Q for original A7 828 owners

[tillpape]

Hi, i have one question that could be best answered by an owner of an original Altec A7 828 enclosure:

Whats the max. excusion of the speakers membrane towards the front, before the membrane hits the board it is mounted on ?

If you look into the horn, you see some small distance between the board and the speakers membrane surrounding, what would be the max. way it could travel towards the front. This measure is what i need.

Thanks, Till

[joyspring]

Don't worry about that at all; the linear excursion
capability of both the 416 and 515 LF drivers is far less than the thickness of the baffle.

From Todd's ALTEC LANSING\'S (unofficial) HOMEPAGE:

http://nleinternet.net/alteclansingu...ele-Small.html

The Xmax (difference of the air gap and voice coil height) is less than 0.2" for both 416 and 515.

If the diaphragm is striking anything beyond the baffle, you're definitely overdriving the system!

BobR

[tillpape]

yes, but this does not help me. As i can?t get those original Altec drivers, i use a TAD 1601a with linear excusion of +-8mm and max. excusion before damage +-16mm .

Mounting the TAD directly to the baffle without distance ring gives me a gap of about 3 or 4mm. Also this gap determinates the compression chambers volume.

This is the reason why i please 828 owners to measure the gap between baffle and mebrane surrounding and tell me.

[GM]

This is a function of how thick the gasket is and how much it is compressed. Of more importance is cab Fb and ensuring it is not driven hard enough below it to slam the driver against it. Mild 'slapping' will not harm an Altec and I can not imagine it would a TAD either, though it can be annoying.

Anyway, my four 515s average ~7.4mm of clearance if they were mounted on a constricted throat baffle. The front chamber volume is not critical since it is a narrow BW, truncated design with such a low Fh (~338Hz) that within reason you can space it back quite a bit. Way back when, local bands would load 825s with then high excursion JBL 2235Hs gapped till they did not 'slap' and they sounded fine, and considering spacing it back to at least Xmax is not much more than the design calls for it should be fine and play louder than you can stand.

GM

[tillpape]

Thanks, those 7.4mm are the information i needed.

My concern are less condition while playing music, i doubt i will ever rich xmax under listening conditions possible inhouse. Its more because i fear to damage the speaker at turn-on thumbs.