Speaker Noise can it be removed?

[Crumbs]

What can be done, and is it even possible, to reduce low/muted signal speaker hiss?

Related threads (different focus):

• https://www.audiosciencereview.com/forum/index.php?threads/powered-speakers-self-noise.41462/
• https://www.audiosciencereview.com/...ible-noise-hiss-in-loudspeaker-and-snr.41696/

Personal History Context

• The system is: 5 channel active crossover, unbalanced into 5 2-way speakers.
  • I can hear hiss in the speakers when there is no or low signal.
  • The noise is not amplified
  • The noise can change with ground changes, ie I can make it worse by inducing true 60 Hz ground loop, but I can't make the sound go away
• The room is on the small-mid size so rear speakers only a few feet away, and front speakers 6-8 feet away. Rear speaker noise is more annoying due to less audio content in rears and it being closer to the listener. Can technically hear front if listen hard in silent room.

Here is the list of things I've tried in no particular order:

• separate power line from circuit breaker that only the A/V equipment is connected to
• added additional ground with 8 foot copper bar into ground for the power panel
• ground run from amp chassis to preamp/receiver and also to active crossover case
• equipment connected to the same power strip
  • different power strips tried
  • amps connected through relay or non-relayed power strip
  • amps connected through DC blocker, EMI reduction power strip
• disconnecting everything (power and RCA lines) but amps (with and without extra ground wires to other hardware)
• same/different tweeters directly wired to either amps, or preamp (actually a receiver) output
• different amplifiers
• different active crossovers (DSP and Op-AMP based tried)

I have not yet tried a isolation transformer due to cost, and given the noise occurs with DC blocked and no amplifier input I am not sure it will help. I do not remember if I've tried amplifier not connected, and RCA input shorted.

My conclusion is these things point to the noise being related to the noise floor or amplifier gain, and I strongly suspect I have to live with it. Hoping others can suggest alternative solutions to consider.

 

[NTK]

Welcome to ASR!

If it is a problem with the amplifier/DSP idle noise being too high, have you considered padding down the tweeters to lower the sensitivity, e.g. by using L-pads.

 

[AdamG]

Can you post up a Video of the sound please? It will help our resident wizards better understand what is going on and result in better suggestions to fix/improve the noise.

 

[ppataki]

Just a comment about the cost of an isolation transformer: I am not sure where you are based but if you are in Europe I would strongly recommend this one:

VOLTCRAFT IT-1500 Labor-Trenntrafo Festspannung 1500 VA 230 V/AC (max.) kaufen

Schnelle Lieferung ✓ Große Auswahl an %brandid% Produkten » Jetzt einfach bestellen: VOLTCRAFT IT-1500 Labor-Trenntrafo Festspannung 1500 VA 230 V/AC (max.)

www.conrad.de

It is a fraction of a cost vs 'audio' isolation transformers and I can confirm that it works like a charm (I have been using it for >1 year)

 

[Crumbs]

Welcome to ASR!

If it is a problem with the amplifier/DSP idle noise being too high, have you considered padding down the tweeters to lower the sensitivity, e.g. by using L-pads.

Yep, I'm a long-time lurker, first time poster.

Based on the suggestion I did try an L-Pad using some random high watt resistors I had lying around. The harshness of the noise dropped off and it was likely attenuated a bit for the non-optimal setup held together with alligator clips.

I think I've been reluctant to add L-pads or other significant passive components to squash the noise, though I suspect as I now go down the route of noise reduction and L-pads I might revisit the logic of having active crossovers. Integrating good L-pad design into the just-in-case high-pass series capacitor already on the high terminal of the speakers may trigger building a separate external "crossover" box anyway.

 

[Crumbs]

Can you post up a Video of the sound please? It will help our resident wizards better understand what is going on and result in better suggestions to fix/improve the noise.

The noise sounds like this ... note it is not ground hum per say, though I can create some pretty strong ground hum with the wrong set of connections.

 

[Crumbs]

Just a comment about the cost of an isolation transformer: I am not sure where you are based but if you are in Europe I would strongly recommend this one:

VOLTCRAFT IT-1500 Labor-Trenntrafo Festspannung 1500 VA 230 V/AC (max.) kaufen

Schnelle Lieferung ✓ Große Auswahl an %brandid% Produkten » Jetzt einfach bestellen: VOLTCRAFT IT-1500 Labor-Trenntrafo Festspannung 1500 VA 230 V/AC (max.)

www.conrad.de

It is a fraction of a cost vs 'audio' isolation transformers and I can confirm that it works like a charm (I have been using it for >1 year)

Part of the problem with using a isolation transformer is that because I have 5 speakers, I need 10 channels of amplification. I have 2 high current amplifiers running. Yes I likely max out the circuit long before I can use the full wattage of either but I have concerns about putting even further VA limitations on the power drawn. Even though I don't listen at volumes necessitating full power, the on/off current, soft or not, could be an issue. These are all hypotheses, some stupid, that one justifies when trying to figure out if one bag of technical specs and associated cost will solve a problem or create more problems. In the end I just haven't justified the money even though over a course of years I've been going slowly down the rabbit hole. Part of me says to put in the time and effort for a good passive crossover at this point to lower the noise, then sell off the active parts, while reducing the system complexity.

 

[Mr. Widget]

The clip you posted sounds like reasonably clean amplifier noise floor... but crazy loud! This is not something to be fixed with an isolation transformer.

Please describe your speakers and what amplifiers you are using. Are you sure your electronics are working properly?

 

[dlaloum]

I would look for gain issues - what is the gain setting on preamp, what is gain setting on power amp... and possibly what is the output level on the source.

Somewhere along the line the setup is amplifying the perfectly normal noise floor.... and that often points to a gain issue

 

[Sokel]

Sounds there's something broken somewhere.
Have you ever measured for DC on your speakers terminals?

 

[Crumbs]

The clip you posted sounds like reasonably clean amplifier noise floor... but crazy loud! This is not something to be fixed with an isolation transformer.

Please describe your speakers and what amplifiers you are using. Are you sure your electronics are working properly?

I probably should have said that I couldn't hear the noise when replayed on the laptop over the built in fan, so I ran it through audacity to amplify it before posting. 38.976 dB amplification later you get the posted clip.

 

[Mr. Widget]

I probably should have said that I couldn't hear the noise when replayed on the laptop over the built in fan, so I ran it through audacity to amplify it before posting. 38.976 dB amplification later you get the posted clip.

The point is, there is none of the classic 60Hz hum or buzz from a ground loop or other grounding issue, it sounds more like like pink noise. I think you either have set your gain structure incorrectly or you have damaged or poorly designed electronics.

 

[Crumbs]

Sounds there's something broken somewhere.
Have you ever measured for DC on your speakers terminals?

I have not but I did now. Also see response above, loudness due to 38.976 dB amplification. Also similar levels and types of noise have persisted across different active crossover, different amps, different power strips, disconnected or connected pre-amp receiver, different pre-amp receiver, etc.

• 0 on the tweeter. there is a low frequency blocking cap on the tweeter to prevent below active crossover frequency, below tweeter Fs pass through transients in the event of an unplanned noise event.
• .4 on the woofer for a 200m scale, does not register on higher scales at all.
• woofer does not have the noise issue, noise just from tweeter.