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In Reply to: RE: How much power do you need? posted by PaulF70 on September 09, 2016 at 17:25:09
I have long been a proponent of using lower power amps and SET in particular whenever possible.
more than 10 years ago I was using a 30 watt KR Audio VA350i on a pair of Acoustat Spectra 2200s that had a sensitivity rating of 84db. It worked beautifully up to the upper 90s db range, which as you rightly mentioned in a room is LOUD.
I have also seen demonstrations where the speakers were not getting so loud but were sucking hundreds of watts from the speakers as visible on their front panel power meters. The speakers in question had a similar sensitivity rating to the electrostats (perhaps a db or two more even).
My current horn speakers (Odeon La Boheme) will rock the house with 20 watts and probably a lot less (my SETs are all 20+ watts so I don't know about significantly less than this). THey are around 98db/watt and I sit around 3 meters (10 feet) away from them. My small Odeons (Rigoletto) will play quite loud with the same 20 watt amp in a bigger room despite having a sensitivity of "only" 93db/watt. Both speakers, even going full tilt have nearly zero driver movement as the bass driver of each (both are two-ways) is back horn loaded and the tweeters are horn loaded as well.
So, what gives here? I think power compression and crossover losses are the main culprits for a majority of "normal" box speakers.
This box speaker that was still playing at tolerable levels even though the meters were reading hundreds (like 500+) watts seems to strongly indicate that the speakers were not increasing in loudness by 3db with every doubling of the power. Probably at some point they simply were not getting any louder and the energy is wasted as heat.
Why my electrostatic speaker probably worked ok with 30 watts was a few reasons: 1) They do not suffer power compression as there is no voice coil to heat up, 2) They were line sources and as such the SPL drops more slowly with distance than a point source 3) THe room was not huge so there is likely significant room gain. I actually measured the drop from the front of a panel to my listnening spot (just over 3 meters) and it was only about 1db. With two panels you get then about 87db for 1 watt, 90 for 2, 93 for 4, 96 for 8, 99 for 16 and 102 for 32. I measured peaks with my Behringer DEQ2496 and calibrated mic in the high 90s without any audible distortion (I didn't have a scope hooked up, alas).
As speaker with significant power compression might be fine for the first few watts but then as the demand to go louder it will compress. This is happening both on steady state and to some degree on sudden peaks as well when the current goes surging through that voice coil it will heat up very fast. A complex crossover will exaccerbate the losses before getting to the voice coils.
I experienced this first hand in the past with Dynaudio speakers. I had a pair of Dynaudio Contour 1.8MkII speakers with about 85db/watt sensitivity. They would not play soft well at all, sounding lifeless and gray. Turn the wick up a bit and they would sound quite good...for compressed pop/rock music and some jazz but not classical at all...the soft stuff just got lost. Turn the wick up some more though and the speakers started to sound compressed with dynamic peaks lacking dynamic punch...the soft stuff would work better but crescendos became a compressed congealed mess. This was the same with several amps I tried...from 500 watt beasts to 35 watt EL34 tube amps.
This speaker has a "comfort" zone of around 80-90db where it sounded quite good and this meant it was tailored to pop music and some Jazz. Rock music played really loud didn't work that great either. Classical was hopeless. Switching to electrostats (AudioStatic ES100s) fixed the low level resolution issues I had and allowed unrestricted dynamics up to the physical limits of the speaker, despite having about the same nominal sensitiity. Jazz and classical became a joy to listen to for a change.
For me, the speakers that "need" 500+ watts are the ones to avoid because they are actually not really delivering the sensitivity they claim beyond 1 watt where they were tested. The normal math (3db for every doubling of power) shows you can get quite loud with a handful of watts but this is only true IF the speaker is really getting 3db louder with each doubling...I suspect most are compressing badly and don't get close to this.
Follow Ups:
What kind of SET's are you running that they are all 20+ watts? They is a lot of ommmph for an SET amp. What output tubes do they use?
Edits: 09/16/16
I have the following:
JJ 322, which is a parallel 300B amp. Rated 20 watts makes a legit 15 watts at 1% THD based on measurements from a Polish mag.
Wall Audio Opus M50 monos. Parallel 6C33CB makes a rated 35 watts but who knows at what distortion. These sound significantly more muscular than the JJ though.
Aries Cerat Diana integrated. All DHT design with 813 output tube wired in triode (it is actually a DHP (direct heated pentode). This amp is rated at 25 watts and probably gets close to that with reasonable THD. I have this in house for review right now.
Soon, I will have the Ayon Crossfire III and in October I will have a pair of Ayon Vulcan II monos for review.
You need to try a true single tube triode SET like a clssic 300B or 2A3 or 45. I think you will hear quite a difference.
I will be getting an Ayon Crossfire III soon. I can let you know how that worked out. FWIW, I have also had the KR VA350i on the speaker and the Aries Cerat Diana both of which use a single output tube. Both are a bit more pure sounding but both cost more than my JJ or my Walls.
FWIW, I run the same speakers as morricab on a set of 2A3 DHSET monos that probably do about 3-1/2 WPCH or so, and I'm quite happy with the sound. It's enough power for my purposes, but I do think it worth noting that the manufacturer recommends ~10 WPCH, and I admit that it could stand a little more slam/grunt, or however you wish to describe it. It's also worth noting, however, that I haven't yet tried any tubes other than the Sovteks that came with them. A set of JJ 2A3-40s might well address that issue.
Those JJ239s look quite nice and I almost bought a set more than once. However, I never did because I have a feeling that they sound a lot like the JJ322. Could be wrong though as the driver is different, the output tube is different (although it looks to me like the JJ 2A3 is simply their 300B with a lower filament voltage) and there seems to be a bit of negative feedback. However, the power supply design and, importantly, the output transformers are very similar (i.e. Double C cores with thin laminations).
BTW, I got the Ayon Crossfire III and it is VERY transparent and has real balls as well. Nearly as ballsy as my Walls + NAT combo but more transparent it seems. Really good impression so far. I am not sure about the 30 watt rated power as it is probably more like a 20 watt amp but that is plenty and then some for the La Bohemes.
I can't imagine needing even 20 WPCH with these speakers, but then my listening room isn't that large.
The Ayon appears to be quite an amp. It should be with that kind of a price tag, FWIW. It would be nice to try something like that out...
If you can't imagine using big amps on efficient speakers, just think of a car with 600 horsepower. It just does not jump off the road with you in it, YOU control the power with the throttle. And even if you don't ever put it wide open, it is so much more responsive to the throttle, so satisfying, you just feel that effortless powerplant in normal acceleration.
Same with the big SET: at 85db you can feel the effortlessness, the ease, the size, the control, the palpability. I've heard fantastic 1 watt amps, but they don't have the effortlessness, the size, the scale, as equally fantastic 20 watters. And fantastic 20 watters don't have the same ease equally good 100 watters. My speakers sound like they go an octave lower and are just more musically convincing with the big amps, even at the same 85db volume, with 102db/watt speakers.
Overkill often helps.
Let me make an important point about my lower powered SETs:
I am not denigrating the wonderful SET sound that is available at lower power. In fact, on of my 20 watt SET amps won my heart over a much more powerful push pull amp, which was the best push pull amp I ever had. So, it all becomes relative. I would take that 20 watt SET over any non SET I ever had in 40 years, into my 101+ db speakers. That's a pretty strong statement. I just prefer the higher powered transmitter tube units....which are expensive, and could blow at any time....who knows.....
And it's the expensive part that's the problem. I'm already playing way out of my league by having bought the Odeons to begin with, then getting the Ultra-Fi monos. The sound I have is very good. Could it be better with a more powerful SET? More'n likely, but it doesn't really matter at this point. I'm going to have to live with what I have, which is pretty damn good, as far as I can tell. I'll leave the perfection part to people with a helluva lot more disposable income than I have ;-)
What a mature post, the one above this. Yes, agreed, when you love your sound, when nothing is annoying you, when you are not wishing for anything, why muck around? Just listening and enjoying is the goal that most people never get to, and that's something about which I complain about the high industry. It becomes about the gear, not music.
Todd, you are wise enough to realize when you have it made. Congratulations on your choices, and congratulation on being able to recognize that.
Enjoy your music!
Don't be spreading that wisdom stuff around - very bad for my image. ;-)
Make no mistake; my system has its warts. There's a bass feedback issue that only shows up on certain music, and always has me diving for the volume control. Oddly, Alan Parsons "Turn of a Friendly Card" was fine at a fairly high volume level; good solid satisfying bass that really set a foundation for the music, but Angele Dubeau's Ludovico Einaudi sets up a feedback loop that sounds almost like TT wow, and there isn't significant low frequency in the recording, so go figure.
I'll get it squared away eventually. I expect that it probably take a set of wall mounted shelves for the 2A3 monos. Keeps me off the streets.
Is this with your sub engaged? Btw, the Crossfire has totally eliminated any need or desire to run a sub with the La Bohemes. It goes deeper and with awesome control unlike any other SET I have tried on them...even KR, which set the bass standard for SET with me until now. Tonally, the KR might still have the edge but until I try direct comparison I can't be sure.
Never mind. After I went back and re-read the above posts I was able to find a couple of links. The Crossfire is way out of any range I'll ever be able to afford, but it's nice to know such products exist, since the technology does tend to trickle down. If only economics really worked the same way. ;-)
Hey, Brad. Sorry it took so long to respond. I've been out of town with no internet. Not a bad thing sometimes.
Yeah, the subs are engaged. One of the subs is now out from under the bridge table (which did help), but I have nowhere else to put the other one. Until I get to making some wall-mounted shelves for the amps, I may just run both leads into the one sub and take the other out of the system, since I'm sure it's the one under the bridge table that's causing the issues. I'm running the crossover points as low as I can set them, so directionality shouldn't be an issue.
Got a link for that Crossfire amp? What I'm finding on a search is guitar amps. Not that it matters, since there's not likely to be any changes made here for a long time, but I'd like to know what we're talking about.
Well, I sometimes was putting my sub in and out of the chain depending on the kind of music. For more bass heavy music I found most amps to sound a bit lightweight on the La Bohemes, which is why the sub from time to time.
Now though with the Crossfire, bass is more than ample and has real weight! It really surprised me...especially with recordings like Yello "Touch" there was seemingly an extra octave that my other amps didn't deliver. Also, it has awesome bass texture and dynamic snap...it is very tight sounding. Tonally, it is lighter overall though than the Wall Opus M50s/NAT Plasma combo. This has good enough bass as well that I was not needing the subs and is richer overall in tone but doesn't have the same inner resolution and soundstage/imaging stabilty of the Crossfire.
So far, I think this is a pretty awesome amp.
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