[DL86]

I just thought of an idea although not sure if it's feasible. On previous threads it was discussed about resonance's with thin waveguides. Now what if someone uses a fine concrete mix or something similar to create a mould from an existing waveguide then use the mirror mould to create waveguides from. I see possibility of making a damn hard waveguide out of which would be resonance free.


Really liking my waveguide based speakers as they are, but would anyone think there would be any improvement in doing this?


What would be a good mixture to use for such a thing?

 

[LTD02]

i've had similar thoughts in the past. i've suggested enclosing the back of the waveguide in a solid concrete block a few times.


the reason why plastic and acoustic foam are used is because most of these things are designed to be portable.


however, it may also be more trouble than it is worth. a plastic horn wrapped in clay on the back may be good enough.


i definitely like the approach.

 

[FastForward763]

If you wanted to make a mould to produce a bunch of them fiberglass would be your best choice for the mould but it's a bit of work.


If you only want to reinforce and stiffen ones you already have then fiberglass would again be your best bet. Just scuff the back of the waveguides and use an epoxy resin and some type of woven cloth. The materials can be found at any body or boat shop.

 

[A9X-308]

Build a small box around your WG so that the throat and driver are outside it. Fill box with clean, dry sand.

 

[penngray]



Quote:
Originally Posted by A9X-308 /forum/post/18604439


Build a small box around your WG so that the throat and driver are outside it. Fill box with clean, dry sand.

That is an interesting solution that I would like to try.


But what about just filling it with that spray foam?


I have new waveguide boxes to build and I want to try something since Im curious if it will improve the SQ over my current boxes.

 

[Looneybomber]

I would think layers of various conventional (car audio) sound deadening would work good enough.

Quote:
Originally Posted by A9X-308 /forum/post/18604439


Build a small box around your WG so that the throat and driver are outside it. Fill box with clean, dry sand.

How would you seal it up? Silicon/caulk? I'd be scared it'd leak later on.

 

[mjg100]



Quote:
Originally Posted by Looneybomber /forum/post/18606487


How would you seal it up? Silicon/caulk? I'd be scared it'd leak later on.

It would be easy to seal, so I would not worry about a leak. For speaker stands in my downstairs room, I bought marble covered pedestals and filled with sand. These have a removable plug and loss of sand is not a problem. As you said you could drill a hole in the back, set speaker on it's face, pour sand in and then seal with caulk. Very simple solution.

 

[A9X-308]



Quote:
Originally Posted by penngray /forum/post/18606474


That is an interesting solution that I would like to try.

Sand makes such an excellent damping agent and it's very cheap to do this and reversible. Maybe $5.

Quote:
Originally Posted by penngray /forum/post/18606474


But what about just filling it with that spray foam?

Dunno, haven't tried it.

Quote:
Originally Posted by penngray /forum/post/18606474


I have new waveguide boxes to build and I want to try something since Im curious if it will improve the SQ over my current boxes.

I'm not saying it will make an audibly worthwhile difference, but if you are going to try something, this is as good as anything else for the cost and effort, both of which are small especially if you consider it during the design and build. It will also serve to dampen the external panels the sand is resting against.

Quote:
Originally Posted by Looneybomber /forum/post/18606487


How would you seal it up? Silicon/caulk? I'd be scared it'd leak later on.

Silicon could be fine. Put the fill hole near the top and make a solid cover (hole saw scrap) and silicon it back into place when full. No NASA grade engineering needed here.

 

[LTD02]

that's interesting penn, do you have any damping on the back of your horns now?


i've read at least one review where damping was applied to the back of a horn and it went from mediocre to spectacular. there is a guy on diyaudio who has done some tests and concludes audible differences are achieved when damped with clay. when he wrote up his findings, dr. geddes agreed, saying something like [paraphrasing] "i don't want to give away all my secrets, but damping the horn is one of the keys to good sound."

 

[penngray]



Quote:
Originally Posted by LTD02 /forum/post/18606572


that's interesting penn, do you have any damping on the back of your horns now?


i've read at least one review where damping was applied to the back of a horn and it went from mediocre to spectacular. there is a guy on diyaudio who has done some tests and concludes audible differences are achieved when damped with clay. when he wrote up his findings, dr. geddes agreed, saying something like [paraphrasing] "i don't want to give away all my secrets, but damping the horn is one of the keys to good sound."

I do not have any dampening material and all my EQing hasn't improved them to the SQ I would like at the lower SPL levels. I still have gain structure changes to try also. I picked up a Halfer amp from Audiogon last friday to try it out since my amps do not have VCs.



sumaudioguy over on DIY uses some dampening materals found here

http://www.earsc.com/search.asp?keyw...-40PSA&x=0&y=0

 

[pnw]

Here is a BMS 4552ND on a 12" MSC plastic WG (very similar to the 12" PE) no treatment:

Here is the same driver & waveguide with about 2-3 pounds of a polyester resin (fiberglass resin) and sand mixture molded to the back of the WG:

This waveguide is a continuous curve in all directions, so quite strong considering the thin construction. There might be more difference for square/rectangular horns with "flat" sides???

 

[penngray]



Quote:
Originally Posted by LTD02 /forum/post/18606572


that's interesting penn, do you have any damping on the back of your horns now?


i've read at least one review where damping was applied to the back of a horn and it went from mediocre to spectacular. there is a guy on diyaudio who has done some tests and concludes audible differences are achieved when damped with clay. when he wrote up his findings, dr. geddes agreed, saying something like [paraphrasing] "i don't want to give away all my secrets, but damping the horn is one of the keys to good sound."

Do you have a link to that thread?

 

[LTD02]

i think it was in this thread, but i haven't read it again to find out which page it was on.


it was definitely in response to member "patrick bateman".

http://www.diyaudio.com/forums/multi...ix-horn-2.html

 

[LTD02]

"i've read at least one review where damping was applied to the back of a horn and it went from mediocre to spectacular."


this was in respect to the h290 horn on the 4pi, iirc. i don't have a link to that one.

 

[Looneybomber]



Quote:
Originally Posted by A9X-308 /forum/post/18606525


Silicon could be fine. Put the fill hole near the top and make a solid cover (hole saw scrap) and silicon it back into place when full. No NASA grade engineering needed here.

I don't mean your plug for when you fill it, but the seal between the rear of the box and the waveguide. Once you mount the waveguide to the box, you'd then have to caulk like crazy between the two other wise the sand is going to leak out onto your drivers where they mount to the wave guide.

 

[A9X-308]



Quote:
Originally Posted by Looneybomber /forum/post/18607458


I don't mean your plug for when you fill it, but the seal between the rear of the box and the waveguide. Once you mount the waveguide to the box, you'd then have to caulk like crazy between the two other wise the sand is going to leak out onto your drivers where they mount to the wave guide.

I got what you meant. I don't see much of an issue making the rear plate for the sandbox for what you've shown. It wouldn't be much different from making the templates to flush mount drivers that aren't round to the baffle front. Do it neatly and you'll need little sealer at all. Mountain;molehill.


Plus in your example, both drivers, the CD and the mid, are closed back so makes it even less of an issue should the odd grain escape.


I'm still dubious that any of these damping suggestions will make much if any difference to most plastic flares. The idea originally came from Altec sheet steel construction flares like the multicells where it can make a large difference. Pick up one by the throat and rap the mouth with your knuckle and that can ring quite audibly.

 

[Erich H]

I've used a certain type of "liquid rubber" to make molds and that would really dampen the plastic waveguide.


I think it would be very easy to coat the back side with some fiberglass cloth that's saturated with liquid rubber or even resin mixed with rubber shavings, etc. I'd think there are many ways to do it.


There are also different types of material similar to roofing tar (but not so messy and smelly) that could be smeared on if you wanted a quick job.

 

[penngray]

How about just trying modelling clay??


I have read several older threads on Geddes waveguides and how he suggested using modelling clay on the backs of them.


I definitely have to try this and the sand box suggestion myself.

 

[catapult]

There are two issues, damping the horn and isolating the horn from the woofer. Horns should really have their own sub-enclosure for isolation. It doesn't make any sense to build a 3/4" or 1" box with lots of bracing for the woofer and then have a big old horn open to the same space when the horn's plastic is only 1/8"-1/4" thick. A lot of the woofer's midrange back-wave is going to leak through that. Once you get it isolated, you can work on damping so it doesn't ring so much when you tap it with a coin.

 

[penngray]



Quote:
Originally Posted by catapult /forum/post/18623689


There are two issues, damping the horn and isolating the horn from the woofer. Horns should really have their own sub-enclosure for isolation. It doesn't make any sense to build a 3/4" or 1" box with lots of bracing for the woofer and then have a big old horn open to the same space when the horn's plastic is only 1/8"-1/4" thick. A lot of the woofer's midrange back-wave is going to leak through that. Once you get it isolated, you can work on damping so it doesn't ring so much when you tap it with a coin.

Valid points that I need to address on my next build, version 2 of my waveguides.