GM-416-8B MLTL Corner Cabinet

[GM]

FYI, the Vid spec on the far right is the amount of volume the driver takes up in a cab: http://alteclansingunofficial.nlenet.net/Thiele-Small.html

GM

[VolvoHeretic]

FYI, the Vid spec on the far right is the amount of volume the driver takes up in a cab: http://alteclansingunofficial.nlenet.net/Thiele-Small.html

GM

Thanks GM, but your link is busted.

So, after rereading the first post again, and with an overall height of 40" and an internal height of 38.5", and with my bracing so far, I wind up with an internal net volume of 23.69 cu. ft. I will have to increase the speaker depth a little.

GM, care to critic my design?

[srivenkat]

Thanks GM, but your link is busted.

So, after rereading the first post again, and with an overall height of 40" and an internal height of 38.5", and with my bracing so far, I wind up with an internal net volume of 23.69 cu. ft. I will have to increase the speaker depth a little.

GM, care to critic my design?

VolvoHeretic,

Please note from the first post, the dims (id) are Volume = ~25.25 ft^3 gross, so ~24 ft^3 net MLTL
L = 58.5"
W = 38.5"
Horn down = 4.75"
Driver down = 22"
Therefore horn/driver ctc spacing = 17.25"
Drivers - GPA 416-8B, GPA 802-8G, Altec 811B horn, GPA N1200-8A XOver (or other passive XO)

Thank you,
Sri

[VolvoHeretic]

Thanks Sri, with 26.5" depth, I get exactly 24.39 cu ft. I just need to know what the volume of the 811B is.

[GM]

I just need to know what the volume of the 811B is.

Fixed previous specs broken link.

http://www.lansingheritage.org/images/altec/plans/1968-enclosure/page04.jpg

GM

[VolvoHeretic]

Fixed previous specs broken link.

http://www.lansingheritage.org/images/altec/plans/1968-enclosure/page04.jpg

GM

Thanks GM. So I have 416-8B = 0.25cf, 811B = 0.19cf, 802-8D = 0.026cf = 0.466cf total components.
Vb = 24.5859cf - 0.466cf = 24.1199cf net. I will recheck my math tomorrow.

[srivenkat]

Thanks GM. So I have 416-8B = 0.25cf, 811B = 0.19cf, 802-8D = 0.026cf = 0.466cf total components.
Vb = 24.5859cf - 0.466cf = 24.1199cf net. I will recheck my math tomorrow.

VolvoHeretic,

Thank you.

Here is the link from GPA spec sheets
416-8B - http://www.greatplainsaudio.com/down...ec%20Sheet.pdf
802-8G - http://www.greatplainsaudio.com/down...ec%20Sheet.pdf

Please note the Vent details from the first post,

from GM
"Vent = [1] 5" dia. x panel thickness [0.75" assumed]/side for ~25 Hz Fs or can both be on one side horizontally.
Recommend using a removable baffle to try up to [1] 9" dia. vent hole/side for more typical Altec tuning or just start big and add smaller hole discs till it sounds right. For all I know, having different size holes in each side may work best overall since the room dominates and SET tube amps can be pretty finicky about impedances not ruler flat, but the passive components to flatten a low Fs bass driver's impedance are large, not cheap. "

Any thoughts/inputs on sides tapered box - the rectangular dim came to 58.5HX38.5WX18.5D

Again, great drawings thank you so much for sharing these.

-Sri

[VolvoHeretic]

Sri, here is a simple 22.5 deg. taper 40"x34" compared to GM's original design. The taper projects out into the room quite a bit more. After all of these corner variations, I would have to say that GM's design uses up the least floor space and allows the easiest adjustment and is probably (undoubtedly) the easiest to build (all angles are the same, both sides of the cabinet are the same, and both cabinets are the same).

[srivenkat]

Sri, here is a simple 22.5 deg. taper 40"x34" compared to GM's original design. The taper projects out into the room quite a bit more. After all of these corner variations, I would have to say that GM's design uses up the least floor space and allows the easiest adjustment and is probably (undoubtedly) the easiest to build (all angles are the same, both sides of the cabinet are the same, and both cabinets are the same).

VolvoHeretic,

Thank you. Looks like taper may not be the right option. Few of basic questions,

(1) Your reference to GM's original design is 45 degree version? (I was pretty much set on this one as it was easier to build and I am fine to be slightly away from the sweet spot)
(2) I understood the best option is the curved one which allows the easiest adjustment, please correct me otherwise.
(3) Finally, what's your input on a rectangular one? Simple to build and I can move from corner but use corner traps, etc. Would it be a bad choice?

Please bear with my basic questions. And, thanks a lot again.

-Sri

[VolvoHeretic]

VolvoHeretic,

Thank you. Looks like taper may not be the right option. Few of basic questions,

(1) Your reference to GM's original design is 45 degree version? (I was pretty much set on this one as it was easier to build and I am fine to be slightly away from the sweet spot)
(2) I understood the best option is the curved one which allows the easiest adjustment, please correct me otherwise.
(3) Finally, what's your input on a rectangular one? Simple to build and I can move from corner but use corner traps, etc. Would it be a bad choice?

Please bear with my basic questions. And, thanks a lot again.

-Sri

Hi Sri,
1) Yes GM's original 45 degree design offers the least intrusion into the room as it is rotated (I think).

2) I have worked for a short time in a cabinet shop, so I am biased towards the most complex shape possible. However, if this is your first build, a rectangle will be simplest and the 45 degree next.

3) A plain rectangle will work fine, but in my experience with a similar width room, spaced as wide as I can get them is best for me. I will draw it up and post it so you can see.

Here are my 28"x42" rectangular speakers in my room, I actually have to pull them out into my room so that they line up in an arc with my center channel: