Image Density, High Efficiency, Flea Power, Room Acoustics

I want to discuss how one could achieve solid, dense images with high efficiency speaker + low power amp combo.

One of the biggest benefits of a high efficiency system is, it opens up the option to use flea watt DHT amps. Based on my limited data points, it seems like, when you try to drive these high efficient speakers with flea watt amps, the lack of good room acoustics start to kill the image density. But like I said, my data points are limited and I would like to hear your thoughts.

 

There was an article in Stereophile a decade or three ago all about high-efficiency speakers with low-power amps. I'm sorry, I don't have a link.

I knew a guy on another forum who really took it to heart, proclaiming that the principle couldn't be beat.

I have no clue, either way --- but I do know that (not sure if it was him or another member of the group) a system that I heard, built with salvaged Cinema speakers, and powered by old Quad amps was absolutely gorgeous.

 

I don't claim to be any kind of expert either on the intricacies of DHT amps or horn loaded/BWC or otherwise high sensitivity/high efficiency speaker designs. But I do feel there is something to doing as little as possible to the music signal from media to wiggly air, and the combination of low power/hi efficiency seems to do much less to confuse the issue of signal integrity through over-engineering.

 

Audio Note UK is basically built on this principle. 93-98 dB sensitive speakers and the further up the line you go with their amplifiers, the less power they generally have. Most criticisms of AN systems (aside from price) are that they don't tick enough audiophile boxes -- bass isn't tight enough, imaging not pinpoint enough, etc. But I've never seen anyone complain about image density.

 

@EagleWings can you say a few words clarifying what you mean by “image density”? I don’t remember seeing anyone use this term before. Do you mean the solidity of the image? Or the amount of spatial information? Or something else?

 

Is an uber-high efficiency transducer paired with a uber-low-powered amp similarly desirable in a headphone system?

 

I seem to recall Decware being built heavily around this as well. Really, any forum dedicated to tube gear tends to lean this way.

Lots of people espouse the low power high efficiency thing. I get it. Partly it's historic, back when you simply didn't have that much power available to create sound. There's a lot of "the first watt is the most important" philosophy that floats around, heck one of the bigger name dudes named his company after it. If you consider power/energy as this nebulous quantity of thing that must move, then our gut feeling tells us moving less will be better or "cleaner" than moving a lot of something. It's like the water analogy for electricity, lots of power must mean lots of water which is harder to move cleanly, so thus less water is better right?

As with all things, moderation is required. Yes I agree moving less energy is easier, but that energy needs to move a physical object to produce the sound, and thus there's a bare threshold of energy that is needed in order to adequately move it (for whatever your definition of "adequate" is). Ok sure make the physical thing easier to move, make it more sensitive, but then in doing so maybe it's not so good at translating the electrical energy into acoustic energy. Something something complex transfer function blah blah. So we make the physical thing a little better, but it needs more power, but oops it's super expensive. But hey we can also make it better for cheaper, but now it needs a lot of power, except now getting that much power cleanly is a bit of a problem. Aaaand then we bounce back to the first argument and that's the pendulum has been swinging back and forth since the dawn of electrical sound amplification.

Personally I like the middle ground. Fussing over the endpoints is compromises either way.

 

@yotacowboy , indeed. I think this signal integrity that is preserved all the way through to the transducers, are then destroyed due to poor room acoustics. At least in Indian homes, where we have hard brick walls.

@Boops , it is the solidity and the meatiness of the phantom images of the singers and instruments a speaker system conjures in the room. Like when the image is so solid, you can almost slice it with a knife.

@Climber , yea there are many other circles (Bottlehead, Altec, Klipsch, AudioCircle, AudioKarma, HiFiHaven) where the approach is quite popular. I too haven't seen people be specific about image density, let alone the room interaction.

@E_Schaaf , very much so. Sennheisers with low power DHTs (45, 2A3) is really something.

 

If I'm interpreting solid dense images correctly, and keeping the amp's max output power low, my vote would be for large point source speakers. Either large(12-15") coaxial drivers, or a single wide band driver with a helper woofer crossed below 2-500hz where sound localization becomes more difficult. Supposedly it's not impossible until you get below 80hz, but I can't think of a single wide band driver that can reach that low without sacrificing mid range and high frequency quality, maybe something with a whizzer cone could do it. Large Tannoys and Altecs are the famous ones for big coax drivers, and I think the PAP Trio 15 with a Tang Band or Voxativ in the middle position is crossed at 450hz. The PAP and some of the Tannoy speakers sacrifice some efficiency(96db for the PAP and 92 for the Tannoy 15" monitor gold vs Altec 604 at 101db) and the Altec sacrifices frequency response below ~50hz in anything less than refrigerator size cabinets. I'm sure there are plenty of other speakers out there that fit the bill, those are just noteable examples to consider auditioning. Room interactions play a big part in imaging, so that's something to consider as well, I haven't gotten there yet myself besides a rug and the fact that my room is full of stuff.

 

I should've been a little more direct in what I was saying on that last part: I have spent time with a number of Audio Note systems and have found image density -- which I take to mean solidity and physical presence/weight, as opposed to more ethereal or almost ghostly presentations -- to always be very very good. Can't comment on Bottlehead, Decware, etc etc but at least for AN, they absolutely pull off meatiness with that low-power high-efficency approach.

 

I switched to monophonic playback full-time this year and haven't looked back. With a proper implementation you lose what I would call peripheral sound effects but gain big time in the solidity and palpability of the centre image. Separation doesn't have to suffer that much, or maybe I just got used to it. I've had some people over to listen and they remarked how much the setup sounded like a good stereo, just with less panning. A fringe solution but something worth exploring

I think a big challenge in getting that dense centre image comes down to the nature of stereo reproduction systems. My stereo system has been disassembled for months but when I did have it up I found this tweak indispensable for that reason: http://www.taket.jp/sa_b/sa(b).html it's basically a micro-crossfeed that works at the amplifier level.

 

@bobboxbody , I currently own a pair of Lii F15 which are 15", 97dB sensitive widebanders. I now have them in baffles and even with baffles, their bass response is quite poor. For a long time I used to run these without baffles. and without baffles the bass was almost non-existent, regardless of the amp driving it. However, even without baffles, when it was driven by a 40W Rotel amp, it produced nice solid, dense images. Whereas, my Elekit couldn't quite pull off the same density.

I have talked to a couple of F15 owners online who run their F15 with ~2W amps and they say they get really dense images. But these people are located in the US, where you have dry walls which are less problematic than hard brick walls we have here. Also I have now sold my Elekit to a friend who uses it to drive a pair of 96dB sensitive TL speakers in a decently treated room. I haven't talked to him about it much yet, but another mutual friend who has heard that combo multiple times confirms that the combo produces nice, dense images.

@Climber , ah gotcha, thanks for letting me know. Is it safe to assume you also got to try with their 2A3 amps and they still pulled off dense images?

@k4rstar , exploring mono has been in the back of my mind, for a couple of genres. I will look into it.

 

Hmmm I can't remember if I've heard one of their 2a3s, sorry. I know I''ve listened to their 300b and 211 for sure, as well as one of their EL84 amps which I think they kept at or below 10wpc, and I've always come away thinking they are much more flesh & blood than most.

I actually am strongly considering right now their newest amp that at 28wpc from a quad of EL34 might be their most powerful. Choosing that one not because I don't love their flea watt stuff (I too very much listen for and appreciate that density) but because it's one of their lowest priced offerings and it also will accommodate a wider range of speakers than the rest of their line -- the @Armaegis middle ground, if you will.

 

You might find some info here @EagleWings

https://www.superbestaudiofriends.org/index.php?threads/sensitive-speakers-for-tube-amps.68/

 

I find it’s the opposite with headphones. For awhile the top headphones were low sensitivity planars like the HiFiman HE-6 that needed 6 watts on tap

 

Much if the world has hard brick walls, at least in part. But only since I came to India have I lived in full-on brick/concrete boxes.

The ex-cinema based system that I mentioned, I rated as being closest to being there of anything I'd heard.

Vintage stuff, of course. I wonder if it makes a difference that now, concerts are belted out at large venues with thousands of watts. Is being-there itself a different experience now?

Tannoy Turnberry (I call that stuff "stately-home speakers," but hey, I wouldn't say no to hand-crafted carpentry)... My next being-there experience.

Counterpoint: All audio, and the whole experience of stereo, is an illusion which depends on the literary concept of willing suspension of disbelief. And, as listeners, we are quite good at that, and can extract a being-there feeling out of almost anything![/QUOTE]

 

@Cspirou , I have gone through that thread as well as a couple other threads here, but none discuss the density aspect. I am guessing most of the posters there are already getting decent density, coz I haven't seen any discussion on it.

Indeed. It just so happens that most of my friends and many of the folks I have talked to on this subject are located in the US. So I've made it a habit to mention the nature of the walls we deal with here.

I've heard one such system (an Altec) in a treated room driven by 40W push-pull power. Unfortunately the system didn't do density on the day I visited. Talking to the owner later, he said he had messed something up in the crossover. I wanted to visit him again with my Elekit. He had had a bitter experience in the past with a friend bringing an amp that blew up his tweeter. Since then he doesn't entertain others bringing amps to try in his system.

 

don't fight the room:

Gramophone Dreams #34: The Salt Cellar System | Stereophile.com

Edit - there's some discussion in that article about a lack of phase-fuckery being essential to this broad concept of "tone/image density", too.

 

Nice find @yotacowboy. I remember reading this post of Herb's at the time. This bit from page two struck me:



I had the chance to visit the OMA showroom recently with some SBAF members and @AdvanTech said something similar when we were listening to the giant horn system there: that the horns turned what was literally a far-field listening experience (we were seated about 20 feet from the system) into a near-field one.

I would say that image density was one of that system's strengths, so maybe there is something to the shape of the wavefront that horns can create that allows for a more near-field experience at a given listening distance.

It would certainly help image density in a room with stone walls – like @EagleWings room or the Salt Cellar room – to get more direct sound to the listener.

All this is to say: maybe superior image density is not just in the amp, but in the way a horn-generated wavefront behaves in the room.

 

That's true, actually. If you can't get around reflective room surfaces maybe it's worth exploring the directivity benefits of horns.

The big OMA Imperias definitely sounded dense with the way horn-loading does immediacy and dynamics, but it's also just a commanding system all around.