Need help to finish speaker design

[truck]

Hi,

I built a couple of speaker cabinets, but need help figuring out the port hole sizes. Each cabinet has two port holes that are 4 inches in diameter. My speaker design software is giving my ridculous figures. If any one could help me figure out the port tube lengths, I would apperciate it.
The speaker cabinets are 4.3 Cubic foot each. The driver is a 500W Delta-15LFA 15 inch driver.

here are the thelie small parameters:

Le: 1.49mH
Z: 8 ohms
Re: 6.3
Fs: 41 Hz
SPL: 96 db
QMS: 6.65
QTS: 0.58
Xmax: 4.8mm
Vas: 6.6 Cu ft.

The suggested cabinet size is 5 cubic feet.

If anyone could input these figures into their speaker design program and give me the port tube lengths for a port hole size of 4 inches in diameter, I would apperciate it.

Thanks,
Truck

[Brian Steele]

Hmm... the high Qts figure for those speakers does cause some issues.

You mentioned that each cabinet was about 4.3 cu.ft., with two cutouts for 4" vents...

I'm not familiar with those speakers, but based on the parameters you quoted, I'd be tempted to try this:

1. Make each vent around 10" long. Ensure that there's at least 4" clearance between the rear of the vent and any internal walls.

If the result of that is not good enough...

2. Stuff the box with polyester fiberfill or acoustic fiberglass to raise the effective Vb to around 5 cu.ft. or higher.

If the result of that is not good enough

3. Use EQ to tame the midband hump in the response (around 70 Hz or so)

You're not going to get below 50 Hz with this design, but what you will get is some pretty loud bass.

[Chris Roemer]

Hi,

I built a couple of speaker cabinets, but need help figuring out the port hole sizes. Each cabinet has two port holes that are 4 inches in diameter. My speaker design software is giving my ridculous figures. If any one could help me figure out the port tube lengths, I would apperciate it.
The speaker cabinets are 4.3 Cubic foot each. The driver is a 500W Delta-15LFA 15 inch driver.

here are the thelie small parameters:

Le: 1.49mH
Z: 8 ohms
Re: 6.3
Fs: 41 Hz
SPL: 96 db
QMS: 6.65
QTS: 0.58
Xmax: 4.8mm
Vas: 6.6 Cu ft.

The suggested cabinet size is 5 cubic feet.

If anyone could input these figures into their speaker design program and give me the port tube lengths for a port hole size of 4 inches in diameter, I would apperciate it.

Thanks,
Truck


Pretty high Q for a vented box.

WinISD shows a 0.71 Q in 14 cf with an F3 in the low 50's. In YOUR 4.3 cf box (which would "look" like 5.2 cf to the woofer if "stuffed") the Q raises to 0.87 w/o too much peaking. This would be my recommendation, to seal the cab and stuff it with fiberglass.

For vented alignments, models with F3 in low 20's in a 14 cf box (but not in YOUR box).
In YOUR 4.3 cf box: Fb, F3, 4"d vent length (1 vent), (2 4"d vents), ripple
20 Hz, low 50's, 16" long, 36" long, +1dB "hump" at 90Hz (sealed box is flatter)
25 Hz, low 50's, 9", 22" for 2, +1dB @ 90 Hz
30 Hz, high 40's, 1 vent @ 6", 2 vents @ 14", +2dB @ 90
35 Hz, high 40's, 1 @ 3", 2 @ 10", +2dB @ 80 Hz
40 Hz, mid 40's, 1 4"d vent only 2" long, 2 4"d vents EACH have to be 7" long, by now you've got a 3dB hump at 80 Hz, yikes!

Chris

[Brian Steele]

Pretty high Q for a vented box.

WinISD shows a 0.71 Q in 14 cf with an F3 in the low 50's. In YOUR 4.3 cf box (which would "look" like 5.2 cf to the woofer if "stuffed") the Q raises to 0.87 w/o too much peaking. This would be my recommendation, to seal the cab and stuff it with fiberglass.

While Qts suggests that vented alignment won't be flat, a sealed alignment will have much lower power handling in the passband. Which would be preferable? I guess that depends on the intended application.

The mid-band "hump" can be corrected by EQ (e.g. with my suggestion, -2dB @70 Hz Q=0.7 should do the trick).

[truck]

Thanks to everyone who helped me with my design so far.

God Bless,
Truck