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Author Topic: Stupid Question - 4 ohm vs 8 ohm  (Read 1020 times)

Dennis Wiggins

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Stupid Question - 4 ohm vs 8 ohm
« on: October 24, 2021, 02:09:08 PM »

In general, amplifiers rated rated @4 ohms will produce "roughly" half that @ 8 ohms.  I get that part.  E^2/R.  In a cabinet that only one driver such as a bass or guitar combo, will going from 8-ohm to 4-ohm (using the same driver, but the 4-ohm version) "play louder" as it uses the full power available?

Or, is it just a wash.  My gut feeling is it's a wash, as the actual cone and its limit is the same. 

 <edit> These are not "tube" amps. 
« Last Edit: October 24, 2021, 02:49:15 PM by Dennis Wiggins »
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Steve-White

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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #1 on: October 24, 2021, 03:13:25 PM »

What type of amplifier are you talking about?  Looks like you did an edit eliminating tube amps.

For solid state PA amps the driver output will be relative to the amplifier performance, the power match of amp to driver and the driver performance relative to power compression and input material being reproduced - peak to average and such.

Simply stated it will be louder - how much louder is a case by case basis.

There could be adverse side effects such as overheating an amp that wasn't designed to run a 4 ohm load.

There are many things to consider and no simple "one size fits all" answer to your question.

If going that direction, I would consider doing a double down on the drivers which means more weight to haul around, possible a second cabinet and so on.

I've only dabbled a little with guitar amp/speaker setups, but have done a few bass and keyboard rigs with good results.
« Last Edit: October 24, 2021, 03:19:17 PM by Steve-White »
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Dennis Wiggins

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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #2 on: October 24, 2021, 03:36:54 PM »

What type of amplifier are you talking about?  Looks like you did an edit eliminating tube amps.

There are many things to consider and no simple "one size fits all" answer to your question.


The SS guitar or bass amp examples were purely hypothetical, but not that far out.  I'm sure it's done all the time - either an 8 to 4 swap, or a 4 to 8.  In my hypothetical, the amp's datasheet "power" is rated into 4 ohms, even though they are equipped with an 8-ohm driver. 

Specifically, I have a NIB 4-ohm EV DL18 driver and am considering finding an appropriate cab for it... but only if it would have more output than the typical equivalent 8-ohm DL18 driven by the same amp output.  It certainly would be a "one-off" project. 
« Last Edit: October 24, 2021, 03:42:56 PM by Dennis Wiggins »
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Steve-White

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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #3 on: October 24, 2021, 03:49:19 PM »

^^^ Do it to it and yes, it will have more output.

Any experimentation or modification involves a learning curve - get after it and have fun learning.  :)
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Brian Jojade

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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #4 on: October 24, 2021, 04:01:50 PM »

Assuming the 4 ohm and 8 ohm driver have identical specs, more power means a little louder, just as using an amp twice the size on the 8 ohm speaker.

Before taking other factors into consideration, you can expect about a 3 dB increase in output.
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Brian Jojade

John Roberts {JR}

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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #5 on: October 24, 2021, 05:23:06 PM »

In general, amplifiers rated rated @4 ohms will produce "roughly" half that @ 8 ohms.  I get that part.  E^2/R.  In a cabinet that only one driver such as a bass or guitar combo, will going from 8-ohm to 4-ohm (using the same driver, but the 4-ohm version) "play louder" as it uses the full power available?

Or, is it just a wash.  My gut feeling is it's a wash, as the actual cone and its limit is the same. 

 <edit> These are not "tube" amps.
All else equal the 4 ohm cabinet will develop twice the power driven by the same voltage as an 8 ohm version.

JR
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Dennis Wiggins

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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #6 on: October 24, 2021, 07:49:15 PM »

All else equal the 4 ohm cabinet will develop twice the power driven by the same voltage as an 8 ohm version.

JR

Assuming that's a 3db boost, I'm satisfied. 

Looking for a suitable (don't need anything significant below 40hz) empty cabinet 61063.  Tuned 35 would be good.
Preferable Bolt Pattern: 17.375" 
Dia. Cutout:  16.750"

...I can adjust to some extent.

https://images.thomann.de/pics/prod/157655.pdf

(11 y/o pointing at center)

Thanks to all!

« Last Edit: October 24, 2021, 09:31:12 PM by Dennis Wiggins »
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Steve-White

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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #7 on: October 24, 2021, 08:25:36 PM »

What is the intended purpose of the system?  Musical instrument or PA?  If MI, what?  Will it be used in conjunction with other loudspeaker components?
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Dennis Wiggins

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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #8 on: October 24, 2021, 08:43:02 PM »

What is the intended purpose of the system?  Musical instrument or PA?  If MI, what?  Will it be used in conjunction with other loudspeaker components?

It will be for playback enjoyment outdoors or indoors, replacing two ZxA1-Subs for gigs with no stairs where I need good clean bass.  Not for pubs or live bands.  For easy, cool, clear, but not-in-your-face listening.  Think: wine+jazz+standards (Sinatra, etcetera + pre-1970 jazz recordings). 

Right now, I use DXR12(s) with ZxA1-Sub(s) to good effect.  I would like to build another "old-school" system with Zx1(s) or (gasp!) Sx300(s) as tops - both of which I have.  I have the necessary amps + DSP.
« Last Edit: October 25, 2021, 09:58:44 PM by Dennis Wiggins »
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Re: Stupid Question - 4 ohm vs 8 ohm
« Reply #8 on: October 24, 2021, 08:43:02 PM »


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