Bi-amping with 2 250s or 135s or Both?

Posted by: Alex S. on 01 August 2001

I have been told by a surprising number outside this forum that bi-amping 250s does/should sound better than 135s (with N805s). Having 2 250s already I very much hoped this was true since I would thus be spared another upgrade path. Nonetheless, some spare time and curiosity combined to get the better of me and I went to have a listen. Sadly, it is not so, 135s outperform 250s by some margin - much more space and instrumental separation, hold on to notes much better, sound less forced, especially at high volume. Nonethless when conventionally bi-amping with 250s (ie treble with one, bass/mid with the other) they do excel in the treble. For example, the piano and trumpet in the final movement of Shostokovich Piano No 1 sounded very sweet and dynamic.

So perhaps one should put a 250 on the treble and use a 135 on each bass/midrange. Having made this suggestion my dealer politely showed me the door.

Posted on: 02 August 2001 by Pierre Isabelle
I am using this combination (with SNAXO and SBL's) and I am very happy with it. A couple of years ago, I replaced the 250 I was using for the woofers by a pair of 135's and that made a tremendous improvement.

I am not sure how much better things would get by replacing the remaining 250 with another pair of 135's. I am probably going to try it some day, but I would rather improve some other things first.

-- Pierre

Posted on: 02 August 2001 by Duncan Fullerton
Years ago I fired off an e-mail to Naim asking this same question ... if the gain of 135's and 250's is the same can I mix and match. The answer was "yes", but give the 135's to the treble and the 250's to to other drivers."

Has anyone got/tried a mixed 135/250 system, and have they tried changing the amps round?

I guess that on first sight, we would give the bigger current devices (the midrange/bass drivers) the bigger amps. But maybe the theory goes that the ears are more critical of changes/errors at higher frequencies so you want to give more control (i.e. 135's) to those.

Discuss and debate ...

Posted on: 02 August 2001 by Alex S.
The reason I thought of a 250 on the treble is because it seemed totally in control of my tweeters whilst it took 135s to have the same degree of control over the bass/mid.

I do know that the debate rages over where to put your "better" amp, generally I would favour the treble for the reasons you state. Nonetheless, perhaps stating the obvious, a 250 on the treble and a 110 on bass/mid may not be appropriate (actually I've tried this for fun and it sounded surprisingly good but I was fearful of blowing up the 110).

I don't wish to purchase 4 135s.

Posted on: 02 August 2001 by Phil Sparks
quote:
Did you try 2X250 in mono mode by any chance? I have heard that this is possible but do not know anything about how its done.

There are a number of stages in trying this out -
the easiest is (assuming yu've got a HiCap or SCap with multiple outputs) to send the same output to each amp but just plug the left hand speaker into the left output on one amp and the right hand into the other amp. The theory being that each amp (and more importantly the power supply in each amp) is working only half as hard, hence better sound. The downside is that the preamp is driving 2 power amps, ie. half the impedance. I tried this for a few weeks before I got round to pulling my kans apart to take them active and thought it was significantly better than just one 250

The more involved stage is to pull the sleeves off the 250s and disconnect the one input cable from the XLR and one power supply cable from the same amp board. This way you really do get almost a 135.

Phil

Posted on: 02 August 2001 by Alex S.
quote:
This way you really do get almost a 135.

It would make sense since each amp would have an equal load. I haven't tried it since everyone I've asked says its not worth the bother, ie. you don't really get close to a 135.

Jonathan - I'm not a plink-plonk etc head - Mozart has too many notes - but to continue tweetering on, the theory is that all notes' leading edges are developed in the higher frequencies/tweeter and therefore one's quality should be there. Nonetheless, when playing at bi-amping with a 250 and a 110 I noticed that a 250 worked best on the tweeters at low volumes but, pump it up and the 110 overheated and lost all control of the bass/mid. Thus for my normal 10.30 listening position I reverted to 110 driving the tweeters. This was marginally better than a single 250 doing the lot.

My theory for 250/tweeters, 135s/bass-mid is based on the characteristics of both amps - the 250 has lots of drive and in your face exitement and thus may be well suited to providing the leading edges of notes whilst the poise, control and transparency of the 135s may be better suited to the bass/midrange.

I am aware that my theory may be utter rubbish, but I'm still going to force my dealer to demonstrate. Maybe the synergy will be lost if both amps are combined - perhaps I'm back to 4 135s.

Posted on: 02 August 2001 by Duncan Fullerton
quote:
I am aware that my theory may be utter rubbish, but I'm still going to force my dealer to demonstrate. Maybe the synergy will be lost if both amps are combined - perhaps I'm back to 4 135s.

Alex, if you've persuaded your dealer to demo four mixed boxes, get him to do it both ways up so we can see whether the "oomph" or the "edge" theory works best.

I'm in the same boat. I have a pair of 135's and 6 hungry drives to feed.

Posted on: 03 August 2001 by Alex S.
Seems to be a straight contest then between treble hash and bass splodge, or spending lots more money - the usual Naim solution.
Posted on: 03 August 2001 by Alex S.
No more dems quite yet (need to pay dealer the balance due on CDS2 before he relays welcome mat).

BTW how has all your Mana bedded in?