How do your 2 subs sound compared to a conventional design?
Those subs were made for a purpose. Being isobarik and coupled cavity, they are very inefficient.
I built them to splice to the speakers that are now my surrounds, that I used to use on location recording. They are sealed with an F3 of 53 Hz. Band pass subs have a second order roll off high and low pass acoustically.
Also in a band pass sub, the designer has precise control of Q. So I could extend the bass, without, making it at all boomy
The current speakers use the venerable KEF B 139s on a ported enclosure. I know these driver s very well after thirty plus years using them. I can really mask the fact the enclosures are ported, and they have an alignment that is first order stating at about 100 Hz, so -3db is 53 Hz, but they are still only 6 db down at 30 Hz, at they point they roll off at 24 db per octave.
So the subs have practically nothing to do. I have customized a Crown VFX 2 to splice the curves. So now the combined curves roll off at 12 db per octave with a 3 db point of 27 Hz.
So if you play the subs alone, you only occasionally hear them on music.
However on tone sweeps you can hear the difference markedly, and also on music that has low bass content. Even though the are highly inefficient, they are called on to produce so little sound the Quad 405 2 driving them barely gets warm.
I would not recommend these subs for a home theater situation.
The other thing is that coupled cavity designs have higher distortion and time delay issues than conventionally ported subs. In fact the distortion and time delay issues are so high with third and fourth order coupled cavity alignments, that I won't use them. Apparently Dr Omar Bose disagrees as he lives these higher order alignments for his bass modules.
So in summary, these subs were designed and built for a very specific purpose, and for general use I would expect people to be quite disappointed with them. However in the manor I use them, it guilds the lily nicely in that very nice sounding system in that space. That is the beauty of DIY.
It was a foul rainy cold afternoon on Saturday, and my wife and I listened to music all afternoon by the fire, ending our listening with two hours of Prairie Home Companion. A really warm fuzzy pleasant afternoon.
