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Subwoofer Selection Criteria

watchnerd

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Yeh :)



I would generally advise it. Especially if you're not going to HP filter them, and especially if your XO point will be as low as 50Hz, which is probably getting very close to the port tuning frequency.

But please remind me what your mains are?



Will definitely be easier if they're plugged. In the absence of measurements, I'd say it would be almost the only way to do it.
Dynaudio Contour 20 are the mains.

Stereophile and several European review places review them with the ports open vs plugged.
 

andreasmaaan

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Dynaudio Contour 20 are the mains.

Stereophile and several European review places review them with the ports open vs plugged.
Port tuning looks to be about 32 Hz. That's pretty close to where you're crossing them over. So plugging is probably a good move unless you're planning on doing a lot of measurements and/or raising the XO frequency. And I'd high-pass them too if I were you: it's a small woofer in a small box - no need to feed it frequencies it doesn't need to be reproducing IMHO, plus integration will be easier if you use filters at both ends.
 

watchnerd

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Port tuning looks to be about 32 Hz. That's pretty close to where you're crossing them over. So plugging is probably a good move unless you're planning on doing a lot of measurements and/or raising the XO frequency. And I'd high-pass them too if I were you: it's a small woofer in a small box - no need to feed it frequencies it doesn't need to be reproducing IMHO, plus integration will be easier if you use filters at both ends.
I'm not following what measuring and/or raising the XO frequency would have to do with plugging vs open.

In my mind, port vs plugged is mostly a matter of why have the cons of a port (woofer unloading) if I'm going to high pass the mains above the port frequency and not use it.
 

andreasmaaan

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I'm not following what measuring and/or raising the XO frequency would have to do with plugging vs open.

In my mind, port vs plugged is mostly a matter of why have the cons of a port (woofer unloading) if I'm going to high pass the mains above the port frequency and not use it.
I agree.

My comment was related to ease of integration though. If you don't plug the port, integration will be more difficult, so measurement will be a must. And even if you do integrate via measurement, crossing over close to the port tuning frequency (less than an octave if you cross at 50Hz) will be hard work.

I'd consider a higher XO frequency if I were you, more like 80Hz, for easier integration and less stress on the mains. But I know others here may disagree with me.
 

Soniclife

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I'd consider a higher XO frequency if I were you, more like 80Hz, for easier integration and less stress on the mains. But I know others here may disagree with me.
I agree, a proper XO is the best way to go, especially as he has complete control over delaying the mains or subs as required, so you can get the timing of the 2 systems in line. I've found getting the timing right makes a huge difference.
I would suggest sealed, and XO at at least 80hz 4th order, and run as stereo subs.
 

Krunok

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I agree, a proper XO is the best way to go, especially as he has complete control over delaying the mains or subs as required, so you can get the timing of the 2 systems in line. I've found getting the timing right makes a huge difference.
Interesting.. Would anybody care to explain how would getting subs and mains time aligned impact perceived SQ but getting woofer time aligned with mid and tweeter within the same speaker not?
 

Soniclife

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Interesting.. Would anybody care to explain how would getting subs and mains time aligned impact perceived SQ but getting woofer time aligned with mid and tweeter within the same speaker not?
The time differences can be very different between the 2 misalignments. Unless the XO in the 3 way is deliberately adding delay wrongly the offset between the drivers is likely to only a few mm, where as the sub could be meters different from the bass driver distance to LP. And when you add in the DSP delay that lots of subs have you add even more delay.

Anyone know what are the listening thresholds are for this?
 

andreasmaaan

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Anyone know what are the listening thresholds are for this?
The delay itself is unlikely to be audible: 2-3ms or even 10ms (equivalent to roughly 3m/10’) has not been shown to be audible in the low- or mid-bass.

What is more likely to be audible are the effects the delay has on amplitude response. But one would need more information about the room and sub/speaker locations to even speculate as to what the amplitude domain effects of a given delay might be.
 

Soniclife

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What is more likely to be audible are the effects the delay has on amplitude response. But one would need more information about the room and sub/speaker locations to even speculate as to what the amplitude domain effects of a given delay might be.
So more of a phase issue causing lumpy response?
 

andreasmaaan

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So more of a phase issue causing lumpy response?
IMO, yeh exactly.

Also keeping in mind that the low-pass filter itself and the box the sub driver is in are already causing likely more delay than 3-10ms in the same range of frequencies.
 

Soniclife

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How does one measure subwoofer to mains delays?
Start with a tape measure, and by trying to find out what the sub manufacturer says their internal delay is. My subs are said to have about 1m delay, which is 3ms.

So if the subs are 1m further from your ears than the mains, and their internal delay is quoted as 3ms then you probably need to use 6ms delay.

I would suggest sending the full range signal to the subs, not low passing them in the Devialet, then get them to filter themselves.
 

watchnerd

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Start with a tape measure, and by trying to find out what the sub manufacturer says their internal delay is. My subs are said to have about 1m delay, which is 3ms.

So if the subs are 1m further from your ears than the mains, and their internal delay is quoted as 3ms then you probably need to use 6ms delay.

I would suggest sending the full range signal to the subs, not low passing them in the Devialet, then get them to filter themselves.
Yes, I'm sending the full range signal to the subs (I have to, for headphone reasons).

A quick Google leads to nothing for "internal delay Dynamo 1100X". Is there another term of art?
 

andreasmaaan

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Yes, I'm sending the full range signal to the subs (I have to, for headphone reasons).

A quick Google leads to nothing for "internal delay Dynamo 1100X". Is there another term of art?
Perhaps "latency"?

EDIT: forgot that - just googled and found info only about the wireless connection's latency.

For now, you could assume zero internal delay on the sub in making your calculations (it's likely not to be very long, in any case), and then measure properly later when you get to that.

Even if this assumption is off by say 3ms, at 80Hz this will only result in a null in the direct sound at the crossover point of around 3dB, which is not negligible, but which is unlikely to be significant in the context of the various other factors at play (most importantly, room modal behaviour).
 
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Krunok

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How does one measure subwoofer to mains delays?
You can do it with REW. When measuring different speakers (left and right mains and subs) you have to use sweeps with timing reference signal set to the same speaker (for example left main).
 

watchnerd

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I agree.

My comment was related to ease of integration though. If you don't plug the port, integration will be more difficult, so measurement will be a must. And even if you do integrate via measurement, crossing over close to the port tuning frequency (less than an octave if you cross at 50Hz) will be hard work.

I'd consider a higher XO frequency if I were you, more like 80Hz, for easier integration and less stress on the mains. But I know others here may disagree with me.
So I experimented with both high-passing the mains and plugging the port, as well as adding 3 ms delay to the mains. I picked 53 Hz as a starting point because that's the F3 of the mains with the port plugged.

The good:

The subs and mains blended well. There is room for further fiddling, I'm sure, but the blending was pretty seamless.

The bad:

Plugging the ports over-damped the mid-woofer dramatically, crushing the dynamics and affecting the imaging and midrange in a bad way. The Contour 20 is pretty neutral / lean even with the ports open (maybe a bass alignment Q of .7), so plugging the port may have pushed things to .5 or even lower.

Taking the plugs out, but keeping the high pass (53 Hz) improved things dramatically and mostly sounded better than with no high pass and/or no sub.

It was an interesting exercise in "textbook generic" vs specific implementations.

The next step might be to leave the ports open and move the HP XO higher, so it's at least an octave above the port (>64 Hz).
 

Krunok

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So I experimented with both high-passing the mains and plugging the port, as well as adding 3 ms delay to the mains. I picked 53 Hz as a starting point because that's the F3 of the mains with the port plugged.

The good:

The subs and mains blended well. There is room for further fiddling, I'm sure, but the blending was pretty seamless.

The bad:

Plugging the ports over-damped the mid-woofer dramatically, crushing the dynamics and affecting the imaging and midrange in a bad way. The Contour 20 is pretty neutral / lean even with the ports open (maybe a bass alignment Q of .7), so plugging the port may have pushed things to .5 or even lower.

Taking the plugs out, but keeping the high pass (53 Hz) improved things dramatically and mostly sounded better than with no high pass and/or no sub.

It was an interesting exercise in "textbook generic" vs specific implementations.
It would be much easier for you to set it up with measurements as this way it's pretty much trial and error.

The next step might be to leave the ports open and move the HP XO higher, so it's at least an octave above the port (>64 Hz).
Yes, that seems logical.
 

Thomas savage

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Iv never had good experiences plugging ports , I had the same result as you it seems.

As for HP XO just double the port tuning frequency, I'd certainly not go lower than that.

Fortunately my preamp dose all this for me now, setting up subs by ear is ' chasing tail ' central.
 
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