For the FH3, page 3 already has dim's for 18mm. Or, are you talking in general?
Well to be honest, there are often several generations of drawings, and I don't always see the final official plansets, so my apologies for any confusion. If Dave has released drawings specifying 18mm for all parts, then certainly use them.
Unless they're wrong
hmm, smilies not workin at the moment - that should be an ironic "EEK"
At least on the west coast, one needs to be even more wary of import Meranti, birch or other plywoods. Our commercial millwork company consumes well many thousands of sheets of various materials a year, and in this class we've seen not only high numbers of voids, unbalanced (in other words even) numbers of plys, serious delamination of glue joints, sand through on factory finished face veneers, and most significantly to this conversation thickness variations of well over .5mm - not only between sheets in a lift, but within the span of a single 4x8 sheet. This certainly makes life interesting when CADCAM cutting and machining depends on materials to be the actual dimensions at which they're spec'ed.
There's no politically delicate way to put it, these materials are almost always sourced from "the orient".
OTOH, I've used more than a few sheets of 3 ply Bamboo by Smith & Fong and others, and while it can be more challenging to work with than Baltic Birch, I've never had any such quality issues.
The discussion of plywood sourcing and sizing aught to be a sticky thread.
Here in the middle of the USA, all import (i.e. China) 3/4" plywood is 18mm and the quality of the stuff is from poor to OMG! Baltic birch is 18mm and the best grade I can get is BC. Cabinet grade veneered plywood is avaiable in true 3/4". Voids tend to be gaps between sheets in any given ply and rarely more than 1/4". This is my current choice in birch or maple because I don't consider the difference between this and BB to be worth the 120 mile round trip to Little Rock to get the BB. 12mm BB is available locally and this is what I use for smaller cabinets.
3/4" MDF is invariably 18mm. I have a lumber yard tha stocks MDF that is far superior (heavier) than what Lowe's/HD carries. I usually buy nominal 1"x12"x16' or 1"x15"x16' shelving because it is much easier to handle than 4'x8' sheets.
YMMV and probably will local to local.
Bob
Here in the middle of the USA, all import (i.e. China) 3/4" plywood is 18mm and the quality of the stuff is from poor to OMG! Baltic birch is 18mm and the best grade I can get is BC. Cabinet grade veneered plywood is avaiable in true 3/4". Voids tend to be gaps between sheets in any given ply and rarely more than 1/4". This is my current choice in birch or maple because I don't consider the difference between this and BB to be worth the 120 mile round trip to Little Rock to get the BB. 12mm BB is available locally and this is what I use for smaller cabinets.
3/4" MDF is invariably 18mm. I have a lumber yard tha stocks MDF that is far superior (heavier) than what Lowe's/HD carries. I usually buy nominal 1"x12"x16' or 1"x15"x16' shelving because it is much easier to handle than 4'x8' sheets.
YMMV and probably will local to local.
Bob
Mutating the FH Mk3 with a MiniDSP
Here's an idea for changing the FH Mk3 design to work in a larger room.
The WR125ST is a "kissin' cousin" to the FR - a bit more bass and a bit less treble, but with basically the same Sd. Otherwise the TS parameters are similar.
It seems to me that by using two (2) drivers you can certainly increase the SPL.
Using two identical WR125ST drivers will not require changes in the cabinet's profile geometry (taper, driver location, choke width, etc.), but the increase in cone area will require an increase in cross-section, so what we could do is increase the width of the cabinet. Guessing perhaps x1.8 (say). Logic: Twice the area of cone pushes twice the volume of air, so increase the x-sectional area by two.
"Combing" is the cry heard from the sages in the wings.
Well, because the WR125ST has a truncated frame, they can be mounted flat to flat, minimising the centre to centre distance, and therefore raising the frequency before onset of significant combing.
Bringing the MiniDSP into play could also assist by offloading all of the frequencies above the combing limit to one driver, with those frequencies EQ'd upwards to match the combined bass output of both drivers.
A supertweeter could be used if considered necessary. You may get away without one.
Comments anyone?
cheers
Doug
Here's an idea for changing the FH Mk3 design to work in a larger room.
The WR125ST is a "kissin' cousin" to the FR - a bit more bass and a bit less treble, but with basically the same Sd. Otherwise the TS parameters are similar.
It seems to me that by using two (2) drivers you can certainly increase the SPL.
Using two identical WR125ST drivers will not require changes in the cabinet's profile geometry (taper, driver location, choke width, etc.), but the increase in cone area will require an increase in cross-section, so what we could do is increase the width of the cabinet. Guessing perhaps x1.8 (say). Logic: Twice the area of cone pushes twice the volume of air, so increase the x-sectional area by two.
"Combing" is the cry heard from the sages in the wings.
Well, because the WR125ST has a truncated frame, they can be mounted flat to flat, minimising the centre to centre distance, and therefore raising the frequency before onset of significant combing.
Bringing the MiniDSP into play could also assist by offloading all of the frequencies above the combing limit to one driver, with those frequencies EQ'd upwards to match the combined bass output of both drivers.
A supertweeter could be used if considered necessary. You may get away without one.
Comments anyone?
cheers
Doug
Chris, what's your thoughts on a single FR125 in the Mk3? I'm tempted to get a pair... hmm...
Well it would certainly work, but having heard them flatulate in other vented designs ( bipole MLTL), I'd be concerned about excursion limits. For this enclosure, I'd be far more inclined to recommend the EL70 / CHP70, which I've yet to get to misbehave in the dual driver Castle microtower, or Fostex FE126En. Just thinking about it, the new Alpair6P could be another candidate for dual drivers in the FH3.
Greetings, my first post here.
A friend of mine and I am building two pairs of MK3s. One with FE126en (his) and another one with C7 (mine). I currently drive a pair of Rega RS3 speakers (89 dB) with Odyssey Khartago (110W/channel @8ohms) and I want to build a tube amp to drive the C7. What kind of power would you recommend given that C7 is 85dB? Room, rather kitchen with horrible acoustics, is 15 ft by 30 ft. Any DIY kit tube amp recommendations?
Regards
Levent
A friend of mine and I am building two pairs of MK3s. One with FE126en (his) and another one with C7 (mine). I currently drive a pair of Rega RS3 speakers (89 dB) with Odyssey Khartago (110W/channel @8ohms) and I want to build a tube amp to drive the C7. What kind of power would you recommend given that C7 is 85dB? Room, rather kitchen with horrible acoustics, is 15 ft by 30 ft. Any DIY kit tube amp recommendations?
Regards
Levent
pardon the senior's moment, but what driver is the C7?
As for tube amps, provided you're not looking for concert level SPLs in a kitchen and you think 15W or so would suffice, I can heartily recommend Tubelab SimplePP. Not a full kit, in that George can supply the board and small parts, but you need to supply iron, tubes and build the chassis. After a few teething problems, I'm quite loving mine.
Another option in a full kit would be the Triode Electronics Dyna ST35 kit, complete with their replica Dyna power and OPTs, and very nice chassis.
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?
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.
1. Is the CHR-70 a direct drop in replacement for the 126En and will it cover the holes drilled for the 126En?
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.