Foam Core Board Speaker Enclosures?

[xrk971]

GM,
Thanks for posting the Weems Celotex enclosure - looks like a lot of fun to be had! Do you have the scans for the 8 inch version? Perfect for a Pioneer bofu.
Thanks,
X

[GM]

You're welcome! Unfortunately not since '72 and wouldn't have this one except for FreddyI and IIRC he didn't still have it either. All I remember is it's similar/smaller. Regardless, with MJK's, etc. software one can design something similar and/or better overall, I just haven't gotten around to it.

In retrospect and with a lot better understanding of such things, virtually all the published DIY projects I built or more recently reverse engineered requires anywhere from a ~0.7-1.2 Qt system, so the Bofu would need ~3-8 ohms of series resistance.

GM

[KLBIrd]

The first speaker project I built was the David Weems 8 inch Celotex corner enclosure in the November 1955, issue of Popular Electronics. I was fifteen at the time and I remember the trouble I got into for building it in my mother's kitchen. I used a speaker from a junked Zenith TV along with my ten watt Allied Radio Kit amp. Over those last six decades I built a number of his designs and in 1992 I wrote him and received a reply. We corresponded over the years and when I retired back to my native Missouri we finally met. I interviewed him for an article that appeared in the October 2009 issue of Audio Express. We spoke a few days ago and he doing well at age 91. I have many of his designs in PDF form from 1955 to 1970 that appeared in popular Electronics and Radio Electronics. He is truly the father of DIY speaker building.

[Cal Weldon]

Originally Posted by xrk971

When you say clamshell do you mean drivers are inside between two chambers with vent on one side?

See the pic. If you place another driver on the opposite side of where the driver is shown in a normal tapped horn and face it together it's called clamshelling. It's a type of isobaric loading. It allows for the downsizing of the cabinet by approximately 1/2. I wonder if it would work.

Originally Posted by zayne742

I really wonder if that will work

Me too but let's not forget the two products are different. the pink stuff is unfaced Type IV EPS made by Owens Corning. This is a faced iso board so I dare say the two are going to behave differently.

[xrk971]

Cal,
Thanks for enlightening me on isobaric driver arrangement! I was telling you about the 4th order bandpass subwoofer I was designing in WinISD and went in there and turned the "clamshell" switch to ON and sure enough the enclosure achieved better performance at half the volume! Pretty cool.

[Cal Weldon]

Well, since I don't have any software how do you feel about this?

Isobaric tapped horns

[xrk971]

I can try running a sim in HornResp for you later - are those your drivers on the link? You want tuning frequency to be at 50 Hz? Is that a 12 in driver? Tell me your approx box depth, height and horn length you want.

[Cal Weldon]

Thanks very much X.

Reckhorn W-130 6" driver

www.reckhorn.com - Bass-mid W 130

[xrk971]

Enclosure size limits? What is so special about these Reckhorn drivers? Efficiency is not very good. I guess you have them on hand and they need a home is why

[Cal Weldon]

You can read about them in the other thread. I would like to downsize a bit and having them concealed in the cabinet works for me also. Size would be about...

...let me go home and I'll give you the measures of the cabinet they are in now. I would like to reuse it.

The upper cabinets are the RS-1354 5.25" and a HiVi dome tweeter XO'd really high.