20 drivers were measured so far and their numbers are all very close to each other (Colin was right!), so I have decided that I will not measure any more of them (it really is time consuming) and will start sending them out. Sorry for the wait!
Here are the average values of the T/S parameters for the 20 drivers that were measured:
DCR 5.2 ohms
Fs 58.6107 Hz
Qms 1.0726
Qes 0.3645
Qts 0.2720
Vas 10.2355 L
Here are the average values of the T/S parameters for the 20 drivers that were measured:
DCR 5.2 ohms
Fs 58.6107 Hz
Qms 1.0726
Qes 0.3645
Qts 0.2720
Vas 10.2355 L
Well,it was a nice idea, but it sounds like a bit of a grueling task. I think it will be fine just shipping them as they come to hand.
Dang.
Dang.
Interesting figures - I wonder how much break in alters them or whether there has been a change in manufacture.
I don't think break in will alter them that much and I don't think there has been a change in manufacturing either. The method that was used to measure and calculate the T/S parameters always seems to result in higher resonant frequencies compared to manufacturer's specifications. The method used was the one from Rod Elliot's pages http://www.sound.westhost.com/tsp.htm with some minor differences.
Edit: The minor differences are in the equipment and the use of -3dB voltages instead of -6dB voltages to determine Fl and Fh. The resonant peak of the driver is so shallow that it was not possible to use the -6dB voltages with my data!
The equipment used was a MacBook Pro's internal audio input and output, an OPA2134 as a pair of buffers, an 8ohm non inductive resistor, and FuzzMeasure (software used to produce the sine sweep and to record the voltage at the audio input). It should be noted that the software recorded voltages every 1.345826Hz, so the resolution isn't as good as it would be if this were done by hand with an analog frequency generator. It would also take a whole lot longer 😉
My laptop's internal audio input/output had a strange non-linear thing going on independent of the load and output level, so I recorded the loop through response and then used that to correct the driver's recorded response. That seems to have worked well but made things more complicated for me; especially since I used Excel to graph the data... and I must say that Microsoft intentionally handicapped the office software for Macs because it runs about 20 times faster on a 3GHz P4 running Win XP than on 2GHz core duo running OS X.
Anyway, if anyone has any comments or thinks I did something wrong with regards to measuring the T/S parameters please let me know.
Edit: The minor differences are in the equipment and the use of -3dB voltages instead of -6dB voltages to determine Fl and Fh. The resonant peak of the driver is so shallow that it was not possible to use the -6dB voltages with my data!
The equipment used was a MacBook Pro's internal audio input and output, an OPA2134 as a pair of buffers, an 8ohm non inductive resistor, and FuzzMeasure (software used to produce the sine sweep and to record the voltage at the audio input). It should be noted that the software recorded voltages every 1.345826Hz, so the resolution isn't as good as it would be if this were done by hand with an analog frequency generator. It would also take a whole lot longer 😉
My laptop's internal audio input/output had a strange non-linear thing going on independent of the load and output level, so I recorded the loop through response and then used that to correct the driver's recorded response. That seems to have worked well but made things more complicated for me; especially since I used Excel to graph the data... and I must say that Microsoft intentionally handicapped the office software for Macs because it runs about 20 times faster on a 3GHz P4 running Win XP than on 2GHz core duo running OS X.
Anyway, if anyone has any comments or thinks I did something wrong with regards to measuring the T/S parameters please let me know.
And here is an impedance plot of one of the drivers. It is quite close to the impedance plot published on the Jordan site http://www.ejjordan.co.uk/drivers/JX92-graphs.html
Attachments
I have fuzzmeasure here but have yet to use it. (It's waiting until I get a decent mic and preamp to connect to my Powerbook.)
The variation from the Jordan published data might, then, be equipment or methodology, do you think? I know Ted uses a specialised testing rig and dedicated PC for the job. It used to be the MLSSA system but I believe it is something more advanced these days. It makes it hard for anyone experimenting, rather than using one of Ted's or GM's published designs.
The variation from the Jordan published data might, then, be equipment or methodology, do you think? I know Ted uses a specialised testing rig and dedicated PC for the job. It used to be the MLSSA system but I believe it is something more advanced these days. It makes it hard for anyone experimenting, rather than using one of Ted's or GM's published designs.
BWRX said:
!! Those aren't close to published spec. Any idea if those are typical of all JX92Ss or just this production run?
Colin said:
I am certain that it is both! Anyone who has tried to measure and calculate the T/S parameters using the method I used can tell you that it never seems to produce the same values specified by a manufacturer.
rdf said:
Please keep in mind that my results may not be accurate!!! Even small errors in the measurements will have a significant impact on the numbers used in the T/S parameter calculations. My setup is far from ideal and was certainly very different from what Jordan uses. That alone can be enough reason for the variation. Also note that I was not intending to rely on the absolute accuracy but the relative accuracy of the results for matching purposes. Again, I do not know if this is flawed logic but it made sense to me and a few others I posed the question to.
I have no idea what specs are typical. This is the first time I've held a JX92S let alone measure one 🙂
Brian,
Your effort is appreciated...it has been months of waiting...maybe you can begin shipping? My wife has been eyeing the money...I can't fight her off much longer...please?
t
Your effort is appreciated...it has been months of waiting...maybe you can begin shipping? My wife has been eyeing the money...I can't fight her off much longer...please?
t
I apologize to all for the wait! But as I said a few posts up, I have begun shipping. The first three pairs of drivers went out today. Once I figure out how to print the shipping and insurance forms online things will go faster. Regardless, tonight I will send emails to the next 10 or so people in line.
Brian,
For domestic shipments using flat rate boxes and USPS, go to USPS.com. You can use clicknship to print online, including insurance up to $500USD...
t
For domestic shipments using flat rate boxes and USPS, go to USPS.com. You can use clicknship to print online, including insurance up to $500USD...
t
Hi t-head.
Yes, I know where to go to fill out the forms... Earlier today I asked the people at the local post office about what weight to enter because that is needed or it won't let you continue filling out the form, even though weight is not an issue with the flat rate boxes. They told me to just use a bathroom scale and round up to the nearest pound, so that's what I'll do from here on out.
I was told I can also fill out the customs forms online, so maybe I'll try to do that for the Canadian and European shipments as well so I don't have to fill out the forms when I get to the post office.
Yes, I know where to go to fill out the forms... Earlier today I asked the people at the local post office about what weight to enter because that is needed or it won't let you continue filling out the form, even though weight is not an issue with the flat rate boxes. They told me to just use a bathroom scale and round up to the nearest pound, so that's what I'll do from here on out.
I was told I can also fill out the customs forms online, so maybe I'll try to do that for the Canadian and European shipments as well so I don't have to fill out the forms when I get to the post office.
Brian,
Sorry I thought you were having trouble filling out the forms...Just weigh one... a local shipping center or your local post office will weigh one for you...the rest will be the same...as for customs forms, you can fill out online but they are repetitive and a pain...good luck...if it helps, contact me offline and I can send self-adhesive forms that print perfectly with USPS and stick on the boxes for domestic shipments...sorry again...
t (Richard)
Sorry I thought you were having trouble filling out the forms...Just weigh one... a local shipping center or your local post office will weigh one for you...the rest will be the same...as for customs forms, you can fill out online but they are repetitive and a pain...good luck...if it helps, contact me offline and I can send self-adhesive forms that print perfectly with USPS and stick on the boxes for domestic shipments...sorry again...
t (Richard)
I would go with the Jordan measured specs when calculating cabinet sizes etc. I don't think the manufacturer would have allowed them to drift that much and the fact you're measuring them all the same seems to preclude random variations. I didn't even know you could use Fuzzmeasure for driver parameters, I was planning to use it for finished enclosure measurement. Anything else is far too complicated for me ...
Good luck with the packing and despatching. I take my hat off (if I knew where it was) to anyone who organises a group buy like this.
Good luck with the packing and despatching. I take my hat off (if I knew where it was) to anyone who organises a group buy like this.
BWRX said:
t-head said:
I think you should bump t-head too. 🙂
My email link to this site has been acting up. I haven't been receiving response notices from subscribed threads. I'm still in Brian, and I believe the email issue is resolved now, but I'll keep checking back just in case.
audiobomber said:
I am currently accepting bribes...
audiobomber said:
Don't worry, you can only be removed from "the list" by request. If you haven't received an email yet it's because I haven't gotten to you yet. If for some reason someone doesn't respond to my emails I will try to contact them by posting here.
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