MCM 55-2982 new design

As Michael Chua of Amps-Lab has testet this inexpensive 12" Woofer and found it fared very well I had to order 4 to test them in Ripoles.
To my surprise it has a way different design now. I did not have a chance to test it yet, but what I saw was encouraging.
A few times in different forums the question came up if the rated xmax of 7mm was actually plus 3.5mm and minus 3.5mm but I can confirm that it has real +-7mm.
It is now very well vented under the spider and the voice coil windings can clearly be seen sticking out 7mm above the pole plate.
Thought I share this as some people may look for an inexpensive Bass unit that is well made.
 

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If you look at the actual measurements online you will find the published and measured parameters are vastly different. The 55-2982 will work open baffle due to the high Q. But a Q of 0.7 is a bit high for a Ripole. You will need to allow for more chamber volume. The measured Fs is also way higher than published (45Hz), but the loading using a Ripole will bring it down a few Hz. It will be a boombox in a sealed or vented alignment.
 
Ripoles are a special kind of animal.
I build 10", 12" and 18" Versions.
Fast attack and decay is the domain of them.
They don't need low Q woofers to achieve this.
With lowering fs I get the desired -3db at 30hz. While this would raise Q a bit to high I add my additional magnets. That will also keep my efficiency at 93db w/m.
My former woofers do a great job with their 0.75 Qts but their efficiency is only 89db w/m. On top of the double Ripoles will be a coaxial speaker with approximately 96db w/m and that's wy I choose the MCM woofers.
I looked hard to find woofers with xmax over 6mm and efficiency over 92db. These fit the bill without breaking the bank.
Putting an additional ferrite Ring magnet on the back pole plate of a Visaton BG20 lowers Qts from 0,45 to 0,37. (10cm dia. ring)
This can be done on any speaker.
Opposing force like north north will lower Q attracting force will up Q.
The apposing force will keep getting stronger till about 1/20 inch than it will suddenly stick without any glue to the back pole plate.
 
Ripoles are dipole radiators that take advantage of a loading cavity on both the front and back to lower the resonance, increase total Q, and slightly increase efficiency. They also benefit from force balancing of the moving mass, and even harmonic distortion when aligned in a push-pull configuration. They also have the drawback of the cancellation due to the depth of the cavity and the fact the driver is perpendicular to the the radiation axis. Because of this they cannot be used in as wide a bandwidth as a direct radiating dipole. Just one of the many possible dipole baffle configurations.
 
Sorry guys I did not get a notice that the thread moved on.
Yes my woofers came in and I can assure you that the 7mm Xmax is genuine.
Voice coil overhang is clearly visible.
It took Farnell about 6 weeks to ship them to me.
I did not have the time to do any TSP evaluation but Ampslab has done it for us.
 
Nice looking driver!

https://www.diyaudio.com/community/...-on-this-unusual-project.242692/#post-3638150

"Michael Chua

Member​

Joined 2006

Check out this 12" MCM 55-2982

Can be loaded with a 2 cuft Bass Reflex. Add a budget compression driver with a horn and you can get a pretty decent 2-way."
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FYI- * Not Ripoles * for inspiration, other options

other 12" MCM Woofers
Drews Brews
https://techtalk.parts-express.com/...half-sheet-heroes-quick-and-dirty-ht-monitors

https://techtalk.parts-express.com/forum/speaker-project-gallery/1490675-faux-pas
====

Google Translate
https://translate.google.com/

Vietnam Site (Audible Hertz Shop)- some Pure Audio Project facsimiles and others.

https://linhkienloadai.vn/blogs/du-an-loa

https://linhkienloadai-vn.translate...uto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp

Emenince Alpha 15A ( $$$- look for a cheaper woofer) Woofers in Series.
crossover @ 9:00 minute on video
https://linhkienloadai-vn.translate...uto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp

Emenince Alpha 15A, Woofers in Parallel
https://linhkienloadai-vn.translate...uto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp

Pure Audio Project
https://pureaudioproject.com/

----
Audio Circle
Open Baffle Resources- Documented designs & kits

https://www.audiocircle.com/index.php?board=90.0

Hestia OB mcm 55-2981 10"
https://www.audiocircle.com/index.php?topic=108003.0
 
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