Dead subwoofer? Don’t pitch it, convert it to passive!

[WaynePflughaupt]

When I picked up a used 60” Pioneer plasma TV a couple of months ago, the seller threw in an Energy 8” sub he didn’t need. Worked out well, as I was short a sub. The Paradigm sub we had in our bedroom system had been temporarily promoted to our living room system until we can hopefully get a Monolith sub later this year, so the Energy took its place in the bedroom system.

Well, low and behold, the little sucker up and quit working a week or so ago. I really didn’t want to waste any money replacing a temporary sub, so I decided to “passive-ize” it. I had everything I needed on hand – banana binding posts I could install in the amplifier panel, and a spare Carvin amp with one dead channel that I had retired from my bass guitar rack. (Every Carvin amp I’ve ever owned blew the “A” channel with light-duty usage. Maybe that’s one reason they’ve gone out of business.)

The biggest pain was taking out the eighteen metric socket-head screws (8 for the speaker, 10 (!) for the amp panel). It took more time to get the screws in and out than it did to do the actual internal modification!

The driver showed 5 ohms on my VOM, which verified that it was good. The diver certainly looks beefy, but it has a plastic frame. That’s probably sufficient for an 8” speaker, though…

Once I got the amp panel out, I could see this was going to be an easy fix. All I did was cut the speaker-level input wires at the amplifier board, and spliced them into the two wires that connect from the board to the speaker. Thus, either speaker-level input is now a direct connection to the original driver. Didn’t even need to install a binding post!

Voila, we now have a passive subwoofer! Dropped the little amp into my bedroom rack, rated for 75 watts RMS, and we’re in business again. (The Energy specs say its amp was rated for 60 watts RMS).

I used to think that speaker-level inputs on a sub were cheesy. I’ll never think that way again! They’re quite handy if you ever find the need to “passive-ize” a dead active sub.

Here’s the little dude hard at work.

Regards,
Wayne A. Pflughaupt

 

[lovinthehd]

Would you have done so if you didn't already have the amp, tho?

 

[KEW]

In a past life, you actually reviewed subwoofers, what is your opinion on the little Energy ESW-C8?
Do you have any idea if Energy applied any EQ to it? Did you?

 

[KEW]

Would you have done so if you didn't already have the amp, tho?

I don't know which model @PENG has, but I know he found a source for a replacement plate amp (I think it is OEM). What did that cost PENG?
I have one of these that I threw together with a soundbar in the bonus room (Soundbar for the sake of convenience and/cost -it was dirt cheap because Vizio put the IR receiver behind the grill and the honeycomb grill structure under the cloth blocked the signal about 30% of the time if you didn't deliberately align it perpendicular to the front of the grill panel. All I had to do (thanks to a review on Amazon that explained why it was rated around 2 stars!) was snip out a nickel sized section of the plastic honeycomb structure and I have a perfectly functioning and pretty impressive 2 way sound bar with sub output for $30, IIRC! MSRP was something like $140, but with the reputation for RC failures they were selling them so cheap that people would live with the spotty RC function (unless they read the reviews and saw the fix)!

 

[WaynePflughaupt]

Would you have done so if you didn't already have the amp, tho?

For this sub, no. It would have made no sense to spend money on an amp to power a free sub, when that money could just as easily buy another similar active sub.

However, for anyone who has an expensive sub, it would probably be worthwhile to pick up a used pro audio amp. A couple hundred or so spent to revive a $800-1000+ sub seems worthwhile to me.

Regards,
Wayne A. Pflughaupt

 

[Alex2507]

Do you have any idea if Energy applied any EQ to it? Did you?

I have a couple of Infinity PS 10 subs. One of the plate amps died and I did just what Wayne did. I thought there was some eq stuff going on with the plate amp and felt it necessary to eq the external amp. I externally amped up the other sub as well and eq'ed them both. Now that the eq is flaking out I'm trying to get the T/S parameters of both drivers to see what would work best without any eq'ing yada yada.

It's interesting that the V(as) parameters are different and the amps are different revision numbers and different P/N.

The working plate amp is going back to the sub it came with and the ampless/eq-less driver/cab is gonna be my lab rat

 

[WaynePflughaupt]

In a past life, you actually reviewed subwoofers, what is your opinion on the little Energy ESW-C8?
Do you have any idea if Energy applied any EQ to it? Did you?

I honestly haven’t bothered to give it a critical analysis because I didn’t have any high expectations for such a little sub. Perhaps that was an unfair stereotype. Don’t know if Energy EQ’d it. That would have required “before and after” measurements. I’m stalled in that department, because since we moved from Houston to Corpus Christi I have yet to find my calibrated ECM-8000 mic (we still have lots of stuff in boxes). For the same reason I haven’t EQ’d it either.

Regards,
Wayne A. Pflughaupt

 

[KEW]

I honestly haven’t bothered to give it a critical analysis because I didn’t have any high expectations for such a little sub. Perhaps that was an unfair stereotype. Don’t know if Energy EQ’d it. That would have required “before and after” measurements. I’m stalled in that department, because since we moved from Houston to Corpus Christi I have yet to find my calibrated ECM-8000 mic (we still have lots of stuff in boxes). For the same reason I haven’t EQ’d it either.

Regards,
Wayne A. Pflughaupt

Yeah, I know it is not a proper subwoofer, But I keep thinking there should be an 8" or 10" good "woofer" for use with small to medium bookshelf speakers for music only systems where (after room-gain) you have all of the bass you need for most music. It seems like you could sell a 8-10" version of the Hsu ULS-15 for $450 or less.
Like you, with my Energy sub connected to an ancillary system (with soundbar in my case). I really haven't compared it critically, but I have had it for a while and it has not offended me the way some subs have so I have begun to wonder if it might actually be a pretty good sub.
I usually use this for talking head stuff that has no real bass or a sit-com. I did listen to the Goat Rodeo Sessions on it and was happily pleased with the sound of the cello and upright string bass (which bottoms out around 40Hz). 11:30 is a nice spot for string bass:

The tiny PSB SubSeries 100 (with a 5.3" driver) for $250 has a following of pleased customers and has been on the market for several years. It seems there should be a nice 8 or 10" which fills the niche between the extremes.
https://www.amazon.com/dp/B00FT37GLO?tag=thewire06-20&linkCode=xm2&ascsubtag=AgEAAAAAAAAAAKtKAAAAAH1YjQoAAAAAXH1acw

Maybe there are good options (NHT has a small sub and does good things with their speakers). Unfortunately I have not seem many reviews that rate the sub as how well it integrates for music, and any small sub carries the shadow of not being a "real" subwoofer which, understandably, "demerits" it in the review!

 

[WaynePflughaupt]

Well, it happened again – the Velodyne SPL-10RGB subwoofer I’m using for my computer audio system bit the dust. A little checking around I determined it was not going to be easy or cheap to replace it with something comparable. Thus, I decided to do another conversion.

This one was a little more of challenge to “passivize” than the little Energy sub was.

Removing the back panel revealed that the banana plug connections were underneath a “second story” circuit board, as shown by the yellow arrow in the picture below, which was held in place by a number of nuts and threaded studs, shown by the orange arrow.

Removing the upper board showed that these banana plugs were soldered directly to the circuit board, unlike the Energy which had wiring from the plugs to the circuit board that was easy to splice into. You can see the banana plugs’ four solder points in the picture below, indicated by the yellow arrows. The two inner ones are the negative terminals, the outer two the positive terminals.

I soldered the wires from the driver directly to those points on the board. I also used a razor-blade box cutter knife to cut through the circuit board traces, thus fully isolating the banana plug terminals from any other circuitry, as seen by the orange arrows.

Lastly, I snagged a little RAMSA WP-9055 amplifier off eBay to power the sub for a measly $100 shipped. So, that was the entire expense of the conversion – way less than the $3-500 it would have cost for something of comparable (small) size and quality, even going with something used.

The RAMSA only puts out maybe 100 watts @ 4-ohms, far less than the 1000 or so watts the Velodyne amp generated. However, I only use my computer system for music and YouTube videos played at moderate volumes, so the RAMSA is more than enough.

So, I’m back in business on the cheap with another “passivized” subwoofer!

Regards,
Wayne A. Pflughaupt

 

[WaynePflughaupt]

It should be noted for those wishing to convert a good-quality sub for home theater use, I originally went with a more-powerful pro-audio Crest Audio FA901 amplifier. Ultimately, I couldn’t live with it. Its cooling fan was quiet from a wind-velocity standpoint, but it emitted a high-frequency whine that just drove me nuts. Granted, I was really close to the amp, which is under my desk with the sub.

That was when I re-evaluated my use and decided a low-powered amp would serve my low-demand music needs just fine. The benefit there is that the little RAMSA does not have, or need, a fan.

The moral of the story: A serious HT sub conversion will require a suitable pro-audio amp. Choose your amp carefully and make sure there is a generous return policy, as it may take some “trial and error” to find one that’s quiet enough.

One really quiet yet powerful amp I can recommend from personal use is the Crest Pro xx00 series. I have one in my bass guitar rig, and it is super-quiet, fan-wise.

Regards,
Wayne A. Pflughaupt

 

[William Lemmerhirt]

Nice job Wayne! Long time no chat.
I used an FA901 bridged, on a subwoofer once. It IS noisy, but at 15’ away, I couldn’t tell. Great amp.

 

[Kingnoob]

Well, it happened again – the Velodyne SPL-10RGB subwoofer I’m using for my computer audio system bit the dust. A little checking around I determined it was not going to be easy or cheap to replace it with something comparable. Thus, I decided to do another conversion.

This one was a little more of challenge to “passivize” than the little Energy sub was.

View attachment 59337​

Removing the back panel revealed that the banana plug connections were underneath a “second story” circuit board, as shown by the yellow arrow in the picture below, which was held in place by a number of nuts and threaded studs, shown by the orange arrow.

View attachment 59335​

Removing the upper board showed that these banana plugs were soldered directly to the circuit board, unlike the Energy which had wiring from the plugs to the circuit board that was easy to splice into. You can see the banana plugs’ four solder points in the picture below, indicated by the yellow arrows. The two inner ones are the negative terminals, the outer two the positive terminals.

View attachment 59336​

I soldered the wires from the driver directly to those points on the board. I also used a razor-blade box cutter knife to cut through the circuit board traces, thus fully isolating the banana plug terminals from any other circuitry, as seen by the orange arrows.

Lastly, I snagged a little RAMSA WP-9055 amplifier off eBay to power the sub for a measly $100 shipped. So, that was the entire expense of the conversion – way less than the $3-500 it would have cost for something of comparable (small) size and quality, even going with something used.

View attachment 59334​

The RAMSA only puts out maybe 100 watts @ 4-ohms, far less than the 1000 or so watts the Velodyne amp generated. However, I only use my computer system for music and YouTube videos played at moderate volumes, so the RAMSA is more than enough.

So, I’m back in business on the cheap with another “passivized” subwoofer!

Regards,
Wayne A. Pflughaupt

Dang I had a Klipch pro media sub amp die I think , a new amp cost more then the system itself . No way I can afford fixing it anytime soon or have any clue how too fix it, I meant replace .