Poor bass extension from small vintage ARs... Help needed!

[Kuja]

Hello everybody,

For a long time I wanted to pair my Acoustic Research AR-90s with their smallest brothers AR-18s.

Unfortunately I coludn't find any for a long time.

I had to settle with a minty pair of AR-17s that I have found couple of weeks ago.


On The Classic Speaker Pages forum, I've read many enthusisatic posts describing great bass coming out of small ARs like AR4x, AR7, AR18, etc.

AR-17 have similar drivers (or same as in AR-18), same one cap crossover, but their boxes are larger so they should have even more bass extension.


When I hooked them up I was kind of dissapointed.
Their sound is quite thin.

Their sound is very transparent and highly detailed, but with some recordings it can get fatiguing.

There is noticeable lack of bass.

When I use tweeter level switch on the back, tweeter output is reduced but sound gets dull and life is sucked out from the music.

I'm not sure if my expectations were too high for a speaker system of that size, or there is something wrong with them.





I suspect that the problem might be in woofer surrounds.

I hear that they are very important in sealed box design.

Original foam surrounds that rotted away due to their age, were replaced with rubber ones by original owner.

Original AR foam surrounds were very thin and soft.

Rubber surrounds that are on my AR17s are much thinner and softer than modern foam surrounds that are available to me locally.
Modern foam is quite thick and it is much harder than the orignal.

Are there some other important properties inheritent to foam surrounds?

Will I get better bass extension if I switch to foam,
no matter if it is thicker and harder than rubber in my present non-original surrounds?



Thanks in advance,

Aleksandar

[ZilchLab]

Measure the woofer Fs.

[Kuja]

Originally posted by ZilchLab
Measure the woofer Fs.

Thanks for the quick reply!

Unfortunately I don't have the right equpment to do it.

How measuring present woofer Fs can help me?
I don't know what it was with the original surround...


.

[ZilchLab]

If you have a voltmeter and a resistor in a suitable range, those plus your computer to use as a signal generator and an amp will suffice.

I suspect someone, somewhere, knows the Fs of that woofer, stock.

[infinia]

How measuring present woofer Fs can help me

Hi
Measured Fs and Q of an acoustic suspension speaker box pretty much tells everything about the bass of your speaker, anything else will be conjecture. Its really easy to do esp in the box, see http://www.diysubwoofers.org/measure.htm