looking for info on speaker and amp loads (prolly noob question) - AVS Forum
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post #1 of 11 Old 12-21-2012, 02:38 PM - Thread Starter
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There are some aspects of audio i'm still not all that clear about so i thought of posting it here where the experts hang out, sorry if this is a total noob question for some of ya.

From my basic physics education in high school i learnt that the higher the ohm value, the higher the resistance.

So a speaker of 8 ohm should offer more resistance to the amp then a 2 ohm speaker as far as i understand it.

When i look at decent amp specs, especially good ss models, this seems to makes sense as they usually deliver more power at 4 ohm or 2 ohm then they do at 8 ohm, the more expensive models seem to even double up, for example 100 watts at 8 ohm, 200 at 4 ohm and 400 at 2 ohm.

Then when i'm reading reviews of audio gear most reviewers warn when a speaker dips under 4 ohm to sometimes 2 or 1 ohm, and advise users to have a very powerfull amp.

This is where it gets unclear to me and i wonder if someone could elaborate, or give me some links to usefull websites.

note: i am familiar with speaker sensitivity and how this translates to power needed for obtaining a certain spl lever measured in decibels, my question are just about loads (and prolly a bit about current delivery from amp.

so my questions would be :


Q1 : Wich speaker loads require more power and why.
Q2: how come higher speaker loads like 8 ohm speakers over the entire frequency range apparently need so little power.
Q3 : i myself have some 4 ohm speakers with a 90 db 1w/1m sensitivity, how come they seem to be able to play louder and with more bass authority on a 100w at 8 ohm and 200w 4 ohm class A accuphase amp then on an 150 w at 8 ohm and 240w at 4 ohm emotiva xpa 200... Does it have something to do with the accuphase being able to deliver more current or what am i missing here.

Feel free to ad questions u think i should be asking myself.

Looking forward to your answers.
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post #2 of 11 Old 12-21-2012, 04:22 PM
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yeah, you answered your own question in question 3.

it has to do with how much current the amp can produce, which in turn determines how much power can be produced.

some manufacturers have creative methods for determining their power ratings, which makes comparisons difficult.

many amps are designed to produce full current only down to 4 ohms or so, so if you put a 2 ohm load in there, the amp will be over taxed and could be damaged from over heating.

your accuphase probably has a very large torroidal coil and lots of power capacitance.

now, the complicating factor. impedance depends on frequency, so if you dip too low at a frequency that doesn't require much power that is less likely to damage the rig than if you dip too low where you are really hitting the big spl.

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post #3 of 11 Old 12-21-2012, 04:36 PM
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Also you had it a bit backwards re resistance. Lower ohm = higher resistance. Hence why the output of an amp will be higher at a higher resistance. Think of it like forcing water through a small hose - more water volume = more pressure needed.
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post #4 of 11 Old 12-21-2012, 04:39 PM
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Quote:
Originally Posted by MikeyD360 View Post

Also you had it a bit backwards re resistance. Lower ohm = higher resistance. Hence why the output of an amp will be higher at a higher resistance. Think of it like forcing water through a small hose - more water volume = more pressure needed.
confused.gif

He had it right. You have it backward.
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post #5 of 11 Old 12-21-2012, 04:46 PM
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Quote:
Originally Posted by Stereodude View Post

confused.gif
He had it right. You have it backward.

You are quite right. Oops! eek.gif
I just learned biggrin.gif
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post #6 of 11 Old 12-22-2012, 09:30 AM - Thread Starter
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lol, well then it's till not clear to me why higher resistance seems to be easier to drive, and why much horn loudspeakers claim to have an easy to drive 8 ohm load over the entire spectrum... isn't a 1 ohm speaker much easier to drive then a 8 ohm??
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post #7 of 11 Old 12-22-2012, 09:37 AM
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Quote:
Originally Posted by denkiedenk View Post

There are some aspects of audio i'm still not all that clear about
Nor forum etiquette either, apparently. rolleyes.gif
Duplicate threads are considered bad form.
http://www.avsforum.com/t/1446685/amp-and-speaker-loads

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post #8 of 11 Old 12-22-2012, 01:03 PM
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Quote:
Originally Posted by denkiedenk View Post

lol, well then it's till not clear to me why higher resistance seems to be easier to drive, and why much horn loudspeakers claim to have an easy to drive 8 ohm load over the entire spectrum... isn't a 1 ohm speaker much easier to drive then a 8 ohm??

Read, or re-read the other anwer Bill provided, ... it's spot on.

A 1 ohm load is nearly a dead short.

A dynamic loudspeaker's impedance varies per freq, a quality amp (with plenty of current ability) amplifies the signal voltage, despite a wildly fluctuating impedance. When the impedance lowers, the current rises. Every amp has it's current limits, thus, lower impedance speaker loads are detrimental.

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post #9 of 11 Old 12-23-2012, 02:05 AM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

Nor forum etiquette either, apparently. rolleyes.gif
Duplicate threads are considered bad form.
http://www.avsforum.com/t/1446685/amp-and-speaker-loads


weird though, i looked first but didn't find this thread, apologies, but thanx for the link
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post #10 of 11 Old 12-23-2012, 02:07 AM - Thread Starter
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Quote:
Originally Posted by FOH View Post

Read, or re-read the other anwer Bill provided, ... it's spot on.
A 1 ohm load is nearly a dead short.
A dynamic loudspeaker's impedance varies per freq, a quality amp (with plenty of current ability) amplifies the signal voltage, despite a wildly fluctuating impedance. When the impedance lowers, the current rises. Every amp has it's current limits, thus, lower impedance speaker loads are detrimental.

i guess u are talking about bill's other thread, because he didn't answer here, but thanks, yes, it was very helpfull.
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post #11 of 11 Old 12-23-2012, 02:10 AM - Thread Starter
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damn, i'm having trouble finding the edit button, but i noticed i somehow doubleposted this thread in different categories, sorry bout that guys, i thought i had cancelled the post in the speaker section.
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