Offering: Subwoofer Modifications


Oct 26, 2015
Eastern WA
Offering: Subwoofer Amplifier Modifications

Hi guys,

I've been inspired to post here after Ack's thread about his system, and people asking questions about modifications to subwoofer amplifiers. On another forum I've been doing this for some members that use Rhythmic servo subwoofers. The Rhythmic's with OB subs are so good they can replace midbass drivers for people running a variety of midrange & tweeter combinations. And then the curiosity turned into a trial run. The results have been some happy people. Here's some links to two fellows who shared their results. |Link 1| |Link 2| |Link 3|

*I would like to add that while I'm not bothering to offer Level 2 mods on Rhythmic's currently, the main function is due to price vs. the Rhythmic amp's price (the mods cost more than the amp that's made in China).

Upgrade Modifications
As an open call for people's interest, I cannot explain the mods I would pursue for every single subwoofer amplifier there is out there. I'll try to cover a good amount here in the thread, before necessitating direct console via PM.

Capacitor upgrades:

With some amps it will be an option to upgrade the capacitors along with standard mods, for some it will not be. The issue is that depending on the physical size of the capacitors it may or may not be impossible to locate replacements that will fit on the PCB board.

"What about off-board"? If I do that I cannot guarantee the capacitors themselves will be any kind of an improvement. You've surely seen someone do this but what you may not know is there's an inherent risk of creating a current sink due to the long leads. The size of the leads have no tangible bearing on the potential current sink. I don't recommend this unless you're DIY'ing so you can make appropriate changes after listening. The only other way is I need the entire subwoofer to evaluate the change, and I believe that's fundamentally less desirable to ship such a large item twice (inquires welcome, if that truly is your desire for a tuning that has the potential to offer absolute performance).

What I don't do is willy-nilly start placing capacitors all over an amp. If I can clearly define an upgrade then that's great, but more capacitance doesn't always equal better. Sometimes more capacitance can cause current problems by detuning a circuit, shift frequency responses, etc. I use clear and evident reasons to add or change capacitors.

Primary upgrade:

This is about changing the behaviour of how current moves through the device first and foremost. It may appear like small changes but my reasons for why and how are from years of R&D that I can offer now while I'm not too busy with commercial products. (these upgrades may not be available forever)

The results have been anything but small changes. As noted in a post above moving from muddy to clear is not a light objective. They are not for changing the frequency response to tune the room or any such thing; they're pure, for quality of existing source signal. This is an option to achieve performance that you may have only been dreaming about otherwise (or didn't know existed, as one fellow stated).

*Upgrades are only offered for amps that use a transformer, a linear power supply.

Level 1:
  • Replacement of both diode bridges with discrete, superior, components. (this is being updated to a potted version that has improvements including vibration dampening)
  • Dampening both secondary windings.
  • Adding a DENO to ground which reduces common mode noise.
  • Twisting output and control wires to reduce their field size.

Level 2:
  • Mounting discrete (superior) diodes off board.
  • Large filters on the DC side off board.
  • Dampening both secondary windings.
  • Adding a DENO to ground which reduces common mode noise.
  • Twisting output and control wires to reduce their field size.

*Level 2 adds complications because it typically requires off board mounting for the addition, so the user must be handy enough to connect some wires and screw the board to something/make brackets. If the amp is stand alone in a box I can provide that service.

*It's worth mentioning that there's high voltages in many of these amplifiers so you must take caution, and I can explain how to safely do so.

Other modifications:

On a case by case basis I may have suggestions for improving any given amplifier. I have to evaluate each one. Many are too complicated on the front end to suggest modifications because I'd be making a new amplifier; and it's not really necessary since anyone seeking these mods isn't going to be looking at modding a piece of junk.

What I'm not doing is stuffing a unit full of exotic parts that may have minor influences on sound - like charging $800 for a teflon cap upgrade you wouldn't even notice. The changes are meant to fundamentally improve the amplifier, distinct, and within reason both for cost & time. Frankly subwoofers do not display all the qualities that a fullrange amp and speaker will. Putting on pure copper RCA jacks would be probably entirely pointless, for example.


I'm not posting that here. First it may be against the rules, secondly I don't know for sure without knowing the model of an amplifier, and may require some pictures to give my most accurate estimate sight-unhandled if you need to budget the upgrade tightly. What I can assure you is the upgrades are cheap compared to seeking new subwoofers that can accomplish something similar to the improvement (perhaps, few subwoofers amps wouldn't benefit from a few changes).
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