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  1. #1

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    Default Sony SAWM-40 mod

    After reading last night about modding the Sony 12" 120W SAWM 40 subwoofer, I thought I would give it a shot. My first mod dontcha know.

    All it involves is taking some polyfil and stuffing the insides of the casing with it. Prior to it, the only internal insulation the thing had was a 1/4" thick piece of polyfil on the wall opposite the woofer. Not much at all. I took probably a 1/4 pound of the stuff and stuffed it in so that the two sides and top walls had another 3-4" of polyfil in them. The bottom of the housing was left alone so that the port would not be plugged.

    The results were worth the $5 and 15 minutes of time. I did no testing with an SPL meter. I still need to get one. :) Anyways, all results are subjective, but thats what really counts. I did a before and after using my HT demo DVD that I am still in the process of finalizing. Tracks reviewed were:

    Matrix lobby scene
    LOTR FOTR battle scene were Sauran get his hand chopped off, ring falls and body explodes. (I find this scene to be a good measure of a sub's capability as it goes deep and has a distinct tone that reveals quality in the sub as well.)
    Antz picnic scene
    Finding Nemo with Darla
    U-571 depth charge scene

    Equipment and settings:
    DVD player: Pioneer DV 434
    Speakers: Polk R40 (front) set to small
    Polk CSi20 (center) set to small
    No center
    Monster Cable subwoofer cable
    AVR: Onkyo TX-SR 600 (crossover set to 80Hz) Volume set at 70
    Subwoofer: crossover set to ~110Hz and gain at the 1:00 position.

    The two words that come to mind after the mod are clean and tight. Clean in that before hand it felt as if the sub would let out, in addition to the intended bass, noticable amounts of bass in the surrounding frequencies. Now it really feels that the correct tones are delivered without competion. Clean.

    Tight in that it hits the note and its over with. This has really been a problem when listening to music. Classical, rock, jazz and even rap. It was easy to tell the bass was just dragging on too long. I have yet to evaluate this with music, but the bass was much tighter after the polyfil.

    Some reviews have argued that the quality of the tone/timbre was improved post-mod. I didn't really notice this, but it may be. Of the above scenes, Sauran's explosion was the most dramatically improved one. Again, I have no SPL meter to evaluate, but it felt as though the bass extended deeper. I have heard all the scenes on an SVS 20-39, for reference. After the mod, the bass extension was closer to matching the SVS than before (and still very far away). Any extension lower is minimal and debatable.

    Bottom line: a fun, easy, cheap and effective mod that has injected some fun back into my little hobby. The results were small but significant. I am looking forward to getting some time with music on the rig now and evaluating the mod further.

  2. #2

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    Default

    Sounds like fun, cheers to endless tweaking!

    :D

  3. #3

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    Default

    I did the mod when I had that sub but I did it a little different. Instead of using polly-fill I used egg crate foam. I cut peices for all the internal walls but making sure not to block the port. It tightened it up subtantially and made me proud to own it. I ended up selling it to my brother-in-law and getting an SVS. Though the sony is a WONDERFUL sub for the $ the SVS really made me understand what a sub should do.

    If I ever find another sony that is in good condition I will buy it and use it on a 2nd system. The sony is such a good sub for the $ and the size, IMHO it can't be beat for it's price range.

    Glad you like the mod!
    Front----------Polk RT800i (BI-wired)
    Rear-----------Polk RT600i
    Center---------Polk CS400i (BI-wired)
    Sub------------SVS 25-31PCi (22Hz tuning port)... it's SubHuman
    Receiver-------YAMAHA RX-V1400
    TV-------------Mitsubishi WT-46807 HDTV
    HD receiver-----T i V o HR10-250

  4. #4

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    i did that mod to a sony wm-500 (essentially the same sub, later model). i also put some layers of Mod Podge on the driver (4 layers) which supposedly stiffen the cone of the driver. i did the polyfill stuff and mod podge coating at the same time and noted significant improvement in the sub's performance. i gave it to my friend for his budget home theater and it rumbles the hell out of his fairly large sized TV room.
    Theater - Polk LSi15, LSiC, LSi9 speaks, DIY Sub (142.5L box, SVS plus driver, 500 Watt plate amp)...Outlaw 990 pre/pro, Carver TFM45, 2 X Outlaw M200 . Rotel RB980 . PS3, Monster 3600 power center

    2 Channel -
    Anthem Pre 2l, Jolida JD100 CD player, CAL Sigma DAC, Carver m4.0, Polk LSi9 w external modified Crossovers (thanks Trey!)

  5. #5

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    Finally got a chance to listen to some music with the newly modded sub tonight. I put on the Maroon 5 album. In addition to the observations I noted in HT application, with music the Polk to Sony seam is much less noticeable. This had been my primary complaint about the sub beforehand. When listening to music, primarily jazz and classical, there was a huge seam. You could easily tell which notes were from Polk and those from the Sony sub. While that same seam still exists, I now have to find it, rather that it presenting itself to me, loud and clear.

    Again, a great mod for $5.

  6. #6

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    I had two of these subs. I did the mod and I think I could hear the difference but after I built my sub I took these out. I noticed that filling the subs completely and plugging the port tightened up the bass, probably because of lower group delay. I might build an IB or something with them some day.
    Graham

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