Recessed B200 mounting?

SAC · 15th July 2008, 09:17 AM

Hi all

Would rear mounting a visaton B200 to two layers of 18mm ply, leaving a 36mm deep "horn", cause any significant disadvantages to the sound reproduction?

I'm only doing this for ease of creation with a fabric layering system I have in mind. I did see others create a waveguide with the alpha 15a below their B200 and I hope to do the same on top.

I will of course post pics in coming weeks once it is created.

P.S. What frequencies would a thin curtain fabric with holes in it likely attenuate? I used some nice stuff - air passes through, etc. - for my DIY sound panels, but on placing the fabric before my speakers there is a noticeable attenuation in the higher frquencies. I hoped to reduce the alpha 15a output above 1000hz with a layer or more of the stuff. I do not have any measuring equipment here.

Hope to hear from you, thanks.

GM · 15th July 2008, 01:54 PM

Greets!

As a TL, no, but it will create a notch with decaying peaks/nulls in the response due to the 'infinite' standing wave that occurs in circular tubes or on circular baffles, so flare it out at a minimum of 9.5 deg., rounding over the 'mouth' as much as practical. That, or 'cheat' as I do and just bevel it at 45 deg. and smooth it with sandpaper.

As you noticed, any material stretched over a driver attenuates the HF to some degree and as its density increases it lowers the corner (AKA 'knee') frequency where attenuation begins and when the resistance gets high enough it begins lowering the driver's Fs and effective Qts due to acoustic mass loading like a horn does.

Without measuring equipment, about all you can do AFAIK is either buy the appropriate absorber from Owens-Corning or similar or play a 1 kHz tone and just experiment until you begin attenuating it. Worked well enough for me anyway, though as always YMMV.

GM

SAC · 16th July 2008, 09:02 PM

Very interesting feedback GM

I am now tempted to buy that router I was looking at to achieve the finish you described. I could use the angled jigsaw but I do not know how well birch ply will respond. Time to get the test piece out.

Thanks

15th July 2008, 09:17 AM	#1
SAC diyAudio Member Join Date: Feb 2007 Location: London	Recessed B200 mounting? Hi all Would rear mounting a visaton B200 to two layers of 18mm ply, leaving a 36mm deep "horn", cause any significant disadvantages to the sound reproduction? I'm only doing this for ease of creation with a fabric layering system I have in mind. I did see others create a waveguide with the alpha 15a below their B200 and I hope to do the same on top. I will of course post pics in coming weeks once it is created. P.S. What frequencies would a thin curtain fabric with holes in it likely attenuate? I used some nice stuff - air passes through, etc. - for my DIY sound panels, but on placing the fabric before my speakers there is a noticeable attenuation in the higher frquencies. I hoped to reduce the alpha 15a output above 1000hz with a layer or more of the stuff. I do not have any measuring equipment here. Hope to hear from you, thanks.

15th July 2008, 01:54 PM	#2
GM diyAudio Member Join Date: Jun 2003 Location: Chamblee, Ga.	Greets! As a TL, no, but it will create a notch with decaying peaks/nulls in the response due to the 'infinite' standing wave that occurs in circular tubes or on circular baffles, so flare it out at a minimum of 9.5 deg., rounding over the 'mouth' as much as practical. That, or 'cheat' as I do and just bevel it at 45 deg. and smooth it with sandpaper. As you noticed, any material stretched over a driver attenuates the HF to some degree and as its density increases it lowers the corner (AKA 'knee') frequency where attenuation begins and when the resistance gets high enough it begins lowering the driver's Fs and effective Qts due to acoustic mass loading like a horn does. Without measuring equipment, about all you can do AFAIK is either buy the appropriate absorber from Owens-Corning or similar or play a 1 kHz tone and just experiment until you begin attenuating it. Worked well enough for me anyway, though as always YMMV. GM __________________ Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

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16th July 2008, 09:02 PM	#3
SAC diyAudio Member Join Date: Feb 2007 Location: London	Very interesting feedback GM I am now tempted to buy that router I was looking at to achieve the finish you described. I could use the angled jigsaw but I do not know how well birch ply will respond. Time to get the test piece out. Thanks

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