Active wall-speaker with 40 drivers and 32mm depth

[prxprx]

So I was doing my usual browsing around the web for some inspiration, when I came across a company called Concrete Audio.

They sell the F1, a 32mm deep wall-mounted, canvas size speaker. Active, with 41 very small (~32mm) drivers.



Here it's displayed in it's pure form, but they also sell.a version with a printed canvas look...

There is not much detail to find. It's active, and paired with a sub. It sells for a whopping 16.000 usd. (2.1 system)

I have not heard them, but I am intrigued by this design.

I was looking at doing something like this, with the Dayton Audio CE32A-4.

Active amps are present, right now a bit overkill. (Hypex Fusion FA123)

Is there a cheap way to do this? I think 'combing' (is that a word?) can be a BIG problem. But maybe this won't be too big of an issue because they are grouped together? Like the Hass effect says, if the other drivers get the sound to your ears, with a maximum time difference of 40ms, your brain will think it's coming from just one source.

That would mean that the 'sheet' with the 40 drivers needs to be pointed at the listener a bit and that means the cabinet needs to be deeper, which I don't really want... It would probably be the most easy and cheap way though.

How do you guys think the original handles this?

Love to hear your opinion and ideas!

[fpitas]

No idea if they do some kind of phasing on the drivers to minimize combing and beaming, but maybe not. Any big planar driver has the same problems, but some people are cool with it, even prefer it.

[jhollander]

There would definitely be some combing, beaming or off axis issues to deal with. I'd spend some time reading up on bessel arrays. By shading and reversing polarity of some drivers you can improve the off axis issues. Interesting project.

[prxprx]

No idea if they do some kind of phasing on the drivers to minimize combing and beaming, but maybe not. Any big planar driver has the same problems, but some people are cool with it, even prefer it.

Yeah, they might be focussed more on the practical side, but then again they cost 16k usd, so they probably should sound good too, lol. Bummer I don't know more about them.

There would definitely be some combing, beaming or off axis issues to deal with. I'd spend some time reading up on bessel arrays. By shading and reversing polarity of some drivers you can improve the off axis issues. Interesting project.

Bessel arrays sound very interesting. There is both a 4ohm and 8ohm version of the driver available, so there are options here. 5x5 bessel sounds pretty cool, but 40 or 50 drivers sounds even more interesting. (As a project)

Might also be able to use the Dayton Audio HARB252-8's. 12 per side ,align them in a circular pattern with a regular single tweeter in the middle. Probably way worse for combing, but would look good as a project and my active amps are 3way anyway.

[mattk]

I wonder if they are using individual amps per driver, with phasing and/or amplitude control.

[billfitzmaurice]

It's possible to eliminate the comb filtering by the use of a sophisticated filtering arrangement that low passes each vertical line of drivers where the CTC distance from each line is one wavelength or less from the central vertical line. There's nothing in their data, such as it is, to indicate that they do that. If they don't the polar response is going to be a mess.

[prxprx]

I wonder if they are using individual amps per driver, with phasing and/or amplitude control.

I think the R&D costs would be too high for such a limited production. I can't imagine that they sell a lot of these.

It's possible to eliminate the comb filtering by the use of a sophisticated filtering arrangement that low passes each vertical line of drivers where the CTC distance from each line is one wavelength or less from the central vertical line. There's nothing in their data, such as it is, to indicate that they do that. If they don't the polar response is going to be a mess.

That sounds a bit too complicated for me. Might be an option for a 'version 2' somewhere in the far future.

[billfitzmaurice]

It is hugely complicated, and even done right it's not going to work any better than, and probably not as well as, a far easier to construct lwo-way line array.

[prxprx]

Yeah, so as a V1 im either looking at a 5x5 bessel array, or maybe something like a 12x HARB252-8 per channel + tweeter. That combined with two small sealed subwoofers.

[jhollander]

Adding a tweeter is not a bad idea assuming you can get one with high enough sensitivity where you can use the gain from the multiple drivers. Many of the single driver projects suffer from directivity/ off axis issues due to the size of the driver.

[neildavis]

My guess is that the array uses electronic curvature, with "rings" of drivers forming a virtual sphere. It would probably use 5 channels of amplification, each with its own delay. That's easy to implement on a small board with DSP and the right amplifiers. The line array at this link does the same thing with a 22-channel amp that fits on a fairly small board. Because of the large number of motors and having a separate subwoofer, you don't need a much power for the array--a smallish 65W power supply would probably be enough for high volume levels..

But it's just a guess--can't find any detailed info on this thing.

[billfitzmaurice]

Adding a tweeter is not a bad idea ...

IME one tweeter used with a line of midbasses doesn't work nearly as well as a line of tweeters.

im either looking at a 5x5 bessel array, or maybe something like a 12x HARB252-8 per channel ...combined with two small sealed subwoofers.

That would result in high sensitivity arrays combined with low sensitivity subs. If anything it should be the other way around.

[jhollander]

Assuming we are talking about multiple vertical and horizontal drivers, with a small ish Bessel array a single tweeter could be beneficial in filling in the higher frequency dip due to the narrowing directivity of the larger drivers. I was assuming this speaker is creating some sort of wide band point source, a line array would be a different design imo.

[prxprx]

For the price they probably indeed have some kind of DSP and amplification per driver or at least per 'circle'

For a cheap DIY experiment I'm probably going to look more into a 5x5 Bessel Array, without an extra tweeter. The CE32's reach up quite high anyway, and with some DSP I can tweak it a bit more.

I agree that two small (Tang Band) sealed subwoofers aren't the perfect match. But for the purpose of the system (creating a big sound without showing) it might have to do for now, lol.

Now I 'only' need to find a way to wire the 5x5 grid up properly, while observing correct usage of 4 and 8 ohm units and their polarity. The ending resistance load for the amplifier should also stay around 4ohm if possible.

[scholl]

3 circles and a cross, must mean something. Maybe they figured out Stonehenge. Nothing could go wrong here.