What is "reference level"? - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 81 Old 06-29-10, 04:03 PM
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Re: What is "reference level"?

Wow houses must vary considerably: with an 18 and two 12's in the HT I can easily hear a 50 cal machine gun outside or at the front door when I watched the Big Red One; I figured someone would think it was the real thing if they walked by! lol!!!
Our windows don't rattle annoyingly, nor have I had any 'walking' objects. It's not too noticeable past the front curb, maybe 20ft from the front door; I don't want to listen at higher volumes than that anyway. The entire house thunders though!


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post #22 of 81 Old 07-01-10, 08:52 AM
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Re: What is "reference level"?

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A9X wrote: View Post
I live in an apartment and have done this with my neighbours and don't see how it is passive aggressive. I also asked that if it became an issue, to let me know 'when' so we could work out what I was watching, how loud etc and if it were at an odd time so I could maximise my fun at minimum inconvenience to them. So far zero complaints, but I tend to crank it at reasonable times and watch dialogue driven flicks at less friendly times like late at night.

Movies I also find are less of an issue than modern music with a regular beat. Doof, doof is more annoying to many than a couple of minutes of not readily identifiable loud noise from a movie which is not consistent or predictable.

I'm still going to add more soundproofing as I work on the room acoustics as I would like even less potential for neighbour disturbance and for me to play louder at times.

Solid walls and acreage would be nice but lotto-win dream for many of us unfortunately.
Yeah, maybe "passive aggressive" was the wrong language to indite; What I meant was that the more subtle hints regarding your inclination to be a good neighbor that you can express to the surrounding community, the more leniency you will be given towards playing movies at higher volume levels now and then as a direct result. If only everyone knew how far a smile would take them, I should think there would be a lot more smiling in the world today (even if for purely selfish reasons )

As for a house on 10 acres.. It sure seemed like a pipe dream to me 2 months ago as well, but simply asking a family friend/realtor if I had a chance at home ownership turned out to be one of the best decisions I've ever made, because I was pleasantly surprised to learn that even owning a home, period, was possible for me now. If you have a steady job, look into buying- you might just be as surprised as I was!
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Being that my neighbors are hard to track down i had conciderd putting a sign out in the front yard telling them that if it's too loud just let me know instead of calling the police. But that would just invite thieves, allthough with too ''monster dogs'' in the house i really don't think any uninvited guests would enter.

My solution to the problem has been to keep the volume at a recpectable level, i've got 13 month old twins now anyways so turning the volume up isn't really an option anymore. Problem solved.
Lol, turn it down and problem solved! That's a good point on inadvertantly letting the world know you have expensive gear inside as well.. I'm not used to having anything worth stealing, so this is taking some getting used to haha
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post #23 of 81 Old 07-01-10, 05:33 PM
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Re: What is "reference level"?

Yeah like i said also, i don't think any uninvited guest will attempt to come in do to my ''security dogs''. Also i've relized that when the kids are at grandma and grandpas as long as it's the right time of day it's ok to rock out a bit but advertising your awesome setup to the world isn't really the best idea anyhow.
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post #24 of 81 Old 09-08-10, 11:33 PM
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Re: What is "reference level"?

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As for a house on 10 acres.. It sure seemed like a pipe dream to me 2 months ago as well, but simply asking a family friend/realtor if I had a chance at home ownership turned out to be one of the best decisions I've ever made, because I was pleasantly surprised to learn that even owning a home, period, was possible for me now. If you have a steady job, look into buying- you might just be as surprised as I was!
Totally agree.
plus, IMHO:

paying rent means your money goes away
paying mortgage means your money is here to stay
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post #25 of 81 Old 11-17-10, 09:28 PM
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Re: What is "reference level"?

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As for a house on 10 acres.. It sure seemed like a pipe dream to me 2 months ago as well, but simply asking a family friend/realtor if I had a chance at home ownership turned out to be one of the best decisions I've ever made, because I was pleasantly surprised to learn that even owning a home, period, was possible for me now. If you have a steady job, look into buying- you might just be as surprised as I was!

I just recently bought my first house. With the low interest rates, I'm paying $225 more per month for my single family detached house. For me, it was totally worth it to not have to share walls. Ahhhh... I can finally play my games & movies as loud as I want. And I can turn my subwoofer up past 2. It goes to 10.
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post #26 of 81 Old 11-17-10, 09:36 PM
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Re: What is "reference level"?

Reference level is when you have An XPA-1 hooked up to each of your towers and you start to smell magic smoke. Oh, wait, that would be beyond reference level.
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post #27 of 81 Old 11-18-10, 07:33 AM
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Re: What is "reference level"?

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85db is actually reference level, and in order to have a reference capable system, you need 20db dynamic headroom from each channel. 75db is what some discs or receivers have you calibrate to using their test tones simply because 10db less is easier to withstand during calibration. The LFE channel is 10db louder, so reference is 95db with the need to be able to handle 115db.

So to sum it up, if you are designing new speakers, the capability you need is for them to reach 105db across their intended range at your seat and the subwoofer 115db. If you cross the speakers over at 80hz, then the subwoofer system actually needs to be able to do ~118db.
What do you mean by "20 dB dynamic headroom"? How does one calculate and/or measure the available dynamic headroom?
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post #28 of 81 Old 11-18-10, 09:43 AM
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Re: What is "reference level"?

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What do you mean by "20 dB dynamic headroom"? How does one calculate and/or measure the available dynamic headroom?
You use the onlline SPL calculator (google it) and see if your amplifier can drive your mains to 105 db at the listening position, and you can find out if your sub can do 115 db AT 20HZin various ways.

However that doesn't factor in thermal compression. Even if your amp can drive your speakers to 105db, your speakers may lose their compusre at those peaks.

Most people's systems can't do reference levels properly. Regular tweeters just don't have the thermal power handling to do so. You usually need some sort of waveguide or horn loading for the tweeter, or a non-conventional multi-tweeter speaker design like the RBH T2 system. My tweeters for example actually have limiting in which they can't sustain anything above 103 db before the protection kicks in. They can do a dynamic transient higher, but not sustained. I've never heard my speakers compress, but then I don't own a pair of JTR Triple 8s to reference them against either.

Professional audio speakers are much more capable of the dynamic range which we associate with movie reference levels.
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post #29 of 81 Old 11-18-10, 09:32 PM
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Re: What is "reference level"?

The SPL calculator does not address "dynamic headroom". It actually disclaims dynamic headroom in the text. Quote: "This calculator does not account for room acoustics, amplifier dynamic headroom or off axis listening positions." If you are really expecting 20 dB of crest factor in your program material, you will need a 10 kW amplifier for a typical home theater. Of course no HT speaker can withstand 10 kW, even on a program peak. I think the old rule of 10-13 dB of headroom is more realistic of program material. Remember we are already considering the loudest passage that the sound system will encounter.
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post #30 of 81 Old 11-18-10, 11:48 PM
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Re: What is "reference level"?

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The SPL calculator does not address "dynamic headroom". It actually disclaims dynamic headroom in the text. Quote: "This calculator does not account for room acoustics, amplifier dynamic headroom or off axis listening positions."
Dynamic amplifier power is nothing more than marketing rubbish.

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gsmollin wrote: View Post
If you are really expecting 20 dB of crest factor in your program material, you will need a 10 kW amplifier for a typical home theater. Of course no HT speaker can withstand 10 kW, even on a program peak. I think the old rule of 10-13 dB of headroom is more realistic of program material. Remember we are already considering the loudest passage that the sound system will encounter.
10kW, really? For an 88dB speaker on it's own at 4m with 800W you get THX ref level at the LP of 105dB. As I presume it is 2 or 4 pi space and not a room where the reverberant sound will also add to the apparent level, and the recommendation from Toole (IIRC, not in front of me ATM) is 3dB not 6dB loss per doubling of distance, then we're back to 400W. High, but not unrealistic.

Now get some sensible speakers with decent efficiency and volume displacement and reference at the LP is easy.

Dialogue is supposed to be mastered at the 75-85dB level and with peak loudness at 105dB, a 20dB+ crest factor is not unrealistic. Just make sure you have enough speaker and amp to do it.

Calculator used is from here. [first google hit]
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