This is the conventional way to close in on the constraints and formulate initial compromises. The plot acts only as a guide and what's important is that it's taken in the context of all other relevant limitations.
There is a certiain madness that overtakes commercial center speaker makers too. 😆
Basically MTM has been and always been
a waste of time.
No benefit.
Far as using 2x woofers
always fun.
Spreading out center to center
otherwise is a waste of time.
solves the center channel issue instantly
having mid and tweeter closer to ear level.
and completely remove the higher mounted woofer
for MTM and put it down low where it belongs
with less center to center speaker spacing.
centers usually speech.
didn't know their is anything useful below 80hz
in a center channel.
a waste of time.
No benefit.
Far as using 2x woofers
always fun.
Spreading out center to center
otherwise is a waste of time.
solves the center channel issue instantly
having mid and tweeter closer to ear level.
and completely remove the higher mounted woofer
for MTM and put it down low where it belongs
with less center to center speaker spacing.
centers usually speech.
didn't know their is anything useful below 80hz
in a center channel.
^ your opinion mtm have no benefits.
In practice some of the best loudspeaker i've heard were MTM with 2x15"+ CD horn loaded ( Kinoshita RM 7 and variant). Tannoy Dreadnough or Buckingham were previous example pointing toward MTM with coax in place of T ( Dreadnough i've seen were oriented MTM ).
None of them have been considered as waste of anything by people who heard them.
Maybe you could discuss the pro and cons of MTM (because there is like in any design choice) rather than giving an opinion, it would be much more interesting no?
Aside: wasn't Diyaudio a place where 'fanatics' could express their wet dreams without being shoot in flame by 'les gardiens du bon gout' -'the good taste' keepers?
Come on guys, once someone have been warned about possible issue and decide to still pursue on his way either be supportive/constructive in your intervention either restrain from posting.
In practice some of the best loudspeaker i've heard were MTM with 2x15"+ CD horn loaded ( Kinoshita RM 7 and variant). Tannoy Dreadnough or Buckingham were previous example pointing toward MTM with coax in place of T ( Dreadnough i've seen were oriented MTM ).
None of them have been considered as waste of anything by people who heard them.
Maybe you could discuss the pro and cons of MTM (because there is like in any design choice) rather than giving an opinion, it would be much more interesting no?
Aside: wasn't Diyaudio a place where 'fanatics' could express their wet dreams without being shoot in flame by 'les gardiens du bon gout' -'the good taste' keepers?
Come on guys, once someone have been warned about possible issue and decide to still pursue on his way either be supportive/constructive in your intervention either restrain from posting.
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already stated
pros= none.
cons= center to center spacing to far
it is that simple.
and will always be that simple.
low enough crossover might fix it.
who cares. bass that low easy.
Directionality is not difficult down low.
Which is exactly again already covered.
Center channel not below 80Hz
Sub does that.
Sorry the design is dismissed that easy.
Im not attached to it in any way.
so giving quick answers is easy for me.
your likely to put your mid or coaxial
dead in the center of the baffle.
So it " looks" right.
So again udder basic baffle diffraction/response
dead in middle is guarantee worst non flat response.
not my fault. it just works, the way it does.
pros= none.
cons= center to center spacing to far
it is that simple.
and will always be that simple.
low enough crossover might fix it.
who cares. bass that low easy.
Directionality is not difficult down low.
Which is exactly again already covered.
Center channel not below 80Hz
Sub does that.
Sorry the design is dismissed that easy.
Im not attached to it in any way.
so giving quick answers is easy for me.
your likely to put your mid or coaxial
dead in the center of the baffle.
So it " looks" right.
So again udder basic baffle diffraction/response
dead in middle is guarantee worst non flat response.
not my fault. it just works, the way it does.
Lol.
Ok biased opinion. It's obvious.
Of course there is pro like the fact it help to reduce floor/ceiling bounce in particular with large driver like 15". The fact it mimics coaxial behavior is another pro, not even talking about the fact // drivers offer higher sensitivity and power admissible... but when your biased...
Maybe study why Kinoshita, Auspurger or the 'big' Jbl from 80's/90's choosen to go this way. Or why vertically aligned spaced pair offer a way to manage vertical directivity ( Horbach/Keele work is an extension of D'appolito's one).
There is a point when naysayers have to advance objective arguments to be taken seriously, dismissing something only on belief with no rational analysis is just... a waste of time for others.
Ok biased opinion. It's obvious.
Of course there is pro like the fact it help to reduce floor/ceiling bounce in particular with large driver like 15". The fact it mimics coaxial behavior is another pro, not even talking about the fact // drivers offer higher sensitivity and power admissible... but when your biased...
Maybe study why Kinoshita, Auspurger or the 'big' Jbl from 80's/90's choosen to go this way. Or why vertically aligned spaced pair offer a way to manage vertical directivity ( Horbach/Keele work is an extension of D'appolito's one).
There is a point when naysayers have to advance objective arguments to be taken seriously, dismissing something only on belief with no rational analysis is just... a waste of time for others.
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Ok let's try this
What is min and max C To C
I can also bring the coxial driver up and bring the lf drivers closer
I can go with a 10" cox
Not sure a 8" can keep up ?
But open to ideas
I believe my 15" driver in a vertical layout works in a mtm design
Even with a 400/500hz crossover point
I understand the horizontal layout is a problem and I'll have to adjust
Maybe 1 - 15
Maybe 2 - 12s
It's a center channel
I do want to achieve the best point source I can
Ah. So developper of this kind of thing based their math on 'magic'?
http://tripp.com.au/sbir.htm
Exactly why i gave reference to some models you can easily determine ctc distance and location, (have access to xover point and characteristic of horns/waveguide), enter the parameters into the previous link and make your own observation, then decide if an opinion is worth giving or not.
A loudspeaker is nothing out of context (location in room).
I repeat it's obvious you give an opinion without having studying in depth what you talk about.
There is many thread in there where professional designers gave their pov regarding this: Dave Smith (rip) gave us a nice lesson about vertically aligned loudspeakers ( initially line array) whith reference to the Snell he designed using log array approach which is here again a variation around D'Appolito work.
His member name was SpeakerDave in case you are curious enough to dig deeper. I shouldn't mention Dunlavy as his one of the guy who worked around this too. Or T.Hidley, Westlake owner and designer and one of the most known acoustician for high end studio which dropped his own loudspeakers for Kinoshita's first time he heard them... and developed the non environnemnt room around RM7.
And before dismissing the D.Smith, here is an example of what he did during his career:
https://www.tnt-audio.com/intervis/david_smith_e.html
It's just a joke you talk about opinion as you don't give anything to backup yours ( saying there is no advantage to a design choice is just a clue you haven't studyed the thing...).
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There is no definitive answer to this as it depend from a number of factors.
But let's say ideally 1/4 wavelength at xover frequency will garantee you to have perfect summing ( omni coverage). You can relax to 1/3 and you will still have coherent summing ( omni). It's not easy to achieve even in lf.
Once you start to go higher you gradually shift to narrower vertical directivity.
To have an idea check fig 3 of this doc: https://www.xlrtechs.com/dbkeele.co...ear Phase Digital Crossover Flters Part 2.pdf
If you want to go horn/compression driver check what Kinoshita San did for inspiration: https://web.archive.org/web/20040409112823/http://www.reyaudio.com/large-e.html
But let's say ideally 1/4 wavelength at xover frequency will garantee you to have perfect summing ( omni coverage). You can relax to 1/3 and you will still have coherent summing ( omni). It's not easy to achieve even in lf.
Once you start to go higher you gradually shift to narrower vertical directivity.
To have an idea check fig 3 of this doc: https://www.xlrtechs.com/dbkeele.co...ear Phase Digital Crossover Flters Part 2.pdf
If you want to go horn/compression driver check what Kinoshita San did for inspiration: https://web.archive.org/web/20040409112823/http://www.reyaudio.com/large-e.html
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I used the 15CXN88 in the Bitches Brew Live Edge Dipoles, with 2 X 15” subwoofers. crossover points 110Hz and 1100Hz.
Details here
https://www.diyaudio.com/community/threads/ultimate-open-baffle-gallery.123512/post-6682515
And here https://evo2.org/wp-content/uploads/2021/06/Bitches_Brew_Open_Baffle_Live_Edge_Speakers.pdf
The 15CXN88 is a superb driver and with DSP I easily achieved constant directivity across the entire band with linear phase and 120dB dynamic range.
Your question about WMW / MTM is related to my choice of subs which were MWW. The subs are mostly in phase with the mids if mids are wired in reverse polarity. I discuss the series crossover here:
https://www.diyaudio.com/community/...over-vs-parallel-for-subs-open-baffle.404680/
If you are doing MTM / WMW in a D’Appolito configuration, then the slopes of the 110Hz crossover need to put the drivers 90 https://www.diyaudio.com/community/...over-vs-parallel-for-subs-open-baffle.404680/ out of phase with each other instead of 0/180 which is what I did here.
Details here
https://www.diyaudio.com/community/threads/ultimate-open-baffle-gallery.123512/post-6682515
And here https://evo2.org/wp-content/uploads/2021/06/Bitches_Brew_Open_Baffle_Live_Edge_Speakers.pdf
The 15CXN88 is a superb driver and with DSP I easily achieved constant directivity across the entire band with linear phase and 120dB dynamic range.
Your question about WMW / MTM is related to my choice of subs which were MWW. The subs are mostly in phase with the mids if mids are wired in reverse polarity. I discuss the series crossover here:
https://www.diyaudio.com/community/...over-vs-parallel-for-subs-open-baffle.404680/
If you are doing MTM / WMW in a D’Appolito configuration, then the slopes of the 110Hz crossover need to put the drivers 90 https://www.diyaudio.com/community/...over-vs-parallel-for-subs-open-baffle.404680/ out of phase with each other instead of 0/180 which is what I did here.
Regarding the 15CXN88 1100Hz Crossover:
It’s essentially a 6dB crossover at 8K. But Combined with the downward tilt from the horn loading, means the acoustic xover is at 1KHz. I added a low-cut shelf filter at 1K which reduces tweeter excursion and gives very well behaved acoustic slopes with low phase shift:
https://www.diyaudio.com/community/...ompetition-updated-design.405104/post-7569413
I used the MindDSP Flex8 and config files are here
https://www.diyaudio.com/community/...ompetition-updated-design.405104/post-7565515
My objective was approximately 12dB/octave acoustic slopes on all drivers, so the tweeter and subs are normal polarity, mid reverse polarity. Therefore all drivers are acoustically in phase and the radiation patterns are well behaved. Finally I used a touch of FIR DSP to reverse the phase rotations and achieve true linear phase from 20-20K.
It’s essentially a 6dB crossover at 8K. But Combined with the downward tilt from the horn loading, means the acoustic xover is at 1KHz. I added a low-cut shelf filter at 1K which reduces tweeter excursion and gives very well behaved acoustic slopes with low phase shift:
https://www.diyaudio.com/community/...ompetition-updated-design.405104/post-7569413
I used the MindDSP Flex8 and config files are here
https://www.diyaudio.com/community/...ompetition-updated-design.405104/post-7565515
My objective was approximately 12dB/octave acoustic slopes on all drivers, so the tweeter and subs are normal polarity, mid reverse polarity. Therefore all drivers are acoustically in phase and the radiation patterns are well behaved. Finally I used a touch of FIR DSP to reverse the phase rotations and achieve true linear phase from 20-20K.
Wouldn't the smaller CXN88 versions be a little better behaved in terms of cone breakup and ease of integration (crossover design) ? Especially when there is no need for a large cone due to the support by large woofers.
Regards
Charles
Regards
Charles