GM-416-8B MLTL Corner Cabinet

**srivenkat** · October 31st, 2016, 09:37 PM

Originally Posted by VolvoHeretic

I'd love to Sri, I should have it whipped out around midnight, first I have to open the doors and play scary Halloween music at 110db and lure those little kids in for candy.

That must be fun! Have a nice time, thank you.

-Sri

- - - Updated - - -

Originally Posted by GM

Thanks, and a quick sketch with a protector [sic] says I guessed right at 22.5 deg/20 ft..

GM

edit: make that 'protractor'

GM,

Just a question, looking at these angles, do you think keeping it rectangular will provide more option for freely move/turn towards the right length sweet spot? I believe the rectangular will keep the current L X W but the depth will change. Or, am I wrong?

Thank you,
Sri

**VolvoHeretic** · November 1st, 2016, 01:11 PM

Ok, sorry it took longer, we had company and had too much fun last night.

Srivenkat's Corner Speaker-22.5x67.5-1.jpg

Srivenkat's Corner Speaker-Floor Plan-4.jpg

**srivenkat** · November 1st, 2016, 01:38 PM

Originally Posted by VolvoHeretic

Ok, sorry it took longer, we had company and had too much fun last night.

Srivenkat's Corner Speaker-22.5x67.5-1.jpg

Srivenkat's Corner Speaker-Floor Plan-4.jpg

Hi VolvoHeretic, Thanks a lot for the drawing, nice you had some fun

-Sri

GM · November 1st, 2016, 06:34 PM

Nice adjunct to this tutorial of sorts: The Emperor’s New Stereo | Bob McCarthy's Blog

GM

GM · November 2nd, 2016, 01:53 AM

FWIW, back at post #24 I meant to add an edit WRT to cab shape: GM-416-8B MLTL Corner Cabinet

That said, all this room mode, speaker shape musings has turned out to be just a bit of a tutorial that's been needed here for a long time and in some edited form be made a must read 'sticky' before posting speaker design request IMNSHO since after viewing your pictures it's obvious that acoustically your room is anything but a simple 15x30x9 ft rectangle and your floor plan doesn't reflect what's in the pictures, so not a complete waste of everybody's time, but at this point I recommend a curved back to fit the desired net [Vb] and after that it really doesn't matter too much as any near boundary reflections can be dealt with DIY acoustic panels, absorbant tiles, thick rug hangings, 'thick' plant[s] arrangements, etc., determined impirically by ear or 'map' it with computer 3D room measuring software.

To wit: The two? wall offset 'shelf', which probably has little impact on the 1st, 3rd harmonics, will set up it's own lopsided 'secondary room insert' harmonic structure to comb filter with the room's primary 3D one.

Acoustically much worse though is the stairwell that acts as either a low tune Helmholtz resonator or acoustic bandstop filter depending on whether the upstairs door is open or closed, both with a Ql [loss] dependent on how well it seals; so on the one hand it will be a 1/2 WL resonator [vent] tuning the room to some other frequency with its own superimposed 1/4 WL TL pipe action, i.e. make the room a relatively high tuned MLTL in effect [judging by its visible length, net [Vb]; or leave the room a 1/2 WL resonator with a hugh notch in its response somewhere in the [sub?] bass BW.

In ~short and all things considered, if a curved cab is too much hassle, then some form of tapered is desirable, though just make them symmetrical and if they do wind up in the corners, then fill the rear cavity it creates with some form of bass-trap such as rolls of fiberglass attic insulation with holes in its plastic packaging.

GM

**srivenkat** · November 2nd, 2016, 11:52 AM

Originally Posted by GM

FWIW, back at post #24 I meant to add an edit WRT to cab shape: GM-416-8B MLTL Corner Cabinet

That said, all this room mode, speaker shape musings has turned out to be just a bit of a tutorial that's been needed here for a long time and in some edited form be made a must read 'sticky' before posting speaker design request IMNSHO since after viewing your pictures it's obvious that acoustically your room is anything but a simple 15x30x9 ft rectangle and your floor plan doesn't reflect what's in the pictures, so not a complete waste of everybody's time, but at this point I recommend a curved back to fit the desired net [Vb] and after that it really doesn't matter too much as any near boundary reflections can be dealt with DIY acoustic panels, absorbant tiles, thick rug hangings, 'thick' plant[s] arrangements, etc., determined impirically by ear or 'map' it with computer 3D room measuring software.

To wit: The two? wall offset 'shelf', which probably has little impact on the 1st, 3rd harmonics, will set up it's own lopsided 'secondary room insert' harmonic structure to comb filter with the room's primary 3D one.

Acoustically much worse though is the stairwell that acts as either a low tune Helmholtz resonator or acoustic bandstop filter depending on whether the upstairs door is open or closed, both with a Ql [loss] dependent on how well it seals; so on the one hand it will be a 1/2 WL resonator [vent] tuning the room to some other frequency with its own superimposed 1/4 WL TL pipe action, i.e. make the room a relatively high tuned MLTL in effect [judging by its visible length, net [Vb]; or leave the room a 1/2 WL resonator with a hugh notch in its response somewhere in the [sub?] bass BW.

In ~short and all things considered, if a curved cab is too much hassle, then some form of tapered is desirable, though just make them symmetrical and if they do wind up in the corners, then fill the rear cavity it creates with some form of bass-trap such as rolls of fiberglass attic insulation with holes in its plastic packaging.

GM

GM,

Thank you for taking time to go thru the diagram/pictures. I tried my best to prepare the room layout. I hate to waste anyone time here but pleased to know this could be a useful tutorial material.

I need to read few more times to understand “stairwell impact” just to educate myself.

From the cabinet options,

Option 1 - Curved Cabinet – Tough one! I won’t be able to build this myself. I don’t want to give up but, I will talk to few cabinet makers and see the possibility – will try to keep 58.5HX38.5W - constant and building a curved cabinet for the volume (24 cu.ft). Based on the initial dim, can I keep the D1 (9.75”) and have a curved back?
While building the 825 cabinet I bought 3/8” thick flexible ply but those are not BB – if I can use 3/8” non BB then sandwiching 2 of this MAY BE possible. I am not sure to bend the BB (3/4”). Anyways, I will talk to the cabinet maker here.

Option 2 – Some Form of Tapered – This sounds like doable by me, hope I am thinking right otherwise please correct,
- Sides tapered: I can extend bottom/top width 2 inches, reduce top/bottom appropriately and have the sides tapered.
Are there any other options or preferable choices here?

Option 3 – Rectangular – Assuming, I can use acoustic panels, absorbent tiles, and thick rug hangings. Can this still be an option?

Again, thanks a lot for your help.

-Sri