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In Reply to: RE: Summer and Winter stereo power amps for QUAD 63 OR Sub/bass duty posted by Mr Peabody on April 05, 2016 at 14:13:34
I have decided to buy the Perreaux in time for next Summer. [I live in SE Australia inland in Canberra (ACT) nestled into the Great Dividing Range, and it's Autumn now. We are in sight of the extensive Winter snow fields, known as the Snowy Mountains.]I will use each of the two SS power amps I now have to drive the clam-shelled push-pull driver subs. That is, one 100w channel per bass driver. But, out of phase with that amp's other channel. I hope I will have enough level to allow the system to play loud enough for Beethoven and Berlioz. And, will live with any limitations on later louder works.
By Summer the subs will be built and tested to determine the Linkwitz Transform settings needed for each sub. A mono LT box for each sub - plus a 1/3rd octave for room Eq notching out peaks - in front of each bass/subs power amps.
I expect I may need different knee points to get a smooth blend, as I will start with asymmetric slopes 1st High Pass and 3rd LP at 150hz.
If I find I do need to push the LPass down a bit, I'm hoping that the
1/3rd-octave-eq boxes can help with any lump in the interim, until I change the knee points for the bass.That will take some time because the active xover I'm using in the bass has 2nd order slopes and fixed freqs, which might have to be changed by changing R's. I'd have to change the 1st order LPass input R and C on the bass amps in any case.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 04/05/16Follow Ups:
No problem, but it sounds like you have put a lot of planning and thought into your set up.
Because I read and think and revise, I usually avoid re-doing things before they've cost me.There have been two quite different notional projects for the final speakers before this one, too.
But, I have been thinking - and hoping - about 63s, and discussing it, for a long time. Beginning well before I was lent a pair of 63s just a few years back.
Asymmetric crossovers for - reinforcement of, and bass extension - under QUAD 63s, using omni bass sources (enclosures), isn't a new idea.
[Using OB dipoles is a lot more recent, and NOT cheap. And I've got all these bits which say 'do boxes.']
And, there are a few imponderables yet, if you will bear with me.
Will I end up using the subs for the lot @ 3rd LP from ~ 150/120 hz right on down to ELF, [or from 80 Hz and on down], and put the subs right beside the 63s?
OR do I build/adapt bass reinforcement (BR) boxes going down to 40Hz - to go right beside / under the QUADs? AND add subs just for ELF ~20-40 Hz and maybe put them in the two far corners (L-shaped room), phased to pressurise at the listening seats? Room-gain from corners is strong down low. LOTS of cables to vacuum around.I have enough spare drivers / speaker boxes, 35Hz spheres, and a spare 60WPC amp to do BR to ~35/40 Hz. In fact - this 40hz or so target, is where I will be starting.
If I did go with two bass systems with two boxes for each, I'd also need to buy/build an LR4LP/LR HP xover to feed the subs!!
When I have built the two subs - my tech and I will measure them, and IF I do find that the 1/3rd octave equalisers can't give me the extension I want below their Fc/F3s: to 20-25 Hz - I will apply LT Eq to match, yet retain the 1/3rd eq - to deal with room peaks, mostly.
So, quite a bit of measuring, and measuring in-room to do. And several phases to the project, so we can learn about the room and stuff.
200 watts per channel (400 watts total) just might be enough for 150 hz down to 20 or 30 Hz, even with LT eq, which does chew up power! Each big stereo power amp will be running OOPhase, so this might help their PSUs to cope a bit better when running hard.
IF I find that I prefer SS bass year round I'll keep the pentode 'Once was a LEAK St20' as a spare!
And I may even end up preferring the big Perreaux to the valve amp for driving the QUADs, year round.
Giving two 'Once were LEAKs', spare!! So far, I still doubt that I will. But it does get very hot here in Summer.
The valve pre will stay, though I/we will try to add a tilt type tone-control as in QUAD's own pre-amps.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 04/06/16 04/06/16
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