What makes a speaker "tube friendly "?

[Deang]

http://www.symphonysound.com/articles/tubefriendly.html

Cornwall II

RB-5

From Al's site, comparing the ALK with the Klipsch Type AA.

"An equally important factor is the impedance load your speaker provides to your amplifier. The Klipsch network, even with perfectly resistive loads connected to the network in place of the drivers, looks reactive (capacitive or inductive as can be see on the top +-180 plot) and varies from less than 8 Ohms to nearly 30 Ohms over the audio range..."

[HDBRbuilder]

BUT...drivers aren't "perfectly resistive loads"...and "MUSIC don't come out of no oscilloscope and frequency generator" (this last part is MY quote)

After tests were successfully completed achieving desired results using the testing equipment in the lab for speakers inside the anechoic chamber...PWK STILL always used to say..."Looks good...now let's give them a LISTEN!" Soooo...

A more proper question might be "what makes a tube amplifier KlIPSCH-friendly?" After all, it is the upstream equipment that determines what comes out of the speakers...right? This smacks of "sweeping generalizations", because even on tube amplifiers, things vary somewhat in what your ears hear by just changing from one tube type/brand to another.

Putting perfectly resistive loads on a network that is not gonna be sending signals and power to drivers with "perfectively resistive loads"...and using a frequency generator in place of music will not do much more than give you a bunch of lab results that have no EXACT representation of how that network performs using music and those particular drivers...OR how it sounds to your ears. BUT there is another consideration here...maybe when the network with its lab-tested nuances off the "straight line" is combined with the NON-perfectively resistive loads of the drivers using music instead of generated signals...it just may flatten-out instead of remaining "off the line".

It seems strange that many are aware of lab-testing results showing severe dips or peaks in the area of certain frequencies on tested speakers, but swear they can't HEAR it when listening to MUSIC on those same speakers...and IF they do something to the speaker to correct the problem found in the lab results, then the speaker just doesn't "sound right" to their EARS anymore...maybe this is why. Maybe it is because it is MUSIC instead of generated frequencies...and when music is actually used, on those non-perfectly resistive drivers, those lab results kinda go out the window...because when combining the discrepancies in a particular network, with the actual drivers being used on a musical signal, everything "lines-up" instead of remaining as expected from the lab test results. After all, we all know that different amps sharing identical lab test specs seldom sound the same on a particular pair of speakers...and that changes in other upstream components tend to make a difference in the sound, even though they share identical specs...so why don't we also face the fact that this happens in the speaker itself in its own unique combination of drivers, networks, and music signals instead of putting our faith in lab tests that use frequency generators and perfectively resistive loads?

Either way...whether it makes a difference or not, it is still interesting to read all of these testing results while I listen to my stock Heresys and they sound perfectly fine to me.

[jt1stcav]

Hmmm...And so my bone-stock Cornwalls with their original, PWK-designed crossovers won't be as tube friendly as an exact Cornwall with modified/updated crossovers?

I dunno...they sound awfully good to my ears playing my favorite music, as opposed to the test tones plotted on lab charts and graphs from lab techs/engineers in their white coats.

Guess it sucks to be me...

[chops]

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On 5/23/2004 6:50:26 PM jt1stcav wrote:

Guess it sucks to be me...

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I'll say!!!! LOL!

[garymd]

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On 5/23/2004 9:32:27 PM chops wrote:

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On 5/23/2004 6:50:26 PM jt1stcav wrote:

Guess it sucks to be me...

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I'll say!!!! LOL!

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Only a brother could get away with that!

[hoggy]

Not to be offensive or anything; all I hear is tube this tube that ss not good with khorns compared to tubes etc. etc. etc. Will someone in the Seattle area bring over their tube amp to compare with my McIntosh MC 352. I'd like to a-b them and see what the fuss is. I'd offer to bring my amp to one of their houses to compare but it weighs a ton.

hoggy

[jt1stcav]

hoggy, I can tell you that all the Mac amps I've used (MC7200, MC2100, and MC250) are all great sounding SS amps with Klipsch loudspeakers! Also Aragon, Adcom, Yamaha, and harman/kardon SS power amps work extremely well. Although I've never heard one, the lil' SS Monarchy Audio SM-70 is about THE best transistor amp money can buy with Klipsch in mind, and many here on this forum can attest to that fact.

Just my opinion, natch...

[Deang]

I'd really like to hear some MacIntosh solid state sometime. I've never heard a bad a thing about it, and everyone that hears it seems to like it a lot.

I know I liked the Aragon 4004 MK II on my RF-7s quite a bit -- but the tube amps I had in the house at the time to compare with just sounded clearer for some reason.

I understand where you are coming from Andy, but it's not really where I'm coming from.

Jim, did you read this part:

A speaker that doesn't perform well on tubes will typically be characterized by one or more of the following sonic traits when connected to a tube amp:

Dual-mono imaging, i.e. the speakers do not "dissappear"

Unusually poor imaging or soundstaging

Lumpy, bloated, or "one note" bass

Lack of control in the bass - excessive boominess or thumpiness

A "suckout" in the midrange

Whenever the bass kicks in, the mids go away

Whenever the bass kicks in, the highs get harsh and strained

When you hook the speaker up to a solid state amp, the bass gets tighter, the midrange comes back, and the highs mellow out The above traits are exaggerated on SET amplifiers. Some speakers are push-pull friendly but not SET friendly. Push pull amps, even with low power ratings, are typically capable of driving more demanding or capacative loads than SET amps.

When you get the amp from Edmund -- place a Mills 12 watt, 15 ohm resistor in parallel with the amps outputs.

[chops]

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On 5/23/2004 10:32:24 PM DeanG wrote:

Jim, did you read this part:

A speaker that doesn't perform well on tubes will typically be characterized by one or more of the following sonic traits when connected to a tube amp:

Dual-mono imaging, i.e. the speakers do not "dissappear"

Unusually poor imaging or soundstaging

Lumpy, bloated, or "one note" bass

Lack of control in the bass - excessive boominess or thumpiness

A "suckout" in the midrange

Whenever the bass kicks in, the mids go away

Whenever the bass kicks in, the highs get harsh and strained

When you hook the speaker up to a solid state amp, the bass gets tighter, the midrange comes back, and the highs mellow out The above traits are exaggerated on SET amplifiers.

Some speakers are push-pull friendly but not SET friendly. Push pull amps, even with low power ratings, are typically capable of driving more demanding or capacative loads than SET amps

.

When you get the amp from Edmund -- place a Mills 12 watt, 15 ohm resistor in parallel with the amps outputs.

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That has to be one of the craziest things I've heard yet. In fact, the only time jt1stcav's Cornwalls really sounded transparent was when he used a Jolida JD202A of our other brother's in his system for a short while. The bass WAS still tight, the mids WERE very present, and the treble WAS smoother than usual. The soundstage width was about 3' beyond the speakers and about 10' deep. Imaging wasn't the greatest, but look at the size room they are in.

And that's not the crossover networks causing the various loads on the amp. That's the speakers (drivers) doing that at different frequencies.

Not to sound mean or nasty, but maybe you should consider that instead of just plugging you crossover upgrades.

[Deang]

Where was I plugging my own work? Besides, I can't promote anything I do in this context because I don't design networks, I just offer parts ugrades to stock boards. If I was plugging anyone's crossovers it would be Al Klappenburger's, since Al's Type A Replacement pretty much presents a stable resistive load to the amp -- ideal for some push-pull amps, but especially SET amps, which will track the impedance curve, creating non-flat response.

It doesn't surprise me that the Jolida sounded good on the Cornwalls. Most decent vintage push-pull amps aren't really all that prone to the problem, and modern day push-pull tube amps are designed with this in mind from the start. I underlined the following for a reason: "Some speakers are push-pull friendly but not SET friendly. Push pull amps, even with low power ratings, are typically capable of driving more demanding or capacative loads than SET amps." -- of course, this is where I was trying to go from the beginning.

However, I also wanted to do it for educational reasons. A lot of questions have been coming up about power again, and the answer that's always thrown out is -- "Hey, you've got Klipsch speakers, you don't need any power." But now we know that if a speaker is reactive, even if it has great sensitivity -- can NOT and will NOT be an accurate reproducer using complex material at live listening levels. More times than not -- with power comes stability.

"And that's not the crossover networks causing the various loads on the amp. That's the speakers (drivers) doing that at different frequencies."

Actually, it's the combination of the drivers and the crossover together. You can make small changes in a network, and cause large changes in impedance.

The resistor tweak was taught to me by Leo here on the forum, who I believe actually still uses a 10 ohm resistor on the outputs of his zero-feeback push-pull amp when driving his RF-7s. DJK, another engineering type who frequents the forum, saw the thread, and suggested that a 15 ohm resistor might work better. I tried both and preferred the 15 ohm resistor. The Cornwalls dip down and climb up through the frequencies in a way that is similiar to the RF-7. Adding the resistor helps by smoothing out the impedance of reactive speakers/networks. With zero-feedback push-pulls, and certainly SET -- it's a good tweak, and definitely sounds better to me. I thought Jim might like to give it a try with Edmund's SET amp.

[maxg]

And enter the technical chimp into the discussion....

A number of things from the article surprized me, and a number I just dont understand....in no particular order as follows:

1. Sensitivity:

Seems to me that if your speakers are more sensitive then the number of watts being used to generate your chosen sound level will be less (than with lower senstivity speakers). If this is the case then the combination of Volts and Amps is correspondingly less and the ill-effects of impedance changes will be reduced in terms of the demands that place on your tube amps.

In other words - it is not that tube amps need a steady load in as much as they simply are not good at providing for (sudden) high current demands. As Watts are smaller in number, in this example, the amps being demanded at any point in the frequency spectrum is correspondingly smaller and therefore have more chance of remaining within the capabilities of said tube amp.

Correct? If so the whole opening section of the article shouldbe re-written.

2. Back EMF:

A Large driver returning from maximum excursion to its centre point (or even to maximum excursion in the opposite direction) generates negative amps (as seen be the amp itself). This results in - according to the article - ".. the result of the bass frequencies exciting a large, "floppy" driver which in turn generates Back EMF and lowers the impedance. "

Confusion - hello!!! Why, if the amps are negative from this excursion do these not serve merely to reduce the current draw on the amplifier itself? In other words won't higher levels of back EMF make a speaker more, rather than less, tube friendly?

3. The Cornwall diagram:

Is there a graph showing what happens to the phase over the spectrum as well as to the impedance? If the phase is moving in reverse then, at least according to the article, this might explain why Cornwalls are tube friendly despite their rapidly changing impedance.

Of course it does seem that Cornwall impedance never drops below 4 ohms anyway - so it never gets that unfriendly. I wonder if there is such a graph around for the Final 0.3 speaker (a hybrid panel / woofer unit). I have heard that this speaker drops down to 1 ohm in places. Definitely not tube friendly - however slowly it does it.

4. A very recent experience:

On friday I went off vinyl buying. In the shop I bought from they were running a pair of RB5's connected to a pair of push pull 300B monoblocks with 2 tubes per side and 20 wpc. These were running off a tube pre-amp and a vinyl rig with a Denon 103 cartridge.

In other words - the above should be something near to an ideal setup on the face of it. The only obvious issue was that the speakers were mounted on wall brackets very high up - about 6 inches from the ceiling - and one would expect that to have a negative impact on the sound - but nothing compared to the result.

The setup produced quite the hardest sound it has been my displeasure to hear in a long long time. This made my original Heresy / Yamaha receiver / Rotel power amp sound lush and warm. I could not believe how bad it was. I do not think the placement alone could possibly account for this (although I could be wrong). There must be something else afoot. I have no idea what - but this article leads me to believe that maybe, just maybe, the RB5 is a sensitive speaker that does not lend itself to tubes.

Anyone running RB5's with tubes care to comment? Shocked the hell out of me!

[Erik Mandaville]

It's sometimes called a 'Swamping resistor.' I use a 5 watt 20 ohm across the binding posts on my Lowthers.

[HDBRbuilder]

Mdeneen, quite frankly, I am SHOCKED by some of your wording! I am an old paratrooper who is admittedly lewd, crude, abusive, and socially unacceptable, but even I would not call somebody a moron, imbecile, idiot, or whatever on this forum! I might, however, be inclined to use old paratrooper terminology like "he has his head up his fourth point of contact".

PWK would have had something to say, but unlike you, he wouldn't have written so much down in order to say it...more likely, he would have just reached into his pocket and pulled out one of his yellow buttons, instead.

[burtlively]

alright, so i've read this thread in its entirety. i might as well been reading chinese. what does all this mean to me, the average joe? i look at the chart w/the cornwall and the rb-5. what do the charts say in laymen's terms?

[Colin]

Excellent link Deano, thanks, except after reading it one would think that some big ole horns might NOT sound great with tubes: NOT! IT also says nothing about the edginess, harshness and fatigue that super-sensitive loudspeakers reveal with solid-state amplifiers. Despite all the science, one double blind study I know of shows that people who dont what they are listening to prefer tubes (and vinyl) on cone loudspeakers.

It isnt just watts, is it? It is how many watts into what load? The ability of solid-state amplifiers to push (?) more current into lower impedances gives them better sounding bass. If a tube amplifier could double its flea-power into half the impedance, it would sound great too.

Max- the tubes might have been old and need replacing

Mark, I dont know about steady loads, I think that tubes dont like low impedances, so the frequency response of loudspeakers on tubes resembles the speakers impedance, NOT the tube amplifiers measured flat response

no insults, play nice

[Colin]

oops- ditto

[Deang]

Colin said, "Mark, I dont know about steady loads, I think that tubes dont like low impedances, so the frequency response of loudspeakers on tubes resembles the speakers impedance, NOT the tube amplifiers measured flat response."

Thanks Colin, that's the jist of it -- but just some tube amps, not all of them. I don't know how this got turned into the idea that I'm slamming all tube amps. I was trying to point out that just because a speaker has high sensitivity, doesn't automatically qualify it as a candidate for any and all tube amps.

Mark, I really think you're being unduly hard on the guy. Poor verbaige aside, and taken in context, his comments parallel everything I have ever read on the subject -- including what you've told me over phone when I asked you about it in the past. You quoted the latter part of the paragraph, but the former part says:

"Tubes like a resistive load - it's really that simple. A resistive load translates to a flat impedance, and an inductive rather than a capacitive phase angle. A less technical way of looking at an ideal speaker from a tube's point of view is as follows: tubes like consistency. They prefer a speaker that doesn't swing from 8 ohms to 2 ohms and back again. If the impedance is going to dip it should do so gradually, or in small dips."

He ends by saying:

"As you can see, an understanding of audio equipment's measurable characteristics is fundamental to building a good hi-fi system, regardless of whether you plan to use a tube or solid state amplifier. It is difficult to make generalizations about the quality of a given speaker or amp in terms of its measurements. There are many wonderful sounding loudspeakers which present extremely demanding loads and are simply ill-suited to tube amplification. On the other hand, there are speakers which are easily driven and present benign loads but which are perhaps not the finest examples of acoustic engineering to be found in our industry. As has been discussed at length in magazines and forums for years, one cannot make a simple connection between measurements and performance. Nevertheless, we believe that to ignore measurements is to limit the performance of one's equipment."

I agree with these statements, and even though I don't know much about electronics or tube amps -- it seems to me it lines up pretty good with everything else I've read. Simply put, benign impedance curves seem to be a prerequisite for SET use -- at least, that's what the SET manufacturer's say about their own amps.

Your post from last year on this same subject was much more useful to me than this last one.

What's not plainly discussed therein, is the fact that what is important when speaker meets amplifier, is the resultant ACOUSTIC POWER CURVE, or SPL. Naturally the speaker has this wavering impedance curve because it is a reflection of the mechanical and electrical resonances within the entire speaker system - drivers and crossovers.

When a driver (or circuit) is at resonance, not only does the impedance rise, but the acoustic output rises and given the fixed voltage of the amplifier, the amplifier power "drops", but the SPL is level. In other words, the driver is most efficient at the zenith of resonance and least at the nadir. And accordingly, the amplifier "power" is the opposite. If this were not true, speakers and amps of all types would simply not be listenable!

The amplifier power output measure is simply E^2/Z. So, if you put a 4-ohm to 100-ohm pot on an amplifier and set the amp to 1V out and twist the pot back and forth, the power will rise and fall to the tune of E^2/R. And so, speakers have this wavering impedance curve, but when mated to almost any amplifier the ACOUSTIC POWER CURVE (SPL) - the part you hear with your ears - is generally very level and very independant of amplifier type (given the amps are operated in their rated ranges.).

The more important issue with such impedance curves is not even discussed there, which is distortion. The tube amp using an output transformer reflects the LOAD impedance back on to the output tube - that's what a transformer does. Since the output tube has an "ideal" load - and the transformer is designed to reflect this ideal on the tube at the "nominal" impedance values of the ouput taps, when this load impedance changes, the operating characteristics of the output tubes CHANGE. And this change means more distortion.

When distortion is measure for a tube amp, it is nominally stated as X% @ 8-ohms @ full power. This obviously assumes the ouput tube is seeing 8-ohms "as reflected back" through the transformer. But when the load goes to say, 40-ohms, this is reflected back and multiplied and the output tube is now looking at a load that is 5X the ideal load, or in the case of a 4-ohm dip, a load that is 1/2 the ideal load. Well, you can't expect the distortion to remain constant, because it won't.

Now comes the potential issue with SE amps. They already have low power output, and most have little if any negative feedback around the transformer. So, they are affected much more gravely in the area of INCREASED DISTORTION when the load changes the operating point of the output tube. Since these amps already have very substantial distortion under "ideal" load, it only gets worse as the load changes.

A push-pull amp with negative feedback reduces the impact of impedance change AND lowers the inherant distortion.

So, if distortion rises from say, 0.5% to 1% in a PP amp, this is still tolerable. But in the SE amp, the distortion may rise from 3% to 10% and this is clearly audible as coloration. Now this distortion in SE amps is 2nd and 4th order - and it is not a "nasty, raspy, harsh" type of distortion, so it has a very passable, euphonic characteristic. But it does add a great amount of tonal coloration. On the other hand, SE amps can sound more open, airy, spacious and dynamic (within their limited power range.) So, as always, you pay your money and take your chances.

SS amps do not suffer like this because they are inherantly very low output impedance devices. There's nothing improper about using a dummy load to measure the amplifier. But a more valuable measurement to me with this dummy load would be the amplifier's distortion curve.

mdeneen

[Deang]

You can't possibly be saying that wild swings in impedance don't impact the measured frequency response of some tube amps, or that some amps will in fact track impedance. Well, I guess it's all magic after all.

[Colin]

I am saying that most speakers - the ones we are familiar with - have impedance

curves that present no particular problem to tube amps.

Big ole horns are NOT most loudspeakers. I have seriously auditioned, in my home, with the same equipment and the same music, for EnjoyTheMusic.com, about a dozen cone loudspeakers. Most of them had lower extended bass and more mid-bass punch with solid-state amplifiers than with tube amplifiers, albeit with some loss of mid-range magic and imaging. The notable exception was CAR Cinema Ensembles (horns).

Now, given that each amp has a unique topology, and each speaker is a

unique load, how do you "generalize" about tube amps or SS amps? Remember, it's ONE complete circuit all interacting.

Unfortunately, I am at the population science level, so I appreciate articles such as this one. One can generalize about the complete circuit. The frequency response of a loudspeaker driven by a tube amplifier is different than the loudspeaker is driven by a solid-state amplifier.

The cherry Coincident Technologies Triumphs, for example, are supposed to be tube friendly loudspeakers, just NOT friendly to flea-powered Bottlehead 2A3 Paramour monoblocks.

It may be that our big ole horns are NOT in fact tube-friendly, but that their awesome sensitivity covers up al sorts of ills.

It IS difficult to make generalizations about the quality of a given

speaker or amp in terms of its simple nominal (read useless) measurements. That is why every loudspeaker and sub should include an impedance chart on its back, so tweaking audiophiles can see how low or steep the impedance curves actually are because the single nominal tells so very little.

Made me think a bit about those magnificent Quads there deano, until you said

SE amps can sound more open, airy, spacious and dynamic (within

their limited power range.)

yeah baby, thats what I like about big ole horns

[Deang]

"It may be that our big ole horns are NOT in fact tube-friendly, but that their awesome sensitivity covers up al sorts of ills."

The ills they are covering may not be related to just their high sensitivty, but to their wide dynamic range as well.

SE amps can sound more open, airy, spacious and dynamic (within their limited power range.)

Push-pulls can do the same -- you just have to play them a little louder.