Aftermarket Bass Management. A Crazy idea whos time has come?

Discussion in 'Archived Threads 2001-2004' started by Chris PC, Aug 5, 2001.

  1. Chris PC

    Chris PC Producer

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    Preface: I ask this question since few receiver manufacturers have been offering proper bass management in their receivers, other than higher end, more expensive ones. And if they do offer it in their expensive ones, why on earth are we doing without it in the lower models? Its not an extra frill. Bass management is a fundamental requirement for proper system setup. On top of that, there has been a fair consensus that setting all main speakers to SMALL results in very good sound overall.
    OK. I have been struggling with the bass management, or lack of, in the receivers that I have been shopping for. The main problem is the use of a xover fixed at 100 hz when setting main speakers to SMALL. Some say this a 100 hz xover is a problem, while other say it is not a problem. Biggest problems with 100 hz xover mentioned were, 1) Localizing the subwoofer or 2) Poor sound due to vocals leaking into the sub or "boominess" or 3) Just plain difficulty matching subs with other speakers in the room to acheive flat response. Perhaps because manufacturers think receivers are used mainly for movies, that the best blend of subwoofer is not the most important.
    But many of use are using subwoofers and want to achieve the best integration with our other speakers for the sake of music and movies too? 99% of subwoofers have had adjustable crossovers since they have been marketed. So if the receiver is now able to send the sub a line level signal, why should we not have proper bass management? When you think about it, a receiver has even more need for proper bass management. A subwoofer already knows its response, and so they provide a crossover to match itself with other speakers, it is dealing with only ONE unknown, the OTHER speakers. A receiver is dealing with TWO unknowns, unknown subwoofer and unknown speakers. If subwoofers have had adjustable crossovers from say 50-100 hz, why don't MOST receivers? It makes no sense. Often, it seems like those who really like music often pay for the receivers that have good bass management, or they don't use a home theater receiver for music, but a stereo system.
    I mentioned this before and I know its next to impossible, but maybe its possible for someone with the skills and equipment. If you already have a business in making custom audio equipment, here is a great idea for you. Start tearing apart receivers that lack adjustable bass management below 100 hz. If you can locate the crossover part using diagrams or through testing for the SMALL speaker setting of the receiver, you could somehow retro-fit an aftermarket part or eprom with adjustable bass management from say 40hz to 120hz, maybe with choice of slope of either 12 dB per octave or 18 dB per octave. I think that would more than cover it. You'd have something that receiver owners would certainly find very very useful
    I suggest internal, because bass management like the Outlaw ICBM, apparantly cannot be used easily with a receiver to modify the internal xover. You cannot just attach it to your receiver and change the SMALL speaker xover. It only works for one source. If someone knows how to do it, then by all means, let me know. The idea of inserting it in the "pre-out" to "input" loop would cause nothing more than a feedback loop. Perhaps it could be used if you simply re-routed the pre-amp level signal out of the receiver, into the Outlaw ICBM and back into the receiver (you'd leave the speaker settings to LARGE and let the OUTLAW ICBM do the work). Perhaps this is the solution, rather than inventing a bass management device. Just re-route the signal to the ICBM and back. You'd have to determine where best in the signal path to do this. Yeah, sounds like it could be NOISY if done cheaply! Oh well, its worth a try. Is there another solution?
    So anybody out there know who would be up to the task? Handy electronics people, skilled PCB people, aftermarket companies?
    [Edited last by Chris PC on August 05, 2001 at 12:03 PM]
    [Edited last by Chris PC on August 05, 2001 at 02:36 PM]
    [Edited last by Chris PC on August 05, 2001 at 02:39 PM]
     
  2. GordonL

    GordonL Supporting Actor

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    A flexible subwoofer design should have adjustable crossovers AND left/right line levels in/out. This will allow you to send your L/R main pre-out to the sub and then back to the receivers main-in. At the receiver, set your speakers to large and with no sub. This merges the DD .1 signal into the front L/R signal which the sub's crossover handles. If your sub is like this, then you don't need to worry about bass management in your receiver. The only thing you need to look for then, is pre-out/main-in on the main channels.
     
  3. Wayne A. Pflughaupt

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    Chris,
    This would be a logistical nightmare. Can you imagine trying to design something that would easily retro to for every applicable receiver on the market? There are literally dozens of them, and they are all designed differently, especially from one manufacturer to the next. It would be next to impossible to pull this off. Even if you were able to, it would probably be obsolete as soon as the manufacturers issue newly designed products.
    Then there is the problem of actually making the retro bass management function. You would have to reprogram each receiver’s firmware, so that the menu system could access the controls. Either that, or find a place to mount accessible “hard controls” (knobs, switches, etc.) some place on the chassis that is convenient and accessible to the user.
    And how much would you be willing to pay for this? I guarantee it would be more worthwhile and cost effective to simply upgrade your receiver.
    There are really only two practical alternatives if you don’t like your receiver’s bass management: add and outboard electronic crossover, or select a new receiver with a crossover frequency that is suitable for your speakers.
    Regards,
    Wayne A. Pflughaupt
    ------------------
    My Equipment List
     
  4. Chris PC

    Chris PC Producer

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    Wayne,
    I guess I was hoping someone would be able to do custom work on a receiver on an individual basis. All I am talking about is taking the preamp level signal and outputing it to something like the ICBM and back into the receiver to be amplified. I guess that was the best idea I came up with while typing out my thoughts, and my idea of building a crossover into the receiver is really no longer valid, as like you say, its too complicated. Instead of have some work done on a receiver, I am researching what receivers might suit my use, and any pre-pro and amplifier setups also.
    See, I thought you could take the entire signal from the 6 or 7 pre-outs and use an outboard crossover and send it back into the receiver to be amplified.
    So when you say use an outboard electronic crossover, are you talking about also using outboard amplification?
    Gordon,
    An interesting idea. My sub has a L and R input which go through the Mirage internal xover (50-100hz at 18 dB per octave) or a single input without any internal crossover. Unfortunately, there are no outputs on the subwoofer.
    If a receiver I am looking at has Main outputs and Main inputs, then your idea is possible. The problem with that is, when you Choose front Large and SUB no,then you have redirected all bass to the front L & R, you have crossed them over at some frequency. What frequency is that? The center and surrounds are not getting the bass, but below what frequency is the .1 content? On top of that, you then crossover the bass a SECOND time and re-direct it to your subwoofer. That's cascading crossovers.
    I don't know if any of this is such a big deal, its just what some have told me when I have suggested what you are saying.
    [Edited last by Chris PC on August 05, 2001 at 03:33 PM]
     
  5. Wayne A. Pflughaupt

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    quote: See, I thought you could take the entire signal from the 6 or 7 pre-outs and use an outboard crossover and send it back into the receiver to be amplified.[/quote]
    This kind of thing used to be pretty easy in the old days of non-computerized two-channel receivers. Typically there were a couple of wires going from the volume control at the front of the chassis to a circuit board elsewhere. Since the volume control is the last thing in the pre-amp section’s signal chain, you can see that the wires were plugged into the receiver’s amplifier section. Anyone with a little electronic savvy could detach the wires and re-route them for some new purpose, like by-passing a blown amplifier section.
    Unfortunately, things are not so simple anymore. I’ve only popped the cover of one late-model receiver, and a link between the pre- and amp sections were not readily apparent.
    But actually, Chris, you are making this harder that it needs to be. While the blend between the L/R channels and sub is critical, there is really no problem if the high pass filter on the rears and center do not match the left/right/sub set up. For instance, have you ever seen a movie where the music is only in the rear speakers and LFE channel? Typically music is in the front channels, or all channels, and the front L/R sub combination handles the bass. Even if the sound source features a crash or explosion dedicated to the rear channels, the low frequency content will be far below the the rear’s high pass filter. In other words, if the filter for your rears and center is 100Hz, and the sub’s low pass is 80Hz, you really aren’t going to miss anything. As long as the left and right speakers are filtered at the same frequency, you’ve got it covered 99.5% of the time.
    The prospect of outboard filtering of six or seven channels is as nightmarish as the prospect of modifying a receiver for a retro bass management package. The only multi-channel crossover I have ever heard of, I think, is the three-channel Paradigm X-10 and –20 (and I may be wrong about it being three-channel). You’re probably looking at the prospect of setting up at least three outboard crossovers. As detailed above, this is more work and expense than necessary.
    quote: So when you say use an outboard electronic crossover, are you talking about also using outboard amplification?[/quote]
    If the receiver has pre-out and main-in jacks, the high-pass output from the crossover could be sent back to the receiver. The low-pass would be sent to the powered sub.
    quote: The problem with that is, when you Choose front Large and SUB no, then you have redirected all bass to the front L & R, you have crossed them over at some frequency. What frequency is that? [/quote]
    That would be the same frequency determined by the receiver.
    quote: ….The center and surrounds are not getting the bass, but below what frequency is the .1 content? On top of that, you then crossover the bass a SECOND time and re-direct it to your subwoofer. That's cascading crossovers.[/quote]
    When you select “front large” and "no sub,” the LFE signal is folded back to the L/R channels, and is then processed by whatever filtering is in place there--outboard crossover, sub loop between receiver pre-out and main-in jacks, etc. There is no second crossover.
    Actually, there would be a second filter using an outboard crossover, namely the sub’s crossover. However, this is dealt with in the same manner as if the filtered LFE signal was being sent to a sub: raise the sub’s crossover all the way, or use the bypass switch, if there is one. Cascading is fine as long as the sub’s highest crossover setting is well enough the other one so that it is effectively “out of range.” I expect that investigation into stories of negative results from cascading crossovers will determine that the sub’s highest frequency was too close to the receivers. If the sub’s highest crossover setting is too close to the one in the outboard crossover, then the pre-out signal from the receiver could be split to send a full-range signal to the sub.
    Hope this helps. I know it’s frustrating when your gear is not set up to so what you need it to.
    Regards,
    Wayne A. Pflughaupt
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    My Equipment List
    [Edited last by Wayne A. Pflughaupt on August 05, 2001 at 09:42 PM]
     
  6. GordonL

    GordonL Supporting Actor

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  7. Chris PC

    Chris PC Producer

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    I think I understand, but when you select fronts to LARGE and SUB to NO, what do you set your front center and rear surrounds to? If you do set them to SMALL, then they must xover the bass to the front L & R, correct? Do you instead set them to LARGE when you have fronts on LARGE and SUB as NO? this is what I meant about the 2 xovers. I was talking about bass going to the center and surrounds.
    As I have done some research into what can be done, I have come across:
    1) The one peice of equipment that would do exactly what I want to do would have to be used with outboard AMPS, between a preamp and an amplifier. The OUTLAW ICBM. It allows xover selection for at least 5 channels. 40,60,80hz and higher. Its not out yet. It would work perfectly between a pre-amp and an amplifier.
    2) The Paradigm X-30 accepts a line level L & R and will pass a low level signal bacl to the receivers main in. Xover is restricted to 50, 80 or 120 hz at 18 dB per octave. Subwoofer xover is adjustable from 35-150 , same slope.
    3) Mirage has a couple of crossovers, the LFX-2 (2 channel) and the LFX-3 (3 channel). Both have selectable highpass outputs of 50, 63 , 80 and 100 hz. They are discountinued. They also allow adjusting the shape of the curve. Again, using 2 LFX-3's between a PRE-AMP and AMPLIFIER would cover 6 channels individually.
    The best solution would be to set the FRONTS to LARGE and SUB to NO, and use one LFX-2 between the main out and main in of a receiver. If I could do that with a xover, I'd be fine. Most of my critical listening will be with stereo sources anyways. If others have done this with success, then its probably the best way to go. It gives me the control I want, without getting too complicated. I'll only resort to that if the SR 6200's internal xover doesn't cut it, and the SR 6200 does in fact have main out and main in.
    thanks for the help and advice [​IMG]
    [Edited last by Chris PC on August 05, 2001 at 11:35 PM]
     
  8. Chris PC

    Chris PC Producer

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    And as usually happens, I come full circle and realize why I have asked the question in the first place.
    The Marantz SR 7200 and 6200 have no Main out and Main in. Neither do the Denon 3802 or the Integra 6.2. The 3802 nd 6.2 do at least have 80hz as there xover though. They only have 7 channel Pre-out and 7 channel input. I cannot use outboard crossovers like the Mirage LFX-2 or Paradigm X-30 without outboard amplification. That is why I am searching for another option than the Marantz.
    [Edited last by Chris PC on August 05, 2001 at 11:40 PM]
    [Edited last by Chris PC on August 06, 2001 at 10:52 AM]
     
  9. GordonL

    GordonL Supporting Actor

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  10. Chris PC

    Chris PC Producer

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    If its merged, as you say, then that would work better. But I reflect here that it is bass. So it must be crossed over somewhere? I mean, if the bass is sent to the front speakers, at what frequency does it stop?
    The one thing I have heard though, is that xovers in receivers are very brick wall like, or in some cases, they are digital?
    Yes, I must look at receivers. I had a budget in mind and its not workable with separates.
    [Edited last by Chris PC on August 06, 2001 at 09:41 PM]
     

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