[454Casull]

Revised spreadsheet using four of these woofers per side, dipole. Woofers kindly revealed by MJL21193.

Probably will use a corner-loaded tapped horn for 60 Hz and under.

May also change the post to 2"x4" rectangular steel tube instead of 1.5"x1.5" to negate the need for reinforcement. I'd have to figure out a new way of mounting the tweeter pod, but it shouldn't be that difficult.

The woofers will be in a W-frame and ideally will be located halfway between the ceiling and the floor so as to run full-space as long as possible (constant power output). Realistically speaking, I will plop them next to the main array and then not ever touch them again due to "good enough" syndrome. Shit, will have to deal with the floor boost instead.

[Bob in St. Louis]

May also change the post to 2"x4" rectangular steel tube instead of 1.5"x1.5" to negate the need for reinforcement.

IDEA: You can also fill the tubes with sand to help add mass which will to help lower the resonating frequencies.

Bob

[454Casull]

May also change the post to 2"x4" rectangular steel tube instead of 1.5"x1.5" to negate the need for reinforcement.

IDEA: You can also fill the tubes with sand to help add mass which will to help lower the resonating frequencies.

Bob

Absolutely. Furthermore, steel sheet can be placed on the 4" sides with a soft adhesive for constrained-layer damping.

[Bob in St. Louis]

Will all that steel in such close proximity to the VCs have any adverse effect? 

Bob

[454Casull]

Will all that steel in such close proximity to the VCs have any adverse effect? 

Bob

I doubt it. Shielded motors don't often exhibit significant differences wrt to non-shielded.

[454Casull]

[Rudolf]

I hope that first comment was a compliment.

For sure!

What exactly do you mean by "provide space for the fastening rod"? As far as I can tell there is no interference from having either the cap screw or the bar in place.

Looking at your latest drawing I can see that no fastening rod is going through the tweeter pod any longer - which I had assumed.

The woofers will be in a W-frame and ideally will be located halfway between the ceiling and the floor

Do you really want to locate the W frame where the first vertical room mode is excited most? I always thought that locating a dipole close to the floor (or ceiling) would be the better way. IMHO it would help to avoid floor bounce too.

Rudolf

[454Casull]

Doesn't have to be exactly in the middle, I guess, but I do want the woofers to fire into full-space, at least near the low-pass point.

I don't know if the picture is too clear or not, but the bar that the tweeter is mounted to is centered under/in the pod.

[Rudolf]

What exactly do you mean by "provide space for the fastening rod"? As far as I can tell there is no interference from having either the cap screw or the bar in place.

Must be the language barrier. I was referring to the red detail:

[454Casull]

What exactly do you mean by "provide space for the fastening rod"? As far as I can tell there is no interference from having either the cap screw or the bar in place.

Must be the language barrier. I was referring to the red detail:

Oh, that pod was several revisions ago.

That reminds me, I've got to see how far I can shrink the pod.

EDIT: I can drop about an inch off. Pushes the dipole peak frequency up by a few hundred Hz.

EDIT2: Instead of filling the tube with sand, I think I'd like to try wax, or some other pourable substance that hardens to a soft solid.

[Bob in St. Louis]

The idea of sand is not only to add mass, but also absorb vibration. The sand particles will vibrate thereby dampening the resonances.
Not sure I've explained that in the most eloquent way, but the point is, you want the filler material to "vibrate".

Understand? 

Maybe somebody else could explain better.

Bob

[454Casull]

Yes, the motion of each grain of sand relative to the others will dissipate energy through friction. But since the system is not 100% sealed (e.g. when the threaded rods are removed) the sand will fall out if tipped over. There are damping compounds that do dissipate energy when vibrated, and who's to say one works better than the other? Perhaps a layer of Hawaphon on the inside with a layer of CLD on the outside - can even make it look sort of decent, if one used a gold-on-black scheme.

[Bob in St. Louis]

who's to say one works better than the other?

There you go....just be sure to take pictures. 

[454Casull]

Revised spreadsheet for AndrewT

[454Casull]

Step 1: Acquire drivers

http://g.imagehost.org/0985/nexxtech.jpg

Have the bass and midbass drivers now (stayed with the Beta-12A-2), waiting for the mids and tweets.

[454Casull]

Pieces being machined...

http://g.imagehost.org/0455/IMG_0983.jpg

I'm going to get started on the structure once I get the tweeters, which are the only missing drivers

[AJinFLA]

The nads??
Sounds rather naughty to me
A rather strange approach, but still interesting there cas.

cheers,

AJ

[454Casull]

Couple things missing:

• toroidal transformer for amp PS (500VA 25-0-25)
• chassis for amp, PS, active x-over
• breadboards for active x-over
• PS for active x-over
• assorted components for notch filters, etc. (have the parts for the dipole rolloff filters and L-R filters)
• the other half of the mounting components (bars and blocks)

Otherwise:

http://f.imagehost.org/view/0959/parts-001
http://f.imagehost.org/view/0828/parts-002

[longdrive55]

VERY cool looking project. Can't wait to see the finished speaker and hear your listening impressions. Keep up the good work!

[454Casull]

Doesn't work too well on bare ferrite magnet. Going to try it with the boot on.

If that doesn't work, I'll try some rubber on the inside. I also have some flange mounts in the works.

Fixed pic link

IMG_1105.jpg (381 KB)