Live music, Tone and Presence: What most systems get wrong

[bonzo75]

I can tell you that I have not heard an Apogee yet that has better bass; not deeper, tighter or with more slam than the 4400s. I have heard two different full ranges, a couple Divas and a Grand without subs. None are better.

That said, in a small room a Duetta Signature will have a powerful sound. Calipers are limited but in a smallish room they were pretty good.

The Grands you heard in a small room were not doing the bass. Also he has a bass null running through the center of his room where the sitting position is. In fact, after listening to that set up, I was not willing to take a call on whether SETs can drive Apogees, because the room there was hiding so many things. It is only after listening to FRs on NATs in a different room I realized the commonalities.

The FRs Reudiger has produce the bess bass in some aspects. His 14m*4m room make some frequencies sound a bit too much low down, but he certainly had the best Mahler 2 I have heard by far, due to the slams in the midbass and the way the softer passages were reproduced.

To beat the bass that Justin and Lissnr have, and the coherency in the bass that the apogee duetta sig produces with the mids, you have to jump mega times over to something like the Evo Acoustics MM7.

Stats are more coherent in the mids. Their bass and mids are usually not coherent. Maybe Spectras is an exception, haven't heard the bigger ones in a bigger room.

 

[morricab]

The Grands you heard in a small room were not doing the bass. Also he has a bass null running through the center of his room where the sitting position is. In fact, after listening to that set up, I was not willing to take a call on whether SETs can drive Apogees, because the room there was hiding so many things. It is only after listening to FRs on NATs in a different room I realized the commonalities.

The FRs Reudiger has produce the bess bass in some aspects. His 14m*4m room make some frequencies sound a bit too much low down, but he certainly had the best Mahler 2 I have heard by far, due to the slams in the midbass and the way the softer passages were reproduced.

To beat the bass that Justin and Lissnr have, and the coherency in the bass that the apogee duetta sig produces with the mids, you have to jump mega times over to something like the Evo Acoustics MM7.

Stats are more coherent in the mids. Their bass and mids are usually not coherent. Maybe Spectras is an exception, haven't heard the bigger ones in a bigger room.

I have heard Grands both with the subs doing bass and with the panels running full range (the panels are quite capable). I have heard this in a "small" room and a big one too.

Rooms and bass are always tricky. I used to tame a 63hz mode in my room with digital EQ. About a 8 db cut with a narrow band parametric did the job... for digital, for analog I had to suffer. It is also tricky for live bass instruments in a room.

 

[morricab]

The coherence of big electrostatics is hard to beat. Curiously of the mini monitors shown in post #272 the more coherent (or less incoherent) uses a metal tweeter and a kevlar medium woofer - I am referring to the B&W SS25.

Coherence of a speaker needs a "coherent amplifier" - but it is a matching property. Some amplifiers seem to enhance the coherency of a speaker.

One modern multi unit dynamic speaker seemed to me more than once to have an excellent coherency when properly set - the Wilson XLF. We usually ask for a seamless transition between units, but like in a full range electrostatic, in the XLF it seems that all spectra has the same characteristic. Unfortunately no other Wislon is was as good as the XLF in this aspect .I must say that I have not listened to competing speakers such as the top Rockport.

The human voice is particularly sensitive of speaker coherency - and here I must refer to the ESL63 that IMHO is more coherent to voices than the ESL57.

Yes, the SS25 is the only B&W that i have heard that I would call coherent. Their Nautilus series speakers do not qualify on this account, IMO.

The original X1 is also quite coherent for a multi-driver system but it is still not an AudioStatic, Acoustat or Soundlab in that regard.

 

[morricab]

I'll agree too, isn't this special?

I especially agree with the different sonic signatures from different driver types, it alone can kill coherency even if everything else is perfect. The Achilles' heel of many modern speakers (for me) is when the tweeter sounds different from the midrange, it's very common although it's gotten far better over the years. Today's Be domes are much better than previous Ti or Al but not perfect. Ribbons like Raal always seem to clash a bit with the mids. It was a problem for me to find a supertweeter that blended seamlessly with my extremely light textured paper-cone midrange for this reason. Most horn tweets or ribbons weren't good enough, too much of their own character. I ended up with a tweeter with a magnesium diaphragm and alnico motor, weighing about 11 kg each! Though, I have to say an Al diaphragm can be really convincing on cymbals, just not good on anything else. Even a supertweeter is incredibly important, it can totally change the entire character of the speaker's tone down through the midrange.

Also, having the same driver produce the lower midrange through highs in a consistent polar pattern is a huge advantage, trying to manage it with multiple drivers and crossovers can be done but is rarely done well and arguably will never be as good in some ways.

As far as panel bass, sometimes electronic music can be too much for them ime. They can't stop fast enough or with as much control, I've heard large panels bottom after a bass note stops too fast at fairly low volumes. Not a problem with most music though.

The big commonality between panel and horn is the much more optimal acoustic/mechanical impedance match between driver surface area and the air.

THe coherence issue is why I have problems with most multi-way speakers and why I have found 2-way horns that can deliver big sound. Then I don't need 2.4 meter tall speakers to get the sound i want and the coherence is nearly as good (I say nearly because any speaker with a crossover and two separate drive elements cannot be perfectly coherent).

 

[manisandher]

This is what Nelson Pass thinks:

"Given the assumption that every process that we perform on the signal will be heard, the finest amplifiers must employ those processes which are most natural.

There is one element in the chain which we cannot alter or improve upon, and that is the air. Air defines sound, and serves as a natural benchmark.

Virtually all the amplifiers on the market are based on a push-pull symmetry model. The push-pull symmetry topology has no particular basis in nature.

Is it valid to use air's characteristic as a model for designing an amplifier? If you accept that all processing leaves its signature on the music, the answer is yes.

One of the most interesting characteristics of air is its single-ended nature. Sound traveling through air is the result of the gas equation:

PV1.4 = 1.26 X 104

where P is pressure and V is volume. The small nonlinearity which is the result of air's characteristic is not generally judged to be significant at normal sound levels, and is comparable to the distortion numbers of fine amplifiers. This distortion generally only becomes a concern in the throats of horns, where the intense pressure levels are many times those at the mouth, and where the harmonic component can reach several per cent.

We can push on air and raise the pressure an arbitrary amount, but we cannot pull on it. We can only let it relax and fill a space as it will, and the pressure will never go below "0". As we push on air, the increase in pressure is greater than the corresponding decrease when we allow air to expand. This means that for a given motion of a diaphragm acting on air, the positive pressure perturbations will be slightly greater than the negative. From this we see that air is phase sensitive.

As a result of its single-ended nature, the harmonic content of air is primarily 2nd order, and most of the distortion of a single tone is second harmonic. Air's distortion characteristic is monotonic, which is to say its distortion products decrease smoothly as the acoustic level decreases. This is an important element which has often been overlooked in audio design and is reflected in the poor quality of early solid state amplifiers and D/A and A/D converters. They are not monotonic: the distortion increases as the level decreases."

Mani.

 

[bonzo75]

Wow Mani, the Anima with the with the Thoress should sound excellent. And the Decca. If I remember right you had the BD horns before?

 

[morricab]

This is what Nelson Pass thinks:

"Given the assumption that every process that we perform on the signal will be heard, the finest amplifiers must employ those processes which are most natural.

There is one element in the chain which we cannot alter or improve upon, and that is the air. Air defines sound, and serves as a natural benchmark.

Virtually all the amplifiers on the market are based on a push-pull symmetry model. The push-pull symmetry topology has no particular basis in nature.

Is it valid to use air's characteristic as a model for designing an amplifier? If you accept that all processing leaves its signature on the music, the answer is yes.

One of the most interesting characteristics of air is its single-ended nature. Sound traveling through air is the result of the gas equation:

PV1.4 = 1.26 X 104

where P is pressure and V is volume. The small nonlinearity which is the result of air's characteristic is not generally judged to be significant at normal sound levels, and is comparable to the distortion numbers of fine amplifiers. This distortion generally only becomes a concern in the throats of horns, where the intense pressure levels are many times those at the mouth, and where the harmonic component can reach several per cent.

We can push on air and raise the pressure an arbitrary amount, but we cannot pull on it. We can only let it relax and fill a space as it will, and the pressure will never go below "0". As we push on air, the increase in pressure is greater than the corresponding decrease when we allow air to expand. This means that for a given motion of a diaphragm acting on air, the positive pressure perturbations will be slightly greater than the negative. From this we see that air is phase sensitive.

As a result of its single-ended nature, the harmonic content of air is primarily 2nd order, and most of the distortion of a single tone is second harmonic. Air's distortion characteristic is monotonic, which is to say its distortion products decrease smoothly as the acoustic level decreases. This is an important element which has often been overlooked in audio design and is reflected in the poor quality of early solid state amplifiers and D/A and A/D converters. They are not monotonic: the distortion increases as the level decreases."

Mani.

This is consistent with what Cheever has to say about the ear's own self-generated harmonics. They are also monotonic and (of course) single ended in nature. He claims that an amplifier with a harmonic distortion pattern that closely matches the ear's own self-generated harmonics will for all practical purposes sound distortion free.

Most DACs will be using an opamp for an ouptut stage, which is both push/pull in nature and using a lot of negative feedback. Same for nearly all SS power amps (there are a coupled of notable exceptions).

 

[morricab]

Just think about it. If you add a complex of coils, caps and resistors to the output of an amplifier. At the very least, you will be dissipating a good bit of the energy of the amp in heat instead of electromotive force to the speaker elements. A lot of passive crossovers are also designed to equalize volume relationships between speaker elements of different efficiencies and impedances i.e. differential resistors. All of the speaker elements have to be "dumbed down" to the lowest common denominator of efficiency of the least efficient speaker element to get an appropriate volume relationship.

A specific passive crossover would have to be measured, but my hunch is 2db insertion loss would be optimistic for even a simple passive crossover.

Not necessarily. Through the passband they should not be adding much in the way of impedance and you would have only the DCR of the coil. If you have resistors in the circuit that are specifically reducing the gain of a driver by 2 or 3db then you would get the loss you are describing but this is not "insertion loss".

If we take a simple passive two-way xover with no equalization of the drivers then I would argue you will get less than 1 db loss through the passband of each leg of the crossover. The AC impedance of a cap (simple 1st order xover for a tweeter) is close to zero through the passband and the inductor (simple 1st order low pass) would be basically only the DCR of the wire itself, which if a good inductor is used whould be far less than 1 ohm.

Obviously if power resistors are added because of gain matching issues then you will have losses in X db depending on the gain attenuation but then only in that frequency range so the overall power loss might not be that great (usually it is the tweeter that needs padding down to match the other drivers so this is the least power dissipation).

So, maybe for your speakers it was 3db because of resistors padding down the signal but that is not the same thing as insertion loss, which is just the inherent loss from the properties of the elements in the crossover.

 

[KeithR]

This is consistent with what Cheever has to say about the ear's own self-generated harmonics. They are also monotonic and (of course) single ended in nature. He claims that an amplifier with a harmonic distortion pattern that closely matches the ear's own self-generated harmonics will for all practical purposes sound distortion free.

Most DACs will be using an opamp for an ouptut stage, which is both push/pull in nature and using a lot of negative feedback. Same for nearly all SS power amps (there are a coupled of notable exceptions).

but Nelson's opinion doesn't matter to you

 

[KeithR]

SS amps with little or no negative feedback these days include:

D'agostino
Gryphon
DarTZeel
Pass/FirstWatt
Ayre
BAT
Lamm
Nagra
Vitus
Constellation
Hegel- well, they do something that is a bit different with whatever SoundEngine is

I mean, its not like in 2000 when everything was Krell or Levinson at the high end

 

[cjfrbw]

Not necessarily. Through the passband they should not be adding much in the way of impedance and you would have only the DCR of the coil. If you have resistors in the circuit that are specifically reducing the gain of a driver by 2 or 3db then you would get the loss you are describing but this is not "insertion loss".

If we take a simple passive two-way xover with no equalization of the drivers then I would argue you will get less than 1 db loss through the passband of each leg of the crossover. The AC impedance of a cap (simple 1st order xover for a tweeter) is close to zero through the passband and the inductor (simple 1st order low pass) would be basically only the DCR of the wire itself, which if a good inductor is used whould be far less than 1 ohm.

Obviously if power resistors are added because of gain matching issues then you will have losses in X db depending on the gain attenuation but then only in that frequency range so the overall power loss might not be that great (usually it is the tweeter that needs padding down to match the other drivers so this is the least power dissipation).

So, maybe for your speakers it was 3db because of resistors padding down the signal but that is not the same thing as insertion loss, which is just the inherent loss from the properties of the elements in the crossover.

There are different solutions, different results, and lots of very different passive crossover schemes. For a particular crossover, you would have to measure to be sure for that particular scheme.

You could never claim lossless passive crossover, whatever scheme you choose to use. There is also the issue of the more complex impedance of caps, coils and resistors attached to the output of an amplifier vs. the pure resistance of a directly connected ribbon to the amplifier's output.

If you are talking about preserving the virtues of an SET, including it's power output and amp response characteristics, a direct connection to a pure resistance is better than a potentially power sapping connection to a complex impedance if you can do it that way.

 

[morricab]

There are different solutions, different results, and lots of very different passive crossover schemes. For a particular crossover, you would have to measure to be sure for that particular scheme.

You could never claim lossless passive crossover, whatever scheme you choose to use. There is also the issue of the more complex impedance of caps, coils and resistors attached to the output of an amplifier vs. the pure resistance of a directly connected ribbon to the amplifier's output.

If you are talking about preserving the virtues of an SET, including it's power output and amp response characteristics, a direct connection to a pure resistance is better than a potentially power sapping connection to a complex impedance if you can do it that way.

No one is claiming lossless for the passive crossover but a few tenths of a db is a lot different than 3db. It is logarithmic and you are talking about a difference of a couple of watts vs. double the power.

A pure resistance is probably better for most amplifiers...especially those with negative feedback where back EMF can really alter the nature of the sound. Otala published a paper on this back in the 80s regarding re-injection of back EMF into the amplification chain through the feedfback loop. A distorted back EMF signal then gets ampified along with the current music signal.

Clearly a crossoverless solution is better, all things being equal. However, I do not consider most electronic crossovers to be equal. Most are opamp based (chip or discrete) and this, IMO, defeats the whole purpose of going with SET in the first place. You still have the same phase shifts associated with passive crossovers because this is inherent in all filter solutions (butterworth, Bessel, Linkwitz-Riley etc.). This loss through a passive crossover and better control over level setting are the main advantages. For example, I had the well regarded Bryston BP-10 active crossover for a while. It did what it was supposed to do just fine BUT it had an electronic haze overlay to the sound that was, IMO, unacceptable. The Accuphase F-25 was a bit dark and dynamically lacking...it had to go too. Also, digital xovers with poor opamp output stages don't sound any better.

The best solution that I can think of for active would be a very good tube based xover (maybe the Marchand kit?) but those are few and far between. A digital xover with digital outputs that can then be fed into one's DAC of choice is my preferred solution but then you have to digitize your analog...bummer.

DBX makes a $3K digital EQ that has digital outputs for each stereo set of drivers. You could buy two or three of your favorite DACs and then drive your system that way and this might sound extremely good...assuming your DAC of choice is a good one. Three stereo DACs would feed a 3-way system. One for bass, one for mids and one for highs.

 

[DaveC]

No one is claiming lossless for the passive crossover but a few tenths of a db is a lot different than 3db. It is logarithmic and you are talking about a difference of a couple of watts vs. double the power.

A pure resistance is probably better for most amplifiers...especially those with negative feedback where back EMF can really alter the nature of the sound. Otala published a paper on this back in the 80s regarding re-injection of back EMF into the amplification chain through the feedfback loop. A distorted back EMF signal then gets ampified along with the current music signal.

Clearly a crossoverless solution is better, all things being equal. However, I do not consider most electronic crossovers to be equal. Most are opamp based (chip or discrete) and this, IMO, defeats the whole purpose of going with SET in the first place. You still have the same phase shifts associated with passive crossovers because this is inherent in all filter solutions (butterworth, Bessel, Linkwitz-Riley etc.). This loss through a passive crossover and better control over level setting are the main advantages. For example, I had the well regarded Bryston BP-10 active crossover for a while. It did what it was supposed to do just fine BUT it had an electronic haze overlay to the sound that was, IMO, unacceptable. The Accuphase F-25 was a bit dark and dynamically lacking...it had to go too. Also, digital xovers with poor opamp output stages don't sound any better.

The best solution that I can think of for active would be a very good tube based xover (maybe the Marchand kit?) but those are few and far between. A digital xover with digital outputs that can then be fed into one's DAC of choice is my preferred solution but then you have to digitize your analog...bummer.

DBX makes a $3K digital EQ that has digital outputs for each stereo set of drivers. You could buy two or three of your favorite DACs and then drive your system that way and this might sound extremely good...assuming your DAC of choice is a good one. Three stereo DACs would feed a 3-way system. One for bass, one for mids and one for highs.

All of this is fine, and even necessary for the bass... steeper slopes and eq are often beneficial.

But for the bulk of the music, lower mids on up, it's not that difficult to keep it fully analog with a minimal crossover. With modern copper foil caps it's possible to make a passive 1st order xo that's VERY transparent. I use Jupiter copper foil caps, and on the mids where I need a larger value a ~50 uF Clarity Cap is bypassed by a ~2 uF Jupiter copper. Those with deep pockets could go with Duelund silver...

 

[LL21]

...DBX makes a $3K digital EQ that has digital outputs for each stereo set of drivers. You could buy two or three of your favorite DACs and then drive your system that way and this might sound extremely good...assuming your DAC of choice is a good one. Three stereo DACs would feed a 3-way system. One for bass, one for mids and one for highs.

interesting...how exactly does this work (DBX for dummies). You put in a CD into a transport...push play...and the signal goes thru 3 identical DACs, with each DAC going to a different identical amp each driving only one speaker cone or pair of L/R speaker cones directly? Does this avoid crossover entirely? or do the 3 identical DACs have to go thru 1 big digital EQ first, before THEN going to each of the identical amps (1 for each cone or set of L/R cones)? Thanks for explaining!

 

[bonzo75]

interesting...how exactly does this work (DBX for dummies). You put in a CD into a transport...push play...and the signal goes thru 3 identical DACs, with each DAC going to a different identical amp each driving only one speaker cone or pair of L/R speaker cones directly? Does this avoid crossover entirely? or do the 3 identical DACs have to go thru 1 big digital EQ first, before THEN going to each of the identical amps (1 for each cone or set of L/R cones)? Thanks for explaining!

You can also take the digital out of a DRC/Crossover box into a dac. Edorr is currently running 3 same dacs (PS Audio) for his MCH with the Evolution Acoustics MM3. BruceMck2 takes the digital out from his Trinnov to MSB.

I have a Yamamura thread here. The owner of that system (Yamamura horns, Goldmund Apologue, Vivid etc)...has a friend in Italy, who has a the crossover feeding 6 dacs, each dac feeding the driver of a horn, and each driver has monos (so 12 boxes) driving it.

 

[cjfrbw]

Actually, I prefer the sound of the F25 a lot to my previous tubed active crossover (Luxman). Japanese tube component manufacturer Air Tight have used the F25 in their active crossover live demonstrations. They probably would not have done this if they really thought the F25 was detrimental to the sound of their tube amps.

Well implemented and good sounding op amps are not necessarily deadly. The Tom Evans Linear A el84 based tubed amplifier uses op amp inputs, and he designed it to sound close to the 10 DHT output tube. http://www.6moons.com/audioreviews/tomevans/lineara_3.html. By all accounts, a good sounding amplifier: "I have to congratulate Tom Evans on what is truly a remarkable achievement in amplifier design. This chap is one of the true innovators of modern audio and marches to the beat of his own drum. His Linear A sounds better and plays music better than any SET amplifier in my experience - by a substantial margin. Coming from an SET devotee like me, I hope you realize the high level of praise that represents."

However, even I would have to hear this one to believe to that extent.

So, I suppose we could agree to disagree.

A passive crossover of a few tenths of a db would be unusual. I would be curious to see the diagram for such a lossless passive. Is it all caps and no resistors or coils? If it has the usual cap/coil/resistor scheme, I would be very surprised it it came in at less than 2db loss if actually measured. Again, one would have to measure to really stake a claim to a particular db loss. The 3db figure was garnered from the blogosphere at some point for Apogee speakers passive crossovers. Some horns just use the natural rolloff of the drivers and use no crossover at all. At any rate, 1db is 20 percent loss, 2db is 37 percent loss, and 3db is 50 percent loss. A 2db for a typical passive would be doing quite well in general.

However, the preferences for crossovers is kind of beside the point. My concern was preserving the SET asset as best as possible in the face of hypothetically antagonistic traits.

SETs do not like complex impedances, so direct driving a ribbon gives it a simple impedance against which to operate. Solid state amplifiers with lots of power, current, and high slew rates don't have a problem with more complex impedances.

SET power is also an asset that is good to preserve, especially if you DO have speakers that otherwise would have a more lossy passive crossover.

SETs are often lower powered, and usually don't deliver the high current favored by ribbons, so preserving the power asset by direct driving is desirable.

SETs have a good bit of their distortion profile below 100 Hz. Crossing over at 100Hz means less SET amplifier distortion for the higher frequencies.

The active crossover enables direct driving, no passive crossover power loss, a simple impedance, and rolling off the most distortion prone frequency range of SET amps. A three way active with two modestly powered SET stereo amps and a tube mediated subwoofer system is the way I did it, at first with a tubed crossover, then later with the F25, and it worked out very well.

What I like about DHT triode, not just SET, is the utterly dynamically open, 3D, tuneful and tone-ful nature of the sound. There are some DHT triodes that also have a quality that for want of a better term sound raw, but raw in the best sense of the word, in that they sound unfettered and as close to the signal as it seems possible to be, while still having a hypnotic quality.

 

[DaveC]

Well implemented and good sounding op amps are not necessarily deadly. The Tom Evans Linear A el84 based tubed amplifier uses op amp inputs, and he designed it to sound close to the 10 DHT output tube. http://www.6moons.com/audioreviews/tomevans/lineara_3.html. By all accounts, a good sounding amplifier: "I have to congratulate Tom Evans on what is truly a remarkable achievement in amplifier design. This chap is one of the true innovators of modern audio and marches to the beat of his own drum. His Linear A sounds better and plays music better than any SET amplifier in my experience - by a substantial margin. Coming from an SET devotee like me, I hope you realize the high level of praise that represents."

However, even I would have to hear this one to believe to that extent.

The driver section of a SET is key, and often neglected. Electraprint also uses op amp drivers. However, there are other ways to achieve a very clean sounding SET using tube circuits like mu-follower, White follower and Broski's related Aikido circuit. Currently I'm using an Aikido circuit consisting of 6SL7 > 6SN7 for my power tube driver and it's amazing, does not necessarily sound like a tube amp, I've heard SS amps that are more "tubey". But, it doesn't have the downsides of SS being a no-feedback single ended design. Basically, it uses error correction in place of nfb, a triode is used as a plate load for an identical triode, which loads it inversely, like a mirror, and cancels distortion. The effectiveness of this design depends on the triodes being matched though. Aikido also injects PS noise into the cathode follower output, which cancels PS noise. It's a neat idea that works really well. I also use a LDR/Aikido buffer preamp and my power tubes use the PS noise canceling trick... you can stick your head inside my midrange horn and hear NOTHING. No tube hiss, no ps noise, just silence.

I do think that high end discrete op amps can be excellent (not quite as good as tubes though), there are some that are specifically intended for audio and they are better than average.

 

[morricab]

interesting...how exactly does this work (DBX for dummies). You put in a CD into a transport...push play...and the signal goes thru 3 identical DACs, with each DAC going to a different identical amp each driving only one speaker cone or pair of L/R speaker cones directly? Does this avoid crossover entirely? or do the 3 identical DACs have to go thru 1 big digital EQ first, before THEN going to each of the identical amps (1 for each cone or set of L/R cones)? Thanks for explaining!

Digital signal into the crossover/EQ. Digital out bass L/R, mid L/R and high L/R. Bass to one DAC, mid to another and high to a third. Output of each DAC to a preamp or attenuator and then a stereo or mono amp. For three way you need 3 stereo or 6 mono amps.

 

[morricab]

Actually, I prefer the sound of the F25 a lot to my previous tubed active crossover (Luxman). Japanese tube component manufacturer Air Tight have used the F25 in their active crossover live demonstrations. They probably would not have done this if they really thought the F25 was detrimental to the sound of their tube amps.

Well implemented and good sounding op amps are not necessarily deadly. The Tom Evans Linear A el84 based tubed amplifier uses op amp inputs, and he designed it to sound close to the 10 DHT output tube. http://www.6moons.com/audioreviews/tomevans/lineara_3.html. By all accounts, a good sounding amplifier: "I have to congratulate Tom Evans on what is truly a remarkable achievement in amplifier design. This chap is one of the true innovators of modern audio and marches to the beat of his own drum. His Linear A sounds better and plays music better than any SET amplifier in my experience - by a substantial margin. Coming from an SET devotee like me, I hope you realize the high level of praise that represents."

However, even I would have to hear this one to believe to that extent.

So, I suppose we could agree to disagree.

A passive crossover of a few tenths of a db would be unusual. I would be curious to see the diagram for such a lossless passive. Is it all caps and no resistors or coils? If it has the usual cap/coil/resistor scheme, I would be very surprised it it came in at less than 2db loss if actually measured. Again, one would have to measure to really stake a claim to a particular db loss. The 3db figure was garnered from the blogosphere at some point for Apogee speakers passive crossovers. Some horns just use the natural rolloff of the drivers and use no crossover at all. At any rate, 1db is 20 percent loss, 2db is 37 percent loss, and 3db is 50 percent loss. A 2db for a typical passive would be doing quite well in general.

However, the preferences for crossovers is kind of beside the point. My concern was preserving the SET asset as best as possible in the face of hypothetically antagonistic traits.

SETs do not like complex impedances, so direct driving a ribbon gives it a simple impedance against which to operate. Solid state amplifiers with lots of power, current, and high slew rates don't have a problem with more complex impedances.

SET power is also an asset that is good to preserve, especially if you DO have speakers that otherwise would have a more lossy passive crossover.

SETs are often lower powered, and usually don't deliver the high current favored by ribbons, so preserving the power asset by direct driving is desirable.

SETs have a good bit of their distortion profile below 100 Hz. Crossing over at 100Hz means less SET amplifier distortion for the higher frequencies.

The active crossover enables direct driving, no passive crossover power loss, a simple impedance, and rolling off the most distortion prone frequency range of SET amps. A three way active with two modestly powered SET stereo amps and a tube mediated subwoofer system is the way I did it, at first with a tubed crossover, then later with the F25, and it worked out very well.

What I like about DHT triode, not just SET, is the utterly dynamically open, 3D, tuneful and tone-ful nature of the sound. There are some DHT triodes that also have a quality that for want of a better term sound raw, but raw in the best sense of the word, in that they sound unfettered and as close to the signal as it seems possible to be, while still having a hypnotic quality.

All I can do is report what I heard and why I left the F-25 behind YMMV.

As for the Linear A, well I haven't heard it. However, I am not inherently opposed to at least transistors (not opamps mind you) in the input and driver stages...that is exactly what KR Audio does and it works amazingly well.


Again, the only way I see 3db of loss is through deliberate attenuation of a driver to match another driver.

Funny you mention complex impedances because I got SETs to work brilliantly with my Acoustats and STAX speakers as well as Apogees. SS amps DO have problems with complex impedances. They interact with the feedback loops that most SS amps employ. Otala studied this in the 80s. The feedback loop circulates back EMF to the input of the amp, causing new and really unpleasant distortions. It is probably a big reason why some amps sound so different from speaker to speaker. My KRs were far more consistent and worked well with a wide range of speaker types. Not all SET can claim this but that is not because they are SET.

Ribbons only need high current if their impedance is really low. Later Apogees were operating at 5 ohms and above and were not current hogs.

The distortion profile < 100 Hz is only a problem with underendowed amps in the output transformer. Try a KR or an Aries Cerat...there will be no discussion of bass issues.

When you say DHT, I am assuming you mean for the output tube only or completely DHT? I have only heard one SET that was completely from inpout to output DHT and that was Aries Cerat and it is really spectacular. The Vulcan Evos I have now for review are superb as well and use a DHT driver (input is still IDHT) and output. Try a 6C33C amp sometime though, you will hear an IDHT that can deliver as well.

 

[LL21]

Digital signal into the crossover/EQ. Digital out bass L/R, mid L/R and high L/R. Bass to one DAC, mid to another and high to a third. Output of each DAC to a preamp or attenuator and then a stereo or mono amp. For three way you need 3 stereo or 6 mono amps.

Whoa...heavy duty. Definitely not one for the uneducated (aka, me). I'll take the simpler route...a good digital source into a good preamp/amp with a speaker that matches well. Thank you, though! Always good to learn!