Fostex FF85K 3rd party measurements?

[DcibeL]

Hello,
I am seriously considering the Fostex FF85K for a future project. I don't have the equipment available to me to complete my own frequency response measurements, would anyone have this driver that has measured it? An impedance plot would be very helpful to me as well as the graph in the datasheet is somewhat vague. I have searched around but have not found any measurements for this driver other than what is in the datasheet.

I use the FRD Tools for simulations, so it doesn't matter much to me if the driver has been measured in a box or on a baffle or what, as long as I have this information I can simulate it. If the driver has been measured in one of those back loaded horn things it's a bit of an issue, however.

Thanks!

[planet10]

In this thread on Tysen, A thread for Tysen and variations on FAST there is limited FR data, and an impedance curve. I can't recall whether the impedance curve was a stock FF85K or the FF85KeN we use.

At least in the form we use it in (i've not bothered listening to a stock one) it is a fantastic driver.

dave

[DcibeL]

The frequency response posted there is the response of the entire system, which I'm not sure I can use. I did find the free-air impedance plot, thanks for that.

Particularly, I am interested in a 3rd party measurement to see if the 4dB sink in the frequency response from 1k-2.7kHz actually exists, and I would like to verify the rising response in the top octave.

I have this crazy idea in the back of my head for a center channel speaker using an FF85K with a Fountek FW168 on either side. Hopefully with the use of the FF85K I can remove the sideways MTM lobing issues without having to move to a 3-way speaker.

[planet10]

Not a crazy idea at all... read thru the Tysen thread, it mentions some similar stuff. The FR is limited by a roll-off caused by my mic cable, any rise is above 15k

dave

[DcibeL]

I ran some quick sims last night with the spec sheet data and the results are very promising. Some notes:

-Frequency response is a bit more ragged than I would like but I think the lack of off-axis nulls will make up for that.

-The Fountek FW168 works very well in a small ported box, and has a highish impedance that running two in parallel does not present a difficult load to the amp at all.

-The acoustic crossover point is about 700Hz so shouldn't put too much strain on the little Fostex. 4th order acoustic filters all around, with some extra bits to smooth the rising response of the FF85K. FW168 is crossed over low enough that it doesn't need a notch filter.

-I kept a bit of the rising high frequency response, as this speaker will not be listened to on-axis. Response is nice and flat at 10 degrees off-axis (think speaker placement under a TV).

-Sensitivity of the FW168 is a good match for the FF85K making for a nice 87-88dB sensitive speaker with BSC.

-Total build cost should be around CAD$250.

I'll post some graphs and whatnot in the near future when I have something a little more finalized. Probably in the loudspeaker forum, I'm not sure how many of the "fullrange" crowd is interested in my MTM center channel with Fostex FF85K.

[chrisb]

you might want to take a look at the Silver Flute 6" woofers as well

[planet10]

Originally posted by DcibeL
-The acoustic crossover point is about 700Hz so shouldn't put too much strain on the little Fostex.

I'd suggest that moving the XO lower will put it where it will be less audible, and you'll be able to take greater advantage of the FF85 goodness.

dave

[DcibeL]

Originally posted by chrisb
you might want to take a look at the Silver Flute 6" woofers as well

The Silver Flute drivers I'm sure would work good as well (as would a lot of drivers), however the Fountek FW168 was chosen for both it's price/performance ratio, as well as it's visual appearance. Since the speakers in my surround system don't match, it would be best to at least have them visually resemble each other. As such, I have been contemplating an attempt to paint the phase plug of the FW168 black to match my NHT XdS speakers.

[DcibeL]

Originally posted by planet10
I'd suggest that moving the XO lower will put it where it will be less audible, and you'll be able to take greater advantage of the FF85 goodness.

I will take this into consideration. I just did a quick simulation for a sort of proof-of-concept.

[chrisb]

Originally posted by DcibeL


The Silver Flute drivers I'm sure would work good as well (as would a lot of drivers), however the Fountek FW168 was chosen for both it's price/performance ratio, as well as it's visual appearance. Since the speakers in my surround system don't match, it would be best to at least have them visually resemble each other. As such, I have been contemplating an attempt to paint the phase plug of the FW168 black to match my NHT XdS speakers.

whichever direction you head, enjoy the trip