How about this simple approach for subwoofer/speaker crossover?

Discussion in 'Speakers' started by Chris PC, Mar 24, 2003.

  1. Chris PC

    Chris PC Producer

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    I have been wondering about getting a crossover for my speakers and subwoofer for a while now. I am not thrilled with the 100 hz of my receiver, and quite frankly, I can't even use the 100 hz crossover in SOURCE DIRECT MODE, which is the best way to listen to music. So another words, listening to music in the best SOURCE DIRECT MODE has thus far meant NO SUBWOOFER. My subwoofer does not have a high-level speaker wire high-pass crossover for my main speakers, but it has a crossover for itself, the subwoofer, of 50-100 hz.

    Ostacles:

    1) I cannot run the speaker wire into the subwoofer because my subwoofer has no speaker wire input or crossover for the front speakers.
    2) I have no PRE-OUT - MAIN IN LOOP on my receiver and I am not using outboard amplification, so I cannot use an active crossover for my main front speakers at all.

    Instead of trying to find a "good" crossover to run the speaker wires through and use as a highpass AND lowpass crossover...why don't I do this?

    1) Fronts LARGE or SOURCE DIRECT (same thing)
    2) Avoid overlap by running front speakers through a high pass crossover.
    3) Connect subwoofer to front LEFT and RIGHT pre-out of receiver and use subwoofers low pass crossover to suit.

    So far I've been doing the above without the high pass, just setting my subwoofer to 50 hz, but because my fronts go to 32 hz - 3dB there's likely a big overlap from say 28 hz to upwards of 60 hz? Sounds ok "sometimes".

    All I'd have to buy is a high pass crossover, rather than both a high pass AND a low pass. Yes, I understand that the high pass crossover isn't quite the match of a good active crossover, but subwoofers have been supplied with these for years anyways and the results haven't been horrible. Surely speakers themselves have passive crossovers. I know there are phase shift issues, but isn't it worth a try?

    Any advice on the most cost effective HIGH PASS only speaker wire level crossover? I'd be willing to try a variable crossover, although I'm aware that a fixed one is better, as long as I can change it from one freqeuncy to another at least by simply swapping resistors. Say a fixed HIGH PASS of 50, 60, 70, 80 or even 90 hz?

    Any ideas?
     
  2. Leon O

    Leon O Stunt Coordinator

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    Hi Chris,

    Partsexpress.com should have passive crossovers to suit your needs.

    However, do you hear the overlap, or is it just the concept that affects you. If you like the sound of a little more emphasis in the lower regions, keep it. Should make movies more fun. For more than a year I looked at similar options, considering external amps and the Outlaw ICBM. However, I finally realized I like the sound as it is. (of course my next upgrade will require full bass management [​IMG] )

    BTW, if your main speakers have ports, you might try blocking one or more of them (I use rolled up socks). On my speakers, it eliminates some of the lowest region and actually seems to tighten the bass.

    Good Luck!
     
  3. Chriss M

    Chriss M Second Unit

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    it should work but you might want to do some more research before you just start buying crossovers. There are different types, with different slopes and resultant phase issues. You are going to try to integrate a seperate high pass filter with the low pass filter in your receiver so you'll need to at least have some idea of what you are doing or you'll probably just makes things worse.

    Any reason why you wouldnt just go for an ICBM? that would take care of any issues you have.
     
  4. Chris PC

    Chris PC Producer

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    Yeah, since the fronts are ported, I would likely want to, at the very least, avoid a 24 dB per octave slope.

    See my original post. I CANNOT use an ICBM because I've no way of inserting in the signal path.

    I have a better solution. How about this?

    I just had a thought. I think I have a very good and probably a decent and logical solution. Hear me out and comment on this idea.

    1) Front speakers running full range as LARGE or in SOURCE DIRECT (in SOURCE DIRECT the fronts run full range).
    2) Subwoofer running from LEFT and RIGHT pre-out of receiver and crossover set to 50 hz. (Receiver must be set to LARGE for times when I'm not in source direct, in surround modes for instance.)

    Now instead of a highpass on the front speakers, I do this:

    3) Use a Behringer BFD DSP 1124P to EQ the subwoofer and correct for any problems that the overlap of the FRONT and SUBWOOFER may be causing.

    Now the only issue is the overlap between the subwoofer and front speakers, the famous arguement of SUB=YES and FRONT=LARGE. I have tried that combo and it has sounded less than spectacular in my room. I will try it again out of curiosity though, as I believe my new speaker and subwoofer placement produces the best blend possible. My Mirage BPS-400 is placed directly between my PSB 6T front speakers. The side firing 12" woofers are about as close to each front speaker as you could possibly get, and therefore, I imagine the blend of propogated bass frequencies might be ideal. Who knows, but it makes sense and so far sounds the best in my room [​IMG]
     
  5. BruceD

    BruceD Screenwriter

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  6. Chris PC

    Chris PC Producer

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    I'm not talking about the speakers internal crossover. A sealed speakers lower most bottom octave is usually a 12 dB per octave roll-off or slope while a ported speakers roll-off in the bottom most bass region is 24 dB per octave. My subwoofer is sealed. My speakers are ported. If I put a "high-pass" crossover in the speaker path, I don't want it to be 24 dB per octave, because it doesn't need to be that steep. I figure 12 to 18 dB per octave is good enough. I guess it doesn't make much difference. My reasoning was that the crossover would be, lets say, at somewhere between 60 and 80 hz, well, once you were below 35 hz, where my speakers naturally begin to roll-off, I think that the combination of a 24 dB per octave crossover and the speakers lower most 24 dB octave roll-off would combine for 48 dB per octave roll-off down in the lower most octaves. Don't think thats too good? What do you think?
     
  7. BruceD

    BruceD Screenwriter

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    Here is how I see it.

    I found it extremely difficult to impossible to match asymmetrical crossovers between mains and sub for a truly smooth and balanced transition, just my own personal experience after wrestling with the processor sub-out and/or the sub's onboard xovers (which have an off position).

    In other words, I find it easier to keep SPL levels across the crossover boundary between mains + sub fairly flat with a symmetrical 24dB xover.

    Also I found that a sub produced much cleaner bass notes with more punch than my mains (at least in the 32-60Hz range) and actually allowed a cleaner mid-bass/mid-range to emerge from my mains (less IM distortion) when they were relived of
     
  8. Chris PC

    Chris PC Producer

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    Yeah, your crossover setup sounds like a good one. I'm envious [​IMG] Perhaps I'll go that route one day. I guess I could grab a good amp someday. I'll see [​IMG]
     
  9. BruceD

    BruceD Screenwriter

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    If you want to try some DIY options, Marchand sells their xovers in various kit forms, even down to just the xover PCB (no power supply or case).

    In addition, I know there are a number of sites that also list DIY options for 4th order symmetrical L-R xovers like this and also here
     

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