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Thiele & Small Parameters
Thiele & Small Parameters (after 24hrs Break-in)
It’s not often I pay $240 for a woofer but after being hugely impressed with the Scanspeak 15WU/4741T00 Illuminator, I decided it was time I test out their much acclaimed 7″ Revelator, the 18W/4531G00. To my utter horror, my DATS measurements are totally different from Scanspeak’s specs (see above). And this is after 24hrs of breaking-in.
Out of concern, I contacted Madisound about this discrepancy but their Customer Service personnel by the name of Brian was less than helpful. Instead of addressing my concerns, he in fact implied that I do not know how to measure the Thiele & Small. Even tried to gaslight me by saying:
“Berger, a beloved engineer at Scan-speak, was aware of the problem and was designing a program to unify the different measurement types, but unfortunately he passed away before finishing it. We have actually gone through this many times ourselves. People would send back drivers they measured on milli-volt systems saying they were out of spec. We would burn them in and measure with Audio Precision to find they were very close to the factory specs. Many of those drivers were Scan-speak, so they are ones that show a pretty large difference.”
That’s a load of BULL-SHIT if ever there was one. I made it clear that Thiele & Small measurements are small signal. One obviously need to use a large signal for breaking the woofer in but when it comes to measuring Thiele & Small, it’s small signal.
Just for the record, I have DATS as well as the industry’s standard, LMS by Linear-X. And if that is not enough, I also have Audio Precision. I would like to know what Scanspeak and this Madisound clown did to magically reduce a Qts from 0.7 to 0.35.
Here’s a Scanspeak PL18WO-06-08 which I own. Notice how close the T/S from Scanspeak and my DATS measurements are. In fact, they are almost identical. Both Qts are at 0.34. And this is from the same company – Scanspeak.
Scanspeak Thiele & Small Parameters
Thiele & Small Parameters with DATS
Using Wavecor’s datasheet as a guide, there’s only a 15% difference between a woofer that’s not broken in compared to one that’s broken in. Note the Qts before break-in is 0.29. After breaking in, Qts is 0.25.
Wavecor WF182BD03 Thiele & Small Parameters
In my DATS measurements, my Qts before breaking in is at 0.33. When I apply a 15% difference for breaking-in, my Qts will be at 0.29. This is acceptable as it is very close to 0.25.
Wavecor WF182BD03 Thiele & Small Parameters (before Break-in)
If I am to apply a 15% reduction as in Wavecor’s datasheet, my Revelator’s Qts of 0.7 will be 0.595. That is still far off from their Qts of 0.35. Looking at this from Scanspeaks perspective, a Qts of 0.35 to 0.7 is a 100% difference. I can accept a 15% to 25% deviation but 100% is clearly off specs.
As a final note, do not blindly accept that the manufacturer’s Thiele and Small Parameters are the gospel truth. If your DATS or any recognized measuring system records a vastly different parameters, there’s a good chance your woofer is not to specs. My advice is to Return it. If the seller refuses to refund your purchase, send me your woofer and I’ll test it for you. If it is still out of specs, I will compile a list of all these rubbish woofers that are sold to the public. Better still, buy from Parts Express. At least they are honest. |
