Skytronic/Fenton/QTX/Tronios 8" Aramid/Kevlar sealed for a 3 way


2018-07-24 7:48 am
I have one of these cheap 8" Kevlar woofers, mine is branded Fenton but they're available as other brands. Model number is 902.426. I'm intending to use two of these in a sealed enclosures to add onto my existing small sealed 2 way speakers and make them 3 way. I'm using an external active crossover and amps. The crossover is a Behringer CX2310 (2 way plus sub output), so for 3 way stereo I would swap it for a CX3400.

My initial plan was to use the one 8" driver as a mono subwoofer, crossed over at 80Hz, but I now think a pair of these crossed over higher up (300Hz maybe) and run in stereo would give a better result. The 2 ways I have are based on Visaton FR10 full rangers and Monacor HT22 cone tweeters. I really like the mids from this little 4 incher. I'm currently using a pair of JPW Sonatas in mono for bass (low passed from the CX2310 at about 100Hz). They're 5 inch drivers in sealed 13 litre (estimated) boxes.

So my next step is to put the 8" driver into a sealed box and test it as a mono sub. If I'm happy with that then make another and run them as stereo woofers.

Bjorno has kindly taken some measurements and 20 litres is suggested for sealed. His workings are here

However, according to the manufacturers T/S numbers, a sealed box with a Qtc of 0.707 would be about 32 litres. Quite a difference. Both result in a f3 in the low 50s.

Which size should I shoot for, 20 litres or 32? The enclosures are going to be on a desk so the smaller the better.

Another option for a sealed woofer is the 6.5 inch Peerless SDS-160F25PR01-08 . They work out at 27 litres to get to 60Hz f3 at Qtc 0.707. If 20 litres for the 8" Kevlar is correct then these would need a bigger box and still don't go as low. People seem to like them though.

Any wisdom on this or suggestions of other 6" to 8" drivers that would work well in sealed boxes would be much appreciated.