DIY sub crossover questions...

Discussion in 'Archived Threads 2001-2004' started by dave shreve, Jan 3, 2002.

  1. dave shreve

    dave shreve Extra

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    It is really important to me that my sub(which I am currently designing/planning/acquiring tools) blend in well with my mains for music and movies. I have a Yamaha RX-V592 DPL receiver without digital surround. It DOES, however, have a sub out because it is a 5.1-ready receiver. Whenever not connected to a 5.1 decoder, the sub out receives a copy of everything 200Hz and below, with no bass management options for the mains. Since my mains reproduce well down to ~40-45Hz, it seems that just using this sub pre-out would not be conducive to a smooth, seamless transition between the mains and sub.

    I ALSO don't want to cut the mains off at 125Hz like most of the plate amps seem to do, as I don't want to run the sub that high. I think I want to make the transition from mains to sub somewhere in the 50-70Hz region. One option is to buy the Adire HS200 amp with active high and low pass controls. Another option is to buy a cheap plate amp, like one of the Parts Express 250 watt units and add an active crossover to my receiver via the tape monitor loop.

    If I add a crossover via the monitor loop, will it affect DPL decoding? Or will it even get a signal when using Pro Logic? Are the Behringer crossovers good and quiet? They seem to have the right features and be cheap enough. Going with the outboard crossover is cheaper and it keeps me from making an extra run of interconnects between the front of the room and the rear corner where the sub will be.

    Also, I will likely be moving to a DD/DTS receiver within the year. I am leaning toward the Denon 1802 at the moment. How good is the onboard bass management on digital surround receivers? Will I want to use the onboard setup or set the mains to large, turn off the sub out, and use an active crossover. Again, it's really important to me that the sub and mains blend smoothly. Will I even be able to put in a crossover on the preamp side of a DD/DTS receiver?

    -dave
     
  2. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    Usually the tape monitor loop can be used with ProLogic processing. Try this - play a CD or something in Prologic mode. Then switch in the tape monitor loop (with nothing attached to the tape monitor inputs/outputs). You should get nothing. Then try connecting a pair of wires directly from the tape monitor outputs to the tape monitor inputs. Now try the source material in ProLogic mode with the tape loop. It should work this time. And that confirms that the tape loop works in ProLogic mode.

    Now the question is - Does the subwoofer output get a copy of the bass BEFORE the tape loop or AFTER the tape loop. If it gets its copy after the tape loop and you've got a hi-pass filter in the tape loop then you've just filtered out the bass to your subwoofer too. Not a good thing. I don't know how to test this other than having a filter and subwoofer to play with.

    You could choose to run your main speakers full range and use a plate amp on the subwoofer to select a low-pass frequency that matches up with the frequency output of your main speakers so that it just extends the bass response. This would be around 40 - 60Hz.

    Of the DD/DTS receivers out now, only the Sony's and the Outlaw have flexible crossover points. Most others are fixed at 80Hz while a few are stuck at 90Hz or 100Hz. 80Hz can work very well if you have a quality, low-Q subwoofer.

    A very few receivers will have both pre-amp outputs and pre-amp inputs. This would allow you to put some equalization or other processor in just before amplification. The Outlaw ICBM would be ideal for taking on bass management duties in this case. The only receiver I can think of that offers this is the Harmon Kardon 520. I believe it comes with connectors that short the pre-amp out to the pre-amp in by default.
     
  3. dave shreve

    dave shreve Extra

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    'Try this - play a CD or something in Prologic mode. Then switch in the tape monitor loop (with nothing attached to the tape monitor inputs/outputs).'

    That's a fine idea there. I guess I should have thought of that myself.

    'Now the question is - Does the subwoofer output get a copy of the bass BEFORE the tape loop or AFTER the tape loop. If it gets its copy after the tape loop and you've got a hi-pass filter in the tape loop then you've just filtered out the bass to your subwoofer too.'

    It doesn't matter. I'll be using the crossover to send the lows to the sub and the highs back into the receiver.

    'You could choose to run your main speakers full range and use a plate amp on the subwoofer to select a low-pass frequency that matches up with the frequency output of your main speakers so that it just extends the bass response. This would be around 40 - 60Hz.'

    Actually, I want to avoid doing that if I can(inexpensively) as my mains are rear ported, making them a bit boomy in the ~40-50Hz range because I have them close to the wall.

    The Denon is fixed at 80Hz, so I think I can be happy with it. However, I didn't realize that most DD/DTS receivers lack pre-out/main-in functionality. I assume that a tape monitor loop is useless for 5.1 stuff.

    I looked at the ICBM, but it's a bit pricier than an active 2-ch crossover, and the sub and main x-over points don't appear to be independently adjustable, so I think I'll pass on it. Well, unless I get an SACD player...

    Anyone have any experience with an active 2-ch, 2-way crossover? Like I said above, the Behringer units are cheap, but I can't find any feedback on them.

    -dave

    -dave
     

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