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Old 30th October 2012, 12:27 AM   #1
Remlab is offline Remlab  United States
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Default HD and IM perception in loudspeakers..

I'm familiar with Geddes and Voishvillo's studies on HD perception and have always wanted to ask this question(Hopefully to DR. Geddes).. Can HD in loudspeakers potentially be perceived in long term listening as an "ill at ease" feeling that makes you wan't to stop listening to the music? In other words, after listening to music for, let's say an hour or two on an accurate, text book(D'appolito style?) designed speaker, you say to yourself, The sound is amazing! So why do I wan't to stop listening and do something else? Whereas the same design(With the same sized drivers and identical measurements) using low distortion drivers may have a " Listen all day" sound. Is there a possibility for this? I'm pretty sure that the Geddes studies(Done with 25 college students and real music) were relatively short term in nature and may not have accounted for this possibility. Or is it a matter of me not being familiar enough with the studies?
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Last edited by Remlab; 30th October 2012 at 12:37 AM.
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Old 30th October 2012, 12:42 AM   #2
sreten is offline sreten  United Kingdom
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Hi,

The result of aural studies very much depends on the choice of participants,
e.g. years ago many "students" much preferred the sound of the raucous
but lively AR18S to clearly far better "hifi" speakers like the LS3/5A.

Listening is a learning process, you do become more discerning.

rgds, sreten.
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Old 30th October 2012, 01:35 AM   #3
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sad isn't it ?

Our once favorite music is cast aside for cleaner recordings.................

Our systems usually become specialized at certain genres of music.

They will be 20% better on said music and 40% worse on others.


For some, distortion is annoying, others is phase, others is far/field near field dispersion, some demand flat freq response at listening chair, and others demand 20-20khz at 110db.
It is a mixed bag, and disasterous when we start shifting.

I'm changing to a near field full range driver fan, but will not give up my subs !!!!!!!!

But, yes, a cleaner driver (less harmonics and less energy storage) usually sounds better to our ears, but at what extra dollar cost ?
And do we now have more resonances to deal with ?

I'm thinking the kevlar/carbon fiber are doing well, but they usually have 2 resonances.

Last edited by norman bates; 30th October 2012 at 02:05 AM.
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Old 30th October 2012, 01:45 AM   #4
pski is offline pski  United States
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Default Lots-of-what here !

Philology : not here !
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Old 30th October 2012, 03:42 AM   #5
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I can listen to my Gedlee Summas for hours on end. IIRC, Geddes is more concerned about diffraction than distortion.
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Old 30th October 2012, 05:43 AM   #6
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Don't people even consider that the greatest amount of distortion in any stereophonic set up is the 6ft wide blob of confusion between the speakers?
Now that's fatiguing!
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Old 30th October 2012, 08:20 AM   #7
Remlab is offline Remlab  United States
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Quote:
Originally Posted by Remlab View Post
I'm familiar with Geddes and Voishvillo's studies on HD perception and have always wanted to ask this question(Hopefully to DR. Geddes).. Can HD in loudspeakers potentially be perceived in long term listening as an "ill at ease" feeling that makes you wan't to stop listening to the music? In other words, after listening to music for, let's say an hour or two on an accurate, text book(D'appolito style?) designed speaker, you say to yourself, The sound is amazing! So why do I wan't to stop listening and do something else? Whereas the same design(With the same sized drivers and identical measurements) using low distortion drivers may have a " Listen all day" sound. Is there a possibility for this? I'm pretty sure that the Geddes studies(Done with 25 college students and real music) were relatively short term in nature and may not have accounted for this possibility. Or is it a matter of me not being familiar enough with the studies?
So there's no confusion, I'm not referring to D'appolito "mtm". I'm referring to his standard design and measurement criteria.
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Old 30th October 2012, 08:31 AM   #8
Remlab is offline Remlab  United States
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Quote:
Originally Posted by Patrick Bateman View Post
I can listen to my Gedlee Summas for hours on end. IIRC, Geddes is more concerned about diffraction than distortion.
Yes, that's true. But his speaker designs also have exceedingly low levels of HD. So in long term listening, is it the HOM and diffraction control? The ultra low HD? Or an obvious combination of the three? I mean, if harmonic distortion is so audibly unimportant, why do his designs use drivers with such low Harmonic distortion? Could it be just a dynamic range issue?
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Old 30th October 2012, 09:09 AM   #9
tvrgeek is offline tvrgeek  United States
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I know for sure: My wife has super sensitive hearing where distortion causes her actual pain. Only when I stepped up to much higher quality drivers and caps that she is happy. I can correlate what she hears with a slight edge on a trumpet ( Harry James) that should not be there or a metallic edge on nylon guitar strings, ( Julian Bream ). I just replaced some $20 Vifa tweeters with some $60 Seas, small tweaks for voicing, and to her ears, went from painful to tolerable. For me, the voicing is slightly better. My ultimate test is Join Mitchel's voice. If Ladies of the Canyon sounds right, you have it.

One clue. The lower the distortion, the louder it can play without being objectionable. A Sax as loud as live is painful on most speakers. Only when the distortion comes down can I take that kind of level in my room.
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Old 30th October 2012, 10:55 AM   #10
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Harmonic distortion is first good indicator of driver performance, and has direct relationship to intermodulation distortion. IMD by nature is specific to signal content seen by driver over its intended bandwidth. Classic big offenders are signals at driver resonance, where low voltage is capable of high excursion, mixed with higher voltage/current signals near driver's upper range.

Often in speaker design temptation is to maximize range of drivers, especially 2-way; Often 6-8" drivers are crossed between 2kHz-4kHz, well beyond range where good piston performance is possible. Then with even a 24dB/octave crossover, driver is seeing significant energy at 3kHz-7kHz, stimulating break up modes of the driver. Lots of IMD. Acoustic driver phase through crossover region becomes signal dependent, and is thus unstable. Sound quality and stereo imaging suffer badly.

Even in middle of driver's target bandwidth IMD damages performance; When two frequencies are present that are close, such that difference is resonance frequency of driver/box, this signal becomes present, and is most unwelcome. Only good solution is lower distortion driver, and keeping power in check.

Above applied to tweeter dictates that tweeters should have much more linear travel than predicted excursion demand in desired operational band.

Quote:
I just replaced some $20 Vifa tweeters with some $60 Seas
I'm guessing, that this Seas driver has more linear travel than Vifa it replaced.

Tweeters benefit greatly in active systems where 48dB/octave crossovers and beyond are possible.

Regards,

Andrew
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