[QUOTE=valhallax;1845989]Follow the 6 moons link to the article.Quote:
Originally Posted by alancohen
Printable View
[QUOTE=valhallax;1845989]Follow the 6 moons link to the article.Quote:
Originally Posted by 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:
http://www.hostboard.com/forums/f700...tl-416-8b.html
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?
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.
1st sim = ~30 Hz tuning/0.75? long vents, 2nd sim = ~24 Hz [Fs]/4? long vents, so this is the typical tuning range.
GM
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?
http://www.audiokarma.org/forums/att...6&d=1359164872Quote:
Originally Posted by alancohen
Here's a clue ;
This is a look at the bottom of an M19 horn module .
:)
Ahhhhh, ha!!Quote:
Originally Posted by Earl K
So why go through all that extra cabinetry if the airspace is linked anyway? :confused:
Easier Construction ? MAGIC ! Engineered by Design ?Quote:
Originally Posted by alancohen
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 ) .
:)
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
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...
http://www.hostboard.com/forums/hbmc...2013/01/24.jpg
A pretty pair of a7's would look nice there.....just saying.
Can't argue with that. There is something very classic (and sexy) about an A7 cabinet...at least to a guy. I don't think women get the same charge out of them. Thankfully, I do not have to worry about that.Quote:
Originally Posted by cradeldorf
Building these would give me the option of swapping to a 511 and crossing over lower if desired. In my small space I don't think that will be the case, but it's nice to have the option.
http://www.hostboard.com/forums/hbmc...2013/01/25.jpg
The Magnificents were designed with the WAF factor in mind. :)
So we arrive at the end of an era and this thread has now come full circle. It's hard to fathom what has happened in the relatively short time that I first posted here. Thanks to everyone that contributed to my education and subsequently, the glorious sound I know find myself bathing in on a daily basis.
With my aquisition of the 604Ds, A6s and A7s I just don't have room to store another set of speakers. I am joining the group of you that have passed on their Heathkit/Valencias and will likely regret it some day. They're up on CL for $1050, but if an Altec Users Board member wants them we can talk.
{sniff...sigh}
Alan are you selling the 802-8G's that you just bought from GPA for those Valencias too ? Or are you selling the 806's with them ? I would keep those ! :Nodding:
I put back the 806As. The 802Gs are nice and warm in a drawer. I might end up using them with the 828 cabs w/ 511s and go A7 set up. Or if I decide on the 288s for the LR, I will build some 805B multicells and go A5. The 288s are a bit much for the space, but they are very seductive.Quote:
Originally Posted by Altec Best
Alas, they are gone. It's only been 10 minutes and separation anxiety is already setting in. They will be missed.
That didn't take too long.
I listed them for $1050 and took $950. I received quite a few emails. One from a guy in S Korea offering to pay the freight!Quote:
Originally Posted by Altec Best
At the end of the day I sold them for what I paid for them, sans a few caps. And it looks like they're getting a nice new home. I vetted him out that he plans on keeping them together and not cannabilizing the parts.
Just got a pair of these... recapped the crossovers and they sounded great