Drivers/loudspeaker distortion .. i want to know the truth!!

[JinMTVT]

ahah
i've been searching this forum in vain,or with just too many possible threads to go through ...

So i didn't get any good information on speaker distortion!

What are the different type of distortions created/introduced by drivers/loudspeakers ?

I've read numbers like 2-4% in this forum,is it correct ?
Do we really settle for 2+% distortion from our speakers but get all freaked out by the 0.005% distortion from amplifiers?
omg!!!

So if it is correct to assume near 2% dist, the speakers would be tne weakest link of an audio system ?? thus where the greatest enhancement is possible?

Also, what are the means we do have to try and reduce distortion to more acceptable levels ? is there some type of drivers that offer less distortion with equal power? ..again it should be a compromise between all parameters ..

please share with me(us) your knowledge about this problem ..

thanks all for your time

[John Sheerin]

2% distortion from a driver is pretty good, but of course that depends on level. I've seen way over 20% THD (mostly 2nd and 3rd harmonic) from some drivers when driven at any kind of significant level. Basically once you start to make a speaker produce sound, it starts to distort. The harder you push it, the more it distorts (usually).

Why don't you go read Sigried Linkwitz's website? He talks quite a bit about various kinds of distortion. But basically, yes, the loudspeaker is one of the weakest links in the reproduction chain and the reason you can't find any good data is because it all looks so bad compared to THD numbers for amps, for example (which are fairly meaningless in any case).

[Mr Evil]

Yes, loudspeakers introduce orders of magnitude more distortion than preceding stages. There are ways to reduce distortion, but it's a compromise. Drivers made of extremely rigid materials, horns and electrostatic speakers offer lower distortion. Bringing the speaker inside the feedback loop can also lower distortion significantly.

[joe carrow]

Yes, JinMTVT, speakers are the weakest link. A speaker with 2% distortion (at a good listening level) could actually sound quite good. Many speakers produce over 10% distortion as you turn up the volume!

Distortion in a speaker is proportional to the electrical power, and to the cone movement. Reducing either of these tends to reduce distortion. Schemes to do this include horn loading, line arrays, and splitting the frequency spectrum across a larger number of drivers.

Horns reduce the required cone movement (and power) by providing something stiffer for the cone to push against- you'll hear horns reffered to as acoustic transformers. I'm still not up to speed on acoustic impedance- but the general idea is that you put a horn on a driver, and the driver doesn't have to move as much to create the same level of sound.

Line arrays and multi-driver setups; such as a 3 way, 4 way, or even 5 way systems allows each driver to reproduce a section of the audible range that it is most comfortable with, reducing the power sent to it and reducing cone excursion when you move a highpass point up in frequency. The tradeoff here is that they can be tough to design, and more large numbers of drivers are expensive.

Don't forget that the driver is not the only part of the speaker that can cause distortion, also be aware that there are different types of distortion! Cabinet wall resonances are bad, so are standing waves and reflected sound inside of cabinets.

Overall, I would have to say to look at both http://linkwitzlab.com and http://sound.westhost.com/articles.htm for more information and some articles.

I am currently trying to learn more about speaker distortion, and how I can build a super-cheap copy of the Orion, so I will be keeping an eye on this thread to see if more links show up.

Joe

[John Sheerin]

Originally posted by Mr Evil
Yes, loudspeakers introduce orders of magnitude more distortion than preceding stages. There are ways to reduce distortion, but it's a compromise.

The compromise is cost / complexity of the driver design. You don't have to go to horns or other more exotic topologies to try to reduce distortion in drivers (although they can help with other things).

[JinMTVT]

ok thanks all for the nice info

i'll re-re and re read linkwitz' site and look for distortion info!!!


line arrays ...
about using multiple drivers to do the same job as a single driver would

in what magnitude does using 2 drivers instead of 1 to get the same SPL at the same distance, reduces the distortion ?
and wich type of distortion does it affect ?
then 4? 8 ?


how does a 200$ Seas unit compare in distortion to a similar 20$ TB unit ? is their a significant difference in distortion ?

what about using 2 drivers in push/pull with inverted phase side by side a la "W" sub frame ? i read that it cancels mechanical distortion ? can we use this for higher freq. drivers?

does it work for more than 2 units?

[audio-kraut]

Why don't you check Solen website. They give you the info you need - if you trust the manufacturers measurements.

[David Gatti]

Remember that harmonic distortion < 1% is inaudible (ref Martin Colloms - High Performance Loudspeakers), so numbers like .001% distortion in amps is academic. Cone area, horn loading and a good magnetic system are the most effective way to keep distortion below the threshold of audibility.


www.gattiweb.com

[wimms]

super-cheap copy of the Orion

Super-cheap? Wow, I want to hear about that.

Re speaker distortion, afaik you need to have cones always operating in pistonic region, avoiding cone breakup like plague. The reality is compromises.

Very nice site: http://www.lenardaudio.com/education/05_speakers.html

[synergy]

best of a bad job i reckon and we've just got to live with it to some degree

the way i see it you've got a compound effect of distortion from the microphone in recording to the speaker in playback

any distortion in one bit of kit is just going to get multiplied by the next thing in the chain and so yes the lower your amps THD the better

if all the kit has less than 0.01 THD before it meets the 2% of speakers you're still only going to be around 2% THD in total

stop worrying about what comes before and it all starts going horribly wrong

dave