I got a pair of Altec 515C speakers the weekend after ATF2001, always wanted some but couldn't find an affordable pair. I have Altec 421-8H drivers in the LaScala, very nice, but the big Alnico 515 have a bit of a reputation. Hey, wow, now that I think of it... A new bass horn perhaps, something like the LaScala but with an extended bottom end. 60Hz sounds like a good result, but the smallish front horn load offers only a very dry (but very fast) sound in the bass area. I'd like some oomph to go with it. You just know they can't go deep enough on some songs (Enya: Dan Y Dwr, Roger Waters: Three wishes etc. etc.). After a while you stop fooling yourself that the speed makes up for this loss.
Looking at horns turns quite depressing. Below 50Hz the horn size starts increasing beyond reasonable sizes. Just look at the VOT horns; even these only go to 50Hz (-6dB?). Horns are starting to fall out of the picture as the size increase does not measure up to the gain in low frequency reproduction.
Using a bass-reflex or Onken type cabinet will increase the low end, but a big and heavy cabinet will be needed (150-200 liters for the 515C). The bass really poses a dilemma for me as I want the speed of the Altecs yet also a good foundation in the low end to at least 35-40Hz.
The choice that is lingering is to make an Onken style cabinet, a corner horn or an A7 type cabinet (front horn and rear BR loading). The latter seems to get the favor for now... argh!!!
I settled on a system that is a combination of the horn loaded LaScala and the reflex loaded Onken. The cabinets use a front horn that works from about 150Hz and up, and a reflex loading to handle the low end. The result is just as the description is, it has the wallop of the horn loading and connection with the Oris front horns, plus a nice bass down to 40-45Hz. Everything I expected and hoped for, I'm a happy camper :))))
The LaScala is very "fast" and connects well with a front-horn system, yet by itself it will not produce enough bass for my taste. It is very dry and jumpy and requires a support for the lower octave (<50Hz). The Onken (with 26cm Vifa) has a very fat bass, very dark and heavy, yet lacks "speed" and wallop and connection with the front-horn mid/high. With either one of these you can live, but there is always something to let you know the match is not as it should be.
The new system combines the matching and "speed" of the front horn with a nice foundation in the lower region. The compromise is that it does not produce the theater style bass of the Onken, but I think that what it does offer is well worth the change (I would never go back). The cabinet looks like a big cube with a horn stuffed into one side. It is quite big measuring around 70cm cubed, yet it matches the Oris 150 in size and color to make a very nice combination.
The following pictures are courtesy of Mattijs de Vries and Bert Doppenberg