Volume/Power quite bad - help me with my setup!

  • 12 April 2007
  • 2 replies
  • 794 views

Userlevel 2
Ok, like many other non-audiophiles I have jumped into the depths of ohms, wattage, channels etc and am just looking for a simple setup.

So here goes:
I have a ZP100 hooked to a impedance protected speaker switch that can output 8 pairs of speakers. There are 4 8 ohm pairs active all capable of being turned on or off. When each subsequent pair is switched on the volume cuts dramatically. It is so bad, that when only 2 pairs are on the controller has to be at 25% volume to hear anything and worse yet when all 4 are on at 75% volume it is louder than speech. So logic not knowledge (be nice here 😉 tells me there is not enough wattage powering the speakers (y/n?). Also The impedance protection may also be culprit (y/n?).

So in short if I used a ZP80 with a strong amp (like a Carver TFM-25 225 per channel 8 ohms) would that make the difference as it would be providing more power to all 8 speakers? Do the additional speakers decrease the ohms? And why do i care about ohms anyway? (again, be nice, I know things you don't)

I want to keep this setup as all speakers in this "zone" of my house have wires clustered in one place. The other parts of my house will have their own ZP's so it makes little sense to break this setup.

Additionally, I have little interest in a "multiroom" amp as the are too expensive and since I already have the speaker switch why bother with the expense. Obviously, I love my music but am not a freak about it...yet.

Thanks for the feedback.
/drew

2 replies

Userlevel 2
The impedance matching will not cause the speakers volume to change.

It is all down to the power rating of the ZP 100. Every time you double the amount of speakers, you are halving the volume level.

A more powerful amp is an option, but may produce new problems. If the amp is rated higher than your speakers and you have only one pair on, you may damage the speakers.
drewsky,

The real question is not exactly where you must operate the volume control, but is the sound level sufficient for your needs?

The impedance matching process will change the volume control's position for a given sonic output for a given speaker.
This is part of the physics.

It's harder to make a blanket statement of exactly what will happen to a room's acoustic level if the speakers operate in the same space, because the speakers tend to reinforce each other.

An audio amplifier is a constant voltage device. If you connect two pairs of identical speakers (in parallel) to the same amplifier, all speakers will give the same acoustic output and the amplifier will be working twice as hard. This is not necessarily a problem if the amplifier is operating within its rating.

As more speakers are connected in parallel to the amplifier, the effective impedance that the amplifier is working into is lowered (it can't count speakers, any more than a truck can count bricks, but if you cross the limit, something bad will happen). Two 8-Ohm speakers appear as a 4-Ohm load. If four pairs of 8-Ohm speakers are connected in parallel, the amplifier is working into a composite 2-Ohm load and there will be significant extra heat generated inside the amplifier. Since this extra heat is potentially damaging to the amplifier, a "protection" circuit is usually included to provide some defense against a bone headed consumer. Protection circuits are typically set to spring into action when the 4-Ohm threshold is crossed.

A ZP100 can safely drive two pairs of 8-Ohm speakers of a single 4-Ohm pair.

Beyond two pairs, external impedance matching or protection tricks must be used to prevent amplifier damage. Since these tricks alter the relationship between the use of the amplifier's output voltage and current, you can expect a shift in the volume control setting required for a given acoustic output from a given speaker.

While the human may have some difficulty accepting the new volume control setting, as long as the amplifier is operating within its design limits, it does not matter to the amplifier what volume setting you are using.

If the resulting acoustic output is too low, or you are uncomfortable operating at "9" instead of "4.5", additional amplification must be used.

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