Is there any way to impedance match 4ohm speakers with 6+ohm amplifier?

N

Nigie

New member
I have a pioneer amp with 6-16 0hm speaker impedance written on the back. I would like to buy a pair of Alesis monitor 1 Mk2 speakers for it but these are rated at 4 ohms.

Is there any way of impedance matching this amp to these speakers or will I have to forget the idea and get different speakers or use a different amp/buy powered speakers do you think?

Thankyou indeed,

Nigel
 
No idea if you can match them in a way. Just don't connect them like this, or you will burn your amp.

The way it all works: trrrrrrrrrrrrrrrrrrrrrrrrrrr....

Ohm's law! U= I * R

Your amp gets a value on its input, and puts the amplified version of this signal on its output. So it will try to get a certain voltage (U) on the output, and will provide the necessary current (I) to get it there.
With a 6 Ohm speaker, that would be: I = U/R = U/6
Now, with a 4 Ohm speaker that would be: I = U/R = U/4

So for smaller values of R, the amp needs to give more current. Here, for 4 Ohm speakers, you would need 1.5 (6/4) times the max current that your amp can deliver. (max current is for 6 Ohm speakers!) The amp will try to do that, try to drive more current than it can handle, heat up because of that, and burn itself to death. How sad. I must go find a hanky now... :(
 
Thankyou for your wise and very sensitive reply, Roel. Yes, I too would hate to see my brave little amp go out in that way!
 
Nigie,
I suggest you look at the Tannoy Reveals (passive) if you want to use your existing amp. They are rated at 50watt average/100watt max, nominal impedance is 6 ohm. Personally I think you would find they are an overall better monitor than the Alesis, and not much more expensive. I have them running off an Alesis RA-150 amp.

Peace.......ChrisO :cool:
 
How about placing a 2 ohm resistor in series with the positive speaker lead to protect your shitty amp?

Nothing wrong with 4 ohm speakers. Event 20/20s are 4 ohm.
Most consumer amps cringe at anything below 8 ohms, with your
Pioneer stretching that to 6. I use a very cheapo consumer amp (SONY) and it hasn't melted yet with the 4 ohm load. I think my eardrums would explode or my neighbors would summon the police before the amp melted down....
 
The 20/20's are 4 ohm? i've just never been a fan of low impedances simply because it's not the standard. (compatibility and what not)

You'd need a big resistor to go with that, most resistors are rated at 2 watts max unless you buy a power resistor.
Sony's may be cheap, but they are stable aren't they? gotta love that!
 
The 4 ohm speakers should be fine to hook up. There's probably going to be some resistance in the wire itself which will get you close to 5 ohms. Unless your running the amp at clip and driving the piss out of the speakers, you won't have any problems. If that was the case, you'd blow up even 8 or 16 ohm monitors. Use your head and ears, and you'll be fine. While I'm not advocating overloading amplifier outputs with too many speakers or too much load (for instance a 2 ohm load on an 8 ohm rated output), this slight difference should not harm the amp. I'm an audio tech of 20 years. I say this not to brag, but only to add some credence to this statement.
 
a couple of things need to be cleared up...i'm sorry but there's a lot of misinformation here :)

V = I * R is for DC. we're talking Impedance here. the OHM rating of a speaker is nominal and is what a DC ohm meter measures. it's not what the AMP see's. the load an AMP see's is related to frequency. meaning that the AMP does not see a constant load. V = I * R does not work here. frequency must be considered. Impeadance.

if you have cables with 1ohm resistance, you've got terrible cables. unless you're running really long cables, this is of no concern. anyways, its the capacitance of the cable thats of concern.

don't place a 2ohm resistor in series with the speaker. first, this would dissipate about 1/2 your power. if you're delivering 100Ws (Based on frequency), then you're going to need a 50W resistor. that's a big resistor. and it'll get hot. secondly, speaker are inductive loads, and a resistor can cause significant phase shifts. your speakers already have a generous supply. forget this.

secondly, you can't necessarilly tell by listening when your amps overloaded. the problem here is that the output transistor heat sinks will not be able to dissipate the heat if you drive the amp too hard too long and the output transistors will fail from over-temperature.

there's nothing magic below 6ohms. the manufacturer rates the amp from 6 to 16. it won'y hurt the amp to drive a 4 ohm speaker as long as you don't drive it too hard too long. if you consistently need a Volume above 5 as your normal setting, then get another amp or other speakers. if you generally run it below 5, then you'll probably be OK. one thing though, THD generally increases as the load decreases.

-kp- :)
 
>if you're delivering 100Ws (Based on frequency), then you're going to need a 50W resistor.

If you're delivering 100W a side to a pair of Event 20/20s then you're monitoring far louder than you should to avoid fatigue and hearing damage.
 
phase shifting is the problem though.
Sonixx is right, AC circuits behave much differently than DC.

Instead of having resistance, current, and voltage on the same plane like in DC, everything in AC has a vector, and with vectors come degrees (or radians) of phase shift.
Unfortunately, I am just starting AC theory in college and I can't comment on much more than that.
 
Sonixx said:
a couple of things need to be cleared up...i'm sorry but there's a lot of misinformation here :)

V = I * R is for DC. we're talking Impedance here. the OHM rating of a speaker is nominal and is what a DC ohm meter measures. it's not what the AMP see's. the load an AMP see's is related to frequency. meaning that the AMP does not see a constant load. V = I * R does not work here. frequency must be considered. Impeadance.
Click to expand...

I know... :rolleyes:

But as far as I remember, v(t)=i(t)*Z (right? It's been a while...), so for every moment in time, this can be seen as V = I * Z. The phase of the signal doesn't really matter if we're speaking about the load on the amp. (soundwise it does, ofcourse.)
I just gave a simplified version of the explanation, to make it all seem logical and not confuse people without any electronics education.
 
Thankyou ALL so very much. I just had a very busy couple of days with not much sleep and when I checked in to all your replies tonight I was astounded!! Thankyou very much indeed for all your time.

Yes I will give consideration to TANNOYS now and also I've been reading druling reports of Mackies when one can afford them (I think they are priced individually so you can buy them one at a time). Anyway the monitor discussion is in full fling on other threads but thankyou for this specific input to my particular situation! It will be a couple of months before I can get to Melbourne where I hoped to hear some different monitors in action (I live on the Island of Tasmania). I was thinking I may just order some Alesis monitor 1's now rather than waiting as I like the idea that they are reasonably bassy for a cheaper speaker and seem very popular here in Ostralia!!

Thanks for the advice on the RESISTOR approach. I had been wondering if that would work but it seems not a very tidy solution. Also DI BOXES lower the impedence of intruments going into low impedence mic inputs from what I gather and I was wondering if people use something similar to match amp and speaker impedances?? Do you see the way a mind with little knowledge fumbles about???

I didn't quite get the bit about THD INCREASING WITH DECREASING LOAD SONIXX. I know THD is an unnice form of distortion. Is decreasing load when you decrease the volume ie. number of watts going into the speakers or is it more to do with the speakers' impedence and the "strength" with which they draw current? Or both??? Or neither!!!!!!!??

Thankyou all again very kindly.

Nigel

PS Yes my pioneer amp is humble and small and not very speci and will someday be replaced my something the hard economics of soundrecording rationalism demands but I do love it. I bought it at a market stall for AUS$7 ie US$3.50 and the following week went back to tell the lady I wanted to pay her more for it but her stall had gone. Does that story make you want to get your hanky Roel? I go through a whole toilet roll telling that one.
 
Dear Roel, I hope I haven't made you tooo sad with that story, though I do admit it is very very sad. But anyway, that's why we play music isn't it?
 
Yes. And playing music only causes more pain and makes me even sad-er.

:(

See what you did!
Now I need a hanky and a girlfriend!!! :(
 
Apart from problems with overheating the amp I was concerned with actual sound quality. I know the pioneer amp and the Alesis/Tannoy speakers may be lower end technology but I had heard you can at least maximise equipment's performance by paying attention to impedance matching. Not sure if this was in some way what you were trying to get thru to me Sonixx - ie trying to keep the amp happy at low volumes = THD??

Sorry I will try to be more tactful in future, Roel and will certainly not send you a CD of my music as that would probably be the end of you and I could never live with myself.
 
drstawl said:
If you're delivering 100W a side to a pair of Event 20/20s then you're monitoring far louder than you should to avoid fatigue and hearing damage.
Click to expand...
that's not the point. the first point is that the resistor will suck up about 1/2 (more or less depending on the load at that frequency) the power. the second point is that you'll need a really big resistor and it's going to get really hot.

Originally posted by Nigie
I didn't quite get the bit about THD INCREASING WITH DECREASING LOAD SONIXX. I know THD is an unnice form of distortion. Is decreasing load when you decrease the volume ie. number of watts going into the speakers or is it more to do with the speakers' impedence and the "strength" with which they draw current? Or both??? Or neither!!!!!!!??
Click to expand...
check your amp specs. you'll find the THD changes based on load. although your amp's spec may not list it down to four (4) or two (2) ohms. also THD may pivit around some prefered load.

THD is the amount of AMP generated extra frequencies. the lower the THD the better. lets say that you are amping two frequencies: 100Hz and 200Hz. with a perfect Amp and no THD you'll get out 100Hz and 200Hz. with a real Amp and THD you'll get 100Hz and 200Hz but some additional frequencies. this is a 'less is better' condition. the measure of these extra frequencies is a measure of THD.

Originally posted by Roel
I just gave a simplified version of the explanation, to make it all seem logical and not confuse people without any electronics education.
Click to expand...
i agree simplified is better. but i feel accuracy is more important even at the expense of some simplicity. :)
 
>that's not the point. the first point is that the resistor will suck up about 1/2 (more or less depending on the load at that

SHEESH! The resistor suggestion was a snide remark. Why would anyone buy decent speaker wire of the shortest length for the job and then introduce a resistance that simulates a ridiculous cable run? Go Back to the Newbies Forum, dude! :)

My main point was not to worry too much about the 4 ohms. If my SONY can handle it- so can that Pioneer. (My previous amp was a Pioneer). They're both fairly crappy. Getting better monitors will always be a plus. And you can always get a decent amp down the road, like I've said I someday would.

But always monitor at a reasonable level. Fatigue will make your mixing decisions worthless and hearing damage is permanent.
 
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drstawl said:
SHEESH! The resistor suggestion was a snide remark. Why would anyone buy decent speaker wire of the shortest length for the job and then introduce a resistance that simulates a ridiculous cable run?
Click to expand...
sorry if i mistook your suggestion. it didn't seem as sarcastic as you make it out to be. anyways, why do you care to be snide when someones asking for help DUDE!!! :cool:
 
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