phenolic vs symbiotik conundrum

[Old Guy]

The model drivers I mentioned had a casting added to damp resonances.

The late model drivers weigh more than they early models because of that casting.

So you completely misunderstood.

I pointed to a series of drivers designed to reduce the issues you were talking about.

This paper discusses increased magnet size

http://alteclansingunofficial.nlenet...ers/TL_231.pdf

Here is the back of a 288C sheet...20 pounds.


http://www.voiceofthetheatre.com/images/288C.2.jpg

And the back of a 288G sheet 29 pounds

http://www.voiceofthetheatre.com/images/288G.2.jpg


To sum up....you are using a lightweight version of the driver designed for higher crossover points used in modern systems, I attempted to direct you to designs optimized for lower crossover points.

The pot casting to damp resonances was added to late Alnico 288, 291, and 290. It was retained when the switch was made to ferrite.

Essentially you are arguing that a 29 pound driver wont resonate less than a 20 pound one.

[kevin@kab]

Hi,
The only points I am making are:
The drivers are brand new made less than 30 days ago, that they have a low frequency specified rating of 300Hz,
and that they were reccomended for my application.
And yet at the very low power that I operate them at -less than 90dB measured at the horn mouth- they are producing a signficant "double tone" at all frequencies below 1000hz
also, as you lower the level down, you hit a point where a "chorus" of tones appear.
Both drivers do this, so that to me indicates that they are defective in some way.

I am unable to accept this as "normal" operation.

Perhaps if I were running these at very high levels, true resonances - that are the result of build design- will apear, but I would not expect that at these low levels.

Kevin
010311

[GM]

Remove the rear cover and see if it still happens.

GM

[Old Guy]

Remove the rear cover and see if it still happens.

GM

Interesting idea.

I'm wondering,,,the big transformer cans...would there be any merit to trying them without the inside cover, possibly filling them with different types? probably not...just my wandering attention span again....

I would think obviously the driver would have to be derated, or am I wrong again?