How much input voltage does a power amplifier need?

kenshingintoki

Distinguished Member
So if you are saying everything is fine with 1/4 the required input power, then of course you care little about the lost signal to noise, the increased distortion, etc. along with less the stellar output. Best try it all over again with a full signal and see what happens. Hopefully you do not apply this principle to everything else in your life.

By full signal, you mean you're aksing him to not have a crossover and let his atmos speakers deal with the bass?
Why would he do that? It makes far more sense to crossover the atmos channels at a pretty high frequency.

I think if most people do REW sweeps and pack dual subs calibrated, they'll be surprised how high their crossover should be. the higher the crossover, less demands on the speaker = less need for power.
 

kenshingintoki

Distinguished Member
Set your S8 mains to no lower than small 40hz. Ideally small 50hz.
C3 to small 50hz
ADP to small 90hz


These are arbitrary numbers mate.

I wish there'd be a bigger emphasis on people just measuring their own speakers in their room than these random home AV rules of crossovers which are just very very approximate. Its only takes a laptop and microphone to see.

In reality they will probably be much higher for a lot of people. I've had three rooms and all really required higher crossovers. Once you have calibrated subs integrated well and multiples, you can really bump that crossover up even higher.
 

kenshingintoki

Distinguished Member
Mr Wolf, how do you think an Arcam AVR390 will handle powering 2x 1723S Arendal surrounds and 2x Arendal 1961s channels as atmos channels?

I really can't be bothered to buy a new power amp at the moment as I have about 20 other things I want to buy, and wondering if the AVR390 will run out of juice and struggle with them?
Of course I'll do it if I have to..!

They struggled when I ran 7 channels off them in select scenes (most demanding ones so Bad Boys for Life reference IMAX intro cars zooming & batman dark knight car chase scene when I'm sure the SPL is borderline illegal lol).
 

Mr Wolf

Well-known Member
the higher the crossover, less demands on the speaker = less need for power.
I think the "sub handles the heavy lifting" subject is actually a little misunderstood. While running a higher crossover reduces the number of transient peaks in the speaker channels, it doesn't stop the speakers from having to reproduce full 20dB peaks. So it's more of a reduction in duty cycle on the amp/speakers, it doesn't mean they can be less capable SPL wise. The problem with going much over 80Hz is that the bass in some male voices can start to come out of the subs but if you need to reduce nulls then so be it. Personally I wouldn't want to go any higher than 100Hz though and would always run 80Hz if my room allowed it.

Mr Wolf, how do you think an Arcam AVR390 will handle powering 2x 1723S Arendal surrounds and 2x Arendal 1961s channels as atmos channels?
Normally I'd say no problem at all because Atmos channels only have max 14dB peaks (vs 20dB on LCRs and 17dB in bed surrounds) but those Arendals aren't the most efficient speakers out there plus, if I recall correctly, you listen pretty loudly in a fairly large room. That Arcam hasn't got the beefiest amp section either, I know many are simply bought and used as 11.1 processors.

I have the Arendal speaker specs to hand but if you want to give me their MLP distances, your room size and listening level I can run a few numbers for you. It also matters hugely how on-axis they are to the listener as all sensitivity ratings are taken on-axis. So if they're off-axis, roughly by how many degrees? This bit doesn't have to be accurate but I'd need to make a few dBs allowance for it.
 

NewAcousticDimension

Active Member
I think the "sub handles the heavy lifting" subject is actually a little misunderstood. While running a higher crossover reduces the number of transient peaks in the speaker channels, it doesn't stop the speakers from having to reproduce full 20dB peaks. So it's more of a reduction in duty cycle on the amp/speakers, it doesn't mean they can be less capable SPL wise.

But isn't it correct in most cases that (for example) a x dB peak at 40Hz requires more power than an x dB peak at 120Hz? Hence, more power on average is required for the speakers the lower the crossover?
 

Mr Wolf

Well-known Member
But isn't it correct in most cases that (for example) a x dB peak at 40Hz requires more power than an x dB peak at 120Hz? Hence, more power on average is required for the speakers the lower the crossover?
I understand what you're saying but that's different. Ken's talking about using a crossover higher than the standard 80Hz, not running a lower one. You should never, ever run a crossover below the f3 point (i.e. when its FR is -3dB below its reference sensitivity line) of a speaker as it becomes massively inefficient below that point plus you'll lose a flat response. You don't want to run a crossover below the resonant frequency of a speaker's woofer as its impedance will dip below this point.

Take my front L/R B&W speakers as an example, their FR line is flat to about 55Hz and they have an f3 point of 44Hz. This chart shows their impedance/phase to frequency plot.

1651743292100.png


As I run a 80Hz crossover so you can see that the most power demanding frequency for the speaker to reproduce is 200Hz as it has the lowest impedance dip (circa 5-Ohms) above the crossover frequency. That wouldn't change if I dropped the crossover down to 60Hz or increased it to 120Hz. The resonant frequency of the woofer is where its impedance peaks (10-Ohms) which is 70Hz so that's where it's most power efficient. It's a vented speaker and the resonant frequency of its port is 40Hz (green line) which is where it will have a major impedance dip (4-Ohms) which you want to remove via a crossover.

In practice though, the lower the frequency the louder and longer the transients peaks tend to be which is why we talk about subs doing the "heavy lifting". This will be soundtrack dependent though and there are exceptions. The most power demanding peaks I've measured coming out of my LCR channels are from the machine gun fire on the Saving Private Ryan beach assault scene. These were full 20dB peaks well above the crossover.
 

kenshingintoki

Distinguished Member
I think the "sub handles the heavy lifting" subject is actually a little misunderstood. While running a higher crossover reduces the number of transient peaks in the speaker channels, it doesn't stop the speakers from having to reproduce full 20dB peaks. So it's more of a reduction in duty cycle on the amp/speakers, it doesn't mean they can be less capable SPL wise. The problem with going much over 80Hz is that the bass in some male voices can start to come out of the subs but if you need to reduce nulls then so be it. Personally I wouldn't want to go any higher than 100Hz though and would always run 80Hz if my room allowed it.


Normally I'd say no problem at all because Atmos channels only have max 14dB peaks (vs 20dB on LCRs and 17dB in bed surrounds) but those Arendals aren't the most efficient speakers out there plus, if I recall correctly, you listen pretty loudly in a fairly large room. That Arcam hasn't got the beefiest amp section either, I know many are simply bought and used as 11.1 processors.

I have the Arendal speaker specs to hand but if you want to give me their MLP distances, your room size and listening level I can run a few numbers for you. It also matters hugely how on-axis they are to the listener as all sensitivity ratings are taken on-axis. So if they're off-axis, roughly by how many degrees? This bit doesn't have to be accurate but I'd need to make a few dBs allowance for it.


I'll get the details for the second part in a bit mate.

For a crossover at 100hz, I can say I've used it and its absolutely awesome. No issue with boomy voices etc. I know I tried this when I had a very roughly calibrated BK Mono Plus and it wasn't great. Voices sounded awful but my response in room and integration of my current subs has left me very happy to increase that crossover. The mono 15s are much much more delicate in how they handle bass compared to other subs I've listened to which has made me value a tight articulate bass a lot more.

I got the idea from Mark who had a high crossover on a lot of this speakers a while back.
 

NewAcousticDimension

Active Member
I'll get the details for the second part in a bit mate.

For a crossover at 100hz, I can say I've used it and its absolutely awesome. No issue with boomy voices etc. I know I tried this when I had a very roughly calibrated BK Mono Plus and it wasn't great. Voices sounded awful but my response in room and integration of my current subs has left me very happy to increase that crossover. The mono 15s are much much more delicate in how they handle bass compared to other subs I've listened to which has made me value a tight articulate bass a lot more.

I got the idea from Mark who had a high crossover on a lot of this speakers a while back.

I read @Mr Wolf describing this week about using a £35 multi-meter to actually "real world" check the power demands - see link here:


It may be really interesting (especially if you report back) that after he has run the calculations for you and you're still unsure, if you get a meter, you could play some key content and establish for yourself if the Arcam if capable.

Another option would be to measure the power consumption of the Arcam with similar content playing but this is less precise, requires more estimation/assumption but has the advantage that you may already have something that can measure this.
 

Mr Wolf

Well-known Member
I'll get the details for the second part in a bit mate.

For a crossover at 100hz, I can say I've used it and its absolutely awesome. No issue with boomy voices etc. I know I tried this when I had a very roughly calibrated BK Mono Plus and it wasn't great. Voices sounded awful but my response in room and integration of my current subs has left me very happy to increase that crossover. The mono 15s are much much more delicate in how they handle bass compared to other subs I've listened to which has made me value a tight articulate bass a lot more.

I got the idea from Mark who had a high crossover on a lot of this speakers a while back.
Cool, if you give me the details for all your speakers I can model the whole system for you. It only takes me about 2 minutes to populate the spreadsheet's assumptions, that's the beauty of it. No rush.

Nothing wrong with a 100Hz crossover at all, especially as you have more than one sub that helps non-localisation. I've watched a lot of Anthony Grimani's videos where he is takes you through his custom installs (inc. Tom Cruise's home cinema) and he always uses at least four subs with crossovers between 80Hz and 100Hz. He'll always shoot for 80Hz but will increase it to help deal with nulls as required. I think it's above this level that you can run into issues as the average male voice is 125Hz. Some male voices are much lower but these are exceptional e.g. the voice of Darth Vader actor James Earl-Jones (aka King Joffy Jaffa) is apparently 85Hz. At the crossover frequency, the sub and the speakers are both 6dB down and making 50/50 in phase contribution to what you're hearing so you can see why 120Hz is not ideal if average males voices are 125Hz. If you have to run a crossover >100Hz I would definitely want the subs up front close to the screen.
 
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NewAcousticDimension

Active Member
I've watched a lot of Anthony Grimini's videos where he is takes you through his custom installs (inc. Tom Cruise's home cinema)

Thought I've gotta check this out, then Google is finding "gemini" instead... ends up it is Grimani.

Not being pedantic, just letting others know in case they want to look him up :)
 

Mr Wolf

Well-known Member
Thought I've gotta check this out, then Google is finding "gemini" instead... ends up it is Grimani.
Sorry, that was a typo. The best videos I've found are done with AVPro Edge and are aimed at educating professional installers as he's a CEDIA trainer. This is just one of them on subs.



I read @Mr Wolf describing this week about using a £35 multi-meter to actually "real world" check the power demands - see link here:
When I get time I'll create a whole thread on this at some point to share it in detail but for anyone interested in doing this yourself , you use a True RMS Multimeter. This is the one I use:

Amazon product

All you have to do is measure the actual AC voltage required for each speaker to generate 75dB test tones (or some other SPL level) at the MLP. Once you have that, you can extrapolate the voltage/power requirements for the peak SPL output levels. These are the results for my own 7.2 system assuming standard maximum 20dB peaks on the LCRs and 17dB peaks on the surrounds.

Input assumptions are the yellow boxes and the rest is formulae.

1651748037003.png


So at a -5dB volume level, my centre channel can potentially draw [email protected] (its nominal rating) on 20dB peaks. As that speaker has circa 4.0-Ohm dips at certain frequencies, that's still only [email protected] on a true worst case scenario. This is why my AVR never breaks into a sweat.

The meter can also measure peak power usage as it has an AC voltage peak detect feature.

It's amazing that the simple measurement of a speakers' actual in-room voltage sensitivity takes pretty much all the unknown variables (e.g. speaker sensitivity, speaker axis, dispersion loss, boundary gain) out of the equation so the result should be bang on the money.
 

rccarguy2

Distinguished Member
Hifi people have been sending full range to their speakers for decades it's typically fine to do so.

I can flip between five settings and full range what is sent to speakers (and respective frequency to sub) so in this image my sub <60hz and the stereo amps >60hz. In disabled speanrds get full range and sub gets no signal
 

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NewAcousticDimension

Active Member
Hifi people have been sending full range to their speakers for decades it's typically fine to do so.

I can flip between five settings and full range what is sent to speakers (and respective frequency to sub) so in this image my sub <60hz and the stereo amps >60hz. In disabled speanrds get full range and sub gets no signal

Where can you get those in the UK please? Apologies all for OFF TOPIC.
 

Conrad

Moderator
@Mr Wolf, does it make a difference if you use white or pink noise vs using a 1kHz test tone when getting the voltage requirements for 75dB?
 

rccarguy2

Distinguished Member
Where can you get those in the UK please? Apologies all for OFF TOPIC.

Mostly sold in the USA. Took ages to find one.

They're multi channel typically used for 5.1 dvd player RCA out into 5.1 analogue input (back then onboard decoders where very basic) so you could have advanced bass management.

Brilliant bit of kit, was going to sell it but since it's rare I'm keeping it
 

Mr Wolf

Well-known Member
@Mr Wolf, does it make a difference if you use white or pink noise vs using a 1kHz test tone when getting the voltage requirements for 75dB?
I don't think so. As noise levels are random I actually used the peak voltage hold feature in the meter to be conservative i.e. I recorded the maximum AC voltage the test tone generated. I even tried it with a sine wave at the most demanding (lowest impedance) frequency for the speaker and still got a very similar voltage result.

If you're going to do this, the meter I have uses standard 4mm female banana plug sockets for its probes so I just removed the probes and connected the meter directly to the spare bi-wiring terminals on each speaker (I don't bi-wire/bi-amp) with a 13AWG speaker cable. Minimum voltage loss that way.

You can also wire the meter in series to measure AC current flow. I bought a pair of meters so I can measure both simultaneously. AC current measurement is useful for identifying minimum impedance points with REW sine waves.
 

Mr Wolf

Well-known Member
I can flip between five settings and full range what is sent to speakers (and respective frequency to sub) so in this image my sub <60hz and the stereo amps >60hz. In disabled speanrds get full range and sub gets no signal
I guess that gadget is aimed at 2 channel HiFi users with amps that don't have active crossover circuits with memories.

My Yamaha AVR has 6 system wide preset memory banks (four of which are directly accessible from a button on the remote) that be can used to call up different crossover/speaker configurations on the fly. In fact they can even store the EQ settings so great for switching between movies and music as I prefer a 60Hz crossover for that.
 

rccarguy2

Distinguished Member
It was designed as 5.1 or possibly 6.1 biut can be used in a stereo system
 

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kenshingintoki

Distinguished Member
I read @Mr Wolf describing this week about using a £35 multi-meter to actually "real world" check the power demands - see link here:


It may be really interesting (especially if you report back) that after he has run the calculations for you and you're still unsure, if you get a meter, you could play some key content and establish for yourself if the Arcam if capable.

Another option would be to measure the power consumption of the Arcam with similar content playing but this is less precise, requires more estimation/assumption but has the advantage that you may already have something that can measure this.


I'm just going to plug the Arcam in and run the 2 scenes I know trip it up when I had 7 speakers hooked up to it.

Bad Boys for Life intro with the car and The Dark Knight car chase scene both at reference.

If my speakers are still playing by the end of those sequences, I think it can provide juice.

If not, then I'm very irritated I have to find another amp cos I CBA.
 

rccarguy2

Distinguished Member
I'm just going to plug the Arcam in and run the 2 scenes I know trip it up when I had 7 speakers hooked up to it.

Bad Boys for Life intro with the car and The Dark Knight car chase scene both at reference.

If my speakers are still playing by the end of those sequences, I think it can provide juice.

If not, then I'm very irritated I have to find another amp cos I CBA.

You damaged your speakers being powered by the arcam?
 

kenshingintoki

Distinguished Member

rccarguy2

Distinguished Member

kenshingintoki

Distinguished Member

rccarguy2

Distinguished Member
Yup I’m buying an Apollon pretty soon. Got a few other purchases to make first tho. Chose them due to the adjustable gain. Seem like the best on the market price : performance

Really need to get one from within the UK you're looking at another £1500 ontop!
 

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