Help designing an LF cabinet.

[Panomaniac]

OK, so we know the 811/806 can play down to 800Hz if I don't throw too much power at it - and I won't.
Experimenting with the crossover point isn't too hard, but changing the LF cabinet once it's built will be!

Sooo....

No worries getting the horns up to ear height. And I may use that extra space for more Vb. I think 5ft^3 could be easy to do. WOuld the 414 be happier in 5 feet?

MLTL, what's this? A transmission line? Folded box?

[GM]

Greets!

Hmm, apparently I have you confused with someone else from the DIYaudio forums, sorry about that.........

MLTL = mass loaded transmission line (aka tower or column speaker). Basically, a bass reflex (BR) assumes that its internal air has a uniform particle density whereas a MLTL has one dimension sufficiently long enough (high aspect ratio) for 1/4 WL pipe action to affect the vent's tuning (makes it shorter for a given area), which in turn allows for a larger vent (greater acoustic efficiency and damping around/at Fb).

If long enough, then yes, it can be folded as required. MJK's site has all the techno-babble explanations/simmed examples if you're interested in all the underlying theory, etc.: http://www.quarter-wave.com/

Anyway, a driver wants to 'feel' at least an air load = its Vas (ideally >4*Vas), so at 5 ft^3, its still somewhat 'constricted', but few of us have the luxury of a large enough room to house a stereo pair of infinite baffle (IB) loaded high Vas drivers.

GM

[Panomaniac]

Hi GM,
Thanks. That's me over on the DIYAudio forums.
But there are plenty of things I don't know. I suppose that I've heard lots of MLTL designs, just didn't know what they were called.

My first serious speaker project, about 20 years ago, was a Triangle FR driver in a TQWT. Wonderful life-like mids. Very little bass.

For this project I was hoping for a tried and true Altec application that could be squeezed into my living room. Not that other designs are out of the question, but you'll have to talk me into it.

[GM]

Greets!

Well, I've seen you on threads that discuss this stuff...........

Yeah, classic TLs are really 'wimpy', super smooth and well damped, but 'wimpy'.

I have better things to do with my quality time than trying to convince you. My 'job' is to give you enough info for you to potentially improve on Altec's designs since as a DIYer you can tailor the speaker's alignment, size to your room/equipment/listening preferences instead of accepting some averaged alignment that isn't even relevant in today's ultra wide BW source material 'world' without a sub and supertweeter system.

Apparently though, you want the Altec 'sound' (aka 'west coast sound'), so follow their recommendations as close as practical WRT size, shape, tuning, XO point/slope/EQ and enjoy. I for sure did decades ago and still would if I only listened to vinyl/tape through a period correct all tube front end, but I have no more interest in returning to them than I do in going back to driving a '56 Plymouth.

That said, I see you're into flea power 'T' amps, so an Altec alignment may be best since it maximizes efficiency over a narrower BW, though as always YMMV.

GM

[Art J.]

For this Project I was hoping for a tried and true Altec application that could be squeezed into my living room. Not that other designs are out of the question, but you'll have to talk me into it.

I decided to untie my hands and jump in. I believe you are going by old plans at this link.
http://www.lansingheritage.org/html/...ltec-plans.htm
What is the actual size of this small room you have?
If I had a small room where the speakers were tight to the corners, I would consider a
cabinet style like the one on the bottom of this page.
http://www.lansingheritage.org/image...ign/page24.jpg
You would be tilting them in anyway, so you could gain internal volume from the wasted space.
You could make the angle less than 45 naturally according to your listening position.

Getting the most cu-ft in your cabinets will always be an advantage but if you want a goal
to shoot for, I will offer this scenario.
Since your tuning the old school Altec"twin peaks" method, you have noticed that the larger the volume, the larger the port as shown on the charts in the Altec plans link .
http://www.lansingheritage.org/image...ure/page04.jpg
So how high is up?
In a full size Bass Reflex system, the port size is equal to the 'effective piston area' of the cone,
so in the case of the 414, its 82 sq-in. The cabinet volume required for this is off the chart with an
Fs of 30hz.
So half size cabinets were made. A 414 with a fixed port size of 40 sq-in would
require you to get about 6.5 cu-ft out of your cabs. That's if you want a genuine old school reflex
system. The half size still gives you real decent reflex action with extended lows, but the 1/4 size ones don't.
The small 'quarter port' just gives you the advantages of box tuning with little if any reflex action.
The sizes you thought as optimum, I think of as minimum........................................... .............................

[Panomaniac]

OK, see. You guys ARE talking me into it.

Art, thanks for the info. The full size, 1/2 size, 1/4 size is a nice way for me to think about it. I’ve bee poring over the charts. Corner placement is not an option for me, too bad.

GM, sorry if you feel like I was wasting your time. I DO appreciate the advice and knowledge, that's why I'm here asking questions.

Also sorry if I have come across as a "Speaker Expert" on this forum or others. I know very little about designing speakers, very little. I don't even know what the fads are, MLTL, MTM, and all the other letters. I have NEVER designed a speaker on my own; I have only followed what was already laid out.

What I do have is the good fortune to have heard, worked with and even owned some world class speakers, and of various designs. Horn, Electrostatic, Planar, etc. I do know what I like, and what works, but I wouldn't know how to design it. I can deduce some general design principles from my experiences, but don’t have the design chops.

The reason I wanted to do an Altec type design is because many of best speakers I've ever hear were based on Altec, JBL, TAD or EV drivers, often in Altec cabinets. So it seemed logical for me to pursue the Altec line of design.

Wimpy speakers, yes wimpy, wimpy. I've heard too many of them, and even owned some. Smooth and clear, but wimpy. That is what I do not want. But none of the Altec type speakers I ever heard sounded wimpy to me. Maybe I never heard the small ones.

Perhaps what would be best for me is the West Coast sound, as I listen to a lot of West Coast Jazz. And, yes - flea power amps. The speakers do need to be a test bed for my T-Amps.

What I'm hoping to learn would be; "Is a standard mid-size Altec box a good choice?" or is there a better way? If there is a better way, why is it better?

As for '56 Plymouths, well, I sold "Betty" my '63 Buick 2 years ago. My daily driver. Sure do miss the old girl.

[Art J.]

Very Good Panomaniac, you see, too many choices create stress, and there is no
shortage of choices in speaker building. What all final choices have in common is that
you glorify the strong points, and accept their shortcomings. Sounds like marriage.
You are glorifying the non-wimpy Altec's so your half way there.

I was near your location in June. (Princeville Resort). Lots of Classic cars
around with low mileage I'm sure. The drivers are always smiling for some
reason. Good Luck, Art.......

(You never gave your room size and layout)

[intotubes]

Originally posted by GM:

Apparently though, you want the Altec 'sound' (aka 'west coast sound'), so follow their recommendations as close as practical WRT size, shape, tuning, XO point/slope/EQ and enjoy. I for sure did decades ago and still would if I only listened to vinyl/tape through a period correct all tube front end, but I have no more interest in returning to them than I do in going back to driving a '56 Plymouth.

GM

<font size="2" face="Verdana, Helvetica, sans-serif">GM, exactly what are you listening to then? I would like to know what beats the pants off a pair of 19's. JBL? I was gonna build a pair of 19's but maybe they aren't the end all I thought they were.
-Mark

[bfish]

[/qb][/QUOTE]..... build a pair of 19's but maybe they aren't the end all I thought they were.
-Mark[/QB][/QUOTE]

Mark, after 30+ years of building, buying, trading and tweaking speakers, I'd have to say there is no such thing as an "end all". There's definitely no such thing as 'the best' or 'perfect'. Even if you had an unlimited budget, there's always room for improvement, so you've just got to find something you really like and call it good. Pursuit of the ultimate speakers will break a normal guy, and consume a whole lot of time you could have spent...

...enjoying listening to music.

[Panomaniac]

Art, you're right. I forgot room size and layout.

Below is a linkt to the room layout, it's small but opens up into the kitchen. Figure about 2000ft^3. Room is heavily furnished with lots of stuff on the walls (grass mats, tiki masks, paintings, etc.) Carpet and rugs on floor. Geckos on the ceiling.

There is an open window behind my head, so no rear wave. In fact all the windows in the house are always open, we ain't got air conditioning.

As you can see, I can't go into the corners because one side is the hallway, the other a door.

That's what I have to deal with, and why I need a big shoehorn to get what I want stuffed into the room. Big sound in small room. Possible?

Room Layout Image