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Old 9th August 2012, 10:20 AM   #1
pshdk is offline pshdk  Denmark
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Default Hiss(white noise) on tweeters and one midrange?

Hi,
Maybe someone could help me? I have a hiss (white noise) on both speaker tweeters and one midrange driver. I have tried different amps, speaker cables and wall sockets, but it stays the same. The volume control does not effect the volume of the hiss and its connected with or without a source or av cables.

Tweeter Dynaudio D28aF , midrange D52af.

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Paul.
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Old 9th August 2012, 11:20 AM   #2
pshdk is offline pshdk  Denmark
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Now I have a hiss in both tweeters and both midranges.?
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Old 9th August 2012, 11:50 AM   #3
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Hi Paul,

Hiss on midrange ? it is generally on tweeter. Your crossover should be with very low slopes if the mid can reproduce the hiss.
I don't think the passive crossovers components generate hiss. Perhaps it is a problem of electronic, amp stability with the speaker ? And the hiss is a high frequency, you see this with an oscilloscope.

The hiss or hum 50Hz/60Hz is something normal. This problem is very annoying with high sensitivity speakers (>95dB).

Note you sensitivity to these noises vary with your health status.

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Old 9th August 2012, 12:08 PM   #4
Mooly is offline Mooly  United Kingdom
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The speakers only reproduce what is fed to them so any hiss must be coming from the amp.

Normally it should be barely audible even with your ear close to the tweeter (certainly with the volume down).

Hiss is normally white noise, it's not a single frequency,
White noise - Wikipedia, the free encyclopedia
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Old 9th August 2012, 02:08 PM   #5
pshdk is offline pshdk  Denmark
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Thanks,
The speakers are dynaudio mps330 4ohm i'm not sure of the sensitivity? So its nothing to do with the speaker crossovers, old caps ect? I'm very sesitive to white noise ect. I can hear these noises and other can not. Only when I tell them to go up close to the component, tv, amp ect. can they hear the noise. Is this a mental health issue? or do you think vitamins could help?
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Old 9th August 2012, 02:15 PM   #6
Mooly is offline Mooly  United Kingdom
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Absolutely nothing to do with the speakers or crossover.

Keep taking the tablets, you'll be fine :P
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Old 9th August 2012, 02:39 PM   #7
system7 is offline system7  United Kingdom
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Thermal noise in amplifiers and sources is inevitable. It's one of those features of nature. Jodrell Bank space radio telescope would cool it's receiver in Liquid Helium to minimise it, but it it's to do with Boltzmann's constant and the laws of thermodynamics.

An amp designer has to balance many features for a good sound, and the best you can do is minimise it for good signal to noise ratio and efficiency, wide bandwidth, low distortion and good common-mode rejection. It may be your speakers are on the efficient side at 4 ohms, and without a valve like impedance matching switch, you are just stuck with it. After all, the object of good engineering is not perfection, but performance that satisfies 95% of your customers.

The simple circuit below will have better signal to noise with low value resistors, but then loses efficiency and is harder to drive. Trade-offs.

Oh, FWIW, many people's mains is not so good these days. 12V Switched mode power supplies common in computers and domestic appliances dump DC onto the mains. You often find a troublesome DC offset on your supply which can have effects on the transformers and rectifiers in HiFi, causing hums, buzzes and such.
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Last edited by system7; 9th August 2012 at 02:44 PM.
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Old 9th August 2012, 07:15 PM   #8
pshdk is offline pshdk  Denmark
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Thanks.
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