Pros and cons of a cabinet with 6 woofers in a line array

[MMMarciNNN]

Since Sica 5.5 coaxials get a lot of praise on this forum, and since Sica produces almost identical visually 5.5 woofers I'd like to ask you if this kind of a 3-way active speaker has any sense. If we stack 6 woofers one on another and put the coax on top, tweeter will be at optimal listening height. First woofer should be as low as possible to couple acoustically the whole bass array with the floor (am I correct here?). Six 5.5 woofers have cone area that is an equivalent of a 13.5 inch woofer, but they will provide much better impulse response and will allow for a very narrow baffle. It won't be a cost effective solution, but maybe something for people who prefer narrow cabinets and minimalistic look. What are the main drawbacks of this concept? Here is a quick sketch and a photo of these drivers:

 

[MMMarciNNN]

No replies...
Bad idea?

Now I think it should rather be 3.5 or 4 way. Coaxial needs to be rolled-off quite high to remain minimal excursion of the cone, so woofer below him will have to play from around 600 Hz. Still 5 woofers remain for the lowest end..

 

[Devnull]

Off the top of my head
1. Limited Xmax and power handling
2. 6 5.5 woofers don't have the Sd of a 13.5, probably not even a 12
3. 5.5 inch drivers are at best a midwoofer

 

[JohnnyNG]

Not very helpful but that guy looks really worried. Maybe over his apparent recent weight loss.

 

[Duke]

There would be no radiation pattern mis-match in the horizontal plane, but there would be one in the vertical plane, which might be worth mitigating with a 3.5 way topology or shading or something like that.

Do the modelling and/or math to make sure the midwoofer array can meet your low-end SPL and extension targets.

I'm not a fan of ultra-narrow baffle speakers in general, but a lot of people are, and this looks to me like a good way to do it.

 

[MMMarciNNN]

Off the top of my head
1. Limited Xmax and power handling
2. 6 5.5 woofers don't have the Sd of a 13.5, probably not even a 12
3. 5.5 inch drivers are at best a midwoofer

So maybe instead of using only Sica drivers, 5 at the bottom could be high excursion woofers with similar diameter, like Dayton Epique E150HE-44? It won't be visually coherent anymore, but still very narrow baffle. After all Daytons can be covered with acoustic cloth with only Sicas visible.

 

[Yasuo]

What if you put a larger woofer on the side? Keep the box slim and tall just enough to allow you a proper woofer on the side. You still get keep the looks if aesthetics is your main goal.

 

[SigbergAudio]

Probably a good idea to simulate to see if the concept delivers the bass response (both capacity and extension) that you expect and want.

The 5.5" driver has a fs of 48hz and xmax of 4.5mm. Will probably be pretty punchy, but not really designed to do very deep bass.

 

[MMMarciNNN]

What if you put a larger woofer on the side? Keep the box slim and tall just enough to allow you a proper woofer on the side. You still get keep the looks if aesthetics is your main goal.

Long time ago I read about the benefits of line arrays and cylindrical waves, that's why I thought about giving it a try. I'll try to do some simualtions, but I have to learn how to do it first, heh.

 

[voodooless]

The thing is, you’re an actually making a hybrid of these two. This can probably work if you carefully design the radiation patterns to smoothly transition. The lower frequencies will always have a transition from forward to omi (bafflestep). This will actually make this effect less pronounced.

What you could try is move the coax one position down. That might benefit the radiation pattern in the transition zone.

 

[Duke]

Long time ago I read about the benefits of line arrays and cylindrical waves, that's why I thought about giving it a try. I'll try to do some simualtions, but I have to learn how to do it first, heh.
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Ime there is a drawback from combining a line array with a point source: SPL falls off differently from the two with distance, so you could easily end up with the tonal balance changing audibly as the listening distance changes.

But the lower the frequency and the shorter the line height, the less it actually behaves as a line source, and the less distance out to which it behaves as a line source.

I haven't done the math, but I think there's a good chance that, at normal listening distances, your stack of six 5" midwoofers won't approximate a true line source very well over the frequency region you would probably use it. And imo this would be good news, assuming you'd like for the tonal balance to be consistent as the listening distance varies.

Imo if you decide to do a line array, then do it all-out, tall as it can possibly be, as full-range as it can possibly be, and with the individual elements spaced as closely together as they can possibly be.

 

[JohnnyNG]

What if you put a larger woofer on the side? Keep the box slim and tall just enough to allow you a proper woofer on the side. You still get keep the looks if aesthetics is your main goal.

If aesthetics/slim profile is really the main priority I'd use a 5.5"mid above and below the coax with one or two real subs on the side(s). I'd only use toy subs in a really small speaker.