What's up with my speaker system?

Aah hi Andrew; just finished talking about a very similar topic (see the previous disc on Ohms); in your particular case the situation may be somewhat related although your system is slightly more complicated.

The short answer is that your Marantz may not have adequate Wattag to handle the load for that system. The issue becomes one of adding up the resistance of speakers that are wired in series for each channel of the system. In all likelihood, if the speakers are ceiling mounted then it could be a mono signal path (summed stereo into mono), it would be advisable to find out how many of them are in the circuit, and the specifications of the speaker-specifically the wattage and Ohms rating (resistance basically), then you’ll be able to add up the collective resistance (impedance) of the circuit.

For example, if you had 4 speakers wired end-to-end in series, and each speaker carried a wattage rating of 20 watts @ 8 Ohms, then the total wattage necessary for that circuit would be 80 watts at 32 Ohms; however, the trick comes in the conversion.

If your amp is delivering 80 watts at 16 Ohms, then at 32 Ohms (increased impedance), the actual output wattage is cut in half. That is, your amp would only deliver 40 watts at 32 Ohms. Conversely, if you only had a single speaker to drive at 8 Ohms, then your amp would be able to deliver double its 16 Ohm wattage, which would be 160 Watts at 8 Ohms.

The result is that if you don’t have enough watts for your load (and taking into account the additive Impedance in a circuit with speakers (resistors) wired in series, chances are you’re underpowering your speakers. Underpowering is usually to blame for the symptom you’re describing, and I the case of most audio systems is the cause for speaker failure (you’d think it was from overpowering, when in reality it’s the opposite).

Lastly, the knob on the wall is just a variable resistor-it controls the current but has little to no I pact on the impedance of the speakers themselves.

sndfreQ is a good guy to have around these parts.

Ah! Of course!

Is there a correspondence to the frequency of sound and the amount of energy it takes to push the signal? Does bass take more wattage?

I’m guessing, then, that the way that the individual knobs work by increasing the resistance to circuit behind them… so, turning up the volume decreases the resistance, which is why that works but turning up the volume on the receiver doesn’t.

And what does “summed stereo in mono” mean? What’s the summed part? That you’re adding both signals together rather than cutting out half of it? I know that some of the speakers in the rooms are L/R stereo and others are mono.

Summed mono means that if you don’t have individual left- and right circuits, then your stereo audio signal must be summed together (think old school tv sets with the single speaker on the front grille) in order to hear the full audio programme. Otherwise, if you have “zones” of speakers in various rooms of the house then your living room will only hear the left channel while the kitchen will only hear the right.

So if you have a “whole house” situation where the speakers are ceiling flush-mounted, then you would want to somehow sum your left and right audio signals before the power amplification stage-there are specialized circuits involved called “summing amps” that merge left and tight signals in such a way that they don’t cancel each other out. This typically takes place inside the receiver unit whereby the receiver will have an option for either “mono out” or an ectromic processor/setting switch for “mono.” And in the caseof some receivers, there are actual “sets” of outputs for a “Main” system and a second “zone” that may be able to be configured for summed mono output; read up in the manual, as even in some (rare) cases this can be done post-amplification by way of “bridging” an amp’s output channels together (basically this means “hard-wiring” the left and right outputs together-very dangerous and potentially amp-blowing!!! Not for the faint of heart). But in pro applicaltions of this (especially permanent installs) it’s not uncommon for an engineer to bridge amp channels if the output is a single circuit (a series of speakers for example).

Feel free to PM me if you have any details you need help with…good luck and don’t blow yerself up!