I think you should measure again with the "Test Box" or "Added Mass" method.
I'm not quite sure how the "Specified SPL" or "Specified M (md)" method works and where your data comes from for it. It is possible that incorrect information can significantly falsify the result.
However, this should only apply to VAS and Mms ...
With the measured TSP, this chassis is quite a scrap
I'm not quite sure how the "Specified SPL" or "Specified M (md)" method works and where your data comes from for it. It is possible that incorrect information can significantly falsify the result.
However, this should only apply to VAS and Mms ...
With the measured TSP, this chassis is quite a scrap
Hello collective intelligence....I info for mmd and effective piston diameter given to me from John...Since then I've exercised the woofers enough to get fs within tolerance....the new readings are what you see...
The adats is now calculating a vas, sd, fs, mms, in acceptable range...
When I get home Ill try "test box" method, it did not work before with fb being too close to fs...it gave an error...I could try specified spl method now the fs has settled in...added mass method may/may not work since the weight cannot be centered due to phase plug in the middle...
My only concern is if my money will be returned (or driver replacement) if the driver truly turns out to be faulty.
I might as well start analyzing the 18H+'s =(
The adats is now calculating a vas, sd, fs, mms, in acceptable range...
When I get home Ill try "test box" method, it did not work before with fb being too close to fs...it gave an error...I could try specified spl method now the fs has settled in...added mass method may/may not work since the weight cannot be centered due to phase plug in the middle...
My only concern is if my money will be returned (or driver replacement) if the driver truly turns out to be faulty.
I might as well start analyzing the 18H+'s =(
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They do...the little bumps in the impedance chart supposedly shouldnt be there...those characteristics are indentical in both drivers as well. Can someone shed some light on that please… Are the curves of the impedance plot supposed to be smooth?
3 days, no words from AE...
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I have always preferred the added mass method - use a ring of clay.
Peaks mean resonances and there should only be one. The others look very sharp, high Q, meaning a low mass most likely. Something loose, like the coil leads.
Instead of clay you can also use small ferrite magnets on the front and backside of the cone,
so the small magnets attract each other through the cone.
I used 4 ferrite magnets of about 5-10g each, depending on the cone size.
Use the not so strong ferrite magnets, because those are easy to remove without damaging the cone,
additional you can also pust some fabric between the magnets and the cone.
so the small magnets attract each other through the cone.
I used 4 ferrite magnets of about 5-10g each, depending on the cone size.
Use the not so strong ferrite magnets, because those are easy to remove without damaging the cone,
additional you can also pust some fabric between the magnets and the cone.
It's almost as if the wrong suspension parts or VC were used.
Qes and Qms are way off spec. Deviations of 10-20% are normal, but here it's 50% and (much) more.
Ro808 - Did you see the last specifications show since a break in attempt? Now that FS is where it should be a lot more specs lineup… But there are still other important specs that aren't lining up... QTS and motor strength in particular, are of concern.... this is all aside from the mysterious character of the impedance plot.
I'm going to grab some putty from the store and post some more information tonight
Thank you all for your timely consultation... this really is just as much your project as it is mine… And I truly appreciate you all.
I'm going to grab some putty from the store and post some more information tonight
Thank you all for your timely consultation... this really is just as much your project as it is mine… And I truly appreciate you all.
Assuming a mass number is very suspect IMO. Find the mass from the Delta-mass resonance shift and use that number. If the BL is still low then it has to be B unless the wrong coil was used.
Bl / Re is the universal measure of motor strength. This number should be the same for both 8 ohm and 16 ohm coils. You can also check that from John's specs.
Bl / Re is the universal measure of motor strength. This number should be the same for both 8 ohm and 16 ohm coils. You can also check that from John's specs.
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I was taught Bl²/Re to compare motor strengths between drivers with different Re.
TD15m Bl²/Re
4 ohm 43.58
8 ohm 43.78
camplo 16 ohm 18.89?!?!?
3 options here as I see them:
1. The B is wrong. This means it wasn't charged fully. Unlikely me thinks.
2. The L is wrong. Very possible. This is a tricky thing to balance. Take the same motor. Putting in different coils, with different Re, that all have the same number of turns in the magnetic gap is a real balancing act. Many speakers that offer different Re specs will also use a different motor, having a different magnetic gap size, for each of the Re speced drivers.
3. camplos measurements are wrong. Possible but seeming less likely than option 2. Will be interesting to see results from added mass T/S extraction.
TD15m Bl²/Re
4 ohm 43.58
8 ohm 43.78
camplo 16 ohm 18.89?!?!?
3 options here as I see them:
1. The B is wrong. This means it wasn't charged fully. Unlikely me thinks.
2. The L is wrong. Very possible. This is a tricky thing to balance. Take the same motor. Putting in different coils, with different Re, that all have the same number of turns in the magnetic gap is a real balancing act. Many speakers that offer different Re specs will also use a different motor, having a different magnetic gap size, for each of the Re speced drivers.
3. camplos measurements are wrong. Possible but seeming less likely than option 2. Will be interesting to see results from added mass T/S extraction.
Unless you are the speakers manufacturer in which case it becomes trivial to simply weigh the moving parts. We don't know if camplo was provided measured-on-a-scale weight or not. If not then you are so very right. You can never, in that case, assume mass.
Qms is halfway there, but Qes is still 2.65 times higher than specified, which is unacceptable considering the price of the TD15M. Perhaps the test method is sub-optimal?
Here are the specified and measured parameters of some mass-produced 15" woofers for illustration:
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