Best internal design for the standard 2x15" cab?

[mike]

Any thoughts from you technical types as to which design for the classic 24"x15"x40" cabs was the most efficient? Granted, I know that there's many variables in the speaker specs, but all things being equal, if you used the same raw frame speaker model in all three designs, there's got to be one that really delivers the goods.  The three designs I'm referring to, of course, is the original rear-loading horn version, the one-piece baffle with the two cardboard tube ports in the center, and the Hartzell-era cab with the angled port "throat" up and down the right side. I know alot of you are quite nostalgic for that original design used in the 200s cabs, but it seems to me that the port opening is a little too large for damping the speakers efficiently.  Also, the angle of the internal "shelves" seems to reduce the box volume, not giving the speakers much air to work with. Is there some secret to this design? According to Conrad it came to him in a dream, a guy from JBL did the math on it and gave it a thumbs up, and I'm not about to discount the powers of the subconcious--we all ought to let our creative minds run free as much as we can. But I've owned one, with JBL D140's, and it didn't seem to get that loud. The next design was kind of a dull vanilla flavor sort of thing, but you still see it used to this day. Was there a cost efficiency thing in the cab building process that caused the change to this design? My first Sunn amp(Sorado)had this kind of box, and at the time it seemed to boom out OK, except the speakers(CTS?)were crap. The '72-onward design with the continuous angled port would seem to be the most efficient set-up, reminiscent of the later EV T-L box, but I just don't find many of these for sale. Any thoughts or advice? And what was up with those 26" wide cabs(to go with the Model T?) that had four 15" in a "V" shaped baffle, and very little box room? Is that an acoustically legit design, or was somebody sniffing too many solder fumes? OK, OK, I'm through...its just when I see an old Sunn cab for sale I wanna know if it's worth getting it, 'cause you know you'll probably have to replace the speakers...                

[Tom Loizeaux]

This is a reply to your older message above.
   I've been working with several Sunn cabinets for a few years now, trying to get the right speakers into the right cabinets. I began with a pair of 1-15 (Sonic 1-40) bottoms that have the angled port running up one side of the cabinet. They came with Sunn Magna speakers. Though they sounded pretty good, they didn't quite deliver the lowest notes. I eventually upgraded these cabinets with EVM 15s. One EV 15B and one with an EV 15L. Though these were louder and cleaner sounding, I felt there was a little to much "flop" in the 15B. I experimented with progressivly blocking the port. Eventually I found that if I blocked about 1/3 of the original port opening I got deeper lows and a little tighter lower-mid. I actually built tapered wedges, lined them with fiberglass, and wedged then into the angled ports.
Later, when I got a few 2-15 cabinets, I began experimenting with these. I ran a sweep generator through these and found the frequency at which the cones exhibited the least movement. This indicated the cabinets tuned frequency. I found that instead of blocking the maximum amount of port area and going for the deepest bass extension, that if I opened the ports back up slightly, I got a combination of extended bass and slightly more mid-bass output that seemed both deeper and cleaner that the original port design. These reduced ports work equally well with my pair of JBL K140s in the 2-15 cabinets.
   I like to have even response all the way down to open E and, with a little EQ from my amps, I can get a very full rich, even sound that really handles the electric bass well.
   I feel the original ports were a little large and tuned the Sunn cabinets at around 60 to 65 Hz. These larger ports provided slightly higher output but sacrificed cone control and the deepest low end.
   I can discuss this in more detail if you like, just e-mail me at  loizcren@erols.com

Tom