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BMW 3-Series (E90 E92) Forum
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Qustion about speaker ohm's
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05-20-2020, 12:28 AM | #1 |
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Qustion about speaker ohm's
My car has a 4ohm sub. logic 7 I believe. Can I install a 2ohm sub? will it damage the amp.? or sound bad? Can I add a resister to it?
I am almost getting it for free that's why I'm asking. Thanks. |
05-20-2020, 09:00 AM | #2 |
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A 2 Ohm sub will be louder than a 4 Ohm sub, and will demand more power due to a lower resistance. If your replacing the stock under-seat sub using the integrated amp I wouldn't recommend it.
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05-20-2020, 11:57 AM | #3 | |
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Quote:
In general you can always put in higher resistance speakers on an amplifier but lower can create problems. 2 ohm speakers draw twice the current so therefore twice the power at a given voltage so the amp has to be able to handle it. I am how the BMW amplifier is designed. The sensitivity (efficiency) of the speaker also plays an equal role. If you have an 91db sensitivity 4 ohm speaker it will be roughly the same SPL (sound pressure level) which is essentially volume that you would get with a 2Ohm 88db speaker. Power and SPL doubles every 3db. Car speakers are usually lower ohm (impedence) than home audio speakers because cars run at 12-14volts which really limits the amplifiers. Home amplifiers usually run 30-70V at the amplifier rails depending on the power requirements. -Rich
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2007 E70 X5 4.8i with 10" android screen Running 265/60/18 AT34s All Terrains (Mainly for road trips)
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05-20-2020, 02:48 PM | #4 |
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There was a thread in here someplace where people substituted
other stuff for the underseats, it was a long way back. The following thread has some info about the output chips https://www.e90post.com/forums/showthread.php?t=1144129 https://www.e90post.com/forums/attac...2&d=1435788287 pretty underwhelming at BMW specs the power a 10 percent distortion. |
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05-20-2020, 03:51 PM | #5 | |
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A lot of amps will list 2 RMS values Like : 250 RMS @ 2ohm 150 RMS @ 4ohm So, for example you have underneath subs that that have a 150 RMS @ 2ohm value with a peak of 500watts You would want to have the amp be 150 RMS @ 2ohm. The stock logic 7 amp might be around 60 watts per channel. The logic 7 subs are 4ohm. I don't know the RMS of the logic 7 amp. |
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