I've tried this with Magnepan 3.5Rs, but it requires an active XO. The Behringers and DBXs are cheap, but CRAP. I had 4 blow up before throwing in the towel on the 3.5Rs
I don't see how it could done effectively passively, without crossing out the bass on one and the treble on the other
I discussed with monitor audio and they advised against active cross over and I am not into it either. They did mention that the best results, will be with passive biamp.
What are the amp specs that needs to be matched (or closely matched). Is
it gain, input sensitivity, input impedance, watts per channel.
Gain must be matched precisely.
Can I ask a question? What do you hope to get that you are not getting now?
The gain of my current amp is 29 db, input sensitivity is 1.4 volts RMS, impedance is 7.5 kohm, damping factor (at 8 ohm) >1000, power output 250 watts at 8 ohms.
I am considering Luxman M-900u, which also has gain of 29 db, input sensitivity of 1.24V/150W (8ohm), input impedance of 34 kohms (balanced), damping factor of 710, power output 150 watts at 8 ohms.
The gain seems to be matched and input sensitivity seems to be close (even though different watts power at 8 ohms). Will this be acceptable for biamp with my current amp ?.
Yes close, you may not need the Sys, but get it anyway as it comes with a trial period, so you can send it back, it is only $49
If it’s on the bass amp, then you "can" raise it slightly for those "bass shy albums", or lower it slightly if it’s on the treble amp.
And yes I’m also against active bi-amping as it sterilizes the mids and highs, it’s ok on the bass though and use the speakers passive xover on the mids and highs.
@yogiboy and @Georgehifi.
Thanks for those suggestions. I would rather not do that, unless that is the only option. But, in the meanwhile, I will dig deep into this.
The thing to keep in mind, with amps, is that the gain specification measurement is just not that important to makers.
That is, maybe they will specify 29 dB but maybe it’s 28.5 and maybe it’s 29.7. It's rarely 29.00 dB
Since 99.9999 of their customers will use 1 stereo amp, accuracy here is just not that important. I’m sure it is consistent among the same model but across different models or makers probably not.
So, good to have some way of measuring the relative gain and adjusting if wrong.
let’s say if it is few decibels apart, how much of the impact will this have. In other words, if they are apart, how will the sound quality be affected. Will it be like one amp sounds more than other one ? Or will it affect the coherency in the music ?
A few decibels is actually a LOT! The difference between 29 db and 32 db means that you would have either too much bass or very weak bass depending on what amp you put on the bottom.
If Erik is correct that gain is not always 100% perfect specification, then the variance might be small. A .7 decibel variance is not that much, but I wouldn't say it's that bad. Speakers are never perfect anyway and actually will vary up to 3-5 decibels through the entire frequency range.
If you put a amp on the woofer that is .7 db higher gain, you might have a "slightly thicker" bass midbass. It's almost like a very slight EQ.
I would ignore those "1.24V" sensitivity numbers. It is just a representation of how much input volts are required to have the amp output a certain amount. The "gain" is the only thing you need to look at.
Sounds good. Thanks for those technical inputs. I am assuming, even if the companies mention 29 db gain, they may vary at best few decimal of decibels. I am OK with that.
Just one question though. It may be silly. Does it matter even if the amp have different watts of power (like 250 vs 150 at 8 ohms) even if gain is same.
A few decibels is completely noticeable!! :) You would be changing the sound of the speaker completely. Dude, if you are OK with that, then go with active bi-amping instead. You’ll get more control, more dynamic range and can fix your level mismatches.
Understood, as I said, the two amps which I stated will have same gain of 29 db. So, I will go with it.