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[Nathan Riddle]

So last night I was packing the trailer with my business partner for a retreat this weekend and we were talking about our future large gig. (the arena one which I have a different thread on).

I was commenting on how I'm trying to rent more TH118's for the gig and haven't had much luck. He suggested combining the 2x TH118's with some KW181's for more spl. I was like no way, not gonna work, phase cancelation, etc, etc.

But then I got to thinking.  What if it would work? I have access to 4x 181's. Obviously I realize more TH118's would be easier, but might not be possible.

I could either run subs with different xovers to help eliminate phase cancellation...but then that adds to the complexity of correct phase alignment between tops+bass+sub-bass.

So scratch that. What if utilizing smaart I trace the subs and try to use all-pass filters to help align the subs phase responses on our xilica? and then align the tops with the combined sub response? could that work?

I read through some threads on here about combining different subs and it seems possible and *could* yield good results. But there's no way of knowing until trying it.

What should my general approach be? Are there any articles or books I could read which would help?

tl;dr Would combining Th118 + KW181, utilizing SMAART traces to align them phase wise, and utilizing all-pass filters to help the phase alignment work?

[Keith Broughton]

So last night I was packing the trailer with my business partner for a retreat this weekend and we were talking about our future large gig. (the arena one which I have a different thread on).

I was commenting on how I'm trying to rent more TH118's for the gig and haven't had much luck. He suggested combining the 2x TH118's with some KW181's for more spl. I was like no way, not gonna work, phase cancelation, etc, etc.

But then I got to thinking.  What if it would work? I have access to 4x 181's. Obviously I realize more TH118's would be easier, but might not be possible.

I could either run subs with different xovers to help eliminate phase cancellation...but then that adds to the complexity of correct phase alignment between tops+bass+sub-bass.

So scratch that. What if utilizing smaart I trace the subs and try to use all-pass filters to help align the subs phase responses on our xilica? and then align the tops with the combined sub response? could that work?

I read through some threads on here about combining different subs and it seems possible and *could* yield good results. But there's no way of knowing until trying it.

What should my general approach be? Are there any articles or books I could read which would help?

tl;dr Would combining Th118 + KW181, utilizing SMAART traces to align them phase wise, and utilizing all-pass filters to help the phase alignment work?

It is possible to use something like SMARRT and get the subs playing well together but it can be a bit of a PITA.
Why not rent subs that are a better match to the ones you already own?

[Ivan Beaver]

The answer is "it depends".

Part of the problem is that you are dealing with 2 very different types of cabinets that have very different phase responses.

Will you be able to get them to work together across the freq range of interest?

Maybe.

But this is not a "step by step" type of thing.

There are A LOT of "it depends".

The way I would approach it is to forget about the tops (for now).

Put the cabinets side by side and put the mic on the ground inbetween them-about 10-20' away.

This is best done OUTSIDE-and away from reflections.

Since the reflections could affect the cabinets differently-because they are in different physical positions.

Measure the amplitude and phase response of one type of cabinet.  I would choose the TH118-because it will have the longest delay.

Now without changing the arrival time/delay, measure the other cabinet.

Now try to "adjust" by whatever means you have available" to get the amplitude and phase to match the TH118.

When you have it where you feel it is close-it doesn't have to be exact as there is a bit of "fudge room" down in the sub area.

Now turn on the Th118 and see if the amplitude has risen across the whole sub range.

If so-good.  If not-try again.

Now align the tops to the subs.

[Cailen Waddell]

Why not take the dual PA approach...  Divide the subs duty up by instrument...


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[Art Welter]

Why not take the dual PA approach...  Divide the subs duty up by instrument...

Because the dual PA approach would sacrifice 6 dB of output compared to phase aligned subs.

[Nathan Riddle]

Why not rent subs that are a better match to the ones you already own?

Currently I am unable to find anyone in my area with rental stock.

Why not take the dual PA approach...  Divide the subs duty up by instrument...

Because the dual PA approach would sacrifice 6 dB of output compared to phase aligned subs.

That's what I was thinking at first, but then realized I'd loose spl doing it that way (basically the whole point of more subs) and the alignment between subs at xover points would be a pain.

[Nathan Riddle]

The answer is "it depends".

Part of the problem is that you are dealing with 2 very different types of cabinets that have very different phase responses.

Will you be able to get them to work together across the freq range of interest?

Maybe.

But this is not a "step by step" type of thing.

There are A LOT of "it depends".

The way I would approach it is to forget about the tops (for now).

Put the cabinets side by side and put the mic on the ground inbetween them-about 10-20' away.

This is best done OUTSIDE-and away from reflections.

Since the reflections could affect the cabinets differently-because they are in different physical positions.

Measure the amplitude and phase response of one type of cabinet.  I would choose the TH118-because it will have the longest delay.

Now without changing the arrival time/delay, measure the other cabinet.

Now try to "adjust" by whatever means you have available" to get the amplitude and phase to match the TH118.

When you have it where you feel it is close-it doesn't have to be exact as there is a bit of "fudge room" down in the sub area.

Now turn on the Th118 and see if the amplitude has risen across the whole sub range.

If so-good.  If not-try again.

Now align the tops to the subs.

Thanks, I'm very grateful for the systematic approach you present here.

My thoughts on the matter originally, was it wouldn't work at all... but then I checked my thinking and figured I haven't tried it or measured it and now that I have smaart and can fiddle with things with actual measurements (obviously I'm still learning, not implying that it will be perfect) perhaps it may work out well? If I haven't tried how can I say it won't work? At MOST, all I can say "it depends" or "maybe, but probably not." Right?

One question I have about the process is should I be limiting the range 'better' to the 'lessor' of the cabinets or let both run naturally?

For instance: hpf the TH118 @ 30 & hpf the 181 @ 40
OR
hpf both 118 & 181 to 40hz so as they match?

What about lpf? don't worry about it until aligning with tops? or set at some nominal value that 'should' work in the end.

[Paul G. OBrien]

Because the dual PA approach would sacrifice 6 dB of output compared to phase aligned subs.

But you only get 6dB more output if both sets of subs are perfectly phase aligned and are capable of the same output SPL. Which is the other thing.. if the stack of reflex subs only produces as much SPL as a single properly powered TH118(will they even do that?) then is it even worth the cost/effort to bring them out.

[Art Welter]

1) If I haven't tried how can I say it won't work? At MOST, all I can say "it depends" or "maybe, but probably not." Right?
2)One question I have about the process is should I be limiting the range 'better' to the 'lessor' of the cabinets or let both run naturally?
For instance: hpf the TH118 @ 30 & hpf the 181 @ 40
OR
hpf both 118 & 181 to 40hz so as they match?
3)What about lpf? don't worry about it until aligning with tops?

1)Correct, though having tested the phase response of a number of tapped horns and bass reflex cabinets, I agree with Ivan "it doesn't have to be exact as there is a bit of "fudge room" down in the sub area."

Below is an example of a TH (my Keystone design, which happens to have very similar phase and frequency response to a DSL TH-118) and a bass reflex with a similar LF corner. Once the proper delays are set (the BR would need to be delayed approximately 10.58ms to match the TH longer path length time of flight) the TH and BR will phase/time align at the upper range.
There is a 120 degree phase difference at 100 Hz, 210 degree phase difference at 40 Hz, so best case 210-120=90 there will be still be a 90 degree phase difference at 40 Hz. 90 degrees is 1/4 wavelength, so the LF will still reinforce, not cancel.

2) Assuming the 181 Fb is above 40 Hz, a 24 dB per octave LR filter will reduce output below that frequency enough that any phase differences between the two cabinet types won't make a difference, you don't need to "throw away" the LF response of the TH-18.

3) The upper response of the cabinets probably can both be set near the same LPF frequency you normally would use, but their frequency response should be matched using both in and out of band parametric EQ, which will also help align the phase response.

Art

[Nathan Riddle]

So I'm not really sure what's up with the delay on the 181 or how to align everything.

I tried for a while and failed. I needed more time to experiment and didn't have it.

Though I thought it was pretty nice that the phases of all 3 pretty easily lined up. this is with 0ms dsp delay on the 181 or 118 and ~6.3ms on the tops.

[ProSoundWeb Community]