Couple Simple Dipole Question...

[AJinFLA]

Probably made in China at the same factory that churns out many brands (see pic). The AL drivers do look interesting with the vented gap cooling. Like Davey suggested, run some 20-30hz tones into the driver holding it in your hand (not too loud now -you don't want to damage it). If it's relatively quiet - you're set.
If you can hear air chuffing from the smallish rear vent, there is a solution. You can drill a small hole (1/2-3/4") in the dust cap, with the driver facing downwards and a vacuum handy to suck out any debri. Glue a small disc (1") of grill cloth or breathable foam to cover the hole. This will allow air in under the cap from the front of the driver and slow the velocity of air being pushed/pulled out the vent. If it's suspension noise, then you could add a light amount of fill into the rear of your H.
You didn't mention how high you need it to go. The lower the XO you need, the deeper you can make the frame to gain a bit of output.
Good luck.

Cheers,

AJ

[santiu]

yup... looks like the same factory!

can I really do this test without mounting it to a baffle? If so, that would be GREAT! a lot less work for me. If so I can do that test tonight (just need to put some test tones on a CD as I don't have a signal generator I can use).

Drilling sounds a little scary, but doesn't seem to complicated. Basically just a little hole in the center of the cone right (since the dust cap is affixed to the cone?).

As for how high it needs to go. Well, I didn't mention that because I don't quite know. At first they will be crossed over to Wayne J.'s DBP's, since those are my speakers at the moment. So that crossover would be pretty high. However, this is just for playing around so I get to hear what they sound like. Once I finish building these woofers I was going to get started on a pair of back loaded horns with the Fostex FE108EZ using the fostex recommended enclosure. So ideally, I would like to have them designed to x-over to those speakers. There I'm not sure where I would crossover, but looking at the response on the plans, it seems like the x-over point would around 100 Hz. But then again, I have no idea what I'm doing, so that may be way off

Unfortunately I don't want to make the frame too deep to save space (since they already have to be 3 ft away from the back wall.). Any suggestions on how deep to make the H-frame? I messed around with the spl_max spreadsheet. But to be perfectly honest I don't have a feeling for sound levels, and consequently, I'm having a hard time interpreting the results.

Thanks again for all this help... you guys are awesome!

[Davey]

Santiu,

Take a look at the woofer section of my el-cheapo dipole system for a nominally sized H-baffle that should work okay for your setup.

http://home.comcast.net/~dreite/Davey/Davey.htm

The baffle and top/bottom sections are 11" X 23". The 11" depth gives a good compromise between EQ requirement and physical size.

Cheers,

Davey.

[santiu]

Well, I played a 30hz test tone and turned it up while just holding on the woofer. I have no clue how to tell how far the cone was moving, but it was a fair amount, although I don't think I hit the maximum travel (I actually probably only got 1/2 way there, I was too afraid of breaking the woofer). Anyhow, I didn't hear any noise other than the note being emitted by the woofer. Maybe I just don't know what I'm trying to listen for...

Are there any downsides to going ahead an putting the "vent" in the dust cap anyways?

Davey, thanks for the dimensions. I think I'll go with that. BTW, did you design those PCBs yourself? Also, which model Hammond chassis is that? I like it

[exipnos]

AJinFLA - Those are good looking drivers! Do they sound good? How much? Are they the same as the Pyle drivers you recommended in the most bang for the buck thread?

Cheers,

Exipnos

[AJinFLA]

AJinFLA - Those are good looking drivers! Do they sound good?

I have no clue, those are just pictures that I recognized as being similar to the drivers Santui has.

How much? Are they the same as the Pyle drivers you recommended in the most bang for the buck thread?

No, these are old model Pyles that have been discontinued. The ones in my max bang thread are still available.
That said, the 12" version (PLM1299) of these Pyle AL drivers were rated as a best buy by a german car mag. If you could find some cheap, they may actually be decent drivers for dipole use - especially the 15's.

Cheers,

AJ

[Davey]

Originally posted by santiu

Davey, thanks for the dimensions. I think I'll go with that. BTW, did you design those PCBs yourself? Also, which model Hammond chassis is that? I like it

Yep.

The Hammond enclosure is part # HM736-nd at Digikey.com

Cheers,

Davey.

[santiu]

okay, one last question, I promise (at least for this project)!

Do I need to flush mount the woofers? Does it make a difference?

thanks again, and you guys are awesome (what would a newbie like me do with out a place like this?)

[Davey]

Originally posted by santiu


Do I need to flush mount the woofers? Does it make a difference?

No. In fact it's better if you don't.....more meat for the screws. If you don't have a router you can cut the circles freehand with your jigsaw or rig a little jig that allows your saw to swing around in a circle.

Turn the computer off and fire up the table saw and have fun.

Davey.

[Retsel]

The depth of the sides of the H-baffle does make a difference. The deeper the sides, the lower in frequency that the baffle starts to roll off. Information is available on Linkwitz's webpage which informs you on how to calculate the frequency at which the baffle begins to roll off. You can use the baffle roll off frequency as part of your crossover strategy.

However, the deeper the sides, the more resonance that the sides will make. Thus, don't make the baffle as deep as possible. To help keep the front and side baffles from moving/resonating too much, you might want to double up on the wood (2 x 3/4 inch).

I have woofers mounted on open baffle. I initially had a pair of 15 inch drivers on open baffle in an H-baffle. I could get down flat to 45 hz or so without too much cone movement when playing Bermester's Chinese Drums piece. I then added a pair of Avalanche 18s mounted in a W-baffle. I can now get down flat to perhaps 25 hz or so. Open baffle bass is very excellent, even with less expensive drivers.

Retsel