Greg Monfort ML-TL Design Update for Alpair 10.2 - Page 3 - diyAudio
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Old 15th July 2013, 05:28 PM   #21
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Greg,
Do your new updated dimensions include the internal brace per Planet 10's original drawing, or is it omitted? Thx.
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Old 15th July 2013, 05:53 PM   #22
GM is offline GM  United States
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Yes, it's included.
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Old 16th July 2013, 12:01 PM   #23
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Quote:
Originally Posted by chrisb View Post
I'd suggest reconsidering very shallow depth enclosures for any wide-band driver, and most particularly very thin metal cone units such as any of Mark's drivers or the new Jordans for example.
Could you elaborate?
Shallow cabs not only look better and are easier to place (not sticking into the room so much), they also have advantages wrt bafflestep and portloading.
So what are the problems?
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Old 16th July 2013, 02:11 PM   #24
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Reflections off the back wall coming through the cone / modulating its resonant behaviour can be a problem in some cases. The same applies to very narrow boxes, except there it's reflections off the sidewalls. Sometimes tricky to damp out. Not likely to be an issue here though -Greg knows what he's doing.

BTW -not everybody thinks that wide / shallow boxes look better. Some prefer narrow, deep boxes. Subjective taste. I like both. Depends what the design requirements are.

Last edited by Scottmoose; 16th July 2013 at 02:14 PM.
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Old 16th July 2013, 03:20 PM   #25
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Oh, it's just that. Reflections are worse from sides in my experience. Most FR units have so large magnets that the backwave are sent mostly to the sides anyway. Not that you should put the driver all the way to the back-wall though.

Deep cabs to me just smack of retail speaker emulation. Because that's how most speakers in the shops are done. I guess they have convinced the salespeople, who in turn can convince the wives, in the heat of the moment at least, that that is The Right Way (tm).
Wide cabs are much more unashamed and unapologetic about themselves. If you have made a nice finish why not show it off? And they are, in the long run, much less intrusive in a living room. /My two cents.
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Old 16th July 2013, 03:22 PM   #26
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Hmm, I managed to miss Chris's post, which opens up a 'can o' worms' WRT acceptable performance trade-offs and in this scenario, damping material choices.

FWIW, I’ve built many tower/column [now TL or MLTL] alignments where the driver was a slight force fit to both keep the cab as flat as practical and to mass and compression load/support the driver, ie. physically as high an aspect ratio as practical. Damping was either Celotex, thick felt carpet padding or acoustic fiberglass insulation.

All these have a much higher, wider BW damping performance curve, so compression, early reflections are pretty much moot till down in the cab's gain BW curve where I want[ed] it since maintaining as much acoustic efficiency as practical was/is one of my prime performance goals.

Celotex is long gone and finding/affording the kind of density, quality felt I used way back when makes it a poor bang/buck choice and folk’s acoustic fiberglass insulation health concerns is a real ‘head scratching’ one for me since it’s designed for lining ventilation ductwork to reduce its TL ‘vent’ noise, ergo to my way of thinking, the obvious choice for damping speaker cabs, especially high aspect ratio ones whether horizontally and/or vertically.

Anyway, the pioneers of audio concluded that as the aspect ratio increased beyond ~1.2732:1 in an undamped horn, measurable pattern distortion increased with increasing ratio to the point of pattern ‘flip’ and anyone who’s ever heard different shaped horns has experienced its impact on signal accuracy, so it seems reasonable to me that this would impact a driver’s ability to accurately track a signal over an increasing portion of its mids, HF BW with increasing aspect ratio when placed in such an acoustic environment if not properly damped.

This is why my default recommendation is a golden ratio since folks mostly prefer polyfil or similar stuffing nowadays.

GM
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Old 16th July 2013, 03:41 PM   #27
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Very cool to see more design options for the new 10's. Tall and thin, sort of the Jackie Kennedy of Alpairs. OK I guess I just dated myself. LOL
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Old 16th July 2013, 04:24 PM   #28
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Quote:
Originally Posted by Squeak View Post
Oh, it's just that. Reflections are worse from sides in my experience. Most FR units have so large magnets that the backwave are sent mostly to the sides anyway. Not that you should put the driver all the way to the back-wall though.
Yes, generally sidewall reflections are the more problematic. It doesn't often happen off the back-wall, but it's not unheard of (the PAWO had problems along these lines IIRC), so if nothing else, as GM says, it's a reminder to ensure the box is properly damped.


Quote:
Deep cabs to me just smack of retail speaker emulation. Because that's how most speakers in the shops are done. I guess they have convinced the salespeople, who in turn can convince the wives, in the heat of the moment at least, that that is The Right Way (tm).
Wide cabs are much more unashamed and unapologetic about themselves. If you have made a nice finish why not show it off? And they are, in the long run, much less intrusive in a living room. /My two cents.
You could say the same (retail emulation) about wider boxes forty years or more back. DIY generally reflects the commercial vogue of the age. Nothing new about that. For better or worse. Usually worse these days, unfortunately.

Last edited by Scottmoose; 16th July 2013 at 04:38 PM.
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Old 16th July 2013, 08:16 PM   #29
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Short comment:

I try to avoid wide cabinets to reduce baffle step. As the quarter wave pipe is stuffed I do not pay much attention to internal reflections from the side walls.

Hi from Bjorn
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Old 16th July 2013, 08:27 PM   #30
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Isn't that one of the main points of having a wide cab? IE that there isn't any need for a BSC circuit?
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