Question Wiring speakers

I like pioneer

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Hello all, I am new here and am looking for some general advice

I currently have an old Pioneer amplifier (A-405r) which is perfect for me . I don't use it often nor do I play it very loud and I mostly play music for 2 hours at most.

a405grog.jpg

I have 4 pioneer speakers which I have wired up using all 4 terminals of the amp.

However recently whilst I was moving my room I got a bit curious and using a very high tech device (free app from playstore) I measured the dB the speakers were pushing out.

My findings were that it made no difference whether I was using all 4 terminals to power the speakers or just the 2 top terminals.

Neither my ears nor phone could perceive a difference.

Can anyone explain in simple terms why that is? Or would I be right in saying the amp splits the power between A and B if there's anything connected to the B terminal?

Now my next question is as follows.

If I wanted to join 2 x 16.5cm speakers to that amplifier using only the A terminals.

Should I use the positive wire to both positive terminals on the speakers and likewise the negative to negatives.

Or

From the amp go positive to positive on speaker 1 and then positive from speaker 1 to negative in speaker 2 and likewise for the negative.

Would this make any difference to anything?

Thanks a lot for your time and consideration.
 
It may have FOUR Speaker terminals, but inside it only has TWO Amps (stereo), or more accurately two amp channels. Internally all those RED terminals are connected to the same amp, RED-A (left), and RED-B (left) internally are the same point. Same with RED-A (right) and RED-B (right), inside the amp both are connected to the same Right Channel Amplifier.

So, reasonably you would not expect any difference if you connect all the speaker to one set of terminals, or if you connect them to both sets of terminals. Inside, you only have two amps even if you have 10 or 100 pair of external terminals.

However, when connecting multiple speakers to a given amp channel, you have to make sure the combined impedance of those speakers falls within the working range of the amp. In most case, with FOUR speakers (2 per channel), each speaker must be 8 ohms or higher.

When you combine speakers, the resulting impedance goes down. Two 8 ohm speakers results in a 4 ohm load, that is the low limit on most common consumer amps. There are a few PA amps that will tolerate loads as low as 2 ohms, but that is rare to non-existent in HiFi Stereo or AV amps.

The problems with combining multiple speakers on an Amp Channel is that the impedance goes down, but at the same time. because of lower impedance, the demand for Electrical Current goes up. The Power Supply has a limited ability to deliver Current, and the more Current it delivers, the hotter the amp gets. At some point the amp will get hot enough to shut itself down. If your amp has not Shut Down on its own, that is an indication that you are using it within its reasonable limits.

Does that help?

Steve/bluewizard
 
It may have FOUR Speaker terminals, but inside it only has TWO Amp (stereo). Internally all those RED terminal are connected to the same amp, RED-A (left), and RED-B (left) internally are the same point. Same with RED-A (right) and RED-B (right), inside the amp both are connected to the same Right Channel Amplifier.

So, reasonably you would not expect any difference if you connect all the speaker to one set of terminals, or if you connect them to both sets of terminals. Inside, you only have two amps even if you have 10 or 100 pair of external terminals.

However, when connecting multiple speakers to a given amp channel, you have to make sure the combined impedance of those speakers falls within the working range of the amp. In most case, with FOUR speakers (2 per channel), each speaker must be 8 ohms or higher.

When you combine speakers, the resulting impedance goes down. Two 8 ohm speakers results in a 4 ohm load, that is the low limit on most common consumer amps. There are a few PA amps that will tolerate loads as low as 2 ohms, but that is rare to non-existent in HiFi Stereo or AV amps.

The problems with combining multiple speakers on an Amp Channel is that the impedance goes down, but at the same time. because of lower impedance, the demand for Current goes up. The Power Supply has a limited ability to deliver Current, and the more Current it delivers, the hotter the amp gets. At some point the amp will get hot enough to shut itself down. If your amp has not Shut Down on its own, that is an indication that you are using it within its reasonable limits.

Does that help?

Steve/bluewizard


Thank you very much that had cleared up some questions. Especially on how to wire up the speakers. The amp is rated at 45w at 8 ohms so I need to make sure I keep the impedance at 8ohms.

My amp has never shut itself off because of heat or anything as i said I don't use it for extended amount of times and never have gone over 50% on the volume.

Thank you for all your help it all makes perfect sense now.
 
The Power Rating of an amp is unrelated to the range of impedance it can handle.

All amps are rated to 8 ohms because that is the legal Federal Trade Commission requirement (FTC in the USA, other standards bodies in the UK/EU). That is so all amps can be fairly compared to each other. They are all rated to the same legal standard.

However, most amps can function with a combined speaker load in the range of 4 ohms to 16 ohms. Below 4 ohms the heat and demand for current become too high. Above 16 ohms and the amp becomes unstable.

Two 8 ohm speakers in parallel, which is how they would be when connected to the speaker terminals, result in 4 ohms total load. Give that your amp has not shut down, you are probably OK with the 4 speakers you have. However, each speaker should be 8 ohms. Because when two 8 ohm are combined, the result is 4 ohms, the limit of the amp.

To determine the combined load of speakers all of equal impedance, simple take the impedance of ONE Speaker, and divide it by the total number of speakers.

TWO 8 ohms speakers -

Rt = R1/n = 8/2 = 4 ohms

If the speakers are not equal size, you multiply the two impedance and divide by the sum of the impedance.

6 ohms speakers and an 8 ohm speaker -

Rt = (R1 x R2) / (R1 + R2) = (6 x 8) / (6 + 8) = (48) / (14) = 3.43 ohms

3.43 ohms is too low for most amps, at very moderate volume it will probably work, but as the volume goes higher, the heat will be too intense, and the amp will shut down.

Steve/bluewizard
 

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