A7 port size

[edfallon]

So I've got an old pair of A7 825 cabinets ca. 1957. I'd like to update the original 803 woofers to new GPA 416-8C. I did some quick box modeling using WinISD and a good model shows 8cu'(I'm guessing that is the rear chamber size of an 825 box), tuned to 24hz, with series resistance of 2 ohms (SET amps). Modeled F3 is about 40hz with F6 about 31hz. What surprises me is the dimensions of the existing port. It's way too big. The modeled port would be a 4" tube around 5" long. Did Altec tune a peak at 50 - 80hz to comensate for the shelved bass reflex response below the horn cutoff? While not perfect, an A7 seems to sound much better than modeling would indicate.

-Ed

[bfish]

Welcome, Ed,

That's been disscussed at length in this old thread;

http://www.hostboard.com/cgi-bin/ult...c&f=3729&t=904

as well as a few others that can be found using the search feature. Pretty much all one might wonder about A7s and a whole lot more. Of particular note are GM's contributions.

[edfallon]

My bad! Your right, this topic has been talked to death already.

-Ed

[ngccglp]

Hi Ed,

I followed those recommendations, but eventually I went back to the stock opening with the 416-8B. Don't know why it just sounds most natural to me.