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Old 20th December 2012, 10:33 PM   #11
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by Hilmar_G View Post
What width would you say is the absolute minimum this driver can work with? Chris mentioned something about 170mm....

That's the "height" figure on the small center channel enclosure in the Planet10 plan-set for Alpair10.2. For mains, I'd certainly look at going even wider - such as the approx 204mm quoted earlier as seen in both Scott's Pensil and Brines' MLTL.

From my experience, these two designers often target their designs to different goals/compromises - for example the above named enclosures have quite different CSA & aspect ratios, but the fact that they are within a cm or so from the same width is probably worth noting.
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Old 21st December 2012, 12:02 AM   #12
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I just had a discussion along the lines of "baby, I have to make them wider, they don't sound so good like this" ... insert heated argument here for a couple minutes, then... "ok, but then you have to make them less deep" . Seems like I can go ahead if I keep total volume about the same .
I think I will go for 180 mm and see how that works. The simulation for this does not look that different from the first I did. Well, new test enclosures will be built beginning next year. Thats what they are meant for, learn and verify.

Merry Christmas to you all,

Hilmar
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Old 21st December 2012, 05:20 PM   #13
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by Hilmar_G View Post
I just had a discussion along the lines of "baby, I have to make them wider, they don't sound so good like this" ... insert heated argument here for a couple minutes, then... "ok, but then you have to make them less deep" . Seems like I can go ahead if I keep total volume about the same .
I think I will go for 180 mm and see how that works. The simulation for this does not look that different from the first I did. Well, new test enclosures will be built beginning next year. Thats what they are meant for, learn and verify.

Merry Christmas to you all,

Hilmar

Depending on the enclosure architecture, adjustments to aspect ratio* of CSA are generally not a problem (at least as far as modeling would suggest), but line lengths, driver placement, and vent/ports for MLTLs. BIBs etc should be retained.

*Some of us have our own thoughts on shapes and ratios of "standard rectangular" boxes or "pipes" - as well as types of materials and bracing schemes - you indicated earlier this is planned to be a learning experience, so no doubt you'll be able to test some of those for yourself - after the first couple of dozen pairs of enclosures, you'll be able to focus in on what works for you.
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Old 22nd December 2012, 02:25 PM   #14
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Originally Posted by chrisb View Post
...after the first couple of dozen pairs of enclosures, you'll be able to focus in on what works for you.
I hope it does not take me quite as many tries to arrive at a funktional solution
I will propably never achieve the same level of experience you have, but thats one of the things this forum is for, isn't it: so people like me can benefit from the knowledge of experienced veterans like you (even if we do not always heed your advice )
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Old 26th December 2012, 01:48 PM   #15
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I am still trying to save my concept with the 150 mm baffle width. If the early reflections of higher frequencies is the problem then maybe this can be solved with proper lining? In the frugal-phile box library I found a ML-TL by Jim Griffin that also uses an internal baffle width of 150 mm. Has anyone ever built one of those? There is only a stuffing density specified, nothing about where to put it and if the walls should be lined with something.

Even if lining the walls does not make it possible to stay with 150 mm it should reduce the needed width, correct? What should I use? My first thought was carpet, then I searched around and found Bonded Logic Natural Fiber Acoustic Pads recommended. I would not feel comfortable using fiberglass since its a ported enclosure. What do you think?
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Old 26th December 2012, 06:52 PM   #16
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by Hilmar_G View Post
I am still trying to save my concept with the 150 mm baffle width. If the early reflections of higher frequencies is the problem then maybe this can be solved with proper lining? In the frugal-phile box library I found a ML-TL by Jim Griffin that also uses an internal baffle width of 150 mm. Has anyone ever built one of those? There is only a stuffing density specified, nothing about where to put it and if the walls should be lined with something.

Even if lining the walls does not make it possible to stay with 150 mm it should reduce the needed width, correct? What should I use? My first thought was carpet, then I searched around and found Bonded Logic Natural Fiber Acoustic Pads recommended. I would not feel comfortable using fiberglass since its a ported enclosure. What do you think?
a few thoughts:

I'm not sure about the enclosure of Jim's - with the hundreds of designs by various folks, it's hard to keep track of how many of which may have been built. Go ahead with the narrow width and see what you think.

If the Bonded Logic is the same as Ultra-touch recycled felted denim cotton fiber that we've been using for a couple of years, it's excellent to work with - although some enclosures still benefit from additional fill

If you're worried about loose fibers from the FB, then a simple trap of cheese-cloth or pantyhose at the internal aperture of vent should deal with that.

I would definitely not go any narrower than 150mm - I think that would place the side walls too close that wall lining wouldn't adequately control the LF energy, a good degree of which would be reflected back into the cone. This is not necessarily a huge issue with 1/8" thick car subwoofers, but with delicate cone full range drivers can mess things up substantially - which I've also found to be a problem with very shallow enclosures.
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Old 26th December 2012, 07:30 PM   #17
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If the Bonded Logic is the same as Ultra-touch
Bonded Logic is the company, Ultratouch is their product.

dave
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Old 27th December 2012, 04:23 PM   #18
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I had to find out that I can't get Ultratouch here in Germany. What I can get is "Nadelfilz", which apparently translates to "needle felting" and looks like this:
Click the image to open in full size.
This is available in 10 and 20 mm thickness.

Also there is something called "Damping 10", which is recycled something (most likely cotton like ultratouch, but they don't specify what exactly). It has an adhesive on one side already but is only available in 10 mm and looks like this:
Click the image to open in full size.

Does anyone know this stuff? What should I use?

With the 150 mm internal baffle I could only use 10 mm lining, there just would not be enough room for more. When I go 180 mm or more I can easily fit the 20 mm stuff.

Oh, and how would I fix the needle felting to the enclosure? For the test enclosure I would just nail it to the wall. Is that the way to go for the final enclosure too or is there a more elegant solution? Would glue be ok, or would it just hold the first layer and the rest rips off and falls down? I guess I will find out once I have it in my hands, but if anyone has prior experience...

Last edited by Hilmar_G; 27th December 2012 at 04:29 PM. Reason: more questions
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Old 27th December 2012, 06:18 PM   #19
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by Hilmar_G View Post
I had to find out that I can't get Ultratouch here in Germany. What I can get is "Nadelfilz", which apparently translates to "needle felting" and looks like this:
Click the image to open in full size.
This is available in 10 and 20 mm thickness.

Also there is something called "Damping 10", which is recycled something (most likely cotton like ultratouch, but they don't specify what exactly). It has an adhesive on one side already but is only available in 10 mm and looks like this:
Click the image to open in full size.

Does anyone know this stuff? What should I use?

With the 150 mm internal baffle I could only use 10 mm lining, there just would not be enough room for more. When I go 180 mm or more I can easily fit the 20 mm stuff.

Oh, and how would I fix the needle felting to the enclosure? For the test enclosure I would just nail it to the wall. Is that the way to go for the final enclosure too or is there a more elegant solution? Would glue be ok, or would it just hold the first layer and the rest rips off and falls down? I guess I will find out once I have it in my hands, but if anyone has prior experience...


The product with self adhesive backing looks interesting (provided it doesn't get stuck too early)

The UltraTouch (Bonded Logic) product we have available here is nominally 1/2" (12.7mm) and comes with a fabric backer. It's dense enough that with careful cutting you can get a pretty good friction fit, but for security's sake I find a quick tacking white PVA glue for melamine ( Rooglue.com) works great.
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Old 28th December 2012, 04:51 PM   #20
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To help me decide what thickness I need I did a quick calculation. Maximum sound absorption in a damping material occurs where the air velocity of a soundwave is highest. That is at 1/4, 3/4, 5/4, .... wavelength, since the velocity on the wall is 0. Now you can calculate what frequencies will have 1/4 of their wavelength inside the damping material or the other way around, how thick your damping material has to be if you want to optimally dampen a certain frequency (and all higher frequencies).

When I want everything above 1000 Hz optimally dampened I would need a damping material that is at least 86 mm thick.
With the 20 mm material optimal damping would start at 4300 Hz, with 10 mm at 8600 Hz and with 1/2" at 6750 Hz.

Mhm

I guess I will go for the 20 mm ...
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