65Hz or 170Hz for stereo subwoofers

Please provide reasons in comment.

  • 65 Hz + mono operation

    Votes: 7 50.0%
  • 170 Hz + stereo operation

    Votes: 7 50.0%

  • Total voters
    14
I have two subwoofers for stereo subwoofers setup. Each subwoofer is placed next to each left and right main speaker. Since the electronic crossover, a/d/s/ 642ix, has fixed frequency module. It requires to change the module to alter crossover frequency. The currently available modules are 65Hz @ 24dB/octave and 170Hz @ 24dB/octave. And the electronic crossover allows to select either mono or stereo subwoofer operation. The manual suggests to set the operation to stereo mode only when the crossover is set above 100Hz. I need advice which setting I should use. Note that this is two subwoofers system, not usual single subwoofer setup. Please vote the poll and reply the opinion on comments.
 
I had a similar setup before with dual subs that were initially mono beacuse that's all I could get from the one electronic crossover I had, an ART CX311.
Later I bought a second identical crossover specifically to get stereo for the subs and the improvement is really nice.
I run them at about 150 Hz with a 24dB/octave slope. There's lots of stereo content down there, and after all, that's the way the music is recorded and produced, so why change it?
 
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diyAudio Moderator
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I would guess the reason the higher frequency cross was offered in stereo is to retain the stereo effect for higher frequencies. Lower bass is sometimes in mono in any case. Stereo bass doesn't give the spatial diversity of multi subs. It's a rich tapestry of smaller concerns.

In any case, are these really subs if they're close to the mains or are they really woofers?
 
I have two subwoofers for stereo subwoofers setup. Each subwoofer is placed next to each left and right main speaker. Since the electronic crossover, a/d/s/ 642ix, has fixed frequency module. It requires to change the module to alter crossover frequency. The currently available modules are 65Hz @ 24dB/octave and 170Hz @ 24dB/octave. And the electronic crossover allows to select either mono or stereo subwoofer operation. The manual suggests to set the operation to stereo mode only when the crossover is set above 100Hz. I need advice which setting I should use. Note that this is two subwoofers system, not usual single subwoofer setup. Please vote the poll and reply the opinion on comments.
My 2 cents is that 170 is way too high for a "subwoofer" and given that you only have two options choose the other one (65Hz).

65 Hz should work better overall because it will be easier to integrate the subs at that frequency and the exact distance between the woofer and the subwoofer on each side is not critical. This also implies that you have some leeway to move the subs around in the room and they will still be "acoustically near" the mains.
 
frugal-phile™
Joined 2001
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It is nice if it operates that high, but it is more of meeting the goals of the design. Driver voicing is important. In a few of these cases we were just lucky the drivers we chose extended as high as they did.

Given tehre are so many compromises in any loudspeaker design, and even thou these exist as a small subset of designs, there are just so many things to weigh when choosing what we chose.

dave
 
For a ~200 Hz XO it would be nice to see at least 1kHz.
I find your description also very cryptic.
But I think what you're trying to say, is that for crossing a (sub)woofer around 200Hz, its frequency response should at least extend to 1kHz?

Best answer I can give, is that it all just depends on the distortion graph.
As long as that one isn't doing weird things in the frequency band we are interested in, it's basically fine.
There are (sub)woofers that don't extend all the way to 1kHz, bust still have a very usable response to work with up to around 200-250Hz.

Obviously one also has to take the frequency response into consideration.
So sometimes you have to compensate a little.

An average high quality 8-10 inch (or smaller) subwoofer has little trouble doing 200-250Hz.

But just check distortion and freq resp graphs, there isn't really a well working rule of thumb here.
 
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It obviously depends on your mains, but as I can't imagine a woofer that doesn't do 65hz, the crossover frequency for the subs should be 65hz.
To reduce distortion, subs should be in mono due to headroom and recording imbalances.
In a recording, or using a record deck where the sub bass signal is 3dB lower on one channel, in stereo, one chanel will reach its limit while the other is at 50%.
 
but as I can't imagine a woofer that doesn't do 65hz, the crossover frequency for the subs should be 65hz.
The question shouldn't be if a woofer can do 65Hz, but which one (sub or mains) will do 65Hz better.

Up to about 100-120Hz, it's impossible to very difficult to hear any localization anyway.
So crossing (much) lower isn't really beneficial.
In fact, I would advice filtering the mains higher to prevent any other non-lineairities due to less cone excursion.

In a stereo/multi symmetrical subwoofer setup, one can cross much higher.
In a multi sub setup, crossing higher is also advisable to have more freedom to tackle those pesky room modes.

As a general rule of thumb, cross as high as possible with a subwoofer, without it being to obvious and noticeable.
 
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Thank you for all advices.

To date, I ended up with 130Hz stereo mode. I had tried 100Hz and 170Hz. The former gave boosting about half bass range, some bass notes were played loud and some bass were not. The latter gave excessive rich male voice. Therefore, the 130Hz satisfied me very much.
 
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