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Thread: Building speakers, i need help with ohms.. |
    
Bronze Member Username: Delirium
Post Number: 12
Registered: Jun-04
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| Posted on Friday, July 02, 2004 - 07:41 pm: |
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I would like to build some bookshelf speakers or maybe floorstanding speakers. I know that my receiver puts out 85 watts at 8ohms. Well one midrange is 8 ohms, and one tweeter is 8 ohms. So I can wire them to get either 4 ohms or 16 ohms right? So how can I get my bookshelf speakers to have the correct ohms? (8ohms)?
Imagine if I wanted two midrange and one tweeter (all 8 ohms).. how would I get 8 ohms out of that? Any help is appreciated... thanks! |
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Silver Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 121
Registered: Dec-03
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| Posted on Friday, July 02, 2004 - 09:01 pm: |
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Why is 8 ohms correct? Your receiver may perform better with a higher load. If you have a typical solid state amp 4 ohms is not going to hurt anything. Quite often when someone is building an MTM they will purchase 16 ohm drivers to wire in parallel for an 8 ohm load. Keep in mind that these numbers are the nominal load and do not accurately reflect the resistance changes that occur at different frequencies. You haven't mentioned how your crossover is going to affect things either. Anyway, in your case, go ahead and wire for 4 ohms. You'll be fine. |
Bronze Member Username: Natediggidy
Baltimore,
Maryland
U.S.A.
Post Number: 33
Registered: May-04
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| Posted on Friday, July 02, 2004 - 09:21 pm: |
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When used with a proper crossover, your speakers will present an 8-ohm load to your receiver. It works out this way because the crossover raises the mid's impedance above it's crossover point and raises the tweeter's impedance below it's crossover point. This is kind of oversimplifing, but the mid (or woofer) and the tweeter aren't playing the same thing at the same time so the impedance dosen't drop like wiring two of the same speakers in parallel. |
Silver Member Username: Kegger
MICHIGAN
Post Number: 630
Registered: Dec-03
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| Posted on Saturday, July 03, 2004 - 02:18 am: |
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nathan is correct! i think timn8ter missread your
post.
but yes if you build a crossover that your mid
only gets the mid frequencies and your tweeter
only gets the treble frequencies.
than when the music plays mid frequencies it will
go through the midrange speaker which is 8 ohms.
and when it plays treble frequencies it will go
through the tweeter which is 8 ohms.
keeping your curcuit at an 8 ohm load.
like nathan said this is breaking it down much
simplar than it is. but it should give you the
general idea.
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Silver Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 122
Registered: Dec-03
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| Posted on Saturday, July 03, 2004 - 09:05 am: |
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Yep, sorry about that. I glazed right over the fact we're talking about a 2 way system. I was assuming it was that same old "ohms" questions that gets asked so often. It's right up there with the "watts" question. Speakers are dynamic, not static, so the load changes considerably depending on the frequency. Also, the watts/ohms rating on most solid state equipment is more about marketing than performance. In tube amps, the nominal load becomes more critical but most are designed with 4 and 8 ohm taps and sometimes with 16. Still, in many cases, a high load is better than a low load and your amp will thank you for providing a twelve ohm load instead of 2 or 3. So, all that said, just go for it! |
Unregistered guest |
| Posted on Friday, July 09, 2004 - 07:26 am: |
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J.......don't wanna crimp your style or anything, so don't be offended by what i'm gonna tell you. Ok? If you need help with ohms, you really shouldn't be building your own speakers at this point. Get a handbook, like "The loudspeaker cookbook" and learn about drivers, crossovers, cabinets, bracing, Q factors, damping, etc. Anyone can put some drivers in a box, connect them to an amp and get noise out of them. If you want noise, buy Bose. If you wanna do it right, and be proud of what you designed, your gonna have to learn at VERY least, the basic math. This post is not meant to discourage you in any way....rather to steer you in the right direction. No hard feelings, please? If your NOT willing to put the time in to learn the math, go to www.partsexpress.com for some pre-made kits. |
J. Vigne Unregistered guest |
| Posted on Saturday, July 10, 2004 - 12:06 pm: |
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But I know which end of a soldering iron to hold. |
Bronze Member Username: Natediggidy
Baltimore,
Maryland
U.S.A.
Post Number: 42
Registered: May-04
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| Posted on Sunday, July 11, 2004 - 11:29 pm: |
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Umm, J.V., I think he meant the other guy (the original poster) =) |
J. Vigne Unregistered guest |
| Posted on Monday, July 12, 2004 - 11:49 am: |
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mybad |
Blue Bayou Unregistered guest |
| Posted on Sunday, July 25, 2004 - 08:50 am: |
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If I upgrade my midrange speakers from a set of cheap Jap 4 ohm to a better quality JBL (which happen to be 8 ohm), using the same crossover, how will the ohm change affect the sound? By the way, it's a 3 way system. Thanks |
Silver Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 123
Registered: Dec-03
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| Posted on Sunday, July 25, 2004 - 10:06 am: |
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It's going to sound terrible. Not because of the resistance rating but because you have no idea what you're doing. Crossovers are designed for the particular drivers and the particular application. Since you're obviously clueless about the whole process don't even try. Oh, by the way, the word is JAPANESE. |
