[shokunin]

I've been passively bi-amping my RM/x with a SET amp on the Neo Panels + FST Tweeter and Ampzilla monoblocks on the bass.  Honestly on the Price/performance ratio, the improvement is hardly worth the $$$$ in the additional amps, interconnects, power and speaker cables.   In fact, without a lot of tweaking, there's almost a NEGATIVE ROI on the bi-amping using two different amps.

Before I throw in the towel on the passive bi-amp route, I figured I should probably give it one last shot and try an Active bi-amp.  TacT guys have all the flexibility in the world to change things on the fly, but I'm mainly analog so I'll be looking for an analog x-over (Marchand? Bryston?).   Does anybody have any recommendations on a good analog crossover and what x-over frequency between the bass and neo panels would you recommend?

Thanks...
Glenn

[Marbles]

Give John Casler a call...the NHT X2 is a pretty good active XO with just a hint of edge on the highs.  Great price, very flexible.

[zybar]

I've been passively bi-amping my RM/x with a SET amp on the Neo Panels + FST Tweeter and Ampzilla monoblocks on the bass.  Honestly on the Price/performance ratio, the improvement is hardly worth the $$$$ in the additional amps, interconnects, power and speaker cables.   In fact, without a lot of tweaking, there's almost a NEGATIVE ROI on the bi-amping using two different amps.

Before I throw in the towel on the passive bi-amp route, I figured I should probably give it one last shot and try an Active bi- ...

Glenn,

To really gain the benefits of active bi-amping, you really need to bypass the VMPS crossovers.  I suggest you contact Eric K. and he can give you the details on the improvements he has been able to gain by going in that direction.

George

[shokunin]

Marbles,

Does the NHT go up to 200 or higher? Just curious as I thought it was mainly a "sub" x-over.?  

George,

Thanks, I forgot that Eric dove in and shorted / bypassed his x-over.  Did you ever actively bi-amp with your Tact and the RM40's when you had them?

Glenn

[Marbles]

Marbles,

Does the NHT go up to 200 or higher? Just curious as I thought it was mainly a "sub" x-over.?  

George,

Thanks, I forgot that Eric dove in and shorted / bypassed his x-over.  Did you ever actively bi-amp with your Tact and the RM40's when you had them?

Glenn

It only goes up to 220 HZ

I'm pretty sure that Eric posted what he did and how he did it, if you want to search the VMPS forum.  Good call George.

[zybar]

Marbles,

Does the NHT go up to 200 or higher? Just curious as I thought it was mainly a "sub" x-over.?  

George,

Thanks, I forgot that Eric dove in and shorted / bypassed his x-over.  Did you ever actively bi-amp with your Tact and the RM40's when you had them?

Glenn

I haven't sold my 40's yet.  

I didn't bi-amp the 40's with the Tact.  Instead I used the Tact to integrate the two Larger subs.

George

[woodsyi]

Glenn,

I use a Marchand 3-way xm44 active crossover with my RM40s and a Larger sub.  I only disabled the lowpass on the woofers and left the TRT passive network on the ribbons intact.  I feel that low draw on the ribbons don't require separate amps for the FST and the NEOs.  I also think the heavy transient draws on the woofers are what really affect any amp performance on the ribbons.  I really like the sound I get with the ribbons driven by Bill Baker modded Extreme Hurricanes.  The RM40 woofers driven by Innersound ESL amp and the sub driven by Crown K2 really perform well on the bass.  I lowpass the RM40 woofers at 300 Hz and highpass the ribbons at 200 Hz using 24 dB slope.  I also lowpass the sub and high pass the RM 40 woofers at 50 Hz.  I tried lowpassing the sub at 80 Hz, but bass seemed bloated.  Even though RM 40 is perfectly capable of going down to 20 Hz, I feel the midbass is faster and punchier when only asked to handle down to 50 Hz.  The sub really blends well and kicks ass down there below 50 Hz.  When the midbass upgrade kit arrives, I am going to try using the passive TRT high pass of the ribbons at 270 Hz and see if it will blend in phase with my 4th order lowpass on the woofers at 300.  If not, I will have to kick up the highpass on the ribbons using 24db slope.  I am exited by the midbass upgrade.  If it works out, I think it will address the only weakness RM40s really ever had -- the midbass punchiness that is so important in coloration of human voices.  If I only listened to digital source, I think I would go with TACT or DEQX but I like my anolog source and tube amp on top..  I think it has to do with my preference for harmonic tonality in music over details and sound stage aspects.  The finer nuances in human voices, to me, is better captured with tubes.

[John Casler]

I've been passively bi-amping my RM/x with a SET amp on the Neo Panels + FST Tweeter and Ampzilla monoblocks on the bass.  Honestly on the Price/performance ratio, the improvement is hardly worth the $$$$ in the additional amps, interconnects, power and speaker cables.   In fact, without a lot of tweaking, there's almost a NEGATIVE ROI on the bi-amping using two different amps.

Before I throw in the towel on the passive bi-amp route, I figured I should probably give it one last shot and try an Active bi- ...

Hey Glenn,

Yep, NHT X-2, Bryston, and Marchand, I have them all.

Was the problem that you couldn't get the levels matched? Blending/Integration?

Did you try using any "passive attenuators" on the AMPzilla side?

It would seem that what is needed is actually a "level match" control since the woofs already have the filter needed, you need the X-over to be set "above" that.  The NHT does run up to 220Hz. Your passive filter is probably just under that (we'd have to check with B)

If you were thinking of actually "bypassing the filter" to a higher Low Pass point, then the Phil will build to suit.

Marchand can be ordered to most any Low Pass Filter spec, and the Bryston has a rather good selection of Low Pass hinges too.

Or we could sell the 845's and get you a DEQX and a pair of Son's

[shokunin]

Woodsyi, Is the Marchand pretty transparent?  Are you using both a high pass x-over from the marchand and the internal passive crossover?  I like the fact that Marchand has "oem" modules that I could place a x-over by my monoblocks (which are 2' away from the RM/x's) instead of a single "component".

If I didn't have my analog setup I would try a Deqx or TacT.  I'm probably making a big deal over the extra a/d and d/a conversion but I'd rather try an analog bi-amp first to see if it's even worth it.

[Jon L]

Glenn, I feel your pain.  Finding an active analogue crossover that is very transparent is extremely difficult.  I've played with units from Krell, Purist Audio, KMF Audio, Bryston, and couple others, and none of them were transparent per se.  Even tried using a cap for top amp and active for bass only.  No good.  

I've bought and sold Bryston a few times and still am using one.  It does some things better than even Krell, namely bass and dynamics, but it's transparent enough ONLY if none of its volume/gain knobs are used.  This means you need something like EVS Ultimate attentuators or Endler's attentuators on one of the amps to match levels, which works out great actually.  

I've yet to try a Marchand unit, but I wouldn't buy one UNTIL you figure out exactly what crossover point/slopes you need.  You can then order the Marchand with the exact right x-over modules.  This is why Bryston is so flexible, as it has tons of x-over points and slopes already built-in.  You do need to decide between 10B "standard" and 10B "Sub."  Usually 10B "sub" has much finer low frequency points, but FYI it has one huge problem (for my setup anyway), which is that it lacks any crossover point between 100 and 200 Hz!  10B "standard" actually has a 140Hz point, which is what I need.  It also has a lot more points up higher in frequency.

[woodsyi]

Glen,

When I went from passive biamping to active, the first thing I notice was that mids and highs were "clearer."  It's not transparent; it is transparenter.   If there is any loss from additional IC's and circuitry, it is more than compensated by the enhanced performance of dedicated amp per driver.  

You do have to play around with frequency modules (ordered separately), L-pads and putty to get the best integration.  I know I won't go back to single amping multi drivers.

[shokunin]

Hey John,

I was actually able to match levels using the L-pads as the Ampzillas are more powerful than the deHavillands.  The L-pads at around 3:00 in order to compensate for the levels.  THe sound isn't quite as coherent as I would like, but when tweaked it did sound very good, just wasn't as great of an imporvement as using just one set of monoblocks either the deHavillands or the Ampzillas.  Obviously the deHavillands cannot produce the full impact and low bass that the ampzillas can.  Tonally the deHavillands and the Ampzillas are great match as they are very similar at the crossover point around 200hz.  Since I don't listen at insane volumes I don't think I've ever stressed the Ampzillas to clipping.

I was thinking of bypassing the the low-pass coil and using an active x-over on the bass and sending only the high-pass signal to the deHavillands.

Glenn

[Jon L]

I hate to tell you this, Glenn, but no matter what you do, passive or active, you'll likely always hear a little coherency problem as long as you use 2 different amps.  ~200Hz is pretty low (good) for using 2 different amps, but not low enough.  In my setup using 2 different amps, there is a significant difference in coherence even going from 200 to 140Hz.  I want to use even lower point, say 70-80Hz, but my midrange driver will blow up.

We're not talking about anything obvious, but I'm sure you can hear it.  Successful active biamping is not something you can achieve quickly.  It will take a lot of sweat and $$.  To do it really right with analogue active x-over, you would have to bypass all the passive x-overs, get 6 channels of amplification, figure out exactly what x-over points/slopes you need, and order a great active x-over with 6 channels.  Even then, I highly recommend using the same amp for all channels.  

If you want to keep the passive x-over between tweeter/midrange, I think you should still keep amps same.  I think you will get great results, which should be much better than now, if you are able to at least bypass the passive x-over between midrange and bass, and use a good active to use 4 channels of same amplification.  This may be all you need for all practical purposes.  I can bring over my Bryston 10B "standard" when you are ready to try something like that

[shokunin]

Hey Jon,

I was worried about that, as the x-over seems to be rising from 166hz up to 200hz and possibly higher, it's creeping into the lower midrange, where problems can be heard on male vocals and cellos using 2 different amps.  

I can definitely see how powerful a TacT of Deqx could be to try and create a 3-way crossover using an Ampzilla on the Bass and a pair of Son of Ampzillas to power the mid panels and tweeter separately.  However, that seems like a whole lot of $$$

[John Casler]

Hey Jon,

I was worried about that, as the x-over seems to be rising from 166hz up to 200hz and possibly higher, it's creeping into the lower midrange, where problems can be heard on male vocals and cellos using 2 different amps.  

I can definitely see how powerful a TacT of Deqx could be to try and create a 3-way crossover using an Ampzilla on the Bass and a pair of Son of Ampzillas to power the mid panels and tweeter separately.  However, that seems like a whole lot of $$$

I think you might find that (even though I suggested two Son's) a single son would handle the FST and the NeoPanels pretty well.

At CES we had a "single 100w channel" of three Son's driving 3 RM40s "full range", (woofers too) and it didn't break a sweat.

.

[woodsyi]

Glenn and John,

I don't agree that amps have to be the same.  You have cones and planars which are blending around 200 Hz.  Even if you use identical amps, the drivers exhibit different characteristics.  In the past, I think too much of mid bass was asked out of the Neos, which resulted midbass wimpiness.  With the faster midwoofer taking over up to 270HZ, midbass should exhibit more impact and mids and highs,  clearer above 270 Hz.  With more prominent role asigned to the midwoofer, it becomes even more important to get a fast and powerfull amp.  I don't think too many tubes can do that.   But I won't give up my tubes on top.  I am convinced that a slope and value can be found for the filter poles to make biamping with tube on top and ss on the bottom can be done.  This is where I do miss the oppotunity to play with digital x-overs with phase correction and instant changes.....  Whatever the case may be, bi or tri amping actively in any permutation has the potential to take these speakers to another level.  With your gears already, I would disable that coil and plunge into active biamping to find out what it's like.  You can always resolder it and go back.  But I don't think you would go back.........