My first build! MarkAudio CHR-70 in da house - Page 3 - diyAudio
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Old 16th March 2009, 01:25 AM   #21
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Hi Chris,
Long time, hope you're doing well.
Yes - it's a interesting balance when designing a driver. With the CHR-70 I've erred towards higher mechanical damping so the driver's more stable on higher loads. My thinking was the CHR would appeal to a variety of users on a smaller budget, many having class AB amplification, and possibly into class D and chip amp country. At the same time, still trying to balance the needs of the more experienced guys running class A 5 watts upwards. In our studio, we are running both Alpair-6 and CHR's with ease on Brain Cherry's (Diy-hifi-supply) Joplin - 7.5 watt 2a3 DHT amp and an Spark SC1 pre-amp. Very smooth on this set up with EH tubes in the Spark.

The 500 hours test on drivers pulled from the first production run are averaging 84.5dB. Most users should get 84 to 85.4 in the CHR's service lifetime depending on how hard they're driven. In box, I would think around 85 to 86dB would be a reasonable expectation.

Can U put you're design on the thread with some pics? - good to help the new guys.

Will be interesting to read more on Dave's experiments.

I must admit to having much enjoyed the CHR design-build. One of those rare situations when a design mostly "flew off" the drawing board, still needing some hours of tweaking but nice work all the same.

Thx

Mark.
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Old 16th March 2009, 04:11 AM   #22
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Quote:
Originally posted by markaudio
Brain Cherry's (Diy-hifi-supply) Joplin - 7.5 watt 2a3 DHT amp
Its too bad he's not doing that anymore. It was my pick of his amps.

dave
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Old 16th March 2009, 06:05 AM   #23
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Sorry guys,
We are experiencing some technical problems with our web site (hopefully fixed soon)

Here's the CHR-70 information:

FO 70.0Hz
Imp 4.0 Ω
Revc 3.60 Ω
Sd 50 cm
Vas 3.61 litres
Mms 4.80g
Mmd 4.59g
Cms 1.00 m M/N
Qes 0.84
Qts 0.65
Qms 2.82
BL 3.10 T-M
Le-vc 27.44 H
No 0.16 %
SPL 85.0 dB-1/m
X-max (1 way) 4.5mm
Power 22 watts cont. (40 watts Max)
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Old 16th March 2009, 12:53 PM   #24
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is a folded 1/4 wrp possible for these drivers
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Old 16th March 2009, 03:19 PM   #25
Henkjan is offline Henkjan  Netherlands
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how about this?
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Old 16th March 2009, 04:04 PM   #26
chrisb is offline chrisb  Canada
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Quote:
Originally posted by planet10


Its too bad he's not doing that anymore. It was my pick of his amps.

dave

agreed - the Joplin was huge bang for the buck - maybe Brian could consider some sort of "half-kit / plans & parts" version



Quote:
Originally posted by bARTaudio
is a folded 1/4 wrp possible for these drivers

Quote:
Originally posted by Henkjan
how about this?

hopefully something a bit more adventuresome than that - who knows, perhaps even from the existing P10 design catalog


Mark: on further playing around with my systems on the weekend, it could well have been a combination of low signal output levels and amplifier input sensitivity that resulted in the 300B amps poor showing with the CHR70s, not necessarily the power level alone.


While it's certainly not the most transparent and refined of my tube amps, the Jolida has a high gain input, and when connected in triode without the 5dB of NFB, lots of personality and torque. It has no trouble at all in rocking the little grey 70's.

25-30 watts should be more than enough, I just don't have a beefy enough SS amp of that power level to play with - the little Kingrex T20 didn't quite do it for me with these.
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Old 18th March 2009, 12:47 PM   #27
tresch is offline tresch  United States
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Hey Mr. Mark! Gotta say, I love the speakers so far. My next project is going to be building an LM1875-based amp to drive them, and I'm fairly excited to see how that will sound.

It's good to hear that you had a lot of fun designing these, as I think they hit a really nice price-to-performance sweet spot for us that appreciate great sound but may not have the money, need, or even available listening environment required for full-on audiophile levels of discrimination.

I'm not sure if I speak for anyone else, but I'm really curious if you plan on expanding on the CHR line. Personally, I would love to see something like a 6-ohm CHR-10, or maybe even a 6 ohm version of the CHR-7 that would be better matched for your standard Home Theater amplifier/receiver. I would totally love to build a 5.1 or 7.1 setup with these little guys, but I've been having difficulty figuring out the best way to power them, as most HT receivers are not rated for 4ohms.

I could always just add some artificial resistance with resistors at the speakers, but I can't decide whether that's a cop-out or a valid approach. Does that tend to affect sound quality much?
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Old 18th March 2009, 01:21 PM   #28
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Hi T,
Good to read your message ad glad you're enjoying the music!
Yes, I've had the desire for a long time to build a driver that can perform for audiophiles, new builders and home theatre fans, without breaking the bank.

Ummmmmph, I think you've been reading mind. Here's a sneak preview pic of the next generation.

Where there's a powerful amp in use, I'd recommend using a decent quality resistor in the feed to a driver to better balance the load. Don't want to accidentally over-load a smaller size driver.

There's some info on using 2 CHR's in series on the CHR-70 thread in Vendors Bazaar. There's a pic and a graph showing what results can be achieved, useful when thinking about H. Theatre speaker plans.

Have fun!

Mark.
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Old 18th March 2009, 02:34 PM   #29
tresch is offline tresch  United States
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Quote:
There's some info on using 2 CHR's in series on the CHR-70 thread in Vendors Bazaar.
Always an option, of course, but if you need to get two drivers for each speaker, that's a lot of extra money just to bring up the impedance for the amplifier! of course you do get more SPL and power handling, as well, but frankly these get plenty loud by themselves, and unless you're trying to shake the house, one should be plenty!
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Old 18th March 2009, 04:59 PM   #30
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I've never had any problems running 4 Ohm speakers with normal HT receivers. I think you'll be better than fine with just one CHR-70 per channel.
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