Have 105db bass cabinets - What do you recommend for mids and highs?

[j.burtt]

Picked up theses Frazier Super Texans a couple of months ago. Jack Frazier was a friend of Paul Klipsch and built speakers here in Dallas from the late 50's to the early 70's. Some believe the Jubilee bass bin was inspired by the Super Texan.


I will be using 2A3 monoblocks with massive, low dcr power supplies and would like to use passive crossovers. I have purchased a Cross Spectrum Calibrated EMM-6 Mic and a preamp to use with REW to help with measurements and mechanical time alignment. I will be looking to some of the more technically inclined for help with the crossovers as the project progresses.

I will not be using the Frazier horn shown in the picture. Last week I picked up a pair of Dave Harris' finished 2" Eliptrac 400 horns. I'm not married to these horns, but have read good things about them. I was considering going with either B&C or Radian compression drivers and finding a suitable horn for the high frequencies.

B&C - DCM-50 for mid and DE-10 or DE-120 for highs.

Radian - 850pb for mid and 475pb for highs.

The only other thought I have is using a cone driver to cover the midrange. That would of course limit the total sensitivity of the speaker and leave me with attenuating the bass cabinet, which goes completely against my more is better thinking. Kinda like putting a governor on your 600 horsepower corvette so it will only put out 300 horses.

I'm buidling the amplifiers now but am new to crossover design, so please include whether 8 or 16 ohm would be preferred for the compression drivers. I have read that one of the big benefits of using 16 ohm CD's is being able to use half value caps versus 8 ohm. I plan on using nice quality parts, so that would be nice.

Thanks for any input,

James
Dallas, Texas

 

[weltersys]

1)Picked up theses Frazier Super Texans a couple of months ago. I have purchased a Cross Spectrum Calibrated EMM-6 Mic and a preamp to use with REW to help with measurements and mechanical time alignment. I will be looking to some of the more technically inclined for help with the crossovers as the project progresses.
2)The only other thought I have is using a cone driver to cover the midrange. That would of course limit the total sensitivity of the speaker and leave me with attenuating the bass cabinet, which goes completely against my more is better thinking. Kinda like putting a governor on your 600 horsepower corvette so it will only put out 300 horses.
3)I'm buidling the amplifiers now but am new to crossover design, so please include whether 8 or 16 ohm would be preferred for the compression drivers. I have read that one of the big benefits of using 16 ohm CD's is being able to use half value caps versus 8 ohm.

James,

1)The 105 dB sensitivity of the Frazier Super Texan is likely in the crossover region. At 600 Hz the response of the folded horn will be quite peaky, and will not be uniform off axis, as the two horn exits are more than 1/4 wavelength apart that high. The low frequency output is rather anemic due to the relatively short horn path length. Even though the FST horn is relatively short, to time align mid or high horns will require moving the drivers back a few feet behind the rear of the cabinet unless you delay their output. Once you measure the actual output you will be able to see that the stated frequency response and sensitivity is rather overstated, to put it mildly.
Not to rain on your parade, but you probably will only find the output of the FST usable from around 80-200 Hz, a mid-bass or "kick bin" by today's standards.
2)Midrange cone drivers can be horn loaded and easily keep up to the FST. They also can share the same horn as the high horn, as is done in Tom Danley's Synergy horn designs, making for a simple cabinet construction, though passive crossovers for horn systems are never simple.
3) 8 ohm drivers are 3 dB more sensitive than 16 ohm drivers, which allows for more relative high frequency output (3 dB more midrange attenuation), helpful if you decide to use constant directivity horns.

Art

 

[DrBoar]

To time align horns you need digital crossovers most of the time. If you are lucky you get bass down to 50-60 Hz. The horn is to short for deeper bass and the mouth area is small (=peaky response). Try to cross over the horn not higher than 600 Hz. How low you can get depends on the midrangehorn/driver as well as high you play and how steep the crossover is.

 

[j.burtt]

I'm in the process of moving or I'd be firing up the mic, preamp and REW to get some measurements. There's a guy on the Frazier Users Group who was Frazier's sales mgr. and stated they were more like 106db. He also commented the horn length on the Super Texan was 7.5 feet. The original Texan was an 8" driver in this cabinet. The Super Texan with the 12" bass driver came about from commercial demand for higher SPL requirements. He said he preferred the 8" driver in this cabinet for HiFi or smaller venues.

I guess I could always go with the minidsp to cross and time align the bass to the upper end, and passive on the mid to tweet transition. If these don't play into the 40's without forcing them to do things they weren't designed to do, I'll probably regroup and look for other options.

James

 

[weltersys]

There's a guy on the Frazier Users Group who was Frazier's sales mgr. and stated they were more like 106db. He also commented the horn length on the Super Texan was 7.5 feet.

James,

If the guy is correct about the horn length, the cutoff could be as low as 38 Hz, though it could not be 106 dB that low, unless room gain is added. You can't count on room gain, though with DSP you can easily compensate for a falling frequency response, but output is limited by sensitivity and excursion.

Generally speaking, one decade (38-380 Hz) is about the limit for a well-designed front loaded horn, and down that low, cone drivers (horn or front loaded) are a much better value than compression drivers.