Ohms?

ddoyle · 31st January 2009, 05:01 PM

I am working on a surround speaker project. I want to try using some auto speakers for the rear and side channels(7.1). I am looking at using some JBL's that were used in some of the higher end ford and lincolns. They have about a 4" woofer and 1" tweeter, self contained in a plastic housing. Now I have not tested these yet, assume they are 4 ohm, what do I need to make them compatable with my system, 8ohm. Resistors? My reasons, speakers are easy to find, cheap and already have a housing,may need to work on the appearance end, and have a small footprint. Thanks for your input!
Dan

HK26147 · 31st January 2009, 09:31 PM

If you verify that they are indeed 4 ohm cabs:
Wire 2 in series for 8 ohms with 1 cab inverted on top of the other...
So you have a 4", T, T, 4" module.
OR
you could use an L-pad and just burn off the excess power.

Iain McNeill · 31st January 2009, 10:45 PM

most respectable HT amps should be able to handle 4ohms as long as you don't do anything exotic with the crossovers.

It'll be louder and so the volume knob could go all the way to "self-destruct" (12)

Just start with the volume low and proceed carefully. Adding series resistance to the speaker will impact the bass

BlueWizard · 1st February 2009, 07:35 PM

Well, if these are Car speakers, then likely they are 4 ohms. That in and of itself shouldn't be a problem as has already been said; any respectable AV amp should be able to handle 4 ohm speakers.

However, the speakers in question are only 4", so it should be very easy to put two of them in one reasonably small cabinet, and wire them in series.

You could make the side speakers with angled fronts, in essence making the speakers di/bi-pole speakers. Have one of the 4" angled slightly to the front and the other angled slightly to the rear to disperse the sound a little better.

Then for the Rear speakers simply stack two 4" speakers together in a standard rectangular box, flat front, cabinet.

So, that solves the problem for Surround speakers, what were you planning to do for the fronts?

Steve/bluewizard

HK26147 · 1st February 2009, 07:53 PM

I am not familiar with JBL product that ddoyle mentioned.
I was given a small JBL satellite ( to repair ) that sounds very similar to what was mentioned - a 4" and a 1" piezo diaphragm.
It was not designed to be repaired - you can only buy a completed satellite.
This product was used by contractors on new construction and entertainment room renovations.
It didn't handle much power; a room has considerable more volume to fill then a car; so I thought wiring 2 in series would be prudent.

ddoyle · 2nd February 2009, 03:28 AM

Thank you all for the replies. I will have my hands on the speakers this week. The front speakers I have been alternating between AR-3s, Mcintosh xd715s and wharfedale w70c. Have not made up my mind which I like best. Cntr is a Zetag kinima. currently running a pair of AR tsw110s for the sides and a pair of smaller Advents in the rear, mini monitors i think.

ddoyle · 3rd February 2009, 03:38 AM

they are indeed 4 ohm. here are a few shots of what i am working with. This is from the front, have not pulled a set out of the rear deck, they may be larger.

31st January 2009, 05:01 PM	#1
ddoyle diyAudio Member Join Date: Feb 2006 Location: oregon	Ohms? I am working on a surround speaker project. I want to try using some auto speakers for the rear and side channels(7.1). I am looking at using some JBL's that were used in some of the higher end ford and lincolns. They have about a 4" woofer and 1" tweeter, self contained in a plastic housing. Now I have not tested these yet, assume they are 4 ohm, what do I need to make them compatable with my system, 8ohm. Resistors? My reasons, speakers are easy to find, cheap and already have a housing,may need to work on the appearance end, and have a small footprint. Thanks for your input! Dan

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31st January 2009, 09:31 PM	#2
HK26147 diyAudio Member Join Date: Jan 2008	If you verify that they are indeed 4 ohm cabs: Wire 2 in series for 8 ohms with 1 cab inverted on top of the other... So you have a 4", T, T, 4" module. OR you could use an L-pad and just burn off the excess power.

31st January 2009, 10:45 PM	#3
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	most respectable HT amps should be able to handle 4ohms as long as you don't do anything exotic with the crossovers. It'll be louder and so the volume knob could go all the way to "self-destruct" (12) Just start with the volume low and proceed carefully. Adding series resistance to the speaker will impact the bass

1st February 2009, 07:35 PM	#4
BlueWizard diyAudio Member Join Date: Jun 2007	Well, if these are Car speakers, then likely they are 4 ohms. That in and of itself shouldn't be a problem as has already been said; any respectable AV amp should be able to handle 4 ohm speakers. However, the speakers in question are only 4", so it should be very easy to put two of them in one reasonably small cabinet, and wire them in series. You could make the side speakers with angled fronts, in essence making the speakers di/bi-pole speakers. Have one of the 4" angled slightly to the front and the other angled slightly to the rear to disperse the sound a little better. Then for the Rear speakers simply stack two 4" speakers together in a standard rectangular box, flat front, cabinet. So, that solves the problem for Surround speakers, what were you planning to do for the fronts? Steve/bluewizard

1st February 2009, 07:53 PM	#5
HK26147 diyAudio Member Join Date: Jan 2008	I am not familiar with JBL product that ddoyle mentioned. I was given a small JBL satellite ( to repair ) that sounds very similar to what was mentioned - a 4" and a 1" piezo diaphragm. It was not designed to be repaired - you can only buy a completed satellite. This product was used by contractors on new construction and entertainment room renovations. It didn't handle much power; a room has considerable more volume to fill then a car; so I thought wiring 2 in series would be prudent.

2nd February 2009, 03:28 AM	#6
ddoyle diyAudio Member Join Date: Feb 2006 Location: oregon	Thank you all for the replies. I will have my hands on the speakers this week. The front speakers I have been alternating between AR-3s, Mcintosh xd715s and wharfedale w70c. Have not made up my mind which I like best. Cntr is a Zetag kinima. currently running a pair of AR tsw110s for the sides and a pair of smaller Advents in the rear, mini monitors i think.

3rd February 2009, 03:38 AM	#7
ddoyle diyAudio Member Join Date: Feb 2006 Location: oregon	they are indeed 4 ohm. here are a few shots of what i am working with. This is from the front, have not pulled a set out of the rear deck, they may be larger.

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