Whatever the reason, the sound levels for the Sub and the main speakers would still have to be manually matched; and once that was done, this trait would have no impact on the sound from the set up compared to one without the Sub, other than the desired extension in low frequency response. Correct?
Whatever the reason, the sound levels for the Sub and the main speakers would still have to be manually matched; and once that was done, this trait would have no impact on the sound from the set up compared to one without the Sub, other than the desired extension in low frequency response. Correct?
Yes I think I agree with this. Some might want to use the main speakers full range, though, and set the sub filter within the sub controls. The only want to do this, as I understand it, is to connect to the sub with speaker level input.
The Sonos Amp output voltage should just be input signal * gain, until clipping. If you remove low frequencies the amp's output in the pass-band should not change if the crossover filter has unity gain for the pass-band.
You can prove to yourself that even a cheap amp is not affected by the presence of the low frequencies. In Audacity, import a clip with a good range of frequencies. Filter out the low end. Then listen to the filtered and unfiltered clips. The mids and highs will be played at the same level for both clips.
None of this is incorrect, but nor does it refute what I stated. The Amp's gain is under software control, and the software can raise the gain for a given volume setting when there is no requirement to produce low frequencies.
Maybe I misunderstood what you were saying then. Possibly we are both just saying that the crossover adds gain (according to Peter's measurement). You think this might be intentional, whereas I think it is likely to be unintentional.
Some might want to use the main speakers full range, though, and set the sub filter within the sub controls. The only want to do this, as I understand it, is to connect to the sub with speaker level input.
Yes. And there is someone struggling to achieve just this without a hum! See:
https://en.community.sonos.com/components-228996/sonos-amp-and-high-level-input-from-subwooder-6822917
Maybe I misunderstood what you were saying then. Possibly we are both just saying that the crossover adds gain (according to Peter's measurement). You think this might be intentional, whereas I think it is likely to be unintentional.
Correct, I think it's intentional. The Amp has more headroom for gain when not required to produce low frequencies, so the Amp's software takes advantage of this. Amplifiers with simple manual controls typically cannot be run at 100% of dial volume without distortion, so one tends to assess by ear how loud they can be run, and one can increase the maximum volume setting if low frequencies aren't required. The Amp can be run at its 100% volume setting without distortion, so it makes sense to recalibrate via software control when the gain available increases.
Correct, I think it's intentional. .
Do you mean that removing the low end is likely to result in a significantly lower peak amplitude in the output to the main speakers? I suppose that could be why they bump the gain. I'm not sure if that reasoning would hold true or not, I would think it would be dependent on what music is playing.
Do you mean that removing the low end is likely to result in a significantly lower peak amplitude in the output to the main speakers?
Yes, that's the gist of it.
Audio amplifiers are essentially linear devices. They have to amplify each frequency by the same amount independent of other frequencies. If different frequencies interact, this is called non-linear distortion and is highly undesirable. It would mean, for example, that every C# on the trumpet, or every Bb on the bass would affect other frequencies. This doesn't happen to any noticeable extent. So filtering out the low frequencies should not affect any other frequencies. And it would be extremely unlikely to uniformly boost all other frequencies by exactly the same amount, i.e. 3 dB.
My guess is that there is a bug in the DSP part of the Amp. The fact that the boost is exactly 3 dB suggests a coding error in the filtering software. It can be very easy to leave out a factor of 2. And a 3 dB boost is exactly double the power.
Like kumar and lahey, I don't know what the point would be in deliberately boosting the non-filtered frequencies by 3 dB.
Cheers, Peter.
p.s. I missed reading page 3 of this thread when posting just now. I can buy the argument that Sonos decided to use the additional headroom available when low frequencies are removed to make the Amp a bit louder. Of course, this will mean the lowest possible volume is also increased.
Of course, this will mean the lowest possible volume is also increased.
Presumably, since the Amp's gain is entirely under software control, Sonos can calibrate it however they wish for different volume settings.
Presumably, since the Amp's gain is entirely under software control, Sonos can calibrate it however they wish for different volume settings.
Agreed. They could have no boost at low volumes and larger boost at high volumes. Although, it is a bit of a coincidence that both hodgeal (in the original LS50 thread) and I found an exact 3 dB boost at whatever volume we tested (I was at 30%, I don't know about hodgeal).
Cheers, Peter.
A small snippet of information gleaned in reading about power:
3 dB is a doubling of power, but it takes 10 dB to achieve a perceived doubling of loudness.
So 3 dB changes are noticeable but not big.
I had not thought of it that way; but if it is a doubling of the power then that is a lot gained by just adding a Sub. As much as is gained by the Sonos Amp over the Connect Amp.
The Sonos Amp becomes 250 wpc into 8 ohms?!
I think it is more accurate to say that it is 125W into 8 ohms for a reduced range of frequencies compared to the normal 20-20k measurement. Frequencies below 80Hz (or whatever the crossover is set at) are excluded from the power rating. The power supply doesn't magically get any beefier. A good fraction of an amp's power is used driving low frequencies.
Cheers, Peter.
p.s. The Amp plus powered sub combo might now be 250W.
I think it is more accurate to say that it is 125W into 8 ohms for a reduced range of frequencies compared to the normal 20-20k measurement.
p.s. The Amp plus powered sub combo might now be 250W.
Why is it wrong to say it is 250W into 8 ohms for a 80-20k measurement? Isn't that what the p.s. also conveys, if the Sub delivers 250 wpc from 20 to 80 hz, that the combination is 250 wpc from 20-20k?
There is a better set of questions to ask:
Suppose the same Sub was to be attached to the Sub out of a traditional HiFi stereo amp of the same power spec of the Sonos amp, 125 wpc into 8 ohms across 20-20k.
1. Would that combo now be 250 wpc also?
2. The 3dB boost seen here, isn't typical for such amps, as far as I know. So how does this ability to drive the 80-20k to higher sound levels than before achieved? And if it never gets achieved, with unused headroom even with amp volume at 100%, does it mean that the combo is NOT 250 wpc, but 125 wpc as it was minus the Sub?
Also, a question of the Sonos Amp for confirmation: If music content minus frequencies below 80hz is played, will it sound noticeably louder every time the Sub is toggled on in the app with no other change in how the music sounds?
Why is it wrong to say it is 250W into 8 ohms for a 80-20k measurement?
Given an 8 ohm impedance, I think the Amp can only put out 125W - this would be determined by the design of the amp, in particular its ability to push current through an 8 ohm load. If that power (ability to push current) is spread over 20-20k, you get a certain sound level. If that power is limited to 80-20k, then frequencies above 80 Hz can have a 3dB increased sound level (i.e. more current), but the total power is still 125W. The power saved from not having to reproduce the low frequencies is now able to be utilised for frequencies above 80 Hz. But the total available power is fixed at 125W by design.
Cheers, Peter.
Also, a question of the Sonos Amp for confirmation: If music content minus frequencies below 80hz is played, will it sound noticeably louder every time the Sub is toggled on in the app with no other change in how the music sounds?
I think this is correct. It is demonstrated by the measurements hodgeal and I made.
Does this then bring to light an undisclosed feature of the Amp? That it will deliver sound levels that are higher across the board by 20-30% if bonded with the Sonos Sub or with a third party Sub of similar power? That is no trivial feature to have. And I don't think that too many legacy HiFi amps can boast of this capability; all they can claim is what comes from the Sub - frequency extension at the lower end.
Which lead me too: this feature would be even more welcome in the Connect Amp, which is just 55 wpc, and could better use a boost in overall sound levels. I am pretty sure it isn't implemented there, from memory; my Sub is with the play 1 these days. I see no reason why it can't be implemented there, other than the usual prioritisation constraints. And of course, the fact that it is a superseded product.
This is interesting, so I imported some music into audacity to see how much headroom is created by high-pass filtering. I'm finding that it isn't much, only a few tenths of a dB typical even with a 100hz filter. So I am not convinced that there is good reason for the 3dB bump that Sonos uses with the crossover. Try it yourself; here is how to find the peak level in audacity:
http://think3x.com/audio/2014/09/02/audacity-effects-amplify-5-finding-peak-amplitude/
But isn't this before the volume control has been recalibrated as Sonos has apparently done - I suppose your finding above is with some other amp?
But isn't this before the volume control has been recalibrated as Sonos has apparently done - I suppose your finding above is with some other amp?
What I was doing with audacity was just filtering a music file, nothing really specific to the amp. I was just trying to see if high-pass filtering creates enough headroom to justify bumping gain with a sub crossover. I'd be interested to see what others find.
