CRT monitor vs. Loudspeaker

[bluesmoke]

Possibly a bit of an odd question, however...

Would having speakers close to a large CRT computer monitor be detrimental to the speakers?

I'm already familiar with CRT related problems (purity, convergence, geometry), but I'm mainly wondering about if the CRT's degauss cycle would slowly deteriorate the speaker magnets.

I've been using biggish speakers next to the screen. No CRT anomalies, but more worried about long-term speaker problems. Possibly a safe distance range?

Any opinions or input greatly appreciated!

Cheers,
bluesmoke

 

[Svante]

I would be very surprised if this is a problem.

 

[EC8010]

No. No problem at all. Well, I suppose if you put the drivers facing the screen spaced by less than an inch it's possible that the bright light and weak alpha radiation might cause foam surrounds to rot a little quicker.

 

[Netlist]

I think you would need to wind the degaussing coil around the speaker’s magnet in some way to experience long time effects. It is much more likely to damage a CRT with the speaker’s magnet than the speaker with a degauss circuitry.

/Hugo

 

[Geoff H]

In my TV repairing days, I don't recall ever seeing damage to the speaker in the TV, by its CRT only inches away.

Replaced one that had gone O/C. That happens without the aid of a CRT.

 

[bluesmoke]

Yup, of all the speakers I've seen inside TV's (except LCD). Most if not all were shielded in some way, done to protect the image on the CRT of course.

How about this... Would the degauss field be able to induce any anomalies into the speaker crossover coils (thus possibly tracing back into the active amp)? Negligible if anything, but possible?

True, I have never seen or noticed any problems in my and others similar usage. Especially being a popular setup for small music studios as well.

Just one of those things on my mind...

 

[Geoff H]

That is an interesting question. A large air core inductor would pick up some some of the degausing flux at power on. Not much though. Then by the time it got through the NFB to the input stage, there'd be much less.

The horizontal sweep energy could be more of a problem, yet does not appear to be. Something, for those that have experienced short tweeter life, to consider.

Geoff.

edit: Afterthought. Bluesmoke, watch where your degausing wand's power plug is if near a TV at switch on. Good thing they have a push button switch.

 

[CeramicMan]

How about this... Would the degauss field be able to induce any anomalies into the speaker crossover coils

Hmmm... interesting point. However, I'd be more concerned about the oscillating magnetic field from the deflection coils (which run constantly) rather than the degaussing circuit.

Think about this: most people would've seen how a magnet can "bend" a CRT image slightly, whereas the deflection coils are WAY more powerful than that – they bend the electron beam from the center of the screen all the way to the corners! I'd say that such intense fields could definitely be picked up by air-cored inductors if the CRT isn't shielded adequately.

The frequency would depend on the refresh rate and resolution.

 

[bluesmoke]

Yup, definitely saw that coming. Been to a few studios that ran audio cables behind or under cheap CRT monitors (or a with mixer nearby) and could hear a buzz leak through. Even had to tell them to turn the things off before live recording or mastering... (and no one even noticed... erk!)

 

[megajocke]

Hmmm... interesting point. However, I'd be more concerned about the oscillating magnetic field from the deflection coils (which run constantly) rather than the degaussing circuit.

Think about this: most people would've seen how a magnet can "bend" a CRT image slightly, whereas the deflection coils are WAY more powerful than that – they bend the electron beam from the center of the screen all the way to the corners! I'd say that such intense fields could definitely be picked up by air-cored inductors if the CRT isn't shielded adequately.

The frequency would depend on the refresh rate and resolution.

The yoke sits around the neck of the tube and your speaker magnets are much further away... Inverse square law? If you put your magnets on the tube neck I think you will have more than just color shifts

 

[Geoff H]

The shape of the yoke concentrates the vert and hor deflection field on the beam in the centre of the tube. It's an angular function, not so much a linear distance function.

The power required is not that high. A modern 48CM tele only draws 60-70 watts total from the mains. I'd guess about a 1/3 of that would end up in the deflection coils, which have resistive losses.

 

[unclejed613]

if i remember my radio theory properly, the field strength within the yoke and very close to the yoke structure follows an inverse cube rule, and once you get away from the structure a distance about equal to the size of the structure, it reverts to the inverse square rule..... something like that........

horizontal sweep energy is rich in RF harmonics, and can cause oscillation in an amp if picked up on signal or speaker leads, if one of the harmonics coincides with a point of instability in the amp..... that's one reason not to "compensate" an amp by using an integration cap in the feedback path.......

 

[CeramicMan]

Inverse square law?

I stand corrected!

Furthermore, there might even be some relativistic effects, whereby the electrons appear to gain mass due to their high velocity near the front of the screen, which makes them harder to deflect.

 

[bluesmoke]

All of this would end up being my ONLY reason to consider switching to LCD. However watching video is still soooo much better on CRTs. Risk seems negligible, as this is such a typically common setup.
(Monitor-CRT-Monitor)