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Can someone answer this for me???? (Amp/Speaker Question)

Old 08-31-2009, 08:17 PM
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Question Can someone answer this for me???? (Amp/Speaker Question)

Here's the scenario:

System A: Amp "A" has a rated power of 125 w/channel at 4 ohms. It is connected to two sets of components (8 speakers, 4 ohms each pair).

System B: Amp "B" is a two channel amp capable of 125 w/channel at two ohms. It is connected to same set of components, therefore seeing a 2 ohm load.

Question is: Is the overall system power the same or is system "a" going to be louder than system "b"? Or is the difference inaudible?

TIA
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Old 08-31-2009, 08:26 PM
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Originally Posted by toomuchuv View Post
Here's the scenario:

System A: Amp "A" has a rated power of 125 w/channel at 4 ohms. It is connected to two sets of components (8 speakers, 4 ohms each pair).

System B: Amp "B" is a two channel amp capable of 125 w/channel at two ohms. It is connected to same set of components, therefore seeing a 2 ohm load.

Question is: Is the overall system power the same or is system "a" going to be louder than system "b"? Or is the difference inaudible?

TIA
please rephrase your question with answers to the following question:
what is the impedance of each speaker?
how many are connected to each channel of the amp.
how are you connecting them? Series? Parallel? combination?
and .. why are you using so many speakers?
what can the 125 watt per channel into 4 ohms deliver into 2 ohms?
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Old 08-31-2009, 10:40 PM
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It sounds like with system A, hes running 4 sets of components(probably 2 up front 2 in the back) with crossovers so the oerall impedance is 4ohm at the crossover right? im not sure about system b, maybe hes wiring the components together to drop the load to 2ohm? if thats the case then system A would be better because u would have 125watts running to each set of comps VS 125 for 2sets of comps....i think...
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Old 09-01-2009, 04:56 AM
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Originally Posted by ChristianM View Post
It sounds like with system A, hes running 4 sets of components(probably 2 up front 2 in the back) with crossovers so the oerall impedance is 4ohm at the crossover right? im not sure about system b, maybe hes wiring the components together to drop the load to 2ohm? if thats the case then system A would be better because u would have 125watts running to each set of comps VS 125 for 2sets of comps....i think...
Exactly.....two sets, 4 ohm at the crossover. System "b" has the two sets wired in parallel, therefore createing a two ohm load for the amp.
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Old 09-01-2009, 05:38 AM
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hmm then imo i would say run the 4channel since each set of speakers will get 125watts/comp set vs 125watts/2 component sets....
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Old 09-02-2009, 03:06 PM
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Originally Posted by toomuchuv View Post
Here's the scenario:

System A: Amp "A" has a rated power of 125 w/channel at 4 ohms. It is connected to two sets of components (8 speakers, 4 ohms each pair).

System B: Amp "B" is a two channel amp capable of 125 w/channel at two ohms. It is connected to same set of components, therefore seeing a 2 ohm load.

Question is: Is the overall system power the same or is system "a" going to be louder than system "b"? Or is the difference inaudible?

TIA
If the power of 125 watts stays the same at 4 Ohms as it does in 2 Ohms, than IMO, both will provide the same SPL output. Although one would be more pleasant to listen to than the other.
The 2 Ohm load system will sound "harsh".
I hope that answers the question
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Old 09-02-2009, 03:15 PM
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I think the question is more related to power and spl.
as far as power is concerned, there are too many people with misconceptions about power, and specifications.
An amplifier that is rated to provide 100w/ch @ 4 Ohms, will be able to provide 200w/ch @ 2 Ohms, and 400w/ch @ 1 Ohm.
Notice the math?
Any speaker's impedance, changes in relation to the voice coil position in the magnet, and as "music" is playing that impedance changes wildely. unlike a test tone, or a resistor attached to the amplifier, which presents a constant load, unlike a speaker, being a reactive load to an amplifier.
Forget specs, they mean less than nothing when it comes to music.
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Old 09-02-2009, 07:26 PM
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Originally Posted by Eli47 View Post
I think the question is more related to power and spl.
as far as power is concerned, there are too many people with misconceptions about power, and specifications.
An amplifier that is rated to provide 100w/ch @ 4 Ohms, will be able to provide 200w/ch @ 2 Ohms, and 400w/ch @ 1 Ohm.
Notice the math?
Any speaker's impedance, changes in relation to the voice coil position in the magnet, and as "music" is playing that impedance changes wildely. unlike a test tone, or a resistor attached to the amplifier, which presents a constant load, unlike a speaker, being a reactive load to an amplifier.
Forget specs, they mean less than nothing when it comes to music.
Thanks for the reply. I understand ohms law but where it gets fuzzy for me is this: the amp power doubles because of the decreased impedence but now because each channel of the two channel amp is pushing two sets of components, does each set "see" that increase in power or is it halved again because of the number of components. Whereas a four channel amp puts out 125 watts to EACH component (therefore each set of speakers "sees" the full 125 watts) Do I make any sense or am I not explaining myself properly?

Thanks again! Here's a little diagram of what I am trying to explain. Which "system" would have more power from the speakers and sound best?

System “A” 2 channel amp (75 W/C @ 4 ohms) bridged to two ohms

AMP (125 W/channel at 2 ohms)
------ + COMP ---------- + Comp
------ _ 4 ohm ---------- _ 4 ohm

----- + Comp ------------ + Comp
---- - 4 ohm ----------- _ 4 ohm

System “B” 4 channel amp

AMP (125 W/channel at 4 ohms)
--------------- + Comp
--------------- - 4 ohm

--------------- + Comp
--------------- - 4 ohm

---------------- + Comp
----------------- - 4 ohm

--------------- + Comp
--------------- - 4 ohm
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Old 09-02-2009, 08:47 PM
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Originally Posted by toomuchuv View Post
Thanks for the reply. I understand ohms law but where it gets fuzzy for me is this: the amp power doubles because of the decreased impedence but now because each channel of the two channel amp is pushing two sets of components, does each set "see" that increase in power or is it halved again because of the number of components. Whereas a four channel amp puts out 125 watts to EACH component (therefore each set of speakers "sees" the full 125 watts) Do I make any sense or am I not explaining myself properly?

Thanks again! Here's a little diagram of what I am trying to explain. Which "system" would have more power from the speakers and sound best?

System A 2 channel amp (75 W/C @ 4 ohms) bridged to two ohms

AMP (125 W/channel at 2 ohms)
------ + COMP ---------- + Comp
------ _ 4 ohm ---------- _ 4 ohm

----- + Comp ------------ + Comp
---- - 4 ohm ----------- _ 4 ohm

System B 4 channel amp

AMP (125 W/channel at 4 ohms)
--------------- + Comp
--------------- - 4 ohm

--------------- + Comp
--------------- - 4 ohm

---------------- + Comp
----------------- - 4 ohm

--------------- + Comp
--------------- - 4 ohm

System 'A' is not bridged, the individual channels are loaded down to a nominal 2ohm load each......

I would use the 4 channel.....cleaner power, still have fader function and individual crossover setting ability.......

Forget about power to individual drivers....the crossover is there to make sure each driver gets the right range of frequencies to produce sound at an even volume level across the whole range. It is possible to over-power the set to the point where the tweeter will die, but that is more a function of a smaller voice coil being unable to radiate heat fast enough to keep working than anything else.

HTH
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Old 09-04-2009, 08:44 PM
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Originally Posted by toomuchuv View Post
Thanks for the reply. I understand ohms law but where it gets fuzzy for me is this: the amp power doubles because of the decreased impedence but now because each channel of the two channel amp is pushing two sets of components, does each set "see" that increase in power or is it halved again because of the number of components. Whereas a four channel amp puts out 125 watts to EACH component (therefore each set of speakers "sees" the full 125 watts) Do I make any sense or am I not explaining myself properly?

Thanks again! Here's a little diagram of what I am trying to explain. Which "system" would have more power from the speakers and sound best?

System A 2 channel amp (75 W/C @ 4 ohms) bridged to two ohms

AMP (125 W/channel at 2 ohms)
------ + COMP ---------- + Comp
------ _ 4 ohm ---------- _ 4 ohm

----- + Comp ------------ + Comp
---- - 4 ohm ----------- _ 4 ohm

System B 4 channel amp

AMP (125 W/channel at 4 ohms)
--------------- + Comp
--------------- - 4 ohm

--------------- + Comp
--------------- - 4 ohm

---------------- + Comp
----------------- - 4 ohm

--------------- + Comp
--------------- - 4 ohm
Ohm's Law although applies in this case, you're more concerned about "Kirchoff's Law"(how much power is each piece getting), trying to figure which system has more power, or sounds better.
If you're providing the same power, but at different impedance, than nothing changes volume wise.
If sound quality is what you're after, than the 4Ohm system will sound better, the 2 Ohm system will "seem" louder, but will just be more aggressive, with less control over the speakers. (Damping factor)
I agree with BigRed, forget power, be more concerned with the end result.
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