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-   -   How to change ohm value of speaker? (http://www.diyaudio.com/forums/multi-way/67526-how-change-ohm-value-speaker.html)

henkel 8th November 2005 03:57 PM

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.

chrisr 8th November 2005 09:42 PM

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.

henkel 9th November 2005 03:28 AM

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.

xplod1236 9th November 2005 03:42 AM

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.

chrisr 9th November 2005 03:42 AM

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.

henkel 9th November 2005 04:54 AM

Thanks chrisr.

You've been a big help.

SY 9th November 2005 04:56 AM

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...

mastertech 9th November 2005 05:04 AM

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?

bjackson 9th November 2005 10:32 PM

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.

dodgerblue 10th November 2005 12:49 AM

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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