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Tekton Double Impact & Comb Filtering

Like many of you, I have been pondering purchasing these speakers but am very curious about the unusual tweeter array. I asked the smartest speaker person that I know (he is a student of Sean Olive) about the design and below is what he had to say.   

"In theory it could work, but the driver spacing means that the crossover point would need to be very low.
He is using the SB acoustics tweeter which is 72mm in diameter, center to center on the outside opposing drivers is around 5.7 inches, which is about 2400Hz. This means that combing would stop between 1/4 to 1/2 of the wavelength (between 1200-600Hz) is where the outside tweeters should start playing nice with each other.
Since he is not using low enough crossover points he has created a comb filtering monster. Now while it's not the great point source that was promised, it's no worse than most line arrays and the combing will average itself out given enough listening distance.

The MTM spacing on the other hand is ridiculous. Hopefully he is cutting the top end off on one of those midrange drivers to avoid combing."

seanheis1
Ag insider logo xs@2x
soundscience
16 posts
 
Hi Guys,

I would like to help clear the air on comb filter effects and line arrays.
The math that describes comb filters really comes from antenna theory and while speakers are acoustic antennas they don't behave the same as an antenna for radio waves.

In Leo Beranek's Text book for MIT on acoustics, he talks about how the air molecules between the drivers if they are close together vibrate in sympathy with the drivers. The consequence of this is that there really isn't any comb filtering at least on a vertical or horizontal line array if the drivers are close enough together.  

The first time I heard the Pipe Dreams at CES I knew something about the comb filter idea for line arrays was not right. 
I have built 2 different line array speakers and never got any comb filtering on either pair.  I didn't discover Beranek's book until after I built them but Beranek's explanation matches 


 
kdude66
1,200 posts
 
Soundscience,

Thank You for this good info,

Leo Beranek's Text book for MIT on acoustics, I have read bits of this book,I will take the time sometime and read all of it.


Kenny.
kdude66
1,200 posts
 
craigl59,

Very nice analogy of basic driver costs that effects the bottom line that all speaker designers and manufacturers must factor in.

Just for clarification for the other readers,I believe you told me that your room is very large and you enjoy large scale highly dynamic classical music and you listen at loud levels hence the spare drivers already purchased as backups just in case.

Kenny.
missioncoonery
1,223 posts
 

There is as  I understand a Double Impact "SE" version that uses all Scanspeak drivers in place of the standard drivers. This model is 6000.00 dollars so presumably the Scanspeak drivers are much more expensive,,,,


I didn't see this on the site but I would like to hear this setup

craigl59
307 posts
 
Kdude66:
Yes, you are right about the large room and classical feeds with dynamic changes that could generate very disruptive bursts.
As a classical musician, I sit in front of a large piano every day and once took the time to measure its decibel level. Loud passages are around 95 db at the keyboard side. But they do not sound as loud as 95 db of recorded music because there is no distortion/noise. As I know most of you recognize, the less noise in your system, the more you can listen to louder and louder feeds.
AND, Kdude, everyone should read your second post at the start of this thread. It is the clearest explanation I have seen yet explaining Eric's minimum mass theory. Congrats!
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