A Monster Construction Methods Shootout Thread

[augerpro]

It might be good to recap where my cabinet testing has led. I started measuring just simple materials, ply, MDF, in 1/2" and 3/4" to establish a baseline. Moving on CLD construction, I now used 1/4" MDF "skins" joined by either the adhesive under test, or with an additional layer of foam, cork, etc. in between. From this the Nidacore construction was probably best, but the simple 1/4" MDF glued together with Weicon 310M Flex was so close and so much easier and cheaper to make, I would use that in the future. From my bracing tests (prior to the results just posted above) the CLD with Weicon 310M Flex made a decent improvement over solid braces. The next question is whether adding those CLD braces to the simple Weicon CLD box would retain the benefits if both. The following is just such box, compared to a simple 1/2" MDF box with solid braces, and a 3/4" plywood box with solid braces to represent the typical DIY boxes.





I would say the rear panel measurement shows the Weicon CLD box to be superior to the others. The side measurement has it about the same as the MDF, with both being ahead of the 3/4" plywood box. I will say the addition of the CLD braces to the CLD box, didn't complement each other quite as I had hoped. Here is that CLD box with and without braces:





You really have to match the construction method to the passband of the driver. If it was a (sub)woofer, plywood with a lot of bracing is perfect. For a pure midrange crossed at 300hz, I might go with the simple CLD box without braces. The real trick is when it's a 2-way. The choice isn't so clear to me at this point.

[augerpro]

I also wanted to try a version of the simple Weicon CLD box (no braces) but using 1/4" MDF inside and 1/2 plywood on the outside. The idea being that the two materials would resonate at different frequencies and thereroe damp each other. I also did a version using 1/4" MDF & 1/2" MDF. I also switched from "box-within-a-box" construction to gluing the panels up ahead of time, then cutting to size and constructing the box. See pic to see what I mean. These are not braced and glued with Weicon 310M Flex. BTW, the Weicon can be found here.

[augerpro]

Here is another comparison I find interesting. This is the CLD of 1/4" and 1/2" MDF glued with Weicon, versus solid 3/4" MDF. So same nominal thickness and material, but one is solid and the other CLD:

[augerpro]

BTW the Weicon 310M Flex can be purchased here.

[augerpro]

Finished another round of testing today!

I've been wanting to test driver mounting methods, so here is my first attempt. I used 1/16" sorbothane sheet between the driver and box. Then a stub at the rear pressed down on teh driver with a sorbothane button between them. So the driver is completely isolated from anything by sorbothane. I used the 3/4" plywood box with matrix bracing from the last round as the control.







That's a dang good result right there! Now how to scale it up and make it practical? Normal rubber will have to be used too, sorbothane is really expensive.

Next, the newest version of the AugerPort. The second attempt at the Polk X-port inspired design hasn't made any improvement so I won't post those results. The other port is the microperforated one from the last round, but with 3 rows of holes instead of 5. I'm going to continue to work this idea.



And compared against the Harman inspired port on which it is based:



And some distortion results:

[augerpro]

I also took the CLD boxes from the last round and added CLD bracing. As a reminder, I made two boxes, both using Weicon Flex310M as the constrained layer/adhesive and using 1/2" mdf glued to 1/4" mdf, and the other box 1/2" plywood glued to 1/4" mdf. The following compares the box before and after the braces were added, then compared to each other, than compared to a typical 3/4" plywood box with oak dowel braces.

[augerpro]

Regarding the driver isolation results above, I wondered how just using the gasket and screws would behave, given that is the typical DIY mounting method. Through all this testing I was not using a gasket because I wanted this small driver to couple well to the cabinet so differences in construction methods would (hopefully) be more obvious. Leaving the sorbothane gasket in place and attaching the driver with screws was very nearly the same as no gasket at all. Clearly the screws were transferring energy to the cabinet quite well. So my next test today was to use rubber washers under the screw so it wasn't directly touching the driver frame. I label this "easy" below because anyone could copy this with hardly any change from typical DIy methods. I label the original experiment as "full isolation" because there was sorbothane completely isolating the driver. This would require more complex construction to pull off in a typical DIY design. I also compare these two results with no isolation at all, as in the above post.





So the "easy" method is more or less in between the "full" isolation and no isolation. So that is promising given how easy this is to implement in any design.

Then I used the "easy" method on the CLD box from yesterday, the one that is 1/4" mdf + 1/2" plywood, and included CLD braces. I thought that with the CLD construction the addition of driver isolation might not be as obvious:





Still looking better! So this might be a good time to take stock of where this testing has led. The plot above is pretty much the current state of my art: CLD box, CLD braces, and easy driver isolation. How does this compare to the typical DIY box made from the 3/4" plywood:





Mission accomplished! And this is without even applying the Resonix which I would in a typical build.

[gregrueff]

Love it!

Cheers,

[augerpro]

attached is a trowel I designed that can apply a uniform 1/32" layer right from the start. After applying the adhesive I would lay down the top panel starting at one end and laying it down inch-by-inch so no air is trapped.

[augerpro]

Here is a bit more info on the Polk-inspired port, so maybe I can get some help figuring out how to tune the resonator properly. I've used three resonators: one with a tap in the center, one with a tap in the center and 1/4 length (both taps sharing same air cavity), and another with a center tap and 1/4 length tap but having their own air cavity.



Looking back at the results it wasn't quite accurate to say they made no difference, there was a small benefit but less than anything else I've designed. Here it is compared to the port with microperforations and the original port on which all of these are based (Harman contour):



Thoughts?

[gregrueff]

Brandon,

Not what you asked, but I’d be curious what kind of driver isolation you could achieve by affixing the baffle (or part of the baffle, or the driver) to the cabinet using well nuts, screws, and a gasket.

In theory the screws would act as an extension of the driver frame, baffle, etc. but be isolated from everything else by the well nuts. The back of the driver frame or baffle would isolated per the gasket (assuming conventional driver mounting).

You could mount the driver in this way on a partial baffle that was also mounted to the main baffle in this way for isolation^2. ��

Cheers!

[augerpro]

Aren't well nuts metal?

[gregrueff]

Hopefully this works. If it doesn't just google rubber well nuts:

I've used rubber ones where the metal nut is embedded in rubber. It is inserted from the front side and tightening it compresses the rubber on the backside to pull tight.
They seem to be used in lots of applications- motorcycles, kayaks, windshields, etc.

Per this diagram, I make the top of the well nut flush with the top of the mounting surface so there is not a raised portion. Then a gasket can be laid flat.

Cheers,

[augerpro]

I forgot I have some of those. Unfortunately they are too big to test because I'm using a really small driver.

[technodanvan]

augerpro Have you done any further research into CLD? I'm very curious about the CLD bracing.

[augerpro]

Yeah, lots! You can pickup where I left off here: https://www.diyaudio.com/community/t...7#post-6798164

[technodanvan]

Outstanding, thank you!

[technodanvan]

So to summarize a bit, if one were to be interested in following your research for an actual loudspeaker:

1. Sidewall construction should not be made of the thickest, hardest woods you can get (i.e., bamboo is probably not helpful). Rather, stick with two (or possibly even three) layers adhered with Weicon Flex 310M. A two layer approach would probably be 1/2" baltic birch interior, 1/4" MDF exterior. I'd propose using that methodology plus an additional layer of 1/8" hardboard or 1/4" MDF on the exterior for a three layer solution. All panels should be adhered to each other using Weicon Flex 310M.
2. Interior bracing should be adhered to the sides using a typical wood glue, then connected together with Weicon Flex 310M. Have to experiment with window braces to see how well they work.
3. I've seen a few posts mention Resonix, but I must have missed where a specific model was used. I'm guessing you were referring to the Resonix CLD squares to add to the inside of the cabinet walls. Further, after researching Resonix a bit, I would think adding their Guardian product to in the interior midrange chamber would be a reasonable move. Given the expense I don't think it would be realistic to use anywhere else in the cabinet.
4. Drivers should be mounted with Sorbothane placed between the driver and the cabinet, using a rubber washer between the screws and the driver frame.

I have some questions though,

1. Would the baffle also be constructed with the Weicon adhesive, or would a traditional Jon Marsh-esque 3" bamboo/pin block and epoxy baffle be better? I'm assuming the baffle would be adhered to the rest of the cabinet using the Weicon Flex 310M adhesive either way, but the more I think about it having a constraining layer on a thick baffle would make sense...but only if it didn't affect the aesthetics of the speaker (i.e., if you just wanted to clearcoat the baffle, you probably would use a seamless adhesive).
2. Have you tried finishing over the Weicon adhesive? I would think there would be a seam if one were to just paint over it, and maybe a seam if one used thin veneer?
3. Regarding standmount speakers, would CLD be helpful in the construction of the stand itself? I'm thinking mostly on any horizontal surfaces that are adhered, not vertical, so maybe near the feet and the 'shelf' the speaker sets on? Then keep the base heavy (so it won't tip over), keep the center vertical supports reasonably light (so they can shift/move), and keep the top relatively light (mostly to keep the whole system becoming more top heavy than it already may be). There are already CLD-style feet out there, so purchasing those would be an option, though making them would be possible too.

Edit: Another question.

[augerpro]

1) I wouldn't avoid any particular wood, the fact that it is wood means they will all measure more alike than different. I think you would have to fundamentally change materials to make a real difference. Bamboo is different because it is not wood, but plant fibers joined with resin. Should be more dense. So I would not be surprised if it measured different than wood products. For better or worse I have no idea. My own usage will be similar to what you suggest, 1/2" high quality plywood joined to 1/4" MDF, because MDF machines nicely for exteriors. I do exactly this format (and another all MDF) in my thread above (and my website).

2) Yes attach to the sides with wood glue, but I admit I haven't measured that versus CLD braces attached with Weicon yet. But the rationale is sound I think. And I did a build that used 3M VHB tape to attach solid braces to the walls and the results weren't anything great. The CLD braces attached to the walls with wood glue were better. I do have to try window braces, if only to prove to myself that no matter how many braces you use, if you end up with a rigid structure it will have significant panel resonances. Damping of some sort is the only solution.

3)Yes, the CLD tiles

4) Correct, but that might only be best with midranges and tweeters whose bandwidth is in the primary panel resonance region. I'm not sure that bass drivers should be couple so loosely.

I think ideally the baffle would be CLD too. But I agree that finishing will be problematic. I'm wrestling with that decision myself.

[technodanvan]

Outstanding, thank you for doing all of this! Have you built a loudspeaker using these principles yet?

[augerpro]

In process right now

[technodanvan]

Right on. In my research on the Misco XBL^2 drivers I came across your thread at DIYAudio about a 3-way anchored by an 8" woofer. I'm guessing that's your current project? If so I have some data on two proof-of-concept Misco 8" XBL^2 drivers (one poly, one paper) they made using off-the-shelf parts and the 6.5" motor. I'm guessing that's probably not what you're interested in since they aren't optimized, but let me know if you want the data and I can send it your way.

Did you see my question regarding speaker stands? I think I edited my previous post about the time you were responding to me.

[augerpro]

Oh yes I'd like the info on the new 8"! They had planned for them to come out last summer, and I hadn't heard anything since. My project is a family of speakers. First will use the SB "ceramic" drivers, and the second will be Satori Textreme woofers and probably TX and BE tweeters. All using my waveguides. These establish a certain design format that I can plug different drivers into. One super-high-value idea I had was SB26CDC tweeter, Zaph ZA14 midrange (excellent mid), and Misco 6502 woofers. The clean SPL capability of this would be pretty incredible.

I use sorbothane feet on the top of my speaker stands to do most of the isolation. I don't really see a benefit to the speaker energy going into the stand. I do also fill my stands with sand, but that is secondary isolation. I do want to build adjustable stands using aluminum T-slot extrusion. If you do something like that, I'd love to see it.

[augerpro]

I want to start some IMD testing, inspired by Purifi. I think the Misco would show performance that might set it apart from many of the popular drivers. And even from the Anarchy. My own reading of the Klippel results suggest they have optimized the soft parts better, and suspension limiting is much less of a brick wall. And using neo motors, should not have an issue with Magnetic Hysteresis Distortion and Force Factor Modulation as Purifi calls it.

[technodanvan]

I'll just share it here, in case anyone else is interested. I know you know this, but for anyone viewing this post with no context, this data is provided by Misco for two proof-of-concept drivers. These are 8" XBL^2 drivers with off-the-shelf parts - meaning the cone and spider are not optimized for this purpose, they're just from another product line from Misco. This in no way represents an actual product at this time - that said they did offer me an opportunity to have some ready made if I liked. I don't know how long that offer is good for, or what the cost would be.

All that said, here you go. I'd love to have some thoughts from others! I can tell you in my modeling I couldn't get either of these to play well ported or with a PR.

Poly Cone Parameters:




Paper Cone Parameters:




Frequency Response (Red is Paper, Black is Poly)