Crossover setting in a sub for a 2 channel system

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  • thyname
    Senior Member
    • Jan 2005
    • 358

    Crossover setting in a sub for a 2 channel system

    I recently purchased a REL sub Q150E to go with my 2 channel Rotel/Axiom system (see below my system). I use High-pass level connection in my sub, but I don't seem to set the crossover in the sub right. I initially thought I should set it 40 HZ, since my Axiom speakers are rated Freq Resp +/-3dB (Hz): 37 - 22kHz, to cover lower tones not covered by the mains, but then I moved it up to around 60 and sounded kind of better. What is the general rule of thumb? Any suggestions??

    Axiom M60s powered by Rotel RB-1080/RC-1070 combo
    Rotel RCD-1072 CD player, REL Q150E sub
  • comeup
    Senior Member
    • Jul 2005
    • 356

    #2
    Thyname here is where it gets difficult I have the Q201E in a HT setup not stereo so your going to have to do it with your ears but you can do it. I hate RELs manual as good as their subwoofers are they have a terrible manual.If you have Hotel California play it for it has a lot of bass making it easier to blend your sub with your mains. I'm no expert but I would keep the crossover setting between 55hz and 80hz giving the REL most of bass.


    good luck
    Blake

    Comment

    • benny
      Senior Member
      • Jan 2005
      • 112

      #3
      Most manufacture's default reccomendation is 80 Hz or so but we both know that's way too high for your setup. You've probably nailed it pretty close at 60, but why not just keep experimenting until it sounds "just right". Good luck!

      Comment

      • thyname
        Senior Member
        • Jan 2005
        • 358

        #4
        Thank you both for the advise guys! do you think I can use a RadioShack sound-level meter? Somebody had suggested I place the sub to the listening position and move around until the meter reads highest, there I place the sub. I thought that meter is for HT only... Then, how do I measure the sub only? How can I turn my speakers off with the sub playing? Again, I have a 2 channel setup (see my profile).

        Comment

        • ekkoville
          Senior Member
          • Aug 2004
          • 392

          #5
          I have a Rel Strata and also use the high pass cable. You might want to check your crossover settings in your preamp, if there are any, making sure they are getting a full signal. I have my Strata at 62Hz and like it very much.
          ____________________
          Erik
          Just another case of the man trying to keep us down! :B

          Comment

          • pramod
            Member
            • Dec 2005
            • 87

            #6
            Originally posted by thyname
            I recently purchased a REL sub Q150E to go with my 2 channel Rotel/Axiom system (see below my system). I use High-pass level connection in my sub, but I don't seem to set the crossover in the sub right. I initially thought I should set it 40 HZ, since my Axiom speakers are rated Freq Resp +/-3dB (Hz): 37 - 22kHz, to cover lower tones not covered by the mains, but then I moved it up to around 60 and sounded kind of better. What is the general rule of thumb? Any suggestions??

            Axiom M60s powered by Rotel RB-1080/RC-1070 combo
            Rotel RCD-1072 CD player, REL Q150E sub

            Hi, I have Rel Sterta 5 with BW-602S3 using Hi Level for music, and I have set it to drop everything below 80Hz, to the Sub, and I have set the crossover on the sub to max, in order to avoid overlap of freqs form the amp and the sub, as suggested in the manual, and I'm already enjoying it.... I need to experiment it more with the placement as it is critical in placement...
            Good Luck..
            Pramod..

            Comment

            • gianni
              Senior Member
              • Nov 2002
              • 524

              #7
              It is my understanding that the Q150E has no High Pass filtering. If this is true, it will indeed make good integration with your mains challenging.

              Ideally you would be able to filter signals below the desired crossover point from the mains. If your mains do in fact produce decent response into the high 30's, then you would not want the sub going much above this. The goal would be to get the sum of the main's natural frequency roll-off combined with the that of the crossover to compliment that of the slope used for the sub. Those using HT receivers in a dual role HT/music set-up have an advantage in being able to do this using the receiver's bass management to send the proper line level signal to the sub while removing low content from the mains. Even this scenario can get challenging as most full range speakers natural roll-off is less than an ideal match for available slopes in most receivers. (some satellite speakers such as M&K are designed with this natural roll-off but this is the exception and does limit your speaker choices). If you took it a step further, you would then have to consider sub woofer in room response which almost surley will throw another wrench into the equation.

              In your case with the RC-1070 lacking bass management, one thing would make your task a lot easier. I suggest using a bass management controller such as the M&K BMC-mini or the Outlaw BMC. Insert it between you 1070 and 1080. This will filter the signal to your mains to avoid double bass and allow you to use the preferred line level connection to your sub. This is the only way to achieve some sort of proper crossover between the mains and sub. Then you will have to fine tune it as best you can with positioning of mains, sub, seating position and other adjustments (the RS meter will be helpful).

              I know it sounds like a lot of trouble, but it is worth it. I use the BMC-mini even though I have an HT receiver. In my case, wanting to use my receiver's analog bypass inputs to avail myself of my Rotel RCD-1072 analog section, I found myself in a similar situation to yours. The mini allows me to bypass the digital processing and hear the 1072's analog output while doing a really nice job of integrating my mains/sub without any localization of the sub. Without some type of bass manager, you will have a mismatch and the best you can hope for is to experiment and find a setting that will be the least intrusive as possible. Good luck.

              Comment

              • thyname
                Senior Member
                • Jan 2005
                • 358

                #8
                It looks like I have a lot of work to do. I think that REL Q150E has high-pass filtering, even though different from the usual high-pass of other subs. Below is taken from the specs for Q150E in Rel website:

                -High quality, gas-tight Neutrik Speakon input (high level)
                -Totally discrete input circuitry for high and low level inputs
                -Separate volume controls for high and low-level adjustment
                -Simultaneous connection of high and low level sources

                To explain it a little bit better, that Neutrik Speakon cable gos from its input in the sub to the speaker binding posts in the poweamp (RB-1080) through yellow, black and red cables, two in the right speaker connection and one in the left. As such the sub gets a full signal from the power amp. Please note that I do not connect the sub to the preamp at all, and I set it (RC-1070) at zero to avoid any bass processing. Those BMC look very interesting, but do I really need them at all if I don't use my preamp with the sub?? Sorry if this sounds a little dummy question, but this the first time I own a real subwoofer.

                I have been "playing" a little more these days with the sub, and found the sound more pleasant with the crossover set at around 65 HZ and volume control a little lower (less than half). I also emailed REL technical support for some suggestions, but I have not heard from them. I have avoided calling them, since they are located in UK. Dissappoiting!!

                Comment

                • gianni
                  Senior Member
                  • Nov 2002
                  • 524

                  #9
                  I was not sure regarding the high pass of the Q150E so I looked around and found a review by Home Cinema Choice. They do say that it does not provide high pass filtering. Keep in mind that this is different than a high level connection.

                  You may be able to get it to blend reasonably well by experimenting, it seems you have made some improvements at least. The only down side to this is that your mains are still being run full range. If you have the sub set at 65 hz, you are still going to get reduced output above this frequency which will decrease to nothing at a rate dependent on the slope in use. How much bass doubling you are getting in the range where the sub and mains are overlapping is hard to say.

                  In the end it all comes down to whether the end result is accetable for you. In any case, if you are not happy, I think you can try the Outlaw unit and return it within 30 days if you are not satisfied. I do not know if they are still available, but they used to have B-stock units for sale with a good discount.

                  Enjoy the sub.

                  Comment

                  • ekkoville
                    Senior Member
                    • Aug 2004
                    • 392

                    #10
                    Setting the pre to zero may in the end cause some double processing of certain freqs around the bottom of the Axiom mains. While you do avoid processing from the pre, the freqs in that 37-60 range may seem mushed or overproduced. I guess what matters is that it sounds good, and tweaking will definately help that.
                    ____________________
                    Erik
                    Just another case of the man trying to keep us down! :B

                    Comment

                    • thyname
                      Senior Member
                      • Jan 2005
                      • 358

                      #11
                      I finally got an email from REL distributor in USA. Do they suggest I cross it over at around 25 HZ, or I read it wrong??!!!

                      Hello,

                      Thank you for your interest in REL. The best thing to do is to follow the four-step setup procedure outlined on our website, listed below, under REL / Owner's Manuals / REL Setup guide. This will get you to the right position and at the right settings. There is no "right answer" since room acoustics will affect the position of the controls. However, a good guess, based on a lot of experience, is that the crossover will be somewhere in the mid to high 20 Hz range, as the REL will play above the crossover point as well as below.

                      Sincerely,
                      Basically, the website instruction, as well as REL manual let you set it up with ear and NO recommendations on numbers are made at all.

                      Comment

                      • ekkoville
                        Senior Member
                        • Aug 2004
                        • 392

                        #12
                        You know, many have had success with a BFD, something I would like to get as well. That may also help with some of the room acoustic issues may encounter, if any.
                        ____________________
                        Erik
                        Just another case of the man trying to keep us down! :B

                        Comment

                        • benny
                          Senior Member
                          • Jan 2005
                          • 112

                          #13
                          Originally posted by thyname
                          Somebody had suggested I place the sub to the listening position and move around until the meter reads highest
                          Place the sub where you will be listening and move around the room until you find the spot where it SOUNDS best. Place your sub there and you're done! :T Many of the suggestions above are good and accurate, but you may not need to do all that to get the sound you want. Again, good luck with your new challenge!

                          Comment

                          • NewBuyer
                            Senior Member
                            • Feb 2005
                            • 122

                            #14
                            Personally I think that REL has it right-on-the-money with the method you are using to hook up your sub.

                            Having the sub receive the high-level signal from the amp ensures that the sub is receiving, and is in step with, exactly the same signal that your main speakers are receiving and reproducing. Also, having no high-pass filter ensures that you will not have to settle for any sonic degradation that can accompany such a filter.

                            I think that you have a very nice sub there - I hope you will enjoy it! I think that using the 60Hz setting is ideal for the speakers and setup that you describe. I'm thinking of getting exactly the same sub that you have.

                            -Regards

                            Comment

                            • Victor
                              Senior Member
                              • Apr 2002
                              • 338

                              #15
                              Thyname,

                              The -3 dB point of your main speakers is rated at 37 Hz. That means that the SPL is at 70% at this frequency. This also means that there is a significant phase shift will be occurring at this frequency. The phase shift will introduce the variance to the arrival times, and that will most likely correspond to audibly adverse perceived sound.

                              What you want is a seamless integration between your main speakers and the sub. Seamless would mean a flat SPL and true in phase characteristics across a crossover point. That means you have to find a frequency point that has no appreciable phase shift. Usually this point is at least an octave above the stated -3 dB. With this in mind I would try to set the crossover around 70 Hz. In fact your own observations seem to confirm the theory.

                              Good Luck, - your sub and your mains are truly a first class gear.

                              Victor

                              Comment

                              • thyname
                                Senior Member
                                • Jan 2005
                                • 358

                                #16
                                I really feel ignorant when reading such great posts here, I don't seem to know many of the facts people (like Victor and NewBuyer) mention. It takes me a while to understand part of it. I really appreciate your help. Your advice totally confirms other suggestions and my own initial experiences for a crossover setting around 60 HZ mark. However, it is totally different from the one suggested by REL distributor in USA (around 25-30 HZ) in his email I received today. Any comments?

                                I also undertand that I cannot adjust anything similar to a crossover in a receiver/processor found in multi-channel systems. Mine is simply a preamp with no bass management and not connected to the sub at all. Talking about crossovers in my case involves talking about setting the crossover at my sub only.

                                Comment

                                • bigburner
                                  Super Senior Member
                                  • May 2005
                                  • 2649

                                  #17
                                  thyname, like you I have struggled to understand the science behind seemless integration of subwoofers with main speakers. I have therefore had to rely on trial and error experimentation with how music sounds to determine the right settting.

                                  I do not understand REL's recommendation. If you listen to Hotel California (as comeup has suggested) with your sub set at 25 Hz you will hear very little coming out of your sub. My experimentation identified that very few music tracks contain significant sounds below 40 Hz. That makes me think REL's recommendation applies to HT only where explosions and dinosaurs' footsteps (for example) are frequently below 40 Hz.

                                  Are you able to connect your sub directly to the RCA outputs on the back of your RC-1070? I'm not suggesting that you do this permanently but it would enable you to turn off your RB-1080 and main speakers so that you can actually hear what is coming out of your sub at various frequencies. This may help you decide what is a sensible frequency to set the crossover. I'm guessing that Victor will be right on the money!

                                  Comment

                                  • miner
                                    Senior Member
                                    • Mar 2005
                                    • 900

                                    #18
                                    I also have a RC-1070 pre but my amp is the RB-1070. My mains are N804 with an ASW800 sub. I have my sub hooked directly the the pre outs on my pre-amp - a left & right sub cable going directly to my sub. My Xover freq (active) on the sub I have set at 55Hz. Why hook sub up to speaker terminals on the RB-1080? Why not hook sub up to RCAs on the RC-1070 pre? Please help me understand. Thanks.

                                    God be with the families/friends/coworkers of the deceased miners in WVa. I have been there in their situation - but I survived.

                                    Comment

                                    • thyname
                                      Senior Member
                                      • Jan 2005
                                      • 358

                                      #19
                                      Originally posted by miner
                                      Why hook sub up to speaker terminals on the RB-1080? Why not hook sub up to RCAs on the RC-1070 pre? Please help me understand. Thanks.
                                      That is the second option (to RC-1070 preouts) and called low-level. The one I am doing was strongly suggested from REL manual for Stereo 2 channel systems. I thought I would try the high-level first. I CAN do the low-level connection, but still have to try, as bigburners suggested as well. Will a regular RCA interconnect do? I understand that only one cable goes to the sub input, which one?

                                      Comment

                                      • audiofan
                                        Senior Member
                                        • May 2004
                                        • 272

                                        #20
                                        Thyname,
                                        may be this can help.... I quote this from the answer i got from av123.com forum:
                                        "If the pre-amp has no bass management, split the output from the preamp (not required if it has two outputs), run one set to the sub and use its crossover, run the other set through an in-line highpass filter then to the speaker amp. These filters range from $30 FMODs from PartsExpress to several hundred dollar Marchand units. An Outlaw ICBM would also do the job for ~$250, but is overkill since it's multichannel and not just two channel. "

                                        or you can read this from http://av123forum.com/showthread.php?threadid=11839

                                        Comment

                                        • miner
                                          Senior Member
                                          • Mar 2005
                                          • 900

                                          #21
                                          I understand that only one cable goes to the sub input, which one?

                                          B&W suggested I use 2 cables OR a 'Y' connector at the pre, use one cable to sub, another 'Y' at sub to split. I chose 2 single cables to cut down on the connections.

                                          Comment

                                          • Victor
                                            Senior Member
                                            • Apr 2002
                                            • 338

                                            #22
                                            Originally posted by thyname
                                            I really feel ignorant when reading such great posts here, I don't seem to know many of the facts people (like Victor and NewBuyer) mention. It takes me a while to understand part of it. I really appreciate your help. Your advice totally confirms other suggestions and my own initial experiences for a crossover setting around 60 HZ mark. However, it is totally different from the one suggested by REL distributor in USA (around 25-30 HZ) in his email I received today. Any comments?

                                            I also undertand that I cannot adjust anything similar to a crossover in a receiver/processor found in multi-channel systems. Mine is simply a preamp with no bass management and not connected to the sub at all. Talking about crossovers in my case involves talking about setting the crossover at my sub only.
                                            It is difficult to comment on the response you got from REL distributor. Frankly I do not understand the rational behind the suggestion to set the crossover point at 25-30 Hz. I think that it is a mistake and I would certainly not do that.

                                            What you need here is a simple cross-over circuit that would have both high-pass and low-pass filters with independently adjustable frequency points. Naturally it is always best to go a DIY route here, because there are many circuit boards and outright kits available for this project. However, if a DIY path is not in your future, then I would suggest an inexpensive box from Behringer that would do the trick for you. Look at

                                            CX3400
                                            or
                                            CX2310
                                            that sells for about $150US and $100US respectively. There are other similar units on the market form DBX and RANE, but the Behriger is the most cost-effective.

                                            The CX3400 is a 3-way crossover, while the CX-2310 is 2-way. Perhaps you do not need a 3-way box, but since it is only about $50 more expensive, it is well worth it and the one I would recommend you buy.

                                            I know that you might be inclined to think that the pro-audio gear such as this CX3400 is not strictly speaking an audiophile quality equipment. However, this is not so any longer. If you look at the specifications you’ll see that the box I am suggesting is completely transparent. The S/N is specified at 94 db for +4 dBu level. This is the level commonly used in the professional environment and in your application you will use much less then that, - meaning that you can expect a much better S/N, - most likely around 100 dB. The THD is specified at 0.04%, which is about 25 times better then what you can expect from your speakers and it is also better then your typical HT receiver THD specification. The every-day performance of this unit is about 16 bits. This is as good as it gets these days regardless of how much you are willing to pay.

                                            The CX3400 comes with only balanced input and output connectors as you would expect from a pro-audio unit. You can purchase XLR-RCA adapters or simply modify your cables, which what I would do, and your are all set, - good luck!

                                            Victor

                                            Comment

                                            • gianni
                                              Senior Member
                                              • Nov 2002
                                              • 524

                                              #23
                                              Thyname,

                                              At the prices some of these filters are approaching you are almost at the price of the Outlaw ICBM. (especially if you can get a b-stock under $200) The ICBM is very flexible allowing various crossover settings as well as other adjustments.

                                              The fact that it is multi-channel capable is hardly reason enough to call it overkill. This gives you many options in the future. If you want to read a review on the ICBM, there is one at AudioVideoRevolution.com. It may be a few more dollars than a basic filter, but you get a lot more flexibility too.

                                              Comment

                                              • Spearmint
                                                Senior Member
                                                • Sep 2004
                                                • 333

                                                #24
                                                I have just setup my 2ch using a 2ch pre amp and I am using a car xover to do the bass management for my system.

                                                The unit works well I cannot detect any induced audio with the xover in circuit and the sub works well.

                                                The unit I am using is the Coustic XM1e.
                                                Richard

                                                "Sometimes it is easier to ask forgiveness than to get permission... "

                                                Comment

                                                • thyname
                                                  Senior Member
                                                  • Jan 2005
                                                  • 358

                                                  #25
                                                  I tried the low-level connections today, I did not like them, it was either not enough or too boomy, depending on the volume knob setting.

                                                  I got another letter from REL distributor, after I wrote them my suspicision on their recommendations:
                                                  The REL is connected at High-level, which means you use the crossover in the REL, not the bass management features in the preamp. The REL is connected to your power amp. The REL connector attaches to the same binding posts to which your speaker cables connect (they share the binding post). The REL crossover plays above the crossover point. If you cross over at 25 Hz, it will play above 25 Hz, just as your speakers will play below 37 Hz (though possibly not at an audible level). The idea is to match the rolloff of the REL with the rolloff of your main speakers. This is done by ear; there is no need to concern yourself too much with the crossover point; I am simply stating that, in my experience, the REL is crossed-over around 25 Hz the overwhelming majority of the time when used with floorstanding speakers. If you follow the setup procedure outlined in our REL Setup guide, you will arrive at the proper crossover point.

                                                  Best,
                                                  Now it starts to make some sense, especially when talking about adjusting it to my listening preferences and not to a particular number in crossovers. Comments???

                                                  I thank you guys for the advice on those equipments. I will play and read a little more for a few weeks, and if I am not satisfied I will consider them.

                                                  Comment

                                                  • ekkoville
                                                    Senior Member
                                                    • Aug 2004
                                                    • 392

                                                    #26
                                                    I have always assumed when in a 2 ch mode with my Strata, that there would be a "leak" of sorts around the freq limits in the speakers and sub crossover. That said, if there was a digital crossover to set the point exactly, it would more possible to match each rolloff. But, alas we are again at what your ears like. If you like it, it is right.
                                                    ____________________
                                                    Erik
                                                    Just another case of the man trying to keep us down! :B

                                                    Comment

                                                    • audiofan
                                                      Senior Member
                                                      • May 2004
                                                      • 272

                                                      #27
                                                      Giani,
                                                      good advice on ICBM . I almost forgot about that. The manual http://pdf.outlawaudio.com/outlaw/docs/icbm_manual.pdf tell us exactly to do with 2-channel system. New one is about $249, but b-stock is a bit cheaper. Now the question is which sub is the best musical sub for 2-channel. I see REL, ATI, Totem, Onix. I have Totem Forrest , so i still prefer Totem Lighting, but still consider others as well.

                                                      Comment

                                                      • bigburner
                                                        Super Senior Member
                                                        • May 2005
                                                        • 2649

                                                        #28
                                                        thyname, after reading the next letter from your REL distributor I'm not convinced that he is a subject matter expert in subwoofer integration. His best advice seemed to be to refer to your REL Setup guide! Hmmm. However I do agree with not using the bass management in the preamp because as we both know the RC-1070 doesn't have any bass management functionality!!!

                                                        I'm certainly interested in the concept of using an external crossover / filter as suggested by a number of contributors to this thread. I currently use the high-pass filter on my ASW750 which is pre-set to 80Hz. The problem with this approach is that I have no choice regarding the crossover frequency. I presume that an external crossover / filter would provide that flexibility.

                                                        Comment

                                                        • audiofan
                                                          Senior Member
                                                          • May 2004
                                                          • 272

                                                          #29
                                                          I believe something like Outlaw ICBM will solve the problem. I read the review from audioholics about Onix ULW-10. It's pretty impressive and will fit nice with the combo rc-1070, rb-1080, ICBM.

                                                          Comment

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