The Bordeaux - Crossover Help Needed - DIY Gurus please chime in

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  • Efalegalo
    Senior Member
    • Jan 2007
    • 138

    The Bordeaux - Crossover Help Needed - DIY Gurus please chime in

    Hi All,

    I just recently completed my build of The Bordeaux and needed help with crossover issue I'm having.

    See attached picture of the frequency response. I have a massive dip in the 1.25Khz - 4.0Khz range.

    I've checked the crossover a 100x.

    I'm hoping other builders can take measurements of their Bordeaux build and post here.

    I'm trying to figure out whether something in the manufacturing of the drivers may have changed since Curt first designed the crossover for the Bordeaux vs the drivers included in the kit today.

    I built my enclosure 95% like the plans. The only thing I changed was including additional bracing in the mid-section of the bass cabinet (which was otherwise empty of any bracing).

    What information can I post here to help diagnose the issues I'm having.
    Attached Files
  • Jim Holtz
    Ultra Senior Member
    • Mar 2005
    • 3223

    #2
    Have you contacted Curt?

    You need to provide details.

    Is the speaker complete or are you just measuring the top cabinet? Postioning of the cabinet in relation to the walls when measuring? Is the top cabinet foam installed per spec?

    What measurement setup are you using?

    HTH

    Jim

    Comment

    • Matt M
      Member
      • Jul 2014
      • 86

      #3
      If one takes the scaling of the Bordeaux's measurements into account, this doesn't look too bad. This is an overlay of Efalgalo's measurements and the ones from the "Time for a Bordeaux"-Thread:
      Click image for larger version

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      Again, doesn't look too bad. It could be the case that the parallel cap in the midrange crossover isn't connected. That might increase the dip. But besides, the differences could also be attributed to:
      • Difference in measuring distance
      • Difference in measuring height
      • Differences in microphone calibration
      • Driver variations
      • Differences in diffraction behavior between both builds.


      Do both your speakers measure the same?
      -Matt

      Comment

      • Efalegalo
        Senior Member
        • Jan 2007
        • 138

        #4
        Jim,

        Yes - I've been working with Curt to try and resolve this and feel bad taking too much of his time.

        Yes - The bass cabinet is complete. Though, at the moment, I'm not much concerned with the bottem end. These are in-room gated measurements. I don't have a large enough room to take accurate sub-300hz measurements.

        Yes - Speaker was positioned as you suggested.

        Comment

        • Efalegalo
          Senior Member
          • Jan 2007
          • 138

          #5
          Thanks for posting.

          Matt,

          Thanks for posting. Very interesting post. I hadn't noticed the scaling on the measured response included in the original design thread; however, I still see some weakness in the 2Khz - 4Khz range when compared to Curt's measurements.

          It almost seems like the high-pass of the tweeter is set at too high of a frequency?

          In regards to your comments on:

          - Difference in measuring distance
          - I did take measurements at couple varing distanced (e.g., 0.5m, 1.0m, and 1.5m) and it does not seem to fill that response

          - Difference in measuring height
          - I took measurements on tweeter axix, between tweeter and midwoofer, and at midwoofer. As expected, the response in the subject region is impact, but certainly no where close to filling in that null. I'll try and post those measurements later.

          - Differences in microphone calibration
          - This was also my concern. Hence, I repeated the measurments using two setups: Setup 1: CrossSpectrum Lab Calibrated Mic + ARTA + Focusrite 2i2, Setup 2: MiniDSP Umik-1 + Room EQ Wizard + Focusrite.
          - The measurements were near identical.
          - As a reference, I've included measurement comparison between the measurement setups discussed above when I measured my Philharmonica Audio - Affordable Accuracy Monitors. Ignore response below 300hz.

          - Driver variations
          - THIS CONCERNS ME THE MOST. Thus, I'm hoping other Bordeaux builders can post measurements

          - Differences in diffraction behavior between both builds.
          - With the exception of adding additional bracing in the bass cabinet, I built the enclosures 100% to spec. Same baffle width. Same baffle height. Same baffle edge round over.


          Lastly - YES - the two cabinets (left and right) measure exactly the same.
          Attached Files

          Comment

          • Jim Holtz
            Ultra Senior Member
            • Mar 2005
            • 3223

            #6
            I'm sure Curt has probably covered this with you but an open back mid speaker needs to me measured differently than the Philharmonics which is closed back.

            The frequency response in the mids is a combination of the front sound wave and the reflected rear wave. The top cabinet must be connected to the bass cabinet since they contribute to the midrange. Altering the foam in the mid tunnel will change frequency response.

            What distance did Curt suggest you measure from? The measuring distance needs to be great enough so that the front/rear sound waves can blend for an accurate measurement.

            Driver variation: if both Accuton drivers measure the same, it's probably not the drivers.

            What kind of room are you measuring in? Size, wall treatments if any and floor treatment? Is it carpeted?

            How far from the back of the top cabinet to the wall behind and how far from the side walls to the speaker? They should not have anything close to them.

            BTW, your measurement of the Bordeaux looks more like a sim with each individual driver response shown with crossover points than a typical FR measurement. Can you show us a normal one for the speaker with normal smoothing?

            Thanks!

            Jim

            Comment

            • Matt M
              Member
              • Jul 2014
              • 86

              #7
              Ok, good job - that covers a lot. Your crossover is most likely fine. Your mics are good. Which one did you use? I can see that the red one has minor depletion around 2.5..3.5 kHz. If that one was used, this might add to the result.

              Could you please post a picture of the baffle (mid-tweeter-section)?
              How is the interior chamfering for the midrange driver supposed to look like? How does yours look like?

              -Matt

              P.S.: there appears to be no backside chamfer for the Bordeaux. Just a a continuous tube, right? In that case: forget about the chamfer.
              P.P.S.: How about driver burn-in? Especially regarding the Accuton driver?

              Comment

              • Efalegalo
                Senior Member
                • Jan 2007
                • 138

                #8
                Jim - maybe I'll take the measurements again with longer gate times and see how that impacts the response.

                Curt mentioned the design axis was between the tweeter and mid - 10 degrees off on the Horizontal axis. I will try and post multiple measurements this evening.

                Matt,

                I've attached a couple pics during the construction process. Its hard to see in the picture, but the tube matches perfectly with the rear chamfered baffle on the mid-driver.

                Also - Jim had mentioned making sure the tweeter is perfectly flushed with the baffle - I made sure of this.
                Last edited by Efalegalo; 29 March 2019, 10:47 Friday.

                Comment

                • Efalegalo
                  Senior Member
                  • Jan 2007
                  • 138

                  #9
                  More Measurements

                  All,

                  Attached are multiple measurements.

                  These measurements were taken on the design axis (-10 Horizontal offset - Mic b/w tweeter and mid-level).

                  All previously used crossover parts have now been replaced with new premium crossover parts (e.g., Clarity Caps ESA, Zisters, 16 gauge inductors, etc.).

                  The mid-woofer response ever so slightly increased - possibly as a result of a lower resistance value of the series inductor?

                  As you can see - the dip is STILL present.

                  One of the measurements were taken with longer gate time - in hopes that rear-wave from the mid/tweeter would sum with the direct wave - again the dip still persists.

                  Does it make sense that the crossover point between the mid-woofer and tweeter is nearly 10db(?!?!) lower? Does it need to be -3db to -6db for it to sum flat (depending on whether it's BW/LR/etc.)?


                  Jim,

                  Any chance Curt can post raw individual driver measurements and then with crossover components in place. Not full range - but for each individual component? That way I may be able to troubleshoot which component's response is not being attenuated correctly.
                  Attached Files
                  Last edited by Efalegalo; 25 March 2019, 23:37 Monday.

                  Comment

                  • Jim Holtz
                    Ultra Senior Member
                    • Mar 2005
                    • 3223

                    #10
                    Curt is tied up with his day job right now and is going to be unavailable for a while. I'd suggest you work with Curt when he's available and get his thoughts.

                    Sorry I can't be of anymore help.

                    Jim

                    Comment

                    • Matt M
                      Member
                      • Jul 2014
                      • 86

                      #11
                      Hi,

                      the dip is about 6.4 dB difference. With the purple curve (different mic position) it is 5.4 dB. And your measurements are only 2.5 dB from the reference. But still enough to be uncomfortable. Your measurements are great, but without more reference data how it is supposed to look like we will have to wait for Curt's input.

                      For now, I would try to give the drivers some serious some-burn in. They might need it. Let it run for 24h. See the next day if the result changes. It is best not to move the mic between measurements if that is possible. Also, do 30min of burn-in before the first measurement so that everything is warmed up.

                      Did you have a chance yet to listen to some music with your speakers? What was your impression?

                      - Matt

                      Comment

                      • ergo
                        Senior Member
                        • Mar 2005
                        • 675

                        #12
                        In this design mid and tweeter are wired in opposite polarity. Have you carefully checked that you have wired them correct way? With regular dome tweeters and cone drivers I've been using the small 1.5V battery to check that the terminal polarity is correct (cone/dome moved out). With ribbon you can't do that, but have you tried to reverse the polarity of TW to check how the response looks then? The original thread does not plot a reverse polarity reference curve unfortunately, but still worth a try imho.

                        Comment

                        • Efalegalo
                          Senior Member
                          • Jan 2007
                          • 138

                          #13
                          Here is something interesting.

                          I traced manufacturer measurements and then simulated the crossover in Xsim.

                          For Mid-Woofer: Simulation based on traced manufacturer measurements (processed for diffraction impact) match actual measured response reasonably well.

                          For Tweeter: Manufacturer measurements were only available down to 1.0Khz. I added a "tail" below that. However, focusing solely on the frequency spectrum in question (i.e. 1.5khz - 4.0khz), my tweeter seems to be rolling off at a steeper slope. Maybe I need to revisit my tweeter crossover section one more time to verify connections?

                          - Black = Measured Response
                          - Red = Traced Respose + Processed for baffle diffraction impact

                          I've included a comparative measurement between raw response of the Accuton mid (without crossover) vs traced from the manufacturer (but processed for baffle impact). I did not provide the same raw measurements for the Tweeter because I'm too scared to damange the ribbon tweeter without a protection cap (which I know will impact response somewhat).
                          Attached Files
                          Last edited by Efalegalo; 27 March 2019, 13:42 Wednesday.

                          Comment

                          • Efalegalo
                            Senior Member
                            • Jan 2007
                            • 138

                            #14
                            Herein lies the problem (?)

                            After my last post, I went and measured the tweeter's raw response.

                            Turn out - the tweeter naturally rolls off starting 5,000Hz.

                            This is DEFINITELY NOT consistent with manufacturer findings - which claims flat response down to 1,000Hz. Mabe Something in the manufacturing process changed?

                            See below picture for tweeter's response on the baffle. Disregard SPL magnitude. Use the SPL scale for relative frequency balance.

                            This is why I'm hoping other builders can measure their speakers and share their results.
                            Attached Files
                            Last edited by Efalegalo; 27 March 2019, 22:02 Wednesday.

                            Comment

                            • Juhis
                              Junior Member
                              • Dec 2018
                              • 21

                              #15
                              Your frequency response looks like what the Hadwood Acoustics tweeter has on it's white paper.
                              I'm building Bordeaux using this one which were somewhere told to be the same as Arum Cantus AST2560.
                              Buy Harwood Acoustics AM 25 Air Motion Transformer online at hifisound.de » 229 € ✓ Your online hifi specialist retailer for Tweeter


                              Click image for larger version

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                              Comment

                              • Efalegalo
                                Senior Member
                                • Jan 2007
                                • 138

                                #16
                                Juhis,

                                Thanks for posting. That seems consistent with my findings. See my measurements comparate to Harwood Acoustics AM 25 AIR. Almost spot on.

                                I'm a little bummed and annoyed by Aurum Cantus with the data included in their spec sheet.

                                The Bordeaux was the most expensive speaker kit I had purchased to date. I really like the styling and it seemed like it had potential. I even went over board with all "high-end" crossover components.

                                However, a wide 5db dip in the frequency response is definitely audible.

                                Not sure what to do next?!?! Thoughts anyone?
                                Attached Files

                                Comment

                                • Matt M
                                  Member
                                  • Jul 2014
                                  • 86

                                  #17
                                  I agree that a 5 dB depression is not desireable. But your speakers are only 2.5 dB off from the reference measurement IMO. I think that will be manageable.

                                  Again, how much burn-in time do your drivers have at this point?

                                  If the deviation persists after burn-in, best thing IMO would be to change the tweeter network. Increase the 8.2uF by adding another 2.2..3.9uF. The parallel coil should be a bit lower, but you can start with just adding a cap. That will raise the level in the affected region. I am not certain what would be the best approach to do this more systematically. Depends on what reference measurements will be available.

                                  Comment

                                  • Jim Holtz
                                    Ultra Senior Member
                                    • Mar 2005
                                    • 3223

                                    #18
                                    Originally posted by Efalegalo
                                    Juhis,

                                    Thanks for posting. That seems consistent with my findings. See my measurements comparate to Harwood Acoustics AM 25 AIR. Almost spot on.

                                    I'm a little bummed and annoyed by Aurum Cantus with the data included in their spec sheet.

                                    The Bordeaux was the most expensive speaker kit I had purchased to date. I really like the styling and it seemed like it had potential. I even went over board with all "high-end" crossover components.

                                    However, a wide 5db dip in the frequency response is definitely audible.

                                    Not sure what to do next?!?! Thoughts anyone?
                                    1st of all, reread post #2 & #3 and take few deep breaths. You need to wait for Curt. He'll be available this weekend or 1st of next week.

                                    Matt is giving you good information.

                                    Here are some thoughts. This is an open back mid speaker and it simply won't measure the same as a closed back speaker at typical distances.The back wave and the front wave have to blend to get accurate measurements of frequency response. That means you need to measure further back than a conventional speaker

                                    Curt can verify this but I think I remember him saying he flattened the AMT response about 5 db to compensate for roll off. I'm curious if you're measuring with a cap on the AMT? That would affect rolloff on the bottom.

                                    Finally, have you listened to music through these setup as they're designed?

                                    Now, I'm going to crawl on my soap box for a minute. I've listened to very few speakers that sounded natural to me that have been voiced for flat response. Flat is where a speaker designer starts but usually doesn't end there. That's the black art of voicing which will vary with the drivers used and is the critical last step in creating a speaker that makes you go WOW! That is all my opinion of course.

                                    Curt's the measurements guy so wait for him.

                                    Jim

                                    Comment

                                    • Efalegalo
                                      Senior Member
                                      • Jan 2007
                                      • 138

                                      #19
                                      Originally posted by Matt M
                                      I agree that a 5 dB depression is not desireable. But your speakers are only 2.5 dB off from the reference measurement IMO. I think that will be manageable.

                                      Again, how much burn-in time do your drivers have at this point?

                                      If the deviation persists after burn-in, best thing IMO would be to change the tweeter network. Increase the 8.2uF by adding another 2.2..3.9uF. The parallel coil should be a bit lower, but you can start with just adding a cap. That will raise the level in the affected region. I am not certain what would be the best approach to do this more systematically. Depends on what reference measurements will be available.
                                      Thanks Matt -

                                      I going to let the speakers play at moderate levels for the next 24s and try and repeat measurements.

                                      Comment

                                      • Efalegalo
                                        Senior Member
                                        • Jan 2007
                                        • 138

                                        #20
                                        Originally posted by Jim Holtz
                                        1st of all, reread post #2 & #3 and take few deep breaths. You need to wait for Curt. He'll be available this weekend or 1st of next week.

                                        Matt is giving you good information.

                                        Here are some thoughts. This is an open back mid speaker and it simply won't measure the same as a closed back speaker at typical distances.The back wave and the front wave have to blend to get accurate measurements of frequency response. That means you need to measure further back than a conventional speaker

                                        Curt can verify this but I think I remember him saying he flattened the AMT response about 5 db to compensate for roll off. I'm curious if you're measuring with a cap on the AMT? That would affect rolloff on the bottom.

                                        Finally, have you listened to music through these setup as they're designed?

                                        Now, I'm going to crawl on my soap box for a minute. I've listened to very few speakers that sounded natural to me that have been voiced for flat response. Flat is where a speaker designer starts but usually doesn't end there. That's the black art of voicing which will vary with the drivers used and is the critical last step in creating a speaker that makes you go WOW! That is all my opinion of course.

                                        Curt's the measurements guy so wait for him.

                                        Jim

                                        Thanks, Jim. Yes - I'll wait until Curt can chime in. Any idea when all the typical detailed information regarding the Bordeaux will be uploaded to the Speaker Design Works website? It would make troubleshooting a whole hell of a lot easier.

                                        Again - I think the original design is wonderful. My concern is only that something in the manufacturing of the tweeter has changed that results in different response than advertised by the manufacturer. Maybe earlier units, like the one used in the original desgin, didn't suffer from the early roll off.

                                        Also - I tried several measurements distances (0.5m, 1.0m, 1.5m, and 2.0m) - and it made no difference in the subject region.

                                        Nonetheless - I'm hoping Curt will chime in.

                                        Comment

                                        • Efalegalo
                                          Senior Member
                                          • Jan 2007
                                          • 138

                                          #21
                                          Update

                                          Spent the weekend break-in and listening to the speakers.

                                          I really like the bass from the two 8" drivers. I think even the Accuton has a very unique sound - really nice midrange. I'm not sure if that is the result of the driver being excellent, or me hearing an open back speaker for the first time.

                                          The voicing of the speaker is certainly different than what I'm used to.

                                          Over the years, I have come to prefer speakers that have a slight downward tilt in their power response. My Bordeaux's currently have a slight upward response (with the excepting on the 1.5Khz - 5.0Khz dip)

                                          Took some off-axis measurements of the top cabinet (0 to 60 degrees, increments of 10 degrees), based on the crossover as originally designed. I played around with increasing the series capacitor value on the tweeter, but it doesn't make a change because the tweeter is naturally rolling off at 5Khz.

                                          I tried modifying the crossover by allowing the mid to play to a higher frequency (3.25Khz). This helped with on axis response, but the high crossover results in a poor off-axis response (maybe becaue (i) the mid starts to beam, and (ii) the center to center spacing of the tweeter and mid exceeds the wavelenght of the crossover frequency). 0 - 60 degrees off-axis response also included below.

                                          (EDIT: The measurements included below DO NOT include the response of the bass cabinet. The bass/mid blend perfectly the reponse is near flat from 30hz - 1.2khz).


                                          Still debating what options I want to pursue going forward.

                                          Possible options I'm considering are:

                                          1) Try to find a replacement tweeter that can play comfortably down to at least 2,000Khz and Keep the Accuton Mid.
                                          - This option is going to be difficult because I don't think I can find another tweeter than can fit the cut-out of the Aurum Cantus
                                          - I can make another tweeter work if it has a slightly larger mounting plate.
                                          - Are there dome tweeters out there that have a square mounting plate?

                                          2) Sell the parts from the top cabinet, and build something with the current SB Acoustics drivers I have on hand

                                          3) Sell the whole Bordeaux speaker as is.
                                          Attached Files
                                          Last edited by Efalegalo; 31 March 2019, 22:20 Sunday.

                                          Comment

                                          • Zvu
                                            Senior Member
                                            • Oct 2013
                                            • 434

                                            #22
                                            Now that measures really dreadfull.

                                            If you are good with crossover designing software, i'd change the tweeter and start all over.
                                            Tesla; George Carlin;

                                            Comment

                                            • Jim Holtz
                                              Ultra Senior Member
                                              • Mar 2005
                                              • 3223

                                              #23
                                              Ok guys, this thread is going the downhill without any input from Curt, the designer. He'll answer and help but until he can get settled in from his business trip. Here's the curves measurement of my Bordeaux.

                                              Click image for larger version

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                                              The C158 has a strong breakup at 4K so the 2.5k crossover to the AST2560 is just right. No one crosses this driver higher than 2.8K.

                                              I'll repeat what I'd posted earlier that Curt flattened the AST2560 response which if you examine the response closely, its flat from about 2K on up with his response shaping.

                                              Click image for larger version

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                                              Obviously, your measurements don't match Curt's. Again, I suggest, wait for Curt. He's a master crossover designer and has been at this for many decades.

                                              HTH

                                              Jim

                                              Comment

                                              • Efalegalo
                                                Senior Member
                                                • Jan 2007
                                                • 138

                                                #24
                                                Jim,

                                                Apologies - I do not mean to criticize. Curt is in fact a master at crossover design. I did lot of rearch before settling on the Bordeaux kit - and I settled on that kit solely based on the reputation you and Curt have. Each one of your collaborations have been a massive hit in the DIY community.

                                                In fact, when I was working with traced manufacturer measurements, Curt's crossover works perfectly.

                                                The ONLY thing I'm trying to point out in this thread is that Tweeters that came with my kit DO NOT measure as provided by the Aurum Cantus (but, instead, measure exactly like Harwood Acoustics AM25). Maybe this happened as a result of a change is the manufacturing process. As you can see, my measurements don't come anywhere close to the measurements Curt achieved.The measurements you included in your post above show near perfectly flat (ever so slightly downward tilt) from 2Khz - 20Khz with the crossover in place. My measurements show that with the crossover in place, the response at 2Khz is nearly 13.5db lower compared to Curt's measurements!!!! Thats a massive discrepancy. Maybe some will aruge that its because of different measurement setup, measurement mic, etc. etc. - and while that may be true - I think the diferent setups couldn't result in more than 1db or 2db difference - but not 13.5db!

                                                So - I need to figure out what I need to do next.
                                                Last edited by Efalegalo; 01 April 2019, 10:50 Monday.

                                                Comment

                                                • Matt M
                                                  Member
                                                  • Jul 2014
                                                  • 86

                                                  #25
                                                  No, it's still 6.5 dB. Take a look at the scale!

                                                  I agree, that this mid driver should not be crossed any higher than it is. You'll have to redesign the tweeter crossover.

                                                  If the tweeter is actually way off from the manufacturer's specifications, you might be eligible for return or replacement. If you purchased this as a kit from madisound, maybe they can help you in some way. As long as you're not on a 14-days time limit for claims, wait for Curt!

                                                  Comment

                                                  • Efalegalo
                                                    Senior Member
                                                    • Jan 2007
                                                    • 138

                                                    #26
                                                    Originally posted by Matt M
                                                    No, it's still 6.5 dB. Take a look at the scale!

                                                    I agree, that this mid driver should not be crossed any higher than it is. You'll have to redesign the tweeter crossover.
                                                    Matt,

                                                    Sorry - when talking about the 13.5db difference, I was talking solely about the tweeter measurements Jim posted, which were inclusive of the crossover, vs my measurements of the tweeter with the crossover in place.

                                                    Please find below two graphs:

                                                    1) My Tweeter w/ Curt's Crossover versus Jim's post of Curt's measurement of the tweeter with his crossover in place.

                                                    2) My Tweeter response with Curt's crossover in place vs Traced Reponse of the Haywood Accoustics AM25 Tweeter (which is aparently the clone of the AST2560) with Crut's crossover


                                                    As you can see, there is a massive difference in the response of my tweeter vs Curt's tweeter

                                                    I also think my tweeter are 100% functional. The two units I have are wihtin +/- 0.25db of one another - and have the same impedance measurements. I just think the published measurements under the "Haywood Accoustics" brand are FAR FAR FAR more consistent with what I've achieved vs the pusblished measurements under the "Aurum Cantus" brand.

                                                    I really don't want to give up the Accuton - I was really surprised by its performance when I was listening to music. I do agree with you that I will likely need to redesign with a new tweeter.
                                                    Attached Files

                                                    Comment

                                                    • Matt M
                                                      Member
                                                      • Jul 2014
                                                      • 86

                                                      #27
                                                      By the first picture I would assume that your tweeter is fine. Given the fact that these are two different drivers measured by two different people the match is outstanding.

                                                      The second picture shows that AM25 and AST2560 are indeed different tweeters, and that you cannot use the traced data of the AM25 sheet to verify your results. It also shows: if your tweeter behaved anything like the AM25 you would have a much larger drop compared to the reference. Not 2.5 dB, but 12 dB.

                                                      Then there is still the surpisingly good match between your measured tweeter performance and the simulation based on the AM25. But this comparison has the biggest margin of error as it is based on traced manufacturer data and ignores diffraction effects. The same goes for the second picture of your previous post if you start comparing to your own measurements. So, these comparisons are the least reliable ones and if the other data indicates that you're fine, you probably are. If these comparisons were valid, there would be now way to explain why the other, more reliable comparisons are only off by less than 3 dB.

                                                      Still, there is nothing wrong with redesigning the tweeter crossover if you don't like what you hear.

                                                      Comment

                                                      • Efalegalo
                                                        Senior Member
                                                        • Jan 2007
                                                        • 138

                                                        #28
                                                        Originally posted by Matt M
                                                        Then there is still the surpisingly good match between your measured tweeter performance and the simulation based on the AM25. But this comparison has the biggest margin of error as it is based on traced manufacturer data and ignores diffraction effects.
                                                        Thanks for the post, Matt.

                                                        Considering (i) the frequency in question (2Kz - 5Khz), (ii) the tweeter's location on the baffle, (iii) baffle width of 11.5", and (iv) 3/4" round-over on the verticle edge -----> diffraction effects should be minimum (+1/-1db).

                                                        Just to confirm my assumptions above, I simulated diffraction effect and added it to the Haywood AM25 published response. My measured response still matches the simulated response reasonably well.

                                                        Unfortunately, I will likely end up replacing the tweeters. Just hard to choose which one.

                                                        I'm still digging the Accuton.
                                                        Attached Files

                                                        Comment

                                                        • Efalegalo
                                                          Senior Member
                                                          • Jan 2007
                                                          • 138

                                                          #29
                                                          Update:

                                                          I've decided to abandon the Bordeaux build. I had purchased a brand new set of the AST2560s and they measure EXACTLY the same as the older pair. I'll be listing my pair for sale and returning the ones newly purchased.

                                                          Since I'm not very good at woodworking, it took me forever to build the top cabinet - so maybe I won't completely abandon it. Instead, I think I might just try and retrofit another tweeter. I also don't feel like selling off the Accuton. If I can get a fair price for it, I may, but I was really digging the Accuton in the open back configuration.

                                                          I want to sincerely thank Curt for trying to help me troubleshoot the issue.

                                                          If I manage to successfully retrofit another tweeter, then I'll come back to this thread to provide an update.

                                                          Cheers.

                                                          Comment

                                                          • Jim Holtz
                                                            Ultra Senior Member
                                                            • Mar 2005
                                                            • 3223

                                                            #30
                                                            Originally posted by Efalegalo
                                                            Update:

                                                            I had purchased a brand new set of the AST2560s and they measure EXACTLY the same as the older pair. I'll be listing my pair for sale and returning the ones newly purchased.

                                                            Cheers.
                                                            I've been talking to Curt and we're as disappointed as you that there seems to be a change in the AST2560 response. Curt is following up to try and determine what and when this happened. Where did you purchase the original parts and where did you buy the replacements? I'm not sure what part of the world you live in.

                                                            Thanks!

                                                            Jim

                                                            Comment

                                                            • Juhis
                                                              Junior Member
                                                              • Dec 2018
                                                              • 21

                                                              #31
                                                              Could there be any crossover tweak that would help? I see that there are couple of builds where Harwood AM25 is used and the response is quite flat. Of course the Mid is not the Accuton but anyway..
                                                              ~2,2kHz used for crossing the mid and tweeter on these builds..
                                                              I'm not familiar on calculating the crossovers so I just wonder if we could just drop the level of tweeter to get response curve more flat as is seen on these builds below.
                                                              This is just my last hope since I got the same parts and almost finalized my build.. I need some help too to avoid trashing pair of ~500$ tweeters..

                                                              Buy Harwood Monitor 13 AM - speaker kit (without cabinet) online at hifisound.de » 399 € ✓ Your online hifi specialist retailer for DIY - Products

                                                              Buy Harwood Acoustics 23 AM - speaker kit (without cabinet) online at hifisound.de » 549 € ✓ Your online hifi specialist retailer for Floorstand

                                                              Comment

                                                              • Matt M
                                                                Member
                                                                • Jul 2014
                                                                • 86

                                                                #32
                                                                I tried to verify Efalegalo's simulations that were based on traced data. That is what I have got and it basically verifies what he has done:
                                                                Click image for larger version

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                                                                As I said, I was expecting a bigger difference judging from differences in unfiltered response. But my assumption turned out to be wrong. I have to apologize!

                                                                edit:
                                                                Yet, based on traced data, it is possible to create a crossover for the AM25 that will result in the same behavior as the original AST2560 should have. Distortion and power handling might become a problem, however, as the new filter needs a lower cut-off point and shallower slope. Hard to tell.

                                                                -Matt

                                                                Comment

                                                                • Jim Holtz
                                                                  Ultra Senior Member
                                                                  • Mar 2005
                                                                  • 3223

                                                                  #33
                                                                  Guys, Curt is in touch with Aurum Cantus and waiting on their response. I'd really like to know where the AST2560's were purchased and when so we can see if this is a single run issue or a change in production that was unannounced.

                                                                  Yes, the crossover can be changed but It'll take a complete redesign of the crossover to do it correctly which is not a small task. My Bordeaux can be used for development but we're several hours apart and other commitments need to be met plus getting our hands on an AST2560 that measures differently than the original in my pair.

                                                                  More to come....

                                                                  Jim

                                                                  Comment

                                                                  • Efalegalo
                                                                    Senior Member
                                                                    • Jan 2007
                                                                    • 138

                                                                    #34
                                                                    Jim,

                                                                    I had originally purchased the Aurum Cantus in September of 2017 from Parts Express. I just purchased another set Parts Express last week and they matched exactly to the prior set I had purchased. I haven't tried purchasing from Meniscus Audio, but I would hate to purchase and immediately return an item to a smaller company like that. Not that I care less about Parts Express, but I wanted to make sure there was nothing wrong with the original tweeters I had purchased from them.

                                                                    I will say that there must have been a time were the AST2560 was produced which had flat response down to 2.0Khz. I found an old thread (back from 2011) on Parts Express where Pete Schumacher measured the AST2560 and found that it performed really well and nearly ruler falt down the 2.0Khz, which seems to be consistent with Curt's measurements. Thus, I honestly believe there is nothing wrong with the your's and Curt's design; its just that the tweeter produced today doesn't matchs the reponse of the tweeter in your build.


                                                                    Juhis,

                                                                    I'm of the opinion that a well functioning crossover tweak may be difficult to achieve with this combo. One can cross the Accuton a little higher, but then you have to worry about appropriately supressing the cone break Jim mentioned earlier and well as the poor off-axis respone from taking the midrange that high. Also, I remeber reading some place that its best to keep the center-to-center distance between components less than the wavelength at the crossover frequecy. The spacing between the tweeter and mid on the Bordeaux is 146.8mm --> which corresponds to 2,343Hz --> and based on the measured response of the AST2560, is hard to get it to cross that low. BUT - I'm not a crossover guy. So take these comments with a grain of salt. EDIT: Took a stab at crossover adjustment. This is based on simulated measurements and don't know exactly how they will fair. BECAREFUL of the low impedance at 2.2Khz - seems like it drops to 2.5ohms!.

                                                                    Hope fully crossover gurus can chime in.

                                                                    Thanks
                                                                    Attached Files
                                                                    Last edited by Efalegalo; 08 April 2019, 22:45 Monday.

                                                                    Comment

                                                                    • Efalegalo
                                                                      Senior Member
                                                                      • Jan 2007
                                                                      • 138

                                                                      #35
                                                                      Here are some actual measurements from the crossover above.
                                                                      Attached Files

                                                                      Comment

                                                                      • Jim Holtz
                                                                        Ultra Senior Member
                                                                        • Mar 2005
                                                                        • 3223

                                                                        #36
                                                                        Thanks Dhar. That helps...

                                                                        I can't comment on the crossover mods you've applied. That's Curt's area of expertise.

                                                                        Jim

                                                                        Comment

                                                                        • Curt C
                                                                          Senior Member
                                                                          • Feb 2005
                                                                          • 791

                                                                          #37
                                                                          Bordeaux builders and potential Bordeaux builders:

                                                                          I’m late to the discussion as usual, but that doesn’t mean I haven’t been working behind the scenes trying to resolve this issue.
                                                                          Efalegalo, I appreciate your persistence and patience while you and I worked through the potential possibilities. It now appears at some point Aurum Cantus adversely changed their design. However long ago this was is up for speculation, but for whatever reason, their published specifications and the current drivers now differ significantly.

                                                                          To all who are presently building the Bordeaux: Please accept my humble apology. Jim and I had no idea that the Aurum Cantus AMT’s we used would be any different than the current production. I have emailed Aurum Cantus twice in the last two weeks and have been disappointed with their lack of response.

                                                                          That said, Jim and I will investigate revising the crossover to utilize the ‘new’ AST2560. I won’t know for sure until I voice it, but it certainly appears doable on paper. Due to logistical issues and previous commitments, Jim and I won’t be able to address this issue in the very near term, but as soon as our schedules mesh, we will relocate the Bordeaux to my location and start the measurement/design/voicing process in motion.

                                                                          We realize for some that this will not happen as quickly as we would like. Jim and I again apologize for this unintended frustration and disappointment. We will endeavor to correct the issue as soon as possible, and bring the Bordeaux back to their former glory.

                                                                          Curt
                                                                          Curt's Speaker Design Works

                                                                          Comment

                                                                          • Efalegalo
                                                                            Senior Member
                                                                            • Jan 2007
                                                                            • 138

                                                                            #38
                                                                            Curt,

                                                                            Thanks for posting. If it's of any help, I'm happy to take measurements and send them to you. I also want to let you know that factory measurement provided by Haywood are pretty spot on to what I actually measured. The only thing I'm nervous about is measuring the AMT2560 without a cap in place. If you think it would be sufficient for your purposes if I measure with say a 50uf cap in place at low volume, I'm happy to do that. If you have any other suggestions, I'm all ears.

                                                                            I'm attempted distortion measurements of the AST2560. These begin at 1khz - 20khz. The volume was set so the fundamental response was 90db @ 1m at 2khz (and due to the rising response of the tweeter, nearly 100db at 5khz and above). The mic was 10cm from the tweeter. Hopefully, this gives you some indication on how low the tweeter can be crossed safely.
                                                                            Attached Files

                                                                            Comment

                                                                            • jacket_fan
                                                                              Member
                                                                              • Oct 2006
                                                                              • 83

                                                                              #39
                                                                              Very interesting thread from a previous Bordeaux builder. I do not have the capability to measure my speakers.

                                                                              What hardware/software is required to do these measurements?
                                                                              Mark

                                                                              Comment

                                                                              • Dave Bullet
                                                                                Senior Member
                                                                                • Jul 2007
                                                                                • 474

                                                                                #40
                                                                                Originally posted by jacket_fan
                                                                                Very interesting thread from a previous Bordeaux builder. I do not have the capability to measure my speakers.

                                                                                What hardware/software is required to do these measurements?
                                                                                Dayton omnimic and Room EQ wizard will get you started for frequency response and distortion measurements. DATS for impedance measurement (with either USB or better - hardware soundcard). Just need line input and output.

                                                                                Comment

                                                                                • Efalegalo
                                                                                  Senior Member
                                                                                  • Jan 2007
                                                                                  • 138

                                                                                  #41
                                                                                  I spent the evening working on a crossover that may pose a little easier load for the amp. I’ll try and post it in the morning.


                                                                                  Sent from my iPhone using Tapatalk

                                                                                  Comment

                                                                                  • Efalegalo
                                                                                    Senior Member
                                                                                    • Jan 2007
                                                                                    • 138

                                                                                    #42
                                                                                    Another Attempt at Crossover

                                                                                    Here is another attempt. At least the impedance is a little better. The crossover frequency is 2.25Khz. The null is about -23db. The design axis is 0-horizontal, with the mic place just at the bottom of the tweeter frame. I ended up going with 3rd-order electrical on the tweeter (maybe 4th-order acoustical) - just because I'm too nervous about damaging the ribbon. Hopefully this allows enough attenuation below the Fc to protect the tweeter.

                                                                                    I've also compared this new crossover with the old crossover - solely for the top cabinet. Looks like overall system efficiency should be the same.

                                                                                    It has the downward tilt I prefer. I'll take polar measurements this evening with this crossover. I'll also share how simulation compares to actual measurements.
                                                                                    Attached Files
                                                                                    Last edited by Efalegalo; 10 April 2019, 11:50 Wednesday.

                                                                                    Comment

                                                                                    • Zvu
                                                                                      Senior Member
                                                                                      • Oct 2013
                                                                                      • 434

                                                                                      #43
                                                                                      Very good work Efalegalo.
                                                                                      Tesla; George Carlin;

                                                                                      Comment

                                                                                      • Efalegalo
                                                                                        Senior Member
                                                                                        • Jan 2007
                                                                                        • 138

                                                                                        #44
                                                                                        Update

                                                                                        Thanks, Zvu.

                                                                                        Please find below an updated version of the crossover. After listening to the speaker for several hours last evening, I decided I wanted a slightly steeper tilt than the previous version posted. The thing is, I'm new to speakers that have a dipole response. The tweeter projects sound forwards and backward, same goes for the mid. Stuffing behind the drivers help attenuate rear response; however, I didn't want to go overboard with stuffing and ruin the "presence" the rear radiation adds to overall soundstage. The flat response of the prior crossover posted resulted in the speaker sounding a bit bass shy (to me, personally).

                                                                                        Please note the graph below is scaled for 3db steps (so, I'm not being that aggressive with the tilted response). As you can see, it has a pretty linear response. The crossover also allows for one to vary the 7.5ohm (R1) resistor just prior to the tweeter to tailor the top end to one's preference without impacting phase-integration/listening axis (range from 5.1ohm to 9.1ohm, 5.1ohm was too bright for my liking, and 9.1ohm was too soft for my liking, my guess is: most people will find their sweet spot between 6.8ohm and 7.5ohm).

                                                                                        The 1.5mH (L3) inductor in series with the midrange can be the more affordable 20 gauge inductor. The higher resistance of the inductor helps attenuate the response of the mid. If you go with a lower gauge inductor, you may want to consider increasing R3.

                                                                                        I'll take actual measurements next week once additional crossover parts arrive.

                                                                                        Overall:
                                                                                        1) System impedance (above 150hz) stays above 4ohm.
                                                                                        2) Electrical phase is -37degrees at 1.6Khz - but the relative impedance should be benign (i.e. 7ohm) <<<- don't ask me why this matters, because I don't understand this stuff. I just remember reading online that speakers electrical phase should be maintained within +/-45 degrees (maybe even +/-30 degrees), and that a combination of phase in excess of that and low impedance can prove to be a difficult load (fatal?) to an amplifier
                                                                                        3) The crossover frequency is at 2.1khz - this allows for (relatively) smooth power response
                                                                                        4) The 3rd order electrical crossover on the tweeter should hopefully protect it from distorting
                                                                                        5) Design axis remains at Curt's original design axis
                                                                                        6) The slight bump at 5.5khz wasn't audible to me (it's about 1db). If need be, it can possibly be addressed by an LCR circuit in series with the tweeter (maybe replacing C6 with the LCR circuit?). For me, it just wasn't audible and thus didn't warrant the added complexity to the crossover.

                                                                                        If you are a current Bordeaux builder, you might want to try the crossover below while we wait for Jim/Curt to come up with a revised design. The new parts required should be cheap (or at least I encourage you to be cheap). We can all save our money for premium parts for when Curt releases new crossover.
                                                                                        Attached Files
                                                                                        Last edited by Efalegalo; 11 April 2019, 15:38 Thursday.

                                                                                        Comment

                                                                                        • Efalegalo
                                                                                          Senior Member
                                                                                          • Jan 2007
                                                                                          • 138

                                                                                          #45
                                                                                          Some Measurements

                                                                                          Although I do not have exact values for the crossover parts selected in the schematics included in the post above, I did have values that were reasonably close.

                                                                                          I will take additional measurements when crossover parts arrive.

                                                                                          Measurements included below:

                                                                                          1) Measured on-axis response of the speaker (bass cabinet + top cabinet - but gated)
                                                                                          2) Off-axis response of the top cabinet only: 0 degrees horizontal to 60 degrees horizontal
                                                                                          3) Distortion measurements. Volume was set so the measured amplitude at 1 meter was approximately 92db; however, the mic was placed 30cm from the baffle.
                                                                                          4) Off-axis response of the top+bass cabinet, 0 degrees to 60 degrees - this measurements wasn't 100% accurate because my turntable isn't big enough to support such a large cabinet - so there is a chance that the front of the baffle may not have been exactly at the point of rotation.

                                                                                          These measurements should be a reasonable proxy of resulting response from schematics included in post #44 above.
                                                                                          Attached Files

                                                                                          Comment

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