A current project I am determining the direction that I am going to follow as regards a sound decoder and speakers. My preferred installation is two off 8 ohm speakers in series, driven by a 3 watt sound only decoder. This will give me 16 ohms impedence with resultant drop in overall volume.
My question relates to how appreciable difference will the extra speaker make to the installation. Basically, would there be a positive difference at all?
I just read the thirteen available history pages on the ‘other site’ and it seems that doubling the impedence (numerically) will halve the available wattage to each speaker. Thus with two 8 ohm speakers in series, each speaker will only receive one-quarter of the available wattage. Not really a very helpful situation. One suggestion was to use two 4 ohm speakers in series, retaining the original 8 ohm impedence.
Looks like a single speaker is preferable.
Tim, wire them in parallel instead of series
Rodney,
thankyou for your response, but unfortunately the decoder that I have chosen does not like to be driven at 4 ohms (two 8 ohm speakers in parallel). Quality decoders like Zimo are actually designed for 4 ohm applications, but alas not mine.
Tim,
I have wired three 5W 8ohm 7oz. magnet ferrite speakers in parallel with a Phoenix P8 Sound Card. This system is in my NW2 Cow & Calf powered by my C-10TL Carrier Board. The speaker in the C-10 has a square plastic cover over it and the other two are installed in the gas tank with baffeling around the cone forcing the sound down and out of the loco. I have been told by many customers and friends that this is the loudest system that they have ever heard in a loco, I think Rodney has even heard it. But, it works with very little dip in output.
Give it a try!
Rick Isard
Cordless Renovations, LLC
RCS America
Rick,
sounds very interesting. Alas, my decoder is only good for 8 ohms, unlike the Phoenix which may be driven down to 4 ohms. I have given up on multiple speakers as there seems little that one can do with an 8 ohm capable decoder and still maintain credible volume. I am going to a single speaker only.
Tim,
That’s ok, put some baffeling around the speaker cone to force the sound out and it will give you a richer, deaper sound.
Rick Isard
Cordless Renovations, LLC
RCS America
Tim , it is very possible to use a series parallel setup to allow more than a single speaker if you wish. I just finished an Aristo cab forward install with the Revolution with three speakers, one over each “engine” and a third in the tender for volume from a distance, if required.
It is important to understand that impedance IS NOT AN ABSOLUTE NUMBER. An 8 ohm speaker, for example will vary in impedance over the full frequency range, usually by a pretty good amount. If the speaker builder is reputable, then the rated impedance will be measured at or very near the cone resonance, and is ideally a minimum number.
Likewise your amplifier. Its rated 8 ohms is a safe minimum rating , based on presumed builder measurements, but is likely to be very safe from about 6 ohms on up.
There is no easy way to measure actual impedance ( or resistance at a specified frequency) in a home environment, so some of this remains educated guess work. However, it will not immediately "blow " your amp is you run a test with low initial volume. As you increase volume, if you hear problems too early in the runup, then you know you may have a problem. Remember, higher numbers means LESS current. Now, in a multi speaker setup, even though you have less power to each driver, you do have more conversion overall of electrical to acoustic energy going on. So , you will get more- or at least equal sound energy, assuming reasonable speaker performance, with good speaker drivers. Modern amp circuits are far more tolerant of uneven impedance loads than older technology.
Jonathan/Electric /steam Modelworks
Jonathon,
many thanks. It seems that multiple speakers require a lot of planning.