Passive bi-amping with a mix of amps ?

What is passive bi-amping? It sounds like splitting the signal output of preamp with no frequency dividing circuitry, to each power amp, one driving bass and the other treble with partial crossover circuitry on each at speaker end, to feed correct signal to drivers, effectively like standard biamping with the filters movers after rather than before the power amps.

If so, seems unlikely to be anything like as good as active biamping, which has the benefit of the filters operating at low power levels. Unless your preamp has two independent outputs running simultaneously you'd need to split the signal, and a simple 'y' cable connector could be detrimental. And if the power amps have different gains you'd need a means of adjusting the level of one channel relative to the other.

Passive Bi amping is when a single amp can be used to controll an select group of drivers. Example, I have a pair of 3 way speakers. I use a 250.2 to Drive the Woofers, a 200 to Drive the Midrange, and another 250.2 to Drive the Tweeters.

Naim does not Advocate Bi wiring, but they do recommend Bi amping. In fact, this is an upgrade path towards an Active System.  All three of my amps are connected to my Hi Cap DR, which is connected to my 282.

Next Question, what is an Active System? This is when the crossover located within the Speaker is rendered useless, and taken out of the equation. Hence, an external crossover is needed, and then we have an Active System. A couple of heavy weights are running Naim Active Systems with an S1 Pre, I hear its the holy Grail!

Before Bi Amping my Briks, I wrote Naim, and they replied its fine, because Naim amps have the same gain.

When I posted this information on the Forum, one of the heavy weights pointed out this wasnt 100% true. There is a slight differece in gain between the 500, and the rest of the gang.  And of couse, there is a difference between the Statement amps.

Now when one mixes amps they reference to this as an Wonky system.

Idealy one would use two 500's, or 3 300's or 3 250's.

Mind you, none of this is possible, unless the Speaker of choice allows this.

My next Upgrade, Snaxo 362/SC2, then I'm Active

Hope that was helpful!!!!!!

Sorry bystander, Didnt finish reading your reply!

Innocent, your surmise is basically spot on.  Although a good quality Y-split cable needn't be detrimental, as far as I'm aware.  The main benefit is simply to drive the speaker with more power.

RJS, the gain difference may be a problem, although I don't know whether +1 counts as material or not.  You'd need to test it to be sure.  In experimenting, I ran into that issue before but the gain difference was almost certainly greater, and therefore more noticeable in its effect on the tonal balance.

However, not being familiar with 802's, I wasn't clear why an active solution isn't viable ?

The concept of  biamping I am familiar with - in fact I'm playing with active triamping of a DIY speaker because it is far easier to tweak the crossover that way - it is very clearly advantageous because it shifts the filter circuitry to the low power side, and simultaneously gives the power amps full 'control' of the speaker drivers they are directly connected to (but any fault can easily blow tweeters as there's nothing to stop bass getting through, eg unplugging input while turned on).

But I struggle to grasp the benefit of passive...  It's still putting the full frequency range through the amps, which in the case of the treble amp it outputting the bass  into the high impedance of the crossover circuitry, while the treble goes through as normal, and the bass amp is similarly outputting the treble into the high impedance of the XO with the bass going through as normal. I think that means intermodulation distortions in the amp would be unaffected, while any power handling limitations or effects from the XO would still be there. Am I missing something?

incidentally, 1dB difference in gain is likely to be audible - notionally about the smallest step in volume difference you hear. Whether objectionable is another matter - as it is the 500 that is the higher gain, and you'd presumably want the higher power capability on the bass end wher the energy is highest, it would give a marginal boost in level below the crossover frequency.

I think RJ is running SL Speaker Cable, and in a previous post was seeking information which wire links work well with SL Speaker Cable, since there arent SL jumpers/Link wires. 

I was teasing him And suggested, Bi amping. B & W advocates Bi wiring, but also states that Bi amping is an improvement over Bi wiring.

 So my thinking forget about the mis match jumpers and plugin SL Speaker Cable directly into  Speaker post.

Might want to check with Forum member or Naim to see if that difference in gain would be measurable.

Naim also pointed out in there reply, that the mistake most make, assuming that the better amp Goes on the lower frequencies, when it should go on the faster tweeters.

I think Naim strong suit, it swings like no other amps. However, Naim's Achilles heel, lack of power.

Hence, Naims cater, Bi/Tri amping, and going Active!!!!!

JMHO

Bystander, I think you point on!

Hence, a path towards an Active System.

Mind you I was Active with full blown Linn Aktiv System, Once you go Active, you can't go back!!!!!

I'm not suggesting that +1 gain is inaudible, especially for someone used to a very high resolution system.  But it may fall into the spectrum of 'preference' (if lucky) or 'indifference', as opposed to 'plain wrong'.  Only trial & test will really establish that, I think.....

Back on to the general matter of bi-amping, I suppose the other concern with using different amps is to do with any subjective timing differences they may exhibit.  If these exist, and are apparent, it could lead to a more muddled musical portrayal at odds with the 'Naim sound/prat' etc.  Again, I don't know if this would be the case, I'm just flagging it as a possibility.....

Passive bi-amping has really confused me when I think about it !   One amp doing treble and another doing bass on a split two way crossover... I would think it would be better having one amp with + treble and - bass and the other amp doing - treble and + bass.   A vertical instead of a horizontal biamp 

To Innocent and your points above, I don't believe you are missing anything.  But the issues you describe are drawbacks vs active bi-amping, rather than vs not bi-amping.

I remain unclear why active is not an option in this particular case.  Although there may be more different drivers than binding posts, for example - which would limit the benefits.

the main difference between passive (still using the speaker's crossovers) and active (no crossover at the speaker level but an active crossover device placed between the preamp and the power amplifiers) multi amping is that the exact real purpose of separating amplified frequency ranges and (most important) getting rid of filters inside the speakers, disappears...

the only benefit of multi amping in passive mode is ... sheer power!

but i strogly recommend 2 things:

1. all power amps to have equal gain (a MUST)

2. preferably - all amps be of similar quality

since we are talking Naim world, then, also based on my personal experience, instead of using 2 different level amps for passive bi-amping, better use only the better amp in single... if one has 2 amps the same, and speakers allow bi-wiring, then some gains might be observed, mainly when the speaker demands lots of control (read serious sustained current)

if similar quality amps are used, the most powerful is to be used on the lower frequency drivers, since they demand the most current.

some examples, to clarify: if i had one 250 and one 200, for example, i would use the 250, and swap the 200 for something more useful... if i had one 180 and one 200, i would put the 180 on highs, and 200 on lows.

but testing will tell the optimum result, as always!

nevertheless, difference in gain will translate into incorrect tonal balance, so you won't really hear the speaker you bought, but a "filtered" version of it, the filter applied would be at the driver you connected the lower gain amp, and the amplitude of the filter would be the difference in gain between the 2 power amps, in you case if you connect 500 (30dB gain) at lows, and 300 (29dB gain) at highs, then is like applying a 1 dB filter on highs.

karlosTT posted:

To Innocent and your points above, I don't believe you are missing anything.  But the issues you describe are drawbacks vs active bi-amping, rather than vs not bi-amping.

I remain unclear why active is not an option in this particular case.  Although there may be more different drivers than binding posts, for example - which would limit the benefits.

Spot on with the first paragraph, as to the second paragraph!

Well, let's see, assuming that the speakers can be operated in Active mode.

Cost of an second amp, then Cost of SC DR, Cost of an Burndy, then Cost of an SL IC from Snaxo to 552, and Don't forget the cost of the Snaxo.

CASH!!!!!!!

That's why less than 1% even consider the Active Route!!!

But it is Naim's Ultimate upgrade path, which addresses it's Achilles heel, lack of POWER!!!!!

The OP is just trying take Advantage of an upgrade that his speakers manufacture suggest!

I think!!!!!!!

Passive bi-amping appears to bring potential pitfalls with no obvious gain, except the suggestion that it brings more power. But I'm not convinced that is significant usable extra power, splitting the amps in that way, effectively in parallel. Paralleling across the whole spectrum would make the additional amps effectively available on any peak, but with the crossover in use, a peak at, say 100hz will only effectively use the amp filtered to bass, exactly the same as it would if that amp was connected in conventional manner. Same if a peak anywhere else in the audio spectrum. Paralelling the amps across the full spectrum might be another matter - if the electronics can stand it, and I suspect that might mean perfectly matched pairs, though I'm out of my depth here, and I'm not suggesting anyone tries without definitive advice.

Can Naim amps be bridged, to use the two channels effectively in series. Then simply using two amps as monoblocks (but they'd want to be the same)?

My thanks to all for your thoughts & experience and to Allante93 especially for planting the seed of bi-amping in my head earlier in the week!

Those wondering about active 802 Diamonds - B&W don't offer you a way inside unless you're willing to take a drill and jigsaw to the rear cabinet of a £12,500 speaker pair (and they're 12 months new!)... and that was never an option I considered. The other consideration is the availability of a matched crossover (which B&W don't do)... and the £cost thereof if they did.

So, no... it has to be passive bi-amping with 802's.

Now, for those who advocate the more powerful amp on the bass driver... no, no.. forget that !!  The place you need the added control and transient power that the 500 delivers over the 300, is right at your mid / high range drivers, so the 300 would connect to the lower pair of terminals & the 500 to the upper ones.

And to Tobyjug for his suggestion of vertical vs horizontal bi-amping (see post a few above), the thought is intriguing... but would you try it on a fairly new 500 and likewise 802's if you were a pensioner struggling to keep food on the table and heat the humble abode ?  (you'll note I have my priorities firmly placed... hifi, food, heating bills... in that order)   If you do give it a whirl and still have working amplifiers and speaker drivers afterwards, will you report back to us on how it sounds?  Thanks.

Roger  

Opinion is divided on the question of where the greater power is needed - my view is based on the fact that highest acoustic, and so electrical, energy is at the bottom end, while tweeters have much flimsier voice oils than woofers and can't take anywhere near as much power - but they don't need to. As for speed of response, that is needed in balance across the system.

Howevr if you do go for it, it is a simple matter to swap around and try both ways, bearing in mind that whichever end gets the 500 gets a 1dB boost.

My thoughts exactly on the 'swap 'em and see' proposal, Innocent 

Wasn't at home so couldn't get to information that I filed away, but here it is! 

''sales@naimaudio.com

support@naimaudio.com

Hi

All Naim amplifiers have the same gain, so it is possible to mix them but the trap is to assume the biggest amplifier should be on the bass, whereas it should be on the tweeter as this needs the best amplifier with the fastest response

Regards

Steven Hopkins ( NOV 1ST 2014 ) ""

==============================================

""All Naim Power Amplifiers do not have the same gain!

They are all 29dB - except for NAP500 and Statement, which are 30dB.

I also confirmed this published Naim specification (look it up) with the Statement designer, who told me that the 1dB difference did exist.

It may matter for those with 'Wonky Active' with mixing NAP300 and NAP500.

But the crossover allows for this gain difference to be removed and leveled - good to know it exist though, for some.

DB.

rjstaines posted:

My thoughts exactly on the 'swap 'em and see' proposal, Innocent 

Right RJ, that's exactly what I did! 

Cdx2> HI Cap DR > 282 > 200 on the tweeters and 250.2 on the Woofers & Mids

Bi Amped Briks

Not Bad, Mind you it's been nearly 3 decades since I heard my Briks Passive with one Amp! 

Naim Amps Richer & Thicker than Linn LK 280's, but when reflecting back Linn Amps did appear to be quieter!  No Hum, perhaps due to Naim's larger Transformers! 

But after an hour of so at 9 o'clock the regulated 250, was overheating and shut off on more than 1 occasion, hence back to the bank. But Before I went to the bank I switched put the 250.2 on the tweeter, and the 200 on the Woofers & the  Mids. 

Results the non regulated 200 did not over heat, it just slipped on the job!  Didn't sound that much different, but could not play as loud. With the 250.2 driving the Woofers and Mids, I could push it up to 10.5, but with the 200 9.5 was the max.  

So After a trip to the Bank! 

Tri Amped Briks

Cdx2> HI Cap DR > 282 > 250.2 on the tweeters, 200 on the Mids, and 250.2 on the Woofers! 

Now I can push to 11 o'clock without any breakup or distortion to my ears! 

But you know what the 250.2 on the tweeter cool as a cucumber, the 200 on the Mids, just as Cool, But the 2015 250.2 on the Woofer still heats up, but have never cut off, I even put some fans on her when showing off, that's pushing it at 11 o'clock for 15 minutes or more. 

But 8 o'clock more than enough, and can play for hours without heating up! 

Next stop Active Snaxo 362/ SC DR / Burndy! 

Passive bi/tri-amping can also be economical.

If you want to drive a difficult load and a 250 isn't up to it, sure a single 500 will sound best and get the job done but it may be out of range cost-wise and a second 250 will get you over the hump for a fraction of the cost. Let me be clear, the single 500 would still be a better option IMO, but we have to be realistic. And there are loads out there that even a single 500 struggles with.

That description regarding heating up of the amps is simply because there is so much more energy at the bass end in normal music, so the bass amp is having to produce the highest power, and mid/treble merely ticking over, which is where the advice to put highest power reserve on bass comes from. I'm intrigued as to Naim's advice, but then perhaps not as the impression I have is that their emphasis is on getting the midrange as near perfect as possible, and the bass end isn't really important provided there's a bit there. To my mind you need both, and if there's a compromise to be had (and of course there always is), balance makes for greatest realism, and it can take more effort to get the bass right simply because of the physics involved.

I never had heating problems with my full Blown Active System!!!!!!!

""In the old days with the original NAP250 driving tricky loads like Isobariks at high levels, some owners directed fans at the amps during the summer to keep them cool.  The NAP135 brought its own fan cooling, which is also found in the current NAP300. 

Richard Dane

Administrator

June 22, 2015 8:48 AM

Yup, it's well worth doing as little as possible to upset the NAP250 re. cabling. Trying 5m per side of NACA5 is a sound plan. The NAP250 was considered the minimum recommendation for passive Isobariks and hard driving at higher levels could every now and then trip the thermal cut-out.  Some resorted to running with the NAP250 tipped up on it's edge for better thermal cooling and even using a desk fan to blow on the casework. Others just traded up to NAP135s (with their own internal fans) when they came along or went active, thus bypassing the passive crossover.""

Love the classic setup Allante93. I even used to have the same black Target tripod racks though back then my system was a much more modest Mimik II, Majik, Keilidhs.

Just sold them last month, Fraimlite, Black on Black, Can always upgrade to Fraim, Interchangeable!!!

I've just read an Article on the 250DR, I didn't know it was a slight increase in Power, I think  its getting 93 and 160 now, and suppose to be 30 times quieter, if I hit the lotto, that just might work!!!!

My 250.2 going in for DR mod this month hopefully. It's a pretty cheap upgrade considering. Bit worried about the amount of time I will be sans power amp though.