Mark Audio CHR-70 Application Thread

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Well, I promised pictures - but I'm afraid I got held up, so now the second box looks exactly like the first box pictured in my previous post. So you'll just have to look at that, but imagine two of them.

In the meantime, I've been breaking in the drivers in their rudimentary OB's on my desk - some observations:

a) These things have extraordinary excursion for a small driver - even OB bass is audible down to 40hz or so.

b) Off axis response is surprisingly good - while there's certainly a sweet spot, response seems quite good up to about 30 degrees off axis.

c) Imaging! The phantom centre effect with these speakers is extraordinary - with well mixed material, it often seems like a 1 foot high hologram of the lead singer has been projected onto my desk.

So far, very happy - this pair is for my girlfriend, but I have the timber for another pair, and I think they'll be headed for the loungeroom to replace a truly dismal set of late 80's Sony 3 ways.
 
Routed, the baffles are, hmm?
 

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Listening impressions on hold

Listening up until now (for those that haven't followed), in order of preference:
  • 6BM8 (ECL82), Single-ended based Philips receiver
  • Sanken based Teac reference 300 receiver/cdp
  • Nuforce Icon headphone amp/USB DAC/amplifier
  • Nakamichi SR-2 "Stasis" receiver

I think this could change. I need to try some resistors in series with the SS and Nuforce amps, and also with the McCormack DNA 0.5deLuxe. This needs to wait until I get some finish on them, as I'm sure if I don't now, I never will.

For now, I need to address the aesthetic considerations. I've decided to not veneer the enclosures. I think I'll use some grain sealer, then poly the front baffle, and perhaps stain the rest of the enclosure. I really like the exposed ply edges--I can't explain why.
 
Listening up until now (for those that haven't followed), in order of preference:
  • 6BM8 (ECL82), Single-ended based Philips receiver
  • Sanken based Teac reference 300 receiver/cdp
  • Nuforce Icon headphone amp/USB DAC/amplifier
  • Nakamichi SR-2 "Stasis" receiver

I think this could change. I need to try some resistors in series with the SS and Nuforce amps, and also with the McCormack DNA 0.5deLuxe. This needs to wait until I get some finish on them, as I'm sure if I don't now, I never will.

For now, I need to address the aesthetic considerations. I've decided to not veneer the enclosures. I think I'll use some grain sealer, then poly the front baffle, and perhaps stain the rest of the enclosure. I really like the exposed ply edges--I can't explain why.
I'm with you on the exposed ply edges Stew, provided they're straight & nicely finished, they look great. Yet another reason to use BB!
Don
 
OK went to three stores and my good friends lumber yard and no luck with ply.... Seems everything has a veneer with any of the good quality ply. That veneer layer causes some pretty bad glue joints. Any suggestions on any place close to the Greater Toronto area that carries baltic birch or quality apple ply? Anyone? TIA...
 
I wanted the MkII (2010) drivers, so I bought them direct from Mark Audio - cost me $125AUD shipped, the same as a pair of the 2009 revision from the local distributor.

I don't think there's a UK distributor at the moment, but I believe there's one in Germany which might save a little on shipping
 
Hi,
I've got question. Some time ago I bought CHR70 pair. Now it is time to do something with it. I thought about something like vented monitor(7-12l) with extra horn added(1,5m long throat 80mm2 mouth 800mm2). It will look like something at image ( it will be 150mm wide you can imagin it by extrude this profile). My question will this added horn help bass performance. Currently I work at FEM analysis. Image shows wave at 40Hz. I plan to form horn in thin plywood (first mechanical resonance mode is around 118Hz second around 200Hz but the deformation is almost zero so it is rather stiff). Post Your opinion about that idea:)
 

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Thanks Dave I'll look thru the thread and see if it helps a brother out. But I already called a few places locally that carry 5/8"(15mm) BB ply and they want $70 per 5x5 sheet, I need to build two cabinets as I have a few CHR-70's hanging around and figure $140 for ply is just a tad too rich for my blood.

Any suggestions for an alternate type of ply anyone, just seems a tad costly to build out of BB at $70/set of cabinets without veneer or finish. Using other building materials I could get 6 sets of cabinets for the same amount invested.

I had my friend look up the cost of BB at his yard and ordered in at "his" cost the ply is $38/sheet ordered in palette form. But he won't order a palette just for me and the two sheets I need LOL, too bad because he would give it to me at cost, $38 is alot easier to swallow than $70. In my 20+ years of lousdpeaker construction I've never used BB Ply, so maybe that's why the cost seems so prohibitive....

Any way I'm going to have these built ASAP, even if I have to do one set in BB ply and the others in MDF... :innocent:

Take care all...

 
Ideally, weld them up out of 10 ga. cold rolled steel (CRS) or Bamboo ply, but I imagine these aren't an option, so can you get marine grade at a decent price? Not that $70 for 19 mm BB ply is bad, it was ~ $62 at Home Depot/Lowe's around here ~ eight years ago......... Around here, $38 doesn't even buy a decent veneered 3/4" plywood.

Frankly, the last time I browsed Lowe's near me, the butcher block pieced together panels seemed to be at a sufficient quality, 'bang - buck' to warrant trying it out if/when I get to DIY any more box speakers.

GM
 
frugal-phile™
Joined 2001
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...just seems a tad costly to build out of BB at $70/set of cabinets without veneer or finish.


What price quality? We can get enuff free MDF to build these every day. It is well worth spending the money for the BB. $70 per sheet is on the high side of the market.

Check with John, (aka MJLxxxx), he may be able to help

dave
 
GM, maybe I should have made the $38/sheet a little more clear. That is a per unit COST wholesale to a lumber yard, but he must purchase a Palette to get this pricing... I'm aware of the cost of ply, too aware, as I spent most of the other night at HD, RONA LOWES and found nothing but utter crap. I like the idea off welded cold rolled cabinets LOL, but I'm getting older and as such would rather not tote 50lb cabinets around ;) .


Thanks Dave, I'll PM him... The BB ply was all 15mm 5x5 cabinet grade (no inclusions). I'd like to start cutting these this weekend if all things go as planned.
 
GM, maybe I should have made the $38/sheet a little more clear. That is a per unit COST wholesale to a lumber yard, but he must purchase a Palette to get this pricing... I'm aware of the cost of ply, too aware, as I spent most of the other night at HD, RONA LOWES and found nothing but utter crap. I like the idea off welded cold rolled cabinets LOL, but I'm getting older and as such would rather not tote 50lb cabinets around ;) .


Thanks Dave, I'll PM him... The BB ply was all 15mm 5x5 cabinet grade (no inclusions). I'd like to start cutting these this weekend if all things go as planned.


I've been working for a commercial architectural millwork business for over 17yrs now, and have been enjoying trade / jobber pricing for so long that all retail figures on building supplies seem somewhat usurious.

The above noted price is actually slightly higher than I paid for my last partial lift (13 sheets) of 15mm BB.

If cross country shipping costs on cut parts weren't so high, someone in this position could help a brother out ........
 
OK I was able to get some nice B grade 15mm baltic birch for my DMar-ken's which looks fairly good with 11 uniform plys. Going to cut the wood tommorrow if the rain holds off long enough. Have to grab some 3/8" solid wood stock and I'm going to skip brads this round and I'm going to glue and clamp. Might take longer but in the end will require less prep time for final finishing with veneer. So here goes nuttin'....
 
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