Peerless 830657 for <$6a piece!

[donradick]

I found the same Don, a port tuned in the 60-80hz range performed best, tuning of 40hz required a massive box to make it work, like over 28l per driver minimum, more like double that. I don't see 4 of these things outperforming 2 decent 8" in a smaller enclosure for example 2 RS225 in 60l ported puts out a lot of nice bass to 30hz. But these things are cheap. Javad

You are correct, thinking only of bass output, but the goals for this build are orchestral dynamics with effortless, clean output and decent bass.
May need or want a sub to fill out the bottom. We'll see. It all depends on the exact T/S params.

[JavadS]

You are correct, thinking only of bass output, but the goals for this build are orchestral dynamics with effortless, clean output and decent bass. May need or want a sub to fill out the bottom. We'll see. It all depends on the exact T/S params.

Absolutely, 100hz and up there are no issues, these drivers definitely benefit from a sub.

[donradick]

Got my case on Tuesday, and starting burning a couple.
Here's the first one - matches the T/S on Amazon pretty closely.
Re was a surprise, but I measured it twice with my trusty Fluke DMM.

Thiele-Small parameters:

Fs = 50.50 Hz
Re = 8.00 ohms[dc]
Le = 289.34 uH
L2 = 775.40 uH
R2 = 18.16 ohms
Qt = 0.60
Qes = 0.75
Qms = 3.01
Mms = 13.27 grams
Rms = 1.399124 kg/s
Cms = 0.000749 m/N
Vas = 20.91 liters
Sd= 141.03 cm^2
Bl = 6.698577 Tm
ETA = 0.34 %
Lp(2.83V/1m) = 87.48 dB

Added Mass Method:
Added mass = 10.00 grams
Diameter= 13.40 cm

Figured out Xmax independently - its:

voice coil length - magnetic gap length / 2

For these, that's 13mm - 6mm / 2 = 3.5 mm (which matches PE's published spec for the 830657)

My drivers were labeled: FSBA25065-0801

[dankwijoti]

Thanks for the measurements, Don! I'm psyched to see that the vas is actually lower than the spec sheets suggested. The higher Re is weird, but I'm glad to see that yours read high too. I thought my DMM was junk when I read 7.9. Sensitivity looks good despite the Re, so nbd, really. Especially since I think we are all planning on cramming multiples of these in whatever we end up making.

[Chris Roemer]

The MUCH higher Qts value swamps any box size gains from the lower Vas, but it also lowers your in-box F3.

[kenny_k]

I picked up 4 and did a little DATS action:

[donradick]

I picked up 4 and did a little DATS action:

Wow, that's a LOT of variation!
did you break them in? I've tested 1, Fs was 57 at first, after burn in it was 50.5 Hz.

My Re was way too high because my meter needed a new battery.

[kenny_k]

No brake in, just had time for a quick measure. So little time, so much to do.

[Millstonemike]

Wow, that's a LOT of variation!

Maybe from the mfg's bin that didn't pass QC ...

[donradick]

Maybe from the mfg's bin that didn't pass QC ...

Probably the truth! I'll know soon enough, I burned in qty 4 for a few hours. On to the next one

[dankwijoti]

Probably the truth! I'll know soon enough, I burned in qty 4 for a few hours. On to the next one

The drumroll is killing me. What's the verdict Don?

[donradick]

OK, Theile/Small parameter tests completed on all 12 drivers.
Summary: consistency, consistency, consistency (or lack thereof)

LIMP used for all calculations, I had some inconsistencies at the start, but that was due to a failing battery in my Fluke DMM.
I"d suspect my process, but the results seem pretty consistent for the couple of retests I've done.

Regardless, I'm inclined to go forward with the project, and use averages for the simulations.
Anyone have a better idea?

Graphs are the most informative.

Fs - not too bad, #2 and #6 are the outliers.



QTS - about the same as Fs - #2 and #6 are off.





VAS - yikes! All over the place.:



MMS - really, should not have this much variation!

[dankwijoti]

Wow, thanks Don. Those measurements are... surprising. How in the world could there be <%100 variation in MMS? I mean, I don't doubt it has happened, as I can see the inverse relationship to the measured VAS, but what sloppy manufacturing processes are causing it? I wonder if it is variation in the amount of the cone coating, or maybe globs of glue under the dust cap. Also, I'm kind of surprised that the higher mass isn't bringing down the Fs of #1, 7, & 8. Strangeness.
Anyway, yeah, taking the mean of the measurements is the only way I can think of to handle the calculations. Having your drivers measured and numbered allows you to manipulate driver selection for your own build to ensure that things more or less average out. Put 3 high MMS/low VAS and 3 low MMS/high VAS drivers per side.

[donradick]

Wow, thanks Don. Those measurements are... surprising. How in the world could there be <%100 variation in MMS? I mean, I don't doubt it has happened, as I can see the inverse relationship to the measured VAS, but what sloppy manufacturing processes are causing it? I wonder if it is variation in the amount of the cone coating, or maybe globs of glue under the dust cap. Also, I'm kind of surprised that the higher mass isn't bringing down the Fs of #1, 7, & 8. Strangeness.
Anyway, yeah, taking the mean of the measurements is the only way I can think of to handle the calculations. Having your drivers measured and numbered allows you to manipulate driver selection for your own build to ensure that things more or less average out. Put 3 high MMS/low VAS and 3 low MMS/high VAS drivers per side.

Good idea to balance the "outliers" L and R.
You know, I attached 2 US nickels for a total of 10 grams, and used some blue painter's tape and put them in the center
of the cone. Now that I think about it, maybe I should have used some Blu-Tac to attach them.
Ok, I'm going to do that and retest each of them ;-)
Gotta be truthful - I looked at the Uluwatu's from Curt Campbell recently and felt that perhaps I should build those.
But I'm going to wait on the results of a retest of these drivers.

BTW, you've shown the most interest in this. Did you buy a case also?

[johnnyrichards]

Years ago, some told me Fs shouldn't change with the addition of a bucking magnet, so when I added a bucker and Fs changed I was curious.

Now, I know more than that and understand that if Fs was tied solely to MMS, it would never ever change under any circumstance. Fs generally comes down during a physical break-in process, unless it is adding mass during that process, soft part variance and even differences in Bl are probably influential in the complex Fs parameter.