Quick Question:
If my Eltax Monitor III speakers State 4-8 Ohms on the back what impedance are they?
If my Eltax Monitor III speakers State 4-8 Ohms on the back what impedance are they?
So it means it's at least 8-Ohms then?
They've been sat on a shelf doing nothing for years; I've just pared them with a new TA2021B based T-Amp and I was wondering how they should stack up in theory. They sound supprisingly good actually.
The specs and internet myth of the TA2021B suggest it would be working at it's best into 4 Ohm and/or a hig-efficiency pair of speakers. The 89dB Monitor III are really doing the job for near-field.
They've been sat on a shelf doing nothing for years; I've just pared them with a new TA2021B based T-Amp and I was wondering how they should stack up in theory. They sound supprisingly good actually.
The specs and internet myth of the TA2021B suggest it would be working at it's best into 4 Ohm and/or a hig-efficiency pair of speakers. The 89dB Monitor III are really doing the job for near-field.
It means that the impedance varies with frequency as it does in most speakers. You should make sure that whatever amplifier you use is stable at 4 ohms.
For nearfield home use, i have never found impedance/power/sensitivity being a problem for any amp and any speaker.
If you were to look at their impedance over the audio band you would be surprised. 2 Ohms to over 2K Ohms is not uncommon.
This, in part, is why Class D amps need to be matched to the speakers, whereas Class A is much more forgiving.
This, in part, is why Class D amps need to be matched to the speakers, whereas Class A is much more forgiving.
I'd say that's a 4 ohm loudspeaker! LOL
Eltax Monitor III Bookshelf Loudspeakers | Hi-Fi
Nothing like seeing the actual impedance curve!
An externally hosted image should be here but it was not working when we last tested it.
Eltax Monitor III Bookshelf Loudspeakers | Hi-Fi
Nothing like seeing the actual impedance curve!
The impedance of the speaker doesnt change in Bridged or Parallel or Series modes.
The important thing is what is being presesnted to the amplifier.
The speaker manufacturer here is saying that these speakers will suit amps that require any load between 4 and 8 Ohms.
No idea what 4-8 Ohm means with these.
The other speakers I know which state '4-8 Ohm' were the large 215DMT & FSM Tannoys but with these the user could choose to run the extra 15" in parallel with the 15" DC or as a 3 way so it did make sense.
The other speakers I know which state '4-8 Ohm' were the large 215DMT & FSM Tannoys but with these the user could choose to run the extra 15" in parallel with the 15" DC or as a 3 way so it did make sense.
If the spec were 8 ohms, or 4ohms, noboby would ask about the meaning, though it wouldn't make more sense.
If in doubt, measure the DCR and add 25-30%. That's pretty standard.
Thanks system7 for posting the graph.
I would be tempted to call it a 6 ohm speaker.
Thanks system7 for posting the graph.
I would be tempted to call it a 6 ohm speaker.
If measured with an impedance meter I am sure it would fall between 4 ohms at low frequency to probably above 8 ohms at high frequency. Typically meaning an amplifier capable of delivering the power into a 4- 8 ohm load would be suitable to run the speaker. Usually one might see a speaker rated 8 ohms nominal for example.
In the old days from 70s through 80s to very early 90s, all speaker drivers were selected to have matching impedance.
You had the option to buy 4ohm speakers, very common in continental Europe.
Or buy 8ohms speakers, much more common in the UK.
I have no idea what the USA did back then (nor now).
All these speakers had the same problem they either gave adequate bass with poor efficiency or they gave good efficiency and much restricted bass output.
The manufacturers did have a trick up their sleeves.
They developed speakers that used a higher Q for the bass roll off, that exaggerated the second harmonic and to most buyers it sounded like extended bass.
Slowly the manufacturers realised that by combining an 8ohm treble driver with a 4ohm bass/mid driver or by combining an 8ohm treble driver with two 8ohm bass/mid drivers they could extend the bass and make their speakers appear to be more efficient.
SPL quoted as xydB/1W @ 1m was in effect an efficiency figure that many manufacturers did not want to use. It would expose them in a poor light.
Instead many would use nmdB/2.83Vac @ 1m, if they thought it make them look equal or better than their competitors.
When the 4ohm bass mid driver with the 8ohm treble driver combination came along these less scrupulous manufaturers jumped on the bandwagon.
Their speakers appeared to be more efficient than any that use a 1W value for sensitivity and better than any that used 2.83Vac into real 8ohm speakers.
To make matters worse, these unscrupulous manufacturers then hid from their customers that they had used a 4ohm driver to "cheat" their customers. "look here we have an efficient bookshelf speaker that does not need a big amplifier and we are giving you the discerning listener more than adequate bass response".
A manufacturer that quotes 4 to 8 ohms is telling the whole truth. They are not hiding anything.
But the problem you the user has is that the 4 to 8 ohms speaker operates as a 4ohm speaker over much of the audio frequency range. It is only over the top two or three octaves (out of the ten octaves we listen to ) that the speaker operates as an 8ohm speaker.
The amplifier does not need to be stable in to a 4r0 load. It needs to be capable of driving a 4ohm speaker load. That is quite an onerous task and very different from stable in to 4r0.
Any competent 8ohm capable amplifier must be stable into a 4r0 test load. Good 8ohm capable amplifiers will probably be stable into a 2r0 load and make a half hearted effort at driving a 4ohm speaker.
A 4 ohm capable amplifier must be capable of driving a 4ohm speaker and must be stable into a 2r0 test load and preferably be able to drive a 1r0 load for a short while, maybe only 10 or 20 seconds, without blowing up.
Use an ohmmeter to check the DC resistance of your speakers.
Expect a real 8ohm speaker to be greater than 5r5 and more probably greater than 6r5.
Any less than this and some where in the make up of the drivers and/or the crossover and EQ there is a lower load than 8ohms impedance.
Low impedance speakers require careful selection of the amplifier.
You had the option to buy 4ohm speakers, very common in continental Europe.
Or buy 8ohms speakers, much more common in the UK.
I have no idea what the USA did back then (nor now).
All these speakers had the same problem they either gave adequate bass with poor efficiency or they gave good efficiency and much restricted bass output.
The manufacturers did have a trick up their sleeves.
They developed speakers that used a higher Q for the bass roll off, that exaggerated the second harmonic and to most buyers it sounded like extended bass.
Slowly the manufacturers realised that by combining an 8ohm treble driver with a 4ohm bass/mid driver or by combining an 8ohm treble driver with two 8ohm bass/mid drivers they could extend the bass and make their speakers appear to be more efficient.
SPL quoted as xydB/1W @ 1m was in effect an efficiency figure that many manufacturers did not want to use. It would expose them in a poor light.
Instead many would use nmdB/2.83Vac @ 1m, if they thought it make them look equal or better than their competitors.
When the 4ohm bass mid driver with the 8ohm treble driver combination came along these less scrupulous manufaturers jumped on the bandwagon.
Their speakers appeared to be more efficient than any that use a 1W value for sensitivity and better than any that used 2.83Vac into real 8ohm speakers.
To make matters worse, these unscrupulous manufacturers then hid from their customers that they had used a 4ohm driver to "cheat" their customers. "look here we have an efficient bookshelf speaker that does not need a big amplifier and we are giving you the discerning listener more than adequate bass response".
A manufacturer that quotes 4 to 8 ohms is telling the whole truth. They are not hiding anything.
But the problem you the user has is that the 4 to 8 ohms speaker operates as a 4ohm speaker over much of the audio frequency range. It is only over the top two or three octaves (out of the ten octaves we listen to ) that the speaker operates as an 8ohm speaker.
The amplifier does not need to be stable in to a 4r0 load. It needs to be capable of driving a 4ohm speaker load. That is quite an onerous task and very different from stable in to 4r0.
Any competent 8ohm capable amplifier must be stable into a 4r0 test load. Good 8ohm capable amplifiers will probably be stable into a 2r0 load and make a half hearted effort at driving a 4ohm speaker.
A 4 ohm capable amplifier must be capable of driving a 4ohm speaker and must be stable into a 2r0 test load and preferably be able to drive a 1r0 load for a short while, maybe only 10 or 20 seconds, without blowing up.
Use an ohmmeter to check the DC resistance of your speakers.
Expect a real 8ohm speaker to be greater than 5r5 and more probably greater than 6r5.
Any less than this and some where in the make up of the drivers and/or the crossover and EQ there is a lower load than 8ohms impedance.
Low impedance speakers require careful selection of the amplifier.
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The IEC standard (IEC60268-3) allows any impedance above the rated value, but limits the impedance below. It does not allow the rated impedance to fall below the 80 % of the nominal value at any frequency.
You could get away under that rule calling this 4 ohm minimum speaker a 5 ohm speaker, calling it a 6 ohm speaker would be cheating😉.
Art
Feed the speaker from a source of 6 volts RMS via a 600 ohm series resistor. The RMS voltage as measured across the speaker terminals then equates to the impedance. So 60 millivolts would be 6 ohm, 40 millivolts 4 ohm and so on. Try it with a really slow frequency sweep 🙂
(Method above credited to Doug Self)
Nominal impedance figures quoted on speakers mean little imo. My B&W's are called "8 ohm" but dip to 2.8 ohms around 100hz.
(Method above credited to Doug Self)
Nominal impedance figures quoted on speakers mean little imo. My B&W's are called "8 ohm" but dip to 2.8 ohms around 100hz.
A lot of amplifiers will drive a 4 ohm load even though they are rated for 8 ohms. However they do not like it and possibly do not perform well. Speaker impedance falls at low frequency and if an amplifier isn't completely stable its going to go up in a puff of smoke.
The Ampzilla I had a years ago rated to drive a 4 ohm load went boom when trying to reproduce the 1812 overture with cannon blasts. To drive a 4 ohm load it had better be capable of doing it and staying together.
The Ampzilla I had a years ago rated to drive a 4 ohm load went boom when trying to reproduce the 1812 overture with cannon blasts. To drive a 4 ohm load it had better be capable of doing it and staying together.
Some speakers drop to their minimum at a low frequency, some have the minima at relatively high frequencies like Mooly’s B&W’s with a minima of 2.8 ohms at 100 Hz.
The OP’s Eltax Monitor III speakers are near four ohms at 10 Hz, 55 Hz, and 150 to 300 Hz as clearly shown in the chart in post #7.
Typical music would have far more content in the upper range ( around 55 Hz, and 150 to 300 Hz) than the lower range.
The 1812 Overture is an exception with the cannon’s VLF recorded at a much higher peak level than the musical average.
I can remember a speaker demo using the 1812 Overture ending with gross amp clipping and speaker flapping, a slight change in the pre-amp setting turned the demo from being fairly impressive for a small speaker to being laughable.
Perhaps the speakers you were using dropped well below the Ampzilla’s 4 ohm rating at VLF, and you drove the amp into hard clipping.
Some amps have protection for eventualities like what blew up your amp, some don't 😉.
Art
Even my 2A3SE has that kind of feature! Shabzilla & The pharaohms I don't know...😱
http://www.youtube.com/watch?v=MHF558u6Q_8
Happy new bangs!😀
I think you guys are overlooking the obvious and making things much too complicated:
An externally hosted image should be here but it was not working when we last tested it.
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