CEDIA RP22 Discussion

[Snoopy8]

1 hour ago, Wavetrain said:

Their design would always produce good off axis response, but they fail at the primary requirement of RP22 & that is SPL. At a 3m seating distance their top model is 6dB below recommendations. 

Is there some place that I can find a table of speakers with RP22 measurements?

[Wavetrain]

1 minute ago, Snoopy8 said:

Is there some place that I can find a table of speakers with RP22 measurements?

RP22 is a recommended guide, not a document detailing how to achieve the standards. SPL would need to be calculated, as would dispersion patterns for even seat coverage.

 

One if the next documents will deal with manufacturer requirements to be considered with RP22.

 

There are a number of documents to come from CEDIA including video design, system verification procedures of RP22, etc.

[Wavetrain]

I lecture in RP22 for CEDIA in Aus/NZ, but this is way off topic for this thread really. 
 

Perhaps it’s for another dedicated thread, as it will get very involved. I’d consider fairly basic training to take 3 days, but even that is just introducing concepts covered in RP22. It would take most people 3-5 years practical application to fully understand it. It’s not for lay people or beginners.

 

That said there are a number of people on these forums who are incredibly dedicated & more knowledgeable then a lot of industry professionals, but this is certainly a minority.

Edited November 15, 2023 by Wavetrain

[Snoopy8]

@Wavetrain  agree we should not take this OT to discuss CEDIA RP22, but you got me curious when you said the top Phantom model was 6 dB below requirements.  Does it then make it unsuitable for a Dante based HT?  

 

And how much attention should "we amateurs" place on CEDIA RP22 for our own HT systems (Dante & non Dante)?

[Wavetrain]

13 minutes ago, Snoopy8 said:

@Wavetrain  agree we should not take this OT to discuss CEDIA RP22, but you got me curious when you said the top Phantom model was 6 dB below requirements.  Does it then make it unsuitable for a Dante based HT?  

 

And how much attention should "we amateurs" place on CEDIA RP22 for our own HT systems (Dante & non Dante)?

It’s pretty simple math. In an acoustically correct room, the SPL drop is 6dB for every doubling of distance (distance in meters x 20log on a calculator). The top model is 108dB at 1m, so 102dB at 2m & 96dB at 4m (or 99dB at 3m). The standard for RP22 and all cinemas for decades is peaks of 105dB. Dolby would dictate 3dB of headroom, which is how we rate most Elementi active speakers. 3dB being half the amplifier power held in reserve.

 

The variable here would be poor acoustics. The SPL drop would be more 3-4.5dB per doubling of distance, but then you wouldn’t want to listen to surround sound as the sound field would be jumbled, voices hard to understand & it would have a high pitched edge.

[Grizaudio]

ISL (Inverse Square Law) is absolutely a good rule of thumb guide, but its worth noting the theory doesn't typically hold in small spaces. . 

 

As David has inadvertently stated, ISL assumes ideal conditions. 

Which is essentially a point source radiating in free space - omni directionally (Sound is free to propagate and expand both vertically and horizontally over distance).   

 

Inverse square law doesn't usually hold indoors (especially in small rooms), due to the impact of reflections, diffraction, reverberation, and standing waves. 

These interactions prevent acoustic energy from radiating in a uniform manner over distance, which typically creates deviation from expected ISL SPL reduction.  

 

This is the value in selecting speaker solutions which have accurate prediction modelling software.

Allowing designers to predict and refine system design in software for any room accurately.

 

These software prediction tools accurately (very accurately) predict SPL & Frequency over nominated area(s), considering factors such as speaker mounting positions, (x,y,z axis), surface types, air temps, acoustic travel outside room, for any number of speakers in the manufacturers range. Software examples include: EASE (Although EASE doesn't model bass frequencies), EAW have Resolution, d&B have Array Calc, Meyer have Mapp 3D, etc. 

 

If I was building a high performance cinema, one option would be to select Pro Sound Dante/Aes67 DSP amplifiers and pair with an appropriate and capable Processor/Matrix. 

I would then carefully model the space, and select a speaker solution with the SPL performance capability and directivity to best match application. 

 

Design software (as listed above) allows careful design modelling for in room predicts.

Broadband SPL A/C,  RAW & EQ'd response over area, Max SPL, SPL v's Frequency response predictions across area (using very fine set points), SPL plots over area @ any desired octave/frequency.  

These software tools are extremely accurate, and help design high performing acoustic solutions. Takes the guess work away. 

 

Edited November 16, 2023 by Grizaudio
typo

[Wavetrain]

2 hours ago, Grizaudio said:

SL (Inverse Square Law) is absolutely a good rule of thumb guide, but its worth noting the theory doesn't typically hold in small spaces. .

It absolutely does hold for small room acoustics, which is most home cinemas. As noted it would require poor acoustics to not hold true, which is why it’s the required formula for RP22.

 

2 hours ago, Grizaudio said:

As David has inadvertently stated, ISL assumes ideal conditions.

Nothing inadvertent. I think it was stated fairly clearly. If you are professionally designing a cinema, there is nothing but ideal IMO. The alternative would be poor voice intelligibility and localisation, plus a skewed frequency response.

 

2 hours ago, Grizaudio said:

These software prediction tools accurately (very accurately) predict SPL & Frequency over nominated area(s), considering factors such as speaker mounting positions, (x,y,z axis), surface types, air temps, acoustic travel outside room, for any number of speakers in the manufacturers range. Software examples include: EASE (Although EASE doesn't model bass frequencies), EAW have Resolution, d&B have Array Calc, Meyer have Mapp 3D, etc. 

These software packages are not going to acoustically engineer the cinema for you. They are accurate for what you have stated, but not the room sound signature or true sound quality at seating positions.

 

I would champion any situation where the room is being engineered, as for most installations, this is not an occurring IMO. As a judge on the EMEA (Europe)  awards, what stood at most was two things:

 

1) A general lack of engineering to produce industry outcomes.

2) An over reliance on auto EQ without an understanding of bass design.

 

These are the types of things that RP22 highlights and why it’s so important.

[Grizaudio]

8 hours ago, Wavetrain said:

It absolutely does hold for small room acoustics, which is most home cinemas. As noted it would require poor acoustics to not hold true, which is why it’s the required formula for RP22.

 

Last comment on ISL... I don't want to derail things further.  

 

David, sounds like you are creating some amazing acoustic spaces, with excellent attention to room design, absorption and diffusion. 

Your ground up approach to cinema design should be celebrated and acknowledged.   

 

At the end of the day, ISL adherence will be depend on a few factors, but if you are correctly addressing acoustics (as you have stated) the law will be obeyed within acceptable limits no doubt.  

For me personally, I would simply select a speaker with adequate pattern control and  SPL headroom, and treat room to address concerns. 

 

For the average room, an un-impeded sound field, speaker directivity, location of measurements x,y,z (I.e. free field, or reverberant field), a point source's ability to radiate & propagate acoustic energy omni directionally without surface interference, the quality of room absorption and diffusion, etc will all influence variance to ISL. 

 

Even in open spaces firing audio large distances, say 100m, you can see & measure the impact (even if its small) of single surfaces or boundaries on SPL over distance. 

This phenomenon becomes critical, and highly specialised/complex when dealing with environmental acoustics and boundary impacts/SPL reduction over distance - for noise predictions etc.  

 

8 hours ago, Wavetrain said:

Nothing inadvertent. I think it was stated fairly clearly. If you are professionally designing a cinema, there is nothing but ideal IMO. The alternative would be poor voice intelligibility and localisation, plus a skewed frequency response.

 

As a professional designer and consultant, you approach cinema design from all the right places, but this is quite different to the average Joe placing theatre hardware into the average living room space.  

 

8 hours ago, Wavetrain said:

I would champion any situation where the room is being engineered, as for most installations, this is not an occurring IMO. As a judge on the EMEA (Europe)  awards, what stood at most was two things:

1) A general lack of engineering to produce industry outcomes.

2) An over reliance on auto EQ without an understanding of bass design.

 

These are the types of things that RP22 highlights and why it’s so important.

 

Absolutely... 100% 

 

My passion is Pro Sound, not Cinema. But I would absolutely agree, there is not enough emphasis placed on well engineered simulated acoustic solutions. 

The software packages I listed previously are obviously not room design simulation packages, you need a different package for that.

However once the room is designed, speaker simulation software becomes a hyper valuable tool in predicting acoustic energy in space. 

Edited November 16, 2023 by Grizaudio

[Wavetrain]

37 minutes ago, Grizaudio said:

 

Last comment on ISL... I don't want to derail things further.  

 

David, sounds like you are creating some amazing acoustic spaces, with excellent attention to room design, absorption and diffusion. 

Your ground up approach to cinema design should be celebrated and acknowledged.   

 

At the end of the day, ISL adherence will be depend on a few factors, but if you are correctly addressing acoustics (as you have stated) the law will be obeyed within acceptable limits no doubt.  

For me personally, I would simply select a speaker with adequate pattern control and  SPL headroom, and treat room to address concerns. 

 

For the average room, an un-impeded sound field, speaker directivity, location of measurements x,y,z (I.e. free field, or reverberant field), a point source's ability to radiate & propagate acoustic energy omni directionally without surface interference, the quality of room absorption and diffusion, etc will all influence variance to ISL. 

 

Even in open spaces firing audio large distances, say 100m, you can see & measure the impact (even if its small) of single surfaces or boundaries on SPL over distance. 

This phenomenon becomes critical, and highly specialised/complex when dealing with environmental acoustics and boundary impacts/SPL reduction over distance - for noise predictions etc.  

 

 

As a professional designer and consultant, you approach cinema design from all the right places, but this is quite different to the average Joe placing theatre hardware into the average living room space.  

 

 

Absolutely... 100% 

 

My passion is Pro Sound, not Cinema. But I would absolutely agree, there is not enough emphasis placed on well engineered simulated acoustic solutions. 

The software packages I listed previously are obviously not room design simulation packages, you need a different package for that.

However once the room is designed, speaker simulation software becomes a hyper valuable tool in predicting acoustic energy in space. 

We 100% agree with each other, just coming from two different directions & fields.