Can anyone help with Alignment?

[Flaesh]

It seems I need to sum the signal of Output Channel 1 & 2 to the subwoofer.

Am I correct in thinking that I can do this by simply selecting both Input A & B at Output 1?

Yes.

 

[Robbie010]

Afternoon all.

Just a little update / feedback on this sub connection query. I did some tweaking today in order to rework the woofer to better integrate with the sub.

As suggested, I connected the sub to Output 1 and chose input A & B. As mentioned previously, Output 1 & 2 are “linked” but nothing is physically connected to Output 2.

When running sweeps in REW, L + Sub and R + Sub were fairly well matched and the sub gain seemed right, however, when I ran a sweep with both L & R driven the subwoofer output was roughly +6db.

I corrected this in the dsp/crossover but I’m now wondering whether this is right!?

 

[3ll3d00d]

When running sweeps in REW, L + Sub and R + Sub were fairly well matched and the sub gain seemed right, however, when I ran a sweep with both L & R driven the subwoofer output was roughly +6db.

I corrected this in the dsp/crossover but I’m now wondering whether this is right!?

This is exactly what I was talking about in the previous post. 2 channels playing together should be 6dB up. Measure separately is the right thing to do.

 

[Salt]

If a single channel sums up main speaker and sub properly, so two speakers and sub with summed up A and B should do the same (as two speakers are 6 dB more equal to sub)?

 

[Robbie010]

Ok gents, I’m not understanding what is the “correct” thing to do here…...

I measure L+Sub I get a good FR

I measure R+Sub I get a good FR

I measure L+R+Sub I get +6db at sub levels and this is a result of the sub signal being doubled-up.

Everyone agrees that is what is expected but it is surely not the desired result.

So, what do I need to do here, measure a single speaker individually and set the sub gain -3db below my preferred level, so that it sums when both play?

Or, change the settings in the dsp/crossover so that the sub doesn’t receive the doubled-up signal?

 

[levimax]

I measure L+R+Sub I get +6db at sub levels and this is a result of the sub signal being doubled-up.

Everyone agrees that is what is expected but it is surely not the desired result.

Why is it not the desired result?

I am not sure how your DSP works but if you have it set up correctly and you measure one channel at a time with the sub playing whatever is on the one channel and the levels are what you want then the levels should be OK when playing L+R together as you would get +6dB from the L+R playing together and + 6 dB from the sub summing to mono.

 

[3ll3d00d]

If a single channel sums up main speaker and sub properly, so two speakers and sub with summed up A and B should do the same (as two speakers are 6 dB more equal to sub)?

Sweeping LR simultaneously means sending exactly the same signal to a single sub twice hence +6dB, ie it is summed electrically

Meanwhile the same signal also goes to two separate speakers in physically distinct locations, ie they are summed acoustically and the result will be some comb filtered mess (to a mic)

 

[Robbie010]

Ok, I think I understand now, when reading earlier comments it seemed that what my measurements showed was incorrect somehow.

After re-doing the crossovers without the sub, the response looks like this:

With sub:

 

[OCA]

Ok, I think I understand now, when reading earlier comments it seemed that what my measurements showed was incorrect somehow.

After re-doing the crossovers without the sub, the response looks like this:

View attachment 488929

With sub:

View attachment 488935

You can get identical result to the green response in REW by "vector averaging" vector sums of "sub + L" and "sub + R" if sub and speakers are individually measured with the crossovers active.