Double Bass Array (DBA)

[StigErik]

I'd like to start a new thread about this and show my own results with it. The DBA concept was described more than 20 years ago, and there's even a short Wikipedia article about it here:

Double bass array - Wikipedia

en.wikipedia.org

The idea is to create a plane wave from the front end of the room by using an array of subwoofers. This array must consist of at least four subwoofers. The plane wave created by the array will cancel out standing wave modes in the width and height of the room. To cancel the remaining modes in the length axis of the room, there is an array at the rear end of the room where the signal must be inverted, delayed and attenuated.

It's also possible to use passive absorption at the rear end. This is called a Single Bass Array (SBA). I've heard an SBA, but not measured it. It seems to have most of the benefits of a DBA.

My room is 5 by 7 meters. I have a cathedral ceiling with an average height of 3 meters.

The front and rear arrays are of course identical, and consists of twelve Seas L26ROY subwoofers in 35 liter closed boxes. The layout is like this:

Measurements will follow.

 

[ppataki]

VERY impressive, congratulations!
Would be great to see some pictures too later on
What electronics (DAC, amp, etc.) are you planning to use?

 

[voodooless]

That is one (or two) hell(s) of (a) massive array(s)

Would be cool if you could enable/disable them individually to see how few you actually need to still get good performance.

 

[StigErik]

I have measured six of the subwoofers in the front array individually. These are labeled A1, A2, B1, B2, C1, C2 as shown on the diagram in the first post here. All measurements are done in my main listening position. As the measurements show, there are very large differences in the response from these six different subwoofers. I would also like to conclude that below the 2nd standing wave mode on the length axis (~50 Hz), the response is mainly determined by the location of the measurement position. Above, the location of the subwoofers also starts to affect the response. The large dip around 33 Hz is caused by the 1st standing wave mode in the width axis of the room, and the listening position is of course in the null of this mode.

First an overlay of the six frequency responses:

 

[StigErik]

Frequency response and waterfall for each of the six are attached here.

 

[StigErik]

The entire front array.

And the rear array

 

[StigErik]

An now... combine the front and rear arrays, with the rear array attenuated, delayed and inverted. A lot better, but still not perfect.

 

[StigErik]

And the final result, with some EQ here and there.

 

[LIΟN]

So impressive!

 

[StigErik]

As you can see from my measurement, the decay is very short and clean, even with no low-frequency absorption in the room. This is the most interesting feature of a well-tuned DBA in my opinion.

 

[LIΟN]

As you can see from my measurement, the decay is very short and clean, even with no low-frequency absorption in the room. This is the most interesting feature of a well-tuned DBA in my opinion.

Good!
Can you show your few more? (ExcessGroupDelay tab, Decay tab, ExcessPhase Tab)

 

[theREALdotnet]

Impressive result, do you have a picture of the arrays?

 

[StigErik]

 

[StigErik]

 

[voodooless]

Distortion would also be fun! Should be extremely low, given that the drivers by themselves are already excellent, in an array will be even better!

 

[StigErik]

VERY impressive, congratulations!
Would be great to see some pictures too later on
What electronics (DAC, amp, etc.) are you planning to use?

Amps:
Front array is driven by three ICEpower 2000AS/2. Two L26ROY on each amp channel
Front array is driven by two ICEpower 1200AS/2. Three L26ROY on each amp channel

DSP:
MiniDSP Flex
Using the analog input

Bass management is done in my Anthem AVM70 surround processor, with 80 Hz crossover for all speaker channels, and 120 Hz filter for LFE.

 

[StigErik]

Distortion would also be fun! Should be extremely low, given that the drivers by themselves are already excellent, in an array will be even better!

Sure

At three different SPLs

 

[voodooless]

below 1% > 100 dB. That is crazy

 

[LIΟN]

It looks almost like a linear phase. Nice can imagine your sound. Your efforts are shown as they are.

 

[Keith_W]

I have never seen a spectrogram like that before! Amazing!