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AUDIO FORUMS >> General Discussion and Support >> Speakers, 8 ohm vs 4 ohm
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Message started by NothingButTreble on 01/31/18 at 03:24:33

Title: Speakers, 8 ohm vs 4 ohm
Post by NothingButTreble on 01/31/18 at 03:24:33

I hope such a simple question is acceptable here, but hopefully the knowledgeable ones will help me understand.

With a speaker at 8 ohm, 99dB, and a speaker at 4 ohm, 96dB, will the volume be equal with the same amount of power (voltage) to each?

Why is the 8 ohm speaker so perfect for the Decware amps?

And is this chart:
https://www.decware.com/newsite/buyingguide.html
for 8 ohm speakers?

Wouldn't the chart be different for 4 ohm speakers?

I'm still not really understanding about this difference, and so far my research hasn't really clearly explained simply enough for me to understand.

Any help is appreciated.

Title: Re: Speakers, 8 ohm vs 4 ohm
Post by dank on 01/31/18 at 15:34:19

I'll take a stab at this (note: watts=voltage squared divided by ohms):

IN GENERAL, a tube amp will put out a fixed number of watts into a load whether it be 4 ohm or 8 ohm. In a test I set a zkit1 up to put out 2.83v into 8 ohms (1w) then changed the load to 4 ohms. The voltage dropped to 2.03v (still 1w).

IN GENERAL, a solid state amp will put out a fixed voltage no matter what the load. This means that the wattage will double if the load changes from 8 to 4 ohms. In a test I set a solid state amp up to put out 2.83v into 8 ohms (1w) then changed the load to 4 ohms. The voltage dropped to 2.73v or 1.86w into 4 ohms which is within 7.5% of doubling the 1w into 8 ohms.

So:
A solid state amp should drive your 8 ohm, 99 db speakers to 99 db (1w).
A solid state amp should drive your 4 ohm, 96 db speakers to (almost) 99 db (almost 2w).
A tube amp should drive your 8 ohm, 99 db speakers to 99 db (1w).
A tube amp should drive your 4 ohm, 96 db speakers to 96 db (1w).

I don't think the 8 ohm speaker is as important to Decware amps as the speaker's efficiency is. I think you can usually find a more efficient 8 ohm speaker than you can a 4 ohm speaker and that's whats better suited for a Decware amp. All things being equal, a 6 ohm speaker would probably be best for the amp.

Dan

Title: Re: Speakers, 8 ohm vs 4 ohm
Post by NothingButTreble on 01/31/18 at 20:36:29

Thank you so much, that's a very interesting experiment. I didn't think there would be such a difference between a tube amp and a solid state amp.

I had remembered one comment somewhere comparing the 8 ohm and 4 ohm speakers, and it was "if your amp can double-up."

I'm wondering too then, what volume (dB) is a normal listening level? I really haven't seen any data about that in the research I've done.

Title: Re: Speakers, 8 ohm vs 4 ohm
Post by ginny on 02/01/18 at 19:43:56

To find "your normal listening level" I would tell you to download a db meter app on your phone and measure the sound pressure level from your listening chair.

I listen between 80-85 db (average) from my listening chair, but i can only handle an hour or so at 85 before i need to turn it down a tad.

Title: Re: Speakers, 8 ohm vs 4 ohm
Post by metropolis7 on 02/01/18 at 21:06:18

How would a Decware (pentode designed) amp respond to a 2 ohm load compared to an 8 ohm load? If these speakers were 95dB?