GM-416-8B MLTL Corner Cabinet

[VolvoHeretic]

Sorry I haven't had much time to work on the speaker design, I've been dealing with a couple of family medical emergencies. Here are my latest ideas on the boxes. These drawings show two front removable panels, a sub-baffle and a finished main baffle.

The sub-baffle would be attached to triangular gussets with wood screws spaced about 4" o.c. and the main baffle would attach to the sub-baffle with 3/4" aluminum angles along the perimeter and also at the speaker and port holes behind the cloth cover trim rings.

The aluminum angles would attach to the sides of the main baffle and the side of the cabinet with wood screws and the two angles would be bolted together with pan head bolts. I am thinking that the a sheet of thin laminate flooring foam underlayment sandwiched between the two panels would keep them from rattling. The angles would then be covered with wood quarter round.

I have not calculated the net volume but guess the depth of the box will have to be a little deeper, like maybe 28".

[srivenkat]

Sorry I haven't had much time to work on the speaker design, I've been dealing with a couple of family medical emergencies. Here are my latest ideas on the boxes. These drawings show two front removable panels, a sub-baffle and a finished main baffle.

The sub-baffle would be attached to triangular gussets with wood screws spaced about 4" o.c. and the main baffle would attach to the sub-baffle with 3/4" aluminum angles along the perimeter and also at the speaker and port holes behind the cloth cover trim rings.

The aluminum angles would attach to the sides of the main baffle and the side of the cabinet with wood screws and the two angles would be bolted together with pan head bolts. I am thinking that the a sheet of thin laminate flooring foam underlayment sandwiched between the two panels would keep them from rattling. The angles would then be covered with wood quarter round.

I have not calculated the net volume but guess the depth of the box will have to be a little deeper, like maybe 28".

VolvoHeretic,

Absolutely no problem VolvoHertic and hope things are better for you now. Thanks a lot for your drawings ? every bit of it is so helpful for me.

Very detailed explanation about the two baffle arrangement, great! So, for me now there are two options to consider based on the difficulty level.

Option 1 (my current choice) ? Using a 1?X2? frame inside and have the front baffle screwed to this with neoprene gasket between the frame and back side of the front baffle
Option 2 (little difficult for me) ? Using two baffle as you described here. Besides the aluminum angles bolting, around speaker driver cavity and port section has to be screwed in?

Option-1 is relatively simple for me. What would be the advantage of going with option-2 with two baffles?

Also, I see a circular spot in the middle of the diagram close to the horn driver - from the top view. Is that representing driver distance position?

Again, thanks a lot.

-Sri

[VolvoHeretic]

Thanks Sri, my mother-in and brother-in-law where driving home from the grocery store and in the dark clipped the corner of a parked 6000lb SUV with their little 2500lb Toyota Rav4, spun sideways and flipped over next to it. They where only going 25-30mph, but weren't wearing their seatbelts and slammed into the steering wheel and windshield-the airbags did not deploy which might or might not have been a good thing. Brother only needed 9 stitches in his eyelid where his glasses cut it, but Mom broke her femur, ribs, jaw, palate, and eye socket and will have a long recovery ahead of her. WEAR YOUR SEATBELTS!!!! even if just to the store.

Anyway, that round thing is the vertical 1.5 or 1.75" pine handrail top and bottom panel stiffener. I would also cut two 4"x4" pieces of plywood, cut the handrail shape out and using PL400, glue the heck out of them to get a lot of square inches of gluing surface with the vertical and the base and cap panels.

I figured that since there are two pieces of plywood behind the woofer and ports, one full size secondary-baffle would be stronger, and easier to make removable. Plus, I am trying to get away from any visible exposed or plugged screws. I also want to make everything as strong as possible because I know how much energy these speakers can generate at 110db 36 feet away, mine worked all of the nails out of the flooring 10' out into the room.

[srivenkat]

Thanks Sri, my mother-in and brother-in-law where driving home from the grocery store and in the dark clipped the corner of a parked 6000lb SUV with their little 2500lb Toyota Rav4, spun sideways and flipped over next to it. They where only going 25-30mph, but weren't wearing their seatbelts and slammed into the steering wheel and windshield-the airbags did not deploy which might or might not have been a good thing. Brother only needed 9 stitches in his eyelid where his glasses cut it, but Mom broke her femur, ribs, jaw, palate, and eye socket and will have a long recovery ahead of her. WEAR YOUR SEATBELTS!!!! even if just to the store.

Anyway, that round thing is the vertical 1.5 or 1.75" pine handrail top and bottom panel stiffener. I would also cut two 4"x4" pieces of plywood, cut the handrail shape out and using PL400, glue the heck out of them to get a lot of square inches of gluing surface with the vertical and the base and cap panels.

I figured that since there are two pieces of plywood behind the woofer and ports, one full size secondary-baffle would be stronger, and easier to make removable. Plus, I am trying to get away from any visible exposed or plugged screws. I also want to make everything as strong as possible because I know how much energy these speakers can generate at 110db 36 feet away, mine worked all of the nails out of the flooring 10' out into the room.

Very sorry to hear that, wishing both of them a speedy recovery. Hope you and your family come out of the shock slowly. Please take care.

If two ply would be required for the front baffle, I can sandwich for an 1.5" thick removable front baffle but use the same framing with neoprene approach to simplify. I can cut the woofer cavity on the sandwiched boards for flush mounting the drivers. For the port, back panel will have the larger cut and front panel board will be mounted on that with neoprene. Would this work? Along with this 1.5 inch, there will be veneering on top of it.

The other thought for the Port - Have a 9" port on the panel and cut different size (6", 5" ports) inches wooden ring which can be made to tight fit. Would this work?

I got the hand rail connecting top and bottom. But, not clear with 4"X4" plywood pair. You are suggesting have ply in between top/bottom board and handrail so, I can have them glued well? For the internal bracing, GM suggestions will be coming we can decide on this along with that.

Thank you,
Sri

[VolvoHeretic]

Sri, thanks for the kind words of encouragement. My 84 year old mother-in-law is in a drug induced coma and a ventilator, but she needs to be weaned off of it and start breathing on her own. It is still touch and go and she is developing congestive heart failure which is fluid surrounding the heart.

Anyway, it appears that pine hand railing comes in 1.5" diameter and the 4x4 ply plates will have that same size hole drilled in them so the railing is the full inside box height and the plates slide over it and will act like a large gusset and increase the gluing surface area from 1.75 to 16 sq in plus the .75" depth.

I envision using 2x2's cut diagonally into 1.5x1.5 triangles to also give a large gluing surface area and I would screw the removable panels to them with 1.5" #12 screws @4"O.C. and I suppose a highly contrasting screw hole plug could look acceptable (like cherry plugs on a light birch finish) and in that case, you could go back to the original drawing with just the areas for the speaker(s) and ports doubled up.

I still don't know where to place the ports and I don't know what affect having a stepped thickness near the ports will have on their function. If you could router a step into the port board outer diameter, you could leave that area just a single thickness and just change out different circles with various diameter ports.

Let me do some more drawing.

James

[GM]

Greets!


Bummer about your family. Hope your mom's getting [a lot] better medical care than me and at least stable enough for ya'll to be able to somewhat enjoy this beginning of the holiday season.


Anyway, this project has moved far afield from the original and either I forgot stuff in my design considerations/trade-offs or I guess chose to selectively ignore them to minimize the acoustic trade-offs since I want a ~all encompassing tutorial to point to in the future.


The vents were to be on the lower front sides like Billfort's and for the dual driver/511 combo I chose to put the horn in the cab since it would be too far away from the woofers with the desired XO [point] and recessed ~like the M19's, which has been already worked out for us by Heathkit [Altec?] many decades ago.


Not much tech info per se, but I did calculate it close enough way back when using the sales brochure and peering through the grillcloth of one, though couldn't find it it in the relatively few notes I still have available and can't recall ATM if I actually built one, but these should suffice:

http://www.heathkit-museum.com/hifi/hvmhh-1-c.shtml

https://www.google.com/search?q=heathkit+legato&rlz=1C1AVNG_enUS675US675& espv=2&biw=1044&bih=514&tbm=isch&tbo=u&source=univ &sa=X&ved=0ahUKEwismeSD063QAhUCOSYKHRM0BHMQsAQIIQ& dpr=1.1

http://i40.tinypic.com/2vvkilh.jpg

https://s-media-cache-ak0.pinimg.com/236x/7b/82/f4/7b82f49c59a0ecb3539c6ce3c7abf2ac.jpg

If a top mounted horn is used, then the woofers ideally need to be at the extreme top as the Lp is too close for good summation, though the woofer's output will theoretically sound audibly different in an A/B comparison to the Legato variant.


More to come as time permits.........and hope ya'll have an enjoyable, filling, profitable [if applicable] holiday weekend if I don't make it back before then.


GM

[srivenkat]

Greets!


Bummer about your family. Hope your mom's getting [a lot] better medical care than me and at least stable enough for ya'll to be able to somewhat enjoy this beginning of the holiday season.


Anyway, this project has moved far afield from the original and either I forgot stuff in my design considerations/trade-offs or I guess chose to selectively ignore them to minimize the acoustic trade-offs since I want a ~all encompassing tutorial to point to in the future.


The vents were to be on the lower front sides like Billfort's and for the dual driver/511 combo I chose to put the horn in the cab since it would be too far away from the woofers with the desired XO [point] and recessed ~like the M19's, which has been already worked out for us by Heathkit [Altec?] many decades ago.


Not much tech info per se, but I did calculate it close enough way back when using the sales brochure and peering through the grillcloth of one, though couldn't find it it in the relatively few notes I still have available and can't recall ATM if I actually built one, but these should suffice:

http://www.heathkit-museum.com/hifi/hvmhh-1-c.shtml

https://www.google.com/search?q=heathkit+legato&rlz=1C1AVNG_enUS675US675& espv=2&biw=1044&bih=514&tbm=isch&tbo=u&source=univ &sa=X&ved=0ahUKEwismeSD063QAhUCOSYKHRM0BHMQsAQIIQ& dpr=1.1

http://i40.tinypic.com/2vvkilh.jpg

https://s-media-cache-ak0.pinimg.com/236x/7b/82/f4/7b82f49c59a0ecb3539c6ce3c7abf2ac.jpg

If a top mounted horn is used, then the woofers ideally need to be at the extreme top as the Lp is too close for good summation, though the woofer's output will theoretically sound audibly different in an A/B comparison to the Legato variant.


More to come as time permits.........and hope ya'll have an enjoyable, filling, profitable [if applicable] holiday weekend if I don't make it back before then.


GM

GM,

Thanks for the details. I was under the impression that single woofer configuration will have the horn in the cab but the dual will have it on top of the cab. For both, I can have the horn (511 and 811) inside the cab.
For 811B horn (total height - 8-5/8") - you have "horn down - 4.75"
So, I guess for 511B (total height - 10-5/8") - I should add 2" down based on its height. This requires woofers offset to go relatively 2" down?

For Port - you have given the details....
"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."

Thanks and have a great holiday weekend.

-Sri

- - - Updated - - -

Sri, thanks for the kind words of encouragement. My 84 year old mother-in-law is in a drug induced coma and a ventilator, but she needs to be weaned off of it and start breathing on her own. It is still touch and go and she is developing congestive heart failure which is fluid surrounding the heart.

Anyway, it appears that pine hand railing comes in 1.5" diameter and the 4x4 ply plates will have that same size hole drilled in them so the railing is the full inside box height and the plates slide over it and will act like a large gusset and increase the gluing surface area from 1.75 to 16 sq in plus the .75" depth.

I envision using 2x2's cut diagonally into 1.5x1.5 triangles to also give a large gluing surface area and I would screw the removable panels to them with 1.5" #12 screws @4"O.C. and I suppose a highly contrasting screw hole plug could look acceptable (like cherry plugs on a light birch finish) and in that case, you could go back to the original drawing with just the areas for the speaker(s) and ports doubled up.

I still don't know where to place the ports and I don't know what affect having a stepped thickness near the ports will have on their function. If you could router a step into the port board outer diameter, you could leave that area just a single thickness and just change out different circles with various diameter ports.

Let me do some more drawing.

James

James,
Very sorry to hear about the mom's situation. Hope things get better for you and your family.

-Sri

[VolvoHeretic]

Thanks for the support guys, here is the latest. I moved the ports to the utmost bottom and left/right, should I pick 7th harmonic points or what? If the baffle is step routed .375"x.75" you can have several port baffles mirror routed, cut 10 or so different diameter port holes and interchange those to come up with the ultimate port dimensions and even do A/B testing.

I want to make the front baffle two piece - one for the horn and the second for the main woofer and port. These could be separated with a piece of speaker/port matching brass looking 1/4 bar stock. I will evenly space and dimension the exposed baffle screws which need to be drilled with a good recessed pilot hole drill bit with the correct plug, chamfer, and pilot hole all-in-one step unit. If (and I hope)(maybe insist if GM's and my names is published on the blueprints) a brass look is used for all metal parts (speaker cloth cover rings) including the exposed screws for the horn are used, brass plugs could also be used to cover the screws if not actual exposed brass screws. (I love brass/gold )

Sri, the plywood can be nailed together as you assemble the box with a brad nailer using finish pin nails. I can't remember what length would be best, but 2.5" comes to mind. I would start at the front and work your way to the rear corner, making adjustments as you go. After every thing is glued and pinned together I would also use cinch straps to suck everything up snug. MAKE SURE TO KEEP EVERYTHING SQUARE, PLUMB, AND LEVEL!!!!

Since the base and cap panels will be free cut, mark everything out on your plywood top and bottom panels using a mechanical .5mm pencil using hard hb lead for the finished outside dimensions, cut those panels an 1/8" oversize beyond the front panel on the rear panel sides and after the vertical sides are fit, glued, nailed up, and dried, use a trim router bit to trim up the base and cap to match the actual sides wherever they eventually wind up (actual resulting fit is not that important, but final fit is crucial to the finished product(it is what it is). In other words, try to follow the outside dimension numbers, try to make sure the outside miters touch first and if need be narrow the miter angels to make sure the outside of the miters are the first parts touching. This will be a living, breathing contraption.