2. speakers
  3. 1429587251

High value, high efficiency speakers for SET amps

Hi, Gang,
I know that some of what I want to discuss here has been dealt with in other threads, some of them quite old, but I wanted to see if any of you fine, knowledgable folks are willing to help update and consolidate some of this info in a more current thread.
I am currently running my new Audio Note Kit 1 300B SET amp with a pair of Reference 3A De Capo speakers. I think it's a fine pairing and I am really enjoying what the 300B SET experience brings to the table in terms of musicality and emotional connection.
Still the De Capo, while supposedly an easy load due to its crossover-less design (only 1 cap on the tweeter with the mid-woofer directly coupled to the amp), is "only" rated at 92 db efficient, and based on the most recent Canadian NRC specs, that rating may be optimistic.
So, I am toying with the idea of trying a pair of more efficient, deliberately SET-friendly speakers in my rig, something that might also play lower and with greater dynamic swing than the De Capo's. Note that the De Capo's have served me well and I am very fond of them, but I can't help but wonder if my lovely Kit 1 would shine even better coupled to a VERY easy to drive speaker.
Devore and Audio Note are obvious options - the O/96 looks really tasty. Unfortunately, both of those choices are out of my budget, which I'm thinking maxes out (for real) at around $1500. I am willing to consider used equipment.
Tekton Lore 2.0: This is the speaker that Eric Alexander of Tekton has recommended when we've spoken on the phone, based upon my medium-small listening room and amp. I've read the epic "Lore vs. Zu" thread elsewhere in this forum, and clearly Tekton has its enthusiastic fans here. What I wonder is whether the Lore 2.0 has the refinement of the De Capo in terms of resolution, sweet high end and imaging. Audiogon'er Mikirob has pointed me to the many rave reviews of Tekton's speakers and I'm definitely interested.
I've corresponded with the Sonist folks (who are super nice) but their really high-efficiency, nearly-full-range floor stander is out of my budget.
Then there's the "vintage" route, going after some used JBL's or other high-efficiency "classics" from the 80's (or '70's). I am not inclined to go in this direction, but mention it because it's been suggested to me.
And then there's Omega. I spoke to Louis some time ago and he recommended his 7XRS hemp cone model. But I know all the raps on single driver designs and I'm cautious, although I would like to hear from any of you who own or have owned Omega's.
I'm in no rush to make a switch but I am very interested in your thoughts. Thanks, folks!
rebbi

Showing 8 responses by atmasphere

atmasphere's avatar
atmasphere
12,008 posts
 
The Classic Audio Loudspeakers have efficiencies that are what you want for a 300b SET (which only makes about 7 watts). The best suited in their line is the Hartsfield reproduction.

Sorry to pop some bubbles here:

The problem you are up against is that with almost any SET, if you really want to hear what the amp really does (the magic) you really **don't** want to push it past about 20% of its full output. If you do, the higher ordered harmonics come into play and there is an interesting interaction that occurs with the human physiology when that happens!

(The interaction is that the higher ordered harmonics will be showing up on transients, and the ear/brain system will interpret that as loudness. As you increase the volume, the loudness cues are thus initially only occurring on transients. Thus the amp will *seem* to be much more dynamic than it has any business being for its output power! This is a common comment about SETs- and one that indicates that the amp is not set up properly. The speaker used needs to be more efficient to avoid this problem. BTW, now that you have read this I may have ruined it for you: knowing that the dynamic quality is really caused by distortion makes it easier to hear the distortion itself.)

(A further note: about 90% of the time when audiophiles are talking about 'dynamics' they are really talking about distortion. The word is so heavily charged that if I really do mean dynamics I often use other words such as 'impact'.)

So with only 2 watts or so to really play with your speaker must be over 102 db or so- otherwise you simply are not hearing what the amp can really do. SETs have the property of distortion that becomes unmeasurable as power is decreased; this is the source of their 'inner detail magic'.

The bottom line is if you have a 300b SET, unless your room is very small you will need a horn system of some sort; single driver speakers like the Zu or Lowther simply lack the efficiency in an average room.
atmasphere's avatar
atmasphere
12,008 posts
 
4)I note that John Atkinson states in his measurements of the older de Capo i version of the speaker that "the speaker's low-frequency tuning is actually a little on the overdamped side." If the same holds true of Rebbi's BE version, its sonics could presumably benefit from the low damping factor of a SET.

This would make it a good choice for an OTL as well, and no worries about power or bandwidth.
atmasphere's avatar
atmasphere
12,008 posts
 
Generally with SETs if you really want to hear what the amp does (where the 'magic' is) its important that you don't push it past about 20-25% of full power.

For this reason you usually need a really efficient speaker to show the amp off. In the case of a 300b-based amplifier, this means you need to get good sound pressures with only about 2 watts. This requires a high efficiency loudspeaker. FWIW, Coincident does not make a speaker with the efficiency required, especially in a larger room.

This is not to say that such a combo will not make sound- it will- but it will not show off either the capabilities of the amp nor those of the speaker. You simply need more power than a single 300b (or even a pair) can provide.
atmasphere's avatar
atmasphere
12,008 posts
 
Atmasphere,
Rebbi's room is about 11x12, my office system, 14x16. Believe me, even true 92db, 8ohm, no problem. My 8 watt Coincident Dynamo is sublime with my 95db or 98db Lores depending on model. How loud do you listen? I generally like about 80db, sometime louder, never a problem. I could't listen much louder in a sustained way without ruining my ears. I really loved the Gizmo and OTL, but even he eventually went The Big Tannoy with 300B. Best Rob

The big Tannoys seem a better match for SETs. They also work well with our amps. FWIW, Harvey tampered with our amps when he had them at his place, and not in a good way.

Just so you know, SET listeners tend to play at lower levels due to the distortion aspects of the amp. Once you get over about 25% of the output power, the higher ordered harmonics come into play. The ear uses these as loudness cues, which is to say that when these distortions show up, the amp sounds like it is playing louder than it really is. So you tend to say "that's loud enough!".

I like to play the system at louder levels, but the amps that I use don't make the higher ordered harmonics until very near full power, so the system is absent of artificial loudness cues. IOW, at 95 db it does not sound loud at all.

My speakers are 98 db, my room is 17' x 22' and fairly well damped.

Audiokinesis makes speakers that are more efficient than the Coincidents, and often they are 16 ohms. If I am not mistaken they are less expensive as well. So they might be good to have on the radar as well.
atmasphere's avatar
atmasphere
12,008 posts
 
This is very interesting, Atmasphere. Is this true for SEP as well? True for a Dynamo 34SE?
That was an insightful observation.
Thank you!

The 20% thing applies to SETs, which typically make about 10% THD at full power. However below about 20% their distortion is quite low, and if one thinks an SET measure poorly one should try to measure the distortion at the lower power levels and then they don't look bad at all. Its understanding how they are to be used that is in short supply.

SEPs are a little different- and because of their inherently higher distortion I would expect that you would want to run them at even less power.

Again, speaker efficiency is key: otherwise you simply are not hearing what the amplifier can do.
atmasphere's avatar
atmasphere
12,008 posts
 
The is no single type of amplifier that is the best for all genres of music, I don't care what amplifier it is, there's inevitable compromise somewhere.

Charlesdad, while I appreciate many of your posts and your primary tenant (paraphrasing: 'get the system that sounds right to you and enjoy it'), the above quote is simply incorrect. Electronics don't care what signal you give them and can't express taste. If the amp is excellent for classical it will be excellent for rock, because it is excellent.

I trust Ralph of Atmasphere when he states that distortion rises quickly with these amps before they reach peak power, but I can tell you that that is not the case with my speakers. I, like Charles, choose to listen at moderate levels, but when I am off and around the house in different rooms, I will turn it up to levels that are pretty loud by any standard, and it still sounds great, without a sign of strain.

102 db is the kind of efficiency that is needed to work with many SETs. I suspect though that the Klipsch are really 99 db (which is still helpful) due to the difference between efficiency and sensitivity; unless I am mistaken I would expect that they are 4 ohms in the bass region despite the '8 ohm nominal' impedance claim.

'Strain' BTW has nothing to do with what I was talking about in my prior posts. If you have ever wondered why SETs are so dynamic, especially considering their low power, the reason has to do with how they make distortion without clipping. As you get over 20-25% of full power, the higher ordered harmonics start to show up. Its important to understand that the ear uses these harmonics as loudness cues, so their presence will make reproduced sound seem louder than it really is. At the volume is increased, these harmonics show up on transients (where the power is) so essentially the loudness cues that the ear detects will be more prominent on the musical peaks. This gives the amp a very 'dynamic' quality.

However what is really happening is more distortion is present for brief periods. Actually in about 95% of audiophile conversations, the word 'dynamic' or dynamics' can be safely substituted for the word 'distortion' without altering the meaning of the conversation at all.

I may have ruined it for some as the awareness that distortion is driving this phenomena may mean that you become more aware of it.
atmasphere's avatar
atmasphere
12,008 posts
 
So, Atmasphere,
Then why don't we have manufacting that promotes high efficiency nominal 8 ohm or higher speakers. Seems like it makes amp manufacting funnel into a narrow "limiting" high power proposition that does Limit and force a specific choice that doesn't often times serve music by my definition, but does loud/dynamic. As a maker of a fine amp, don't you realize many benefits with more efficient speakers in the manufacturing process.

I'm a big advocate of high efficiency- tube power is expensive! My speakers at home are 98 db and 60 watts is pretty good power on them and I don't feel like the extra power is wasted at all. I like to play things at a lifelike level. I'm also an advocate of higher impedance- 8 ohms or more. This reduces the distortion of all amplifiers, tube, solid state, class D, whatever. Higher impedance is also a lot less critical of speaker cables and connections! IOW if high quality reproduction is your goal, there really is no good reason to use a 4 ohm speaker. If sound pressure is your goal and you have solid state then there is a reason, albeit a 3 db reason... it would be cool if speaker manufacturers figured this out as a simple way to make any speaker sound smoother and more detailed is to reduce the distortion of the amp by increasing the impedance of the speaker.

Ralph I stand by my statement that there is no perfect amplifier, some will excel in some sonic areas and be less than ideal in another. We choose the tradeoffs we can live with.

Restated in this fashion I've got no beef; I agree 100%.

One of the huge strengths of SETs that many audiophiles don't realize is that 'first watt'. SETs might make a lot of distortion at full power, but as the power output is reduced the distortion decreases linearly to unmeasurable- at lower power levels most push-pull amps make a lot more distortion (one of the few exceptions being our OTLs which have the same reduction of distortion as power is reduced). This is where that great 'inner detail' and 'magic' comes from- without distortion you just get the music (distortion masks low level detail via the ear's masking principle).

That's a lot harder to do than it sounds!

This is why if you really want to hear what the amp does you need a speaker with real efficiency.
atmasphere's avatar
atmasphere
12,008 posts
 
A few comments.
I also listen at lower than typical volumes. I frequently have to fight with salon proprietors to turn it down when I audition new equipment. In my case, those lower volumes represent realistic volumes. Bach cantatas are seldom performed at 105 dB. So, Ralph, no worries! You did not confuse me by presenting the facts as dictated by physics and math.

My problem is that I played in several orchestras over the years and my wife was a singer. I've seen her singing in a Bach Cantata and FWIW 105 db is **easy** when the full choir is singing at a double forte (ff)! Having such exposure to the real thing (which is on-going; I operate a recording studio and play in a band), playing with peaks at only 75-80 db is good for background music when I am reading or cleaning up the kitchen but not if I am seriously listening. What if you want to play Wagner (Das Reingold, Decca, Sir George Solti conducting, side 6) or Verdi (Verdi Requiem, RCA Soria series, side one cut 2)?? 80 or 85 db peaks ain't gonna cut it- you need the unrestricted ability to play well past 100db without incurring artificial loudness cues (previously mentioned in prior posts) from the system.

With a low powered amp this means high efficiency and make no mistake. If you have 91 db, the is a moderate efficiency and although you may like what you hear, just keep in mind that you are not really hearing what the amp is about and for that matter the speaker as well and it just goes to show. Seems a poor investment to me, unless you are in a fairly small room or office.

But that's me- I figure if you are going through the trouble and the cash, might as well be able to really enjoy the music the way it was recorded. Others might differ on that...
More to discover