Speaker Impedence vs Amplifier load.

[sunder]

Hello friends, please clarify for this: Some speaker's specification is 4-8 ohms on the rear side label of the speaker. In such cases, how the connected amplifier will take the speaker's impedence on the account? as 4 ohms? or 8 ohms? or in between? Is it good for amplifiers to connect such a speakers?.
Thank you.
sunder.

 

[dovin]

I've anecdotally heard about cheaper amps being 'blown' (whatever that means) by connecting to low impedence speakers they weren't designed to handle. At least a blown fuse is possible at higher volumes, I think.

Best to check your amp documentation to ensure it can handle 4 amps.

 

[sunder]

most of the amp's are designed to handle 2ohms loads.

when you hook low impedance speakers to such amp's the power output is more, you cant turn up volume as you like as it has chances of tripping the amp.....also amp tends to get heated more of low impedance drive....

but not to worry it will not damage the equipment nor speakers.....

musicmaya, I see what do you explain. Is there any sound differences between single (4 or 8) fixed impedence and 4-8 impedence in speakers?
Thank you,
Regards,
sunder.

 

[jaudere]

musicmaya, I see what do you explain. Is there any sound differences between single (4 or 8) fixed impedence and 4-8 impedence in speakers?
Thank you,
Regards,
sunder.

Impedance of speaker when quoted, is usually nominal impedance. However the impedance of a driver/speaker is not constant. It varies as per the frequency it is playing. It depends on the individual driver characteristics and crossover characteristics.
When a speaker spec has impedance of 4-8ohms, it means that the impedance is going to vary between 4 and 8 . It cannot be constant unless you are playing a single note sound (e.g. a particular key of a piano and nothing else). For usual music, it is a mix of various frequencies and impedance is highly variable.

If impedance of speaker is highly variable, the amplifier finds it difficult to drive. Some speakers, Like Ushers, are known to have fairly constant impedance and are easier to driver for the amp.

Change of impedance does not change the frequency the speaker is playing but definitely changes the amplitude. Speaker with lower impedance , say 4 ohm, will play louder than similar speaker of 8 ohm if volume knob is kept at the same position. This is because the amplifier pushes more current for lesser impedance at the same position of volume knob.

Lower the impedance(e.g. 2 ohm), more the current the amp has to push and puts more load on amp. Higher the impedance, safer it will be for the amplifier but the amplitude(loudness) will go down.

I hope this helps a bit.

 

[sunder]

Impedance of speaker when quoted, is usually nominal impedance. However the impedance of a driver/speaker is not constant. It varies as per the frequency it is playing. It depends on the individual driver characteristics and crossover characteristics.
When a speaker spec has impedance of 4-8ohms, it means that the impedance is going to vary between 4 and 8 . It cannot be constant unless you are playing a single note sound (e.g. a particular key of a piano and nothing else). For usual music, it is a mix of various frequencies and impedance is highly variable.

If impedance of speaker is highly variable, the amplifier finds it difficult to drive. Some speakers, Like Ushers, are known to have fairly constant impedance and are easier to driver for the amp.

Change of impedance does not change the frequency the speaker is playing but definitely changes the amplitude. Speaker with lower impedance , say 4 ohm, will play louder than similar speaker of 8 ohm if volume knob is kept at the same position. This is because the amplifier pushes more current for lesser impedance at the same position of volume knob.

Lower the impedance(e.g. 2 ohm), more the current the amp has to push and puts more load on amp. Higher the impedance, safer it will be for the amplifier but the amplitude(loudness) will go down.

I hope this helps a bit.

Thanks jaudere, I understand. Some vintage amplifiers have seperate speaker terminals for 4 ohms and 8 ohms. So, which terminal is suitable for the 4-8 ohms speakers?
Thank you.
sunder.

 

[S.P.KRISHNA]

In other terms more current the speaker sucks in resulting in damage to the AMP particularly when speaker has high wattage and lower impedence to that of AMP.

Regards

 

[jaudere]

Thanks jaudere, I understand. Some vintage amplifiers have seperate speaker terminals for 4 ohms and 8 ohms. So, which terminal is suitable for the 4-8 ohms speakers?
Thank you.
sunder.

Put it on 4 ohm. Technically it will be safer. Amps capable of driving low impedance speakers have better power supply. But i dont think the said vintage amp will have 2 separate power supplies, 1 for 4 ohm and 1 for 8ohm speakers.


On my amp which was not vintage,there were 2 terminals(for 2 pairs of speakers) . I could use both together only if each speaker was 8 ohm or more . That means that the two terminals were wired in parallel inside the amp. Probably the vintage amp you speak about has similar thing.

Can you post a picture?

 

[Thad E Ginathom]

I've anecdotally heard about cheaper amps being 'blown' (whatever that means) by connecting to low impedence speakers they weren't designed to handle....

I have seen an amplifier blown by connecting multiple speakers. Its owner did not understand the difference between connecting speakers in series and connecting them in parallel, and it cost him his amp.

I don't understand it either! But it is explained, along with a lot of other information about impedance and other stuff about speakers on this page. Yet another useful link that I found on hifivision just a few days ago

 

[doors666]

most of the amp's are designed to handle 2ohms loads.

when you hook low impedance speakers to such amp's the power output is more, you cant turn up volume as you like as it has chances of tripping the amp.....also amp tends to get heated more of low impedance drive....

but not to worry it will not damage the equipment nor speakers.....

Incorrect. Most of the home theater amps will blow with a 2 ohm load. almost none of them can handle it. car audio is a different world altogether, where the system is driven from battery, which does not like high impedence loads, also the manufacturer's can push the wattage of their amps up, thats why you see 1000w amps.

I dont think the sensitivity takes a hit with higher impedence. speakers efficiency is defined at x db/1m/2.83v. For 8 ohm load, 2.83 volts translates to 1w, while for 4 ohm load, it requires around 2w.

a 4-8 ohm speaker, if its specified correctly, will be around 6 ohms nominal. a 4 ohm nominal can drop down in impedence to around 3.2ohms and an 8 ohm nominal will drop down to around 6 ohms. These will be the lowest numbers for a very small frequency range and for most of the frequencies, it will be at the nominal value specified.

 

[rishiguru]

Incorrect. Most of the home theater amps will blow with a 2 ohm load. almost none of them can handle it. car audio is a different world altogether, where the system is driven from battery, which does not like high impedence loads, also the manufacturer's can push the wattage of their amps up, thats why you see 1000w amps.

I dont think the sensitivity takes a hit with higher impedence. speakers efficiency is defined at x db/1w/2.83v. For 8 ohm load, 2.83 volts translates to 1w, while for 4 ohm load, it requires around 2w.

a 4-8 ohm speaker, if its specified correctly, will be around 6 ohms nominal. a 4 ohm nominal can drop down in impedence to around 3.2ohms and an 8 ohm nominal will drop down to around 6 ohms. These will be the lowest numbers for a very small frequency range and for most of the frequencies, it will be at the nominal value specified.

+1 from me.

Also the lower the rated nominal impedence of the speakers the more current will be drawn, and amps do not like to deliver a lot of current. Cheap amps should be used with 8 ohms speakers.

Even an INR 20K plus 8 ohms rated stereo amp mated with 6 ohms speakers can cause drastic heat build up & ultimately thermal failure in the amp.

 

[arj]

most of the amp's are designed to handle 2ohms loads.

when you hook low impedance speakers to such amp's the power output is more, you cant turn up volume as you like as it has chances of tripping the amp.....also amp tends to get heated more of low impedance drive....

but not to worry it will not damage the equipment nor speakers.....

This is a wrong understanding !. there are very very few amps which can consistently take a 2 Ohm load and very few speaker which present this load. the older Mark Levinson amps could reportedly take 1 Ohms and so do the Accuphase power amps.

even so called tough to drive speakers like dynaudio vary rarely go below 3Ohms nominal at any frequency.

jauderes post completely explain the situation..thats the reason why certain speakers lose out on Bass with some amps ie when the load gets tough , the amp is not able to supply the same amount of current and hence the SPL goes down

most amps are actually designed for optimal at 6-8 ohms although most could take a 4 ohms load as well..car audio is designed around 4Ohms I believe,

 

[Thad E Ginathom]

For the few people who, like me, don't really understand electronics... I came to get some feeling for this from the example that, if you connect a wire across your amp speaker terminals, this is a zero Ohm load :sad:

 

[saurabh459]

On a related subject ,how about mixing impendence ?,say i want 2 6ohms front speakers and rest all 8 ohms.Is denon 1611 fine to drive 6ohms?

 

[doors666]

For the few people who, like me, don't really understand electronics... I came to get some feeling for this from the example that, if you connect a wire across your amp speaker terminals, this is a zero Ohm load :sad:

yeah, thats shorting the speaker terminals. kinda like putting a wire into both the terminals of an electrical socket. sparks will fly

On a related subject ,how about mixing impendence ?,say i want 2 6ohms front speakers and rest all 8 ohms.Is denon 1611 fine to drive 6ohms?

check your manual. some of the avrs can handle it, some cant.

 

[captrajesh]

thats the reason why certain speakers lose out on Bass with some amps ie when the load gets tough , the amp is not able to supply the same amount of current and hence the SPL goes down

Thank you for this information, it sure sounds logical. That's probably the reason why my Class D amp gives out lean bass because it is drawing its current from puny looking EI trafo. I'll try my luck with an R-core trafo and see.

 

[S.P.KRISHNA]

Damping factor of the speakers should also be taken into account.

Regards

 

[Hari Iyer]

Thanks jaudere, I understand. Some vintage amplifiers have seperate speaker terminals for 4 ohms and 8 ohms. So, which terminal is suitable for the 4-8 ohms speakers?
Thank you.
sunder.

The cross-over of the speakers also have circuits (Zobel impedance) that provide constant impedance to the filter so that the cross-over point does not change. The cross-over frequency is the function of the speaker impedance and hence a constant impedance is required for the cross-over point. Another design is to look at the impedance curve of the woofer and design the filter looking at the impedance at the cross-over frequency. Also the speaker resonance plays havoc with the impedance where at the resonating frequency of the speaker the impedance is as high as 20 ohms to 30 ohms.

In the bass-reflex design there are 2 resonance peak. One of the cabinet and other of the woofer which becomes very difficult for the amplifier to handle at higher volume levels and low frequency source.

Transmission Line and Aperiodic system designs usually have a flatter neutralized impedance curve and provides constant load to the amplifier and the acoustic impedance is neutralized by the line tuning. Constant load to the amplifier at all frequencies help in better power transfer between amplifier and speaker, better frequency response and power bandwidth with increased dynamic headroom.

 

[doors666]

Thank you for this information, it sure sounds logical. That's probably the reason why my Class D amp gives out lean bass.

try to upgrade the caps on the output stage to higher values, that should make it a lot better. what speakers are u using with the class d. usually the impedence drop is in the 100-300 hz range and thats a critical zone as tons of music lives there.

 

[captrajesh]

try to upgrade the caps on the output stage to higher values, that should make it a lot better. what speakers are u using with the class d. usually the impedence drop is in the 100-300 hz range and thats a critical zone as tons of music lives there.

Hi, went out & just returned. Edited my post and realised that there were some more posts.

I had earlier paired it with Acoustic Portrait bookshelfs and realised the lean bass issue. I've revisited the amp and paired it with my new speakers, Cadence Aristas. Result is the same. However it truly excels in reproducing mids which are so beautiful and musical and even has crispy highs.

I've paired it with a variety of pre-amps viz, Parasound which I wanted to buy, NAD pre which I owned for some time and now with Acoustic Portrait PM1 Tube preamp.

As suggested by you now and earlier by Grubyhalo, I need to do some component changes viz better speced R-core transformer and bigger caps.

 

[jaudere]

I am not expert in this but aren't the caps supposed to help mainly in the transient peaks ? Will putting higher caps help in improving constant current supply? In short I thought that 'bigger the caps,more the headroom but that doesnt translate into higher RMS Power'.