Matching the power amplifier to the loudspeaker is usually a function of driver size, efficiency and budget. Efficiency is not the only determinant – even though they may be very efficient, many speakers with large drivers need tremendous amounts of damping factor and current capability to control the driver properly. @hilde45 This quote from VTL is largely false. The diameter of the driver has **nothing whatsoever** to do with the ability of the amplifier to ’control’ it (although I will concede this is a popular myth)! What **does** matter is the relationship between the amp and driver. To give you can example, my speakers at home employ dual 15" woofers, which by most accounts are large drivers. Yet they are easily controlled by our little S-30 amplifier which has a very low damping factor. This is because the designer of the speaker prefers smaller tube amps, and our S-30 has full power bandwidth to 2Hz. The size of the drivers (TAD 1602s for anyone wondering) is irrelevant. That same manufacturer (Classic Audio Loudspeakers) features an 18" driver in their next model up, yet no worries controlling it with the same amp! In fact, our MP-1 **preamp** by most accounts would seem to have an output impedance too high and power too low to be able to drive a loudspeaker, but it does more than a passable job on both of these speakers as long as you don’t need more than a conversational volume level- and the bass is just fine! So don’t be fooled by the high damping thing- it isn’t real. Well, it seems that audiokinesis put me in my place. Hey guys, it's
just been my experience that woofers are quicker and tighter with a
higher damping factor amp.
'Tight bass' is a coloration that does not seem to exist in the real world. You only hear it or hear about it when dealing with audio reproduction. Admittedly, its popular, but probably in the same way that turning up the bass tone control can be pleasing- pleasing, but not natural and not neutral. |
@atmasphere re
Thanks for correcting VTL. I'm surprised they're out there with such false information.
I'm grateful to bury the damping thing. Clearly, it refuses to die, generally.
There may be different senses of what 'Tight bass' means. One way I take it is that a speaker emulates a string bass similar to one at a good seat in a jazz club — clarity in the fretting, the pluck, and a bass-like attack and decay of the note. What I've been hearing from my speakers, at times, is a bass-colored fog. That's at least what I mean by that phrase.
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@atmasphere +1 An amplifier, cables and speakers form a system in which they interact. Anyone who claims one thing in particular is a panacea for all ills is prevaricating. To wit, from MBL Noble Line N11 line preamplifier @ https://www.stereophile.com/content/mbl-noble-line-n11-line-preamplifier "Some of my work involved tuning the power supply. It may come as a surprise to learn that you can change tonality without even touching the signal path, because the signal originates from the power supply. The impedance curve of the N11’s power supply is absolutely homogenous from DC to 200kHz, which creates a very balanced sound. I also tuned the resistors for the voltage gain, using a mix of carbon and metal resistors to create a neutral balance. There are a lot of preamps that claim to be ’neutral’ or ’in balance,’ but there are different shades of ’neutral.’ If you have a tube preamp, for example, ’neutral’ is at a different level than solid-state; it’s not better or worse, but it is different. It took a lot of work to find the tonal balance I like a lot that measures well, with low noise, and fits very well in the Noble Line." [emphasis added] One can only assemble a system in one’s locale with one’s components. All else, especially idiot topics "What [insert device here]?", is pure folly. |
I recently purchased a pair of floor-standing Revel 328s (sensitivity 91dB, recommended power 50-300W). I'm driving them with a Raven Nighthawk tube amp (20 wpc, high current IA). Question: Am I harming the speakers by underpowering them? |
@nakam Yes you can mess up the tweeter if you drive the amp to clipping. The recommended amp range is an estimate the speaker company uses as a guide for consumers as long as you don't push the amp which means listening for clipping even in moderate listening levels at the transients. |
When the amp clips the current doesn't alternate but behaves like DC which the capacitor in the crossover will pass, especially bad for tweeters. |
@nakam @djones51 When the amp clips the current doesn’t alternate but behaves like DC which the capacitor in the crossover will pass, especially bad for tweeters While I of course agree that overdriving an amp to the point of clipping, or at least severe clipping, can and will often damage tweeters, and while many audiophiles apparently believe the quoted explanation, that explanation is not correct. Capacitors are commonly used to **block** DC. Consider for example the coupling capacitors that are used at the outputs of many tube-based preamps or other line-level components, or that are used to couple signals between active stages within those components. They are there to block DC, perhaps among other reasons depending on the particular design. Also, the impedance presented by a capacitor **increases** as frequency decreases, and DC is zero Hertz. Following is an explanation of why a clipped amp can damage tweeters, quoted from a post I made in a thread back in 2011: The reason that speakers are commonly damaged by clipping of underpowered amplifiers is essentially as follows: Clipping occurs when the amp is asked to deliver a larger voltage swing at any instant of time than it is capable of delivering. That will usually occur at bass or mid-bass frequencies, where music typically contains its highest energy levels. Clipping means that the positive and negative peaks of what would normally be a smoothly varying waveform will abruptly transition to a flat, essentially constant output level corresponding to the maximum positive and negative voltages that the amp is capable of delivering.
The ABRUPTNESS of those transition points corresponds to high frequency spectral components being present in the output signal that are not present in the original waveform. In other words, the clipped waveform contains excess high frequency energy, which the speaker’s crossover will duly route to the tweeter. That can occur even if there is no high frequency energy at all in the original signal, as a result of the clipping of bass frequencies. Tweeters are ordinarily able to handle much less energy than lower frequency drivers, and can therefore be damaged by that excess energy.
Solid state amplifiers will typically clip more abruptly than tube amplifiers, therefore making them more likely to cause that kind of damage. Although if a tube amp is clipped severely enough, the same damage can result.
Severe clipping will be immediately obvious, because the sound will be horribly distorted. The onset of clipping may be characterized by mild distortion or slight popping sounds on musical peaks. I doubt that occasional mild clipping would cause any damage. @nakam, with regard to your specific question note particularly the last paragraph above. Regards, -- Al |
@nakam
20wpc is good for 96db @ 3.5m w 91db 2.83V/8Ω/1m speakers
Plenty loud.
Speaker impedance may change the above somewhat |
@almarg So the tweeter getting to hot from excess energy would cause failure? If occasional mild clipping wouldn't cause any damage, how easily would it be to detect mild clipping in LF leaking into the HF area of the tweeter? Could this type of clipping be easier to not notice in lower powered tube amps causing not occasional clipping but a lot? |
@djones51, not sure what I can add in response to your questions other than the generalities I stated at the end of my previous post. Basically, the more severe the clipping is the more likely it is to be noticeable, and the more likely it is to cause damage.
Regards,
-- Al
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OK thanks, I never listen that loud anymore the last time I blew a speaker had to be 1974. |
To add to my previous posts on this subject, an illustration of what a clipped waveform looks like: https://www.mtx.com/i/mtxcom/clipped-signal.jpg As you can see it alternates (going both positive and negative), as does the original signal of course. So it is not DC, which the series capacitor that is commonly part of the high-pass section of a speaker’s crossover network would block from reaching the tweeter even if it were. +Vcc and -Vcc shown in the figure represent the maximum positive and negative output voltages the amp can provide into the particular speaker load. Also, note the sharp discontinuity between the smoothly rising or falling parts of the waveform and the flat top and bottom. The frequency components corresponding to that sharp discontinuity contain the excess high frequency energy I referred to. (Examining the clipped waveform with a spectrum analyzer, which indicates the various frequency components of the signal, would show that). Most of that excess energy will tend to be routed to the tweeter by the crossover network, since it is at high frequencies. Regards, -- Al |
@djones51
A square wave is an infinite series of odd harmonics above the fundamental. When an amp clips, the waveform stops at the power supply limit and creates an odd multiple series of the clipped fundamental. Below is an abreviated list of 200Hz odd harmonics to 20kHz. They continue forever. As you can see, they cover all driver ranges. Note that if only a portion of the wave is clipped, that period is the fundamental and the odd harmonic progression starts there. 1% clipping @ 200Hz starts @ 20kHz and continues upward. On a 200wpc amp, that’s 200w into the tweeter for a few µs. 200Hz 10% clipping starts @ 2kHz and supplies full power for a dozen plus full power harmonics continuing to the amplifier bandwidth.
H# Hz
003 600
005 1000
007 1400
009 1800
011 2200
...
091 18200
093 18600
095 19000
097 19400
099 19800
101 20200
Music has an approximately 50% power ratio per octave and acoustic instrument harmonics are only a fraction of the fundamental, so there is very little power actually sent to the HF driver. [Electronic instruments, buzz guitar and heavily Eq’d program can have a grossly skewed driver eating power spectrum.]
Hz Pwr %
200 100%
400 50%
800 25%
1600 13%
3200 6%
6400 3%
12800 2%
25600 1%
When a tube amp distorts, there is a fair amount of lower even [2nd & 4th] harmonic distortion which is a good indication the amp is losing control and gives fair warning. A good SS amp with robust power supply gives no warning and dumps the full spectrum willingly. By the time user hears it, it can be too late for the HF driver.
Hence a low power SS amp into inefficient speakers is more of a risk.
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Yes, the Nighthawk's specs are 20 watts per channel: (8Ω, 1% THD). If you follow John Atkinson's measurements in Stereophile, he often has to allow higher levels of distortion, e.g. 3%, to get a tested tube amp to achieve its manufacturer-specified output. The amp will put out more than 20W but as almarg says with increasing levels of distortion. |
For this reason, the argument that only speakers with an impedance of 8
ohms or higher will work on tubes is incorrect. There are many tube
friendly speakers whose nominal impedance is 4 ohms. If the speaker’s
impedance is relatively flat and consistently hovers around 4 ohms, and
if the phase angles are only slightly capacitive, or better yet
inductive, there is no reason why a 4 ohm speaker cannot perform well on
a tube amplifier. Some of our favorite tube friendly speakers are 4
ohms!" I missed this earlier but the fly in the ointment here is that all amps regardless of technology make more distortion into lower impedances- and that distortion is audible- the difference being, if you just want a good stereo, 4 ohms is fine, if you want it to sound real then higher impedances will help out by keeping amplifier distortion down. Tube amps in particular like higher impedance loads for another reason as well- if the amp has an output transformer, it will make deeper bass into higher impedances- the lower the load impedance, the less efficient the output transformer becomes and it will roll off faster on the bottom, by as much as an octave! This can result in phase shift, robbing the amp of impact. So the tweeter getting to hot from excess energy would cause failure?
If occasional mild clipping wouldn't cause any damage, how easily would
it be to detect mild clipping in LF leaking into the HF area of the
tweeter? Could this type of clipping be easier to not notice in lower
powered tube amps causing not occasional clipping but a lot?
Tube amps have a soft clipping character that solid state amps do not. Essentially you get less higher ordered distortion, which is what damages the tweeter. Since its the higher ordered distortion of powerful low notes that usually overloads an amp, the distortion has some power too. The crossover won't stop these harmonics since they are the frequencies that are supposed to pass. So the tweeter gets fried. Generally speaking, its solid state amp clipping that damages tweeters. You can usually get away with it with tube amps unless you clip them really hard. |
Thanks for the information, just goes to show it's best not to repeat what one has heard for years. I read about 2 hours last night, articles on clipping and tweeter distruction. I think everything both almarg and ieales explained was mentioned though it's hard to remember everything I read. Anyway I apologize for hijacking the thread, back to speaker and amp matching. |
Look at all of Fritz’s speakers impedance curves. Absolutely outstanding. I would have to assume that it is due to his exceptional crossover design. It’s also why some people report that his speakers have sounded really good driven by 8 watts. It’s not always about sensitivity.
I am absolutely smitten with his Carreras. Fantastic speakers that are making me upgrade the rest of my system because the music they
are making in my listening room is intoxicating, addictive and downright therapeutic.
Anyone in the Colorado Springs area is more than welcome to stop by once I get my new integrated and hear these wonderful speakers!
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You can clip a tube amp all day and no harm will come to drivers...ask any guitar player. |
guitar cabinets typically don't have tweeters or crossovers
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FWIW I have a fairly low power tube amp, Manley Stingray, 38 watts UL or 19 watts triode, that drive my floorstanders with tight authoritative bass and sweet open mids and highs. The speakers are somewhat vintage Audio Physic Scorpios. They each have 4 side firing 7” woofers and are rated at about 91 db - pretty efficient.
I’m pretty certain that your amps would make them sing also. If you can find them, their price would be reasonable, and probably pretty re-sellable if they didn’t work out. Very pretty too.
Not sure if current Audio Physics, which are fairly expensive, live up to the original founder’s sound quality.
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Thanks. The only Audio Physic speaker near is Audio Physic Tempo, used for about $1k. |
I would agree with a few of the others and think about taking a different speaker path..along the line of anything hi-efficiency / sensitivity. ie....such as Zu, Klipsch Heritage series...Tekton...Tyler Acoustics PD series...and numerous others...etc.
Your QuickSilver amps will then set you free with everything it is that you want..with plenty of dynamic headroom, swing, and presence. Once properly implemented, be prepared for a music listening revelation.
while your Adcom seemed to have some positive attributes..you also mentioned a few negatives. Those negatives will never really go away completely..as the Adcom stuff is limited by what it was..that is to say..consumer grade “mid-fi” gear at best.
If you want to stay with the Focals, you might want to put some nice class A juice to them (Pass, Plinius, or old Krell KSA?) to really have them open up.
have fun!! |
@clhs04 Thanks so much for your post. I have some lower priced Klipsch RP 600M's and they are so easy to drive. I don't think these speakers are right for my listening area — they're kicking butt in my home theater, but their mids and highs leave something to be desired (harsh to my ears).
I've returned the Focal 936s to the shop that loaned them. After two weeks of listening, their tweeter still sounded harsh and these had some miles on them. I noticed there are a lot of Focal 936s for sale used out there, lately; I don't know what's up with that; could be nothing.
I've located some really nice Legacy speakers here in town, but the dealer (who mainly does installations) won't let me take them home to try them and so I really don't see myself going with Legacy without a trial. Their AMT style tweeter and their sensitivity both seem great for my QS but…I need to try at home.
I appreciate your mention of a couple brands I've never heard of, including Tyler. Something to look around for.
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I’m sorry to perseverate but let me clarify that I meant Klipsch “Heritage” series speakers only. A great segment of audio listeners have a general perspective that Klipsch’s are too bright or too forward or harsh. Most are only listening to generic consumer grade Klipsch’s thru a generic consumer grade AV receiver. Listen to a set of LaScala’s or Forte’s thru a triode system and you’ll become a believer.!
as far as Legacy speakers go....they are very good ..and Bill D. has been around and advancing his designs for quite some time.
however be advised QuickSilvers will not get it done..and those speakers deserve amps that commensurate quality wise. A lot of folks often put Coda amplification behind them.
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@hilde45 What part of the country do you live in? |
@clhs04 Point taken. Another person is also pointing out how different the better Klipsch are — I recognize (thanks to you both) that I need to understand things differently. Gotcha.
It's interesting to hear that the QS 60w Monos won't be enough to drive the 94 db Legacy speakers. Or maybe you're not saying that, exactly, but rather that the amps are not sufficiently good enough quality wise? I have very good tubes in them…
@timlub I'm in Denver.
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Legacy‘s are large cabinet big multi-driver speakers that demand a lot of current..despite what their persuasive specs regarding sensitivity may imply.
if you were to do a generalized perusal online of Legacy speaker systems I would bet that > 50% of the guys are using high current muscle amps to run them. In fact Legacy has or had their own line of amps... I suspect that Coda was in some way involved. In fact Coda amplifiers are ideal in that they are high current designs and highly biased in class A as well.
im not saying the QuickSilvers are “bad” in fact they are good in the context of their application. That said I think wrong tool for the job with Legacy speakers.
60 WPC is ideal / great for your highly efficient speakers such as those that were discussed prior. However with Legacy anything I think I would want to start with no less than 100 wpc (or more). Too little power = not good. There is no such thing as too much power..it will give you gobs of headroom even at the lowest listening levels.! |
@clhs04 Legacy‘s are large cabinet big multi-driver speakers that demand a lot of current..despite what their persuasive specs regarding sensitivity may imply. if you were to do a generalized perusal online of Legacy speaker systems I would bet that > 50% of the guys are using high current muscle amps to run them. Fact check for the other 50%, various tube amps used successfully with Legacy speakers. It doesn't take an overpriced Coda to run them. Not all tube amps are created equal, it all starts with the transformers. As suggested, a quick five second search: |
help!!
@decooney has me on the ropes here....somebody bail me out! just kidding folks I agree and actually I’m all for tube gear myself...my Viva has some of the largest transformer iron I’ve ever encountered in my life.
Not to totally derail this thread but did @hilde45 ever mention what preamp he is using.? That’s a whole nother rabbit hole to go down in. |
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@clhs04 Not to totally derail this thread but did @hilde45 ever mention what preamp he is using.? That’s a whole nother rabbit hole to go down in.
------------------------------------- heheh, ah just having some fun here with ya, it’s all good. He’s running a Quicksilver Linestage, non-remote control version preamp. They sound pretty nice with good vintage tubes and drive QS Mono 60 amps just fine. To your point, and others, you cannot simply throw just any amplifier at these types of loudspeakers, agree 100%. I grew up here in the land of PASS, Coda, ESS where it all started with AMTs too and it truly does take a better amplifier to help these types of speakers sound their best. Even AMTs sound "right" with a ballsy amp. You are correct sir. I would not throw a dinky integrated tube amp at any of these Legacy speakers, but perhaps some small monos with really good transformers, maybe. |
Thanks, deCooney. The capability of the mono 60s was what convinced me to get them over the mid monos (40s) and some other good tube stuff — and so it startled me to think that even by spending that much more, they would still not be capable.
I loved the part of one video where Duddleston says, "We're always having people walking in going well can your speakers be driven with a single ended amp, 16 watts or something, and so it's nice to be able to prove that, so there's a lot of flexibility."
The QS 60s weigh 30 pounds each; big honking amps. Not as big as they get, but certainly not backing me into a corner.
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hilde45,
Its seems folks are just wanting you to be aware some speakers may be better suited to your amps than others, and to try and avoid ones that are not. This past year during a test I listened to some 82db sensitivity electrostatic speakers powered by a quality 10wpc tube amp. It was quite educational and surprising to say the least.
Were they super dynamic and powerful, not really. Were they super punchy and detailed, no. They were extremely musical though, amazingly so. Something you could listen to for days and never get fatigued. So the other consideration is is how you listen, at what levels, and what you enjoy - it varies from one person to the next, and YMMV. |
This whole discussion around impedance only highlights what a can of worms you get with passive crossovers. Here's WHY active crossovers are so very much better than passive. A single loudspeaker driver is an inductor, and provides a frequency dependent, reactive load to an amplifier. Looking at the image here, the blue line on the bottom is the frequency dependent impedance curve for an SB Acoustics SB29RDAC Ring Dome Tweeter, and it typical of any dynamic tweeter. As you can see, it is anything but flat, yet it is listed as having a 4 ohm impedance. It's 4 ohms at about 1200 hz, but at 600 hz, has an impedance of nearly 10 ohms.
Now if you put a passive crossover circuit in front of it, you add capacitors, resistors and inductors, which then give you a frequency dependent impedance curve which looks like a Coney Island roller coaster. And that's just for a tweeter high-pass circuit.
Now when you add in mid and bass drivers, with high and low pass filters there... It's a real mess. But we're not done there yet. Nope. Many of your extreme hi-end loudspeakers add in equalization to their crossover designs, which makes that impedance curve even worse. This is very hard for an amp to properly manage. That's why people drop many, many thousands of dollars on things like Krell, Threshhold, Bryston, or Rowland Research solid state power amps.
Now when you use an active crossover, an amp channel only has to manage a single driver. There's no passive, reactive component in between the amp and the loudspeaker driver. Then you don't need a megabuck amp to deal with it.
All of the Linkwitz loudspeaker designs use active crossovers. Earlier designs used analog crossovers, but his last designs were all digital crossovers. There are some digital crossovers that offer DSP EQ, which allows you to tailor the total system response for the room you are in. Then you're not just limited to whatever sound your speakers give you in the room you're stuck with.
The lowest cost active crossovers are typically pro grade, from manufacturers like Behringer, dbx, Rane or even Nady. There are many manufacturers. Some of the best known home audio digital crossovers are from miniDSP.
Another major benefit is that you can use much, much lower powered amps when you use active crossovers. A lot of power is wasted having to push through a passive crossover. You really don't need to push many watts into a tweeter or mid-range driver to get a lot of level out. You could even run a single ended tube amp on your tweeter, and a mid-level tube power amp on your mid-range driver, and a solid state amp for the bass driver. You have a lot of options.
Of course you've invested in a relatively high powered tube amp, and I'm sure you wouldn't want to use it only as a mid-range or tweeter amp. But in insisting on running a high powered tube amp, you get to deal with the issues a passive crossover brings to you. |
Hi Everyone, great discussion. I'm not sure if what I say applies. I too was worrying about measurements, Speaker and Amp match, but quickly tossed all the measurements aside.
I have Thiel 2.2's that I love but they run at 4ohms with an 86 sensitivity rating. They are fed by a VTL 2.5 Tube Pre-Amp and Mystere PA-21 Tube Amp @ 55 watts per channel connected with all Transparent Cabling and the 55 tube watts driver them effortlessly.
To me my system sounds amazing and to anyone who hears it. The true measurement for me was when i first placed a record on the turntable, my wife came from two rooms over, said that sounds really nice, then proceeded to sit with me to listen to the entire album.
I guess my point is, don't get too hung up on measurements. Trust your ears, and never ever forget to just sit back and enjoy the music.
Enjoy... |
