Sound System Question????

[Cisco Kid]

I recently got the idea to use a car amp and speakers for my MAME cabinet I'm getting ready to construct from a MAME cabinet I seen posted over at MAMEROOM.

Sounded good at the time, so I bought an MTX 202 Thunder amp and a pair of Sony Xplod XS-W4021 4" Speakers.

After visiting this forum and reading through a sound post, it suddenly dawned upon me that those speakers were unshielded and there proximity to the monitor would probably cause problems or could ruin my 27" WG D9200  

I really want to use the speakers and the amp and not destory my monitor in the process. (I hate buying something and not using it   )

I've been told that the Sony speakers have a weak magnetic field

so here is my question....

Will attaching a FERRITE BUCKING CANCELLATION MAGNET to the back of the Sony speakers in reverse polarity allow me to use the Sony speakers in my MAME cabinet without ruining my monitor or causing interference???

(Will this actual work or is it myth???  I don't want to buy something else that doesn't work or I won't end up using)

Thanks in advice to any replies and helpful advice  

[night]

ive done this. not for a cab. but made corner boxes to mount car spekers on ceiling corners and use my pioneer head unit with its remote and a 12disc changer.

and i dont think you understand how much 12v juice you have to supply these things....

a good powers supply is gonna require some $$$. i wanted to do this to for my cab, but had to cut the cost somewhere. so im using something i had 'around' instead. will be even cooler and didnt have to go buy somthing else.

i looked up you amp, and its only 20 amp (fuse rating), but still, im assuming you are thinking PC power supply, and looking at sparkles (very good PSU's at a great price, same thing as the fortron's) on newegg, the only on that give more than 15amp is the top 550w model. which is 100bucks. you can find power converters but all ive seen go for more than PC PSU's.

anyway, was just trying to let you know this before you get to into it. i been down this road and was dissappointed the amount of extra money i had to spend

[SS427]

The shielding problem (if you use the setup you have) may just be trial & error.  I've checked with a couple of people using car speakers in there cabinets, none of them were having any problems with the magnetic fields.  

There is a tutorial out there (check mameworld easy emu or search for car amp mame) on hooking a pc power supply up to your amp.  The individual I checked with on the speaker and magnets was using a ps from radio shack (I think around $100).

For the rest of you guys...Have any of you purchased any of the pc power supplys off of ebay?  Are they bad or something.  I just checked yesterday and they had atx 550 w heavy duty power supply for like @26.00 Buy it Now.

[ZippySLC]

I don't think those speakers would cause any problems with the monitor, believe it or not. The magnet is going to be facing away from the monitor, and if it's a standard layout cabinet, the speakers are going to be about 1' away from the monitor anyway.

I think you're going to have more problems in the power supply department. I would have thought a simple set of PC speakers + subwoofer would cost less than a 12v car audio amp + speakers. Sounds like way over complication.

[SS427]

Other thing to consider is volume control.  I am planning on using the car amp and speakers also just because I already had them laying around (and I wanted to see if I could hook it up and get it to work), so my only real cost was going to be the power supply.  PC power supply also solved my need for 5V and 12V for various things.  Back to the volume thing----with this setup I will have to build some type of volume control.  Computer speakers have that wonderful prebuilt v control that just has to be relocated for easy use.

On another note (anyone else chip in here, cause I'm just guessing) you will probably not get the sound "punch" like you would get in a car.  It would probably sound good, but anything that really pushed the speakers would destroy the power supply (I think most are rated at maximum of around 20 amps for a good one and that is probably only using the 12 volt source).

ss

[OSCAR]

I did the car amp/speaker thing in my upright cabinet.  I epoxied bucking magnets to the backs of the car speakers and it reduced they magnetic field on from the speakers significantly.

http://www.oscarcontrols.com/tmp/magnets.jpg

I also made a volume control (http://www.oscarcontrols.com/volume) and placed it under the control panel.  This setup works very well for me and give plenty of sound, definitely way more than I need in a game cabinet.

[SS427]

Oscar,

If you don't care to tell, what size and type of power supply did you use?

I was wondering where I had seen that volume control hook-up.  Thanks!

ss

[Cisco Kid]

Thanks for the warning about the power supply ... but I'm well aware that issue  

I'm using a Mean Well S-320-12 12V, 25A Switching PSU (I use these for 226W peltiers in a Swiftech watercooling solution (I'm a watercooling computer builder if your wondering ... hehe) ... it will provide 12V @ 25amp continuously ... voltage is variable 10V - 13.2V ... so I have that problem solved)

heres a link with info ... not to expensive and this unit is also extremely small ... thought if your interested

http://www.cooltechnica.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=MWS32012SPS&Category_Code=PS

Seeing as I'll be supplying it somewhere in the ballpark of 12-13V the most current it should draw is 15 - 16amps (I = P/V  I = 200W/12V)

I'm more worried about the magnetic field

I think I found a product that will lessen the magnetic field without changing the sound characteristics of the speakers like a bucking magnetic sometimes does.

MagnetShield and Joint-Shield (which happens to be another from of MuMetal in an adhesive tape form) .... because just tape this stuff around the magnet in a few layers and it will typically reduce fields up to a factor of 2 or 3.  Sounds good me ... but the Joint-Shield stuff is a bit expensive seeing as is really MuMetal ... can you image trying to fabricate a shielding box out of this material ... talk about big dollars  

here a links if you need this material too.

http://www.lessemf.com/mag-shld.html#274

[Distortion]

Those Sony speakers may look nice, and they even don't sound too bad, but be really careful.  Sony Xplod's are the easiest speakers to blow out there.  Just don't push them very hard.  Those hard plastic cones come off in chunks when they blow.  They don't call them Xplod for nothing.

[Cisco Kid]

Those Sony speakers may look nice, and they even don't sound too bad, but be really careful.  Sony Xplod's are the easiest speakers to blow out there.  Just don't push them very hard.  Those hard plastic cones come off in chunks when they blow.  They don't call them Xplod for nothing.

I'm not going to crank them ... I just want nice sound with decent bass is all

I hope I don't end up fragging myself with them  

[Distortion]

Those Sony speakers may look nice, and they even don't sound too bad, but be really careful.  Sony Xplod's are the easiest speakers to blow out there.  Just don't push them very hard.  Those hard plastic cones come off in chunks when they blow.  They don't call them Xplod for nothing.

I'm not going to crank them ... I just want nice sound with decent bass is all

I hope I don't end up fragging myself with them  

Yeah, I work at Best Buy, so I've seen those things come and go many a time.  It's mostly the subwoofers that are notorious for coming off in chunks, but the speakers have been known to do it as well.  Every time I've worked in car audio (not that often, I'm a home audio guy) for more than a few hours, I've seen at least one Sony subwoofer get replaced on a service plan.  Just wear a helmet when you're playing, you'll be alright!

[SS427]

Sorry about getting a little of topic there.....Back to shielding.   Now this is only what I have read (no proof that it is correct).  

1)  Bucking Magnets will help.  I have read some post on other boards (don't remember where), that they can have an adverse affect on the sound quality.  Don't know if this for woofers, really loud sound or what.

2)  The materials you mentioned (Mu-Metal, etc.)

3)  Another post/discussion I came across was about using materials like plain old metal (the higher the ferrite content and the thicker the better).  It had something to do with the iron in the metal being able to "reduce" the effects of the magnetic field produced by the magnets.  It also discussed material that would have no effect.  They were aluminum and other non magnetic material.  Supposedly the field produced by the magnetics could pass right through.

If you are real concerned about damage from the speakers, I would rather be safe than sorry (speakers a whole lot cheaper than a monitor).  Another option is to check with Bob Roberts, he has shielded speakers listed on his site for a very reasonable price.

just my 2/5 of a nickel
  ss

[visciouslymamed]

1)  Bucking Magnets will help.

Correct. Probably the best (cheap) protection. This is how almost all shielded speakers are made. If properly done, then the magnetic field is very minimal.

2)  The materials you mentioned (Mu-Metal, etc.)

Mu-Metal works very well, but it is expensive. It was designed for applications (industrial) where option 1 & 3 were not applicable and / or feasable.

I worked with a similar material. I can't remeber the exact makeup, but it was basically a lead-enhanced iron.

3)  Another post/discussion I came across was about using materials like plain old metal (the higher the ferrite content and the thicker the better).

This is just creating a buffer. The ferrite absorbs some of the EMF. It will gradually become magnitized and lose its effectiveness.

Most newer pc monitors have metal a surround inside to protect the CRT and shield EMF. Most of the EMF is concentrated around the sides / top & bottom of the monitor.


I would highly recomend installing bucking magnets. Just use some that are about 1/2 to 3/4 weight of the magnets on the speakers (do not use one that is more than 3/4 weight).

If you are paranoid about the EMF, you could also install sheet metal between the speakers and the monitor also. This would still be much cheaper than Mu-Metal.

Hope this helped you out. Feel free to pm or email me if you have questions