New Heathkit AS101 owner - First post.

[alancohen]

[QUOTE=valhallax;1845989]

His dimensions are deeper than wide.
whose dimensions?

Follow the 6 moons link to the article.

[alancohen]

So...this weekend I'll be getting moving boxes organized in my garage and my shop up and running. I have two projects in the queue:

1) acoustic panels for my listening area and

2) designing my new cabinets

I just picked up some of this stuff for both:

16 in. x 48 in. UltraTouch Denim Insulation Multi-Purpose Roll (6-Pack)-60306-16482 at The Home Depot

It's 2" thick insulation that I hear makes a pretty good sound absorber. Since it's 16 x 48" I'll be making some 16 x 48" acoustic panels as well as some 32 x 48" panels to mount on the ceiling, fireplace and back walls.

But I think I'll also use it to line my cabinets.

That brings me to cabinet design. I've poked around and found quite a few threads on the subject. Basically I'm thinking along these lines:

GM's MLTL with 416-8B

I like the idea of an MLTL cab, but do I have to go 52 3/4" high? I'd like to mount the 811s on top and have their centerline at ear level...maybe 38-40" off the floor. I could make the cabs taller and angle the horns down, but I think I'd prefer them on plane together.

Also, I see internal volumes all over the place for 15" Altec speakers...from 6.5 cuft for model 19s to 16cuft and up. I'd like to stay with about a 9 cuft at most.

We don't need to rehash everything here. Can someone distille the past fews years cab threads and direct me to a few that might fit my siituation?

[GM]

IME, the denim?s specs implies it?s too absorbent for a MLTL. O-C 703 1? duct board same as what Altec sometimes used works well, while others prefer to stuff with loose polyfil. If you can split the denim in half it would probably be OK.

The M19 is ~ 8.35 ft^3 net. To get more bass extension requires more net Vb, so to get down to a low Fs with authority and/or to keep from having a ?boomy?/?flabby? bass with a high output impedance requires a huge cab due to the 416?s specs.

This is why I always recommend building the largest cab one can ?afford? if for no other reason than it allows some extra tuning flexibility.

A MLTL?s path-length is restricted not by it height per se, but by its height x its depth and any adjustment required to fit the driver in, but to fold it in half with a divider/vertical brace, it needs to be 23.25? o.d. deep for the 416A and dictates the dual 4? vents will normally exit the rear side corner[s] or back 13.1? i.d. up from the bottom.

If we split the difference and design based on a 39? ear height, a 34.25? o.d. MLTL height equates to a ~65.5? one fold path-length based on a ?? thick panel construction.

Combined with the M19?s 30? o.d. width, it will be near 11 ft^3 net.

All dimensions are approximate and sims are minimally damped.

1^st sim = ~30 Hz tuning/0.75? long vents, 2^nd sim = ~24 Hz [Fs]/4? long vents, so this is the typical tuning range.

GM

[alancohen]

I'm confused. Plans on the net show the Model 19 lower cab to be 30x24x19. If I plug those OD dimensions into this volume calculator, and assuming 3/4" panels you get 6.49" of internal volume.

Speaker Box Volume Calculator / Designer

What am I doing wrong?

[Earl K]

I'm confused. Plans on the net show the Model 19 lower cab to be 30x24x19. If I plug those OD dimensions into this volume calculator, and assuming 3/4" panels you get 6.49" of internal volume.

Speaker Box Volume Calculator / Designer

What am I doing wrong?

Here's a clue ;

This is a look at the bottom of an M19 horn module .

[alancohen]

Here's a clue ;

This is a look at the bottom of an M19 horn module .

Ahhhhh, ha!!

So why go through all that extra cabinetry if the airspace is linked anyway?

[Earl K]

Ahhhhh, ha!!

So why go through all that extra cabinetry if the airspace is linked anyway?

Easier Construction ? MAGIC ! Engineered by Design ?

Seems, GM is pretty convinced that it simulates a ( "leaky" ) quasi-MLTL, setup of sorts .

I'd love to see data supporting the theory ( so it can be put to applied use ) .

[GM]

Like most things speaker design related, it's well understood ancient history and easily simmed in all the versions of LspCad AFAIK and of course AkAbak or similar programs. I forget who did the initial work, but nowadays it's usually referred to as a double bass reflex [DBR], though there's three different variants of which the M19 is the simplest variant used to improve driver damping in the 1/2 octave above a low tuning where the driver is most vulnerable to over excursion.

In short, the horn cavity plus spacer acts as a band stop filter [Helmholtz resonator], so nothing 'leaky', just good old applied engineering, once again proving the old adage that those who don't learn from history are doomed to repeat it : http://users.cms.caltech.edu/~ps/All.pdf

Regardless, a well done MLTL will provide better damping overall over a wider BW, so DBR loading is best left to improving BR power handling. Note too that it creates a notch in the mid-bass as the trade-off same as what occurs with a MLTL if the vent is located close to the driver to achieve this type of notch filter, so no 'free lunch'.

GM

[alancohen]

Call me crazy, but if I'm going to go 30" wide and 40" high, and considering my power source being fairly low wattage tube amps, I'm actually considering "just" building a pair of 828s. "Considering" might be the operative word, but I like a good project and my woodshop is now a 2.5 car garage with a big double door to open when the weather gets warm to let all the sawdust out.

I do have the room...

[cradeldorf]

A pretty pair of a7's would look nice there.....just saying.