Big Size Home Theater Challenges

[caspian1985]

It doesn't. Reference level capability is 85 dB SPL, with 20 dB of headroom. Reference level playback for movies is simply playing back the movie at the level it was originally mixed. Nothing more, nothing less.

It does, according to the RP22 spec or at least that is how I read it . See page 77 the footnote below the SPL guidelines:

“Sound Pressure Level at the Reference Seating Position is the recommended minimum long term SPL”. And the RP22 defines that SPL as 105 dB, which is what I meant - there is no home theater where you’d need long term SPL capability of 105dB, because you always have to have dynamic head room above your long term SPL goal. So to me the THX spec makes more sense, 85dB capability at the seating position with 20dB headroom for dynamics.

Correct.



Some films are mixed too hot, though. In those cases, playback volume needs to be dialed down from reference to compensate.

However, for the most part, playback at reference level in a HT boils down largely to capable equipment that's well calibrated and a thoughtfully engineered room that allows for sound to decay quickly enough for reflections to not be overbearing at reference levels.

 

[liverpool_for_life]

It does, according to the RP22 spec or at least that is how I read it .

Hmm.

Sound Pressure Level at the Reference Seating Position is the recommended minimum long term SPL according to
AES75-2022 or ANSI-CTA-2034-A, Section 8.

Don't have access to either standards document, but, from looking around, I'd wager that the long term SPL being described above refers to the length of stimulus applied (60s for long term SPL capability measurement).

As for your earlier comment about some of the criteria in RP22 being ridiculous, I'll disagree. The requirements laid out merely point to how meticulous the design/engineering of the room, choice of equipment, and finally, calibration needs to be in order to get to a high-performance audio space. It was certainly eye-opening for me.

I've long felt there's a significant difference between the potential of equipment and performance in my room and this document confirmed it (equipment possibly qualifying for Level 2 capability with performance not hitting all Level 1 targets even). If I ever build a dedicated HT, RP22 will serve as the foundation of the standards to aspire to. In the meantime, I'll enjoy my current space even if it doesn't get close to meeting the specs for Level 1, never mind Level 4.

We finally have a document with objective standards for various levels of audio performance in a home environment and that's a good thing. Look forward to the follow-up document that will describe how to measure for the performance parameters laid out in RP22.

 

[caspian1985]

Hmm.



Don't have access to either standards document, but, from looking around, I'd wager that the long term SPL being described above refers to the length of stimulus applied (60s for long term SPL capability measurement).

You can get it from the CEDIA website.

This would make sense except the RP22 document gives a “worked example”. In that, it uses the speakers RMS power rating, which implies long term ( ie many minutes if not hours ) when calculating the SPL level, which is different from the 60s you’ve mentioned.

As for your earlier comment about some of the criteria in RP22 being ridiculous, I'll disagree. The requirements laid out merely point to how meticulous the design/engineering of the room, choice of equipment, and finally, calibration needs to be in order to get to a high-performance audio space. It was certainly eye-opening for me.

I think they’re two different points - a document can be have exacting and meticulous criteria and also have unnecessarily high thresholds required. RP22 IMHO is well thought through, but requires over specification. Remember it’s written by industry professionals, so there’s a certain incentive to upsell

I've long felt there's a significant difference between the potential of equipment and performance in my room and this document confirmed it (equipment possibly qualifying for Level 2 capability with performance not hitting all Level 1 targets even). If I ever build a dedicated HT, RP22 will serve as the foundation of the standards to aspire to. In the meantime, I'll enjoy my current space even if it doesn't get close to meeting the specs for Level 1, never mind Level 4.

We finally have a document with objective standards for various levels of audio performance in a home environment and that's a good thing. Look forward to the follow-up document that will describe how to measure for the performance parameters laid out in RP22.

 

[liverpool_for_life]

You can get it from the CEDIA website.

I was referring to AES75-2022 or ANSI-CTA-2034-A.

This would make sense except the RP22 document gives a “worked example”. In that, it uses the speakers RMS power rating,

It uses peak power handling capacity.

From pg. 77:

Calculation Example: SPL at seating positions based on speaker sensitivity and peak power
A speaker in the front of a room has a sensitivity of 96 dB (meaning it produces 96 dB SPL at 1 m with a 2.83
Vrms test signal). The RSP is 4 m away, and the last row of seats is 8 m away. If the speaker can handle a 500
watt peak power without audible distortion, dynamic compression, or failure, the calculation for predicting
the maximum SPL capacity would be as follows:
i. 500 watts is approximately a 9-step doubling sequence (2 to the power of 9, or 29) from 1 watt.
9 x 3 (dB increase per doubling of power) = 27 dBW (dB relative to 1 W into an 8 Ω load)
ii. Therefore, 96 dB SPL at 1 watt (speaker sensitivity) + 27 dBW of power beyond 1 watt
= 123 dB SPL of peak sound at 1m for that speaker
iii. Doubling the distance to 2 m loses 6 dB due to propagation loss, and doubling again to 4 m loses
another 6 dB, meaning 12 dB loss at 4 meters.
iv. The maximum peak SPL at 4 meters would be 123 - 12 = 111 dB at the RSP. This would provide
6 dB of headroom over the 105 dB peak reference level.
v. Another doubling of distance to 8m results in a maximum peak SPL of 105 dB at the back row.

(emphasis supplied)

I think they’re two different points - a document can be have exacting and meticulous criteria and also have unnecessarily high thresholds required.

The latter part is subjective, so to each their own.

Remember it’s written by industry professionals, so there’s a certain incentive to upsell

Not disagreeing that the incentive to upsell exists, but IMO, that wasn't the point of RP22. It may well be that folks employ professionals to build out a high-performance HT that wouldn't have done so prior to RP22, but that will be because they're better educated and want standardized performance.

 

[caspian1985]

I was referring to AES75-2022 or ANSI-CTA-2034-A.



It uses peak power handling capacity.

From pg. 77:


(emphasis supplied)

I missed that my bad. Then 105dB peak at listening position makes sense as that is the dynamic headroom

The latter part is subjective, so to each their own.



Not disagreeing that the incentive to upsell exists, but IMO, that wasn't the point of RP22. It may well be that folks employ professionals to build out a high-performance HT that wouldn't have done so prior to RP22, but that will be because they're better educated and want standardized performance.