Please, not a tubes vs transistors debate.
To repeat, the entire raison d'etre of the Ariel, and it's successor, is a good loudspeaker that is suitable for tube amps in the 3 to 30-watt range. If you don't consider tube amps "accurate", fine, there are lots and lots of speakers that work just great with transistor amps in the 60 to 500-watt range. That's not what this thread is about.
This thread is aimed at people who already own tube amps in the 3 to 30-watt range. This imposes severe constraints on the loudspeaker design, particularly if flat response is also a goal. If the flat-response criteria is relaxed, there a plenty of efficient Lowther/AER/Fostex whizzer-cone full-rangers out there, but that's a different topic, and a different forum.
Given the constraints of 3 to 30-watt amplifiers with output Z's in the 1~2 ohm range, what is possible? I was initially attracted to dipoles until I realized just much equalization they require, which would push this type of amplifier to its limits. 6 dB of boost EQ doesn't sound like much until you realize that a (very) expensive SE or PP 300B amplifier has had its power cut by four times. 6 dB of EQ is trivial in the context of modern Class D 500-watt amplifiers, but it's a show-stopper for triode amplifiers.
What I consider interesting about Duke's design is that it is suitable for owners of low-to-moderate power tube amps, and it creates an ambient impression that is akin to dipoles or electrostats (not the same, but similar in important ways). That's unusual because dipoles and electrostats are typically used with more powerful amplifiers.
To repeat, the entire raison d'etre of the Ariel, and it's successor, is a good loudspeaker that is suitable for tube amps in the 3 to 30-watt range. If you don't consider tube amps "accurate", fine, there are lots and lots of speakers that work just great with transistor amps in the 60 to 500-watt range. That's not what this thread is about.
This thread is aimed at people who already own tube amps in the 3 to 30-watt range. This imposes severe constraints on the loudspeaker design, particularly if flat response is also a goal. If the flat-response criteria is relaxed, there a plenty of efficient Lowther/AER/Fostex whizzer-cone full-rangers out there, but that's a different topic, and a different forum.
Given the constraints of 3 to 30-watt amplifiers with output Z's in the 1~2 ohm range, what is possible? I was initially attracted to dipoles until I realized just much equalization they require, which would push this type of amplifier to its limits. 6 dB of boost EQ doesn't sound like much until you realize that a (very) expensive SE or PP 300B amplifier has had its power cut by four times. 6 dB of EQ is trivial in the context of modern Class D 500-watt amplifiers, but it's a show-stopper for triode amplifiers.
What I consider interesting about Duke's design is that it is suitable for owners of low-to-moderate power tube amps, and it creates an ambient impression that is akin to dipoles or electrostats (not the same, but similar in important ways). That's unusual because dipoles and electrostats are typically used with more powerful amplifiers.
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This is interesting, because one can desing the upfiring speaker as sensitive as possible, too.
Have you tried placing your Azura horns on the floor facing upwards ?
Then you would need totally of 4 horns, maybe, to supplement ordinary stereo triangle.
Actually, for the up-firing application, broad dispersion at 10 kHz is very desirable, and it's also going to need fairly precise EQ to offset the narrowing directivity of the forward-facing horn. That implies an array of dome tweeters, an efficient ribbon, or one or more conical or OSWG type of horns.
The narrow dispersion (at 10 kHz) of the LeCleac'h makes it unsuitable for this particular application. The change in DI should be the inverse of the forward-directed horn; dispersion (or at least level) should increase as frequency goes up.
One of the subtler aspects of the AudioKinesis is the 10 mSec delay. That implies two bounces, not just one, so I'm guessing a bounce off the front wall, followed by a second bounce off the ceiling. So the additional drivers would aimed upwards and also rotated backwards maybe 10~30 degrees. Very likely, optimum aiming will be different for different rooms.
This sounds simple enough, but it's going to require measurements to dial-in the correct dispersion pattern, equalization, and arrival timing between the front and upwards-facing drivers. It's not something I'd want to do subjectively; too many variables, and too dependent on recording characteristics.
The narrow dispersion (at 10 kHz) of the LeCleac'h makes it unsuitable for this particular application. The change in DI should be the inverse of the forward-directed horn; dispersion (or at least level) should increase as frequency goes up.
One of the subtler aspects of the AudioKinesis is the 10 mSec delay. That implies two bounces, not just one, so I'm guessing a bounce off the front wall, followed by a second bounce off the ceiling. So the additional drivers would aimed upwards and also rotated backwards maybe 10~30 degrees. Very likely, optimum aiming will be different for different rooms.
This sounds simple enough, but it's going to require measurements to dial-in the correct dispersion pattern, equalization, and arrival timing between the front and upwards-facing drivers. It's not something I'd want to do subjectively; too many variables, and too dependent on recording characteristics.
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I am sorry but "flat response" with a "2 ohm output Z" just isn't going to happen.
Please see for instance: http://www.geocities.jp/arai401204/Experiments/TubeAmp/TubeAmp.html
Of course, one may still like and prefer the sound of low-power valve ("tube") amps nonetheless, but flat frequency response into a real (i.e. non-perfectly resistive) speaker load is NOT within their capability, full stop.
I have raised this point a number of times before, but so far no-one has been able to provide any factual measurements to prove otherwise.
Respectfully,
Marco
So you keep saying. Over and over.
Despite the results posted in this thread and on Lynn's website.
Lynn,
The upward rear firing tweeter angles et al I concur with. Have you considered an AMT for the super tweeter. While not the flattest with their typical rising top end something like the Airborne RT 20021 or Datyon Audio Mini-8 should work quite well in this application once the response is tweaked.
The upward rear firing tweeter angles et al I concur with. Have you considered an AMT for the super tweeter. While not the flattest with their typical rising top end something like the Airborne RT 20021 or Datyon Audio Mini-8 should work quite well in this application once the response is tweaked.
While respecting Lynn's wishes to not make this about SS vs. tubes, I will just add that it is fairly easy to take the Zout of your amp into consideration when designing crossovers and tuning your boxes. Bass is typically one of the most affected areas for the higher Z and your box tuning can help with that. So in the end, it doesn't seem to be as big of a deal as folks make.
In your link he compares the 8ohm tap (Zout ~4ohm) to the SS. By eyeball the 4ohm tap (Zout closer to 2ohms) looks a lot closer to the SS line. Lynn is talking about amps in the 1-2ohm Zout region.
Here is something I came across on another forum. It is a pair of old Phase Linear speakers (or so I am told). Each has open-baffle mid-bass, sealed dipole mids and 5 tweeters firing up into cones to disperse the high frequencies in a 360º pattern. They share a single subwoofer where the bass is supplied by two mass-loaded woofers in a down-firing reflex box. The guy who owned them said that he remembers them to have a very 'spacious sound'. I'll bet they did, probably along with some very diffuse imaging. But considering what has been discussed, with up-firing tweeters and the like, I thought I'd share it here. Does anybody remember these? Any more info on them?
An externally hosted image should be here but it was not working when we last tested it.
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I remember when Bob Carver demo'd a pair of those at our Audio Club in the early to mid 80's. Maybe it was Bob's Music selection, but I remember thinking they had a somewhat shrill higher register and a rather unfocussed sound. His later Carver "Amazing" speakers were much, much better to say the least!
Best Regards,
TerryO
That was my impression too; very bright and shrill, and obviously not flat. Imaging was predictably diffuse thank to the multiple HF radiators and non-coincident arrivals. It was never clear to me what kind of sound Bob Carver was aiming at, since his products all sounded rather different from each other.
The problem with a lot of multidirectional speakers are the overlapping arrivals from the multiple drivers: these gives a complex time signature, as well as comb-filtering effects that are strongly position-dependent.
This is revealed subjectively by listening to steady pink-noise stimulus and slowly moving side to side over several feet. If you hear weird whistling or swishing sounds that sound disconnected from the steady waterfall roar of the pink-noise, that's comb-filtering. It's difficult to hear this artifact with sparse, low-reverb rock, blues, or jazz, but it's pretty obvious on symphonic and particularly choral music.
The clever thing about the AudioKinesis is the shadowing created by putting the additional drivers behind the main cabinet, and the relatively long bounce path. I am also pretty sure that the additional drivers are going to need equalization that is independent of the main system ... however, it's probably not important that the additional drivers need to be as efficient as the main speaker.
A 90-degree constant-directivity horn radiates very little energy outside of the intended radiation pattern; the forward cone is where nearly all the acoustic energy is. The rest of the sphere is almost dark, so even a little bit of additional energy, say 6 dB down, is going to brighten up the overall sphere quite a bit. An intentional lowering of DI goes against modern controlled-directivity philosophy, but I personally feel it's the right way to go with 2-channel recordings and 2-speaker playback.
I have had very enjoyable results using wholly separate CD 2 way rear-firing- they can be moved and adjusted and attenuated etc for balance, or even entirely located differently than the main. Another interesting effect can be achieved using a far less efficient speaker (or an attenuated one) front-firing along with the mains- some randomization and associated comb filtering sure but it can also do things like minimize the depth of floor bounce or crossover lobe notches.
Yes, the thing is to avoid very deep frequency and spatial nulls. It only takes a little bit of additional energy to "fill in" the lowest-energy part of a notch. This is a bit like combining fluorescent and tungsten lighting; the efficient FL has a rough spectrum, with sharp peaks, along with strong 100/120 Hz time pulsing, while the inefficient tungsten light has a smooth, continuous spectrum and a fair amount of time-averaging.
The problem I have with many (not all) constant-directivity speakers is a "spotlit" quality to the sound; everything is very clear and sharp, but real, acoustic music in a normal room doesn't actually sound that way. You're more aware of the sound filling the space, the physical presence of the instrument, and the performer changing their performance to match the "feel" of the space.
The problem I have with many (not all) constant-directivity speakers is a "spotlit" quality to the sound; everything is very clear and sharp, but real, acoustic music in a normal room doesn't actually sound that way. You're more aware of the sound filling the space, the physical presence of the instrument, and the performer changing their performance to match the "feel" of the space.
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Lynn,
For what it's worth, Dan Wiggins once opined that short duration dips were very seldom audible, however Frequency Peaks and Spikes were easily detected and heard in playback. This problem could easily be due, in part, to the design and construction of the crossover.
Best Regards,
TerryO
The different luminous flux and color rendering index blending analogy works as a good example model.
Maybe this is why horns can sound good / better with open back (cone) drivers. I am listening to PM2A Lowthers on 200 Hz front horns, and 15" Vitavox K15/40 drivers on 50Hz horns, with open backs in the room corners. Imaging and depth is good, applause ambience realistic. Counter to what you might expect.
martin
Sure, if you have several ohms of output impedance in your amp and you don't include that in your design of the crossover, you will end up with a different response than designed. So you just need to include the amp in your design process - problem solved. If you use an active crossover you can do this by measuring the response of the drivers using the actual amp you will use to drive them. If you want to design a passive crossover, I think it would be easiest to measure with a low Z out amp, measure the Z out of your intended amp, and include that in your crossover simulations. That's what I've done before.
The only problem comes when you want to design a speaker that other people will use with amps with different Z outs. In that case you could try to achieve as flat an impedance curve as possible, although I'm not sure if the drawbacks of doing this would outweigh the downsides of ignoring the problem.
If you were making the speaker to listen to you can forget the issue of ruler flat FR. If you are making it to sell on specs then that is another story.
The problem as I see it is that the device itself or the set of devices should be the best possible with the flattest inherent FR and as benign impedance curve. This will give the best results in the end with the least amount of manipulation to correct aberrations in FR or impedance problems. When trying to correct these problems with a passive crossover or even and active xo it is that often correcting the FR makes the phase response much worse, we can't look at FR in isolation, you do need to consider minimizing phase turns for the best sound possible. I see all this manipulation going on sometimes without consideration of the real end result that will appear at the output of the loudspeaker. Always use the KISS principal, keep it simple stupid!