Standard 12" speaker cut-out dimensions--any such thing?

[Rhodesplyr]

I've been trying out some creative re-use of a phonograph stand my grandfather made for my brother years ago as an open-backed 12" speaker cabinet. Its baffle was already cut out for a 12" speaker, but that's turned out to be the problem. Whoever cut the circular opening made it a full 11.5" in diameter.

I used a 1961 Jensen P12 basket from a ruined speaker as a template and just barely managed to mount t-nuts around the edge of the cut out. I wanted to use t-nuts particularly because I ultimately planned to use it to house a Jensen field-coil speaker, and the field coils are pretty heavy.

Last night, I found out that the 1955 field-coil speaker won't fit; its mounting holes are closer in towards the speaker cone than they are on the later basket, so the existing baffle wouldn't ever have worked for it. It works for any Rola speaker I tried, but not the Jensen. Arrgh. This was after removing old grill cloth, painting the baffle black, etc...

Checking a Hammond A-100 speaker baffle, the cut outs are only 10 3/8" in diameter for a 12" speaker. T-nut spacing is 11 5/8" on-center.

So, is there any general standard for 12" speaker cut-outs and mounting-bolt spacing, or do you simply have to tailor the opening based on the speaker you plan to use? Sorry if this is a very basic question. I know a lot more about the conceptual aspects of speaker enclosure building than I do about the nuts and bolts--in this case, very literally....

[tubeswell]

I standardly use 11" dia. FWIW

[jmaf]

I've been trying out some creative re-use of a phonograph stand my grandfather made for my brother years ago as an open-backed 12" speaker cabinet. Its baffle was already cut out for a 12" speaker, but that's turned out to be the problem. Whoever cut the circular opening made it a full 11.5" in diameter.

I used a 1961 Jensen P12 basket from a ruined speaker as a template and just barely managed to mount t-nuts around the edge of the cut out. I wanted to use t-nuts particularly because I ultimately planned to use it to house a Jensen field-coil speaker, and the field coils are pretty heavy.

Last night, I found out that the 1955 field-coil speaker won't fit; its mounting holes are closer in towards the speaker cone than they are on the later basket, so the existing baffle wouldn't ever have worked for it. It works for any Rola speaker I tried, but not the Jensen. Arrgh. This was after removing old grill cloth, painting the baffle black, etc...

Checking a Hammond A-100 speaker baffle, the cut outs are only 10 3/8" in diameter for a 12" speaker. T-nut spacing is 11 5/8" on-center.

So, is there any general standard for 12" speaker cut-outs and mounting-bolt spacing, or do you simply have to tailor the opening based on the speaker you plan to use? Sorry if this is a very basic question. I know a lot more about the conceptual aspects of speaker enclosure building than I do about the nuts and bolts--in this case, very literally....

At some point I learned that every maker varies the baffle cutout a tiny bit, but you can make them all one size if you give up millimetric precision, which you probably don't need anyway in practice.

Speakers with 4, 6 or 8 screws also seems to be an issue, I don't know what standard they follow, if any. Since you mentioned nuts and bolts, internal nuts, those that lock themselves into the wood from the opposite side of the baffleboard, come in handy as well.

[Bill Moore]

I wonder if you could use some of the "clamp" type mounting, only from the rear? This would allow the (new) t-nuts to be moved farther out into more support.

[J M Fahey]

I use 270mm if I mount it from the back, which fits *all* speakers I know.
For front mounting I basically use 280mm (practically those 11" suggested above) but should really be adjusted a couple mm over or under depending on the particular case.
Those 11.5" are too much for any modern speaker.