Infinity SM-115 Questions

Discussion in 'Infinity Loudspeakers' started by NoPants6227, May 21, 2018.

  1. NoPants6227

    NoPants6227 New Member

    So I received these speakers from my father and have been playing with them for a while. I decided well these aren't the best speakers in the world so lets hopefully make them a bit better. The original woofers were both toast so I replaced them with a Dayton Audio DS270-8. As I was looking into the cabinet I noticed literally nothing in these things just an empty shell. I figured what the hell lets put something in this cabinet. So I lined one of the cabinets with some jute (left side, back right side. leaving top and bottom uncovered). It's 3/4" thick jute and in all honesty it sounds worse. The highs and mids are just more loud and shrill. I don't fully understand it. These speakers never sounded amazing in the beginning but I didn't expect them to sound worse. So my question is what can I do to make these sound better. If it's not worth the investment are the cabinets worth keeping and swapping different parts into or am I better off building my own.


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  2. pauljh

    pauljh Active Member

    San Francisco
    The Infinity SM (Studio Monitor) series was developed to be as inexpensive as possible and was widely sold in US Military PXs. I don't think they were ever sold by the audio-store Infinity dealers. It made a lot of money for Infinity. Many years after he left Infinity Arnie Nudell was interviewed and talked about the SM series. He commented that internally, Infinity referred to this line as their Sado Masochistic speakers. You can take whatever conclusion you want from this story.
  3. Silentnet

    Silentnet AK Subscriber Subscriber

    Charleston, SC
    (They're junk.)
  4. NoPants6227

    NoPants6227 New Member

    So I guess my question at this point is are the cabinets junk too?
  5. goodolpg

    goodolpg Just an old fart trying to help.

    Not sure about your specific speaker model, but many people say stuffing (more/less/type) can make a difference.
    Also cabinet bracing can make an improvement.
    I suspect your SM's are ported so sealing them is not needed.
    Maybe new cap(s) NPE's for a few cents would help.
  6. 7.62

    7.62 Gearhead Subscriber

    Las Vegas
    Sell them on Craigslist, look for better speakers, anything from the IL, Kappa or .1's line would be much better !


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  7. swechsler

    swechsler Frog Whisperer

    7th row center
    When you say the original woofers are toast, I assume you mean that the surrounds were shot, which is very common with older Infinity speakers, and pretty much universal on the SM line. These can be repaired fairly inexpensively by even a casual DIYer, and is better than just installing a random woofer. It's possible that the Daytons you installed are not as sensitive as the original Infinity woofers, so fixing the originals and reinstalling them may fix that somewhat. However, as others have stated, these were never great speakers. What I'd do is purchase inexpensive generic foam surrounds for the woofers and repair them, then reinstall them in the cabinets and sell them on Craigslist. Save the Daytons for another project (and learn how to use speaker modeling software).
  8. jazzmans

    jazzmans Super Member

    devils playground, NV
    as a confirmed Infinity fan, I can say with absolutely no reservation that
    Those speakers are junk to my ears. Loud, painful, and no fun at all for anything but a stupid loud party

    I wouldn't waste a dime, get rid of them and buy any Infinity with an Emit.
  9. GregDunn

    GregDunn Active Member

    I have a pair of SM125 on my AV system, and face it: most TV and movie media are not hi-fi; they're intended to be played loud, and movie music is not mixed for audiophiles anyway. They are efficient and do a fine job.

    But my speakers are not factory stock. As hinted above, the construction of the SM series is very budget. There's nothing really wrong with the drivers, but they are just stuck in an undersized cabinet with no bracing or stuffing and by default are very dull and boomy. Since I got mine for free, I figured I could invest a few $ in attempting to make them better. It's not hard, and it makes a huge difference in the sound. I'm guessing I spent $20 on a free pair of speakers, and it saved me from spending hundreds on a bigger receiver. :D

    Of course the surrounds on the woofers were toast, so those got replaced. While I had them out of the box, I placed some heavy wood bracing wedged and glued between the front and rear panels (4 around the woofer, a couple more further up in the box) and filled them with insulating fiberglass, making sure not to cover the port. The boxes being undersized, and the bracing stealing even more volume, the fiberglass increases the effective internal volume while further reducing some of the resonances. With the low end tamed, I ran a RTA on them at the listening position and flattened the remaining response with a graphic EQ. They don't go super low anyway, so I crossed them over to an M&K sub in the bottom octave. The resulting response is surprisingly flat.

    No, they're not even as good as my RS4000, which is the speaker I use in my office system (dedicated to music). They're also far more efficient and for my AV setup, perfectly satisfactory. They do voice and loud SFX just fine and don't stress my Sony AV receiver (also a free acquisition). Maybe someday if I can find a pair of RS5000 or one of the better RS floorstanding systems, I'll upgrade. But if I do, they'll likely replace the RS4000 instead. ;)
    Bahamayellow likes this.
  10. Dirtweed

    Dirtweed AK Subscriber Subscriber

    I have the SM-152. When I turn them up I don't have Tinnitus anymore. :)
    When I am working in one room across the house and I want to hear tunes I crank up the Onkyo TX-2500 MkII and the Infinities.
    I bought some angled stands for them so they are not tipping forward after this picture.

  11. jsours

    jsours Active Member

    I have some SM 120s that I fooled around with and they turned out to be decent. Not as good as my Kappa 7s or my NS 1000s, but passable certainly. I refoamed the woofers and completely filled the cabinets with polyester filler. I found a decently priced pair of high output Polycell tweeters to replace the original models, which I found a little sharp. I can play these all day and spook the neighbors when I need to.


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