Please help me integrate my subwoofer

[kifeep]

Make sure that the sweeps you choose for the subwoofer and speakers are ones that were performed with the crossover enabled and set to your desired crossover frequency.

I'm not sure I understand this part. If the crossover is enabled, both the sub and the speaker will play when a signal is sent to the speaker. And a signal sent on the LFE channel will be LPed at the LFE freq, not the XO freq.

Should I physically disconnect first the speaker, then the sub, to get LP and HP responses before aligning the phase?

 

[terryforsythe]

Should I physically disconnect first the speaker, then the sub, to get LP and HP responses before aligning the phase?

Yes. Run one of your speakers with the sub turned off, and then the sub with the speakers disconnected. The crossover needs to be enabled for both sweeps.

 

[kifeep]

As a side note, too often people choose too low of a crossover frequency for their speakers, which makes getting the transition smooth more difficult. Generally speaking, I usually choose a frequency that is around 1 octave higher than the resonant frequency of the speaker's woofer. You can determine that by running an impedance sweep on the speaker.

I'm not sure of the resonant frequency, and I don't think I have the tools for an impedance sweep. But they have an F3 of 34hz, so I assume it's pretty low. But they do struggle down there, so assuming I can get good results, I'd be happy crossed at 80hz.

Also, if the speakers are ported, I have achieved better subwoofer integration by plugging the ports of the speakers. I put dense foam in mine. You can try it both ways and see which one works best for your speakers.

The manufacturer says the woofer doesn't behave well unported. I suppose I could try it, but I'd prefer to avoid unintended consequences.

 

[kifeep]

Yes. Run one of your speakers with the sub turned off, and then the sub with the speakers disconnected. The crossover needs to be enabled for both sweeps.

Got it. Thanks.

 

[terryforsythe]

What speakers are they? Are they active or passive?

 

[kifeep]

Philharmonic BMR Monitors. Passive.

 

[kifeep]

Found an impendance graph online

 

[terryforsythe]

Philharmonic BMR Monitors. Passive.

Plugging the ports will change the frequency response in the low frequencies, but you will be covering that with the subwoofer. You can try it both ways and see which one works best.

I would start with a 100 Hz crossover frequency, then adjust it up if needed depending on your room response.

 

[terryforsythe]

Found an impendance graph online

The woofer's resonant frequency in the enclosure is around 59 Hz (highest peak of the red line). The further higher you move the crossover away from the phase transition, which is around 68 Hz as shown in the graph (blue line), the easier it should be to smooth the crossover transition.

 

[kifeep]

Thanks for all your help. I'll give this go tomorrow.

But just as a thought experiment, and an opportunity to learn something, I noticed that the crossover on the center speaker is much, much smoother:

The center is placed too close to the wall, which I assumed was a problem. But if the wall is interfering with the port, would that explain the better response? Starting to wonder if this might be even easier than I thought, if plugging the ports could make this much difference by itself...

Curious if my intuition about this is plausible.

 

[terryforsythe]

Being near the wall may have something to do with it, as well as the distance from the listening position. If it is further away than the left and right speakers, there may be less phase difference between it and the sub.

 

[kifeep]

Ok, interesting. It's actually closer to the LP. And the phase is closer to the sub than L&R are, but still not really aligned. The FR graph above was center crossed at 80hz.

 

[terryforsythe]

Another note - don't be afraid to overlap the crossover frequencies a bit. For example, in my room I have a dip in response centered around 105 Hz due to a room mode. I crossed my speakers at 90 Hz and crossed the sub at 120 Hz. Having the speakers and sub all covering 90 Hz - 120 Hz helped fill in the dip.

 

[kifeep]

Another note - don't be afraid to overlap the crossover frequencies a bit. For example, in my room I have a dip in response centered around 105 Hz due to a room mode. I crossed my speakers at 90 Hz and crossed the sub at 120 Hz. Having the speakers and sub all covering 90 Hz - 120 Hz helped fill in the dip.

Yeah, unfortunately, we're back at the limitation of AVR crossovers. I can't do that.

But the phase graph does suggest that if I crossed at 90 hz, I could conceivable get LCR all aligned with the sub, correct?

 

[kifeep]

Can't read my own graph. L and R are already aligned with the sub at 90, it's C that different.

 

[terryforsythe]

Since the center speaker is a little out of phase with the left and right, you won't be able to get it perfect, but will be able to improve it.

 

[kifeep]

Just playing around with the alignment tool. It looks like the phase is quite close at 90 hz:

But the alignment tool calculates -11.36ms delay to align them:

This seems large to me, mostly the -3.896m distance equivalent. Does that seem right?

 

[kifeep]

The phase actually matches at 88.59 hz, but alignment tool still says -11.36 ms delay.

I'm confused.

 

[terryforsythe]

The delay recommended is a negative number. That means the delay actually should be applied to the speakers. Is your subwoofer closer to the listening position than the speakers?

If the speakers and sub are in phase at the crossover frequency with the crossover enabled, but the frequency response still is not optimal, you should try using steeper crossover sloaps and/or a higher crossover frequency. I would try 120 Hz. Since REW's phase alignment tool seems off, try manually adjusting the time delay.

 

[OCA]

You subwoofer needs an additional 18.3ms of delay (6,27 meters) to clear up those dips in the crossover region:

I understand this is over the Audyssey distance limit and your chosen IR peak is a good compromise. You could "just" get away with it if you have an older model receiver with speed of sound set to 300 m/s.

You can still try to improve the dips increasing the SW distance as much as possible (6m + the distance of closest speaker).