Old work electrical boxes

You could try metal old work boxes with F brackets which are designed for that purpose.

What’s on the other side of the wall? You could always rip a strip of 2 x 4 add liquid nail it to the other side on the inside of the wall and then screw through the back of the box into the piece of 2 x 4.

Why not install the electrical box alongside a stud and screw the side of the box into the stud.

I've added 100 boxes and was done in 2 hours, including primer mudding the box tight with joint compound and fiberglass tape. 
Next day pain touchup..

A 2 x 4 wall rip a 2 x 4 to 2 1/2 inches and the width of the studs 14 1/2 usually. Check after the hole id cut.

Cut the hole for a regular single or double and slip the cut down 2 x 4s into the opening horizontally.

You need to fit the width before the liquid nails.

Put a generous supply of liquid nails on both ends. It may be a bit messy, thats fine. Secure them in place with a few screws through the sheetrock.

They are narrow enough to flip in the hole you cut. The wires will fit behind the cut down 2 X 4s

Secure the box, pull the cable (more than one wire), 

Your ready for mud. Tape, Top, Skim, and texture. Can skip the last two for a smooth finish and sand after a thick Top coat.. You want to finish it all in one day.. Hot mud.. Add a hardener.

You'll be at primer in 2 hours.. You can rough out the electrical and hook up add a cover and flip the breaker. The next day you could touch up the paint. BUT use it in 2 -3 hours..

I installed a dedicated circuit 15 yrs ago with Oyaide R1 outlet, using a remodel box. I’ve had no problem. Then too I don’t unplug my conditioner very much. Just bought a new one and didn’t have any problem plugging it in

Thanks to all who replied. I'm going to try the screw to the side of the stud approach. I think that will give the best stability.

I used metal old work boxes when I ran 3 dedicated lines for my system when I bought my present house in 2002.  I have never had any problems with the drywall caving in or cracking.  I have plugged and unplugged from the lines probably a hundred times in the past 19 years with no problems.  I am using Shunyata receptacle’s. 

Never had a problem with the plastic old work boxes. Get the screws nice and tight and it's done. Keep in mind,  If you use them, you may need to cut the tabs on the receptacle for the plate to fit. 

Ive used the metal old work box with the flip out wings. Works great and no problems after 10 years of use.

stereo5, cissado, mktracy thanks. It appears I was worrying unnecessarily about the ruggedness of the old work boxes. Glad to hear they worked well for you.

Just to wrap up...yesterday an electrician installed two dedicated lines for me. About 95 feet of 10/2 was used per line terminating in 2 gang blue plastic Carlon  old work boxes. Each box was screwed to the side of a stud using 3 screws. The drywall flippers were also engaged. Each box is extremely solid...I have no concerns. Hubbell HBL5632W outlets were connected using 10awg pigtails. 20A breakers were used, both on the same main line in the breaker box. My total cash outlay was about $700.

While I know many of you have much more elaborate setups than this I'm really pleased with this setup for the amount spent. I also have a whole house surge protector, so no more outlet strips!

Performance-wise I'm stunned. This is the most significant thing I've done to my system in a long time. The main improvement is in dynamics, but tonality is also improved.

For reference the setup I have connected is as follows:

Line 1
Meridian G08 CD player, Kimber KS1130 XLR
Rowland Synergy 2i preamp, Cardas Neutral Ref XLR
Rowland Model 10 power amp, Kimber Bifocal XL
Soliloquy 6.5 speakers

Line 2
Bluesound Node 2i, toslink
Chord Qutest DAC, Cardas Neutral Ref RCA to preamp

Oops, that should have been HBL5362W outlets.

Thanks for coming back to update this. Great to hear it worked out and sound is improved.