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-   -   Acoustic Horn Design The Easy Way (Ath4) (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4.html)

mark100 3rd February 2020 02:27 PM

Quote:

Originally Posted by mabat (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post6069568.html#post6069568)
It has been some time since I looked into that but I just don't like the idea of an abrupt phase change around the crossover frequency off-axis. Or, how would you avoid that, provided the distances to the individual drivers change with angle, as they typically do?

Hi mabat, for sure.. when distances to the individual drivers change with angle, there have to be different summations thru the xover region from relative phase shifts.

i just keep measuring that minimizing the frequency range (width) of the xover region using high orders, minimizes the frequency range of difficulty...

and as to the issue of abrupt phase change around xover, that's what the linear phase xovers solve.
There aren't any abrupt changes, as phase stays flat for both drivers throughout summation (or at least to least to minus 30-40 dB contribution points)

So with xovers that are both both steep and linear phase, the off axis summation issues distill down to geometry alone (geometry being of course inescapable).

But at least the problem frequency range is minimized via steep, and the difficult to sum abrupt phase changes are eliminated via linear.

jcga 3rd February 2020 03:33 PM

Hi Mark100,
I'm following this very interesting thread and when you write that with linear phase xover, you don't have phase change at Fc, what about "off axis" at Fc ?

mark100 3rd February 2020 05:55 PM

Hi Jcga, i've been talking about phase change at and around xover frequency, in the context that steep slope IIR xovers are fickle to adjust on and off axis.... that phase differences get amplified due to steep phase curves...like mabat said.

So linear phase xovers are to avoid that problem...haven't mentioned or considered anything going on at Fc... hopefully not a crossover :)

mabat 4th February 2020 08:12 AM

Quote:

Originally Posted by mark100 (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post6069752.html#post6069752)
Hi mabat, for sure.. when distances to the individual drivers change with angle, there have to be different summations thru the xover region from relative phase shifts.

i just keep measuring that minimizing the frequency range (width) of the xover region using high orders, minimizes the frequency range of difficulty...

What I meant is that there are different delays for sound paths below and above the crossover region - the distances to drivers in general change with angle off axis. The narrower this region is (imagine an extreme situation), the more abrupt the change will be (group delay will jump up) - at least in my book. I can't see how it could be otherwise - this can't be compensated because of the changing delay.

Maybe it is not so bad in practice but this thought lead me to this position. I have never actually tried, I must confess.

Anyway, we are quite off topic here I guess.

mark100 4th February 2020 10:04 PM

Cool Mabat, i still don't really get what you're saying, but like you also say, it's drifted off topic....which has been a most excellent thread indeed ...and is indeed yours :)

camplo 5th February 2020 12:02 AM

Quote:

Originally Posted by gedlee (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post6066538.html#post6066538)
I agree, I think very steep crossovers are a bad idea. My system was 3rd order LP and first order HP....

Hi Gedlee... all the studio monitors seem to favor steep crossovers, not saying much, but, I thought the idea the less interaction between the speakers the less issues caused by the interaction at crossover. Though steeper crossovers have a downside I thought it was a trade for the greater good? With a shallow slope, much more sharing of the bandwidth, how does one deal with the issues this causes?

gedlee 5th February 2020 12:25 AM

This thread is not about crossovers. It's an interesting subject, but not here.

camplo 5th February 2020 12:31 AM

OK, I missed some of what was said above! My apologies.

mabat 5th February 2020 06:37 AM

On the other hand, why not devote a few pages to crossovers, which are always an integral part of what we do. I'd also love to learn something new from those more experienced. Please continue.

Ro808 5th February 2020 05:17 PM

1 Attachment(s)
Quote:

Originally Posted by mabat (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post6066977.html#post6066977)
OT - any experience with Precision Devices CD1.5NR1 anyone? How bad is the breakup?


Judging by the hard suspension, it's unlikely to behave any better than the MOR compression driver in this respect.
However, the breakup of the rear covers appears to be problematic :rolleyes:


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