more info on d'apolito needed

[blu_line]

Hello all,

I'd like to have some more (indepth) info on d'apolito configurations (and the relation to linkwitz), filters and such.

Can any one help ?

grtz

Simon

[bob4]

Hi,

check out this link: www.royaldevice.com

It's about the Audio room of some crazy Italian who built a huge bass horn beneath his floor. As Mid/ Hi horns, he uses d'Appolito's

I didn't look further for any info or links on the d'Appolitos, but perhaps you can find something.

greets,

bob

PS: try searching with Yahoo etc. , I got approx. 2500 hits, and the first two pages looked very promising.

[bob4]

Whoooooops,

I always thought it was a speaker- brand

I should probably get more info if I post on a subject I don't know too much about..........

But the Hi/Mid speakers used in that listening- room I posted the link of, are arranged according to this d'Appolito thing. TEll me if you find out more.

reagrds,
bob

[daatkins]

Here's a reply from the man himself (Joe D'App) to Andre Perreault (of e-speakers) who posted it to the Bass List three or four years ago....

"Andre,

I'm up to my behind in alligators right now. You're right, there is much bad folklore on the MTM configuration. People seem to forget that the basic reason for the MTM is to stabilize vertical polar response with respect to frequency. This is accomplished by the geometry alone, regardless of interdriver phase relationships, interdriver time delays due to lack of time alignment or crossover type.

Beyond that, you can examine via simulation, just about any crossover configuration you want. Different crossovers will yield different vertical polar patterns, but all patterns will stay centered on the central axis defined by the central driver, usually a tweeter. In-phase (even-order) crossovers will have off-axis nulls in the vertical direction. The depth of the null and its angular location are a function of the crossover frequency, the interdriver spacing and the crossover order. Laying MTMs on their side
for center channels as you see in so many home theater systems can lead to poor horizontal coverage with in-phase crossovers.

One of the popular myths is that one must use an odd-order crossover to get the benefits of MTM. Nothing could be farther from the truth. The off-axis null with in-phase crossovers is of great benefit in reducing floor and ceiling reflections. Odd-order crossovers have a 90 deg inter-driver phase shift at crossover and generally do not produce off-axis nulls with time aligned drivers. They are more sensitive to lack of time alignment, however, and may in this case also produce off-axis nulls.

My original paper on the MTM covered most of this in great detail, but few people bother to read it. I really don't have time now to say more on this topic. The short essay you suggest will have to wait till I get back from Greece in mid April."

Best regards,

Joe D'App"


I may have some more archived Bass Lists posts on the subject - I'll have a look.

Nice one,
David

[blu_line]

Is this from the march issue 1990 of speaker builder ?

I have requested the AES pre-print of Joe D'appolito.


grtz

Simon