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  • Andrew Pratt
    Moderator Emeritus
    • Aug 2000
    • 16508

    BFD's

    Ok now that a bunch of us have our BFD's I figured nows a good time to start a thread discussing the how's and what's of this device. I've started reading Sonnie's thread and it seems well laid out...now I guess its time to start trying things out...

    So is it best to try and get a flat response first then apply a house curve to it?




  • Uncle Clive
    Former Moderator
    • Jan 2002
    • 919

    #2
    Phew, I was hoping someone would start this tread, funny my wife said to me "So there's ten of you guys who bought this thing, now you-all just sitting there looking at it going...... I don't know"! :sos: :LOL:

    Anyway, Andrew, speaking to a friend of mine just yesturday whom BTW will come to assist me in the setup, suggested the same thing. Because all our rooms and systems are different we'll need to establish our rooms' frequency response, get it as flat as necessary then do the corrections. We will be using a laptop, SPL meter and a measurment tool software for the laptop.




    CLIVE




    HEY!! Why buy movie tickets when you can own a Theater?
    CLIVE




    HEY!! Why buy movie tickets when you can own a Theater?

    Comment

    • Andrew Pratt
      Moderator Emeritus
      • Aug 2000
      • 16508

      #3
      see below.




      Comment

      • Bruce
        Senior Member
        • Aug 2000
        • 156

        #4
        CH,

        Will you also use the laptop to control the BFD through it's MIDI ports with the BFD software?

        BFD software




        Bruce
        ____________________________________________
        Bruce

        Comment

        • rebop
          Junior Member
          • Jun 2002
          • 6

          #5
          That's a great looking pre-EQ curve, Andrew. Wish mine was like that

          There is a ton of info over at The Home Theater Forum. Search for "BFD". I have a relatively new thread there as I went through three sets of subs when I got my BFD trying to get results I knew were possible, but I could not acheive in "my room". I had even taken my subs to friends to check to be sure the sub was performing properly.

          What I learned was:

          1. I have a problem room
          2. One sub works better than two subs "in my room"
          3. One sub was plenty
          4. The Hsu VTF-3 worked better than a pair of SVS's or a pair of Sunfires
          5. A "flat" curve sounds better to me in my room than a house curve with cabin gain.
          6. What you measure is not always what you hear - in my case, I had a dip at 71Hz that I corrected and made every kick drum "bloom". Removing that correction sounded "right". There must not be enough resolution with 1/6th octave tones and a Rat Shack meter

          Try this thread: http://www.hometheaterforum.com/htfo...&highlight=bfd

          Here are my "final" results showing before, after and the filters I used:



          Filter 8 is turned off to get rid of the bloom.

          So, this was the final curves, actually. This shows raw, with filter 8 and without.








          -=Bob=-
          -=Bob=-

          Comment

          • brucek
            HTG Expert
            • Aug 2000
            • 303

            #6
            Andrew,

            Your response looks quite easy to equalize...

            No doubt you already know this but, I think one of the important things to take care of first (after you've hooked the thing up) is to ensure you have your level into the BFD set up properly with the BFD on bypass (push and hold IN/OUT switch until the green LED flashes continuously). Now the red level LEDs are presenting input level.....

            My recommendation is to set the level into an EQ as to not overdrive it at the highest level your likely to listen to a movie with an LFE track. Play a movie like U-571 at a level you would consider the loudest you like, and then adjust the sub out level of the processor to "just" not turn on the red LED.

            To take maximum advantage of the dynamic range provided by the analog to digital converter in the BFD or any ADC for that matter, you need to provide it with a maximum input signal level that takes advantage of the greatest number of bits to represent the resultant voltage samples. I know that's oversimplified, but you know what I mean.

            If the range from your weakest signal to the strongest signal was only half the required maximum input level, you would be robbing yourself of dynamic range and subsequently increasing your signal to noise level. To get the most out of this system you would like the maximum signal sent to the BFD to "just" not turn on the red LED. If the yellow LED comes on in explosions etc, that would be fine.

            Since we are feeding the BFD a variable line level whose maximum is actually set by the volume control of the processor and not a "fixed" line level as from a CD player, careful setting of the sub out level of the processor is necessary. Every user is different. Some people like to listen at reference all the time, some like it lower. Each of these people will have different maximum levels being fed to the BFD. Why rob yourself of dynamic range because you've set your input level using exact AVIA reference levels. You need to use the highest dynamic range device, which would be a DVD and play it as loud as you normally would and when an explosion or loud bass scene occurs, check the LED level on the BFD. Set the processor sub out level to just be turning on the yellow LED once in a while. Now you know that at least when you are playing your system at this high level and you have a worst case DVD playing with its LFE plus redirected bass, that the maximum signal will not overdrive the digital input of the BFD because there's no limiter or AGC here - these are basic devices. You'll also know the softest signals will have the least quantization error possible for the ADC system.

            I think the input level to an ADC that isn't fed a fixed volume line level signal should be an iterative approach. Play around with different source material until you are convinced the level from the processor is proper. After that, the level of your sub that you like is only set with the sub's amplifier and not the processor sub out control......

            I also think it's important to not have your mains or any other speakers turned on except the sub during the set up of your filters. Mains and their interaction with the sub can be dealt with later.
            Personally I think it's a good idea to feed your tones through your processor with the crossover enabled at the frequency you'll be using, with your mains off....

            brucek

            Comment

            • Andrew Pratt
              Moderator Emeritus
              • Aug 2000
              • 16508

              #7
              Thanks guys I'm about to start playing with it so I'll report back how things go...I'm pretty excited to get started...




              Comment

              • Uncle Clive
                Former Moderator
                • Jan 2002
                • 919

                #8
                Originally posted by Bruce
                CH,

                Will you also use the laptop to control the BFD through it's MIDI ports with the BFD software
                Sorry took this long had to work from 10:30a - 6:30p
                Yes we will.




                CLIVE




                HEY!! Why buy movie tickets when you can own a Theater?
                CLIVE




                HEY!! Why buy movie tickets when you can own a Theater?

                Comment

                • Andrew Pratt
                  Moderator Emeritus
                  • Aug 2000
                  • 16508

                  #9
                  Hey this thing isn't that hard to figure out at all..now I just need to play with it a little more and dial her in. I added 7 quick filters and its a little flatter now but still needs some tweaking...that hole at 50 is now half as deep but adding more gain isn't working now so that might be as good as it gets....One interesting thing though is that it doesn't sound nearly as loud as it did before adjustment even though its calibrated back to the same overall level...I guess a house curve is on the agenda to try once I get it flat.

                  One other thing to point out is that the adapters I bought from RS to go from RCA to 1/4's were the stereo kind which do not work at all...I was a little scared for a while that my pre amp didn't have enough gain in its LFE channel to drive the BFD properly but while fiddeling around I pulled the adapter half out and all of a sudden it started working properly which got me thinking...luckily I had a Y adapter for the pro amp and its mono so I used it to convert the stereo adapter into mono and it worked properly so I knew what the problem was...just a heads up to those needing adapters make sure they are mono




                  Comment

                  • Pat
                    Super Senior Member
                    • Aug 2000
                    • 1637

                    #10
                    BruceK,
                    I see you are using a BFD and X-30.
                    I have both of those too...what order do you have them hooked up?
                    Do you go from the pre/pro to BFD to X-30 or pre/pro to X-30 to BFD?




                    Pat's Page
                    Pat's Page

                    Comment

                    • Uncle Clive
                      Former Moderator
                      • Jan 2002
                      • 919

                      #11
                      Brucek, would recievers such as the Onkyo with "LFE limiter" capabilty achieve to same goal as you're describing for the BFD?




                      CLIVE




                      HEY!! Why buy movie tickets when you can own a Theater?
                      CLIVE




                      HEY!! Why buy movie tickets when you can own a Theater?

                      Comment

                      • brucek
                        HTG Expert
                        • Aug 2000
                        • 303

                        #12
                        Pat,

                        Yeah, the X-30 is a great line amp for those that don't have sufficient level to drive a sub from their processors. I see SVS also sells a little line amp for this purpose.

                        It would be best to place the line amp between the BFD and subwoofer power amp. Feeding the line amp from the processor is not a good idea for this application.
                        So, the order would be processor - BFD - X30 - Subwoofer........

                        The BFD is not an amplifier, it's a unity gain device. As I was saying in my post above, the BFD is digital and you're feeding an ADC/DAC chain where you would like to optimize the input level to take advantage of all the bits available. By this I mean to take maximum advantage of the dynamic range provided by the analog to digital converter in the BFD, you need to provide it with a maximum input signal level that takes advantage of the greatest number of bits to represent the resultant voltage samples.

                        This means once you've reached and set this input level, you can't increase the level any more, even if you wanted to. So it's the output analog signal from the BFD that you want to amplify, not the input signal to the BFD, which is easily set to optimum by your processor.

                        The BFD's unity output (or less if filters are applied) can then be amplified to your hearts content with the line amp. If the line amp can create 15dB gain, then it will "all" be available to you, instead of being limited if you placed the line amp before the BFD.

                        It's very convenient with the volume control on the X30 to place it beside or near your processor. Then you don't have to crawl around the rear of your sub to adjust the volume.

                        Uncle Clive,

                        No, the LFE limiter in your processor is not going to protect from turning up the level of the signal too high that feeds the BFD. You're going to have to determine the "sub out" level from your processor by using the red VU LED's on the BFD itself. If you have the level too high, you'll see the RED LED on a lot, indicating too much signal feeding the BFD. Some people run their sub out level "hot" from the processor as a volume control. This practice is what I'm cautioning against.

                        brucek

                        Comment

                        • Pat
                          Super Senior Member
                          • Aug 2000
                          • 1637

                          #13
                          Thanks for the insightful reply BruceK :T
                          That helps me out a ton!




                          Pat's Page
                          Pat's Page

                          Comment

                          • Bruce
                            Senior Member
                            • Aug 2000
                            • 156

                            #14
                            I'm using a Feedback Destroyer 1100P and DSP1100 MIDI software with my Hitachi Multimedia Notebook Computer (Windows 95) with a Parallel port Midiman 1x1 Portman/P adapter. All computer MIDI input and output parameters are set to Portman/P-IN and Portman/P-Out selections in the Control panel as well as the DSP1100 MIDI software program settings.

                            I initially set the 1100P's MIDI parameters with the BFD's front panel buttons to the following settings:
                            page1--> 1c
                            page2--> 1o
                            page3--> 4C
                            page4--> 3P
                            page5--> 1S
                            page6--> 1d

                            1) When I initially load the DSP1100 program, everything in the program window is greyed out.

                            2) When I select "New" from the file menu, I get two new program windows titled "Unnamed1-1" and "Unnamed1-2" and everything in the program window now appears active.

                            3) The "Unnamed1-2" program window has all the filter programs and parameter values displayed plus "Load" and "Store" buttons in the upper right corner of the window. All the filters (1-12) are showing values of:
                            PAR, 500Hz, 0dB, and 60/60 Oct.

                            4) The "Unnamed1-1" program window has a straight line graph and the "dB" level meter on the right. In this window, clicking the "I/O" button below the "dB" level meter toggles the "In/Out" button on the front panel of the 1100P in and out of "bypass-blinking" mode. Therefore I know I'm communicating with the 1100P hardware through the MIDI interface.

                            5) If I click in the "Unnamed1-2" window, then select Program 8, and then click the "Load" button, the "In/Out" button on the front of the 1100P flickers and program number "8" shows up on the 1100P's front LED display. Again, I know I'm communicating with the 1100P hardware.

                            6) I can't seem to get any filter values I manually enter in the DSP1100 software to replace any of the filters in the 1100P hardware or to have any effect on the music program material that is playing (when I toggle bypass mode on and off). In other words the "Store" button doesn't seem to do anything.

                            QUESTIONS:

                            1) How do I get any parametric filter changes I make in the DSP1100 MIDI software program's "Unnamed1-2" window to actually load into the 1100P hardware memory for a specified program number?

                            2) How do I load any of the 1100P's current hardware program number filter settings into the DSP1100 MIDI software program?

                            3) How come the "dB' level meter in the DSP1100 MIDI program doesn't show any activity when the "dB" level meter on the 1100P's front panel display is showing lots of activity?


                            So, is the software just used to model the filters and then you have to enter the filter values by hand (button pushing) ?

                            I used the BFD filter graphs to build a mirror image and correct the frequency spikes that appear on the the graphs from ETF5 (my room measurement system).

                            Sure would like to know how to electronically "load" my filter setups from the software into the BFD, anybody experienced with this MIDI interface control of the BFD?




                            Bruce
                            ____________________________________________
                            Bruce

                            Comment

                            • Sonnie Parker
                              • Jan 2002
                              • 2858

                              #15
                              brucek should be able to help you with that software Bruce.

                              Andrew, I started out using a flat response, as flat as I could get it with my dip at 50hz being pretty drastic. I felt like I was missing some punch in watching movies so I tried the house curve. It worked better for me. I have 2 presets, one flat, one house. I always use the house. But, it may be different for your room.

                              I will say that when I boosted the 50hz null to a point where it was almost in line with my house curve I seemed to have too much bass in that area (as far as what it sounded like to me). I eased it back down and even though I have a measured null still there it sounds good to me. Similar to rebop's situation.

                              Looking forward to seeing your new graph.






                              SONNIE

                              Cedar Creek Cinema

                              DVD Collection

                              BFD Comprehensive Setup Guide

                              Comment

                              • Andrew Pratt
                                Moderator Emeritus
                                • Aug 2000
                                • 16508

                                #16
                                One quick question why use present 4 as the preset to build our user defined levels? Why don't we use 1 instead?




                                Comment

                                • rebop
                                  Junior Member
                                  • Jun 2002
                                  • 6

                                  #17
                                  4 and 5 are already preset for ALL filters to be PA (parametric). The other presets have Single Shots, etc set-up by default. You can override that, but it is easiest to start with 4 or 5 and not have to take the extra steps.





                                  -=Bob=-
                                  -=Bob=-

                                  Comment

                                  • brucek
                                    HTG Expert
                                    • Aug 2000
                                    • 303

                                    #18
                                    Hey Bruce,

                                    Sorry, but I've never used the midi feature to load my filters into the BFD. I've only used this design software to play around with the filters to get a visual feel for how my filters look and to also get a feel for what my phase alteration will be given my filters that I use. It's very useful software for this feature alone.

                                    I guess I always found it so easy to enter the filters manually, that I never hooked up a cable to download through the midi - since my computer is in one room and my BFD in the other....

                                    brucek

                                    Comment

                                    • brucek
                                      HTG Expert
                                      • Aug 2000
                                      • 303

                                      #19
                                      Guys,

                                      Something that you should remember to do when you are using a BFD is to add a foot to the value you enter for sub distance in your processor set up.

                                      The 1 msec DSP processing delay in the BFD would account for approximately a foot in distance. If you add a foot to the distance you tell your receiver that your sub is from your ears, then it will advance the sound the 1 msec required for that speaker. This will nicely compensate for the BFD's delay...

                                      brucek

                                      Comment

                                      • brucek
                                        HTG Expert
                                        • Aug 2000
                                        • 303

                                        #20
                                        Guys,

                                        Another thing I found useful if you're using the manual method of taking and charting frequency response, is to burn two CD's.

                                        One with only the sixth octaves from 16Hz up to 160Hz, and a second with every 1Hz increment at least from 10Hz to 80Hz.

                                        The first CD allows you to press play and simply take readings from your RS meter without frigging around with your CD remote. It allows you to do a response very, very quickly, to check after you've altered a filter.

                                        The second CD allows you to narrow in and play around suspect areas of dips and peaks to find out what's going on between the sixth octaves. Sometimes you can make a more educated guess on a center frequency....

                                        I use the tone generator below to make my 5 second tones...

                                        FREE tone generator listed below and save the tones in five second files and burn them on a CDR.

                                        sound, audio, software, download, program, programs, applications, wav, record, play, recorder, player, shareware, tone, instant replay, telephone, hold, messages, action, audio action, development, software development, programming, programmer, freeware


                                        Scroll down to Freeware and click on TONE GENERATOR......

                                        You can also get tones from Sonnies site along with the Excel graphs.


                                        brucek

                                        Comment

                                        • Uncle Clive
                                          Former Moderator
                                          • Jan 2002
                                          • 919

                                          #21
                                          Brucek would you mind emailing me
                                          harrison1884@rogers.com

                                          Thanks!




                                          CLIVE




                                          HEY!! Why buy movie tickets when you can own a Theater?
                                          CLIVE




                                          HEY!! Why buy movie tickets when you can own a Theater?

                                          Comment

                                          • Sonnie Parker
                                            • Jan 2002
                                            • 2858

                                            #22
                                            Originally posted by the brilliant brucek
                                            Guys,

                                            Something that you should remember to do when you are using a BFD is to add a foot to the value you enter for sub distance in your processor set up.

                                            The 1 msec DSP processing delay in the BFD would account for approximately a foot in distance. If you add a foot to the distance you tell your receiver that your sub is from your ears, then it will advance the sound the 1 msec required for that speaker. This will nicely compensate for the BFD's delay...

                                            brucek
                                            Hmmm.... another add to the BFD page.

                                            Thanks!






                                            SONNIE

                                            Cedar Creek Cinema

                                            DVD Collection

                                            BFD Comprehensive Setup Guide

                                            Comment

                                            • Andrew Pratt
                                              Moderator Emeritus
                                              • Aug 2000
                                              • 16508

                                              #23
                                              I started to play with the BFD tonight and I've got an interesting problem. First I must be doing something wrong because the only filter that works is the first filter on 4...no other filter seems to have any effect. While trying to see what was going on I set a -48 on #3 (still in 4) to see what it would do for the peak I have at 71...all that did was lower the overall volume so that tells me its doing some processing but its not applying it to the freq's for some reason? I checked to see that its set to PA which it is so do you guru's have any other things to check? I did try swapping L and R and that doesn't fix it. One thing to note is that number 2 light doesn't come on on Right even though I do everything the same way as the rest? #2 works fine on R though it still doesn't effect the freq's. This doesn't seem to be that hard but I'm obviously missing something...and if it didn't work on #1 (of 4) I'd say either its defective or I'm doing something wrong..partially working is frustrating




                                              Comment

                                              • Sonnie Parker
                                                • Jan 2002
                                                • 2858

                                                #24
                                                Hmmmm Andrew.....sounds like a good one!

                                                I'm a little confused in what you are saying about #3 (still in 4)?

                                                Are you saying filter #3 in preset #4?

                                                If that -48 lowered the overall volume you may have had the bandwidth set really wide. It would lower the overall volume with a wide bandwidth. At -48 it would probably lower the overall volume with a medium bandwidth. Check the bandwidth and start really narrow at 2, 4, or 6 on 71hz and see what happens with just that one filter.

                                                Also make sure you didn't dial in "KHZ" for the frequency instead of "HZ" (little read reading next to the frequency). Just a thought.

                                                Once you input all of your adjustments, etc., are you pressing store twice until you have a red light lit up on the bar? You know once you change anything in a filter the "STORE" light will blink until you press it twice to store the changes you made.

                                                Is the correct engine light lit?

                                                How's your input? When you play something how far up do the output lights go up? Are they getting up to -20 or -10 at least. If not then you may need to up your sub out on your pre/pro. If it's not high enough then you won't get the proper processing.


                                                If you have some filters working and others are not then go back and double check everything for those that are not apparently working (no red LED's lit). If it still doesn't work then I suggest you may indeed have a defective unit....but it would be the first one I've heard of.






                                                SONNIE

                                                Cedar Creek Cinema

                                                DVD Collection

                                                BFD Comprehensive Setup Guide

                                                Comment

                                                • Pat
                                                  Super Senior Member
                                                  • Aug 2000
                                                  • 1637

                                                  #25
                                                  Sonnie,
                                                  I think there is something wrong with your sinewave section.
                                                  Everytime I try to click on it I get this message:
                                                  You don't have permission to access /sinewaves/ on this server
                                                  Thanks for the great BFD setup site...It has been very helpfull!




                                                  Pat's Page
                                                  Pat's Page

                                                  Comment

                                                  • Andrew Pratt
                                                    Moderator Emeritus
                                                    • Aug 2000
                                                    • 16508

                                                    #26
                                                    Doh! Looks like I was in the KHz range ops:

                                                    Where do I hand in my geek badge




                                                    Comment

                                                    • brucek
                                                      HTG Expert
                                                      • Aug 2000
                                                      • 303

                                                      #27
                                                      Sonnie, good catch - I guess you're not spending "all" your time on that new 61" Grasshopper.

                                                      Andrew, there isn't anyone who hasn't fallen for the old "KHz" trick. Welcome to the club...... :roll:

                                                      brucek

                                                      Comment

                                                      • Andrew Pratt
                                                        Moderator Emeritus
                                                        • Aug 2000
                                                        • 16508

                                                        #28
                                                        Alrighty after sorting out the difference between a Hz and a KHz this thing works much better :LOL:

                                                        Here's my before and after from the sweet spot. I could still tweak it a little but to my eye's its not a bad start.




                                                        Now here's where it gets interesting. I plotted the SPL's with the mains engaged as well as the sub. Blue being Sub only and Pink being both mains and sub. I have the mains crossed over at 60 hz on the rotel and they are rated to go down to 45 Hz. So what do I do now?






                                                        Comment

                                                        • Rick Guynn
                                                          Junior Member
                                                          • Mar 2002
                                                          • 9

                                                          #29
                                                          OOps.. misread graph

                                                          Comment

                                                          • Sonnie Parker
                                                            • Jan 2002
                                                            • 2858

                                                            #30
                                                            Andrew, I did the same thing a time or two when I first got mine.

                                                            As brucek says: It's a club thing! lol

                                                            Ken, that's why I got that 61" GH..... so I wouldn't be spending all my time on that 42" Craftsmen. Try 2-3 hours instead of 7-8 hours. Makes a huge difference! I cut everything today and had much more time to work on other things outside. Although it was still hot as a firecracker. :##


                                                            Pat..... what da ya know.... I'm forbidden myself! 8O

                                                            I'll get up with my ISP tomorrow.... they've obviously been playing around with the server. Not a good thing but it happens all along. I can't see my images folder either.

                                                            Thanks for the comp! Glad it has been some help.





                                                            Andrew.......great looking response line on the sub man. You got that baby very smooth.

                                                            On the mains plus sub deal....

                                                            If you can stand to up your sub volume a little then it will over power your mains and you won't have the problem. I don't have that problem with mine but it's probably my room and my main speakers. Plus I use an 80hz crossover point and I like a lot of bass.

                                                            You might try 80 or 90hz as your crossover point instead of 60hz. Seems like I remember reading that most people use a crossover point of double what their mains will go down to. In your case that would be 90hz.....but 80hz should be fine. Your problem area is between 45hz and 80hz so changing the crossover to 80hz should be more than enough to drop the mains down. Isn't that Rotel crossover 12db per octave?

                                                            Another thought is the Rotel's eq. Can you eq just the mains? You could take some out but not sure how much.

                                                            How does it sound? Are you going to try a house curve too?

                                                            Maybe Ken can give us some help on this one.






                                                            SONNIE

                                                            Cedar Creek Cinema

                                                            DVD Collection

                                                            BFD Comprehensive Setup Guide

                                                            Comment

                                                            • brucek
                                                              HTG Expert
                                                              • Aug 2000
                                                              • 303

                                                              #31
                                                              Andrew,

                                                              Good looking sub response Andrew. I do have a few points to make though...

                                                              1. As Sonnie pointed out, with respect to the subs response - the LPF seems rather strange. As you know, most processors have a 2nd order HPF for the 5 main speakers and a 4th order (24dB/octave) for the LPF subwoofer output. If your crossover is at 60Hz, and I look at your graph, it looks like you're only down about 10db an octave past 60Hz. Kinda weird. Actually, the plot looks like it's an 80Hz cross. There's no BFD boost to upset the crossover drop in that range, so I'm confused by that?

                                                              2. Again, I would agree with Sonnie, if your mains reach to 45Hz, then an 80Hz crossover is probably best. This might alleviate some of the small problems you're having in the 45Hz to 95Hz range.

                                                              3. I think you have to establish whether the "slightly rough" (mains + sub) response is being effected by the sub/mains interaction or is this simply the mains response that is at fault here.
                                                              So, it would be a good idea to do a "mains only" response also. Then you will have the information you need to decide. If the "sub only" and "mains only" look good, and the combined response is bad, you'll know you have an interaction problem and can work on that specifically. Phase can help there...
                                                              If the problem is simply a wacky mains response, then that's another issue. The BFD is only there as a sub equalizer, and that's all it can do of course. If your mains have a response problem, then you'd have to try some placement options etc.......

                                                              4. You're taking your readings at a very high SPL level ~100db-110dBSPL. I feel it's a bit better idea to set your volume more in the ~90dB-95dBSPL level to take readings.

                                                              5. From the combined response, I would suspect your level matching between your mains and sub may be off a bit. I wonder if your low end may be sounding a bit flat? If you were to raise the level of the sub with respect to the mains, it would be interesting to see what the response curve looked like.


                                                              brucek

                                                              Comment

                                                              • Andrew Pratt
                                                                Moderator Emeritus
                                                                • Aug 2000
                                                                • 16508

                                                                #32
                                                                Thanks guys I'll run some more plots and see what the mains are doing...I'll also play with the cross over point and see what effect that has. Adjusting phase isn't going to be easy since the Rotel doens't offer phase control and there isn't any phase control on the IB sub. About the best I can do is reverse the banana plugs for the other speakers and see what effect that has.




                                                                Comment

                                                                • Sonnie Parker
                                                                  • Jan 2002
                                                                  • 2858

                                                                  #33
                                                                  Pat,

                                                                  The http://www.snapbug.ws/sinewaves should be working now. At least it's working for me now.






                                                                  SONNIE

                                                                  Cedar Creek Cinema

                                                                  DVD Collection

                                                                  BFD Comprehensive Setup Guide

                                                                  Comment

                                                                  • Pat
                                                                    Super Senior Member
                                                                    • Aug 2000
                                                                    • 1637

                                                                    #34
                                                                    Good work Sonnie :T

                                                                    Downloading now

                                                                    Thanks!




                                                                    Pat's Page
                                                                    Pat's Page

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                                                                    • Andrew Pratt
                                                                      Moderator Emeritus
                                                                      • Aug 2000
                                                                      • 16508

                                                                      #35
                                                                      I was out this eveing but I did check and the crossover was set to 60...I've moved it to 80 but its too late to run any sort of test now...maybe this weekend time permitting.




                                                                      Comment

                                                                      • Wayne A. Pflughaupt
                                                                        Member
                                                                        • Jun 2002
                                                                        • 69

                                                                        #36
                                                                        Let's flip this sucker!

                                                                        Oh sorry, wrong forum! ops:

                                                                        Seriously, Andrew asked me to comment his charts – not sure why, since brucek and Sonnie are doing a great job of driving this thread. The advice they’ve given is spot-on, as always!

                                                                        I took a look at your unequalized curve, Andrew, and the only problem I see is the classic one of using more filters than necessary. Your unequalized response is very good to start with. I mean, ±5dB! The home theater world is full of people would die for response this good after equalizing. I know I would!

                                                                        Notice that there are only three deviations, and they are very symmetrical. As you know, a filter induces symmetrical alterations, so there’s no reason that three filters, four tops, could not get a curve almost identical to the one you’ve achieved with eight filters. More filters = more phase issues, and if I remember, brucek has documented that the BFD brings more phase changes to the table than analog parametrics. This may account for some of the changes you’re seeing when the mains are added.

                                                                        I can give you a link to a post I made on the HTF about filters and bandwidth, if you think that would help (thought I’d check first – some Forums don’t like to see links to other Forums posted).

                                                                        Regarding your combined mains/sub curve, I’m confident the 1/6-octave dip that appeared at 89Hz is phase-induced, probably a function of the crossover and time-domain (signal path) differences between the sub and mains. You can try to address it with a filter – may or may not make a difference.

                                                                        The 45-75Hz plateau is a little strange, but I notice that so far there is no house curve applied. So along the lines of Sonnie’s recommendation, if a curve is dialed in it will probably overwhelm the plateau, if it’s all coming from the mains.

                                                                        Regards,
                                                                        Wayne A. Pflughaupt




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                                                                        • Wayne A. Pflughaupt
                                                                          Member
                                                                          • Jun 2002
                                                                          • 69

                                                                          #37
                                                                          Just adding this because I forgot to check the "e-mail me" box in the one above. ops:

                                                                          Comment

                                                                          • Andrew Pratt
                                                                            Moderator Emeritus
                                                                            • Aug 2000
                                                                            • 16508

                                                                            #38
                                                                            Thanks guys...so how do I go about making a house curve? Do I keep the mains on and adjust for a maximally flat reponse from both the mains and the sub or simply apply a large cut around 400 with a very wide BW and then boost the over all volume?




                                                                            Comment

                                                                            • brucek
                                                                              HTG Expert
                                                                              • Aug 2000
                                                                              • 303

                                                                              #39
                                                                              Hey Wayne,

                                                                              Great to see your learned input at this forum. I agree with your assessment. Andrew already has a pretty darned good response without equalization, but like all HT'ers, he's trying for the perfect sound.

                                                                              I feel his "mains + sub" response curve is exactly the result of the mains being a little high in volume with respect to his sub and we see the natural addition of the two signals until the mains have dropped out of the picture (down about 35Hz) and the sub then overwhelms the situation. I suspect his "mains only" graph will look a lot like the combined graph, but will be dropping at its predetermined 12dB/octave..

                                                                              I don't know if the dip at 89Hz could be crossover phase induced or not. It will be very interesting once Andrew does his "mains only" chart. My feeling is that since he's crossing at 60Hz, and that he has no filters specific, or even near that area, that phase won't be the problem. I suspect his mains are causing it by themselves - but we'll see.
                                                                              I entered Andrews filters into the BFD design software and his curve shows very little phase shifting, mostly due to the fact that he has used small gains and cuts since his original curve is so well behaved.....There is still some phase shift at 89Hz, but it's small...
                                                                              My experience is that the BFD introduces phase shift "similar" to an analog unit. As you know, it's nothing to be concerned about of course, until you approach the crossover area where the mains and sub tend to misbehave when combining their signals in the room.

                                                                              Andrew,

                                                                              If you have the headroom, I would go for the wide filter method from Sonnies site http://www.snapbug.ws/brucekbfdbandwidthinfo.htm
                                                                              But first, I would get the mains/sub interaction problems settled until you were satisfied with your "mains + sub" curve, and then add the house curve last.......Who knows, you may be very happy with the sound using a flat response and not need the house curve. The wide filter method though,is very easy to add and play with and see what your ears enjoy....

                                                                              brucek

                                                                              Comment

                                                                              • Andrew Pratt
                                                                                Moderator Emeritus
                                                                                • Aug 2000
                                                                                • 16508

                                                                                #40
                                                                                I was listening to some tracks from "Brothers in arms" last night and the bass was a little flat sounding...very quick and tight but it didn't have the pressense I'm looking for so I will try the house curve once we get a decent flat response to work from. I've also boosted the crossover point to 80 so we'll see what effect that has on the situation.




                                                                                Comment

                                                                                • Wayne A. Pflughaupt
                                                                                  Member
                                                                                  • Jun 2002
                                                                                  • 69

                                                                                  #41
                                                                                  Hi brucek,

                                                                                  Nice to see you here too!

                                                                                  My feeling is that since he's crossing at 60Hz, and that he has no filters specific, or even near that area, that phase won't be the problem. I suspect his mains are causing it by themselves - but we'll see.
                                                                                  In my admittedly limited experience (okay, limited to my subs/my room!) I found phase interactions a full octave above and below the crossover point! And that was with 24dB/ slopes on both high pass and low pass. I would expect phase problems could show up deeper in both directions if shallower slopes were being used.

                                                                                  However, in my system there were multiple, 1/6-octave phase-induced problems, not only one as in Andrew’s situation. I guess its narrow bandwidth coupled with the fact that it didn’t appear until after the mains were turned on leads me to suspect phase, but again I don’t have enough experience with phase to say conclusively.

                                                                                  Where’s Greg Monfort when we need him?

                                                                                  Regards,
                                                                                  Wayne A. Pflughaupt




                                                                                  My Equipment List

                                                                                  Comment

                                                                                  • Sonnie Parker
                                                                                    • Jan 2002
                                                                                    • 2858

                                                                                    #42
                                                                                    Hmmm! Three weeks later.... vacation and office moving will sure take away from a man's computer time.

                                                                                    Good to see Wayne grace us with his wisdom! Always good reading from both you guys.

                                                                                    Oh btw, good flip Wayne, but no image... :roll: j/k

                                                                                    Andrew, any new graphs....(maybe a house curve graph) just out of curiosity I suppose???






                                                                                    SONNIE

                                                                                    Cedar Creek Cinema

                                                                                    DVD Collection

                                                                                    BFD Comprehensive Setup Guide

                                                                                    Comment

                                                                                    • Andrew Pratt
                                                                                      Moderator Emeritus
                                                                                      • Aug 2000
                                                                                      • 16508

                                                                                      #43
                                                                                      Sonnie I just got back from vacation so I'm going to get back to the BFD shortly...




                                                                                      Comment

                                                                                      • Uncle Clive
                                                                                        Former Moderator
                                                                                        • Jan 2002
                                                                                        • 919

                                                                                        #44
                                                                                        Well, well Andrew, what do you mean your back? The Heineken you ordered is still here waiting for you what do I do now 8x)




                                                                                        CLIVE




                                                                                        HEY!! Why buy movie tickets when you can own a Theater?
                                                                                        CLIVE




                                                                                        HEY!! Why buy movie tickets when you can own a Theater?

                                                                                        Comment

                                                                                        • Sonnie Parker
                                                                                          • Jan 2002
                                                                                          • 2858

                                                                                          #45
                                                                                          I guess you could go ahead and drink it!

                                                                                          I just wish I had time to fool around with my BFD. I suppose I'll have to wait til winter time. Too much outside work to be done for now.

                                                                                          Looking forward to seeing some more graphs Andrew.

                                                                                          I had another fellow e-mail last night about using the BFD. I advised him to post his graphs here in this forum for all to help. Maybe we can be on the lookout for him. (Jonathan Slater)






                                                                                          SONNIE

                                                                                          Cedar Creek Cinema

                                                                                          DVD Collection

                                                                                          BFD Comprehensive Setup Guide

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