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Author Topic: Mains to sub alignment: further thoughts  (Read 5356 times)

Tom Reid

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Mains to sub alignment: further thoughts
« on: January 01, 2005, 03:37:49 pm »

Last year, I started a thread asking about "squashed cymbal" reproduction in the mains.

In the course of diagnostics, I was asked how I align mains to subs.  Andy was asking how I could have a smooth system, since I had a +3db bump in the crossover freq.  Started me thinking ...
and since I had the night off, I spent some time with my gear.

Rane has an alignment procedure that they describe in the manual with the AC22.  It was the basis for this experiment.

I set up the system like this.

SC mixer to DRPA to CE2000 bridged for lows, XS900 for highs in stereo.

CE2000 to EV Elim 18.  XS900 to MP415 on a stick.
Measurements taken outside 30' from any boundary.

Crossover set at 95Hz 24db LR.  EQ flat, Parametric flat, no compression, no limiters.

ECM8000 used for measurement mic, 3' from center of cabinets.

Bink audio CD used for input.  95Hz sent to mixer.  Gains set to hit at least +12 on crossover inputs.  

Low amp gained until I could measure 90db on output.  RTA/Mic senstivity set to read 0db.  Once 0db established, low amp shutoff (gain not touched).  High amp gained until same results are shown on RTA display.  Low amps turned on, delay adjusted until maximum gain obtained (I could just flicker the +3 light).

The delay reads out at 6.4 ms for the JBL MP415, 7.2x ms for the EV Elim 15.

Without using a computer and SMAART software and/or more pro tools, it seems like this is a good way to "eyeball" the delay compensation between a main cabinet and a subwoofer.

Is there something wrong in this procedure?

Sorry for all of the headaches waking up today.  I've paid my New Years dues years ago ...I try not to work New Years unless it's very lucrative and close to home.  
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Douglas R. Allen

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Re: Mains to sub alignment: further thoughts
« Reply #1 on: January 02, 2005, 07:25:04 am »

The delay reads out at 6.4 ms for the JBL MP415, 7.2x ms for the EV Elim 15.


This part I don't understand. There is no need to add delay to the subs if the tops are ahead in time. Adding delay to both tops and subs puts the tops
.8ms back from the subs. ( 7.2 minus 6.4 )Also "Perfect" alignment would show 6db boost at summed freq. Although less is the norm. If you add just .8 ms to the tops do you get the same results?

The down side to this is you don't know if you are aligning to the first cycle or 3 or 4 cycles in. I have seen ported subs with 16ms of group phase delay. 14 or so feet back from where they are is where they are really sitting in time.

I would just add delay to the tops.
Also make sure your mic is not 40 or so inches high when you do this. That is close to 1/4 wave length of 95 hz and will cause boundry cancelation with the bounce off the floor making it hard to get a good reading. Put the mic on the floor. With a long wave length of aprox 11 1/4 feet at 95 hz it will be better to do that.

Douglas R. Allen

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Allen Audio

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Douglas R. Allen

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Re: Mains to sub alignment: further thoughts
« Reply #2 on: January 02, 2005, 08:30:26 am »

Tom Reid wrote on Sat, 01 January 2005 15:37

Last year, I started a thread asking about "squashed cymbal" reproduction in the mains.

In the course of diagnostics, I was asked how I align mains to subs.  Andy was asking how I could have a smooth system, since I had a +3db bump in the crossover freq.  Started me thinking ...
and since I had the night off, I spent some time with my gear.

Rane has an alignment procedure that they describe in the manual with the AC22.  It was the basis for this experiment.

I set up the system like this.

SC mixer to DRPA to CE2000 bridged for lows, XS900 for highs in stereo.

CE2000 to EV Elim 18.  XS900 to MP415 on a stick.
Measurements taken outside 30' from any boundary.

Crossover set at 95Hz 24db LR.  EQ flat, Parametric flat, no compression, no limiters.

ECM8000 used for measurement mic, 3' from center of cabinets.

Bink audio CD used for input.  95Hz sent to mixer.  Gains set to hit at least +12 on crossover inputs.  

Low amp gained until I could measure 90db on output.  RTA/Mic senstivity set to read 0db.  Once 0db established, low amp shutoff (gain not touched).  High amp gained until same results are shown on RTA display.  Low amps turned on, delay adjusted until maximum gain obtained (I could just flicker the +3 light).

The delay reads out at 6.4 ms for the JBL MP415, 7.2x ms for the EV Elim 15.

Without using a computer and SMAART software and/or more pro tools, it seems like this is a good way to "eyeball" the delay compensation between a main cabinet and a subwoofer.

Is there something wrong in this procedure?

Sorry for all of the headaches waking up today.  I've paid my New Years dues years ago ...I try not to work New Years unless it's very lucrative and close to home.  



I may have goofed after rereading your post.
Do you have different tops that you use? EV 15's and Mp415's. Theses aligning with the EV18 subs? For some reason I was thinking the MP415's were subs. My goof.

( The delay reads out at 6.4 ms for the JBL MP415, 7.2x ms for the EV Elim 15. )

If the EV Elim 15 is a typo then your subs would need.8ms to get in alignment with your tops. Or are you using MP415's sometimes with ev18's and Ev elim 15's with the Ev18 subs other times?

Thanks
Douglas R. Allen
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Tom Reid

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Re: Mains to sub alignment: further thoughts
« Reply #3 on: January 02, 2005, 12:42:46 pm »

Hi Douglas.

I'm in Portage Indiana. About 38 miles east of Chicago.

In answer to your other question, I have 2 sets of tops, MP415, and EV Elim 15.  I run them with the EV Elim 18 subs.

Thanks for the tip of putting the mic on the ground.

I had also thought about measuring the response out at a true wavelength of 95hz, but annoying the neighbors with low freq sine waves is the problem there.  Maybe I can get down to a cornfield an do this again when the weather breaks.

Yeah, I thought 6db is the theoretical max for 2 drivers coupling at the same freq.  I could never get more then 3db gain.  But that's probably due to low freq wave, measurment mic, mic placement, and a tons of other things.

Sorry for the confusion.  I did the Syn-Aud-Con, Crown TEF school stuff in the 70's.  Left the industry after the third kid to do programming, and now I just enjoy the hobby (it does help lower my blood pressure ...and the workout is great).






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Mike McNany

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Re: Mains to sub alignment: further thoughts
« Reply #4 on: January 02, 2005, 02:22:24 pm »

What I missed was, were you delaying the tops or the subs? I reread the posts a couple times and didn't see it.

I'm just getting into experimenting using speaker delays for alignment. I'll check that Rane manual procedure out.

I had a chance before NYE gig to set up my system using the speaker maker's speaker controller crossover & delay settings (sans controller) and it seemed to make a subtle improvement. But the speaker controller has a fixed delay on or off so the recommended crossover point is affected by that, I'm sure. So it may not be the true optimum due to fixed options.

Thanks,
Mike McNany
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Tom Reid

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Re: Mains to sub alignment: further thoughts
« Reply #5 on: January 02, 2005, 02:46:28 pm »

Boomerweps wrote on Sun, 02 January 2005 13:22

What I missed was, were you delaying the tops or the subs? I reread the posts a couple times and didn't see it.

I'm just getting into experimenting using speaker delays for alignment. I'll check that Rane manual procedure out.

I had a chance before NYE gig to set up my system using the speaker maker's speaker controller crossover & delay settings (sans controller) and it seemed to make a subtle improvement. But the speaker controller has a fixed delay on or off so the recommended crossover point is affected by that, I'm sure. So it may not be the true optimum due to fixed options.

Thanks,
Mike McNany

Yeah I see what you mean.  It seems I write in a confusing manner.

All subs exhibit some natural delay in a specific frequency range due to cabinet design ...in my experience.  Given that, I would be dealying mains to match the subs' place in time.

When I go 3 way, the problem will compound itself again, since bypassing passive crossovers will cancel out any adjustment the crossovers are doing to the mid to high alignment.  Not to mention CD EQ.

But hey, this is much more rewarding then stamp collecting (and cost about the same).  
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Don Boomer

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Re: Mains to sub alignment: further thoughts
« Reply #6 on: January 03, 2005, 01:10:43 am »

Tom Reid wrote on Sat, 01 January 2005 12:37



Low amp gained until I could measure 90db on output.  RTA/Mic senstivity set to read 0db.  Once 0db established, low amp shutoff (gain not touched).  High amp gained until same results are shown on RTA display.  Low amps turned on, delay adjusted until maximum gain obtained (I could just flicker the +3 light).




I would think it might be easier if you did the same setup but flip the polarity of one of the speakers and adjust the delay for maximum attenuation (assuming your speakers were actually IN phase at that frequency point when you started)
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Don Boomer
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Re: Mains to sub alignment: further thoughts
« Reply #6 on: January 03, 2005, 01:10:43 am »


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