DIY dipole plexiglass speakers - need advice !

[Ozne]

I am trying to gather information and thoughts from experienced people about building my own dipole speakers.

I have done a lot of research (A LOT!) and I do believe that making my own dipole speakers (often called open or infinite baffles I believe, but please correct me if I'm wrong!) would be best for my use, budget, and as a first DIY project in this field. I'm pretty handy and am a music lover. My dad and uncle are audiophiles and have made their own speakers when they were my age. Well, I'd like to do better and nicer!

I know it might sound weird but I want to make the "open enclosure" in plexiglass. I do know that the sound quality will decrease considerably but I'm ready to pay this price. As much as I love music, I am willing to sacrifice a little bit of that sound quality in order to make this project happen.

I am looking to make two towers, each with respectively 1 12" woofers, 1 8" mid-range, and 1 4" tweeter. This are all used Technics components from my current stereo. Since I am on a tight budget (but am definitely willing to spend the time; and some money) I will use what I have in stock!

Another reason why I am going with dipole speakers is that I wouldn't have to worry about the enclosure volume, and would really like to use these speakers as a piece of art of my own (this sounds cheesy but this is something big for me as I want to make these prefect!).

I am also planning on incorporating 1 subwoofer unit made of two 16" speakers.

Now, this being said, I have a few questions, and any comments or ideas are more than welcome!

- Fiberglass thickness: I was thinking 3/4" or 1". Thoughts on that? I am leaning toward the 1" because of vibrations issues and overall look.
- Subwoofer: I am undecided between making one unit with the two 16", or two separate units. Or incorporate the subwoofers to the towers?

Well, I guess that's all I had to ask, please feel free to comment or advice me on issues I might encounter!

Thanks a lot.
Enzo"

 

[D OB G]

Hi Enzo.

I've made a baffle with plexiglass (25mm or 1" thick- very expensive)!
I discovered that it is too flexible, even at that thickness, to resist the vibrations of a woofer.
I mounted the woofer on a sub-baffle that didn't touch (which I think is a good idea anyway for a flat baffle).
I have seen a picture of a Supravox mounted on plexiglass, but it was reinforced by- wood?

Regards,

David

 

[pforeman]

Sounds great! (Looks great)
I made open baffle speakers using 1/2 inch plexiglass actually LEXAN.
I made H frame woofers according to MJK's articles found here in the diy audio site (full range forum). I made four sets of those. One in solid maple for my daughter, two out of MDF for my brother and my friend, and one for myself out of maple plywood.
For the full range speakers, Three were made out of Lexan. Just for the two full range speakers (open baffle) (one piece) 2' X 2' it was almost $80 per pair!
It worked out well (is a inherently damped material).
I used a drill bit that I filed down so that the angle of the tip was flatter.
This causes the bit to not dig as quickly, and reduces the likelihood that the plastic will crack while drilling.
If you want to glue pieces together, you could try acetone. It will "disolve" the plastic, then clamp them together, and "voila".
If it migrates much, it might make the surface hazy. Give it a try on spare pieces first.
To attach the drivers, I drilled holes through the plastic, and used bolts, you could try this for attaching the side pieces to each other also.
good luck, I think it will be quite expensive.
Hope this helps,
Paul

 

[pforeman]

ps.
I got some scratches in mine while working on them, especially cutting out the hole for the driver.
Get some auto polish, and some polishing pads from your optometrist (used for fabricating eyeglasses. Apply the polishing pads to a block of wood apply polish liberally, and rub!
Paul

 

[Ozne]

Hi Enzo.

I've made a baffle with plexiglass (25mm or 1" thick- very expensive)!
I discovered that it is too flexible, even at that thickness, to resist the vibrations of a woofer.
I mounted the woofer on a sub-baffle that didn't touch (which I think is a good idea anyway for a flat baffle).
I have seen a picture of a Supravox mounted on plexiglass, but it was reinforced by- wood?

Regards,

David

Thanks a lot David. Yeah, I was afraid the 1" would be a little flexible... that's why I want to have the subwoofers built on a much smaller structure which (I guess) would leave less room for vibrations!

thanks for the advice!

 

[Ozne]

Sounds great! (Looks great)
I made open baffle speakers using 1/2 inch plexiglass actually LEXAN.
I made H frame woofers according to MJK's articles found here in the diy audio site (full range forum). I made four sets of those. One in solid maple for my daughter, two out of MDF for my brother and my friend, and one for myself out of maple plywood.
For the full range speakers, Three were made out of Lexan. Just for the two full range speakers (open baffle) (one piece) 2' X 2' it was almost $80 per pair!
It worked out well (is a inherently damped material).
I used a drill bit that I filed down so that the angle of the tip was flatter.
This causes the bit to not dig as quickly, and reduces the likelihood that the plastic will crack while drilling.
If you want to glue pieces together, you could try acetone. It will "disolve" the plastic, then clamp them together, and "voila".
If it migrates much, it might make the surface hazy. Give it a try on spare pieces first.
To attach the drivers, I drilled holes through the plastic, and used bolts, you could try this for attaching the side pieces to each other also.
good luck, I think it will be quite expensive.
Hope this helps,
Paul

This is perfect. I was going to go with an H frame as well. I was going to use acetone along with screws to keep the frame sides together. I know Lexan is very expensive. I work for a company which luckily uses plexiglass to manufacture its products. So I am hoping to get a sweet deal on that end!
Thanks a lot for sharing!

 

[Ozne]

pforeman, Thanks a lot for sharing.
I was going to use acetone along with nice stainless steel screws. The H frame is what I had in mind too but I am trying to think of something a little more original and less common, but that's definitely what I'll do if I don't come up with a good idea!
And for the plexiglass, the company I work for uses plexiglass to manufacture its products so I'm hoping to get a sweet deal...! If not, I'll have to go with some exotic wood or something similar.

Thanks again!
Enzo

 

[Tiroler]

Plexiglass has some excellent properies, but you need a milling machine to produce a baffle. Very likely companies that produce illuminated signs can make parts for you. Make a drawing in a CAD program or in Corel Draw, save it as vector file and solicit a quotation.
An excellent glue is ACRIFIX®
When choosing a glue, get proper advice from the seller. There are different glues for extruded and for cast material. If you don't get the right glue, your piece will suffer from a lot of cracks.

 

[Ozne]

Plexiglass has some excellent properies, but you need a milling machine to produce a baffle. Very likely companies that produce illuminated signs can make parts for you. Make a drawing in a CAD program or in Corel Draw, save it as vector file and solicit a quotation.
An excellent glue is ACRIFIX®
When choosing a glue, get proper advice from the seller. There are different glues for extruded and for cast material. If you don't get the right glue, your piece will suffer from a lot of cracks.

Interesting. I have a CAD software I can use at work. I will check the glues available to me and see what their pros and cons are. Thanks!

 

[Flaesh]

..1/2 inch plexiglass actually LEXAN..

Lexan is the brand name for polycarbonate, not PMMA(acril\plexiglass)
had you glued PC with acetone ..

 

[el`Ol]

A cheaper and better solution to make large OBs invisible is a rigid center part of thick multiplex or MDF and wings of ceiba bendable plywood. you could cover them with 3M DiNoc foil, which is available in about 500 different designs.

 

[Flaesh]

but it's not a solution to make large OBs (or something else) transparent

 

[Pano]

Why not do a magnet mount of the woofer? That way it would be decoupled from the plastic baffle. The baffle will still vibrate simply from air pressure, but not nearly as much as having a 12" woofer bolted to it.

Something like the Manzanita Project in plexi or Lexan could be very nice.

 

[PeteMcK]

before you start cutting expensive plexiglass, have you determined the suitability of the 12" woofers for OB?

 

[cuibono]

before you start cutting expensive plexiglass, have you determined the suitability of the 12" woofers for OB?

Actually, the question is how are you going to EQ them, and at what frequency would you like to cross them down to the subwoofer? I would guess that a single 12" woofer used OB would only be good down to 80Hz or so, at best. But that may be a good place to bring a sub in. Similarly, you will have a very very difficult time developing the EQ/crossover if you aren't doing any measurements. This could be a very time consuming project, just so you know.

I've worked with plexi/lexan some - it is seriously prone to breaking if not cut right. Milling may be your only option, and I would absolutely make a test baffle first out of wood. On the other hand, I don't think that you will be losing any sound quality by using plexi/lexan. I second magnet mounting all the drivers.

 

[Pano]

have you determined the suitability of the 12" woofers for OB?

I would guess that a single 12" woofer used OB would only be good down to 80Hz or so, at best.

I guess you guys didn't follow my link above. The Peerless 12" on a modest size baffle will play down to the upper 30s and do it with gusto. Takes a good bit of power tho - that's the trade off. Of course two 18" driver would be better, but you have to draw the line somewhere.

 

[jackies]

I, too, was thinking about making transparent OB speakers, it's a very attractive idea, has a great WAF potential. However, Lexan, plexiglass, etc. will be very expensive and will easily exceed the price of the drivers. So I would still suggest making the baffles from MDF first, then, when (if) you are fully satisfied with the sound, just make the transparent version...