TB 1337SA Fs way off?

[littlesaint]

I ordered a couple of drivers from PE to test with the WooferTester3. It appears to be getting good marks for speed and accuracy. One of the drivers is the TB 1337SA. Its listed Fs is 70Hz, and John Krutke tested it at around 85Hz. On the WT3 mine came in at 105Hz??? The other T/S parameters where way off as well.

I know it's not the WT3 because the other drivers I tested (various Dayton RS) were very close to the published Fs. Could I have a bad driver or is that much variance common?

[Dennis H]

Try running it at 1/2 Xmax with a 20 Hz tone for a while and retest.

[MuaDibb]

I found the same thing. I recently won a WT3 and measured all the drivers I had, the Fs came in about 5hz higher than published specs on all of the drivers I tested, some broken in some not. The exception was a new W4-1337SA, which tested at 100Hz. I recently built the D4 from Jed's Lineup series, very nice speaker and the driver is wonderful, but it got me wondering. I pulled both drivers and while they hadn't had a lot of playtime they weren't fresh either, one measured at 90Hz and the other came in at 91Hz. The impedence graphs match up, the other T/S parameters are close enough that you could say its normal variation in a run. I've always assumed the published specs were an average of several speakers, maybe not though. Anyway I've been scratching my head over that one.

[Jed]

Looks like it is getting tougher and tougher for manufacturer's to maintain their specs. Note my Vifa D26 Consistency thread as well.

[littlesaint]

Well, I ran a 20Hz sine wave and some pink noise through the driver, and Fs is down to 95Hz. Better, but still not as low as I was expecting. I don't think it will adversely affect the design I was planning on, but it makes me wonder about the QC of these drivers.

[Jed]

I think I'd be more concerned with FR or distortion anomilies. I've measured about 10 of them and they're pretty close. Since you have the capability to measure, you can take the best ones and send anything "questionable" back to PE for free. That's the beauty of their 45 day satisfaction gaurantee.

Jed

[TacoD]

Looks like it is getting tougher and tougher for manufacturer's to maintain their specs. Note my Vifa D26 Consistency thread as well.

Spend some extra money and you will get consistence specs, Visaton TI 100 for example. And as far as I know the Seas woofers are also very consistent.

[Jed]

Spend some extra money and you will get consistence specs, Visaton TI 100 for example. And as far as I know the Seas woofers are also very consistent.

Yeah sometimes you get what you pay for but not always.

[TacoD]

Yeah sometimes you get what you pay for but not always.

That's the reason I did not mention Accuton

[Jed]

That's the reason I did not mention Accuton

:rofl:

Although I haven't found a lower distortion mid than my C79s..........yet. And they have a nice FR. I guess I got lucky.

Jed

[jkrutke]

I found the 4" Ti TB's to be a little more sensitive to breakin than a normal speaker. It's likely something to do with the ratio of cone weight to spider size and stiffness though I'm only speculating. The breakin on the attached impedance was 2 hours of 15 Hz at full Xmax with 1/2 hour cool down time. Fs went from 100 to 83 Hz. This is the 3rd and 4th sample I've tested and they've all been relatively close.

[Jed]

Thanks for clearing that up, John.