Understanding Ohms against Watts??

Witterings

Active Member
If I'm comparing 2 systems for overall power / volume / performance .... one is 2 x 30 watts @ 6 ohms and the other 2 x 60 Watts @ 4 ohms what differences should I expect.

The speakers in case it's needed are 8 ohms although I'm interested in generally understanding it and what differences there might be with 4 ohm speakers.
 

mseve1

Active Member
If I'm comparing 2 systems for overall power / volume / performance .... one is 2 x 30 watts @ 6 ohms and the other 2 x 60 Watts @ 4 ohms what differences should I expect.
It's impossible to say what to expect based purely on these parameters. Relative system performance depends upon far more than just quoted amplifier output power.

The speakers in case it's needed are 8 ohms although I'm interested in generally understanding it and what differences there might be with 4 ohm speakers.
Speaker impedance ratings are nominal values and don't have much relevance apart from highlighting how easy they are to drive/control. It's more useful to consider their efficiency (output Sound Pressure Level per Watt input) to determine their relative output volume or loudness for a given input.
 

acgingersnaps

Active Member
As above, but i would ask, have you got sensitive speakers? Those figures suggest pretty lightweight power output at 8 ohms.
 

Witterings

Active Member
As above, but i would ask, have you got sensitive speakers? Those figures suggest pretty lightweight power output at 8 ohms.
Thanks for both the replies .. in answer to this query I wouldn't know what to look for to know if a speaker was sensitive or not.
The combination is a Denon RCD - M39 and Monitor Audio Bronze BX1's. ... I'm possibly looking for something with a little more power (ideally without changing speakers as well) as it's in a reasonable size kitchen / living area and was looking at the Denon CEOL RCD-N10 but if I'm not going to notice much difference there's no point in changing.
 

mseve1

Active Member
Both units have output specs which are rather misleading. However, once you adjust the quoted figures for the same load and distortion levels then the CEOL N10 looks to be around twice as powerful as the M39. As such, you should expect a worthwhile increase in volume capability with the N10 but you would be losing the DAB radio of the M39.

The MA BX1s are pretty efficient at 88dB/W/m so no need to change them.
 

Witterings

Active Member
Both units have output specs which are rather misleading. However, once you adjust the quoted figures for the same load and distortion levels then the CEOL N10 looks to be around twice as powerful as the M39. As such, you should expect a worthwhile increase in volume capability with the N10 but you would be losing the DAB radio of the M39.

The MA BX1s are pretty efficient at 88dB/W/m so no need to change them.
Brilliant and thank you for that!!!

What exactly do you want to achieve, more volume?
More volume / a fuller sound if possible although I realise the speakers will play as large a part of that (might change them at a later date) but it also has a bluetooth built in ...
At the moment I have chromecast audio in the Opt input and then a splitter for a BT receiver and an Amazon Echo Input which isn't ideal.
We also have a rubbish system in the bedroom which is only used for radio so would probably move the M39 into there.
 

RBZ5416

Distinguished Member
I think I'd start with speakers. The small driver & 55Hz bottom end of the BX1 isn't helping & I doubt more power is going to help that much, not that the N10 has significantly more power. Although as @mseve1 suggests, getting meaningful specs for these mini systems isn't easy.

So my starting point would be a more efficient speaker with a larger woofer & lower bottom end. If you otherwise like the BX1 then a used pair of BX2 would tick all those boxes for around £100. I'd suggest that for sound only, the N10 will give you very little over the M39.
 

larkone

Distinguished Member
Or a small sub like BK Gemini - it would extend the bottom end and take the bass load off the main speakers. I have run both of those systems with Dali Zensor 1s and a sub and it was the sub that really made the difference to the overall sound.
 

dogfonos

Well-known Member
Agree with above. Small speakers played in a large room will always sound wimpy - no matter what volume they're played at. For an accurate tonal balance with decent impact, the speaker needs to be a good size match for the listening space, roughly speaking. But if we're talking only about maximum volume...

The three main parameters that affect maximum volume available from a system are:

amplifier power output
speaker sensitivity/efficiency
speaker power handling

As far as maximum system volume goes, the higher these figures the better.

one is 2 x 30 watts @ 6 ohms and the other 2 x 60 Watts @ 4 ohms what differences should I expect.
Quick answer: IMO, not a lot - but an individuals interpretation of volume is subjective. Check this out.


These are generalisations.

Amplifier power output:
Most transistor amps manage to output more power into lower impedance speakers - but only up to a point. When a speakers impedance/resistance drops to a really low value, many amps struggle and, typically, either start to loose power or overheat or blow a fuse. Most amps don't like it when a speaker's impedance is below about 3 Ohms (although some amps are OK - depends on the amp design).

If the two amps you mention specified power output figures (Watts) into the same speaker impedance (Ohms) then you could compare them directly and determine which amp would output most power - but you can't because the speaker impedances stated are dissimilar (i.e. one is into 6 Ohms and the other into 4 Ohms). Best guess is that the 2 x 60 Watt into 4 Ohm amp would output about 2 x 45 -50 Watts into a 6 Ohm load. This is a guesstimate based on past experience and depends on certain amp design factors of which I'm unaware.

So we have two amps. Into a 6 Ohm load, one amp outputs 2 x 30 W and the other probably 45 -50 W. That's equivalent to a volume increase of about 2 dB. Doubling amp power into the same speaker gives a volume increase of about 3 dB which would give a noticeable, though far from large, volume increase - all other things being equal. Note: there are exceptions, which again depends on amp design.

Speaker sensitivity:
The Monitor Audio BX1 speaker allegedly has a sensitivity of 88dB @ 1W @ 1metre. I say 'allegedly' because speaker manufacturers often overstate specifications of their speakers, particularly it seems wrt sensitivity. But let's take the Monitor Audio figures at face value. The BX1 is an 8 Ohm impedance speaker, allegedly, and has a power handling of 70 W RMS max. Perceived volume is measured in decibels (dB). Using these figures, we can calculate the maximum volume this amp + speaker combination should achieve. The speakers give 88 dB sound output for 1 W input. Every doubling of power input increases the speaker's volume by 3 dB (approx.) which translates to 91 dB for 2W, 94 dB for 4W, 97 dB for 8W and so on. If the amp you currently have outputs 2 x 30W into 6 Ohms, I estimate that would be approx. 2 x 25W into 8 Ohms (i.e. the MA BX1 impedance). An amp of 25W equates to approx. 102 dB of sound output from the BX1. On it's own, this figure isn't particularly useful but it can be used for comparisons. Take the next Monitor Audio speaker in the BX range, the BX2. This has a sensitivity of 90 dB, is also an 8 Ohm speaker and has power handling of 100W so can output a max. of approx. 104 dB with the same 25 W input. The difference in maximum sound output of the BX1 and BX2 speakers being driven by the 25W amp is (104 dB - 102 dB =) 2 dB, which is about the same volume difference you can expect between the two amps when driving the same speaker. i.e. not huge.

If you want significant volume increase, a more powerful amp (maybe around 60 - 80W RMS/channel into 8 Ohms) will be required or purchase more sensitive/efficient speakers. Or both.
 

acgingersnaps

Active Member
Is the CD player a deal breaker? There are better options if nor.
 

Witterings

Active Member
@dogfonos ... didn't want to quote it all as it was quite long but thank you for that and much appreciated !!!!!

Is the CD player a deal breaker? There are better options if nor.
No absolutely not .... in fact the only thing it ever gets used for is The Mrs playing Michael F**&&^g Buble at Xmas so to lose it would be a massive bonus :D:laugh::rotfl:

If you have other suggestions I'd really appreciate, the only thing is size is quite important keeping it on the smaller side, I'd even looked at the mini units like the Sabaj A3 / A4 (one of the few that has the BT / Inputs I'd like) but figured these are probably going to be quite a drop in sound quality.
 

mseve1

Active Member
On reflection something seems very wrong with the manufacturer's specs of the two mini systems. Here are Denon's own figures which I assume are steady state :-

M39. 2 x 30W (1kHz into 6ohm @10% THD)
N10. 2 x 65W (1kHz into 4 ohm @0.7% THD)

If we take these figures at face value (and taking account of the different loads/distortion) then it appears that the N10 is at least 50% more powerful than the M39. However, if we look at the power consumption ratings of the two units the M39 is rated at 70W whilst the N10 is rated at only 55W!

This being the case I think it's probably unwise to draw any conclusions from a comparison of the output power specs of the two units :(
 

dannnielll

Well-known Member
Lets get back to the physics.. any amplifier outputs a voltage, this voltage drives current through a speaker ,and the product of voltage x current drives electrical power in the speaker coil . The size of the current obeys ohms law .. I=V/R . The efficiency of converting this into sound is independent of the amplifier and is the efficiency of the speaker. Equal voltages into the same speaker from different amplifiers makes the same sound level.
The data for the M39 at 30W into 6ohm means that the maximum voltage out is .13.4v.. And the current is..2.25amp.. Note 10% distortion means the unit is at the utter limits of what it can deliver
The data for the N 10 at 65watts into 4ohms means the maximum voltage out is 16.1..V . And the current is 4.03amps... Note 0.7% distortion is low , and the amplifier should be capable of at least 10% more power its distortion rises ,to unacceptable levels so lets say 16.5v and 4.5amps
If both amplifier s are driving an 8 ohm speaker ..the results are suprising. The M39 gets to drive a current of 1.65amps ... And generate an electric power of 22.45watts.
And the altogether more capable N10 gets to drive a current of 2amps and generate 32watts.
It might even be closer than that, as the M39 was running very close to its limits and heavily loaded might be able to output more voltage if it not required to drive as much current. The Thd figure for the N10 shows it was nowhere need its limits ,so that is is effortless output voltage, without loading
 

rccarguy

Active Member
A typical, good quality amplifier would have the following approximate figures depending on the speaker load, a perfect amplifier, with large power supply.

100w into 8ohm, two channels driven. 0.05%thd
150w into 6ohm, two channels driven. 0.05%thd
200w into 4ohm, two channels driven. 0.05%thd

Most budget amplifiers will struggle to drive 4 ohm speakers, they overheat, power goes down, distortion goes up, and could shut down.

A good amp will increase power as impedance drops
 

rccarguy

Active Member
The N10 cannot possibly generate anything like 2 x 65W under steady state conditions when it's only drawing 55W from the mains supply!

Yup that's why show disgust at the Yamaha 11 channel amplifier..600w maximum power consumption, and 20,000uf total capacity for ALL channels. A good two channel power amplifier will have 600w psu for just two channels and 10-20,000uf per channel!!!! My amp has 30,000uf per channel
 

acgingersnaps

Active Member
@dogfonos ... didn't want to quote it all as it was quite long but thank you for that and much appreciated !!!!!



No absolutely not .... in fact the only thing it ever gets used for is The Mrs playing Michael F**&&^g Buble at Xmas so to lose it would be a massive bonus :D:laugh::rotfl:

If you have other suggestions I'd really appreciate, the only thing is size is quite important keeping it on the smaller side, I'd even looked at the mini units like the Sabaj A3 / A4 (one of the few that has the BT / Inputs I'd like) but figured these are probably going to be quite a drop in sound quality.
Ha! What functions are actually required then?
 

Witterings

Active Member
Or a small sub like BK Gemini - it would extend the bottom end and take the bass load off the main speakers. I have run both of those systems with Dali Zensor 1s and a sub and it was the sub that really made the difference to the overall sound.
Kind of overlooked this when I skimmed replies earlier ... this may actually be something I should try!!

Question .... if I add a Sub does the system recognise that and change the crossover's so that most of the bass goes through the sub freeing up the speaker for better use of the mids / tops or does it just enhance the bass???

Ha! What functions are actually required then?
Depends if it has bluetooth built in or not .... in not then ideally 2 x Opt input and one analogue ..... if it does have BT I can lose one optical input.
Tuner would be a nice to have but again with an Alexa going through the system can always use that for radio even if it the quality is slightly less.
 

rccarguy

Active Member
Correct adding a sub frees burden on your amp, my speakers are low impedance low down about 2 ohm


However if you have a powerful amp, then the burden isn't so great, so for 2ch music it's fine running in two channel, speakers with no bass management set to full range. Wouldn't watch movies like that, but for cd audio it's fine
 

dannnielll

Well-known Member
The N10 cannot possibly generate anything like 2 x 65W under steady state conditions when it's only drawing 55W from the mains supply!
I was not looking at the product specifications..just the quoted numbers in the previous postings. The actual power consumed by amplifiers is the most dishonest of their measurements. The figure should be RMS power into resistance loads for 1hour .. in which case that N10 would probably be 20 watts per channel.
Incidentally I do have an AVR which will drive all its 7 channels at full power of 55watts RMS , or 2 at 70 until the cows come home. The power supply in it is rated at 850watts.
 
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dannnielll

Well-known Member
Yup that's why show disgust at the Yamaha 11 channel amplifier..600w maximum power consumption, and 20,000uf total capacity for ALL channels. A good two channel power amplifier will have 600w psu for just two channels and 10-20,000uf per channel!!!! My amp has 30,000uf per channel
There are a number of caveats here.
1.if the amplifiers are digital or some version of classD then they can be 90+% efficient
2.if the device has a switch mode supply it can easily get by with a fraction of that capacitance,as the DC voltage is stored at 320volts.
 

dogfonos

Well-known Member
Manufacturers have been quoting deliberately misleading, and sometimes downright dishonest, specs for decades. Here are my revised specs for the Denon equipment:

M39. 2 x 500W (1kHz into 0ohm @2000% THD)
N10. 2 x 1000W (1kHz into 0ohm @2000% THD)

...available for about 1 millisecond - accompanied by a loud bang and acrid smoke.

Specs for amp power output, speaker low frequency limit and speaker sensitivity seem to be the most unreliable.
 

rccarguy

Active Member
There are a number of caveats here.
1.if the amplifiers are digital or some version of classD then they can be 90+% efficient
2.if the device has a switch mode supply it can easily get by with a fraction of that capacitance,as the DC voltage is stored at 320volts.
Talking of usual class ab amps,not class d
 

dannnielll

Well-known Member
Manufacturers have been quoting deliberately misleading, and sometimes downright dishonest, specs for decades. Here are my revised specs for the Denon equipment:

M39. 2 x 500W (1kHz into 0ohm @2000% THD)
N10. 2 x 1000W (1kHz into 0ohm @2000% THD)

...available for about 1 millisecond - accompanied by a loud bang and acrid smoke.

Specs for amp power output, speaker low frequency limit and speaker sensitivity seem to be the most unreliable.
Good try, but you cannot develop power into a zero load...its that pesky division by zero thing or multiply by zero.
 

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