The making of: The Two Towers (a 25 driver Full Range line array)

nc535

Member
2011-04-08 5:12 pm
NC
Questions for you guys that have built these line arrays. I'm considering a pair for use in my (new) open floor plan house that can be listened to from multiple places, sitting and standing. The listening distance will be great enough to mitigate comb filtering from a TC9 sized driver but I'm concerned about beaming at HF. How wide a sweet spot does one get with a TC9 sized array? Does it cover a 3 seat couch?

BTW alternate architecture is line of 1" full range drivers backed by woofer array, either coaxial or dual opposed on sides of cabinet but is 3x more expensive and more work.
Target 1" FR good down to 250 Hz so lots of freedom re' CTC.
 
:) indeed! I would have loved doing bass arrays too ;).

Though one of these subs has twice the volume displacement of one array. So this should help quite a bit. The arrays will still be played full range, I'll just use a little less boost EQ on the bottom end. Creating head-room is the primary idea. Plus the subs will most probably take over the left/right compensation I do in the bass department.

A point to ponder, provided to me by the designer of the Swarm bass system in some private communication is that systems comprising line arrays and point source subs can be adjusted to have the desired sub/array spl balance only at one particular distance, due to the differing attenuation rates of both. Not a problem if the system will be listened to at one distance. Closer than the calibrated distance will provide a bass-heavy balance; further will be bass light.

Maybe this doesn't matter. If it does you will need to make an array-height stack of subs. Then you won't have enough screws!

Just sayin'.
 
Questions for you guys that have built these line arrays. I'm considering a pair for use in my (new) open floor plan house that can be listened to from multiple places, sitting and standing. The listening distance will be great enough to mitigate comb filtering from a TC9 sized driver but I'm concerned about beaming at HF. How wide a sweet spot does one get with a TC9 sized array? Does it cover a 3 seat couch?

BTW alternate architecture is line of 1" full range drivers backed by woofer array, either coaxial or dual opposed on sides of cabinet but is 3x more expensive and more work.
Target 1" FR good down to 250 Hz so lots of freedom re' CTC.

A 3 seat couch has never been a problem in my house. It is why I picked the TC9. Even way off axis the results are better than I could hope for.

I'm hoping the guys who have heard my arrays (a growing number) will chime in too.

At an angle up to 15 degree off axis the output is still very similar to the on axis curve:
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(using the round-over outer baffle even helps there with even more bundling in the upper frequencies (around the 5 to 8-9 KHz spot), but I've lost some plots that show that, I can't do them with meaningful results with the arrays).

I use absorption at first reflection points to counter the more irregular room response that might come from the beaming character of a 3.5" driver. However even before placing damping panels I had quite an acceptable result. I just wanted to know how far I could go with this concept. That's an on-going journey as this thread has proven.
 

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A point to ponder, provided to me by the designer of the Swarm bass system in some private communication is that systems comprising line arrays and point source subs can be adjusted to have the desired sub/array spl balance only at one particular distance, due to the differing attenuation rates of both. Not a problem if the system will be listened to at one distance. Closer than the calibrated distance will provide a bass-heavy balance; further will be bass light.

Maybe this doesn't matter. If it does you will need to make an array-height stack of subs. Then you won't have enough screws!

Just sayin'.

I'm well aware of what I'll be facing, but don't see it as a big problem. As said, the arrays will continue as full range, I'm just adding extra power and volume displacement to the bottom end. So you could see it as 4 subs working together. Making the load on each one a little less. So while there will be a difference, it won't be much different from the bass level differences one gets when you move closer to a wall.
I measure just before my couch. Leaning back on the couch, one gets a higher level of bass than at that measurement spot. The beauty is in that it's virtually free of modes the room normally enforces. That can only get better with more subs to help out.

Your noted difference in point source/line source is very true, and the exact reason why I still want to have the arrays help out in that bottom end.

But I'll be (more than) doubling the volume displacement and power, which makes about a 6 dB gain in headroom entirely possible.
My main listening area is close enough to consider it similar in distance to get away with it. At 20 Hz, the subs will do most of the heavy lifting, that's what I keep calling the atmosphere generator. It is a "feel thing" but oh so much fun! Probably my biggest motivator to do this project. Even though the reduction in movement of those little cones could bring a surprise too, I'll just have to wait and see.

Outside the room, literary in the back yard, you hear midrange and bass leaking out, not just a few bass notes like my previous speaker would do.
Room nodes would let the bass stand out.

About bass arrays: if I could, I would!
 
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The second enclosure is moving along nicely. This one is a much faster process. I've ordered epoxy and paint to make it match the arrays. I'm a little scared on how to do the area around the logo, as part of the epoxy paint will be applied with a light micro balloon fill to get the same texture as on the arrays.
finaltexture.jpg


closeup.jpg


Not sure yet how to handle it properly, I kept the cut-outs from the laser cuts as I expect they will help out to keep the logo's clean and sharp looking.
 
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Great sub build so far wesayso! Been a while since I dropped in over here! :D

Can I ask if this is true regarding bass 'point source' versus bass 'line array'???

Given 40hz has a wavelength of 30ft, surely the two subs, and all the drivers in the array will be within the 1/4 wavelength rule and therefore will combine as a single entity?

Plus given you are pressurizing a relatively small enclosed space which will have room mode etc - this even more discounts this theory??

To be a 'point source' at the bass frequencies we are talking about surely only refers to outdoor huge venues where distances are measured in 100s of meters and therefore can become more relevant?!?
 
Possible very true points! Especially at these low frequencies, where even a line array can't begin to mimic a true infinite line array.

But it made me ponder not to cross over at a certain frequency, but to have all of them share the load. One of the things that keeps me hooked is the coherent sound of the arrays. I won't do anything to jeopardize that.
 
When you think about it - one of the best ways to get a really good bass response in a room is with spread out, different distance multiple subs.

They are usually all different distance to the LP, and there is no issue with 'differing attenuation rates' - I just do not believe this is an issue indoors (unless you listen to your speakers in an aircraft hanger maybe!!!)

Anyway - soon we will know - looking forward to your measurements, analysis and insights as always!
 

BYRTT

Member
2009-12-21 6:18 am
...But it made me ponder not to cross over at a certain frequency, but to have all of them share the load...

You told from the start and imagine this is the clever strategy and the point to keep the great sound coherence that it performs as is for now, where for example me and koldby reported there are not any signs that music lack into lows for these musical monsters.

Will see if i can find time model line array in VituixCAD because think it can also model those subs at same time, but time will go because of learning curve to new software and also it has tons of settings and possibilityes to dial on so its nots so easy without put alot of time into case.

...One of the things that keeps me hooked is the coherent sound of the arrays. I won't do anything to jeopardize that.

...:up:
 

nc535

Member
2011-04-08 5:12 pm
NC
You want as many sources as possible sharing the load than do multi sub optimization. Geddes says little gain in even-ness of bass sound field with more than 4 sources, which you will have. That isn't to say you shouldn't have a single pole high pass on the arrays at 30 or 40 Hz to give the lion's share of the load to subs at lower frequencies. At frequencies below the lowest room mode you shouldn't need multiple sources.

Is coherence at risk with subs? I don't think so. Certainly not if you put the subs close to the arrays. If you don't, than maybe there will be some compromise in evenness of the bass at the LPs in order to improve it elsewhere. But it all comes down to where you put the subs and how you tune them and how high you allow them to play. I don't think its coherence that gets compromised but the smoothness of the bass FR at one location vs others. Coherence isn't determined by the 20 Hz to 60 Hz band but by what goes on above that band.