Highly Sensitive Speakers?

I suppose it’s only to be expected. Still, its a bit disconcerting. Another system? Already?

I mean, WTF, seriously? The last bits of my current system aren’t even in and yet, here I am, actively hoovering the Internets for info about another approach to high end audio: high sensitivity speakers. Egads.

My current system, built around a Plinius amp and pre, driving Magnepan speakers, is absolutely incredible. Best I’ve heard here at Chez Moi — and by a country mile. My new Berkeley Audio Series 2 Alpha DAC with it’s attendant Alpha USB is, likewise, the best digital front end I’ve ever heard here — and may well be the best I’ve ever heard anywhere. With that said, I fully expect that my digital front end will be utterly destroyed by the analog rig that is supposed to be showing up this week from Deutschland.

So, what gives?

Nothing, really. I really love that system. Love love love it, in fact. But you know what would be fun? A highly sensitive speaker with a low-output SET amp to drive them.

I know! I know. Believe me, I know — I have problems.

My Magnepan 3.7, love them though I do, can hardly be called anything other than low-sensitivity. I think Magnepan rates them at 86dB (@ 1w/m), but this might be a stretch. All I know is that no one runs these speakers without a giant amplifier — and I don’t either. My Plinius SA-Reference cranks out 450wpc into 4ohms, and the speakers pack a hefty whomp! because of it. But is that all there is, power?

Tackling that question requires a sidebar.

Now, everyone knows that to get another 3dB out of your speakers requires a doubling of power going in. To go from 86dB @ 1w, if we added a watt — using a 2w amp instead of a 1w amp — we’d have a max volume of 89dB (at one meter). Adding 3dB requires another doubling — so, now we need a 4w amp. 8w gets us another 3dB for a total of an extra 9dB over the baseline, or 95dB of speaker output. Keep doubling, and we’ll quickly get to 512w, which nets us a total of 27dB over baseline. 512w is a bit more than my Plinius amp can do (without clipping), but it’s close enough — so, say we shave 1dB off that number and call it even 26dB. With that extra 26dB that amplification provides, my Maggies can swing about 112dB of total output, max.

Is that good? Well, as the Bob Katz discussion tells us, we need no more than 20dB of headroom above (and below) a given average listening volume in order to allow for the full dynamic swings we might possibly find in our recorded music. So, assuming that the max average volume I play my music at is 92dB, I’m good to go. And luckily, 92dB is on the loud side of my comfortable listening window.

Of course, this isn’t to say that my speakers can’t play loud. They most certainly can — but the louder I turn them up, the less headroom I have available. As long as the music is compressed, the amps and speakers won’t clip, and as Bob tells us, most music is heavily compressed, so I think a good rule of thumb would be to shoot for at least 12dB of headroom in your system. That should make you right with the vast majority of music out there today.

But when it comes to headroom, the more the merrier. The more headroom, the more the speaker/amp combo can operate in their comfort zones, which ought to result in better quality sound. Interestingly, if you have a speaker that actually starts a bit higher on the sensitivity scale than my Maggies (which isn’t hard), you can get gobs and gobs of headroom pretty quick and pretty much painlessly.

Looking at a horn speaker like a Nano from Avant Garde, we’re looking at 110dB of efficiency right off the bat. Add a 2 watt amp and you have the same output as my Maggie+Plinius setup — going all out! Add an 8wpc amplifier to that horn and you have system that can push nearly 120dB. Yikes! Anyway, that’s dynamic headroom. The more of it, the better.

The last bit here is a tube-thing. Now, I’m not really a fan of tubes for the obvious reason — they’re either breaking in or breaking down. Owning a piece of tube audiophile gear is a commitment — and that’s before you go hog wild with swapping out (“rolling”) the tubes for ones that sound (usually, only slightly) different. And, of course, you need back up tubes. And with many tube amps, you will need to manually bias the circuit yourself, which means delays during warm up, continually fiddling with adjustments … and then there’s the whole voltmeter thing. Audiophile … turned electrician? It’s all kind of annoying and quite frankly gets in the way of the music. That’s why I hate tubes and after a harrowing experience with Joule-Electra OTL amps, have completely banished them from my big rig.


But there’s just something about the sound that you get with tubes that’s really and truly different than what you get without them. It’s not better — and in most measurable ways, quite the opposite. But as my experience having both the tubed Lampizator DAC and the non-tubed Playback Designs MPS-5 here taught me quite painfully is that sometimes great specs and measurements and control … well, it just isn’t all that fun to listen to.

So, where does that leave me? Well, color me curious about a more “fun” system. With a highly sensitive speaker, I can get away with getting a flea-powered amp to drive them. Why a flea-powered amp? Well, why the hell not? Honestly, there’s something about a single-ended triode system that I find magnetic. Perhaps it’s the insane immediacy of the mid range. Perhaps it’s those crystalline highs. I’m pretty sure it’s not the lumpy, bloated or slow bass, but then I guess you can’t have everything. I kinda want a 45-based amp. Or a 2a3. Or even a 300b. Heh. Ahem.

But to be able to get away with an amp less than 16wpc, I will absolutely need to make that extra volume up with the speaker. So, I’ll be looking at something with a sensitivity rating of around 100dB — much less, and I think I’ll be starving the speakers or continuously punishing the amp. Not that an 3.5 wpc amp can’t drive a 88dB speaker (I have a Miniwatt N3 feeding some 88dB Audioengine P4 speakers here on my desk, after all) — the speakers just won’t sound as good as a 60wpc amp will (bass will be weak, highs may seem blunted — and there’s just no cranking the sound to 11).

The question I’m wrestling with is “how low do I go?”.

In the wide-bander (single-driver) category, I’ll admit that I’ve never been a huge fan of Fostex-based speakers or of Lowther-based designs. Now, don’t get uppity there, settle down! — yes, both of those august drivers can be made to sound excellent, sure. It’s just that those are rare [ducking]. A slightly different approach would be to use an Eminence driver (or some other, similar, widebander). Going that route, I can get a 98dB Tekton Lore for about $1000 new. Similarly, Zu Audio makes a the 101dB Soul Superfly, for $3k that has gotten some very public raves. The Superfly is a 16ohm speaker, though, so finding a good SET integrated to drive it might be a bit of a challenge as most (‘most’, when qualified with ‘affordable’) seem to only come with 4 and/or 8-ohm taps. No, this mismatch is not fatal, it’s just not perfect. Doubling the speaker impedance (going from 4 to 8, or from 8 to 16) halves the power delivery of the amps attached — never a good idea — and this might rule out some of the more entertaining low-power triodes.

Another approach would be something like an integrated bass boost. Vaughn Loudspeakers makes a series of speakers with reasonably high sensitivities (93-99dB) and adds just that, a powered bass subsystem, which helpfully eliminates many of the objections that people have with SETs (that is, it has weak bass). They’re priced from $6500 to $9k.

And (yes,) there are a ton of other options besides. Ocellia, Tonian, and a host of others have offerings that can and do fall in the intersection of “reasonably priced” and “high sensitivity”. There’s too many to choose from, actually, though, affordably-priced horn speakers are difficult to find or just wildly colored (“cupped-hands”, “horn-honk”, &c), which rules out the favorite recommendation of the Internets, a classic Klipsch. Volti might work, but they’re not cheap and ….

Sheesh. This is hard.

More soon.