Open Baffle Line Array in progress

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#21
A note on comb filtering

I have played around with a number of short arrays (column speakers) which are supposed to comb filter worse than longer arrays.

When I used fairly decent small PA drivers (4 X PA-130's) on my latest columns, they sounded great to me.

They are XO'ed at ~ 1,700 Hz BW3 electrical to some pro horn loaded compression drivers.
I am using a DEQ 2496 to EQ and a DCX 2496 to XO to the 12" woofers and subs.

However, even though they sound great to me with very high SPL's, low distortion and high efficiency (96 db 1W/1M) and when eq'ed to my taste,
my daughter comes over and says "how can you stand all that "swish-swish".

So she inadvertently, without knowing any of the jargon hit the nail on the head about comb filtering.
My point is, they sound perfectly fine to me.

I have heard from a number of people who built various length arrays say "don't worry about comb filtering, it is no big deal".
For whatever reason, I tend to agree.

I built these columns firstly for my Synth sound system, but it sits in storage being used as rear speakers in a home theater stand-in.

I have 12" SEOS as fronts.

Take it any way you want, I'm sure that all the lobing and high freq. loss can be measured, but my ear doesn't care.

One persons opinion,
Dave

A final note: Efficiency, I am using a 40W/Channel amp for the columns, a Cervin Vega CV-900 (420 W/channel) for the woofers and a Crown xti-1002 with 0ver 400 W/channel capability into my Lab-12 based subs, and the 40 W driven columns will walk away from everything else SPL wise.
 
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#22
Rick Craig said:
What I meant is that you can measure one array on-axis but be sure to do it at a distance similar to your listening distance. If you measure too close it will skew the results due to proximity effect. Once you get it dialed in then you can fine tune at the listening position.

I would avoid a simple 12db slope on the planars because it will limit your headroom. A simple 2nd/3rd harmonic distortion test will help if you can do that. I would also do driver correction with EQ applied while measuring the separate lines before you do any auto EQ with REW.
Click to expand...

Thanks for the recommendations. I have been measuring about 1 meter in front of the baffle and making changes based on that. I can see I need to do it as you described and it does make much more sense to do it that way.

Shadydave said:
I have played around with a number of short arrays (column speakers) which are supposed to comb filter worse than longer arrays.

When I used fairly decent small PA drivers (4 X PA-130's) on my latest columns, they sounded great to me.

They are XO'ed at ~ 1,700 Hz BW3 electrical to some pro horn loaded compression drivers.
I am using a DEQ 2496 to EQ and a DCX 2496 to XO to the 12" woofers and subs.

However, even though they sound great to me with very high SPL's, low distortion and high efficiency (96 db 1W/1M) and when eq'ed to my taste,
my daughter comes over and says "how can you stand all that "swish-swish".

So she inadvertently, without knowing any of the jargon hit the nail on the head about comb filtering.
My point is, they sound perfectly fine to me.

I have heard from a number of people who built various length arrays say "don't worry about comb filtering, it is no big deal".
For whatever reason, I tend to agree.

I built these columns firstly for my Synth sound system, but it sits in storage being used as rear speakers in a home theater stand-in.

I have 12" SEOS as fronts.

Take it any way you want, I'm sure that all the lobing and high freq. loss can be measured, but my ear doesn't care.

One persons opinion,
Dave

A final note: Efficiency, I am using a 40W/Channel amp for the columns, a Cervin Vega CV-900 (420 W/channel) for the woofers and a Crown xti-1002 with 0ver 400 W/channel capability into my Lab-12 based subs, and the 40 W driven columns will walk away from everything else SPL wise.
Click to expand...

I agree with your observations Dave. I could hear the "swish swish" when I had my 6 1/2" drivers incorrectly crossed at 3200Hz and could hear changes when I moved my head around as well. Now that they are crossed at 2200Hz I can no longer detect any of that combing "swish". Also, moving my head around I don't detect any change in the sound. Standing, sitting or tilting presents no discernible anomalies

I too have been told by others not to be too concerned about combing in a long line array. I agree with that to a point. Combing for sure is not a show stopper at least not until it's extreme enough to be heard by the listener.
 
#23
As much as it pains me to say, women have better hearing than men... I used to make changes on my speaker designs and then have the wife come listen.. She didn't know any of the HiFi jargon but always nailed the description.. And sadly she was usually right..
 
#24
Rob41 said:
Thanks for the recommendations. I have been measuring about 1 meter in front of the baffle and making changes based on that. I can see I need to do it as you described and it does make much more sense to do it that way.



I agree with your observations Dave. I could hear the "swish swish" when I had my 6 1/2" drivers incorrectly crossed at 3200Hz and could hear changes when I moved my head around as well. Now that they are crossed at 2200Hz I can no longer detect any of that combing "swish". Also, moving my head around I don't detect any change in the sound. Standing, sitting or tilting presents no discernible anomalies

I too have been told by others not to be too concerned about combing in a long line array. I agree with that to a point. Combing for sure is not a show stopper at least not until it's extreme enough to be heard by the listener.
Click to expand...

You'll get much better results if you move back from 1M. A straight un-shaded array will have some response changes versus distance so the closer you can measure to your listening position the better. The higher order slopes also minimize the comb filtering on the woofers. If you optimize from the center of the array it's good to go back and take measurements within a 20 degree vertical window. That way you can look for general trends to see if some EQ adjustment is needed. The planars will start to have peaks and dips at a fairly low frequency, not far above your 2.2K crossover.
 
#26
Finally completed

Yesterday I finally got the bases done so my OBLA-33 speakers are finished. At least as far as the build goes. I've got the specs roughed in at 65Hz and 2200Hz but I'm sure there is a bit more tweaking to do. Aside from some finish issues which I'll redo later, I'm very happy with how they turned out.

I was expecting a deep and wide sound stage and they didn't disappoint. What I wasn't expecting was the magnitude of the presence. It might sound cliche', but it's as if the band is right in the room with me.

Anyway, I thought you guys might like to see how they turned out so here are a couple pics.



 
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#28
Thank you. I will kepp playing with the settings and try it lower. My only concern is when I'm not playing at my usual levels of about 75-80db I could cause damage to them and 18 of them are almost a grand. I will try it though.
 
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