Added mass route should be fine. Remember, of all the t/s parameters, Vas can have the widest variation in value before changes in the response curve become significant. Why I like the delta compliance method better is because it pushes Fb UP, and the higher it is, the easier it is to measure accurately.
I weighed everything today. The driver weighs 25 lbs. The cabinet weighs 55 lbs. Finished it should be a tick over 80lbs.
I will measure the vas of the 385 tonight using the added mass method.
How much weight should I add to the cone? I was thinking of using the method at the 4:00 minute mark on the PE instruction video. https://www.youtube.com/watch?v=dARRX-tZpg4
Also, How should I be measuring the piston diameter on this driver? The video shows a foam surround and the guy measures from the apex of the surround. Do I just measure from the middle of the ribs on the paper surround on the pa385?
How much weight should I add to the cone? I was thinking of using the method at the 4:00 minute mark on the PE instruction video. https://www.youtube.com/watch?v=dARRX-tZpg4
Also, How should I be measuring the piston diameter on this driver? The video shows a foam surround and the guy measures from the apex of the surround. Do I just measure from the middle of the ribs on the paper surround on the pa385?
OK, I think I have found the answer. The piston diameter will be measured from the middle of the surround to middle of surround and the weight added should be between 60% and 100% of mms of the driver.
Does this sound correct?
OK, the middle rib on surround measured out at 13" diameter. I measured vas using 3 different weights and recieved the following.
160g
232g
185g
And here are the parameters entered. Things don't look too good.
160g
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232g
An externally hosted image should be here but it was not working when we last tested it.
185g
An externally hosted image should be here but it was not working when we last tested it.
And here are the parameters entered. Things don't look too good.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Oh well 🙁.
I guess at this point it's time to measure and see if the frequency response is closer to the original sim or to the adjusted one.
I guess at this point it's time to measure and see if the frequency response is closer to the original sim or to the adjusted one.
Ya I was thinking the same thing. Unfortunately I won't be able to measure outside until spring.
I don't know if it would be worth redesigning the box with the parameters I measured. I would like to build 4 boxes but would hate to receive 4 drivers with specs that are all out of whack.
I am leaning towards 4 SS15s after seeing what I see here.
Yep. That concern is why I usually design my boxes after measuring the drivers. I'd also take the issue up with PE if the parameters are way off the published ones as appears to be the case here.
You could do a "close-miked" in-house measurement to get an idea of what to expect. Put the box in the center of the room, the mike about a foot or less away from the mouth, run a measurement at low drive level. Turn the box so the driver is facing down for the measurement, which should bring the mouth closer to the floor.
No worries, it was a good learning experience. Now that I have the tools I will do this in the future. I will talk to PE and see what they want to do.
I will have to check what the 15tbx100 sims in the box I built when I get back home just for kicks.
Thanks again.
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Neat project!
Before you give up on that driver, how cold was it when you measured it? Were you anywhere near room temperature, or was it sitting out in an unheated shop?
I've had cold drivers measure VASTLY different than they do when warm.
Still, with that much difference in BL, I'd take things up with PE, seems like the motor force is far weaker than it should be. Your driver is 30% (10 units) low.
I would say it was around 55 deg F in the room when I tested. Don't worry, I'm not going to throw the towel in quite yet. I will talk with PE tomorrow and see what they say. Thanks for the advice.
Once again. Great info! Very curious what PE does... After all they are selling the tool that we use to check this stuff.
Valid concerns, but those conditions would also change Fs, and the measured Fs is almost identical to the value published by PE.
The measured specs for the Dayton PA310 are a good match for the published ones. Except for Le, which checks in at a lower value than published.
probably true, however, they like to "change the specs" after about a year of release (dayton pa 465 for instance that gained almost 20 points on qes).
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