WinIMP help needed, please!

[Rusty the Scoob]

I'm trying to design a sealed cabinet around a JBL 2220A 15" speaker that I was given.

WinIMP says I need 20.6L of volume, and the optimal dimensions are:

0.278m wide
0.445m high
0.167m deep

So those are approximately:

11" W
17.5" H
6.5" D

I'm no expert but that seems pretty small. What am I doing wrong?

 

[Rusty the Scoob]

Hmm.. using a D130 for the driver, a very similar speaker that the 2220A replaced in the lineup, I get much better numbers for the exterior dimensions:

0.390 w
0.602 h
0.248 d

or

15.35" w
23.7" h
9.763" d

rounded to logical carpentry dimensions:

15.375 W
23.750 H
9.75 D

That still seems too small for a 15" speaker but at least it's getting closer.

I'd ideally like it to match the depth and width of my Super Redhead so they stack nicely:

22.5”W x 23”H x 16.75”D

 

[billfitzmaurice]

What am I doing wrong?

Using it in a sealed box.
The 2220 is spec'd for a vented cab.

 

[Rusty the Scoob]

Oh.... I guess I'd better vent it then! Thanks for the pro info!

Hmmm. I was planning to have it reconed to D130 specs: aluminum dome, ribbed cone. But that should only change the tone, not the specs, right?

 

[billfitzmaurice]

I was planning to have it reconed to D130 specs: aluminum dome, ribbed cone. But that should only change the tone, not the specs, right?

It will change everything.

 

[Rusty the Scoob]

Oh... thank you! I'm really glad to have a pro-loudspeaker builder's advice.

I don't fully understand all the specs but to my eyes they are pretty similar.

Brand Model X Vas Qts Fs Sens Pmax Xmax Production Mod
JBL D130 148 297.3 0.25 40 100 75 0.76 Discontinued Mod.
JBL 130A 195 297.4 0.18 37 101 100 2.03 Discontinued Mod.
JBL 2220A 195 297.3 0.18 37 101 100 2.03 Discontinued Mod.


The sound I'm after is Phil Lesh fat, midrangey sound from the 70's. The Wall of Sound looks like it had sealed cabs for Phil's stacks but they are also enormous.... bigger than I could deal with.

 

[billfitzmaurice]

Oh... thank you! I'm really glad to have a pro-loudspeaker builder's advice.

I don't fully understand all the specs but to my eyes they are pretty similar.

Brand Model X Vas Qts Fs Sens Pmax Xmax Production Mod
JBL D130 148 297.3 0.25 40 100 75 0.76 Discontinued Mod.
JBL 130A 195 297.4 0.18 37 101 100 2.03 Discontinued Mod.
JBL 2220A 195 297.3 0.18 37 101 100 2.03 Discontinued Mod.


The sound I'm after is Phil Lesh fat, midrangey sound from the 70's. The Wall of Sound looks like it had sealed cabs for Phil's stacks but they are also enormous.... bigger than I could deal with.

The 130A isn't a D130. Qts is the most significant difference here, that between .18 and .25 is significant. BTW, .5 is the lowest it should be for good results from a sealed box, and for that matter .3 the lowest for a good low end from vented.

 

[Rusty the Scoob]

I'm not sure I understand the Qts parameter. This is what Wikipedia has to say:

Qts A unitless measurement, characterizing the combined electric and mechanical damping of the driver. In electronics, Q is the inverse of the damping ratio. The value of Qts is proportional to the energy stored, divided by the energy dissipated, and is defined at resonance (Fs). Most drivers have Qts values between 0.2 and 0.8.

So if I'm reading this correctly, a higher number means less damping, and less damping means more low end?

Hmmm. So would this driver not be a good choice? The fact that it's free is pretty strong motivation my world but I don't want to build a bad cab, either. I'm also not looking for ultimate depth, more like low-mids.

 

[billfitzmaurice]

Simply put low Qts drivers are more sensitive, but that sensitivity is gained at the expense of bass response. High Qts drivers have good bass response, but at the expense of sensitivity. With a vented cab best results generally come with a Qts of .3 to .4, sealed with a Qts of .5 to .7, but there are a dozen other factors at work also, so these are fairly broad generalizations.
I wouldn't be using either a 2220 or D130 for bass, as not only do they have poor low end response, they're also very shy on power handling, being displacement limited to only 50 watts or so. That was fine when 50 watts was a big amp, not so much today, unless you want something for studio use only.

 

[Rusty the Scoob]

Hmmm. I guess what I really want is a D140 or equivalent. The Weber Neomags look like a nice option, have you ever worked with those?

Thanks again for steering me in the right direction!