Test tones for listening tests

[loninappleton]

I have some test tones which were downloaded from an mp3 source.

The thing I noticed in the lower and lowest freq tests was:

1.) lots of Xmax activity by the driver itself

2.) some tone change as the sound played. The only analog I can think of is a transmission change in a car like the speaker was 'warming up' and changing pitch without changing the frequency on the player setting.


I cannot ascribe it to my hearing. It seems to be a mechanical thing.

[jnb]

Is it a multiple test tone?

I haven't used an mp3 tone but I wouldn't. Have you tried noise based testing... Arta, for example?

[loninappleton]

Is this a digital source?

I was just using free stuff and do not have things like a scope and tone generation equipment.

[jnb]

I hope there's no misunderstanding. Arta (computer program) will generate its own test tones. All you need is a mic.

[loninappleton]

Ok, I know a bit about this sort of software but not much.

Maybe some day I will be able to do testing. I thing audiorountable had some info on this but I don't really know where the how to would be covered.

[hermanv]

IMHO Test tones are valuable for measuring frequency response, impedance maybe 2nds and 3rds, but utterly worthless for listening tests.

At a loud enough levels, sine wave tones will heat voice coils or crossover components in a way that music never will. So the sound changes over time as things get hot.

[Richard Ellis]

Test tones can test for enclosure integrity...some years ago a buddy of mine who was in the DJ business neede his speakers rebuilt,,,we changed drivers for a more balanced (Accurate) response & made a new enclosure. We did an A-B test at thirty hertz with the old against the new...the old set was merely vibrating the enclosure to death complete with air-leaks, resonances, and harmonics.
The old set would not propagate the low frequency,,,the new one on the otherhand set the windows in motion quite well.
____________________________________Rick..........

[happy.gringo]

Was the speaker you tested a fullrange? I have heard similar "transmission changes" when I played with a 2 way crossover, which I assumed were phase problems, but I really don't know. I use this freeware signal generator and it did help alot in setting the tweeter level:
http://www.natch.co.uk/downloads/SigJenny/SigJenny.html

[loninappleton]

Nope just single FE127e.


The test tones gave so much excusion I thought the
surround was going to fly off.


The sound is sort of like a balloon being flapped by a bicycle wheel.

I have another test going today with less batting inside and covering just 2 walls.

[hermanv]

Originally posted by loninappleton
<snip>
The test tones gave so much excursion I thought the
surround was going to fly off.

The sound is sort of like a balloon being flapped by a bicycle wheel.

I have another test going today with less batting inside and covering just 2 walls.

In most enclosure designs the air in the chamber acts as a spring against the cone. In a ported design, the enclosure spring disappears below the port resonance frequency. At or below this frequency the woofer cone is un-damped, causing it to flop about kind of like a balloon being flapped by a bicycle wheel.

Don't test woofers blow their cutoff point, it provides no information and can damage the woofer. Do not operate woofers beyond the Xmax rating, either by too low a frequency or too high a drive level.