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radulescu_paul_mircea

New SVS Ultra 16"

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I went back and looked at the Tymphany STW-350F specs and they are totally different from the specs that ITR posted from a PB16 driver. Originally I thought that these drivers would be quite similar or were at least using a similar build platform. After looking again there is very little similar between them at all. The frames are different, the STW-350 is 15" OD but the SVS appears to be 16" OD. The STW-350 is using an overhung topology with a 7.4" diameter coil. SVS says they are using an underhung 8" nominal diameter. That being the case both the surrounds and spiders would be different. The overall motor / gap / coil geometry would be much different as well. In fact it seems like perhaps the only parts shared would maybe be the motor case and backplate. Although the motor outwardly makes the drivers seem like close brothers it appears that they are more like estranged 3rd cousins.

Modeling the 2 drivers using the parameters provided shows that they behave as differently as you would expect.

The SB16 driver should be a completely different 3rd driver design.

I must say this has gotten me interested in testing the SVS 16's again.

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On 11/6/2017 at 3:51 AM, ITR said:

Sorry, I am little late to the party. Could you please point me to the newer thread, I could not find it.

I did not mean that high moving mass would always be an indicative of high inductance, I was just replying to his question.

T/S parameters below.

Electrical Parameters            
Re    4.65    Ohm    electrical voice coil resistance at DC
Le    3.143    mH    frequency independent part of voice coil inductance
L2    8.938    mH    para-inductance of voice coil
R2    16.81    Ohm    electrical resistance due to eddy current losses
Cmes    898.19    µF    electrical capacitance representing moving mass
Lces    21.56    mH    electrical inductance representing driver compliance
Res    51.10    Ohm    resistance due to mechanical losses
fs    36.2    Hz    driver resonance frequency 
            
Mechanical Parameters            
(using laser)            
Mms    491.600    g    mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd)    464.350    g    mechanical mass of voice coil and diaphragm without air load  
Rms    10.711    kg/s    mechanical resistance of  total-driver losses
Cms    0.039    mm/N    mechanical compliance of driver suspension
Kms    25.38    N/mm    mechanical stiffness of driver suspension
Bl    23.395    N/A    force factor (Bl product)
Lambda s    0.045        suspension creep factor
            
Loss factors            
Qtp    0.911        total Q-factor considering all losses
Qms    10.428        mechanical Q-factor of driver in free air considering Rms only
Qes    0.949        electrical Q-factor of driver in free air considering Re only
Qts    0.870        total Q-factor considering Re and Rms only
            
Other Parameters            
Vas    38.8458    l    equivalent air volume of suspension 
n0    0.186    %    reference efficiency (2 pi-radiation using Re) 
Lm    84.90    dB    characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom    86.00    dB    nominal sensitivity (SPL at 1m for 1W @ Zn)
            
Series resistor    0.00    Ohm    resistance of series resistor
Sd    834.69    cm²    diaphragm area

 

Thanks for posting the complete T/S's (unlike what was available a year ago when I posted and you quoted me). Super stiff driver. But since you mentioned using a lazer for measurements, what is the actual Xmax (70% BL, 82% BL, etc), Xmech, Xsus? One-way figures of course. It's good to see someone with Klippel openly publishing the information on this driver. Thanks again. :)

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10 hours ago, Electrodynamic said:

Thanks for posting the complete T/S's (unlike what was available a year ago when I posted and you quoted me). Super stiff driver. But since you mentioned using a lazer for measurements, what is the actual Xmax (70% BL, 82% BL, etc), Xmech, Xsus? One-way figures of course. It's good to see someone with Klippel openly publishing the information on this driver. Thanks again. :)

Here you go. My 3 kW amplifier could not push it further than +/- 15 mm (~210 V peaks) so you don't actually see where the 70% limits are, but one can have a pretty good estimate.

SVS PB16-U Kippel.png

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4 hours ago, ITR said:

Here you go. My 3 kW amplifier could not push it further than +/- 15 mm (~210 V peaks) so you don't actually see where the 70% limits are, but one can have a pretty good estimate.

Looks like it is time to try that K20 out on the next big woofer across the bench. ;)

Judging by the slope of those curves it looks like the 70% BL point is going to be around 20mm.

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I should amend my critique to add that keeping cost low is likely a factor that went into the optimization.  We DIYers often take for granted that actual parts cost is typically a much smaller percentage of the finished product cost in a retail offering than a DIY build.

5 hours ago, ITR said:

Here you go. My 3 kW amplifier could not push it further than +/- 15 mm (~210 V peaks) so you don't actually see where the 70% limits are, but one can have a pretty good estimate.

I don't know a whole lot about how Klippel testing works, but the amp should be able to achieve more excursion at Fs than below because of Qtc > 0.707.  This may actually suit the SVS design well if the amp is unable to achieve its "peak" power rating for any useful length of time at Fs, even despite the impedance peak.  The high Qtc would provide an extra boost where the amp can't quite "get there", but the amp would be able to go full tilt into higher frequencies where the mass and inductance really hold it back.

The Klippel's look real nice as far as allowing lots of excursion with low THD.  It'll probably look great in a standard measurement suite including CEA.  However, the inductance variance seems pretty high to me.  Maybe it's fine for a budget consumer sub.  Still, I'd bet that it sounds a lot better, the lower the crossover point is.

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10 hours ago, ITR said:

Here you go. My 3 kW amplifier could not push it further than +/- 15 mm (~210 V peaks) so you don't actually see where the 70% limits are, but one can have a pretty good estimate.

SVS PB16-U Kippel.png

I had a feeling the driver was more linear than the 10 mm spec that someone on another forum eluded to. IIRC SVS mentions 20 mm Xmax (one-way) but it's nice to see the graphs. Pretty linear BL on the driver too. Big pat on the back for the shape of the curve. Thanks for showing us the curves. All of them are nice and symmetrical (which is actually more important than shooting for a high number irregardless of the shape of the curve). :D 

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14 hours ago, Electrodynamic said:

I had a feeling the driver was more linear than the 10 mm spec that someone on another forum eluded to. IIRC SVS mentions 20 mm Xmax (one-way) but it's nice to see the graphs. Pretty linear BL on the driver too. Big pat on the back for the shape of the curve. Thanks for showing us the curves. All of them are nice and symmetrical (which is actually more important than shooting for a high number irregardless of the shape of the curve). :D 

The numbers currently on the PB16's page are 95mm peak to peak Xmech and 82mm Xmax:

Snap.png.ec873864e83681ce49a60f797f4bc25d.png

 

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