CHR-70 GENERATION 3 - COMING SOON - Page 13 - diyAudio
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Old 20th March 2011, 12:00 PM   #121
Tyimo is offline Tyimo  Hungary
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Thanks Dave!
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Old 31st March 2011, 05:50 PM   #122
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Originally Posted by markaudio View Post
Hi Kipman,
Avoid dips to less than 4 ohm? Not sure precisely which set of frequencies you're thinking of. There's the sort of well known BT (British Telecom) engineers standard that says don't mess around with vocal frequencies, those being 400Hz to 4kHz. When asked, I usually suggest trying to cross below or above this band (where possible).

a little confusion here I was thinking about using the crossover to (partialy) correct baffle step therefore the slopes would be asymetric and both drivers would be playing at once and therfore the impedance would be less than 4ohms at low frequancies.

regardless this dosen't effect me as I aggree with the no crossover aproach in the midrange and use an active crossover (box full of opamps - I'm lazy); just thinking out loud with insufficiant explination.

I notice that Mark has a 'bass wide' version of the alpair 10, is there a chance of a 'treble wide' driver of some sort, that goes down to about 200Hz and can take more power/is more effciant?
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Old 4th April 2011, 01:04 PM   #123
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Hi Mark,

Will the specs be significantly different to the gen 2 ie fs and qts and does the frame diameter remain the same?

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Old 4th April 2011, 04:34 PM   #124
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Originally Posted by Bill poster View Post
Hi Mark,
Will the specs be significantly different to the gen 2 ie fs and qts and does the frame diameter remain the same?
Hi Bill,
We're about to make the 8 ohm pre-production samples (next week) so will publish the T/S, Fr range and impedance. Hoping there won't be big changes but lets see the outcomes from my tweaks.



Last edited by markaudio; 4th April 2011 at 04:36 PM. Reason: additional
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Old 4th April 2011, 06:34 PM   #125
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Should be interesting...
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Old 8th April 2011, 05:20 PM   #126
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I am getting very anxious to try out the new CHR. Hurry, hurry, hurry, please......
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Old 11th April 2011, 05:43 AM   #127
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Originally Posted by airkitty View Post
I am getting very anxious to try out the new CHR. Hurry, hurry, hurry, please......
Doing our best.
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Old 18th April 2011, 03:02 AM   #128
Bigun is offline Bigun  Canada
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Wow, 8 Ohms and multiple other upgrades and a price increase of only 'a few $' - will be watching with great interest !
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
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Old 20th April 2011, 02:01 AM   #129
StevenZ is offline StevenZ  United States
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Looking forward to these as everyone is out of stock. I'd like to make some office speakers and these will definitely be the ones I will use.
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Old 21st April 2011, 06:17 AM   #130
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Default Here's the new CHR-70 Gen 3!

OK Chaps,
Are you sitting comfortably? Then I'll begin...........

Summarising......your feedback broadly said:
1 - Make 8 Ohm
2 - Improve the frame
3 - Add some extra range
4 -More SPL
5 -But don't change the T/S too much

Bye gum......, you're a tough lot to please

So, we've pretty much managed to do what you've all requested. Quite a challenge as the feedback posed major challenges, especially between increasing SPL while not making radical changes to existing T/S.

The 8 Ohm coil winding has been made by Goto, the Japanese maker we use for the Alpair series. Other coil suppliers were struggling to cope with our spec. The coil body is thinner, reduced from 1000 micron to 720 micron with a lower mass paper wrap. More mass was removed by adding extra larger breather holes. This changed the flux density and resonance properties of this coil; Becoming more lively, requiring Matsubara San's (Bless him) help to come with a new spider capable of adding some additional damping on the coil to spider connection point. So a new spider Type CW3060 has been made to do the job.

Evan Yu and me have worked mainly on the cap design, integrating it with the existing cone and Multi-Form process, frame re-design, motor to frame seal and modifications to the motor mounting arrangement. My thanks to Evan for all his hard work. Frame diameter remains the same as the existing CHR.

Results. (graphs attached)
Firstly, there's a significant gain in the high range. The new driver is capable of reaching 25kHz. The new cap is doing its job quite well. I'll further modify it to help slightly reduce the 14-kHz peak but its not a drama at this end of the range. From 1.5kHz up, the Gen. 3 CHR is out-performng the old driver. The major gains are from 10kHz to 25kHz.

The driver's free air resonance is also improved, down to under 65Hz. With total Q maintained above 0.5, the driver should retrofit most existing CHR-70 box designs. New box designs could take a little more volume for those who want to extract extra bass. Moving mass has also been reduced to 4.14G allowing for a modest improvement in SPL to just over 85dB. There will be off-axis gains making room set-up a bit easier. Also, its mid range (1.5kHz to 10kHz) could also make it a handy mid-driver in a multiway system.

Overall, the Gen 3 is more mechanically and acoustically efficient compared to the existing driver. It will give those DIYers on a budget allot more "bang for buck".

Please note, these results are pre-production. I'm not anticipating any significant changes as all parts used are drawn from the assembly stock.

CHR70 new Gen.3/3060 (anechoic chamber LMS V4)
Revc= 7.200 Ohm
Fo= 64.709 Hz
Sd= 5.027K mm
Vas= 5.244 Ltr
Cms= 1.461K uM/N
Mmd= 3.730 g
Mms= 4.140 g
BL= 4.236 TM
Qms= 2.359
Qes= 0.675
Qts= 0.525
Levc= 39.766u H
No= 0.203 %
SPLo= 85.102 dB
Power= 20 watts (nom)
X max= 4.5-mm (1 way)

Apologies for the driver pic. I'll try to post a better version later.


Attached Images
File Type: jpg CHR-70-new Fr.jpg (269.0 KB, 330 views)
File Type: jpg CHR-70 new - IMp.jpg (276.8 KB, 318 views)
File Type: jpg CHR-70-gen3.jpg (84.4 KB, 308 views)

Last edited by markaudio; 21st April 2011 at 06:32 AM. Reason: typo fix
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