To Bridge Or Not To Bridge

Hey guys, not so fast!
A bridged amp is effectively two amps wired in series, one amp has inverted phase, so each amp is half of a bridged push-pull "composite amp".
This doubles the available output voltage, NOT the current.
Since Power = V squared/impedance, bridged power is quadrupled into 8 ohms.
However, if each non-bridged amp is specified to drive a 4 ohm minimum load, two amps in series will drive confortably 8 ohms (4+4), nothing lower than that.
Otherwise a bridged amp would be contradicting the laws of electricity.

To double the current and be able to drive half the impedance load, we need amps connected in paralell, and that's exactly how most manufacturers scale up the power: by adding more transistors in paralell at the output stage.
Load impedance is the main crippling factor of bridged amps: they have lots of theoretical power, however, for those amps that I have auditioned, bridged amps have a hard time driving current-hungry speakers.

In your case, the ideal solution would be vertical bi-amping, one amplifier for the bass, one for the remaining drivers, if only Thiel made bi-wired speakers!

Well, an email from Krell customer service contradicts what Bret told me.

I guess the answer is Not To Bridge.

Maybe I should run some speakers to the porch...

Schipo - I am not worthy!

Almarg, that was my concern as well. I don't see anything confidence inspiring in the manual either. But Bret D'Agostino said it would be fine. I'll call again to double check, I don't have the bridging wires anyway it turns out.

Douglas, the KAV-500 is lifeless and monotonous in my opinion. But its just fine for HT which is why I don't swap it out. The Classe has lots of synergy with the older Thiel 1.5s as many before me have discovered. Also, the power of the Classe is 400W@4O and the Bridged Krell is 400W@4O so you must be thinking of a different amp when you say there is more power.

Schipo -- ROTFLOL!!!

Leo -- Bob R. makes an excellent point. In bridged mode an amp will see the speaker impedance x 0.5. The Thiel is rated as 4 ohm nominal, 3 ohms minimum. Therefore in bridged mode the amp will see 2 ohms nominal, 1.5 ohms min. I looked at the amp manual, http://www.krellonline.com/archive_pdfs/KAV500/KAV500_V990_MAN.pdf, and I see nothing that provides confidence that the amp will be able to handle that acceptably.

Regards,
-- Al

P.S. If you're concerned regarding the inefficiency of the Theil speakers and the capacity of the bridged KAV to drive them, give Theil a call. Better to be cautious. It's likely there is no issue, but best to be informed.

You may even consider trying to bridge the KAV's four channels to two, then trying them out as power to the main L/R speakers!

I saw your comments, displeasure with the KAV, however it may be better than the Classe two channel amp you're using now, especially since the power will increase substantially through bridging. That has a huge effect on what is perceived as "quality" sound. Only way to know is to try. There are so many things happening tonally, etc. that no one can tell you definitively that you won't like it better. It'll take some time, but the payoff could be good. You would still have one channel remaining for center, and you'd have perfect consistency in amplification across the front rather than different manufacturers. The Classe then could be put to work on the rears. If it doesn't pan out you've lost nothing. If it does, you've upgraded for free.

I would think this could be a very interesting comparison for you. It certainly should not be written off. This is the kind of futzing around with equipment which will separate you as an audiophile from the weekend hacks. ;)

I called Krell and they said 4-Ohm would be no problem. I guess I'll try it then. Thanks.

Buff, it powers the rear surrounds and the center. Left and right are powered by a different amp.

Schipo, er?

To Bridge or not to Bridge that is the question:
Whether 'tis nobler in the mind to suffer
bad sound with tinny highs and boomy bass or to spend an outrageous fortune cleaning it up by Bridging your amps.
Or to take up your entire system against a sea of troubles,
And by opposing the purchase to buy newer equiptment? To die: to sleep and listen no more to a bad sound system.
No more; and by a sleep to say we end by removing that one troubling piece of gear,
The heart-ache of removing it and the thousand natural shocks of electricity because you forgot to unplug the amps.
That flesh is fried to a complete crisp 'tis a consummation
Devoutly to be wish'd that I turned the power off instead. To die, to sleep;
To sleep: perchance to dream and wake to a better Stereo seperation ay, there's the rub;It's not my gear at all BUT THE ROOM.

Why not bridge 4 of 5 channels to give more power to L and R and leave center as is?