 Re: blind testing of speakers
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Joined: Jan 2011
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Jacques, the "roll" that using different frequencies plays when calibrating for equal speaker volume is also interesting. Primarily electronic components such as receivers and players have so little variation in frequency response across the 20Hz-20KHz range that using one frequency(e.g. 1000Hz)to set levels equal will result in audibly equal levels for the entire range. Speakers, on the other hand, have much larger variations which often occur at different frequencies for different speakers. For example, if speaker A was 2dB louder at 1000Hz than was speaker B, lowering A by 2dB would result in equal volumes at that frequency, but if B was 2dB louder than A at say 2000Hz(certainly a common possibility)then the 2dB adjustment previously made because of the 1000Hz measurement would result in 2000Hz now being 4dB louder in favor of B.
Using pink noise, which contains the entire frequency range in a way roughly similar to music, rather than a specific frequency when setting levels can result in a better average leveling result when comparing speakers with music selections. It would be interesting to hear Ian's comment on what Axiom uses in equalizing levels. my guess is they usually use band limited pink noise, maybe something like 300-3000 Hz. this should give a good match for the average SLP put out by the speakers.
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Re: blind testing of speakers
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Joined: Jan 2011
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there is "some" difference between the two terms: roll and role. at least i hope so. ;-)
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Re: blind testing of speakers
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Joined: Jan 2002
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Hi J.B,
We try to get the two speakers within about 1/4 dB of each other, because even though our hearing cannot detect that small a difference in loudness (1 dB is considered the detectable threshold of loudness differences) tests have shown that if there is a bit less than 1 dB loudness difference, although we can't "hear" it, the itsy-bitsy louder speaker will be perceived as "better" in the blind tests.
Axiom's new listening room, still in construction, will contain a speaker shuffler to exchange speaker positions to randomize the role (that's ROLE) that room placement variations introduce to speaker testing.
Regards,
Alan
Alan Lofft,
Axiom Resident Expert (Retired)
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Re: blind testing of speakers
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Joined: Oct 2006
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axiomite
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axiomite
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1 db represents the difference in loudness that an average human can detect as being different. However, does perception of sound quality (verses loudness) dip into a fractional level? This I do not know, thus I ask.
Also, it will require more than your average radio shack db meter to accurately measure into small fractions of a db and there is also the variations of the frequencies to consider as noted above.
Therefore, for me, I think that for home listening tests, getting within a db is a reasonable goal but I guess it depends on the answer to the above question.
EDIT: My post was being written as Alan posted his ahead of me. I'll let it stand as I'm too lazy to rethink my questions.
Last edited by Murph; 11/09/11 03:55 PM. Reason: Sniped!
With great power comes Awesome irresponsibility.
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Re: blind testing of speakers
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Joined: Oct 2006
Posts: 6,955
axiomite
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axiomite
Joined: Oct 2006
Posts: 6,955 |
.
Axiom's new listening room, still in construction, will contain a speaker shuffler to exchange speaker positions to randomize the role (that's ROLE) that room placement variations introduce to speaker testing.
I think that, for fun, they should invite Alan to a listening test and have a set of speakers continually 'shuffled' while he is actually listening to them. Just to see what the continual movement effect does to his comments on sound stage and discover if he can actually detect what is happening or will he end up in a fetal position on the floor.
With great power comes Awesome irresponsibility.
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Re: blind testing of speakers
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Joined: Jan 2002
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Aarrrgh!
Going back to your earlier question, the research shows that in the case of loudness differences of less than 1 dB between two speakers that are NOT detectable by listening (but which are measureable with a broadband pink-noise test signal), the louder of the two speakers will be perceived as sounding "better". I don't recall details of how that was defined.
At the NRC, we also found out that if you have a cold or sinus congestion, the reliability and consistency of blind speaker ratings goes out the window. The same can be said of using alcohol or weed before listening tests.
In the latter case, subjects became much less critical and even piece-of-crap speakers were highly rated, simply because the music simply sounded so great while the subjects were under the influence. . .
Cheers,
Alan
Alan Lofft,
Axiom Resident Expert (Retired)
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Re: blind testing of speakers
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Joined: Feb 2004
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connoisseur
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Aarrrgh!
or weed
Cheers,
Alan
heheheh, i found that part very funny Alan.. 
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Re: blind testing of speakers
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Joined: Oct 2006
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axiomite
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axiomite
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Thanks for answering my question Alan. It's always amazing how sensitive human senses can be and also how easily the senses can be influenced.
Also for letting me know that I want a job at the NRC. [Shuffles off to fake a new resume]
With great power comes Awesome irresponsibility.
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Re: blind testing of speakers
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Joined: Sep 2004
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shareholder in the making
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shareholder in the making
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So, what you're saying is that if we can find a reliable drug dealer, we don't need Axioms? 
::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::
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Re: blind testing of speakers
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axiomite
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