Cross over point and max wattage spec for 288Bs (for testing)

[Squarewave]

I'd like to ring these out and cook em on the bench for a spell as they have been in storage for years. I don't know the limits on lowest xover point, or max wattage for these. Can anyone direct me to the specs?
Thanks very much,
Dan

[Robh3606]

Be careful with them especially if they have original diaphragms. They are aluminum and will eventually develop cracks in the surrounds due to metal fatigue. Putting any real power into them or running them to low will accelerate this process.

http://www.audioheritage.org/vbullet...ragm-Longevity


Rob

[Squarewave]

Be careful with them especially if they have original diaphragms. They are aluminum and will eventually develop cracks in the surrounds due to metal fatigue. Putting any real power into them or running them to low will accelerate this process.

http://www.audioheritage.org/vbullet...ragm-Longevity


Rob

Thanks Rob,
It's possibile the diaphragms are original, old for sure. I've never had the back covers off, not even sure if it's ok to do that.
Would you be willing to take a stab at a "safe" wattage and xover level? (I was thinking 50 watts going easy, and 800 cycles), but I'm a novice when it comes to these drivers.
Dan

[Robh3606]

I was looking on the site and found 15 watts but could not read the frequency. Those are a bit OLD! I wouldn't put more than a couple of watts into them. They are going to be loud as hell not padded down. You will know right away if you have a issue. I would power them up with care. You could safely take the back cover of just be careful and remember you have one hell of a magnet in there so watch out for things magnetic. People have gone to tighten up a loose connection and had the screw driver sucked right in and damaged the diaphragm.


http://www.lansingheritage.org/image...1947/page3.jpg


Rob

[Earl K]

I'd like to ring these out and cook em on the bench for a spell as they have been in storage for years. I don't know the limits on lowest x-over point, or max wattage for these.
Can anyone direct me to the specs?
Thanks very much,
Dan

ALTEC Driver Specs at GPA


The diaphragms used in 288's are really quite fragile ( with low power handling ) by today's standards.

Before they were discontinued they were rated at15 watts of continuous Pink Noise that's been band-width limited from 500hz - 20,000hz, with the driver mounted on a 300 or 500hz horn.

Your first sentence is worrying, it telegraphs the message that you want to destroy your diaphragms ( that'll hardly help any prospective eBay sale ).

[Robh3606]

Glad you posted that must misread the old catalog page. Edited my post so a search engine doesn't grab it.

Rob

[Earl K]

Glad you posted that must misread the old catalog page. Edited my post so a search engine doesn't grab it.

Rob

You likely were quoting that ancient ( mis-information rating of 40-watts program ).

[Squarewave]

ALTEC Driver Specs at GPA




Your first sentence is worrying, it telegraphs the message that you want to destroy your diaphragms ( that'll hardly help any prospective eBay sale ).

Gosh Earl K, I don't want to destroy these, which was the whole point of posting this question! I remember as a kid, we drove these at "hippie" concerts, with low watt tube stereo amps, which are also stupid pricy now.. they sure sounded nice that way.
I'm going with ten watts for testing. Everyone has been most helpful, thank you!! I'll report back.

[Earl K]

Gosh Earl K, I don't want to destroy these, which was the whole point of posting this question! I remember as a kid, we drove these at "hippie" concerts, with low watt tube stereo amps, which are also stupid pricy now.. they sure sounded nice that way.
I'm going with ten watts for testing. Everyone has been most helpful, thank you!! I'll report back.

To test the health of your drivers and their diaphragms you only need apply 1Watt of Band-Width Limited ( 800-20,000hz ) Pink Noise ( preferably all the while viewing the output on some sort of RTA system ).

Applying more than that achieves very little and is quite possibly counter-productive to any possible future eBay sale (IMHO) since savvy buyers don't want power stressed diaphragms .

Buyers typically want to know the DCR value of the diaphragms, as well as good pics of the diaphragms to make sure they aren't creased or shattered.

BTW, there are inexpensive RTA programs for smart-phones these days ( with the best usually being for the iPhone > best because Apple has wisely included some correction filters for the real-world limitations of the builtin phone mic ).