Pls help with 15cxn88 coax

[mark100]

Hi all, I want to try to build a co-axial box similar to the Danley SM-80.
I'll be using the B&C 15cxn88, and plan on making a two section conical horn to mount around the driver.
Unlike the SM-80, I want to port the box. I'd like to achieve solid response from at least 80 Hz up.

Here's my initial efforts with hornresp on the LF/mid cone section:
Pls critique at will....any and all thoughts welcomed..

and I have a really dumb HR question......no matter what I try, power always rolls off dramatically after 3-700 Hz. There's nothing i can do to make response extend to 1000Hz or higher as in the B&C spec sheet. (This is the first time I've tried to model anything other than a sub.)

THANKS!

 

[chris661]

Some thoughts...

1 - Looks pretty good! FWIW, I'd check phase shifts and/or group delay around the port tuning frequency - more phase shift means it's additional PITA to integrate a subwoofer.

2 - When Hornresp simulates "Power response", that's the sum total of all on- and off-axis output. Try simulating at zero degrees off axis. NB - only works for single-section horns.

3 - Above ~10xFs, T/S parameters aren't particularly useful for predicting a driver's behaviour. You're better off looking at the manufacturer's frequency response chart, and combining with the expected gain from the horn.

I like the idea of an SM80 with more guts. Haven't tried them in person, but a sealed 12" can only do so much below 200Hz.

Chris

 

[mark100]

Thanks Chris,

I won't have any group delay to contend with...good ole FIR

I tried the hornresp one-section conical, 0 degree simulation. Yes, response did improve some above 300Hz.
But still, not at all like the manufacturer's spec curve.

I didn't know T/S parameters don't hold up past about 10xFs....
What have folks been doing to sim any driver that spans more than 3 octaves?
Just looking at manufacturer's charts, like you say ? Wow....

 

[freddi]

that should be fun (I'm on a new pc w. no hornresp yet)
Frazier - Mitchell did that type some time ago http://www.frazierspeakers.com/download/c40.pdf
http://www.frazierspeakers.com/download/cat59.pdf

 

[GM]

HR etc., only shows a driver's/horn's piston response; its TL, breakup modes BW that makes up the HF output can't be predicted with any degree of accuracy.

T/S parameters peter out at the driver's upper mass corner = 2*Fs/Qts' and lower mass corner = Fs*Qts'/2 with the mean of course being Fs.

Qts' = Qts + any added series resistance: mh-audio.nl - Home

GM

 

[mark100]

Thx freddi,
Ready to go, just need to build a hot-wire foam cutter to make the circular horn.

Thx GM, very helpful

 

[GM]

You're welcome! Looks like a fun project!

GM