Help with Seas w15cy001 T/S parameters

[jarkaa]

Hello,

Has anyone measured T/S parameters for W15CY woofer.

I did measurements with SWand ended up with really weird results compared to published specs.

Here are my measurements

Vas:9,0
Qts: 0,49
Fs: 48Hz

The datasheet says:

Vas: 13,5
Qts: 0,36
Fs: 37Hz

Can anyone tell about their own specs?

[simon5]

Did you break-in the driver enough?

[jarkaa]

I broke the drivers in for about 15 hours before the testing.

I am surprised that the specs are so different from the datasheet.

Or maybe my testbench needs modifying...

[simon5]

Maybe try another 15 hours at higher volume levels, and see how much it changed. You'll know if they are breaked in enough.

The specs are way off, I agree with you hehe!

I can't help you much about Vas, but are you using these methods for Fs and Qts?

http://www.diysubwoofers.org/measure.htm

[bidland]

The problem with most T/S measurements is that you have to keep the signal level low to get an accurate measurement. The driver must be operated within its linear range.

This will get you accurate measurements of force actor and moving mass, but it will not be a realistic measurement of the resonance frequency. Suspension compliance varies with excursion and the effect on the measured resonance frequency measured at 0.1V and 2V is substantial.

Seas believes that the resonance frequency published in the datasheet should be measured at a drive level that is closer to normal listening levels. The resonance frequency is measured with 2volts at the driver terminals.

It's our experience that this gives us much better correlation between simulated low-frequency response based on T/S-parameters and frequency response measurements at normal listening levels.

Seas is now in the process of updating all datasheets and T/S-parameters measured with the Klippel LPM module. Very accurate voltage and current sensors together with laser measurement of cone movement gives us a precise set of parameters.

I hope this can explain the different measurement results, and that you will find our datasheets useful in the future.


regards,
Bjorn Magne Idland
Lab tech.
Seas Fabrikker AS

[simon5]

Thank you very much for your imput, it's fun to have the manufacturer reply to a topic like this.

The method I posted above use 1.0 V at the amplifier output, I guess it will be closer to your posted T/S specs.

[jarkaa]

Björn, thanks for your input.

I will make a test cabinet according to Seas datasheet and see how it measures.

Also big thanks to Seas for their excellent service in providing discontinued drivers datasheets. It is some three years ago I mailed to Seas and asked for old P17rc4 specs and it took only a week to recieve the datasheet on a paper via mail.

Keep up the good work

Jarno

[ojamio]

Bjorn, could you take a minute and post specs for the seas p17rc4. I.m considering a purchase from zalytron
Thanks, Orlando

[bidland]

I could not find the datasheet for this driver, but I have done a calculation that should bring you quite close.

I used the parameters from H425-08 P17RC4Y, which has a bigger magnet, and reduced the BL a bit.

H424-08 R17RC4

Rdc: 5.7 ohm
Fs: 31Hz
Mms: 15.5g
BL: 8 N/A (estimated)
Qms: 1.1
Qes: 0.27
Qts: 0.22
Vas: 40 litres
Sd: 130 sq.cm

Hope this helps.

Bjorn Magne

[jomor]

It has been reported that measuring T/S parameters often give quite different results than the manufacturer's specs, but the weird thing is that both the measured and manufacturer's parameters give an almost the same box when simulating !