Let's design a 15" sealed cab

Eminence Alpha, Beta and Delta 15 have high enough Qts and low enough EPB to work in sealed boxes. Get the designs on the Eminence site.

 

Beta 15 and delta 15 are considered good replacement for ampeg fliptops. Both will do fine without midrange driver but i would hesitate using just one because of their modest xmax. Delta 15lfa and definimax 4015 would make a quite potent 1x15 sealed cab, both require some kind of midrange driver.

 

Designing a sealed cab isnt that involved really, there is a lot of room for the error considering you are using the right driver.
Affordable, easy to build, relatively small and light one-hand carryable 1x15 sealed cab solution? Make it 2cuft net, out of 1/2 ply, brace it well and use heaps of polyfill stuffing. Three drivers come to mind, all three will work @ 2cuft. beta 15, delta15a and delta 15 lfa.
Delta 15a will sound brightest, delta 15lfa will go lowest and loudest but sound darker doing so. Beta 15 is a compromise between the two.

 

go on then.....

 

Would there be much of a market?

 

This is an interesting project, but there are some performance aspects that may be worth considering.

1) The bass is strongly peaked: 8 db at 90 Hz. The peak is fairly broad, so that fundamentals and harmonics between about 70 and 140 Hz will be reproduced at a much higher level than the remaining harmonics.

2) With a system Q (Qtc) around 2.7, the bass resonance of the system is poorly damped. Notes definition will be extremely poor (beyond soft, fat, mushy and pillowy) and low notes will audibly boom.

3) Power handling will be fine until the system resonant frequency (around 110 Hz), below which excursion limited power handling will plummet: less than 100w between 70 and 95 Hz. There is a lot of energy in that range.

People need to decide what they want performance-wise in a cab and design accordingly. That would include the tonal quality of the bass (articulate, well defined, rich, fat, etc.), bass extension (do you want the deep fundamentals, or how deep do you want fundamentals to be reproduced), and how much power must the cab take to produce the volume you need (how big is the venue, and how loudly do you play). You also need to consider the mids and highs (will a mid or tweeter be needed), and their impact on the tone of the cab.

Until the above questions are answered there is little point in working on a design (except maybe to learn, and that is a good one!).

 

Better than the alpha 15A design, but no cigar. There is a 5 db peak that is due to a poorly damped system bass resonance (high Qtc). The low notes will have poor definition, and will sound soft, obese and pillowy. Tone quality will be similar to a lot of 115 combos: thumpy, poor note definition, congested, fart-out prone. What do people want from this project performance-wise?

 

If there is a peak in the bass much over 3 db, the resonance is poorly damped and note definition will suffer. Sealed or ported, it doesn't matter. Stuffing the cab with acoustic insulation will dampen it a little, but at the expense of musical dynamics - a heavily stuffed cab sounds lifeless.

 

Let's not. The last sealed 15 I played was a Polytone Mark III Teeny-Brute I had in undergrad in the early '80's. There is effectively no extension below the resonant frequency of the driver. There have been so many advances in technology in not only cabinet design, but crossover and driver design, including strides in tailoring the compliance of the cone material itself, that a closed cabinet is a regression.