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Old 16th September 2012, 07:54 AM   #131
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Quote:
Originally Posted by natehansen66 View Post
I really don't see any good reason to go baffleless on the bass drivers.
Yet I don't see any good reason for not isolating the woofer itself .
Yes you do isolate the other drivers from the tremendous vibrations induced by woofer's cone movement , but why you don't decouple the woofer from the environment ? So the problem it's not resolved yet .
Just because it transmits good vibrations and you like the feel of them ?
That's another story , as also should be investigated more the kind of sound
perceived when using some dipole sources .
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Old 16th September 2012, 08:17 AM   #132
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Sorry I don't know what I was thinking when I typed that... I was actually thinking of a H or U frame. I was actually thinking about the tweeter and mids when I made that statement, not about the woofers which we are discussing. Must have been having a blonde moment.

Picowall I am of a similar mind if the tweet - mid can be decoupled from the woofers without causing major hassles I would like to head down that path.

Based on what people are saying I take it the woofer suffers from greater dipole roll off than the other drivers? So it wont hurt to have additional dB in the low end of town.
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Old 16th September 2012, 08:31 AM   #133
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The roll off starts as function of baffle width. The wider the baffle the lower it will go before starting to roll off. Having said that I am not much of a fan of big OB unless you have a big room. They start losing their magic as you go bigger if you don't have a big room to move them out into the room
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Old 16th September 2012, 08:41 AM   #134
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Yes , dipole roll off is Just another name for cancellation , as it appears in the
first page of any book about speakers .
You have the useful signal from the front and the negation of it from the back.
I would move towards a design principle of a controlled attenuation of the back wave .
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Old 16th September 2012, 08:51 AM   #135
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Last night while I was in double 15 mode I came up with an idea to reduce the height of the 15"'s to allow drivers to be placed above the woofers without making it too high.

This is a pic of what I had in mind. Please note I have just repurposed the Sketch Up mids for demontation purposes only to demonstrate the idea.

Kind of like a H but slanting the board between the drivers to allow them to be closer together.

Figure with 15" driver should be able to get a couple of inches overlap on both drivers with a nett gain of ~4-6". That would address a lot of the height issues.

Not so sure how it would go with reducing sound since one side of each of the drivers would be slightly compressed.

Was thinking of clear acrylic to build the box...

Edit:
oops forgot the sides...

Edit 2:
and here is what I had in mind to isolate the woofers from the tweeter and mids.
Attached Images
File Type: jpg Double Dipole.jpg (60.5 KB, 228 views)
File Type: jpg Double Dipole 2.jpg (61.4 KB, 224 views)
File Type: jpg Double Dipole 3.jpg (50.2 KB, 218 views)

Last edited by Silent Screamer; 16th September 2012 at 09:13 AM.
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Old 16th September 2012, 09:45 AM   #136
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There is another method. Check out slot loaded open baffle
2 woofers for the height of one
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Old 16th September 2012, 10:15 AM   #137
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ok I was wondering if that would work or if it would cancel itself out...

The idea of putting them behind each other like that did occur to me but wasn't sure if it would work.

Kind of like a isobaric without sealing the drivers.
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Old 16th September 2012, 10:21 AM   #138
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Nelson pass has 6 x 8 in a slot loaded open baffle, and others are doing other variations.
There is thread on it.

There is also a W arrangement in push pull.
I will building all of these as soon as more woofers arrive
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Old 16th September 2012, 10:51 AM   #139
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Yes just reading the article now (or at least looking at the pictures) The Slot Loaded Open Baffle Project Article By Nelson Pass

Hmmm think I need to investigate this idea a bit further.
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Old 16th September 2012, 02:25 PM   #140
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I think the trade-off with adding multiple bass woofers to an enclosure is that it limits flexibility (placement). If you're determined, by design, to have all the drivers located in one area ... that's fine and it works great. ... but if you're interested in exciting the room even better with LF you'd be sort of stuck using that driver arrangement ... maybe leaving something on the table?

I like adding the mains into a low lying (and low level) fog of bass. The mains add focus to the detail of the fog. Potential draw back here is time alignment ... it helps. ... and this might get complicated with stereo bass. Although, mine seem to stay coherent in a pretty good sized listening area. Guessing that if the overlap is low enough timing doesn't need to be absolutely "perfect". If they're placed a good distance though, not trying to TA the signal will get you boomy LF(s).

At any rate, wouldn't be anything stopping a guy from building separate 15" enclosures ... either U or H frames giving him some placement flexibility. For instance ... what if you wanted to elevate one of the LF drivers to help even out room response at the listening position? Can't if the packaging won't allow it.

If separation is not your cup of tea after all ... just gang them back together. ... and you'll have some flexibility in this arrangement as well.

Last edited by puppet; 16th September 2012 at 02:28 PM.
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