Any online source for FRD and ZMA files (looking for Audax PR170M0 & Fostex FT17H)?

[Saurav]

I know the right way to do this is to measure my drivers for myself. But until I have the capability to do that, does anyone know of a place where I can find this information? Or, if anyone has measured those two drivers, would you be kind enough to send me the files? Measurements on someone else's drivers would be better than nothing, and it seems like most of the crossover simulation software needs this data.

I searched the archives, and there have been suggestions of forming a driver database, but I didn't find anything beyond that.

Thanks for looking.

Saurav

[Saurav]

Alternatively, does anyone know if the T/S parameters for the FT17H are available anywhere? I figured out how to get rough FRD/ZMA information using Subwoofer Simulator. I found the T/S parameters for the Audax midrange, but can't find any for the Fostex horn tweeter.

Thanks,
Saurav

[moving_electron]

Originally posted by Saurav
Alternatively, does anyone know if the T/S parameters for the FT17H are available anywhere? I figured out how to get rough FRD/ZMA information using Subwoofer Simulator. I found the T/S parameters for the Audax midrange, but can't find any for the Fostex horn tweeter.

Thanks,
Saurav

For the FT17H parameters go to:

http://www.madisound.com/

Click on Catalog -> Fostex Speakers -> FT17H

[Saurav]

I've seen that page, but all I can find on it is nominal impedance and efficiency. Is there a way to derive the various Qs and Vas information from what is available in that document?

I also saw someone mention what looked like a curve tracer type of program, something that could take an image and generate the numbers for the curve. Is this what SPL Tracer on the FRD website does? Is there a corresponding program for impedance curves?

Edit: Never mind, I answered my own question. Should have tried out the software before asking. It looks like it can do frequency as well as impedance.

[kelticwizard]

Here is the thread where it is mentioned.
Scan-Speak FRD ZMA request

Just to reiterate: the impedance graph can be synthesized by Subwoofer Simulator and made into a ZMA graph-both impedance amplitude and impedance phase.

Subwoofer Simulator was written by our own F4ier. You can Email him if you have questions.

[Saurav]

I'd seen that thread. I have the T/S parameters for the midrange, so I used Subwoofer Simulator to get the FRD/ZMA files for that driver, complete with phase. I don't have T/S parameters for the tweeter. So I used SPL tracer to get the FRD and ZMA files, which don't have any phase information. Do I still have a way of generating phase information? I think I'll still need the T/S parameters to be able to do that.

I think I have enough to get started and mess around with the XO simulator software to see how it works though.

[kelticwizard]

Be careful with using Subwoofer Simulator to create frequency response for a driver.

Even Isaac, the creator of the program, says that the frequency response rolls off in the high end faster on Subwoofer Simulator faster then it does in fact. It has to do with the fact that cone breakup modes, etc are not really calculable on Subwoofer Simulator.

As a person who uses Subwoofer Simulaor often, I really do not use it to predict midband or high band response. Just bass characteristics, which is where the issues are.

Is there a chart of the frequency response by the manufacturer that you can use SPL Tracer to use? I do believe that Subwoofer Simulator does a good job with impedance magnitude and phase, though.

I also think you can simulate the impedance info for the tweeter using Subwoofer Simulator. The way I see it, a tweeter is like a little closed box speaker, and the Q info is the same for speakers that have a Qts of 0.5 in free air or a Qtc of 0.5 in a closed box, (starting with a driver of lower of lower Qts and letting the enclosure raise it to 0.5).

By the way, what is your tweeter?

[Saurav]

Thanks, that Q information should help. The tweeter is a Fostex FT17H. I'll try a different midrange or tweeter if these two don't work with each other.

I used SPL tracer to trace the curves for both drivers, but now my crossover simulator program won't read one of the FRD files. It reads the other one fine, so I'm not sure what the problem is. I'll have to play with that some more. I'm using software on the CD that came with Weems' (Weebs'? I always get the name wrong) book.

[kelticwizard]

Saurav:

Sorry, I did not realize your tweeter was a horn. All bets are off as regards using Subwoofer Simulator to simulate the phase response of a horn.

I would suggest you start another thread on the phase response of that horn tweeter. As I understand it, (and I am not experienced in using horns), the horn is resistive throughout it's operating range. So I would guess that 0° or near it would be the electrical phase of the horn tweeter.

However, I don't know about the acoustic phase. I am given to understand that horns are superior in this respect, but again I am going by imperfect knowledge.

I do believe the fact that your tweeter is in a horn would override any characteristics of the driver itself. I suggest you start a new thread on the phase characteristics, both electrical and acoustic, of horn tweeters.

[Saurav]

That's good advice about starting a new thread, I'll probably do that once I know what questions to ask Right now I still have a lot of work to do, I was just trying to get a start on playing with the XO modelling software.

Thanks for all the help.