Help with design of this Altec mid bass horn

GM · April 23rd, 2013, 02:25 AM

You’re welcome! Looking forward to what performance you wind up with as it strays a bit too much from my experience in trying to get as much high SQ BW out of a truncated or compression loaded design, especially when factoring in an 800 Hz XO point.

GM

**atilsley** · April 23rd, 2013, 07:19 PM

GM, if I went back to the drawing board (I still can), but still remained within my restriction of 40cm axial length of horn, what would be the largest square mouth area possible using a standard/proven flare?

GM · April 24th, 2013, 10:17 AM

Again:

"The way to have your ‘cake and eat it too’ though is to plot the 825/828’s area expansion every ‘x’ distance [of your choosing] and extrapolate it out until it meets your mouth dims to find the correct axial length, flare frequency and closest radius. Now it should perform like an Altec through the XO BW except with a bit more bottom end and directivity control."

Conversely, work out the Sm based on axial length and start with Altec's 128"^2 throat if you want the largest practical one.

GM

**atilsley** · April 25th, 2013, 05:28 AM

Thanks gm, I don't understand fully the first para. (btw, I'm using 902's.)

On para two, what is Sm?

I have fixed axial length, but no limit on size on mouth. Hence q re what lowest bass hz can I get depending on choice of flare....

Kindly

**atilsley** · April 28th, 2013, 03:07 AM

Main horn complete....I've added numerous layers of MDF, adding silicone a plenty for dampening. Baffle added, with throat 180mm x 200mm. Will now start finishing inside horn with putty and sanding.

**atilsley** · April 28th, 2013, 04:24 AM

putty filler added

**atilsley** · April 28th, 2013, 05:33 AM

GM, could you pls clarify how 128 sq inch throat is worked out. The sq root of 128 is 11.3 inches. When looking at A7 and other cabinets, the driver cut-out is around 8 inches by similar....hence my 18cm x 20cm actual.

Do you count the total area at the begining of the horn (including driver cutout) as the throat?

**Alien_Shore** · May 8th, 2013, 12:34 PM

Great project, Andrew.
So good to see the experimenters diving in and creating something new. Did you model the sealed box that you wound up with, or did you just take a guess at the dims?