# Use car speakers for a bookshelf stereo?



## thewatusi (Feb 1, 2011)

Sorry if this is a stupid question.

I'm building a little Iphone/Ipod dock system for the wife with doing it on the cheap as a top priority. It will just be used in the kitchen for some music while cooking/cleaning, so an over the top SQ setup is not the goal here. Ideally the entire system would be no more than 16" inches wide and about 6 inches tall -- just to give you a rough idea. It has to take up minimal counter space.

I plan on powering it with a small Tripath 2x25w RMS @ 2ohm / 2x20w RMS @ 4ohm amp that I found for cheap on fleabay.

My question is, what should I use for speakers? I've poked around on diyaudio and it's all completely over my head. I looked a bit at the raw drivers on PE, but once I get two woofers, two tweeters, and materials to make some crossovers it's going to cost me more than what I want to spend.

Would I be alright with just getting a cheap-o set of 5 1/4" coaxial car speakers rated at about 30w RMS @ 4ohm? A set of Pioneers can be had for around $35 on Amazon which seems like a reasonable price. At the very most I'd spend $50 on the speakers, but less is better. At the same time I don't want to put junk speakers in, if I'm going to go that way I might as well use some of the stock car speakers I have laying around.

The second part of my question is, car speakers are not designed to be installed in an enclosure, but obviously I'm looking to put whatever I get in a pretty small cabinet. Can a 5.25 coaxial speaker be installed in a small sealed enclosure, or would it be ideal to build a ported one?


Thanks in advance for your thoughts and suggestions.


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## erknjerk (Dec 24, 2010)

I'll be using my MB Quart 160QM in book shelf speakers. I think it'll need to be ported or a big enclosure cause car speakers are IB.


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## thewatusi (Feb 1, 2011)

^ that's right up my alley. I'm certainly not opposed to building my own set.

Would that configuration do alright with only getting around 20w RMS per side?


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## thewatusi (Feb 1, 2011)

Good deal, that's actually the same amp I just bought. I also ordered up a 12v-2a/5v-2a hard drive power supply so I can power the amp and charge the ipod without things getting too complicated.

What do you think about using this woofer to get a little more low end? Will I have enough power to drive it?


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## erknjerk (Dec 24, 2010)

I've got some Peerless 6.5s HDS. Do you think a generic Dayton XO would do it justice? Don't know which tweeter I want to use yet.


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## thewatusi (Feb 1, 2011)

XtremeRevolution said:


> Dude, this is HILARIOUS.


Ha, great minds think alike, huh? I was looking at the 4ohm version of that speaker and they're talking about the 8ohm. Will that make a huge difference in crossover design? Since it's a larger driver I'd like to squeeze as much power as I can out of the amp. Definitely let me know about the final crossover for that pair though.

Re: Greenmountain Audio, holy marketing BS batman. Makes me want to slap together $100 worth of crap and sell it for $2k+. That's a nice profit margin there.


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## thewatusi (Feb 1, 2011)

^ well I'm planning on using the little t-amp which is supposedly fine down to 2 ohms. Looking that the specs I think I'm better off building the first design you posted.

Could you clue me into the crossover diagram/parts list?


Say the Green Mountain guy puts $200 worth of parts/materials into a set of those speakers and it takes him 10 hours of labor. I'd value that level of craftsmanship at around $25/hr (at least that's how much you'd have to pay around here, other geographic areas vary of course), so the total cost to build is around $450 or so. The gross profit would then about $2k per set. No idea what his overhead costs are or how much volume he's doing, but I'd guess he has a pretty nice business going.


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## lucius (Oct 2, 2009)

would car speakers mess up home theatre amps?


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## ƒÆ§tÇµm (Feb 5, 2011)

think just gotta make sure ohms match


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## ƒÆ§tÇµm (Feb 5, 2011)

or impedance, as they call it


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## XtremeRevolution (Dec 3, 2010)

Impedance, and they call it that because its a nominal impedance. Its technically resistance, but resistance is stable, whereas impedance is more like a sweep. 

Most newer amplifiers can handle 4 ohms, although most are rated at 8 ohms.


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