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event horizon 01-16-10 02:23 PM

What is "reference level"?
 

Having just typed this into "search" on here & having found over 20 pages which really weren't what i was looking for i thought i'd ask - what is "reference level"? That'd be with regards to films & home cinema..

This year i'm hoping to build what should be my final speaker system :T

My idea is simply to design & build a 2 channel system that will produce as little distortion as possible & generate 116db from 20Hz to whatever the poor tweeter will withstand. Yes high frequencies do tend to drop off somewhat so i live in hope. The system will be 4 way active per channel.

As well as this i'll be rebuilding Paradigm's top of the range C5 V2 centre speaker & adding what i'd regard as a driver that can do real bass to it 15" with decent excursion. Poor thing is sitting here in it's box waiting for me to pull it to bits :D

Rear speakers aren't a problem as they'll be much nearer me than the front & centre speakers. Not sure i need to fuss over a sub as a few staff members have put my mind to rest that the LFE is directed to the front left & right speakers when it's set to "off".

So, can someone help me & let me know what is meant by "reference level" when dealing with films etc.

I guess as long as it's less than 116db i have nothing to fuss over as that output would be anechoic & the room will add some gain at low frequencies, at a guess i'm probably looking at 120db+ at 20Hz & 115db at 15Hz with what i'm going to build.

Thanks for your time ;)

Mark.

tonyvdb 01-16-10 02:45 PM

Re: What is "reference level"?
 

Reference level is the volume at 75db (decibels) in your room using full band pink noise. When you set up your system and you run pink noise through your speakers one at a time setting each level using an SPL meter to 75db you will (after all channels are done) and your volume control is set to 0db you will achieve "reference" when playing back movies or music. Movies will tend to reach peaks of 115db with your system set up properly.

This is not always easy to do as most home theatre systems can not reproduce this without distortion and is usually louder than most people go. Unless you have fairly expensive gear and larger speakers you likely wont achieve this without distortion.

event horizon 01-16-10 02:58 PM

Re: What is "reference level"?
 

Quote:

tonyvdb wrote: (Post 226446)
This is not always easy to do as most home theatre systems can not reproduce this without distortion and is usually louder than most people go. Unless you have fairly expensive gear and larger speakers you likely wont achieve this without distortion.

Cheers Tony, thanks for taking the time out to reply :T

I'm mainly a 2 channel man but HT has given me a bug (as well as a huge projector screen & 1080P tv), definately since one music label i listen to a lot does a lot of 5.1 DTS music releases. Yes, i'll agree that the volume level that i should likely attain will be ridiculous, which is precisely the point! It should mean that any sane volume level will be reproduced with minimal distortion.

All via sealed boxes btw, i'm not in to reflex muddiness. Ta again for the reply. 75 db, i'll say nothing more :D

SteveCallas 01-16-10 06:43 PM

Re: What is "reference level"?
 

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.

event horizon 01-17-10 01:35 PM

Re: What is "reference level"?
 

Quote:

SteveCallas wrote: (Post 226502)
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.

Cheers Steve, looks like i should well be able to manage that :whistling: No problem whatsoever with the full range stuff, though i'll be pushing it with the bass end possibly :blink:

Any idea on what the "sub" would need to output if crossed over at 100Hz? The only reason i ask is simply because i'll be doing things a little differently. You see i want the main left & right speakers to be full range for stereo (music man you see) & they'll be using 2 x 15" in a sealed box for bass (each side). These drivers have a one way Xmax of 17.5mm (35mm pk-pk). Now WINisd pro tells me i should get approximately 116Db at 1M with these drivers (excursion limited) @ 20Hz, but that's anechoic.

I'll not be running a sub channel as i've been reliably informed that if i set this to "none" it'll force all the bass to the front left & right speakers when watching films. However there will be another 15" driver in a sealed box added to the centre channel & this one has an Xmax of 14mm one way which should happily produce another 102Db @ 20Hz or add another 2Db to the output. I'm sure that like the left & right front channels there is bass applied to the centre channel, even if a sub is enabled.

The surround speakers also happen to happily go down to 27.5Hz to, though at a lesser level. They'll be approximately 1M from me behind me to the left & right strangely enough :D


You know, listening to a single bass driver of the same size doing it's thing i'm having incredible difficulty in imagining what 4 of them would do at 20Hz. According to equal loudness curves the output will virtually triple in loudness (actual volume level) with doubling the drivers at 20Hz & then do the same again with 4 drivers :rofl: Think i'm going to need to cure the door from rattling & other stuff besides when this gets operational.

Cheers for your input & have a good 2010!

Mark.

SteveCallas 01-17-10 02:03 PM

Re: What is "reference level"?
 

If you don't have a dedicated subwoofer, then the LFE channel will be directed into only the L&R mains. Every other channel would need to be able to handle 105db across the entire intended frequency range. The L&R mains would need to be able to handle 115.4db below 120hz and 105db above 120hz.

Keep in mind, you probably won't listen at reference, it is quite loud. Also, remember that these upper limits for reference level capabilities need to be achieved at the seat, not at 1m from the drivers.

event horizon 01-17-10 02:34 PM

Re: What is "reference level"?
 

Cheers Steve, yes the left & right mains will be good for 116Db (1M) from anywhere from 600Hz down to 100Hz where they cross over to the 15" bass drivers (that's per channel). The bass drivers will be excursion limited to 109Db per channel but at 20Hz, they can do a lot more at a higher frequency as you can probably imagine.

Looks like i have it sussed & yes you are right - the volume level will be nuts. Again the idea being that you aren't pushing the system at any volume until it becomes uncomfortable to the listener.

It should result in a low distortion system at any reasonably acceptable level :T It'll just have some reserves :D

SteveCallas 01-17-10 05:39 PM

Re: What is "reference level"?
 

If the speakers are near the corners or a wall, you will get boundary gain - that will help. Also, room gain will set in at some point on the low end.

Based on how you described your setup, I take it you are going to run every channel as "large" and set the sub to "none"? Every speakers will get it's full 3hz-20khz signal and the mains will also get the 3hz-120hz LFE channel.

tonyvdb 01-17-10 05:57 PM

Re: What is "reference level"?
 

Quote:

SteveCallas wrote: (Post 226799)
If the speakers are near the corners or a wall, you will get boundary gain - that will help.

This is true for the sub but never a good idea for the mains or surrounds. Having speakers in or too near a corner will cause cancellation of some of the frequencies due to reflection off the side walls called first reflection cancellation.

Jon Liu 01-18-10 10:55 AM

Re: What is "reference level"?
 

Like Tony said, corner loading speakers even subwoofers isn't necessarily the best thing to do. A lot of times boundary gain helps boost levels, but it doesn't necessarily boost all frequencies equally causing some cancellation as Tony mentioned, too. For subwoofers, I tend to find corner-loading them make them sound boomy.

As far as reference level at home, personally I find it somewhat hard to listen at that level. I usually listen at anywhere between -10dB to -20dB under reference at home. I don't know, it's not that it's necessarily that loud, but it just feels different. Maybe it's just a combination of things, like worrying about neighbors, worrying about who else is home, etc.


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