Technical Amp Question

laissez-faire · 27 Apr 2007 at 08:40

On the back of the Marantz Amp is written:

Set 1: 4-16 ohms
Set 2: 4-16 ohms
Set 1+2: 8-16ohms

Does this mean that if connecting two speakers both speakers must be at least 8 ohms (to be within the 8-16 bracket) or that the sum of the impedance should not exceed 16ohms? Isn't impedance the inverse of the resistance?

Also, despite what is written on the back of the amp the manual still says 'speakers should have an impedance between 8 and 16 ohms, otherwise the protection circuitry may be activated during playback'. I have 6 ohm speakers, will this cause problems?

daz · 27 Apr 2007 at 10:16

It sounds like the amp can run two sets of speakers simultaneously (i.e. 4 speakers in total). If you did this, but decided to use 4 x 4 Ohm speakers, each channel on the amp would see a 2 Ohm load, which is probably dangerously low for amp (the amplifier's power supply will try to draw too much current at higher volumes and can overheat).

If you're just running two speakers, 6 Ohms is fine... it's also important to remember that speakers' impedance across the frequency range is not constant. An "8 Ohm" speaker's impedance may drop to 4 Ohms or lower for the very low frequencies.

Ste · 27 Apr 2007 at 10:49

It just means if you plan to run two sets of speakers (1+2) they must be 8ohms a pair minimum, so two 6ohm stereo sets would be too much.

If you are running one pair (output 1 or 2) you can run as low as 4, so 6ohms is no problem at all.

If the amp has protection circuitry then it doesn't really matter either way, if it cuts out the load is too high, if it doesn't then all is well =)

laissez-faire · 27 Apr 2007 at 14:07

http://www.marantz.com/pdfs/e_pm4001_man.pdf

Thinking of giving this as a gift along with some old 6 ohm speakers of mine, so want to be sure it will work. Why do you think they have written what they have on page 3 of the manual (page 8/15 of the PDF)?

daz · 27 Apr 2007 at 14:10

I would imagine it's just the difference between the technical specfications and the "recommended" impedances to be used...

Ladforce · 27 Apr 2007 at 16:14

If the load is only a resistive one, impedance = resistance ( in this case nominal is usually the one stated) and like someone said earlier this will change depending on the frequency. A speaker can be treated as a resistive system. The impedance only gets complicated which considering capacitive or inductive loads as then the impedance becomes complex.

In answer to your question, the amp is able to run speakers down to 4 Ohms when only running one set of channels but a minimum of 8 Ohms when running two sets consecutively. This is because a lower impedance speaker will draw more current and over load the amp. Therefore 8 Ohms is the minimum to prevent overloading of the amp when driving 2 sets of channels instead of 1 set. 6 Ohm speakers should be fine as long as the amp is not run at very high power, they just dont want you wiring up something like a 2 Ohm set as this would draw significantly too much current for the transformer and other components to handle.

Hope this helps.

~>Dg<~ · 27 Apr 2007 at 20:37

ah man i love this one my bro been running a modded speaker set up(speaker in every room of house running of and old record deck from the 70s) that in theory shouldnt work(should blow up

) he even told a so called hifi expert at a very high standard place about what hed done and he wouldnt have it in end he even invited him to come and look at it to prove him wrong that was about 15yrs ago haha(still running and sounds awesome).some things are recommened as just caution but theres always ways round things.

DRZ · 27 Apr 2007 at 22:07

dgmug said:
ah man i love this one my bro been running a modded speaker set up(speaker in every room of house running of and old record deck from the 70s) that in theory shouldnt work(should blow up ) he even told a so called hifi expert at a very high standard place about what hed done and he wouldnt have it in end he even invited him to come and look at it to prove him wrong that was about 15yrs ago haha(still running and sounds awesome).some things are recommened as just caution but theres always ways round things.

Of course there is - it entirely depends on the amplifier. Of course, what we have here is some consumer-grade equipment with published specifications and an OP that wants to remain within those specifications. Its not a crazy setup and there is no need to modify anything to find a way around.

On a slightly different note, I hear that music sounds loads better when you correctly punctuate your sentences.

~>Dg<~ · 28 Apr 2007 at 11:17

fingers got the better of me as usual.

james.miller · 28 Apr 2007 at 17:30

the reason the minimal load increases to 8ohm per set with two sets of speakers is because they are run in parallel. ie: 1 set of 4ohm speakers = 4ohm load. 2 sets of 4 ohm speakers = 2ohm load (run in parallel, the total impedance halfs). obviously a 2ohm load is below their recommended minimum so with two sets of speakers, they tell you to go with 8ohm minimum.

get it? lol