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Old 8th November 2005, 03:57 PM   #1
henkel is offline henkel  Malaysia
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Default How to change ohm value of speaker?

Hi all!

I am new here, and was just wondering if I can change the ohm value of my Scanspeak driver from 8 to 4 ohms, so that I can use it in the car audio application?

Can I add anything along the speaker cable to make thew amp thinks it's powering an 8 ohm driver?

Thanks.
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Old 8th November 2005, 09:42 PM   #2
chrisr is offline chrisr  United States
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you can't change the value of your speaker. if your looking to make a 4 ohm driver into a 8 ohm driver just add a 4 ohm resistor in series with it. but since it seems you looking to use this speaker for car audio that doesn't make much sence. btw an 8 ohm speaker will work just fine in your car it will just draw half the power.
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Old 9th November 2005, 03:28 AM   #3
henkel is offline henkel  Malaysia
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Thanks for the reply Chrisr.

I think there is a misundertsanding of my intention. Sorry for my misleading question.

My current speaker is rated 8ohms. I am using a car audio amp thats rated st 4ohms to power it. Hence, it's only drawing half the power.

I would like to make full use of the power, by tricking the amp to see the speaker as a 4ohm load instead of 8ohms.

Can I add something along the speaker wire (I am guessing like a cap, since you mentioned resistor earlier) and what value should the cap be?

I might be wrong, your your help is very much appreciated. Thanks.
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Old 9th November 2005, 03:42 AM   #4
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If you have a 2 channel bridgeable amp, then you can bridge it, and run the speaker that way. Each channel would see a 4 ohm load, and you would get the combined power from both channels into the speaker.
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Old 9th November 2005, 03:42 AM   #5
chrisr is offline chrisr  United States
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there's really nothing you can do to trick the amplifier into giving your 8 ohm speaker twice the power except for wiring two of those speakers in parallel.

edit: i forgot about bridging, but then you lose one of the channels in your amp.
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Old 9th November 2005, 04:54 AM   #6
henkel is offline henkel  Malaysia
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Thanks chrisr.

You've been a big help.
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Old 9th November 2005, 04:56 AM   #7
SY is offline SY  United States
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As others have said, no easy way, but if you're ambitious, you might try winding an autoformer. That may be more trouble than just using other drivers...
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Old 9th November 2005, 05:04 AM   #8
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escuse me
may i offer a suggestion for full power tricking the amp into thinking it is attached to a 4ohm speaker, try adding an 8 ohm
power resistor in parrallel with the speaker the power through
the resistror wont translate into sound though,amp tricked!
for sound however replace the resistor with a second 8ohm
speaker tricked again with sound! good huh?
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Old 9th November 2005, 10:32 PM   #9
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When you double the power on a speaker you only increase by three decibels, which is considered to be hte smallest amount the human ear can easily hear the difference in. Also if you take a look at impedance graphs of speakers, your 4 ohm speakers, may only be 4 ohms for a small range usually in the midband for a few thousand hertz, and the rest of time upwards of 8-100ohms.

If you are going for pure SPL just get a second woofer in parallel will give you a 4 ohm load.
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Old 10th November 2005, 12:49 AM   #10
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you didnt state wich scan-speak driver you are using but like bjackson mentioned imp. -ohms fluxuates within the bandwidth with music, if its a mid or midbass driver you might be better off as is, 8 ohm there will not be much difference
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