Passive Bi-Amping

Hi Shrink,

You've got a good point. Although I would say that it does partly depend what you define as midrange. Tweeters still do a lot of midrange work, especially if they have a low crossover point, say 1-2KHz. Or you could even be using a 3-way speaker but still bi-amping with mid/tweet on one amp and bass on another.

This is exactly why I didn't think of your above point. I wouldn't use the same amps on bass and treble duties if I had much choice about it. In my mind half the point of bi-amping is to specify your amps for the required job. I'd want massive raw power for the bass, and refined delicacy for the tweeters.

 

Two questions:

If using dissimilar amps as suggested above, how do you go about matching the levels?

Am I right in thinking that there are also digital active crossovers available and is this effectively a multi purpose crossover ie. it can be used with any set of speakers - the tricky bit being replicating the settings of the original passive crossover?

 

If using dissimilar amps it may be hard to match the outputs unless you stick with a particular range from one company. The amps I have are modular & designed to be used in passive polyamplification.

There are also digital active crossovers available but this is an active setup, different from the above. You are here introducing more components - active components - into the equation. If done right, passive has the advantage imo, as there is less in the signal path.

As a general point, you should always use the bigger amp on bass/midrange, substantially bigger, although some have said otherwise over the years. The problems mentioned by Shrink would otherwise make the whole exercise a waste of time.

Don't forget, it is not about using 'cheap' amps or 'expensive' - it is about musicality. A 'decent' 'expensive' amp can sound inferior to 'cheaper' amps if the implementation is wrong. If the amps are crap in the fist place it wont matter how many are used - 1 or 6, it still won't be any good. Passive Bi-amping is 'right;' because the amps can be faithful to musicality, as they have a less reactive load to cope with.

As regards to an amp being compromised because of dealing with bass & midrange, that is down to the designer of the loudspeaker and the load it presents to the amp (and not necessarily a lot to do efficiency on paper).

 

The gain has to be the same though the max output wattage can be different.

Bi-amping is by nature passive - if it is not passive it becomes active operation and is no longer bi-amping (by definition).

Bi-amping gives greater control, quantity if you like - it does not necessarily give you better quality.

 

Ah, but not enough quantity of quality will be an issue. I'd like both.

From what Tenson said I guess one could play compressed music & not worry too much about clipping anyway. BTW Tenson, you didn't say: are you referring to voltage clipping or current clipping?

 

Oh no! You said the evil word!

With the Kensai and Cyrus its probably mostly a lack of current. But it depends on the load impedance vs. frequency.

 

I experienced the same thing way back using an MF A3 integrated and an A3 power amp into Monitor Audio's.

Both amps blown away by a good tube amp though.

 

level matching is so easy my 9 year old could do it.

Just buy power amps with attenuators on the front, piece of pee.


I have a studio amp, 300b valve and el84 valve amp - all completely different power ratings and manufacturers. The studio amp is on the bass of course.

 

not a fan of mixing amps myself... as it brings its own problems.

As you increase volume, the rate of gain on two different amps will differ. They will produce different output volumes based on the input voltage, so you could only ever assure that they were volume matched at one particular level

Sounds like a lot of hassle to me. I'd rather just have one amp that worked well

 

Shrink, luckily it doesn't work like that. As an example an amp might have a gain of 4x, 6x, 8x etc.. (most have more). So if you had one amp with 4x gain and one of 8x gain, you just need to put a voltage divider of 2 on the higher gain amp. i.e a volume control with -6dB attenuation. So then whatever input you give it, both will give 4x gain.

 

Taken from Rega website.

"The power supply uses two generously rated toroidal transformers with 28,200mF of parallel connected smoothing capacitors, which will provide enough current to drive the hardest of loads."

Does this mean my amps are mono designs ?

 

exactly so! - the pre-amp is used for the 'global adjustment' once the various power amps are set at the right level.

 

Levi,

that in itself doesn't mean the amp is a mono/dual mono design or otherwise, it just refers to the power supply & its implementation.

"I currently use one for mid and treb, the other for base, although I have thought many a time to have one for the left speaker and the other for the right."

Your earlier quote indicates the amps are stereo amps, certainly not monoblocks. They may be dual mono designs though.

 

Hi Alan,

Good to hear of another NVA bi-amp system.. i've been recommended I go down this route myself. My current system is:

NVA P50sa > NVA A60.

Considering buying another power amp for the tweeters (or maybe even the A60 for tweeters, and a bigger amp for the mid/bass).

My speakers are also Royd (Abbots).

Was just a bit put off by the thought of making more space for another amp... but I guess by the sound of it its worth it !

By the way, are you AlanB on Hifiwigwam?? If so, how do your NVAs compare with your valve amp?

I changed from an Audion Sterling (modded) integrated to the NVAs.

Cheers

 

Hi Rockhopper,

No I'm not AlanB on Hifiwigwam - I'm Alan from Hifiwigwam (confusing isn't it)!

Didn't you start something in the review section there on NVA? I think I posted on it but the thread got removed. I don't post so much there as its hard to feel included when half your gear cannot be discussed as its designers are banned! (I've also got a Beresford DAC in my second source)...

Gromit once had a little NVA A30 which would be ideal with an A60 - you should ask him what happened to it. (there are also some trade in A70s on ebay...) Stick with stereo power amps if you want to keep the box count down.

Definitely try Bi-amping at least - it could really surprise you. Then get the word out so others give it a go. I think there is a lot of apprehension on the part of folk to try it, though in the old days it was more the norm. I know R Dunn recommends Bi-amping his amps, and Royds seem to love it too.

 

Hi Alan,

I did start that thread in wigwam yes, and it was removed by their admin, for reasons I wont go into here.

Despite some initial issues with my NVA amps, all matters were resolved in the end, and what im left is a cracking sound for relatively small outlay.

I'm definately gonna try biamping the Royds. I think its coincidence that all 3 of us (Gromit, yourself and me) are using Royds with our NVA kit, and from what you guys say about biamping I think its definately the way forward for me too.

Only slight issue with my Royd Abbots is that when I listen at high volume the sound does harden up a touch. I wonder whether adding more power (biamping) may help keep them under control.

Anything other than high levels though, and its the best sound i've had by a long way.

Once i've tried it i'll report back.

 

That seems to be a Royd 'thing', ultimate volume doesn't really seem to have been one of Joe Ackroyds ultimate goals. I think they did actually market a few models specifically on their ability to go louder than the rest of their range, though whether their sonic abilities were compromised in any way I do not know; I would have thought all the models would have had more 'loudness' capability if it could be easily incorporated without compromise.

I have found mine to go satisfyingly loud - they certainly fill the room, even at relatively low volumes. They can in fact go much louder than I am comfortable with - I found out how loud once, and had to pay for a new old stock driver... (Bi-amping with monos and twin volume controls meant the damage was limited to just the one driver fortunately. A small mercy!) Their abilities are in 'believability' (new word) and accuracy. The Bi-amping gives more of the same, you may well find the hardness creeps in a little later. Even if that is not the case, the volume range that they are already comfortable with is what will improve - of that (if little else) I am sure.

 

I don't currently bi-amp but my ambition is to one day build a system around an active digital crossover (like from DEQX) and bi-amp from there. This allows for room compensation, phase alignment and can keep the analogue circuit nice and simple. And since each amp has just one driver to control, I always thought you could get away with less expensive amps albeit x2 or x4

But of course this is active rather than passive biamping.