George and Ralph, not really interesting in starting another discussion on the differences between Voltage Paradigm amps (generally solid state amps with very low output impedances -- high power SS amps can generate high current) and Power Paradigm amps (usually tube amps with higher output impedances).
Suffice to say that as Ralph and Al (Almarg) have said many times, if a speaker was designed and voiced to be driven by a Voltage Paradigm/SS amp, using a high output impedance Power Paradigm/tube amp will likely result in acoustic colorations. The reverse case also being true.
But hey, not all acoustic colorations necessarily sound bad. ;-) |
Thanks George, I read the article that uses the term EPDR. It appears to be a numerical factor that in some way combines and restates a speaker's impedance and phase angle attributes at a specific frequency as some sort of "impedance prime" equivalent.
Is there a formula that would enable one to make an EPDR calculation? What about cases involving inductive phase angles? How is EPDR computed in such cases? Are they hard on amps (tube or SS) like capacitive phase angles? Lastly, how significant is a low EPDR at a particular frequency when the frequency range where the EPDR is low may only be 10 or 20 Hz wide?? |
Thanks George. Is it a gross simplification to view EPDR as a "refined" version of impedance which will provide a clue about the load an amp is facing when driving a speaker at various frequencies?? For example, the EPDR of the Wilson Alexis at one point was .9 ohms, which I assume is not particularly amp friendly.
Also, as a practical matter, most impedance and phase angle curves vary significantly as a function of frequency. So what's the deal if a speaker's EPDR in the bass region is .9 ohms (ala the Alexis), but the bandwidth saddle is only say, ... 50 Hz?
Thanks again George.
Bruce |
Thanks for the heads-up George. I'll do some checking. At this point, more from dumb luck, I may have a combo that works ok because my ARC Ref 150 has muscle power and a large reserve power supply, plus my speakers are reasonably sensitive (92 db). Otherwise, I would have been another hapless victim. I'll be smarter next time when I upgrade speakers. That's for sure. |
Ralph, maybe my aim is way off. Instead of picking on amp manufacturers, maybe it's the speaker manufacturers who should be taken out to the woodshed.
But first, let me be generous by at least asking if it's the nature of the beast and the laws of physics that is the reason conventional cone speakers have flaky impedance and phase angle curves? Stated differently, is it possible to design a cone speaker that performs well *AND* has benign impedance and phase angle curves? And is also reasonably sensitive??
I imagine the "SET-heads" must use such speakers or else SET amps just wouldn't do the job.
Bruce |
Ralph, what you say makes a lot of sense. Notably, take a look at some of the Class A speakers profiled on Stereophile's 2013 List of Recommended Components, here:
http://www.stereophile.com/content/2013-recommended-components-loudspeakers
Most if not all the selected speakers (including B&W 800-Ds)seem to have the type of impedance characteristics you referred to above.
Based on discussions with Paradigm, I'm pretty sure my speakers were also voiced to be driven by a high current SS amp. FWIW, I understand that my version of the Signature 8 (v3) was redesigned whereby the woofers are now 3 db more sensitive. As a result, the mid and tweeter drivers were "unpadded" to be driven full bore. So, the current v3 version has a rated sensitivity of 92 db verses the v2 version, which was 89 db.
I gather that 3 db is a considerable increase in sensitivity. As such, based on what you said above, the S8 v3s are an easier load, regardless of whatever type amp is being used.
Nevertheless, I also gather than even though any type of amp should be less stressed driving the S8s, one is still left with the issue of acoustic coloration, the amount of which is dependent, in large part, on the amp's output impedance. Ergo, the caveat that some tube amps might not be a good candidate, particularly those not using any or very little NF. The same point also being relevant to many other speakers as well, which if technically correct, is an important take-a-way point.
Thanks again Ralph. |
George, I happen to enjoy reading many of your posts in other threads. But I feel compelled to politely suggest that Ralph Karsten (Atmasphere) and Al (Almarg) are among the most respected A'gon members. Both are EE techies. And Ralph is the gent behind Atmasphere as in the "designer" and maybe the owner too.
In short, you're taking on some pretty heavy-duty guys. I suggest you back down and carefully re-read what Ralph and Al posted. I happened to think that what they wrote makes sense.
Ralph and Al, the discussion begs the question of how can one know whether an ESL was voiced to be driven by a tube versus SS amp. Obviously Sound Lab ESLs were designed to be tube friendly, ergo Ralph's comment that his amps have been coupled with Sound Lab ESLs for years. Is it the same old answer -- call the manufacturer and ask?? Or try to determine the type of amp that was used by the manufacturer to display the ESLs at shows??
Seems to me that what gets a bit dicey is the case where the ESL is coupled with a cone/dynamic speaker to cover LFs. Then we're back in the soup with "rock and roll" impedance curves.
Folks, let's try to remember this is a just a cool hobby and we're all friends.
Cheers,
Bruce |
I am standing down. I read all the posts and respect the good intensions and credibility of all the folks who contributed to this OP.
My sense of the issue is purely academic. I'm still trying to get my arms around "simple" electrical compatibility concepts involving amps and conventional/cone speakers. Electrostats seem like a horse of a very differnt color.
I will say this. Any interest I had in trying ESLs is gone. It seems that amp/ESL compatibility is counter-intuitive. So I'll stick with what I have.
Btw, to the point about going with one's ears. I've been switching between my amp's 4 and 8 ohm output taps. For various technical reasons that I am not going to get into, I would have surmised that the 4 ohm taps would have been the preferred taps. But it just isn't always the case. At least that's what my ears tell me. So much for any notion of "faithful sound reproduction."
Well Stanely, "... that's another fine case" where changing speakers may be an exercise in futility.
Cheers and Happy Holidays.
Bruce |
Thanks Al.... Headphones is where my wife wants me to go. When my wife begs me to lower the gain, and then violates the serene sanctity of my blessed man-cave when she does so, I promise to turn the rig down, but turn it back up even higher when she leaves. LOL :)
Clearly Al, you are much more the gentleman than me because you switch over to headphones so as not to "conflict with [your] wife's activities." AL, ... I'm 19-year old child trapped in a 60-year old body -- just like a rat trapped in a steel cage.
I get the idea that negative phase angles coupled with low impedance attributes in a speaker's bass frequencies makes for a difficult to drive load. But good ole' George dropped a new term on us tech newbies, "EPDR (equivalent peak dissipation resistance)." Que'est ce se mon amies??? [What does it mean my friends?]
All the best guys. And ok, I'll put ESLs back on the speaker possibility list.
Regards,
Bruce
|
George, I did a web search for an article that explains EPDR. I found an article authored by Keith Howard printed in Stereophile (July 2007), here:
http://www.stereophile.com/reference/707heavy/index.html
Mr. Howard explains in simple to understand concepts what I have been seeking for some time. Namely an article that folds impedance and phase angle stats together in a way that provides useful information about speaker and amp compatibility.
If Messrs. Howard or Atkinson, or you too George, get around to starting up the SPCA (Society for the Prevention of Cruelty to Amplifiers), send me an application form.
And as usual, we audio dummies are at the mercy of an industry that is not as transparent as it should be. To quote Mr. Howard, "[EPDR] import seems not to have suffused audiophile consciousness. Speaker reviews don't address this issue, and neither do many speaker manufacturers, who are apparently happy to throw the output-device dissipation problem over the fence for amplifier designers to deal with."
Speaking just for myself, I'm embarrassed to call myself an audiophile for not having better quantifiably grasped these concepts a long time ago. What I wound up slapping together is hard to call a system. More the result of sheer dumb luck.
Good night Gracie,
Bruce |
