Left-Right Balance: It's important

[macc]

Originally Posted by bob katz

I also suggest you get the Chesky test disc with the LEDR test and use it to test for any room reflection/boundary issues that are intefering with imaging.


…

Using an SPL meter located dead center, confirm that the measured SPLs of each loudspeaker are the same, within a tenth. If this does not match what you heard, then either your ears or your monitors' frequency responses are not balanced, OR, your room acoustics are causing reflections that are affecting the left-right imaging. That's where the LEDR test comes in.

I’ve been really keen to find out more detail about the LEDR test and how to interpret it. I’ve read the article here - Stereophile: Take Me to Your LEDR! - about 100 times, but would love to have a little more information on how best to use the test to one’s advantage. That article is 20 years old, amazingly, so I was hoping you could share any further insights/experiences in how best to interpret what it is telling you. It would be much appreciated. There is also a mention of a grading system at the end of that article, did this ever come about?

I have been meaning to start a thread about it for a while, but as this has come up…

Thanks!

[lucey]

The Hacienda record 'Loud is the Night' that I did last year was all 60s panning ... very cool, well liked, well reviewed. LCR is a good start for most records.

[bob katz]

Originally Posted by macc

I’ve been really keen to find out more detail about the LEDR test and how to interpret it. I’ve read the article here - Stereophile: Take Me to Your LEDR! - about 100 times, but would love to have a little more information on how best to use the test to one’s advantage. That article is 20 years old, amazingly, so I was hoping you could share any further insights/experiences in how best to interpret what it is telling you. It would be much appreciated. There is also a mention of a grading system at the end of that article, did this ever come about?

I have been meaning to start a thread about it for a while, but as this has come up…

Thanks!

Ask away and I'll take you to your LEDR! We'll start by saying that the LEDR test is a computer-generated signal produced by Doug Jones in the days when it took 24 hours to generate a 1 second long sample! It's amazing how useful it continues to be. The comb filtering in the LEDR signal will clue you into nasty reflections in any of the directions that the signal can (or cannot) go.

BK

[dcollins]

Originally Posted by macc

I’ve been really keen to find out more detail about the LEDR test and how to interpret it. I’ve read the article here - Stereophile: Take Me to Your LEDR! - about 100 times, but would love to have a little more information on how best to use the test to one’s advantage. That article is 20 years old, amazingly, so I was hoping you could share any further insights/experiences in how best to interpret what it is telling you. It would be much appreciated. There is also a mention of a grading system at the end of that article, did this ever come about?

I wouldn't worry about it. The single most important thing is to get a comfortable translatable frequency balance in your room. When I think of the rooms that I'm familiar with that consistently turn out great work they didn't use it.

While I have that LEDR test signal and it's interesting to hear it move up and around, I don't adjust the room based on it.


DC

[macc]

Well, ok then...

Straight off: Room's too small really but I've worked, and continue to work, ridiculously hard on it. There was a thread here that converted me from 'don't bother' to 'bother'. Very well treated, with more on the way. All main reflection points well covered at least. Doing good work (apparently) and all that so doing alright at the minute, considering.

On K+H O300s, at about 4.5 feet. I've had my fiancee (who is gorgeous but essentially deaf) do the LEDR test while I watched, just to confirm it all. So;

Up - Sits in the speaker for the first half-second and then goes up up up. With eyes closed, my fiancee points about 4-5 feet in the air. BUT in the last foot it comes in to centre, both sides. Like an ' r ' - straight up, but then in to centre in the last foot or so of height.

Over - Sits still for half a second, moves inwards maybe 6 inches laterally - like the last path - before moving truly up and over. Doesn't go quite as high as the Up path but it feels like if the sound was at double the tempo, it might catch that high point, almost like it goes past it between beats. My missus points up some way, but maybe a foot short of the Up height.

Lateral - seems nice to me. Describes a pretty straight line in 3d space between speakers, maybe a slight hold up before it gets moving but not like the others.

Diagnose away! This is better than I could have hoped - thanks Bob, from another Bob

[macc]

Originally Posted by dcollins

I wouldn't worry about it. The single most important thing is to get a comfortable translatable frequency balance in your room. When I think of the rooms that I'm familiar with that consistently turn out great work they didn't use it.

While I have that LEDR test signal and it's interesting to hear it move up and around, I don't adjust the room based on it.


DC

Thanks Mr. Collins. I certainly wouldn't do anything drastic based on it, I'm doing good work (I'm told). But if it gives any clues to improving anything then it might be useful. If there's nothing more to be had from my room then so be it, and I'll try not to mess up a good thing... but you never know.

This forum is brilliant. Despite wading into the middle of your low-key running battle, thank you both.

[Adam Dempsey]

Originally Posted by Lagerfeldt

I love hard panned mixes when they're done right (=usually simple arrangements).

And if done well they also tend to still sound good in mono!

[lucey]

Originally Posted by Adam Dempsey

And if done well they also tend to still sound good in mono!

thumbsup

[dcollins]

Originally Posted by macc

This forum is brilliant. Despite wading into the middle of your low-key running battle, thank you both.

It's not a battle. I just never seem to agree with Bob, so when I do, I buy a lottery ticket.


DC

[jdg]

you can't win if you dont play

[masteringhouse]

Originally Posted by dcollins

The single most important thing is to get a comfortable translatable frequency balance in your room.

thumbsup

Of the acoustical experts that I've had in my room (last one being Roger Quested setting up subs) I have yet to see one do a LEDR test. After a few frequency and phase measurements they mostly seem to simply sit and listen to a CD of their choosing occasionally moving around or getting up to use the restroom.

[lucey]

Originally Posted by masteringhouse

After a few frequency and phase measurements they mostly seem to simply sit and listen to a CD of their choosing occasionally moving around or getting up to use the restroom.

I don't know of anything useful as a ref cd with a variety of tracks and a person who knows that ref.

[Jerry Tubb]

Originally Posted by dcollins

I'm buying a lottery ticket.


DC

Now thaaat's funny!

I got the joke ...for once.

(no offense to Bob either)

JT

[masteringhouse]

I'm sure that Bob has a thicker skin than allowing a difference of opinion as being taken as a personal attack. It's certainly not my intent to become part of a katfight. One of the main purposes of forums is to discuss differences of opinions in order to get closer to the truth, however elusive or perceived. If these differences can be expressed with a sense of humor that makes the discussions all the more entertaining.

FWIW Bob given my second semester of teaching a mastering course I've helped to sell around 50 copies of your book and will continue to do so. A book that in large part was built from content on these forums. While there are points in your book that I may not agree with for example, the requirements of a mastering DAW, and I would like to see a different ordering of the chapters, it remains the best book written on the subject of mastering.

Let the Point/Counterpoint continue (to paraphrase an old Saturday Night Live skit) "You ignorant slutz".

[bob katz]

Originally Posted by masteringhouse

thumbsup

Of the acoustical experts that I've had in my room (last one being Roger Quested setting up subs) I have yet to see one do a LEDR test. After a few frequency and phase measurements they mostly seem to simply sit and listen to a CD of their choosing occasionally moving around or getting up to use the restroom.

The LEDR test is no substitute for good time-domain measurement techniques, but it is the only subjective/objective listening test that gives the ears the opportunity to hear and objectively judge time-domain reflection problems. I haven't run the LEDR in my room in years, but that's because I do make time-domain measurements and judge the reflection-free zone objectively as well as subjectively. But if you do not have good time-domain measurements of the room, the LEDR is a great tool. Remember that this thread started off as advice to mixing and mastering engineers on how to judge the left-right balance in their room. If the room is not properly treated, or if the speaker crossovers are screwy, or any other number of potential acoustic anomalies----the ol' "pink noise is in the middle" test will not be enough help. And the LEDR test is the first (and probably only) LISTENING test for acoustic reflections and anomalies that the mix engineer can turn to.

[masteringhouse]

Bob, how much of the LEDR test is affected by the design of the monitors?

I suppose that it can serve as a rough test for the overall performance of the combination of room/monitors, but I don't know that I would depend on this test alone in order to make decisions on room treatments without checking on a few different monitors. One could be barking up the wrong tree.

[PatrikT]

Originally Posted by bob katz

The LEDR test is no substitute for good time-domain measurement techniques, but it is the only subjective/objective listening test that gives the ears the opportunity to hear and objectively judge time-domain reflection problems.

When playing the LEDR, that is.


Best Regards
Patrik

[Silver Sonya]

Originally Posted by lucey

The Hacienda record 'Loud is the Night' that I did last year was all 60s panning

Cool!

- c

[bob katz]

Originally Posted by masteringhouse

Bob, how much of the LEDR test is affected by the design of the monitors?

That's an excellent question. In theory, if a loudspeaker system doesn't pass the LEDR test fully, then it must be "defective" in some way and not as good as one which does pass it. But obviously there are degrees of perfection. In my mind a system which does not fully pass the LEDR test will probably audibly not have as good a depth response, as wide and even a soundstage or as clear or well-defined definition or what audiophiles call "resolution".

For example, there's the "beyond" test. Some loudspeakers have very poor "beyond" response. The beyond signal should extend from about a foot or more to the left of the left loudspeaker to about a foot or more to the right of the right loudspeaker. First of all, if it's not symmetrical, I would question the accuracy and evenness of frequency response between the two loudspeakers. If it does not extend very far beyond the loudspeaker, question reflections from side walls. But if you think the room is properly treated and the beyond signal is only so-so, then I would say the speaker's dispersion is not optimal, perhaps it's too wide at least at certain frequencies. Or it has significant diffraction or beaming. How many subjective tests can you name which actually tell you something about these objective parameters which normally you would have to measure to verify the performance?

That's why I scoff at people in this thread who say, "I've never used the LEDR, I can't see its use". It's only when the speaker or room does NOT pass the LEDR test that you need to at least find out WHY, even if you feel the speaker is still good, it's important for you to know its weaknesses. All other things being equal (and they never seem to be) I've found speakers that pass the LEDR test to image better, wider, and deeper. And this translates to ease of use and less listener fatigue. Scoff all you will, LEDR is a tool that's very helpful for those who want to make a quick listening evaluation and not go through the measurements.

I suppose that it can serve as a rough test for the overall performance of the combination of room/monitors, but I don't know that I would depend on this test alone in order to make decisions on room treatments without checking on a few different monitors. One could be barking up the wrong tree.

The question that came up by the doubters is, "Can't I make just as good a judgment about the imaging performance of my loudspeakers just by listening to music?" Roger Quested didn't need to play this test.

My answer is, if "Music playback will not tell you about imaging as precisely, as quickly, or with as good resolution as the LEDR"!

Roger Quested is an experienced listener and measurer. He probably has a regular set of recordings which he uses to test playbacks and knows how they react in many other rooms. Same with me, I haven't needed to use the LEDR in my own room in a long time. But if I went into a strange room and didn't have time to measure, pop goes the LEDR.

Back to YOU and YOU and YOU. If you're not Roger Quested and you have NOT yet measured your room, then LEDR will be very good for you. However, if you've already done high-quality measurements of the time-domain response of the room (including the amplitude and time delays of the earliest reflections), the energy-transfer curve of the loudspeakers/environment, the averaged frequency response curves over a specified averaging time (I use 100 ms), the phase response, horizontal and vertical dispersion, distortion and overload points, noise floor, Schroeder curves, etc., then you probably don't need to bother with the LEDR tests.

The more familiar you become with the LEDR test, you'll see how it can be a very quick way of verifying speaker/monitor imaging response. Try it first on a pair of bookshelf-mounted monitors and then really cringe. Can you tell when someone walks past your loudspeakers when you have your eyes closed? It's the same thing with the LEDR, you listen and you make a judgment.

[macc]

So *cough cough*

Howzabout telling us a little more how to interpret it?

Please and thank you.

[masteringhouse]

Thanks for the reply Bob, well said.

Roger also has an advantage in knowing how his speakers should sound, so the room was the only variable in this particular case. This was not a typical scenario. FWIW he did mention that he had forgotten how good UD1s sound as was thinking about possibly re-making them. I hope that he does.

[dcollins]

Originally Posted by masteringhouse

FWIW he did mention that he had forgotten how good UD1s sound as was thinking about possibly re-making them. I hope that he does.

It's funny you mention that, as he also commented of how good the H-108's sounded in my old A&M room. Which they did. I miss those mini's sometimes, but better not to have too many choices.

It's actually easy to get good monitor imaging, and besides mastering should maintain the original mix image rather than try to "enhance" which should be for the mix.


DC

[jayfrigo]

Originally Posted by dcollins

It's actually easy to get good monitor imaging, and besides mastering should maintain the original mix image rather than try to "enhance" which should be for the mix.

DC

Next you'll be telling me you don't use multi-band compression on every master, there's no easter bunny, and magazine ads don't always tell the truth!

[dcollins]

Originally Posted by jayfrigo

Next you'll be telling me you don't use multi-band compression on every master, there's no easter bunny, and you can't trust magazine ads!

At the rate you're deleting posts, you may never know what gems I might share here.


DC

[jayfrigo]

Originally Posted by dcollins

At the rate you're deleting posts, you may never know what gems I might share here.

DC

Only one, as it fell inside a string of others that needed thinning. It's back now.

[bob katz]

Originally Posted by macc

So *cough cough*

Howzabout telling us a little more how to interpret it?

Please and thank you.

Let's start with the "beyond signal". The sound should evenly move from beyond the left speaker (about 1 foot if the loudspeakers are in the midfield) to beyond the right. If it doesn't extend that far, look to the side walls for possible reflections. Look to the loudspeaker crossver for phase anomalies. Look to the loudspeaker design itself for diffraction issues or dispersion issues. Bad symptoms would be if the sound goes up and towards you or up and away from you. It should go straight up.

The "Up" signal, in a well-designed loudspeaker, should move straight up in the air, some report as much as 3-4 feet above the speaker. if not, look for ceiling reflection issues, loudspeaker crossover or phasing issues. Some people report that loudspeakers in an MTM configuration like the Dunlavys and Lipinskis don't do the up signal very well. I NEVER played the LEDR through my Lipinskis and now that I'm selling that pair I guess I'll never know the truth. As to whether success with the "up" signal translates to better imaging, it's the most controversial signal. But I think you can pat yourself on the back if you get a good "up signal", it does mean the loudspeaker is linear in that domain, whatever that means.

The OVER signal, or the rainbow. Should be a very nice rainbow shape, would be ideal. Obviously, look for obstructions located between the loudspeakers as being the cause of a bad OVER signal. Or diffraction or dispersion issues. Out of phase tweeters could cause this as well.

LEDR is an interesting and entertaining test at the least. Experienced listeners probably don't need it, but it could be a wakeup call, tell you if some driver or crossover element is starting to go out of tolerance.