Interesting post, Spridle!

So the blue line is what the processor generated?

Also, it corrects for speaker performance and room interactions and creates a flat curve in the mids and highs which make a huge difference in vocals, guitars, cymbals, imaging, soundstage, sparkle, etc.

Something to listen for, the fundamentals of mid to upper-mid bass notes reside in the 100-300 Hz range, so this curve might leave them sounding reduced in level. Of course, that’ll be of little consequence for home theater.

If you want to take it to the next level, I have previously used Rane PE-17 parametric EQs (bought on EBay) for my mains with no audibly detectable coloration, noise or distortion added. This is a good way to go. I even found a way to precisely set the filters on the Ranes using REW. See a prior post of mine for the technique.

I’ve regularly been sending people to that thread when they inquire about the benefits full-range equalizing. :T

Regards,
Wayne

 

So the blue line is what the processor generated?

On the REW graph, the blue line is the target curve I created with points to generally follow the red response line that I measured with REW. The red response line was from measurements taken after the processor does its thing and is an average of 5 positions. When I measured with REW then looked at the graphs, I was surprised to see the size of the hump and the narrow range it covers compared to the house curve I was using before which was basically a 4db boost house curve. I was also surprised that the bass does not sound "louder" than before, but rather tighter and more precise. On the graph, the gain at 30-50Hz is a whopping 11dB.

Something to listen for, the fundamentals of mid to upper-mid bass notes reside in the 100-300 Hz range, so this curve might leave them sounding reduced in level. Of course, that’ll be of little consequence for home theater.

I primarily listen to music, so accuracy and realism are most important to me. The sound is very balanced across the spectrum and sounds very much like live music, especially when cranked up. The bass is tight, punchy, and smooth -- much more so than before. The Basia bass line is particularly impressive. Believe it or not, I have been tweak-free for about 2 weeks and haven't heard anything that has caused me to get up and try a new setting.

I’ve regularly been sending people to that thread when they inquire about the benefits full-range equalizing.

It would be interesting to hear about the results with the Ranes and what target curves are used. I'll search the thread to see if anything has been posted.

 

On the REW graph, the blue line is the target curve I created with points to generally follow the red response line that I measured with REW. The red response line was from measurements taken after the processor does its thing and is an average of 5 positions.

Ah. Well then, I can't help but notice that the red-line response the processor generated has the house curve shelving at ~30 Hz, a figure I mentioned in my house curve article.

Are you still using the Ranes, or did the processor have EQ to replace them?

Regards,
Wayne

 

I have removed the Ranes. I have the processor room correction set to work up to 15K Hz.

 

This looks like the RoomPerfect curve. I am using a similar (slightly different) target for my DEQ2496.

The RoomPerfect people claim that it is based on the principle that we are used to hearing room gain when we are in a room. I think this is a weak rationale.

However, much more important to me, is that most final mastering of recordings is done in a studio, which will have room gain. The mastering EQ is therefore based on sounding right in a room with room gain. In these (dare I say normal) cases, it would result in too little bass in our rooms if we EQ flat in the bass.

You would be making a mistake to say your search for a target curve is over. Some recordings are mastered with headphones (shudder). And some are so-called 'direct to disc', which can mean what it says, but more generically means recordings that are effectively unmastered, e.g. some of the Water Lily Acoustics recordings of live classical work captured direct to two microphones and not further equalised, or recordings like Marcus Miller's Ozell Tapes that are mastered direct from the mixing desk. Such 'unmastered' recordings will sound too bass heavy (I can vouch for it) because your target curve needs to be flat in the bass for them.

So you need to have a few target curves on hand. But the one you are using is a better default setting than flat (eech) or X-curve (misapplied in the home living room), which I have used over the years.

 

I think that most mixing studios are checked out by Dolby Digital and they mix the master using an X-Curve. When they go back an recode for the format DVD, Blu-Ray, Digital Copy :scratchhead:, they are mixing for an enviornment that is entended to be flat, unless they expect you to do the curve yourself. How to know which is right can be impossible. I wish that I knew a way of extracting these metatags or downloading them that are intended for the THX Media Director. Better yet they should just make it all public so we can know how the mixes were done. That is probobly asking too much but it would be nice. Even then we would have to rely on the people releasing the media to tell us, and they already don't as it is most of the time.

 

I agree it would be sooo pleasing if people in the industry (the big players) would join the internet discussions and make interested audiophiles aware of the room acoustic they would recommend for the recordings. Then we could aim for that. At the moment it feels like groping in the dark!

 

Your not taking into account how close one is to the speaker. The speaker will sound harsh at times depending on the mix unless it is factored into the remix and encoding proccess to disc. I hear it sometimes but other times it is not as bad. It is dependent on what the film maker wants to do mostly. If they are listening to speakers that are not going to sound harsh while they mix, it isn't going to sound that way. Here is a quote directly from the THX website about their version of Re-Eq.

THX Re-EQ is a compensation technology taking soundtracks that are mixed for large cinemas, where speakers are placed farther away from you, and re-establishes the accurate tonal balance for your close range home theater speakers. Without THX Re-EQ, higher frequencies sound excessively “edgy” or “bright.” With THX Re-EQ, the movie soundtrack is true to the original immersive cinematic experience.

Example: The THX Certified DVD classic action film Aliens is loaded with audio and visual effects. When watching this film with THX Re-EQ activated in your THX Certified receiver or pre-amplifier, the technology adjusts and reproduces the high frequencies to play at the appropriate audio level in your home. Otherwise these frequencies would sound overbearing and distracting.

My pre/pro calls this theater mode.

 

Your not taking into account how close one is to the speaker.

Sure I am (or did, in Dec 07):
http://www.hometheatershack.com/for...om/forums/rew-forum/8178-house-curve-some-advice-its-use-non-use.html#post68712

The speaker will sound harsh at times depending on the mix unless it is factored into the remix and encoding proccess to disc. I hear it sometimes but other times it is not as bad. It is dependent on what the film maker wants to do mostly. If they are listening to speakers that are not going to sound harsh while they mix, it isn't going to sound that way.

No argument.

I still reckon the X-curve for a small (home) room is zero.:hide:

In saying the X-curve is zero, I am not saying there is no need for EQ in the home. I am only saying that the reasons EQ is needed are not founded in the X-curve rationale. Therefore the shape of EQ that is needed in the home is not based on the X-curve's shape.

 

I'm sorry. I confussed a statement I made earlier in this thread. Most movies that are mixed for the cemema will benifit with RE-EQ. The majority of material we may be expossed to however such as games or broadcast will not benifit from RE-EQ.

 

I've stumbled to this thread the other day and decided to give this target curve a try. I've recently bought a Marantz SR8001 and real happy on the SQ. Anyway, this receiver has the MultEQ Audyssey calibration built in. I was trying to tweak the manually calibration to my best to get it closer to this target curve. I'm really like how it sounds especially on the vocals, but it seems to lack on the bass department though. I like how the Audyssey setting sounds more with the bass. So I combined this target curve with the lower freqs Audyssey target curve and got what I want. It sounds great with music and movie now. I really like how it sounds now, even GF give a thumb up on the newer EQ system.

Here is my curve.

15 15
20 15
30 15
50 11
70 7.5
100 2.5
150 1
200 0
2000 0
8000 -1
10000 -2
13000 -4
16000 -10
20000 -20

My measurements with Target Curve

Before and After graph.
Green = Audyssey OFF; Yellow = Audyssey ON; Blue = EQ FLAT; Red = Preset - manual calibration (volume was 1 db higher by accident)

Thanks Spridle and everyone else for the target curve.

Al,

 

hi wackii and all

I'm just new to the thread but I thought that you all might find this interesting and particularly wackii as the "Real X Curve" described in this linked document pretty much matched your target curve.

(Seeing I haven't done five posts you'll have to do the link yourselves)
siamize.vpscustomer.com/sound/the_mythical_x_curve.pdf



It also puts simply what a lot of the main points of what has been said in the thread which I've summaries below

1. Large/small rooms need a different house curves .... it gives some recommendations which I think are pretty much in keeping with comments/recommendations previously posted.

2. How the "official" X curve is some what dated and was based on how things sounded on old equipment (not that I was around back then) but how now with newer systems extreme frequencies are reproducable (ie. below 100 Hz & above 8k) and hence it suggests the "Real X Curve".

3. The cabin effect with the possible modification of the "Real X Curve" for boomy rooms along with Point 1 recommendations.


My take on a house curve is that it is a standard so that when you take your CD/DVD from one house/room to the next it will sound the same. The electronics (including speakers), room shape, occupants & furnishings are all part of the "house".

 

Tested out the Real X Curve in the previous posts document
(ie. the_mythical_x_curve.pdf) in a 200 seat auditorium ... way to much highs is my only comment . It might have sounded OK in a small home theater but not a room 15mx26m with a 4.8m ceiling. I modified it a bit. Kept the same under 2kHz but then used the standard X Curve over 2k with the recommendationed modifications for a 200 seat auditorium as the std X Curve is for a 500 seat room. Hence, the House Curve was as below although I shelved the really low sub bass. I was very happy with how music sounded through the system.


20 6
80 6
100 2
110 0
2000 0
10000 -6.0
20000 -11.5


On a side note, I was a bit confused how after I EQed the house for the "Real X Curve" yesterday and then came back today to apply move the roll off at the top from 8k to 2k, I first check to see if if the EQ was still OK from yesterday and it wasn't even though all the setting were the same. The house wasn't responding the same way and needed reEQing even though all the EQ setting were exactly the same. I know that because I wrote them down just to make sure no little fingers had changed them during the day or at anytime in the future.

 

On a side note, I was a bit confused how after I EQed the house for the "Real X Curve" yesterday and then came back today... The house wasn't responding the same way...

Not at all unusual. While the measurement platform is stable enough (REW for example), the transducers involved - the speakers and elements in the microphones - are not. Their physical (and consequently electrical) properties are altered with changes in temperature, humidity, etc. This is why response readings taken at one session may not “look” the same as those taken at a later date.

I know that because I wrote them down just to make sure no little fingers had changed them during the day or at anytime in the future.

You might want to get a security cover for the equalizer...

Regards,
Wayne

 

You might want to get a security cover for the equalizer...

Yea have thought of that but it's a digital one and I've stored the settings to the presets. It's more so that I'm not the only operator of the system.

 

Well suprise suprise. When I checked the house response today after setting it up to my modified Real-X-Curve, the house response was different. Yesterday I was cooler and much more humid (rained on and off from about 3am through to 2pmish on and off) whereas today was relatively warmer and clear skies.


Anyway how much different ... see the picture at ...
siamize.vpscustomer.com/Sound/100414%20-%20PCCC%20eq.jpg

The blue line is the target house curve. This has been subtracted off the true response of the GREEN (yesterday's response after EQing) and the YELLOW (today's response without changing yesterday's EQing) so that the response shown should looks flat. This makes it easier when EQing to know how much to cut/boost especially when your target house curve is sloping and varied.

I thought I'd post it just to show how much variation can happen from one day to the next even when the setting on the electronics are all the same.

 

It's more so that I'm not the only operator of the system.

Matters not, the equalizer should be “set and forget.” The various “operators” shouldn’t be messing with it.

I thought I'd post it just to show how much variation can happen from one day to the next even when the setting on the electronics are all the same.

I must say, a “new day, new reading” deviation of -4 / +8 dB is pretty shocking.

Is the green line actual measured response, after equalization?

Regards,
Wayne

 

Matters not, the equalizer should be “set and forget.” The various “operators” shouldn’t be messing with it.

Yes I know but you know sound engineers ... always want to tweak things a little.

I must say, a “new day, new reading” deviation of -4 / +8 dB is pretty shocking.

I was very suprised myself. That's what why I posted the reponses to see if others had tested their systems with the same setting on different days. I'll test it again today too as the weather is not as extreme as such ... today looks like it'll be clear skies and much the same temp as yesterday.

Is the green line actual measured response, after equalization?

Yes but with the inverse of the target curve applied. That way you are chasing a "flat response" on the screen. The sub has a separate volume control, the crossover is about 110Hz, and the sub only has a 4 band parametric EQ. Whereas the main front of house has the 4band parametric EQ + 32band EQ. I would have liked to have got that lower area (40-160Hz) a little flatter but I run out of time / was running really late for my next appointment by that time.

Also I've been EQing to a 20Hz to 20kHz to 20Hz logrithmic frequency sweep/cycle. The sweep duration from 20Hz to 20kHz is 20secs. I find this much more replicable than using pink noise - also a bit easier to listen too.

 

Well it seems that the atmospheric conditions may play a larger role than most expect. Today the house reponse was much the same as yesterday's response with the same EQ settings unlike the day before when it was much more humid and a little cooler.

http://siamize.vpscustomer.com/Sound/100415 - PCCC eq.jpg

 

Not really. I guess it has something to do with TrueRTA, which I've never used and know nothing about. Every RTA I've ever used, you just EQ'd to get response to match the Target curve (which included a house curve), such as you see in the graph below (which I lifted from Post # 1 of this thread). So the graph you get is an actual response reading. I wouldn't find any other kind particularly useful.

Blue Trace - Target
Red Trace - Measured Response w/ EQ
​

Regards,
Wayne

 

Not really. I guess it has something to do with TrueRTA, which I've never used and know nothing about. Every RTA I've ever used, you just EQ'd to get response to match the Target curve (which included a house curve) ...... I wouldn't find any other kind particularly useful.

Yea I guess I thought that way when I first saw the feature. It's not really a feature for determining what your house response is but rather a tool to help when shaping the house response to a target (particularly EQing). I've played around with quite a few RTA's and never come across it before either. However, now that I have it, I find it quite useful when shaping the house response.

I guess that it's only over the last 2 weeks that I've researched an objective way of EQing to a standard rather than just what sound's good. The digital 32 Band eq that we use has an autoeq (ie. it play's pink noise and set up the eq to a target but there was no guidance as to what that target should be and as we all know flat doesn't normally sound good - particularly in large rooms) so I was really looking for somekind of standard. That's how I've ended up here. Now I think I've found that standard this tool help apply that standard easily.

Giving a little more history ... I've done some recording over the last 6 months with my new Zoom R16 and have had trouble mixing the recordings so that they sound similar in various sound environments - particulary setting the bass level with respect to the rest of the mix. So this has all kind of resulted from that and live mixing.

 

Well after a bit of research on how temperature, air pressure & relative humidity affects sound I put together this spreadsheet.

http://siamize.vpscustomer.com/Sound/Atmospheric Sound Attenuation.xls

It seems that only frequencies over 2kHz are significantly affected. As my main differences were in the 500-1000Hz range I think that difference may also be to do with the fact that the natural frequency of the room (ie one with the highest R60 value) is about 600Hz.

As my measurements were taken at exactly the same place, modal interference/construction changes can be very significant from reflected signals with even the slightest atmospheric changes. See http://www.rane.com/pdf/ranenotes/Enviromental Effects on the Speed of Sound.pdf

So my next readings with be from a variety of locations in the room as obviously in my room (15x26x4.5m) frequencies of this range are reverberated quite a bit and thus interference factor can really mess with EQing with even a slight change in atmospheric conditions.

 

It seems that only frequencies over 2kHz are significantly affected. As my main differences were in the 500-1000Hz range I think that difference may also be to do with the fact that the natural frequency of the room (ie one with the highest R60 value) is about 600Hz.

Don't forget that changes in temperature and humidity will have an effect on the transducers involved - i.e., the speakers and measurement mics. Expansion and contraction and all that. That will potentially have some effect on measurements across the entire frequency spectrum, even if it's not enough to be audible.

Regards,
Wayne

 

effect on the transducers involved - i.e., the speakers and measurement mics.

Yes, most definately. I did think of that but just forgot as I was writing the last post. I think that the temperature & humidity would have an effect quite and effect on the stiffness of the membranes of the transducers and thus change their response characteristics.

I guess the main point of this is to find out what changes the sound and by how much. I mean there's no point in setting the house response flat to within +/- 0.5 dB and think that you can leave it that way when a change in the temperature or humidity can put +/- 8 dB dents and humps in it like it seems to have done.

So far it seems that you should EQ each session but I'll see what this weeks results come up with by taking more than one measurement in the room but rather throughout the room.

 

The comment above concerning the X curve are confusing to me.

Referring to movies only, I thought that the intent was that a theater EQ should be setup to match the X curve and the film or digital track was EQ'ed to be the inverse of the X curve. If done correctly The result would be that the theater would then provide the intended flat response. [The logic being the same as the old Dolby D cassette EQ or the LP RIAA EQ, that is, to try to achieve a low noise and flat response given the weaknesses of the mediums involved at the time (film, tape and vinyl).]

Since the target of home theater speaker setup is presumably intended to provide a flat response the EQ for a BluRay disk does not apply the "inverse X curve" and the result is again to try to achieve a flat response.

Is this off base? Do I need to try to wade through this again?

[The house curve is another matter and that is where I am struggling.]

 

Welcome to the Forum, John!

Referring to movies only, I thought that the intent was that a theater EQ should be setup to match the X curve and the film or digital track was EQ'ed to be the inverse of the X curve.

No, the X curve was – is – what’s used for both theaters and sound stages. In other words, both the theaters as well as the playback medium (the movies) adhere to the same standard.

Click the “Tech Articles” link in my signature and you’ll find an article about the X curve and home theater. In it you’ll find a couple of other links about the X curve.

Since the target of home theater speaker setup is presumably intended to provide a flat response the EQ for a BluRay disk does not apply the "inverse X curve" and the result is again to try to achieve a flat response.

Unlike a theater, the goal in a home theater is flat response. However, for many people flat response sounds “thin” or “tinny,” sorely lacking in bass response. So a rise in the lower frequencies is enacted to make response sound natural.

Regards,
Wayne

 

Thanks!
I got the wrong idea or confused it with something else i guess. I will read through the info you noted.

 

Well I run a set of test throughout the building this morning and WOW. While I realise that my initial testing location that I was using wasn't the best I really didn't think that it would vary so much through the room/seating area. I knew that some areas had more bass response but yea. Now I have to workout where to attack next.

Note that for the following response charts the inverse of the Target House Curve has been applied.

Here's the responses at 12 various seating locations (the reasonable flat purple line at about 1dB) was at the previous test location (location where the EQ was set).
http://siamize.vpscustomer.com/sound/100420 - PCCC seating locations.jpg

In this response, I've averaged all 12 the seating locations. Also included is the response in the middle of the seating area (probably the most ideal test location if a single test location was to be chosen) as well as the response when seated at the sound desk. My first comment is that as the sound desk the highs don't response as well as in the rest of the room leading to obvious mixing difficulties.
http://siamize.vpscustomer.com/sound/100420 - PCCC overall.jpg


As you can see the practicalities of having a nice even sound/flat response seems somewhat of an idealistic concept considering I have't even included the wash from the stage foldbacks yet!

My next step will be to EQ it for the centre of the seating location and then then test the various seating locations again. The this centre locations seems somewhat like that average response (ie. areas that need cutting/boosting) (although I use that term "somewhat" very loosely).

 

OK analysised the average data for the 12 seating locations and then estimated what EQ changes needed to be made, made them and then tested all locations again. I'm pretty happy with the results actually except for the 1kHz band which I've boosted by 5dB but haven't tested again. Overall the sound is much more natural and less crisp which is to be expected but does sound much more even. Although I am thinking of moving that 2k attenuation point back up to 8kHz to see how it sounds.

Here's the overall responses (with inverse house curve applied).
http://siamize.vpscustomer.com/sound/100421 - PCCC overall.jpg

At each of the 12 location (with inverse house curve applied).
http://siamize.vpscustomer.com/sound/100421 - PCCC seating locations.jpg

 

Well I took my advise and applied it and am very happy with the results. From the last tests (100421 which

were done for a Modern X Curve but applying attenuation at 2kHz) I estimated what EQ changes needed to be

made at the top end to change it to the Modern X Curve (ie. Attenuated at 8kHz). I'm pleased to say that I

prefer the sound - much more clarity. For some reason there is now a dip at 250Hz even though I didn't

change anything in that area but that's not that bad for removing some mud some times. I think that my

"mistake" of attenuation at 2kHz was due to only selecting one not really ideal spot for my original testing.

Admittedly it takes much longer and more effort to measure at 12 locations plus a few other non-seating

locations, but it is definately worth it if you want a real result for your room - particularly if you have a

rather large room where there are many different seating locations.

There are the results and I've also overlayed the House Curves as the inverse of the House Curves have been

applied to the responses.

http://siamize.vpscustomer.com/sound/100422 - PCCC overall.jpg

http://siamize.vpscustomer.com/sound/100422 - PCCC seating locations.jpg

 

I really don't get it. Today (Tuesday) I went and tested the room again with all the same settings as Friday (See http://siamize.vpscustomer.com/sound/100423 - PCCC seating locations.jpg for Friday's Responses) and the response was just way different on a few particular bands (250, 800, 1000 & 2500 Hz) by up to 7dB. (For a comparison see http://siamize.vpscustomer.com/sound/100427 - PCCC seating locations.jpg).


I thought that I had nailed it to an interference/nodal thing and that the issue would be removed by testing in approximately the same locations (ie. not down to the same inch but rather to the nearest foot or so) and by testing in 12 locations instead of 1 and taking an average.

However it seems to be something else. Any ideas?

 

I'd say study your 12 locations for both days and see if you can determine which location(s) is skewing the measurement. Then figure out what changed at those locations between the two days. Near an AC vent that was blowing one day and not the other? Some nearby object in the room relocated, removed or added? Some kind of noise bleeding into the room from outside the auditorium?

Regards,
Wayne

 

I'd say study your 12 locations for both days and see if you can determine which location(s) is skewing the measurement. Then figure out what changed at those locations between the two days. Near an AC vent that was blowing one day and not the other? Some nearby object in the room relocated, removed or added? Some kind of noise bleeding into the room from outside the auditorium?

It's not any particular one locations skewing as I can normally tell if it is going to skew after about 3 results because it happens at all locations.

All AirCon was off during all testing, and furnature was basically all the same nothing noticable has been moved or changed.

The volume that I'm testing at is very much above any background noise an the room is closed during testing as well.

I was talking to a guy from the city theatre and he said that it sounded like something playing up in the amps.

I've tested it twice this week and it hasn't tried to skew the results. Very strange.