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HOW DUMB/ DANGEROUS IS THIS?

johnnyblue

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Nov 3, 2008
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I've recently bought a ca640a amp to pair with my 640c and ae evo 1 floorstanders. It's a great combination with some cds but with others it's far too bright at the top end, painfully so on some tracks. I've tried turning the treble down, moving the speakers round and even bi-wired them, but no difference. So, today as an experiment I wired the hf left & right to a pair of celestion f1's I have and the lf l&r to the evo's. In other words the bass comes out the evos and the treble out the celestions. There's no denying that there's a trade-off in sound quality at the top end, but the brightness is gone and I can play just about everything I've tried at a high-ish volume,between 10 and 12 on the dial.

My question is - am I damaging the amp as it is effectively only driving one pair of speakers? It certainly doesn't feel any hotter after a couple of hours continious play at reasonably high volumes.
 

The_Lhc

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Oct 16, 2008
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If the combined (read average) impedence of the speakers isn't lower than what the amp can handle then you could wire both sets of speakers to the amp without any trouble. That will depend on both the speakers and the amp in question of course and without know the numbers it's impossible to say.
 

johnnyblue

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Nov 3, 2008
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Thanks for the quick reply. The acoustic energys are actually evo 3s and both pairs of speakers are 8 ohms and the amp is 75w at 8 ohms, so I guess it should be okay.

Assuming nobody else posts to say I must be mad all I've got to do now is decide which sound I prefer - oh, and convice my wife that four foot high speakers are actually quite an attractive feature in the living room.
 
A

Anonymous

Guest
If it were simple resistance (rather than impedance) then two 8-ohm speakers in parallel:

------SPEAKER-----
Ý Ý
Ý Ý
-----SPEAKER-----
Ý Ý
Ý Ý
Amp+ Amp-

Which is effectively what you are doing by the sound of it.

This gives a resistance R = 1/(1/8 + 1/8) = 4 ohms, i.e. twin 8 ohms wired in parallel are equivalent to a 4 ohm single speaker.

Okay with capacitance and inductance and all it gets more complicated, but you're basically still presenting about a 4 ohm speaker.

If you "daisy chain" the speakers you present a 16 ohm load.

Therefore you should check your amp's compatibility with 4-ohm speakers as putting X volts across them will draw twice as much current through a 4 ohm load compared to an 8 ohm load and could therefore burn something out (heat generation is proportional to current, not directly to voltage).
 

Andrew Everard

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May 30, 2007
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Trouble is, I imagine it'd sound pretty horrid, as the crossover points in the two speakers will be different, so you'll either have a hole in the frequency response or too much reinforcement in the midband somewhere.

And that's without considering the different characteristics of the drivers.

So I'd say not dangerous, but borderline dumb
 

johnnyblue

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Nov 3, 2008
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Andrew - Before I did this I looked it up on the internet and couldn't find one match for anyone else ever having done it so I knew it was probably borderline dumb at the least, but only borderline's probably an improvement for me.

Darren Heal - The amp is only driving one set of treble (celestions) and one of bass and middle (evo 3s) so does that apply?
 

johnnyblue

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Nov 3, 2008
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Any advice on other methods of lessening the brightness would be appreciated. The evo 3s are certainly not thought to be bright and I've never found them particularly so before, so I thought they'd be good partners for the CA kit. The trouble is the nearest hifi shop is about 20 miles away and the nearest Richer Sounds is 25 miles and doesn't have a listening room so not a great chance of auditioning stuff.
 
A

Anonymous

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johnnyblue:

Darren Heal - The amp is only driving one set of treble (celestions) and one of bass and middle (evo 3s) so does that apply?

Without a circuit diagram and a morning to do the sums, not to mention remembering how to do them (it's been 25 years since my last electrical engineering class), I can't be sure. HOWEVER, if the impedance of the speakers isn't changed from 8 ohms by bi-wiring idividual pairs properly, I would assume yes. You're probably going to be okay if you don't crank the volume up past half-way, but I'd still be wary.
 

johnnyblue

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Nov 3, 2008
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Thanks for that. Believe me I am wary otherwise I wouldn't have posted on here and opened myself up to having people realise how "borderline dumb" I can be.


I'd still appreciate any suggestions for lessening the brightness if anyone's got any. Andrew?
 

Andrew Everard

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May 30, 2007
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johnnyblue:I'd still appreciate any suggestions for lessening the brightness if anyone's got any. Andrew?

With the set-up you now have, not a clue...
 

johnnyblue

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Nov 3, 2008
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"I'd still appreciate any suggestions for lessening the brightness if anyone's got any. Andrew?"

Minus the celestions, of course.
 

Craig M.

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Mar 20, 2008
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does it still sound bright when you use the other speakers on their own?

if not then you have your answer. or change components to suit your evo 3s?

or maybe it's the way the bright cds were mastered?

how is your room furnished? laminate flooring and a minimalist room with painted walls wouldn't help.
 

johnnyblue

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Nov 3, 2008
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JohnDuncan

Direct doesn't make a discernable difference and the bass and treble controls have the least effect I have ever encountered on an amp. At first I thought they might not be working, but eventually after listening very carefully I was able to hear that there was a tiny difference in sound.

CraigM.

The trouble is the Celestions aren't much cop. The room is carpeted, curtained and has a very large sofa in it - but also a pretty big coffee table too and half the back wall is lined with cds. So I'm going to try disconnecting the Celestions (it was only a crazy experiment) and moving the Evos around again. I think you're right about the mastering though. And the original production too. What made me try hooking up the second pair of speakers was that I played the first Stephen Stills solo album and it sounded great except for Love The One You're With on which the drummer is hitting something that was so sharp I had to skip to the next track, and Go Back Home which was fine until Clapton's solo comes in at which point I was in danger of being prosecuted for possesion of an instrument of torture.

Andrew.

The biggest change in sound, aside from the fact that the Celestions are not as revealing as the Evos, is that the bass has lost a fair bit of tautness, which is one of the really nice things about the ca equipment.

Ah well, worth a try (but only if you've got time on your hands and don't mind looking an idiot) but back to the drawing board. I'll let you know how I get on as I think a few others might have the same problem to lesser or greater degrees.
 

johnnyblue

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Nov 3, 2008
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Well, I've tried everyone's suggestions and I've managed to move the speakers a little further away from the walls and there is no real difference in sound. So, if anyone else is suffering from a system they feel is too bright I'm afraid I think thereare only two solutions, short of changing a main component, which is probably why so few people even made suggestions or had any ideas.

Overall, I'd say the brightness is down to 3 things - some recordings are indeed very bright, particularly stuff from the Sixties, which the cd mastering only makes worse, and should not be played at high volume, although they are usually acceptable at anything up to 9 o clock on the dial.In such cases vinyl is far better.

The CA 640 amp and cdp are clearer and more detailed than my old Nad combo of 314 and 541i.

The other factor is my perception of whatever I'm listening to. If I'm listening out for brightness almost everything becomes too bright. I think it's very easy to colour your perception of what you're hearing. Which leads me to the second solution - stop listening so hard and just enjoy the music.
 

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