Speaker modification advice needed

I currently have Infinity SM 122's. They were given to me by a friend years ago, and while I know they're regarded as pretty bad, they seem to work okay for rock music, and they're what I have to work with until I can upgrade, something that's been at the top of my to do list for a long time but life gets in the way and other things take priority.

I'd like to make the best of what I have until I can pull the trigger on getting something better, I've seen online that these can be improved by adding insulation (they are totally empty) and bracing or other mods. I'm not really looking to get into bracing or changing the cabinets, but if adding some insulation would make a difference, I can do that without much fuss.

How should I go about this or is it even worth the effort? I have some foam padding that I could add, or should I use something different? One poster on another forum (years old, and closed now) stated he had rolled up tshirts and shoved them in the ports, but I wouldn't want to cover the ports would I? Any other simple suggestions would be appreciated (short of putting them in the dumpster).

Thanks!

 

The biggest problems are usually standing waves inside the cabinets that cause errors in bass frequencies, and midrange frequencies bouncing around the inside of the cabinet and then escaping through the bass port.

You don’t want to mess around too much with bass because the effort might change the Q of the cabinet. However, lining the inside (left and right) of each cabinet will help tighten up part of the bass range. Use 1” styrofoam (Home Depot). Attach to the inside cabinets side using silicone adhesive.

An additional layer of acoustic fiberglass insulation (R16 - at Home Depot again) placed loosely in both cabinets - make sure you use just enough to cover the top, bottom, left side, right side and the back. Don’t block the port!

 

Thank you so much Agitater, I appreciate the information.

 

You can use polyfill sheets to dampen the cabinet. Another option would be Sonic Barrier, which has a PSA backing, so peel and stick.

Do not use silicone anywhere near speakers or electronics. The gas off is highly acidic, which is corrosive.

 

Stuff with this UltraTouch 16 in. x 48 in. Denim Insulation Multi-Purpose Roll-60301-16482 - The Home Depot

I doubt you'll be able to get 1" rigid styrofoam into the cabinet w/o having to cut it up into pieces and shove it in through the woofer hole, and trying to get a caulking gun inside also will be difficult.

My suggestion is to use this GREAT STUFF 16 oz. Window and Door Insulating Foam Sealant with Quick Stop Straw-99053990 - The Home Depot which I have used in the past to add vibration reduction to panels. I experimented on a cheap poorly made set of speakers I picked up at Goodwill to see how if my idea was viable and it was - it reduced the 'hollow' sound on a knuckle test. Its low expanding so it doesn't get out of control but make sure to take EVERYTHING out of the cabinets first. Holes can be poked through for wires and to finish it off the denim insulation which can be torn into pieces and stuffed in the cabinet.

There is also 'Dynamat' which I have used with success in reducing noise in cars but they also make a home version now. It can get pricey depending on how much you need and can be difficult to install in a small enclosure although the entire panel does not have to be covered just a good portion of it.

 

Oh, you can always recap the Xover with better parts which should help and use better internal wiring.

 

I've got the Technics SB-A33 speakers, and can't see any way to take the cabinets apart at all, so I'd have to unscrew the woofers and take them out to stuff the spaces with insulation...is this just asking for trouble?

 

For a sealed box, you can stuff the box full with lots of polyester fiberfill (like a pillow's worth), and this will make the apparent box volume up to 30% larger to the woofer, which is usually an improvement.

For a ported enclosure, instead 1"-2" dense fiberglass insulation matting covering the inner walls is the choice (don't use old hay bales like Genelec). It changes the tuning a bit (but the speaker should be designed for it), but more so, dampens standing waves and noises that can come out the port.

Spray the cabinet walls and/or the fiberglass with spray adhesive, let dry a minute until tacky, and apply to all surfaces. You can cut a single piece for all four sides: width similar to the depth of the box, and length is 2x height + 2x width, roll it up tightly and jam it through the woofer hole, and then you can unroll it along the sticky insides of the box to take care of four of the five sides.

No trouble, removing the woofer is expected, although you likely will find little opportunity for improvement inside. The speaker may have a foam gasket seal that falls apart if it has stuck to the box. The speaker terminals may be "locking", where you have to push or lift a tab to disconnect the speaker wires from the driver. It is unlikely to be made like the 2018-era JBL "professional" monitor I just worked on, where besides the missing screws that caused the power plug to flex and break the PCB, and other screws that were 1cm from completely screwed in, the spade connectors were tinfoil on pot metal wires that break if you breathe on them (thanks, China).

 

Thanks to everyone else also. Some great suggestions for a short term fix.

 

I have two lots of Technics speakers:

- SB-A38 260w a front tower speakers (8ohm 89db 130w, 3 way 4 drvr 35hz to 35khz)
- SB-A28 240w b front tower speakers (8ohm 89db 120w, 3 way 3 drvr 35hz to 35khz)

Would they benefit from the afore-mentioned procedures as well?

What's the point of the modifications? (speakers isn't my strong point)

I'd consider the bracing work as well as the insulation as I'm pretty attached to the brand because I've been collecting the kit to go with it and have an obsession with keeping the brand the same.

(yes I know hardly an audiophile approach but I don't consider myself an audiophile just a regular bloke with a nerdy interest in music ).

 

Speakers aren't my strong point either. Basically, I want to buy new towers, and during the research I learned that was I have isn't really that great, but could be improved a bit with some modification. I was looking for whatever easy mods I could do for a short term improvement until I can afford something much better.

In my case, the Infinity SM122's are cheaply made. No insulation on the inside so they have a rep of being boomy. Adding the insulation should cut that down and at least give a better bass response. I don't want to go into the effort/time to add bracing. I don't intend to have to rely on them too much longer.