Bi-Amping

Cam -- Thu, 03/24/2011 - 16:09

Hi Folks,

I've got a couple of questions pertaining to bi-amping on which I'd love your opinion.

1) Wondering if anyone can help me understand the theory and benefits of bi-amping in general?

2) From what I understand, there are 2 potential bi-amping approaches. Is my understanding of the methods below correct? What are the pros/cons of each approach?
a) Use two identical monoblock amps, with each one driving one speaker. I guess you could also bi-wire with this approach.
b) Use one stereo amp to drive the low frequencies of each speaker and a second stereo amp to drive the mid/high frequencies of each speaker.

Thanks!

Cam

Robert Harley -- Thu, 03/24/2011 - 20:45

In addition to the division you name, there's another way to think about bi-amping: active and passive. In passive bi-amping, one amplifier channel drives the loudspeaker's woofer and another amplifier channel drives the midrange and tweeter, all through the loudspeaker's crossover. The speaker must have bi-wired inputs for this method. Passive bi-amping allows you to optimize the choice of amplifier for the frequency range it will be reproducing, such as a big solid-state amplifier on the woofer and a lower-powered sweet-sounding tubed amp driving the midrange and treble.
A better approach is active bi-amping in which a line-level crossover splits up the frequency spectrum before the power amplifiers. Active bi-amping removes all the crossover components between the amplifier and loudspeaker drivers, which confers huge advantages. Getting those big inductors and capacitors out of the signal path between the amplifier and drive units results in much better sound. The trick, however, is to design the active crossover so that its characteristics are compatible with the properties of the drivers. If you go with active bi-amping, it's best to use a line-level crossover designed by the loudspeaker designer.
Rockport Technologies recently converted its top-of-the-line Arrakis loudspeaker to active bi-amping. The technique requires an outboard crossover and four amplifier channels, but it is worth it.

Cam -- Sun, 03/27/2011 - 15:24

Hi Robert,

I'm currently using a Simaudio Moon Evolution i-7 integrated to drive my Revel Ultima Studio 2s, using Cardas Golden Reference bi-wire. Which of the following upgrades do you think would give me the biggest sonic improvement:

1) purchase a Simaudio Moon Evolution W-7 dual mono power amp, hook it up to the i-7's variable RCA line level outputs, and bi-amp the Ultima 2s (I assume this would mean the W-7 would power bass on both speakers and the i-7 would power mid-highs). Sim says the i-7 is basically a P-7 pre-amp and a W-7 power amp in one box, so the amplification in the i-7 integrated is the same as a W-7 (150 wpc @ 8 ohms, 300 wpc @ 4 ohms) with a slightly smaller power supply.

2) purchase a Simaudio Moon Evolution W-8 dual mono power amp (250 wpc @ 8 ohms, 500 wpc @ 4 ohms) and continue just to bi-wire.

3) purchase a pair of Moon 400M monoblocks (Moon line only, not Evolution; 400 watts @ 8 ohms, 650 watts @ 4 ohms) and drive them with the pre-amp in the i-7 via the RCA line outs, bypassing the i-7's amplification section.

What do you think? Option 1 would cost about $9k + new speaker wire, Option 2 would cost about $15k and Option 3 would cost about $7k. Of course, staying with what I have now would cost $0.00!

Thanks!

Cam

Robert Harley -- Mon, 03/28/2011 - 21:38

HI Cam,

I would try option #3 by borrowing a pair of 400Ms from your dealer and listening to the system. The Revels really come alive with plenty of power behind them; I found that a 250Wpc Mark Levinson amplifier was not quite enough power to hear the Revel's full potential.

Robert

Cam -- Fri, 03/25/2011 - 05:20

Interesting! Thanks Robert!

staxguy -- Sun, 03/27/2011 - 16:07

Hi, Cam,
A friend of mine has two Parasound HCA-2200II amplifers in his system, driving a pair of Monitor Audio 1800R/Gold's, I believe - D'Apolito like configuration. After not having room for one of those two Parasound amps in my hi-fi rack, I passed it his way, and he experimented with it in his system, using Nordst mid-level cabling, throughout, I believe.
The best result he obtained, giving a level of bass response that he appreciated with techno-type music or else decent classical / orchestral details (his two real audio preferences, with classic JMJ in the middle of his range, perhaps...) was with each amplifier driving each speaker - there was no comparison in channel seperation et al using one for the bass drivers, and another for the tweeters.

Some people - and some active speakers - will choose various topology or power-rating or class etc. amplifiers for various ranges, or some over the top assaults will use multiple mono-block amplifiers per speaker (4 say with the B&W Nautilus or even more with cusom horn designs), but the easiest and friendliest results seems to be with two idential amplifiers stereo or monoblock, each driving a different speaker, either bridged to the cross-over, or else bi-wired there instead from stereo channels.

In my ideal world, I'd love to see integrated amplifiers provide an always powered pre-amp out to match the output level of the amplifier portion of the amp, to allow for less-ideal bi-amping, and as a way for manufacturers to drive sales from our existing investments and choices in gear, but for some reason (cost can not be a real factor), I have yet to see such friendly entry-level products.

That's my Canadian quarter, to your question! :)

Staxguy, Vancouver

Cam -- Sun, 03/27/2011 - 16:53

Thanks Staxguy, from another fellow Canuck!

Simaudio says that I can use the variable line level outputs to drive a separate W-7 dual mono power amp, so I'd have the outboard W-7 and the amp in my i-7 integrated (which is basically another W-7 dual mono amp) to bi-amp my speakers. Problem is, the i-7 manual says that I can use the variable line level outputs if I want to use my i-7 integrated as a pre-amp ONLY. Although my Simaudio dealer thinks it's possible to us the i-7 integrated with the W-7 power amp in a bi-amp solution, I think I'll need to confirm with Simaudio that this is possble.

Cheers,

Cam

staxguy -- Sun, 03/27/2011 - 17:31

Let us know: it might require some cable or internal modification, but look into it. :) Most integrated amps I know have a little metal jumper between two sets of RCA's for normal use, or else taking out that jumper allows for connection to an outboard amplifier, and of course removal of the internal amplifier section from the chain. A "Y" RCA cable would allow likely connection to both, but I would go ahead and see what Simaudio may advise. I had the same issue with a YBA Integre, which would of really benefited with an accompanying higher-power and less finesse-orientated amp for the bass frequencies, but still giving that "YBA house sound" in the mid-and-trebble dept, but it would have been a hardware modification in the YBA's case, and that would of entailed some other sacrifices, feature wise, to simply use it as a pre.

I wish you the best of luck!

Being a smaller company, I hope Simaudio can accomodate your desire, which is much less uncommon, that you might imagine. :)

Let us know.

Cheers, Staxguy

Cam -- Sun, 03/27/2011 - 18:20

Thanks Staxguy,

I'll post what I find out from Simaudio. The i-7 integrated doesn't have a set of pre-out/main-in jacks with jumpers that would allow for the insertion of something between the pre-amp output and power amp inputs (the NAD M3 integrated I had before it did have this feature, as well as other helpful features like the ability to bridge it's amps and turn it into a monoblock amp). The i-7 only has RCA tape loop inputs/output RCA jacks (no jumpers - not sure what these would be for?) and variable line level output RCA jacks from the pre-amp.

Cam -- Wed, 03/30/2011 - 14:20

Just to follow up - Simaudio confirmed that the variable line out RCA jacks on the i-7 integrated amp can be used to drive an outboard amp concurrently with the i-7's own internal amplifiers.

I don't think I'll go this way, though. After some research, the whole idea of "horizontal" bi-amping seems a little hit and miss. I like the the idea of either leveraging mono-blocks for each speaker or just getting a more powerful 2 channel amp better.

Cheers and thanks for your input!

Cam

Robert Harley -- Thu, 03/31/2011 - 20:43

Let us know what you decide and how it works out for you. I'm interested to learn from your experience.

Cam -- Tue, 04/19/2011 - 10:52

I borrowed a Simaudio W-8 amplifier along with a P-7 preamplifier to try out on my system at home. I've not gotten around to listening to the P-7 yet but it's been an interesting experience leveraging the i-7 integrated amp and the W-8 amp to bi-amp my Revel Ultima Studio 2s.

I first hooked up the W-8 to the i-7's pre-amp via the line out RCA jacks on the back of the i-7 (using Cardas Golden Reference interconnects). I ran my Cardas Golden Reference bi-wire speaker cables from the i-7 to the mid/high frequency binding posts on the Studio 2s (since the Cardas bi-wire configuration has separate "low" and "high" frequency speaker connections, I only used the higher guage "low" frequency connectors, the "high" frequency connectors were not connected to anything). I then ran XLO Unlimited speaker cables from the W-8 to the low frequency binding posts on the Studio 2s.

The i-7/W-8 bi-amp configuration produced a noticably better sound than the i-7 alone. The soundstage grew in every direction but the biggest difference was depth. I could now hear much deeper into the recording venue. Imaging was also much improved, with instruments becoming easier to locate in three dimensional space. Related to this, there appeared to be more detail and clarity in recordings. This was a great effect on some recordings, however on other lower quality recordings their was a little of that "ruthlessly revealing" quality that reviewers talk about. Going back to the i-7 alone from the i-7/W-8 bi-amp configuration, however, it was like the music got slightly compressed. I missed the space and three dimensionality.

As expected, with the W-8 dedicated to the lower frequencies, there was a noticeable improvement in bass detail. Someone once wrote about a pleasant "rocky hardness" to the bass of Simaudio equipment and what I heard was more of that - extremely tight, detailed, extended bass. On the right recording, you could really feel the tight, sharp "punch" of the kick drum. Ironically, it was a little less warm and had a little less mid/upper bass bloom than the i-7 alone, so it didn't feel that I got more bass from the bi-amp configuration. I did get better bass, though (more defined and a bit deeper).

Overall, the i-7/W-8 bi-amp configuration is a significant improvement over the i-7 alone (but it should be at the price of the W-8!!). I suspect that the W-8 is overkill in this set-up, though, and I wonder if a W-7 would be more than adequate in its place?

Next to evaluate the i-7 vs. a P-7/W8 combination. I'll write about that soon.

Cam -- Sun, 04/24/2011 - 17:12

A further update...

Upon more listening I believe the "revealing" nature of the i-7/W-8 bi-amp configuration was more than just added clarity. I tried the same bi-amping experiment at my Revel dealer's place with a few different amps and my i-7 integrated (continuing to use the Revel Studio 2s as speakers). Long story short, the output level on the i-7 is higher than any of the amps I paired it with in a bi-amp configuration. Regardless of which amp I paired it with, if the i-7 was driving the mid-high frequencies those frequencies were always lounder. The opposite was true if the i-7 was driving the low frequencies, in this case the bass was always emphasized.

Of all the amps I tried (McIntosh, Mark Levinson, Simaudio W-8 and some tube monoblocks, the manufacturer of which I can't recall), the closest output level match to the i-7 integrated was the Simaudio W-8. Still, although initially appealing, over time I begain to notice the i-7/W8 bi-amp configuration (i-7 driving mids/highs; W-8 driving lows) was not quite flat in frequency response. This became apparent when I switched from the i-7/W-8 bi-amp configuration to a traditional Simaudio P-8 pre-amplifier/W-8 power amp configuration. The sound was richer, more solid and more natural sounding with the P-7/W-8 combination (although much of the soundstage depth gained in the bi-amp configuration went away). In fact, the P-7/W-8 combination sounded much more like the i-7 integrated alone than the bi-amp configuration.

Next experiment was to examine the differences between the pre-amp in the Moon Evolution i-7 integrated vs. the dedicated Moon Evolution P-7 pre-amp. Simaudio claims there is a significant improvement in performance in moving from the i-7 pre-amp to the P-7 pre-amp/P-7 power amp, and that much of this improvement is due to the P-7 pre-amp being superior than the i-7's pre-amp section. To be honest, I didn't listen to more than a couple tracks but it was clear that there is a significant difference between the sound I heard using the i-7 as a dedicated pre-amp with the W-8 amp vs. the dedicated P-7 pre-amp driving the W-8. In a nutshell, what I heard was that the P-7 pre-amp presents more detail and clarity, particularly in the upper frequencies, whereas the i-7's pre-amp is "smoother" (less detailed?) with perhaps a little more mid-bass bloom. I think Simaudio would argue that what I heard in the P-7 was greater accuracy in terms of dynamics, pin-point precision and clarity. Did I like it better? Tough question - I guess it depends on the recording, and there's the rub with high fidelity! It makes great recordings sound better and poor recordings...well, you know for sure how bad they are!

So, what were my key take-aways from this cool experiment?

There is something to this horizontal passive bi-amping thing, particularly in terms of expansion of soundstage and dynamic headroom. However, it's trial and error so no decisions should be made without a trial in your system. Clearly there's a lot of variables beyond what you can read in equipment specs that play into this so I think the results will be difficult to predict without some good solid listening time. However, if you have a good integrated with pre-outs or line level outs, and you have the patience to try a bunch of options, I'm sure you could get some great improvement in sound without spending a lot of cash on a new system with separates!
The Simaudio i-7 is a fantastic value within the Simaudio line-up (as I'm sure is the new 600i integrated). Comparing the performance of the i-7 to the P-7/W-8 separates, I'd say that you can get over 90% of the performance of the P-7/W-8 combo (or even a P-7/W7 combo) at less than half the price with the i-7. The sound between the i-7 and P-7/W-8 combination is VERY similar overall, with the key differences being more detail (which you may or may not like), slightly better dynamics and tighter/deeper bass with the P-7/W-8 combination.
The W-8 is a very solid amplifier that took complete control over my somewhat difficult to drive Revel Ultima Studio 2 speakers, from rock solid deep bass to clear, grain free mid-range and treble. It sounded very neutral, and was more than capable of resolving differences between the subtle differences among the pre-amps I tried.
The presumption that you will get more clarity, resolution and dynamics as you get into the Moon Evolution separate pre-amps seems to be true. Will you like it better? That's up to you and your tastes!