Help designing an efficient HT speaker

[paulspencer]

I'm looking to design a 2 channel 3 (or more) way efficient speaker system with an SPL target of 120 dB from 20 - 20k.

The room is ~ 3.9 x 4.2m with a ceiling height of approx 2.8m and the construction is probably well damped enough in the bass range that modes will probably not be as bad as you might expect.

Subwoofer: 2.6 wide (or more) x 2.6 high x 0.5m deep loaded with 2 x AE speakers AV12 ... in hornresp models well and has some compromised horn loading down to 20 Hz as it easily hits 120db @ 20 Hz with 50w IIRC.

Active crossover: Behringer Ultradrive DCX
EQ: Behringer Ultracurve DEQ

The part I'm most undecided about is the mains.

What appeals most at present is a 2 way inspired by the Gedless Summa speaker:

http://www.gedlee.com/Summa.htm

A 15" pro driver with a CD in a waveguide crossed at 900 Hz, which Geddes shows to achieve an excellent on and off axis response.

I didn't think a CD could go that low without sounding harsh, but after investigating I've found that they vary a lot in what they can do. eg. Selenium D3305Ti DPD can get down to 800 Hz with 150w power handling and 108db sensitivity, although it needs eq to get above about 16k.

Has anyone tried this approach and if so what results did you get?
Has anyone heard the Summa speaker or something similar?
Has anyone tried either the Peavey Quadratic Throat Waveguide or an oblate sphereoid waveguide?

I was previously considering a 3 way main with a midrange conical horn as well, however I'm starting to think a direct radiator is the way to go.

Thoughts anyone?

[sreten]

Hmmm.....


The white paper, whilst quite interesting fudges a number of issues.
Baffle step compensation. for CD drivers, diffraction is less of an issue.
High efficiency + big drivers + horn loaded treble = low distortion.

Seems to explain quite well why people like the 15" Tannoy dual
concentrics, which arguably have been doing all this for years.

/sreten.

[paulspencer]

What issues does it fudge?

[sreten]

Originally posted by paulspencer
What issues does it fudge?

Baffle step compensation.
For CD drivers, diffraction is less of an issue.
High efficiency + big drivers + horn loaded treble = low distortion.

1) Is not accurately described.

2) The diffraction issues of the cabinet are less with directional drivers.

3) Isn't really mentioned, though it would be a major feature of the sound.

/sreten.

[paulspencer]

Anyone else? Especially experiences regarding using compression drivers for hifi use ..

[paulspencer]

also thinking something like this:

http://www.jbl.com/home/products/pro...&cat=K2&ser=K2



reviewed here:
http://www.ultraaudio.com/equipment/jbl_k2_s9800.htm