Should I bi-amp or bridge my amps to feed my speakers

I love AP speakers.  Sounds like you may be talking about the original Virgos?  If so, here’s what JA had to say about them in the “Measurements” section in that review…

The Audio Physic Virgo is a reasonably hard load for an amplifier to drive, as shown by its plots of impedance magnitude and phase against frequency (fig.1). Not only does the impedance drop below 4 ohms for pretty much the entire midrange, but the phase angle is also moderately high in the upper bass and low treble.

If this is the case I’d certainly try bi-amping as there’s no chance either amp in triode mode will drive them sufficiently unless you’re in a small room listening at low volumes, and even then it’s probably a big stretch.  If you’ve got the amps just try it — it’s free and you’ve got nothing to lose and maybe a lot to gain.

Bi amping with keep the upper frequencies from getting clipped, and more sore if there is some active XO happening.

So I would bi-amp with an active XO, or some active XO type of filter, if been a Harrison Labs RCA job.

But bridging is probably better if you need more woofer notes.

Have you considered a subwoofer, and using some filter to scrape off the low notes so that the speaker do not need the amp to play them loudly?

If they are mono amps then you have to run one amp per speakers.

if they are stereo amps are you sure they are capable of bridging? 

i will assume they are stereo amps, i wold try one amp for the left and right woofers

and one for the mids and highs. 

clipping should not be an issue because tube amps soft clip, they just run out of steam.   

I vote for adding SS amp good for high current for the woofers; use the tubes as mono blocks for the tweets/mids

I should have mentioned the tube amps are in stereo they’re  HK citation 2’s. They have both been rebuilt. Also speakers are Virgo's the first series 4 ohm. Soix got it right!!

i have considered a small sub woofer, but haven’t made a move on it. 

In your situation you could use one amp for the woofers and one for the mid/treble or you could  use a single amp each for the L and R speaker.  I would try both ways. 

Bridging allows for greater watts at the expense of current. Not good for low impedance speakers. 

I would be concerned about the power compatibility of those amps with that speaker even using both amps. What is size of room? 

Which amp were you planning to bridge? Stereo tube amps aren’t usually bridged; their sides are run in parallel for mono. My VAC 200iQ tube amps are like this, and it results in a huge upgrade in performance (at the cost of 2 amps versus 1). I’ve tried bridging a SS amp I really love (Phison A2.120SE), and it honestly sounds better in stereo mode. Bridging is much more tricky, and more likely to degrade sonic performance for the extra power.

I tried bi-amping instead of bridging SS amps, and that was fun but nothing life changing. Tried both vertical and horizontal bi-amp. You need identical amps for vertical, and (at least) gain matching for horizontal. I simply still prefer to run that amp in stereo (single amp). Biggest difference I’ve heard so far was running the tube amps in mono/parallel mode (haven’t tried bi-amping them).

@kellymack,

Should I bi-amp or bridge my amps to feed my speakers

I would bi-amp. That said it should not be undertaken without first asking the manufacturer’s advice.

When I horizontally bi-amped my speakers with an analog active crossover design by the same manufacturer (of the speakers) it brought my speakers three notches above the passive crossover in sound quality. 😎

Mike

See Active Vs. Passive Crossovers (sound-au.com)

i have considered a small sub woofer, but haven’t made a move on it. 

@kellymack ^That^ often gives the most boost.

And if done right it is more like bi-amping… Basically the sub notes get largely  striped off, from the main speakers.

if you already had two stereo amps, then just try it, but $ for $ a sub is usually the most effective.

@kellymack 

You are on the right track getting a sub. 35 watts is probably not enough to take care of the entire bottom end, but if you roll them off at say 80hz to a subwoofer or two will amaze you!  If you go with REL or similar, that use your amps speaker feed, you shouldn’t need anything else. They can control where the speakers roll off and the subs roll in.

Let us know what you decide to do.

I would not bridge your amps.  It forces two different output transformers to work in series. 

Bi-amp vertically...it should help with separation and soundstage. Add an active subwoofer to handle only the bottom octave. Set the low pass crossover on the sub at it’s lowest frequency, and set the gain so that you can barely even notice the sub.

You bridge your amps and you create a public address system from a stereo system.  It will be louder and it will sound poor.  If you want to bi-amp, that will likely yield better results.  Speaking from experience here.

I have heard those speakers with and without subs at a dealer in Portland and the spatial difference was not subtle. They were also spread farther apart from each other than "normal" and severely toed in. I don't remember which amps were driving them but I'm sure there was more power than the 35 wpc you are using.

I have heard those speakers with and without subs at a dealer in Portland and the spatial difference was not subtle. They were also spread farther apart from each other than "normal" and severely toed in. I don't remember which amps were driving them but I'm sure there was more power than the 35 wpc you are using.

I am not sure that we know that for sure…

The amount of power in the 20–80 Hz region depends on the music, and the system with the subwoofer May have been <35 wpc, and the sub well over 100 watts.

We sort of don’t know, but it is possible to significantly lower the amount of power by adding the sub.

@aewarren 
Can you further describe the “not subtle” difference?

The room is 14 x 20. This amp is already louder than I can handle. Once in a while I turn the volume up half way on my pre-amp. Sounds good, but don’t need it that loud. I just want a little more bass. I’ll try bi-amp ing this weekend. According to the manual bridging is straight forward and easy.

I feel like an idiot. I bi-amped my speakers this morning and it’s night and day difference, sound stage is more distinct and the speakers have disappeared.
 

@kellymack Did you end up using one amp to drive left and right bass drivers and the other amp to drive left and right mid/tweeter OR does each amp drive each speaker ( bass vs mid/tweeter split by channel)?   If you tried both, would be curious to know which you preferred. Thanks.

I did use one amp for left and right tweets and mids.

one amp for left and right woofers.

I didn’t bother bridging the amps, because I was real happy with the bi-amp configuration 

Glad it worked out so well for you.