Free air resonant frequency (Fs) of AR 8" driver

[Kuja]

Hello again.

Does anybody know what was the original free air resonant frequency (Fs) of AR 8" driver?

Or at least what it should be?

I need to know this since I plan to measure Fs of this driver with new surrounds.

The goal is to find out if new surrounds are the cause of thinnish sound coming out of my AR-17 speakers.

I wrote about this in my previous post:

http://www.classicspeakerpages.net/IP.Boar...?showtopic=5598

My drivers are 20001-1.

Same drivers were used in AR-18, AR-17, AR-15 and AR-25. I also think that they were also used in somewhat older AR-16. Similar driver was used in AR7 and maybe AR6.

I'm sure that there are other 8" AR drivers with different codes.

I think that 8" drivers from my AR-90 have different code.

Physically they seem identical to 20001-1 drivers...

If you don't know the Fs for that exact driver, maybe values for other similar 8" drivers used in AR7 or some other small AR model might be useful too.

They all worked in small enclosures and many folks praised bass coming out of them.

Thanks in advance,

Aleksandar

.

[tysontom]

Hello again.

Does anybody know what was the original free air resonant frequency (Fs) of AR 8" driver?

Or at least what it should be?

I need to know this since I plan to measure Fs of this driver with new surrounds.

The goal is to find out if new surrounds are the cause of thinnish sound coming out of my AR-17 speakers.

I wrote about this in my previous post:

http://www.classicspeakerpages.net/IP.Boar...?showtopic=5598

My drivers are 20001-1.

Same drivers were used in AR-18, AR-17, AR-15 and AR-25. I also think that they were also used in somewhat older AR-16. Similar driver was used in AR7 and maybe AR6.

I'm sure that there are other 8" AR drivers with different codes.

I think that 8" drivers from my AR-90 have different code.

Physically they seem identical to 20001-1 drivers...

If you don't know the Fs for that exact driver, maybe values for other similar 8" drivers used in AR7 or some other small AR model might be useful too.

They all worked in small enclosures and many folks praised bass coming out of them.

Thanks in advance,

Aleksandar

.

Aleksandar,

The free-air resonance f(s) for the 200001-1 "Universal" AR 8-inch woofer, used in the AR-16 and AR-17, is 25 Hz, +/- 10% or so. The system resonance for the AR-17 is the same as the AR-16 at 55 Hz. The surround will affect this number, of course, so if the woofer has been stiffened by the application of a thick or improper surround, the f(s) will go higher. One statistic: the system "Q" of the AR-17 is (at 0.8) lower than the AR-16 (at 1.15), and thus the damping is higher resulting is slightly more roll-off at resonance (55 Hz). This difference would be nearly inaudible, however. The enclosure volume for both speakers was identical.

If you are in doubt about the woofers' surround replacment, the best bet would be to replace the rubber version you described with a foam aftermarket version of known quality. Overall, the AR-17 has excellent bass response, but it will not bring down the house. It should have reasonably flat response down into the low 40-Hz range in most rooms if the speakers are mounted close to the wall, even placing one speaker in a corner. Since the speaker does not have bass peaks associated with many speakers in this class, the bass can sometime sound "thin" when compared to ported speakers that exhibit bass heaviness at certain frequencies. But in clean deep-bass output and low distortion, there are very few speakers it size that will out-class it.

Questions for you:

(1) How are they placed in your room (out in the room, against the wall, bookshelf, floor, etc.)?

(2) What are the dimensions of your room?

(3) What associated equipment is being used with them (amplifiers, etc.)?

(4) Have you carefully inspected your hook-up to be sure both speakers are in phase?

--Tom Tyson