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Old 21st April 2011, 06:13 PM   #521
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by Poultrygeist View Post
I've built two pair of Mk3's using the 126En in 18 mm MDF cabinets. I'm thinking of trying the CHR-70 in one pair but have the following questions:

1. Is the CHR-70 a direct drop in replacement for the 126En and will it cover the holes drilled for the 126En?
If cutout is precise and not rebated for flush mount, yes it would "drop in" . However the round flange of the CHR is not wide enough to reach holes drilled for the pincushion shaped frame of any of the Fostex drivers of this size. You could of course fill the screw holes with dowels or wood filler. The other big "but" is difference in sensitivity. The smoother FR and deeper LF extension of the Mark Audio driver aside, there's no getting around the substantial difference in sensitivity (well over 6dB). Which brings us to the next question:

Quote:

2. The 126En Mk3's sound wonderful with my new 2a3 amp but will it's 6 watts be enough for the CHR-70's playing small group jazz at low to moderate levels in a 15X15 room?

Thanks in advance for your input.
What 2A3 amp do you have that delivers 6 watts (or is that both channels?)

The approx 3watts I'm getting from my Bottlehead Paramours or DIY class A EL84 P/P would certainly be adequate for FE126E, and quite acceptable for FE127E and dual driver EL70, but could be borderline in terms of dynamics and bass impact with single CHR70. Only your ears can answer that one


Quote:
Originally Posted by lavanta View Post
My bad, it is the Alpair 7. It was my senior moment.
That makes more sense, my earlier recommendations for tube amp "kits" still apply - I've heard/owned more than a few DHTs, but am still a big fan of the still relatively affordable and widely available EL84/6BQ5 family. Of course there are lots of other options, including some rather reasonably priced commercial products - Jolida FX10, Shuguang I-12, etc., - which are inexpensive enough to be modified / tarted up with tube rolling / parts upgrades, and other posters will have their own suggestions / favorites.

Rather like with (building) speakers - unless you have opportunity to hear the exact model under discussion, preferably in your own or very familiar venue, any decision based on recommendations or printed reviews alone is a big leap of faith. Of many such I've made in the past 10yrs or so, only a couple have been major disappointments, and aside from financial loss on resale / trade etc., (always part of the learning curve), none unqualified disasters.
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Last edited by chrisb; 21st April 2011 at 06:18 PM.
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Old 21st April 2011, 07:16 PM   #522
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Quote:
Originally Posted by planet10 View Post
And if some of you are wondering where we are coming from or what we are talking about, here is the original concept which was modified in the interests of ease of build. Even if you have a tenon jig, not many saws will give you 6" of blade to cut with

dave
What dimension(s) were changed to compensate for the double-thickness material in the image above?

Just a slightly deeper cabinet? I'm assuming the angle remained the same.

*edit: whoops, what image above... Original choke implementation post

Last edited by grimmrok; 21st April 2011 at 07:29 PM.
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Old 21st April 2011, 08:16 PM   #523
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by grimmrok View Post
What dimension(s) were changed to compensate for the double-thickness material in the image above?

Just a slightly deeper cabinet? I'm assuming the angle remained the same.

*edit: whoops, what image above... Original choke implementation post
Yes, the angles remain the same ( 5dg).

What we finally ended with for the flat pak production was per attached.

By using 1/2" roundover router bit on the adjoining ends of internal divider and rear panel, the height of angle cut is substantially reduced, and the need to hand cut sharp corners in CNC routed dadoes was eliminated. I cut the rear panels with tenoning jig on table saw with blade set to 5dg angle, but there are certainly other methods to remove the small amount of material.
Attached Files
File Type: pdf FH3choke_detail.pdf (4.8 KB, 122 views)
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Old 21st April 2011, 08:50 PM   #524
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Hi Chris,

Thanks for that. Nice and simple solution.

I'd love to make a pair of these but the cost of good ply here is rather prohibitive as the only source of void free material I've traced so far (locally) is marine or aircraft grade ply.

Good luck to those who're taking the plunge though!
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Old 21st April 2011, 09:00 PM   #525
chrisb is offline chrisb  Canada
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Originally Posted by grimmrok View Post
Hi Chris,

Thanks for that. Nice and simple solution.

I'd love to make a pair of these but the cost of good ply here is rather prohibitive as the only source of void free material I've traced so far (locally) is marine or aircraft grade ply.

Good luck to those who're taking the plunge though!

you could always try particle board - sonically preferable to MDF, but of course not as easy to paint
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Old 21st April 2011, 09:15 PM   #526
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Chipboard wont degrade the SQ too much? If that is the case then I'd build them. Painting wouldn't be a problem as the'll be veneered I've got some lovely jarrah leaves in the shed but that wont suit a black EL70 as much as the off-white/beige of the CHP's!

Come to think of it, I'd get to use my nice new plane on the shooting board. You may know of the make, Veritas Lovely piece of kit and half as expensive for a tenth less tool than Lie-Nielson!
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Old 21st April 2011, 10:05 PM   #527
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by grimmrok View Post
Chipboard wont degrade the SQ too much? If that is the case then I'd build them. Painting wouldn't be a problem as the'll be veneered I've got some lovely jarrah leaves in the shed but that wont suit a black EL70 as much as the off-white/beige of the CHP's!

Come to think of it, I'd get to use my nice new plane on the shooting board. You may know of the make, Veritas Lovely piece of kit and half as expensive for a tenth less tool than Lie-Nielson!

From the few experiments I've made, the particle or chip board definitely sounds "faster / more musical" than MDF.

Some folks have even used OSB - but I've pretty sure that none of the projects I've heard were with that.

The Veritas certainly are gorgeously enough made for most hackers - I'd be afraid to pick up a Lie Nielsen tool.
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Old 22nd April 2011, 12:17 AM   #528
lavanta is offline lavanta  United States
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Thanks for your suggestions Chris. Sometimes you have to make a leap of faith and go with the suggestions. Time to keep an eye on AudiogoN listings. Looks like I need around 15W/channel, Triode Electronics Dyna ST35 would fit the bill. Might make a wooden base to match my Bottlehead Crack.

Regards
Levent
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Old 22nd April 2011, 12:39 AM   #529
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So is it worth offering flat packs in ply, 18mm MDF and particle board? or would you rather they weren't offered in MDF?
I definitely notice a difference between the ply and MDF but not nearly 5x the price worth.
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Old 22nd April 2011, 01:30 AM   #530
Bigun is offline Bigun  Canada
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for me it's not just about the sound. If I'm going to the effort of building a speaker I want to be able to look at it in the future and feel good about the construction. I personally would find it more satisfying to have used good quality ply. I think it's a better quality material all round.
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