Foam Core Board Speaker Enclosures?

[Cal Weldon]

Thanks for finding the patent Dave. I admit I didn't look as you did. I noticed that when you look up Daniel, you'll find a number of patents but not the speakers just computer stuff.

[xrk971]

Originally Posted by Cal Weldon

Progress, and I want to tell you about a sign from god. [must be 'cause I'm not that smart and I don't know who else to give the credit to.]

I have been wondering about attaching the trim pieces. I want it to be fairly fast as I am an impatient person. I want it to be fully adhered, not just spot adhered to reduce the chance of buzzing. I would like to use hot glue but the run is too long so I was settling on wood glue. Damn, wood glue takes a while to set up and needs lots of clamps. Hmph! Then it hit me. Lay a bead of wood glue with small gaps at set intervals. Use hot glue in the gaps and voila! Fully adhered and the hot glue does the clamping. They were done in no time. Wahoo!

I have a lot of cleaning to do before I mount the drivers so no pics yet but I'm sure I'll have them in a bit.

I also notice how the quality of workmanship goes downhill post-rum so last night's effort was well, how do you say...

...nah, I not saying anything, they'll be fine.

I did the same thing by using combo hot glue to clamp or tack in pkace and white pva to glue and seal the foam channels on my first one. The truth is I was running low on glue sticks and did this to conserve but found it works well as a clamp. Serendipty and necessity is the mother of invention.

[Doug R]

From the Peanut Gallery:

For attaching trim, tightly-stretched blue masking tape every two inches (perpendicular to the joint) or so works fine with wood glue. It's routinely used to apply trim to kitchen countertops, etc. Also, if you feel rushed, Elmer's white glue is just as good as Titebond and sets up more slowly.

Doug

[Don Hills]

OK, I printed Dave's PDF, dimensioned it, built an AkAbak model, scaled it to Cal's size (70 x 70 x 11.5 cm) and used Fostex FF125K T-S specs. The results are attached.
- The dimensions are "all over the map". The plan needs redrawing to make the horn sections taper more evenly. The "round spiral" cornu plans may be better.
- There are multiple resonances, as indicated by the SPL and impedance curves. Note the behaviour around 150 Hz. I did not include stuffing, so real life won't look as bad as the model.

Next step is to make an "ideal" AkAbak model - regular horn tapers. I have my doubts about the multiple path length horns, I'll try it with single length paths too.

[xrk971]

Originally Posted by Don Hills

OK, I printed Dave's PDF, dimensioned it, built an AkAbak model, scaled it to Cal's size (70 x 70 x 11.5 cm) and used Fostex FF125K T-S specs. The results are attached.
- The dimensions are "all over the map". The plan needs redrawing to make the horn sections taper more evenly. The "round spiral" cornu plans may be better.
- There are multiple resonances, as indicated by the SPL and impedance curves. Note the behaviour around 150 Hz. I did not include stuffing, so real life won't look as bad as the model.

Next step is to make an "ideal" AkAbak model - regular horn tapers. I have my doubts about the multiple path length horns, I'll try it with single length paths too.

Great! Someone finally modeling this thing. How do you model the split lengths? The sound that Cal describes appears to be lots of bass, whereas the sim is low on bass with lots of mid range peaks. Do you mind scaling it to 20 in (50 cm) and running it with the Vifa tc9fd- assume round spirals if it helps? Also, at the 70 cm, the longest path should get down to about 38 Hz, the sim shows falloff below 50 Hz. Thanks for tackling this.

[Cal Weldon]

Originally Posted by Doug R

For attaching trim, tightly-stretched blue masking tape every two inches (perpendicular to the joint)

That would work if the baffles weren't freshly oiled.

Originally Posted by xrk971

The sound that Cal describes appears to be lots of bass

Yes, but that peak at 200 Hz is very apparent. Stuffing will be the key here.

[Cal Weldon]

I have the trim applied and did the following stuffing:

First is the horn throat stuffing, worked into place with fingers and a spoon.
Next is the birds nest I created for the driver.
Last is the view of the chamber when stuffed.

[Cal Weldon]

That stuffing sucked the life out of the system. Limited bass but the mids returned. I guess that was too close to aperiodic.

Removed the throat insulation and left the chamber with the birds nest. We are getting close now. Some of that 200Hz is still there but with a touch of throat insulation I am guessing we can look after that.

[Cal Weldon]

Pics:

I see there is still a little glue string and a grill cloth tuck needed in the middle pick. Oops.

[xrk971]

Originally Posted by Cal Weldon

The stuffing sucked the life out of the cabinet. Limited bass but the mids returned. I guess that was too close to aperiodic.

Removed the throat insulation and left the chamber heavily stuffed. We are getting close now. Some of that 200Hz is still there but with a touch of throat insulation I am guessing we can look after that.

Cal,
Thanks for the minute play by play with your adjustments. Are you using a spectrum analyzer? Even software one using the computer mic is helpful.
I am listening to mine now and think that I must have just gotten lucky with the light stuffing i put in the throat.
Xrk971