I have a polk psw11 sub. Recently hooked up to my 6LU8 tube amp. I use the speaker level inputs. After a bit of trial and error, I have the frequency and volume adjustments where I think they sound best.; Here is the problem. With low level bass there is often a bit of noise on top of the bass. At higher levels, like playing loud, or with bass heavy modern not acoustic, there is no noise. It sounds like a dirty pot, but does not come and go with turning either vol, or freq knobs. Speaker wires are all hooked up solidly.
My question is whether this is a repairable problem or not. If not, is there a 'replacement' sub amp that is very affordable?
Roger
My question is whether this is a repairable problem or not. If not, is there a 'replacement' sub amp that is very affordable?
Roger
The problem is likely caused by the use of high-level inputs. Typically low-level connections are made through screened cable.
Roger,
If you were hearing an amplification problem, the noise would increase with the subs gain (volume) setting.
Your description sounds like you might be hearing finger board noise from an acoustic bass.
Round wound strings often preferred for thier articulation are more noisy and have more "scratchy" upper harmonics than flat wound.
Much of the older acoustic music was recorded with less low bass due to vinyl record limitations.
At low sound pressure levels, the fundamental low frequencies don't sound as loud to your ear as their upper harmonics, the reason for a "loudness contour" switch.
"Bass heavy" music generally has more of a low note's fundamental relative to the upper harmonics than acoustic, and when you listen at louder levels, your hearing (should) tend to "flatten out", as can be seen in the equal loudness contour graph.
Also note that around 1000Hz a 10dB reduction in level sounds half as loud, while at around 41Hz (the low E on an upright bass) dropping by only 5 dB sounds half as loud.
You may want to increase the sub's volume at low levels compared to higher level, a variable "loudness contour".
Art
Thanks guys. I will do some experimenting. Also the speaker wire is old, and although I have tinned the ends, the copper is coated with oxide. It lived in the garage for a long time. That is a no trainer.
Also, I get the extraneous noise from acoustic bass. I have heard it, this is a bit different, again, some experimenting will help.
I will hook up the sub to my HT system where it came from, and listen to the same program material and source.
Roger
Also, I get the extraneous noise from acoustic bass. I have heard it, this is a bit different, again, some experimenting will help.
I will hook up the sub to my HT system where it came from, and listen to the same program material and source.
Roger
Art,
The noise is higher frequency than what I expect the low-pass would cut off. Kind of like crinkling paper, not low frequency rumble.
My guess is that if after the low pass it is amp noise?
Roger
The noise is higher frequency than what I expect the low-pass would cut off. Kind of like crinkling paper, not low frequency rumble.
My guess is that if after the low pass it is amp noise?
Roger
Okay. Got tired of the noise, like static. switched back to HT sub out, disconnected the speaker wires and listened to the sub using my HT system and the sub out, with the same source, well via HDMI rather than SPIDF(?).
Anyway the noise was still there. So not my set up, but something inside the sub. I REALLY do not want to spend a lot of money on this, it is, for me, a DIY hobby. So, a replacement plate amp via Ebay, they are available used. A new replacement or similar sized plate amp, a DIY class D or chipamp with a low pass filter on t drivng the speaker nside the sub. I expect this to be the cheapest route, although I am warming up to a used one from Ebay.
I know the PSW10 is not a high end unit, but it did the job, except for the noise. It seems a shame to me to let the box, driver go without trying something. Budget suggestions welcome.
Roger
Anyway the noise was still there. So not my set up, but something inside the sub. I REALLY do not want to spend a lot of money on this, it is, for me, a DIY hobby. So, a replacement plate amp via Ebay, they are available used. A new replacement or similar sized plate amp, a DIY class D or chipamp with a low pass filter on t drivng the speaker nside the sub. I expect this to be the cheapest route, although I am warming up to a used one from Ebay.
I know the PSW10 is not a high end unit, but it did the job, except for the noise. It seems a shame to me to let the box, driver go without trying something. Budget suggestions welcome.
Roger
Sounds like a bad capacitor or transistor in the subwoofer's amplifier. Not really user-repairable, unless you know what you're doing, you're handy with a soldering iron and you know how to get your hands on the required replacement parts.
I agree. I have inspectedthe insides, and nothing obvious. I am trying to come up with a solution. I am thinking class D amp with SMPS. That part is straightforward. What is more complicated is the fact that my DIY 6LU8 a p does not ha e a pre or sub out. I could use a voltage divider on the output, or tap off of the volume control. Next would be some low pass device. I like the sound a sub adds to my system, and as a DIYer, I want to salvage the sub if possible.
Roger
Roger
That amplifier likely has special EQ built-in to get the best performance out of that combination of driver and box.
If I was going to DIY a replacement, I'd just take the amplifier out, seal up the hole with a piece of wood cut to the same size, put a terminal on it, and then power it from one of those "chip" amps, and use DSP if necessary to get the best out of it.
If I was going to DIY a replacement, I'd just take the amplifier out, seal up the hole with a piece of wood cut to the same size, put a terminal on it, and then power it from one of those "chip" amps, and use DSP if necessary to get the best out of it.
Pretty near my plan. I think I will install the chip amp and smps inside the box, and use existing terminals etc. I have my eye on an inexpensive sub pre-amp the will combine two channels, has an adjustable low pass filter and volume control. My concern with that is the quality, or rather lack of, for the filter. Looking into a different approach to the low pass filter. Parts express has some, but for more $ than I wa t to spend. A d Iknow, I get what I pay for
FWIW, I wouldn't put an amp in the same box as the subwoofer. The "active subwoofer" thing with a consumer-focused solution, giving them both a subwoofer and an amplifier at the time of purchase, with all of its pitfalls (usually proprietary amp, line-level signal needing to be sent over a longer distance, etc.). DIYers don't have to follow that path 🙂.