I recently got a DATS V3 and tested a number of drivers I had. I use to use Speaker Workshop and a Wallin Jig. The results were reasonable to published specs. I just received a used pair of Peerless 830870's, a 4" poly cone in their HDS series. When I tested them, key parameters, such as Fs and Qts were considerably out of spec. Example, Fs spec is 91Hz and measured was 129Hz. I consider 10% reasonable and and consistant with other Peerless models I've tested. It does look like Peerless claims 15% on Fs for this model, but still considerably off from that.
I've also had good luck with measuring Peerless drivers with the added weight method for Vas. The inverted dust cone helps there. I have been using 30g for smallish woofers and 45g for larger. When I try to test these drivers, the test fails because Fs didn't change enough. I tried 30g, 45g, and 75g. This has me concerned there might be some damage to them. BTW, both drivers test very close to each other.
The drivers are used, and see signs of being mounted, so do not suspect they would need break-in. Now, the drivers were shipped, face down against a styrofoam board, compressing the surround. I suspect that this might be the issue and will let them set for a few days, and running tests on each to see if they improve. Is there a test signal that would accellerate this process?
Le and Re measure close to spec, so don't think the voice coil is shorting out. They also pass the "rub and buzz" test.
Any thoughts and what may be causing these issues?
I've also had good luck with measuring Peerless drivers with the added weight method for Vas. The inverted dust cone helps there. I have been using 30g for smallish woofers and 45g for larger. When I try to test these drivers, the test fails because Fs didn't change enough. I tried 30g, 45g, and 75g. This has me concerned there might be some damage to them. BTW, both drivers test very close to each other.
The drivers are used, and see signs of being mounted, so do not suspect they would need break-in. Now, the drivers were shipped, face down against a styrofoam board, compressing the surround. I suspect that this might be the issue and will let them set for a few days, and running tests on each to see if they improve. Is there a test signal that would accellerate this process?
Le and Re measure close to spec, so don't think the voice coil is shorting out. They also pass the "rub and buzz" test.
Any thoughts and what may be causing these issues?
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They appear to be just as flexible as my other rubber surround Peerless woofers, which are definitly older. These do appear to have a serial number on them, but don't know how to decode. GF10AP0473 and GF10AP0476 Maybe "10" = 2010???
I just happened to read about this over the weekend because I had some new drivers measuring quite different than I expected.
The advice was (1) start with an added mass of about 50% manufacturer's stated Mms and then (2) increase mass until Fs drops 25% from your free air measurement. This will give you the most accurate message of Vas (according to what I read).
This worked well for me and I did not end up needing to send them back.
Note, this suggests you should be starting with 3g for those 4 inch drivers.
The advice was (1) start with an added mass of about 50% manufacturer's stated Mms and then (2) increase mass until Fs drops 25% from your free air measurement. This will give you the most accurate message of Vas (according to what I read).
This worked well for me and I did not end up needing to send them back.
Note, this suggests you should be starting with 3g for those 4 inch drivers.
Thx. I didn't know it could be too heavy. When I've gotten the error before, it was because Fs did not move low enough. I tested with 5g, 10g, and 15g, and they all passed the test. The results varied, but will look at that a little closer now.
Well, that answers the Vas problem. But the Qts and Fs are still out. I also recalibrateded the referance resistor and the leads. Lead resistance decreased slightly, but didn't change the Vas/Qts much. Hopefully the surrounds recover and I see some change in tommarows tests.
Well, that answers the Vas problem. But the Qts and Fs are still out. I also recalibrateded the referance resistor and the leads. Lead resistance decreased slightly, but didn't change the Vas/Qts much. Hopefully the surrounds recover and I see some change in tommarows tests.