surround with Visaton FRS8, measurements and design.

[ßart West-VL.]

Thanks a lot guys, really appreciate the input.

I'll go ahead and put one at the time in a baffle or a small closed box, to measure.
No need to measure them ALL again I think. Looking at the previous measurements, it might be useful to search the ones with the most different T&S parameters and do the frequency sweep.

 

[Rudolf]

I'll go ahead and put one at the time in a baffle or a small closed box, to measure.

Don't put them in a baffle, if you finally want to use them in a box.
Look how the FRS8 measures in 3 different (open) baffles:

If you don't understand why it measures such different, those measurements are useless for you. I don't have box measurements for the FRS8, but they will look very different (and much "better") from those presented here.

 

[Barleywater]

Don't put them in a baffle, if you finally want to use them in a box.
Look how the FRS8 measures in 3 different (open) baffles:
View attachment 323544
If you don't understand why it measures such different, those measurements are useless for you. I don't have box measurements for the FRS8, but they will look very different (and much "better") from those presented here.

Observed result for "wide" baffle: how wide, how tall, and what microphone distance?


But yes, great demonstration of reasoning behind measuring driver in target enclosure.

 

[Elias]

The conditions are all the same, the distance couldn't have deviated more then half a cm. This was tricky because the drivers hung from the ceiling on a thin wire about 1.5m long.
I'm doing the same with the T&S parameters and they deviate quite a bit too, but these are cheap drivers, didn't expect consistent results anyway.
This is why I measure them all. This way I can pair them (or 4) by the results. I want to pair two drivers with as much difference, in the high frequency's, as possible.

Sure at this price point tight manufacturing tolerances are not expected. But I think 5 dB midrange sensitivity difference is too much. If one would use drivers of extreme sensitivity difference in a stereo pair, 5 dB offset would ruin the stereo imaging completely.

It could be argued to make more sense to get two better quality drivers than 14 of bad quality drivers, with the same money


- Elias

 

[Barleywater]

Sure at this price point tight manufacturing tolerances are not expected. But I think 5 dB midrange sensitivity difference is too much. If one would use drivers of extreme sensitivity difference in a stereo pair, 5 dB offset would ruin the stereo imaging completely.

It could be argued to make more sense to get two better quality drivers than 14 of bad quality drivers, with the same money


- Elias

Perhaps you are reading too much into initial results for shown conditions of measurement, and acknowledged potential 1cm positional differences.

Fine grain structure of FR plots shows highly correlated behavior <4kHz where 1cm positional differences show in results as sensitivity differences.

Jig with +/1 0.5mm positional repeatability for microphone/driver location would show much tighter sensitivity performance.

 

[Rudolf]

Observed result for "wide" baffle: how wide, how tall, and what microphone distance?

Wide baffle is 22x22 cm, smaller baffle is 22x16 cm. Microphone distance about 60 cm. SPL in the diagrams are not calibrated.

Jig with +/1 0.5mm positional repeatability for microphone/driver location would show much tighter sensitivity performance.

My four Visaton FRS5X measured "naked", without box or baffle. I bought them in pairs at different times at differnet dealers. The difference at 4 kHz is emphazised by the "open" measurement. I'm still amazed about the manufacturing consistency of these cheap drivers.

 

[Barleywater]

View attachment 323620
Wide baffle is 22x22 cm, smaller baffle is 22x16 cm. Microphone distance about 60 cm. SPL in the diagrams are not calibrated.

View attachment 323621
My four Visaton FRS5X measured "naked", without box or baffle. I bought them in pairs at different times at differnet dealers. The difference at 4 kHz is emphazised by the "open" measurement. I'm still amazed about the manufacturing consistency of these cheap drivers.

Thanks for clarifying "wide".

And yes again, consistent fixture and microphone position clean up repeatability.

 

[ßart West-VL.]

Yes, my measurements where hasty and it's the first time I use a measurement system, experimental. So I wanted some results fast to learn and use the program.
It will take some time to do, but I would try a slim box, closed, 1 litre. And a fixed position for measurements.
→Does this sound OK?

In Rudolf's post I read:"Look how the FRS8 measures in 3 different (open) baffles"
One thing I noticed is, that the 3khz bump stays in all configurations. Well, it did shift up a bit with the baffles.

Thanks for the insights!

 

[Barleywater]

I've done a few hasty measurements on similar 3" full range driver. Similar peaking exists for free air and sealed baffle. Source of peak is primarily reflection off of rear of basket and magnet.

Magnitude and width of peak will be influenced by enclosure/baffle used.

Big notch in post #22 for "wide" baffle is due to first big dipole null swamping basket reflection.