Why aren't D'Appolito arrays more common?

[Sparky]

Wait, what? When they are in the kitchen, where are you sitting? It's true that some speakers* sound really open-but truly the same would seem to defy physics. Unless you're sitting right in front of them in the kitchen; in that case sure.

*(Wharfedale's Linton Heritage and Diamond 11.2, both sounded really nice throughout Audio Element's shop, unlike the EVO 4.4 which had a narrow sweet spot).

Hehehe. I mean when walking around the house. I could be stood in the kitchen and I hear no loss of detail at all. I think that's the benefit of a soft dome tweeter as opposed to a Ray gun RAAL tweeter...?

 

[Sparky]

I remember that! Probably have it in my garage still; I was just starting to build speakers as a pre-teen out of envy of a friend who'd gotten connected to a golf caddy job and was making $$$$ and bought an awesome stereo. But y'all gotta understand, in those days truly good loudspeaker simulation was limited to exotic companies like KEF, B&W, and so on. So at that time, "rules of thumb" and ideas like the D'Appolito array were a kind of bridge for hobbyists and smaller companies try to do something good with limited resources. Once you get into the 90s and LEAP, MLSSA, LMS, and then later stuff it became a lot easier to do basic design work and spend more time on details. When I read LEAP could import real frequency and impedance data, including phase, and do a hard number crunch crossover simulation, I danced for joy and sang hallelujah!

I worked more in automotive, but I presume that all these towers from intelligent brands like Revel can direct nulls away from the listener without needing a D'Appolito setup and its negatives as already mentioned.

I'm 42 and have only just gotten into this rather expensive hobby. I find myself obsessing over things like frequency response and tweeter height etc etc. I wish I had got into it when I was younger like you did as I feel I've missed out on the all the fun of it before measurements and hard core data became the most important factor.

I'm a big fan of Revel. You don't see them much over here. I love reading the research papers. The reviews on here are really favourable.

 

[Mashcky]

This thread is very informative but I’m still wondering a few things about MTMs.

First, why don’t we see many (any?) MTMs with much smaller mid ranges in the 3-3.5” range, or even smaller dome mids, where the driver spacing can be kept to maybe 6” and therefore allow for normal tweeter crossover frequency? I was recently thinking about such a design using two “full range” drivers as mids to help compensate for their low sensitivity and therefore save money even compared to just one, higher end mid range driver.

I’m also curious why three-way MTM speakers often have WMTMW configurations rather than MTMW. It’s my understanding that woofer spacing shouldn’t matter much due to the long wavelengths, so why bother with such tall designs? The three-way Neumann monitor Amir reviewed has fine polars as far as I can tell – what’s stopping an MTM from even a side-woofer configuration when regular MTs get away with it?

 

[radio3]

Imo the most pattern-correct version of the MTM would be an MHM: Rectangular horn in the middle, perhaps with a radiation pattern of something like 90 x 40 degrees, crossed over where the woofers' pattern approximately matches.

That was what the JBL SVA1600 I mentioned above that blew my and all my friends’ minds was.

 

[BenB]

This thread is very informative but I’m still wondering a few things about MTMs.

First, why don’t we see many (any?) MTMs with much smaller mid ranges in the 3-3.5” range, or even smaller dome mids, where the driver spacing can be kept to maybe 6” and therefore allow for normal tweeter crossover frequency? I was recently thinking about such a design using two “full range” drivers as mids to help compensate for their low sensitivity and therefore save money even compared to just one, higher end mid range driver.

I use small mid/full range drivers in my WMTMW designs. The small mids let me pack things in closer vertically, and have nice (wide) horizontal dispersion over their operating frequency. I posted about a design using the TC9FD18 full range as the mid in a WWMTMWW configuration here:

http://techtalk.parts-express.com/f...owers-nested-array-speakers-in-denovo-cabinet

I’m also curious why three-way MTM speakers often have WMTMW configurations rather than MTMW. It’s my understanding that woofer spacing shouldn’t matter much due to the long wavelengths, so why bother with such tall designs? The three-way Neumann monitor Amir reviewed has fine polars as far as I can tell – what’s stopping an MTM from even a side-woofer configuration when regular MTs get away with it?

The BMR tower is going to be an MTMW design. You can see a couple of renderings and discussion here:
https://forums.audioholics.com/forums/threads/the-philharmonic-audio-bmr-refreshed.119407/page-5

 

[kniff]

Thought i'd chime in and say that there are still a few modern designs still available for sale. I for one am very happy with my MTM front consisting of XTZ Cinema M8 Towers + Center

I'm just an amateur so couldn't say if it's because of the MTM design or not.. but it's the best sounding setup i've owned or listened to! That might tell more about my credentials than the speakers however..

 

[sarumbear]

Thought i'd chime in and say that there are still a few modern designs still available for sale. I for one am very happy with my MTM front consisting of XTZ Cinema M8 Towers + Center

I'm just an amateur so couldn't say if it's because of the MTM design or not.. but it's the best sounding setup i've owned or listened to! That might tell more about my credentials than the speakers however..

How does those six tweeters work?

 

[GimeDsp]

How does those six tweeters work?

Like 1 tweeter but 6 times better!

Haha, i wonder same thing. I know such designs have got THX ultra certification so they must be decent.

 

[NiagaraPete]

Thought i'd chime in and say that there are still a few modern designs still available for sale. I for one am very happy with my MTM front consisting of XTZ Cinema M8 Towers + Center

I'm just an amateur so couldn't say if it's because of the MTM design or not.. but it's the best sounding setup i've owned or listened to! That might tell more about my credentials than the speakers however..

F... that is a nice room.

 

[nahuel]

What about Eve Audio sc305/307, Adam a77x or Focal Twin6?

I use sc307s, they are pretty flat. Eve makes closed subs, I believe those are great too.

 

[NiagaraPete]

I'm not sure if these qualify but Linn Ninka’s have a similar design. Mine are driven actively which makes a 3 way type.

 

[sarumbear]

Like 1 tweeter but 6 times better!

Haha, i wonder same thing. I know such designs have got THX ultra certification so they must be decent.

It is proven that unless there’s some clever math is used like in CBT, multiple tweeters will create lots of beams and major dispersion issues. That’s why I wanted to know. Clever or wishful thinking?

 

[GimeDsp]

It is proven that unless there’s some clever math is used like in CBT, multiple tweeters will create lots of beams and major dispersion issues. That’s why I wanted to know. Clever or wishful thinking?

I wondered the same thing.
Here is what THX claims to test
https://www.thx.com/product/thx-certified-loudspeakers/

MnK use a line array type deal
https://mksound.com/products/pro-series/mps2520p/

AH!, lol, it was the XTZ I saw on THX list a long time ago.
XTZ Cinema M6 compact speaker - XTZ Sound in Balance

Always, I have heard many THX verified MTM type system and own one and have never been disappointed with the results.

 

[sarumbear]

I wondered the same thing.
XTZ Cinema M6 compact speaker - XTZ Sound in Balance

For the Cinema M6, we developed a Quattro tweeter arrangement to provide a very high maximum sound pressure level, high efficiency and minimal distortion. In addition, a perfectly even dispersion pattern is achieved for several listeners by using a controlled bundling of drivers that minimize the negative influences of the room.

if anyone understood this please explain to me. Another of their models have even six tweeters!

To achieve optimum bundling for home cinema sound in the lower mid-range, the two mid-bass drivers are arranged according to the D'Appolito principle. Thus, the M6 sounds crystal clear, yielding great precision and extremely high dynamics.

As it was discussed on this threat at length, D’Appolito layout requires the low frequency drivers much nearer to each other.

I’m glad that you are happy but as speaker designer and engineer in related disciplines I see clear issues in those speakers. However, I’m happy to proven wrong by hearing the science behind them.

 

[GimeDsp]

if anyone understood this please explain to me. Another of their models have even six tweeters!

As it was discussed on this threat at length, D’Appolito layout requires the low frequency drivers much nearer to each other.

I’m glad that you are happy but as speaker designer and engineer in related disciplines I see clear issues in those speakers. However, I’m happy to proven wrong by hearing the science behind them.

They say "This makes it possible for the tweeters to go all the way down to an impressive 1.2 KHz which completely removes the phase problem most speakers have in the sensitive hearing range"

I am not sure about the math but I do know the lower you can get the tweeter to cross at the wider apart the woofer and be in such a design.

Also from what I have read getting the woofers close together is most important for a center channel where more sweet spot sweats are needed. In the vertical it's not as important for seated listening. This is way some manufactures make nested MTM, like what I have in one system.

I am not sure why they list it as a 2.5 way system or why they list "1.2 kHz, 3 kHz" as the crossover frequencies.
It's possible one 1 tweeter plays all the way up high and the rest come in only at 3k, this could minimize comb filtering, etc.

Either way they look cool.

 

[sarumbear]

It's possible one 1 tweeter plays all the way up high and the rest come in only at 3k, this could minimize comb filtering, etc.

Either way they look cool.

Everything is possible but on 4 Twitter model this means that the tweeter is not equal distance from the woofers. Reading further to their blurb it looks more and more of wishful thinking and complete ignorance of physical realities. The single vs two tweeter chart is hilarious.

 

[GimeDsp]

Everything is possible but on 4 Twitter model this means that the tweeter is not equal distance from the woofers. Reading further to their blurb it looks more and more of wishful thinking and complete ignorance of physical realities. The single vs two tweeter chart is hilarious.

What chart, I missed it.

 

[sarumbear]

What chart, I missed it.

Here is the screen grab and the page link.

https://www.xtzsound.eu/product/cinema-m6

Anyone knows at least a modicum of how line arrays work will laugh at these plots.

Meanwhile, have you wondered why other than in PA there are no speaker systems on the market which have more than one tweeter? (Unless they are in very large numbers and forms a CBT or Bessel array). If the manufacturer's "Quattro" array is their invention and we don't yet know how it operates I expected a patent or at least a paper reference. There is none.

Obviously they sound well as there are people testifying it, but why use smoke & mirrors? Why lower yourself to uneducated level?

 

[Ericglo]

Anyone knows at least a modicum of how line arrays work will laugh at these plots.

Meanwhile, have you wondered why other than in PA there are no speaker systems on the market which have more than one tweeter? (Unless they are in very large numbers and forms a CBT or Bessel array). If the manufacturer's "Quattro" array is their invention and we don't yet know how it operates I expected a patent or at least a paper reference. There is none.

Obviously they sound well as there are people testifying it, but why use smoke & mirrors? Why lower yourself to uneducated level?

What about Tekton? I have asked about their multi-tweeter speakers and never received an adequate reply.

 

[sarumbear]

What about Tekton? I have asked about their multi-tweeter speakers and never received an adequate reply.

This.is.hilarious! It trumps every wishful thinking design I’ve ever seen. It will go pretty loud though…

https://tektondesign.com/product/full-range-speakers/flagship/ulfberht/#color