Forte II Passives

[wilson32]

Hi,

I've had my eye out for a pair of Fortes and I just came across a pair of II's with replaced passive radiators. I don't know what they were replaced with but I'm wondering how critical the passives are, and how hard is it to find original 15"
passives for the II's? A quick search of the bay showed no completed listings.

Should I take a look at these or should I pass?:



Price is nothing special depending upon cost of passives - the good thing is that these are close to me and the seller also trades

Thanks for your help.

 

[DavidF]

Hi,

I've had my eye out for a pair of Fortes and I just came across a pair of II's with replaced passive radiators. I don't know what they were replaced with but I'm wondering how critical the passives are, and how hard is it to find original 15"
passives for the II's? A quick search of the bay showed no completed listings.

Should I take a look at these or should I pass?:

View attachment 623430

Price is nothing special depending upon cost of passives - the good thing is that these are close to me and the seller also trades

Thanks for your help.

Passive radiators interact with the resonance of the woofer in the enclosure as influenced by its own resonance. Ideally the resonance of the Passive should be tuned to a precise frequency. This is done by adding or subtracting weight to the cone, somehow, though this has limits by nature of the Passive's suspension and mass.

A Passive tuned too high can add boominess to the bass. Too low and it may not be adding anything to the bass response as intended.

So, unless the owner has some experience and tools to match the mass of the replacement with the original, it's sort of a crap shoot. Then again, you may not want to pass on an opportunity to pick up a set of Fortes close by.

The originals do pop up sometime on eBay.

 

[wilson32]

I have a spare set of 12" radiators from some KG4's - could I make an adaptor ring and turn these into Forte I's ?

Anyone have a ball park figure on what a used set of 15's would go for?

 

[moray james]

the 12 inch passives of the KG4 are not heavy enough by a wide margin and will result in a tuning higher than what the stock Forte ll was tuned for. do you have access to a test CD which has test tones? If so you can check for yourself and see what frequency the new passives you have found are tuned at. If you don't have a test disk you can down load test tones from an on line source and then burn them to a CD to use.

 

[wilson32]

I won't worry about the KG4 passives but you've given me an idea.

I have a test tone app on my phone - is it possible to check the tuning of the replacement passives with all the drivers mounted in the cabinet? Just find the frequency that vibrates the passive? If they are too high could they be fine tuned by adding weight? - if too low then they are probably not useable?

Anybody know what frequency the forte ii passives are tuned to?

Thanks

 

[moray james]

you need to be able to play the test tones through the loudspeaker via the system. The Forte ll is tuned to a minus 3db point of 32 Hz. Tuning to 30 Hz is just about ideal as far as I am concerned. Tuning is achieved by adjusting the moving mass of the passive, more weight will lower the tuning point by increasing the overall mass. To find out what frequency any passive is tuned to simply play tones starting above where you expect the tuning point to be at and progressively play lower frequencies and watch the woofer at each tone. When you see that the woofer is not moving and the passive is doing all the moving you have found the frequency that the passive is tuned to. Simple. Tuning to 30 Hz will result in a minus 3db down point in the upper 20Hz range. That is as low as you want to tune with this system.

 

[wilson32]

Thank You