Mono Amps that are Internally Paralleled?

My friend and I were having a discussion tonight about mono amps that are "internaly wired in parallel". Some examples would be Phoenix Gold's Xenon amps, Sony's Xplod Signature Series, ect.

He asked two people who work at an audio shop about this and this is the answer they gave him.

"If you put a 4 ohm woofer on that amp, it will see 2 ohms, and power it accordingly, because internally it halves the impedance of the load."

I think this is total BS fed to him from uninformed salesmen. My argument is that,

"What "internally wired in parallel" means is that you're going to get the exact same signal on both outputs. It dosen't matter which + terminal you use or which - you use, it will work either way. And no it does not half the woofers impedance."

Somebody, please clarify this point and put an end to this nonsence that has so many people confused.

Paul

the guy at the stereo shop must have been trying to sell you something you dont need. every amp sees the actual ohm load put to it. no amp changes impedence of speakers.

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You are correct. The amplifier is a one channel amp, and both positive terminals are identical, INSIDE the amp, and the same applies to the negative terminal... A 4 ohm woofer is a 4 ohm load. End of story.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

What about those amps that have optimum power at at 2 or 4 ohms? Like JL claims that it will do the so called "500wrms" at 2 or 4 ohms.  It sounds as if there are some parts left out of this one, maybe some misconstrued info.

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A mono amp is internally wired in parallel only if it has multiple speaker terminals of the same polarity.  Connectors of the same polarity are connected together and originate from a common source.

If you connect a load to ONE set of terminals, there is no parallel connection within the amp.  Although there are two connectors of each polarity, there is only one load on one connector....so there is no parallel connection.

But if you use BOTH sets of output terminals on the mono amp, the load will be paralleled within the amp.  ALL connections of the same polarity are parallel connections, and  the calculation for parallel wiring will apply.

Here is one of the Phoenix Gold Xenon amps as shown in the manual:

If BOTH +/- outputs have loads attached, let's say 4 ohms on each one....the result would be power output at 2 ohms.  But if only ONE +/- is connected to a load of 4 ohms, the power output would be at 4 ohms.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Great explination Steve, completely understood now.

Paul

Stevdart:

Okay, but then why even bother with the multiple speaker outputs anyway? From reading your explanation it looks like there isn't any difference from wiring the speakers together or at the amp? Wouldn't it just be easier to wire subs together inside the box or whatever?

Am I missing something b/c it looks to me like completely ignoring the 2nd set of outputs would not change the operation of the amplifier in anyway..?

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"I'm finished!" - Daniel Plainview

I'm pretty sure that is the point. That it will work as a straight series or 1:1 wiring scheme. But if you want to do a parallel scheme, it is all right there, you can just wire each sub to each terminal and it is done for you. It's a different look and approach to a wiring scheme, that's all. Atleast if I understand correctly. :)

(took me a minute to figure out how the f a mono amp had 2 terminals, hah)

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sedate, it's something that the amplifier makers probably should have left alone...just one set of terminals for a mono amp is easier to understand.  Because you're right, the individual loads can usually just as easily be connected together BEFORE they're attached to the amp.  It really does add confusion to an already confusing (for most people) concept.  I guess the proliferation of multiple voice coil subwoofers and the use of multiple subs has been the reason to add more terminals....there are cases where you can't easily get the wiring done the way you want it and end up with just one set of wires going to the amp.

And yes, ignoring the second set of outputs is fine.  It's a mono amp, so one + and one - is all it's going to have to work with.  Just wait until one of these fine makers decides to put quadruple terminals on a mono amp......that'll be fun to figure out!

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Some amps have two sets of terminals for various reasons.

(1) ease of connectivity. If you have two separate boxes and the amp mounts in the center between the two.

(2) cost of manufacturing. It may cost the manufacturer more to use the single terminal block over the double terminal block. This is due to them now having to make a new end cap for the amps heatsink and a second setup to have the endcap silkscreened.

If it is a mono amp from the outset, the laod you give it is the load it sees. Only a 2 channel or multichannel amp will see half the load when it is bridged.

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