The Diminui Dipole Project

[matevana]

Hi Folks,

I am experimenting with a small OB design and would appreciate your feedback. My goals were to develop a room friendly dipole and also address such issues as bi-amplification, crossovers and equalization in a manner that might be more affordable than usual. To date, I am pleased with the results and welcome questions, comments and thoughts on making improvements. The project details are here:

http://home.comcast.net/~cunundrum

Ed

[chinsettawong]

Hi Ed,

I like your nice and simple design.

Wachara C.

[bolserst]

Originally Posted by matevana

Hi Folks,
My goals were to develop a room friendly dipole and also address such issues as bi-amplification, crossovers and equalization in a manner that might be more affordable than usual. To date, I am pleased with the results and welcome questions, comments and thoughts on making improvements. The project details are here:

Hello,

I admire your ability to define the goals of your project and work toward them.
Keeping to the confines of your design:
1) chosen amplification and equalization technique
2) "full" range driver + helper woofer

The only real thoughts for improvement that spring to mind are driver choice and mass loading the baffle to minimize modulation of the full range driver by the woofer.

The helper woofer you chose was designed for car subwoofer use in a small enclosure. As such, it has high moving mass(about 135 grams) and a very stiff spider. You probably noticed that the high mass results in considerable shaking of your baffle. The Peerless SLS line is very popular for dipole woofer designs. You might consider the Peerless SLS 10". It's moving mass is just a bit over 50 grams so a lot less shaking will occur. The spider is much more compliant which in general allows a more linear suspension. These two differences offset resulting in nearly the same free air resonance and response as the Alpine woofer. Designed as mid-woofer rather than a subwoofer, Peerless includes an aluminum shorting ring which reduces the distortion in the mid-bass dramatically. The Peerless midband efficiency is about 2dB above the Alpine. The voice coil of the Peerless is a bit shorter, but with the amplifiers chosen this will not be a limiting factor.

I'm not really that familiar with extended range drivers like the Peerless3" you use, so was just wondering what led you to this particular driver?
Did you consider any other full range drivers besides the Peerless 3" ?
I have seen some folks prefer some of the Tang Band extended range drivers with phase plugs for better off-axis highs.

[matevana]

Thanks very much for your helpful comments bolserst. I must admit I never considered moving mass in the design. While the baffle vibration isn't horrible, I'm sure it can be improved some. The Alpine was selected in part due to its low cost, about 60 bucks for a driver with almost 13mm xmax and a QTS that isn't so low.

I also tried decoupling the full range driver from the baffle by mounting it on rubber faucet washers. Open cell foam was used to maintain the seal. I scrapped the idea since I couldnt detect a difference sonically.

I've been impressed with the Peerless 3" drivers since they came out about a year ago. They handle quite a bit of power, and to my ears sound better overall than either the aurasound 3" aluminum driver or the Fountek. All are similar but the the Peerless can get much louder w/o breakup. The aurosound may excel at the lower end, but my design calls for crossing over at 200Hz. They have good sparkle at the top end, especially with a little help from the active EQ.