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Old 30th May 2013, 01:57 AM   #8861
ra7 is offline ra7  United States
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Thoglette, Kindhornman, others,

The rising level of distortion percentage at lower output is not because of heat dissipation or other causes. It is simply the percentage of noise becoming a higher fraction of the signal. For example, at 100 W, the distortion maybe 1%, getting down to 0.1% at 1 W, and then increasing back up to 0.3% at 0.1 W. The proportion of noise is the same at all levels, but as the levels decrease, it becomes a larger percentage. For an amp biased in Class A, the distortion usually rises smoothly with level after getting out of the noise.

This is of course my noob understanding. The 1/3rd power test is only to ensure that it can stay thermally stable over long periods.

Last edited by ra7; 30th May 2013 at 02:00 AM.
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Old 30th May 2013, 02:14 AM   #8862
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Quote:
Originally Posted by Lynn Olson View Post
No, I have not. I have corresponded with Thorsten and have a lot of respect for his designs, although we part company about our favorite converters ... he's a TDA 1541 guy, and I like the Burr-Brown family the best. Both are really, really good, though.

Thorsten uses the TDA 1541 ladder converter for 44.1/16 Red Book CD's, and a sigma-delta converter for high-res content. Considering how fantastic the Burr-Brown ladder converters sound with 88.2/24 and 96/24 content, I find this an odd choice, but Thorsten's the expert here.
Hi Lynn,
Thanks.
The AMR CD-777 uses UDA1305AT DAC chip, which is a Multibit DAC, like the TDA1541. So far, that player is the best CD Player or DAC I heard. (I didn't hear the AMR CD-77 and other players, or DACs, which I cannot afford). I wondered if the Monarchy DAC is better than the CD-777. I don't know of anyone in my country who may have it, so I cannot listen to it. There are but few people on whose listening impressions I'd be willing to follow, without hearing myself. So, for the time being, I'd stay with the CDP I have.

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Originally Posted by Lynn Olson View Post
I have noticed that audiophiles who like DACs that use sigma-delta converters listen to Class AB transistor amps, usually with low-efficiency loudspeakers, while the ladder/R2R enthusiasts often have moderate-power valve amplifiers, typically in the 3 to 30-watt range.
I have fairly low efficiency speakers, tough unconventional ones (Brodmann VC-2).

The tube power amps I tried, in pentode mode I didn't like their sound, while in triode mode didn't have enough power for my speakers and for the volume in which I listen to symphonies. However, I do get what you say about the sound quality of DHTs.

The power amp I have right now is the Pass Labs XA 30.5, which isn't a mere 'Class AB transistor amp'.

I wish I'd find speakers of high efficiency, that will sound at least as good as my present ones, which I could afford. (Being retired, I don't have big money to spare).
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Old 30th May 2013, 09:36 AM   #8863
tomtom is offline tomtom  Slovakia
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Originally Posted by Pano View Post
Thanks Lynn. Does it still sound good when you turn it down, or does it "come alive"when you turn it up? Two common problems that were demonstrated to me almost 30 years ago in Paris. I still don't understand why, either. But it certainly is a common phenomenon.
This phenomenon has perfectly reasonable explanation /if you want to believe it/ in Tooles book.

Its again reflections to blame . Reflection are good - they enriched sound no doubt about. They change perceived timbre and enhance localization etc. /of course only some good reflexion/

There is threshold value in intensity for reflection to work. Too little and it doesnt work /too much and it doesnt work either/ . Try put symphony orchestra in room three time as big as usual and it will sound weird.

You must put certain amout of energy to build up reflection to above threshold level.

Of course different speakers has different interaction with room.
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Old 30th May 2013, 10:08 AM   #8864
ScottG is offline ScottG  United States
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Originally Posted by tomtom View Post

Of course different speakers has different interaction with room.
Most speakers, placed in the same location, react similarly in a room - particularly as freq.s descend. With that - the reflection "cause" is rather hollow argument for a speaker "coming alive".

In *acoustics* however, from which the argument is derived - it's a fairly well documented phenomenon. But there it's live sound in a larger venue which is pretty far removed from stereo reproduction on a set of loudspeakers in a small room.

Unfortunately Toole's book does that a LOT ("grabing" from the study of acoustics), but it's understandable given how little quality research there is into such esoteric topics of loudspeaker presentation.
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Old 30th May 2013, 10:23 AM   #8865
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Originally Posted by Lynn Olson View Post
Tonality and resolution at low levels was one of the big differences between the JBL 2226 and the GPA 416-Alnico. The JBL sounded flat and dull, while the 416-Alnico had the trademark Alnico sparkle to the sound, and most noticeably at low levels. If you want to hear the difference between magnet materials, and overhung vs underhung voice coils, low-level listening is where it is most apparent. IslandPink, please tell us more about the sound of the Supravox 285GMF, especially how it compares to prosound drivers.
That's what I found in general too when comparing more 'old school' (or the very few modern but 'hi-fi oriented') high efficiency woofers to their 'pro sound' siblings.
The way I rationalize the difference is as follows:

at (very) low levels, the woofer is barely moving at all, and having a highly compliant spider and outer suspension (high Cms) and especially low overall mechanical resistance (low Rms) become critical in allowing the low-level detail to come through unhindered.

Coming to Lynn's example, both the GPA 416 and JBL 2226 are about as efficient at ~ 97dB/W(1m).
However, the GPA woofer has Cms = 0.78 [mm/N] and Rms = 1.3 [N*s/m], while the JBL has Cms = 0.16 [mm/N] and Rms = 4.9 [N*s/m].

Of course, there's a manufacturing reason for these differences. The JBL woofer, with its comparatively 'stiff' suspensions is quite a bit sturdier if driven hard in PA applications.
Unfortunately, the flip side of this is impaired low-level detail retrieval, and fewer and fewer modern high-efficiency woofers seem to be produced with the latter goal in mind.

Interestingly, as far as low-level detail retrieval is concerned, I have found that controlling these two parameters may possibly be even more important than achieving the ultimate in actual efficiency.

For instance, the Fostex FW405N 15" woofer (~94 dB/W(1m)) has Cms = 0.34 [mm/N] and Rms = 2.5 [N*s/m]. Not quite GPA-like, but still much 'better' than the JBL 2226. And guess what? It sounds much more detailed than the latter (in spite of being 3dB less efficient - it has approximately the same moving mass at ~100 g but a 'weaker' magnet: BL^2/Re = 36 [N^2/W] vs. 75 [N^2/W] for the JBL).

In general, I set for myself the following 'rule of thumb': Rms < 3 (approx.).

Marco

Last edited by marco_gea; 30th May 2013 at 10:38 AM.
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Old 30th May 2013, 11:17 AM   #8866
tomtom is offline tomtom  Slovakia
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Quote:
Originally Posted by ScottG View Post
Most speakers, placed in the same location, react similarly in a room - particularly as freq.s descend. With that - the reflection "cause" is rather hollow argument for a speaker "coming alive".

In *acoustics* however, from which the argument is derived - it's a fairly well documented phenomenon. But there it's live sound in a larger venue which is pretty far removed from stereo reproduction on a set of loudspeakers in a small room.

Unfortunately Toole's book does that a LOT ("grabing" from the study of acoustics), but it's understandable given how little quality research there is into such esoteric topics of loudspeaker presentation.
As soon as you are not in anechoic chamber you are dealing with acoustic
In stereo reproduction case you can add little bit of cognitive science

But serious. I dont know ANY speaker which can play silent as good as at its optimum level.

And about real acoustic event. Tell me which one play really silent? Musical instrument are designed to play LOUD. Because at the time they was invent there was no amplification. This was also supported be designing auditorium rooms to have right amount of reflection to energize rooms. In fact they want to play louder and for more people they use more instruments/players. - this was main drive behind orchestras. In cognitive sense to some extent louder /and with reflections is better/ - this has nothing to do with acoustic.

So do we have any reasonable proof that one speaker can play better silent than another? At which condition - at your home with right cognitive condition glass of good wine, candle glow - low background noise - or at showroom or exhibition - where evil hiend speakers are revieved how they can play silent? And no offense - im really just asking
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Old 30th May 2013, 12:12 PM   #8867
kevinh is offline kevinh  United States
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Originally Posted by marco_gea View Post
That's what I found in general too when comparing more 'old school' (or the very few modern but 'hi-fi oriented') high efficiency woofers to their 'pro sound' siblings.
The way I rationalize the difference is as follows:

at (very) low levels, the woofer is barely moving at all, and having a highly compliant spider and outer suspension (high Cms) and especially low overall mechanical resistance (low Rms) become critical in allowing the low-level detail to come through unhindered.

In general, I set for myself the following 'rule of thumb': Rms < 3 (approx.).

Marco

Very interesting insight.

It will be fun to look at drivers with similar characteristics.
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Old 30th May 2013, 01:49 PM   #8868
Elias is offline Elias  Finland
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Quote:
Originally Posted by marco_gea View Post
However, the GPA woofer has Cms = 0.78 [mm/N] and Rms = 1.3 [N*s/m], while the JBL has Cms = 0.16 [mm/N] and Rms = 4.9 [N*s/m].


Marco

Beyma SM115/N could be interesting to try.

http://profesional.beyma.com/pdf/SM-115%20NE.pdf
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Old 30th May 2013, 02:02 PM   #8869
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marco_gea,
Yes the T/S parameters are very different between a hifi speaker and one intended to be used for PA sound production. The PA speaker has a very different job to do than our beloved HiFi speakers and fs will typically be very different between the two types of drivers. What you are looking for in a PA driver is just so different than what someone is trying to recreate in their home sound system. High power handling and SPL level are the purview of the Pro Audio type speaker and working in smaller enclosures with multiples ganged together is what is looked for. At the same time for live applications extreme low frequency response isn't even desired, it will create nothing but problems for the sound engineer if the PA is producing 20hz low frequency as that is going to end up in a feedback loop back to the microphones. A typical feature on any mixing console at a live event is going to have a cut switch that will have a roll-off point of 60hz approximately just for this problem and will be used in most closed rooms and even in many outdoor applications. So the response curve that is desired is very different than what we can have with a simple playback system. I think this is what drives the major differences between the two types of speaker design, the use in either production of a live event or the reproduction of that event. One device is not better than the other, they do have a different job to do.
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Old 30th May 2013, 02:08 PM   #8870
Elias is offline Elias  Finland
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Originally Posted by Kindhornman View Post
Yes the T/S parameters are very different between a hifi speaker and one intended to be used for PA sound production. The PA speaker has a very different job to do than our beloved HiFi speakers and fs will typically be very different between the two types of drivers.

Beyma SM115/N has fs = 29 Hz according to specs. Not bad for a PA driver
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