speaker distortion - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 12th July 2004, 12:31 AM   #21
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

Quote:
who said they could hear 0.00001% thd?
Did anyone?

IMHO, THD speaker measurements, just like amplifier THD measurements, don't say didley squad about how they sound compared to the sound of a live, unamplified acoustic instrument.

If high-end companies stuck with accepted tools to measure performance of the gear they put on the market we'd probably still be stuck with all those "fabulous" Phase Linear amps and their ilk.
IOW, we would not even be talking about "high-end" anyway...

It must be rather disconcerting to discover that your trusted measuring gear doesn't even begin to correlate with what it's thought to do...

Cheers,
__________________
Frank
  Reply With Quote
Old 12th July 2004, 08:43 AM   #22
diyAudio Member
 
Join Date: Jul 2001
Location: The Netherlands
Hi Till,

THanks for your reply. I think I'll make it my next project to make acoustic distortion measurements. We could do the same measurement and compare? Then it might be interesting to agree on some test-standard.. like 80dB, 600Hz, 1mtr etc?

Mean time I need to adjust my pure-sine-oscilator (which has abouyt -105dB THD) or make a test CD, make a good mic-preamp, make a microphone (got several spieces of panasonic capsules) etc.... I got a proffesional callibrated 16bit 200KHz DAQ ADC card (National Instruments) and software to do the THD measurements with ...

Greetings,
Thijs
  Reply With Quote
Old 12th July 2004, 10:19 AM   #23
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
Just a few thoughts:

1.) Crossover distortion seems to be very nasty. Does a speaker produce it and do single-ended class-A amps produce it ? I think everyone knows the answer, and it is therefore not that hard to guess why (and I belive that it IS true) a class A amp with 0.01% THD @ o,1 Watt sounds better than an AB amp with 0.01%
THD @ 1 Watt, when driving a high-efficiency speaker.

2.) THD of speakers is heavily SPL dependant. So the figures given at the beginning of this thread are in fact meaningless. If this figures are from large P.A. speakers, driven a max power then I wouldn't care about 10% THD that much. Keep in mind how much THD the ear would produce at such insane SPLs ! Many P.A. speakers produce very low THD at domestic listening levels. Thats one advantge, amongst others (and there are NOT only advantages) of generously dimensioned P.A. components used at home.

3.) The same nonlinearities that generate THD, generate IMD as well. While the harmonics generated by THD are often very close to an instrument's natural harmonics (don't forget that not all harmonics of instruments are exact integer numbers of the keynote) this isn't true for IMD. There will be spectral content where there wasn't any before. And there will be content in the stereo image where there wasn't any either. Or in simple words: IMD is muddying up the sound (and every component in the chain makes the mud deeper). Since speaker drivers usually reproduce a small portion of the frequency range and since they are the last stage of the chain (disregarding room and listener) they might be the least culprits regarding IMD. IMO it wouldn't hurt to reduce an amp's good THD value of 0.0001 % down to 0.0000001 % even when driving a speaker with 1 % THD at 100 dB SPL - if it can be done at 1.) reasonable cost and 2.) without degrading other parameters.

Regards

Charles
  Reply With Quote
Old 12th July 2004, 01:19 PM   #24
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
Isnt speaker distortion far more benign then amp distortion anyway?
__________________
What the hell are you screamin' for? Every five minutes there's a bomb or somethin'! I'm leavin! bzzzz!
  Reply With Quote
Old 12th July 2004, 01:24 PM   #25
Banned
 
Join Date: Apr 2002
Location: Germany, Clausthal
Quote:
Isnt speaker distortion far more benign then amp distortion anyway?
this is what phase_accurate tells in the posting above your: yes, in case you look at normal push pull / AB amps. No in case you look at SE class a amps. The speaker will not make crossoverdistortion, the push pull amp will.
  Reply With Quote
Old 12th July 2004, 01:44 PM   #26
diyAudio Member
 
Join Date: Jul 2001
Location: The Netherlands
Hi Phase_accurate,

1] Could be correct, but this was not the issue.

BTW the gainclone at 1W is more lineair than a ZEN at 0.1W. My measured spectra show little or no higher harmonis at a gainclone; crossover distortion seems to be pretty low then. (and I'm NOT a gainclone fan!)

2] Yes, THD for speakers is EXCURSION (is related to, but not identical to SPL, freq depended!) dependent, that's why I want to measure my own speakers at say 80dB spl.

3] THD and IMD are so much related that we could stick to THD for now. Personally I suspect the speakers to be the LARGEST culprits. Various publications show relative large Nonlineairity of speakers, check the web, the brochures os various speaker manufactures etc.

I think it's time for some hard numbers guys... going to the soldering iron now.. het thos measurements done!


Cya,
Thijs
  Reply With Quote
Old 12th July 2004, 02:03 PM   #27
Banned
 
Join Date: Apr 2002
Location: Germany, Clausthal
Quote:
BTW the gainclone at 1W is more lineair than a ZEN at 0.1W. My measured spectra show little or no higher harmonis at a gainclone; crossover distortion seems to be pretty low then. (and I'm NOT a gainclone fan!)
did you measure the chip also at very low Watt, and did you measure at some higher frequencies? like 5 or 10 kHz. And also the gain you set on the chip may influence it.
Attached Images
File Type: jpg image0037.jpg (5.8 KB, 70 views)
  Reply With Quote
Old 12th July 2004, 02:06 PM   #28
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Default Re: speaker distortion

Konnichiwa,

Quote:
Originally posted by millwood
here is a particular speaker (by a well known high-end brand name) and its thd figures:

2nd harmonic:
100hz: about 10%;
1000hz: about 0.5%;
10Khz: about 5%

3rd harmonic:
100hz: about 10%;
1khz: about 0.2%;
10khz: about 0.5%.
Sounds quite reasonable for 96db/1m if that's where it is taken at and barely average for 90db/1W .

Quote:
Originally posted by millwood
who said they could hear 0.00001% thd?
Hmmm. Depeneds entierly upon the actual spectrum of the 0.00001% THD and the presence or absence of other "non-harmonic", "non correlated" or "noisefloor modulation" (I am still looking for the best term to imply a signal dependent noisefloor whose content appears not correlated or harmonically/IMD related to the signal).

Some interesting work on distortion has been done by Earl Geddes:

http://www.gedlee.com/distortion_perception.htm

It is quite interesting to compare the sound samples given.

Sayonara
  Reply With Quote
Old 12th July 2004, 02:11 PM   #29
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
Quote:
BTW the gainclone at 1W is more lineair than a ZEN at 0.1W. My measured spectra show little or no higher harmonis at a gainclone; crossover distortion seems to be pretty low then. (and I'm NOT a gainclone fan!)
O.K. When I was younger I would have listened to a 109 dB efficient Speaker at 0.1 Watt or even 1 Watt.
Nowadays it would be closer to 0.01 Watt (even less on average). The less power, the better it looks for speaker and single-ended, linearity-wise.

Quote:
Personally I suspect the speakers to be the LARGEST culprits. Various publications show relative large Nonlineairity of speakers, check the web, the brochures os various speaker manufactures etc.
If you look at the figures alone you are definitely right. But be aware that things get worse when they are already fed with garbage (and every single stage adds more garbage to the one that it was already fed with) thats why I think it is still worth to have low THD amps even when the speaker's THD is higher.
IMD generated by a nonlinear device is larger the broader the part of the audio range it has to "process". If you split the signal into several spectral parts before feeding it to a nonlinear device, you will have less IMD (or maybe less disturbing IMD) in the end. That could be one reason for nonlinearity within speakers being less severe than amp related nonlinearity. If you include the power amps into such a topology (i.e. active x-over) you will reduce amp-related IMD as well.

Regards

Charles
  Reply With Quote
Old 12th July 2004, 02:13 PM   #30
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa,

Quote:
Originally posted by cunningham
also typically you can almost eliminate speaker distortion by never exceeding 60% or so of rated RMS power.
Hmmm. You think so? From experience most speakers start to exceed 0.5% THD at around 1 Watt applied. The above is for cone/dome speakers operated within the linear throw and is a direct result of the magnet system construction and based on a cubic function of the current (hence the 1 Watt reference).

Measures can be taken to reduce this level of distortion, which are rarely found in "High Fidelity" and "High End" speaker drivers due to cost issues - even in supposedly "cost no object" design. Yet even with all distortion mechanisms minimised I find "no distortion until 60% RMS Power" to be a rather adventerous assertation, to be kind about it.

Also, I find that in many "HiFi" speaker drivers compression starts to set in around the 1 Watt Level. Again, there are measures that can be taken, but rarely are for "High Fidelity" Drivers.

Sayonara
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Measuring speaker distortion ak_47_boy Equipment & Tools 0 12th September 2008 02:22 AM
Speaker Workshop Distortion Question arc2v Multi-Way 47 27th July 2007 02:38 PM
Distortion Measurements with speaker workshop noodle_snacks Multi-Way 1 6th September 2006 02:28 AM


New To Site? Need Help?

All times are GMT. The time now is 01:38 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2