Computer and vibrations.

[Dkay]

Okay i think i am goung to put a comp in my truck and am a little worried about the vibrations and such from the subs.
Any ideas on what to do externally and internally?
Thanks

[Warthog]

You mean just to transport? I would think it would be ok as long as you didn't chuck it into the back storage area in the truck. Maybe wrap it in something soft - clothes, bubble wrap, etc. Computers are shipped by truck from across the country and usually survive just fine. ALthough I don't know how loud you're planning on having your subs. http://sysopt.earthweb.com/forum/smile.gif

Warthog

[jad1097]

MP3 player?

[Dkay]

Yes I mean as a permanat thing
They will be 4 Infinity perfect 12's with 3,500 watts going to them.

Thanks
If you can think of ANYTHING else please lemme know.
thanks

[BBA]

Hmmm....

Hard drives can take quite a bit of shocking, but vibrations tend to reduce their lifespan.

It's good for MP3's in heavy bass environments, but just don't expect it to be the longest lasting thing.

Find a shock isolation mount like those made for portable CD players.

[Warthog]

Oh my....that's a lot of power.

Warthog

[tonym]

Dkay,

Hmmmmmmmmmmmmmm. 3500 Watts. Watcha got connecting the speakers to the amp? Welding cable. P = I^2*R, and R=4 Ohms. That means that I = SQRT(3500/4) = 29.6A. That's a lot of current!! Now, V = I*R, so this means that the voltage across the speaker is 29.6*4 = 118.3V. The best bridge amplifiers will do a little over 2.5 times the raw DC input voltage as the peak AC output voltage. For your car, this raw DC input is 12Vdc, so the maximum available peak output voltage is 12*2.5 = 30Vdc. This corresponds to an RMS value of 0.707*30V = 21.2Vrms. This means that you have V^2/R watts of power available, or 21.2^2/4 = 112.5 Watts(rms).
And if you were able to muster 3500 continuous watts, you'd melt the **** out of your speaker's voice coils! Even the 122 Watts that I mention make the speakers quite hot!!!

But the 112 Watts is a more realistic number to me. Over 75W (per channel) in a car is deafening and bone crunching! Thirty-five hundred Watts would be sort of an "auditorium-in-a-car" experience! I can tell you that 15 Watts of sound power with really efficient speakers will make your ears bleed!!!

Where does the 3500 Watts come from??? You've got me curious!!!


Tony

[Warthog]

Seems like someone knows their stuff when it comes to speakers. http://sysopt.earthweb.com/forum/smile.gif

I'm curious too...

Warthog

[BBA]

tonym...

You never heard of dc-dc converters or PWM power supplies?

Anyway, your math is a little theoretically incorrect. Max power from a non-power supply type automotive amp is around 30-40W/channel bridged. 112W is definitely in teh 30-50v rail voltage designs.

[OuTpaTienT]

hehe, if those calculations are correct (& I'm sure they are) then his truck will need a serious suspension system...don't cha think? Because in addition to the vehicle's power plant (6 or 4 banger) his sound system is gonna need it's own internal combustion engine. And from the sounds of it, it'll probably need a Mopar "hemi" supercharged with a 6:71 blower...and why not throw in a nitrous oxide system to boot, just in case there happens to be a few humans within a 10 mile radius that haven't permanently damage their hearing yet, that'll show'em.

I seriously hope this vehicle is intended for show, to win some bizarre "best of" category. If it's not, if it's really for driving and listening to music...or for listing to "thump" (which isn't music), then all I got to say is you are a FOOL. You will be deaf before your 30. But if you're lucky, then every nut, bolt, screw, and other fastening devices will vibrate loose and the truck will literally fall apart piece by piece. I've known a number of people with similar vehicles over the years and I've yet to see one that isn't just one big rattle-trap after a year or two. Kinda funny actually...they always act surprised that their car is falling apart. Maybe you could lok-tight or silicone or even weld ALL the nuts/bolts/screws/etc.

Oh well, I don't mean to be insulting...but if you are really going to listen to music in a confined metal box with that kind of power then I just can't imagine that you wouldn't be jeopardizing your hearing. And if you are willing to risk permanent hearing loss (that means it's CAN'T be fixed by any doctor on this planet) just because you wanna have the loudest & most annoying thing on four wheels, then I'm sorry but that is just utterly stupid. (OTOH, if it IS going to be a "show car"...well, then good luck.)

[thekingofpain]

Whisperwatt makes a real cool 15kw generator on a trailer you could tow behind ya for all your "higher powered needs"... http://sysopt.earthweb.com/forum/smile.gif

[tonym]

BBA,

Oh, yeah...I've heard of DC-DC converters...been designing them for over 20 years!! Mostly military, avionics, computer and industrial power systems in the 1-20kW range. Have several patents too!! Most of my doctoral level work has been in the power conversion domain!

The 30V rail I quote is indicative of a boost converter creating a higher rail voltage, then "bridged" to get the higher p-p output voltage...but this doesn't answer the 3500W question!

Let's say that you do somehow boost the +12V supply rail to +100Vdc. And your output is 3500W (forget rms versus average for a moment). And your boost conversion efficiency is 85% (which is reasonable for a boost converter). The input power is 3500/.85 = 4118 Watts. This means that your boost converter dissipates 4118-3500 = 618 Watts. Big heat load! And really tough to cool. But this number pales in comparison to the 4118/12 = 343 Amperes of current drawn from the +12V supply rail. Most heavy-duty car/truck alternators are useful to 60A, so you're talking about a serious power source!!! And if you can provide the primary +12V power, the losses incurred in the cable/power distribution are huge unless you use bus bars and exotic/expensive techniques to get power from the super alternator.

So, I'm still wondering about that 3500 Watts???

Tony

[wtp]

wrap the computer with bubbles, or put it around foam that covers it in all sides. After, put it on a box. Then your safe, make sure the box doesn't bounce though. Then.... you can turn on your subs and listen to your music.. haha, don't turn it up TOO much. I'm not concerned too much about that safe computer, but about your ears. http://sysopt.earthweb.com/forum/wink.gif

wtp http://sysopt.earthweb.com/forum/smile.gif

[Warthog]

whoooooooshhhh!!! Right over my head. http://sysopt.earthweb.com/forum/smile.gif

You guys are gettin outta my league with all this tech talk.

Just waiting for Dkay to respond...

Warthog

[john robbinson]

go to crutchfeild search the web and order one of thier cataloges its free. ive been buying from them for years. even before i discovered PC. over 1000 car stereos,speakers,and amps. plus home audio and video. they sell several car cds that play burned mp3. whats great about them when you order a stereo or speakers they give you custom brackets, wirring harnesses and instuctions for your car specifically and great return policy!

oh and im awed by you tman!
the last post that awed me was the designer from amd in overclockers forum.


[This message has been edited by john robbinson (edited 06-13-2000).]

[shadow]

This car wattage stuff has really got out of hand. Being an electronics technician (not an engineer like tonym) I know about Mr. Ohm and his laws. 3500 watts is incredible power and needs some serious amperage.

My home stereo (separate power amp) is rated at 120 rms watts x2 connected to speakers with an efficiency of 103db@1watt@1metre. The amp has some serious weight to it and certainly doesnt put out a continuous stream of 120 watts. It may hit a 120-240W level for some instantaneous peaks here and there. To run the amp at a high volume level with the efficient speakers in a normal sized room with alot of wattage soaking carpet, curtains, furniture, etc. is simply deafening and one would be nuts to sit in that kind of sound pressure for very long. In a car...3500 real watts? Not

[Dkay]

Okay look the 3500 watts is delivered by a modified earthquake PH-D2. Which will be wired at 1 ohm. So I don't see what all the fuss is about. And they are real watts shadow.
thanks for all the replies everyone.
At peak pull it will pull about 100 Amps from the 240 Amp Alt. I have. note, it will do this for just milliseconds
But mainly pull 50-60 on a normal basis

[F=ma]

If youre planning on hooking the computer up to the car, it'll prolly get real hairy. The Hard drive is pretty sensitive esp to vibrations... Heat may also be an issue.

If not, man just chuck that sh*t back there, unless you're running a pair Eclipse titanium 15"s with 1500 Watts powering them, Vibrations aren't gonna do jack to a box.

[tonym]

Dkay,

It sounds like you mean "put" permanently in your truck. Right?

Otherwise, as Warthog also wondered, why worry about the subs??

If you do intend on leaving the PC in your truck, then I suggest that you put a drop of Locktite on each of the screws in the unit. I'd be more worried about the low frequency road shocks and vibrations than I would about the subwoofer resonances. Also, it's not a bad idea to tie-wrap all the loose wires to the chassis. And, if you get real ambitious, you can glue a small piece of flame-retardent styrofoam the between the I/O cards, on the "free" end, with a piece between the last card and the bottom of the chassis. This prevents the cards from vibrating themselves loose.

Also, put a tie-wrap/twist-tie around the memory cards to prevent the latching mechanisms from moving once they're closed. Finally, if you've got a PII/III or Athlon, the processor might want to work itself free (even with the well-intentioned latching mechanism!) with shock/vibration, so you'll need to wrap the processor module with a large tie-wrap to secure the teeth of the latching mechanism such that they can't be acted upon by vibration.

One last thing, Any I/O cables need to be "retained" to the chassis...particluarly the PS2-style keyboard and mouse connectors. They are quite prone to nuisance disconnects from shocks and vibrations.

The remanider of the components in the PC yopu can't do anything about...HDDs, CDROMs, FDDs, etc. They will behave as they want to!

Remember, there are mechanical resonances in the PC that can't be quantified...each PC case is different, the wires hang in a different place and the options are different. You need to look at the mechanics and try to determine where a resonance (lots of displacement for very little input vibration/shock) MIGHT occur. Usually on objects at right angles to one-another or objects cantalievered within the case. If you find such components, shore them up with padding (careful not to obstruct cooling/airflow) or mechanically couple them to the chassis or each-other with additional brackets and supports.

A PC was never intended to survive in a mobile environment, so it's up to you to "ruggedize" it if you want to use it in that manner...


Tony

[Toadman]

Wow, speedbumps, potholes, and steep driveways would take on new importance.

[hd581]

Just don't burn any CD-R's unless you're at a stoplight, and you should be fine. http://sysopt.earthweb.com/forum/biggrin.gif

[pin-monkey]

Are you planning on overclocking the truck?


J/K Haven't seen sarcasm guy here yet!!

[bdunn]

how many alternators are in this truck? you may need to add one.

[shadow]

Didn't mean to get on your case about the stereo, just be careful with your ears. I know mine aint what it used to be thanks to numerous concerts and car stereos.

I see there are several car decks that decode MP3's now, I know Aiwa has one. That may be easier than mounting a computer in the truck, but not quite as cool either.
It sounds like fun, good luck!

[alondra]

I don't know that much about audio. but I suspect that wattage would equal what they use for the pa sys. at Staples Center. But years ago I had a 1KW (1000w) mobile ham transmitter in a car. powered by a war-surplus dynamotor. when I keyed it there was a noticeable drop,in speed/V8 engine. no human body could survive that much audio DB in a car even if you could get the speakers in it. I suspect a snow job here. http://sysopt.earthweb.com/forum/smile.gif

[tonym]

alondra,

You're on the right track. However, I did a little research and Dkay and other folks that purchase the meag amplifiers are getting a little "specification tickle" from the amplifier vendors!

An amplifier capable of providing 3500 continuous Watts would literally melt a hole through the car! And a continuous 3500W load would require ant least a 450A or better alternator in order to provide headroom for lights and other electric accessories.

The key here is that the vendors quote peak Watt capability. Thus, the amp can supply 3500 Watts for a transient time span (as Dkay replied, in the 10-100ms timeframe). Capacitors are used to provide the transient current rush. BUT, like everything else in life, there are other mitigating factors.

At 3500 Watts into a 1 Ohm load, the peak current is the square-root of 3500, or 59A. Now, if you use hookup wire in the 8 AWG range, the resistance per foot is 0.87 milliohms. If the wires connecting the sub is 12 feet long (probably longer, then there is 12 * 0.00087 * 2 (2 wires) = 21 milliohms. The power loss in the wires is 59^2 * 0.021 = 73 Watts. Those **** wires get hot if you have a thum-thump-thump rap song or the like ripping from your stereo.

This 73 Watt power loss reduces the effective output power from 3500 to 3430 Watts. The same analysis goes for connectors and for connections...by the time you're done you loose 100 or so peak Watts in the cables. And why??

A really efficient amplifier/sub combination will give you tremendous sound pressure and low distortion. At 3500W, I'm sure there are thermal distortions that are suffered by the subs, and these are perceived as audio distortion. Try it yourself...because of the logarithmic response of human hearing, it's tough to perceive a change from 0.1 Watt to 1 Watt, or from 1 Watt to 10 Watts. After 10 Watts, with a reasonable sound pressure, your ears basically stop hearing...they are clipping all the really loud noises trying to protect themselves. Any sound you hear (especially low frequency bass) comes into your cochlea through bone conduction!

IMHO, a 100W amplifier will give you enough sound power to give you thumpin' bass and great sound quality. The 3500 Watt amp is really a headroom waste...at some point you're spending a lot of dough to heat up wires and just make the quarter-panels go thump-thump-thump.

And one other thing, the damage you will do to your ears at the supra-200 Watt level with relatively efficient speakers in a closed metal box is phenominal. Incremental displacements of your ear drums and the corresponding excitation of the cochlea as the the thump-thump-thump displacements damage, numb then destroy the cilia in the cochlear fluid. Be advised of an adult life saying "Huh?" a lot! I can testify to this. Been there, done it.

You will know when it starts, as you'll get tinnitus (subtle ringing) as a result of necrotic nerve ceels at the ciliae bases. High frequency perception and hearing loss is the first to go.

My advice, turn the volume down...you won't be known as the deaf guy in your elder years!


Tony

[alondra]

simple question
whats the point of the computer? ?


[This message has been edited by alondra (edited 06-16-2000).]

[Dkay]

Yeah thats why we don't use 8 AWG we use 1/0 AWG
***deleted***
The purpose s for MP3's and navigation

Play nice. -socalgal

[This message has been edited by socalgal (edited 06-17-2000).]

[BBA]

tonym

When I used to install custom car systems for Crutchfield and Audiophile, it was not uncommon to install several alternators over 200W each and extra batteries just for the audio.

Also, if you've ever seen a van or truck setup with 20 12" subwoofers and numerous mid/high speakers, you would be much less intent on argueing the 3500W aspect...I suspect you are too far removed from the field of car audio to really know about this kind of thing.

There is no limit on how much power a person may or may not put in their car...whether for show or for actual usage...why are you harping on this subject? Can't we just get along and answer the question asked originally?

[Dkay]

Thanks you SO much BBA
I knew I had a fellow car audio person somewhere!

[tonym]

Sorry!

I won't make that "giving my opinion" mistake thing here again! I'll stick to computers...OT stuff like stereo = bad! Common sense = off!

I guess my "jargon" touched an open nerve! But hey, it's your money and your ears!!!!!!

Have fun...

Tony

[jad1097]

I assume there will be a couple of 1+ farad capacitors and batteries in the trunk, right?
A car audio system is capable of 3,500 continuos watts is designed correctly.

If anyone has to to a decent car audio show you would be able to understand how it is possible.



I have also seen some truly awesome 100 watt and under systems that would blow away 500 watt+ systems. This is why the ISACA has a 100 watt and under class.


The addition to car audio could be compared to computer addition. Once you get the bug you need your fix. It's all about tweaking and is an art of it's own.

Check this pic of some wiring out. (http://www.gr8ride.com/articles/I'd/004664afz10z.jpg)


There also some links in this thread. http://sysopt.earthweb.com/forum/Forum1/HTML/004892.html

Joel did you ever get your car mp3 player working and installed?

Also check out this van, (http://www.gr8ride.com/cgi-bin/pm/common/feature.jsp?channel=Electronics&community=Extreme&oid=18244) ratted at 3,600 watts! I have seen this thing in competition and it is awesome.

[This message has been edited by jad1097 (edited 06-17-2000).]

[juandeez]

There has been some similar discussion about putting computers in cars at: http://www.sounddomain.com
They run a UBB very similar to this one. I highly recommend it!

[Twin]

The best course of action when mounting kit in your car is to go STIFF.........

The more flex and uncontrolled damping you introduce the more chance you have of undesirable resonance or Q being present.

Unless you intend on doing a proper study on the vibration characteristics of both your car (and normal driving conditions) and the unit, then go STIFF....

Hard mount all drives, PSU and boards and remove flex where possible. Try to rig some form of gantry to support the top edge of any PCI/ISA cards (the best solution is to use a MB with on board audio/video) and use some sealant to glue down any non-surface mount components.

Use 2.5" HDD's if available (less mass/gyroscopic precession)

Don't even atempt to use a standard CD-ROM on the move (these units will withstand 30g/11ms shocks Non-operational but do not cope well when operational)

Flat panels (for your display) freeze and can be damaged if started below -20c if you live in a VERY cold climate make sure the display is properly heated before applying power (switching the backlight on for 10mins before applying video works well(you will need to overstrike))

A word on power

Do not use a DC-AC inverter, these things are v inefficient and tend to have a very narrow input voltage range, it is better to use a 12v PC PSU these can be found here:
http://www.jarcom.com/inmotion/


Or you can build yourself a less complex unit (it is a little known fact that the -12v rail is a legacy from early ISA cards and is not used for most applications)

Hope this is of help:-))

[This message has been edited by Twin (edited 06-23-2000).]

[Drifus]

There is this little company called KENWOOD

Kenwood Z919/D919 Car Radio/MP3 Player

Maybe this would be easier!!!

[Twin]

Drifus

easier is not necessarily interesting, challenging or FUN

[Andy_L]

ISA or not, you will find it a little hard to use a Hard Drive without 12 V : ).

Laptop Hdd's will handle more vibration than standard pc hdd's, and converter cables are available.

Why not just use a laptop? That way you can use it for other things besides just in the auto?