Fender Rumble 15 Mod

Discussion in 'Amps and Cabs [BG]' started by PrietoBass, Jul 14, 2013.

  1. PrietoBass

    PrietoBass How does he do that?

    Apr 16, 2009
    I've had a Fender Rumble 15 for about four years and I was getting very tired of the sound. I use it strictly for practice.

    I tried to get rid of it... posted it for as low as $25 on Craigslist and didn't sell. GC wouldn't give me even a lollypop for it.

    Then. I stumbled onto some threads by people buying Ampeg BA-108's and replacing the speaker with the Eminence Alpha 8a, which sells new for $49.99.

    So I could buy the Ampeg BA-108 used (about $60 if you can find it), or new ($100), and then replace the speaker (another $50).

    So, I ordered the Eminence and put it in the Rumble.


    Then I said, what the heck, I'm going to port the little thing and see what happens. So I ordered one of those flared 2" port kits from precision.

    After doing some calculations, I "thought" I was shooting for 45Hz... but I measured wrong... and after cutting the hole on the side I found out that the inside flare would not fit because it bumps into the speaker. :)

    So I had to extend the tube... right now it's about 11.5"... I forgot, so it's tuned to around 35Hz, if my calculations where right. (I estimated the volume of the enclosure at .574 ft^3.)

    I also lined some of the sides of the speaker with AC filter foam (I had some and it was a last minute decision). And if it matters, the foam is black. :D

    Ok, I put everything back together. Here's how it looks like now.


    Results? Less distortion. More clarity. The notes on the B string on my 5er sound better. Overall I'd say it sounds better.

    Before I just hated the sound going straight into the amp so I always ran a BDDI in front of it. Now I just plug straight into the amp.

    I's say the mod was a success. Was it worth it? Well, that's subjective. But I did learn a thing or two in the process so that was definitely a plus.
    chupacerveza and fritzk9 like this.
  2. Nice first DIY project! Seems like you learned some useful things and achieved your goal of getting improved sound quality.

    A few model runs suggest that you can pick up a few db in the 50-90Hz range by tuning a little higher (mid-50's). This will actually improve the sound of the b-string by strengthening the 2nd harmonic. Just notch out the internal flare so its not touching the speaker.

    Or just have fun with it as-is...
    chupacerveza likes this.
  3. Plucky The Bassist

    Plucky The Bassist ZOMG! I'm back from the dead! Supporting Member

    Jul 30, 2010
    Nice post, I see plenty of those amps and wonder if it would be a good investment for an amp to do acoustic coffee shop gigs. Great to hear it's working well for you!
  4. PrietoBass

    PrietoBass How does he do that?

    Apr 16, 2009
    Thx Astro and Thunda for your comments.

    I initially thought of tuning to 50. Per your (Astro's) analysis the B string would have benefitted more from that 2nd harmonic boost. But it's pretty good as it is... And I suspect primarily because the Eminence is so much superior than the stock speaker in every way. Considering that this is a practice amp I'm going to leave well enough alone, that is, until the time I feel the itch to tinker with it again. :D Right now I'm set.

    Vanilla, some people are buying Ampeg BA108's and replacing the speaker with the Eminence. I found a thread where someone put a 10" speaker in the BA108. If I was starting from scratch, I'd probably go the Ampeg route, but since I already had the Fender and I couldn't get rid of it I was willing to bear the risk of thrashing the amp. But it turned out nice and I think it would do fine in an acoustic setting.

    I would do it again if I found a Rumble pretty cheap... Perhaps someone even has one that is not using it and would be willing to give it away.
  5. Yahboy


    May 21, 2008
    Nice driver replacement.I have done a similar job with Eminence Alpha 8A in 2008.
    Marshall MB 15.
    Sound MUCH better and can handle more low.Finally sold to a guitarlist who like the MEATY tone from this MB15.

    BOY_0144 by totomoyap, on Flickr
    chupacerveza and MoosEsooM like this.