help speakers and amp

homer1982

Hi all

Before we start I confess that I know nothing about speakers or Amps.
I got a present of a Sharp HI-Fi, I had also installed previously 3 ceiling speakers that are rated at 80W 8ohm but only 2 channels on the Amplifier. The spec of the Amplifier on the Hi-Fi is giving me the following:

Output Power - PMPO:120W
MPO: 60W(30W + 30W) 10%T.H.D.
RMS: 30W (15W + 15W) 10% T.H.D.
RMS: 24W (12W + 12W) 1% T.H.D.

Output terminals - Speakers: 4ohms 20Hz - 20kHz
Subwoofer Pre-out(audio signal):200mV/10k ohms at 70Hz

I have been trying to look up situations on how best to wire the speakers to the Amplifier as there are 3 of them and only 2 channels on the Amplifier.

Can anyone please help me?

TroutMask

It's going to be hard to balance the load.
First, can you post the model no. of the amp please?

homer1982

The Hi-Fi is:

Sharp XL-DAB151PH(BK)

TroutMask

OK there's a 4 ohm minimum load spec on the speaker outputs of the power amp section. If you go below this then you run the risk of blowing the amp.
So your options are: a) leave out one speaker and just connect each of the remaining ceiling speakers to an output; b) buy one more ceiling speaker identical to the other three, connect a pair of ceiling speakers in parallel to each output;
c) run it mismatched, with a single speaker on one side and a pair wired in parallel to the other side.

Option b) is the most efficient and will deliver the most SPLs for the watts available.
Option c) is mismatched and one side will appear substantially louder than the other - maybe you can compensate with the balance control. It's not ideal - but technically feasible.
Option a) is less efficient, but will work well and is probably the way to go if volume is not an issue.

Note: you probably don't want to drive that unit too much anyway as they're a bit lightweight.

homer1982

Thanks for the help I have a fourth speaker so I think I'll wire them in parallel and have two speakers going to each channel. Someone said to wire two each in series instead to bring the impedance to 16ohms instead of the 4 ohms in parallel would this be good or bad?

TroutMask

Cool - option b) will give you max efficiency and power. It will work if you wire them in series, but you will only get about 3 Watts RMS power in that scenario.

In this case, i would only wire in series if the amp is getting very hot with a 4 ohm load. This is a consumer-grade lightweight - so don't expect too much level.

Speaker efficiency is going to be an issue with the perceived loudness too as this amp would usually expect a more sensitive speaker, and yours are rated at 80W?

Notes: make sure you observe polarity, and I would even go so far as test polarity on those drivers. A 1.5 volt AA alkaline (not a rechargable) cell should produce an excursion (i.e., it should come towards you) when placed momentarily:
Battery + to Speaker +
Battery - to Speaker -

For parallel it goes like this:
wire Speaker1 + to Speaker2 +
wire Speaker1 - to Speaker2 -
wire Amp + to Speakers1/2 +
wire Amp - to Speakers1/2 -

For series it goes like this:
Amp + to Speaker 1 +
Speaker1 - to Speaker2 +
Speaker2 - to Amp -

jay1912

homer1982 wrote: »

Hi all

Before we start I confess that I know nothing about speakers or Amps.
I got a present of a Sharp HI-Fi, I had also installed previously 3 ceiling speakers that are rated at 80W 8ohm but only 2 channels on the Amplifier. The spec of the Amplifier on the Hi-Fi is giving me the following:

Output Power - PMPO:120W
MPO: 60W(30W + 30W) 10%T.H.D.
RMS: 30W (15W + 15W) 10% T.H.D.
RMS: 24W (12W + 12W) 1% T.H.D.

Output terminals - Speakers: 4ohms 20Hz - 20kHz
Subwoofer Pre-out(audio signal):200mV/10k ohms at 70Hz

I have been trying to look up situations on how best to wire the speakers to the Amplifier as there are 3 of them and only 2 channels on the Amplifier.

Can anyone please help me?

Why not get a speaker input expander switch.. Very quick solution

homer1982

Thanks for your help with the amp and speakers I wired two sets in parallel and they seem to be working fine. Thanks for all the trouble you went to looking up the amp and all the info you sent back as i really appreciated the help.