Target Curves

RUR

WBF Founding Member
Apr 21, 2010
647
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SoCal
#1
The good news for TacT owners is that target FR curves are selectable and highly adjustable. Armed with a laptop, we can insert/move/delete filters to our hearts content in search of “the perfect curve”. Adjustment may be made in increments as small as 0.8Hz and 0.1dB. Furthermore, multiple curves are supported and selectable with the push of a remote button, so we can design and use multiple curves as individual mastering and/or the mood suits. Not enough bass on a particular recording? Pick a curve with more bass emphasis. Want more bloom in the midrange? Pick a curve with a touch of midrange push.

Unfortunately, finding the ideal curve isn’t necessarily easy. Sure, the TacT comes with a variety of target curves to try and, if one of them is the perfect fit, you’re done. In my case, and probably in many/most others, that won’t be true and one is left to tweak a supplied curve or to develop one from scratch until nirvana is achieved. Depending upon your temperament, you may find this (generally extended) exercise to be fun – or frustrating, so I thought I’d start this thread with what I believe to be basic principles, a couple of enjoyable curves, and an invitation for fellow users to share their own curves and experiences.

Last year, Harman International conducted a series of preference tests for Room Correction (RC) products. The results were published in an AES paper, but the basics may be found on Sean Olive’s blog here. Of importance to this discussion is that Harman found that “the most preferred room corrections produced the smoothest, most extended amplitude responses measured at the primary listening seat” and that “preferred room corrections have a target response that has a smooth downward slope with increasing frequency”. The former probably requires no explanation while the latter is attributed to the belief that listeners prefer a certain amount of room gain because the recordings were mixed with similar room gain. The most preferred response is the topmost of six shown here on slide 24 of the associated Powerpoint briefing. Note the smooth downward slope and that FR falls roughly 10dB from 20-20KHz.

In a recent thread describing his own experiences with DSP/RC, Marty posted that his target curve approximates a curve resulting from Bruel and Kjaer’s research into room response preferences, presented in a 1974 AES paper*. B&K’s curve looks like this:



And shows a slight 2.5-3dB “hump” (relatively flat) from 20-200Hz, falling off evenly from 200Hz-20KHz and ending at ~-3dB. I wanted to try Marty’s curve and created a TacT target curve approximation, which looks like this



And for which the *.cor file may be found attached as BandK 0dB for WBF 6-9-10.COR.

In my system/room and for my absolutely subjective tastes, I find both the Harman and B&K curves to be a bit rich in upper bass, masking vocals and important spatial detail. Basically, I use a straight slope from 20-20KHz, though much shallower than Harman’s.



The associated TacT *.cor file may be found attached as kensexample for WBF.COR

As with any TacT curve, measured response will vary from the curve actually input and desired, so a bit of filter tweaking must be done in order to achieve the curves shown. Finally, and as mentioned at the outset, I have the various TacT presets set up with variations of "my" desired curve, adding more/less bass, mids or highs so that I can select a curve which sounds satisfying for a particular genre or to “fix” perceived mastering issues. All entirely subjective, of course!


* That paper cannot be directly linked, but may be found here in B&K's library by searching on "Relevant Loudspeaker Tests".
 

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audioguy

WBF Founding Member
Apr 21, 2010
2,731
6
38
Near Atlanta, GA but not too near!
#4
RUR: To demonstrate my lack of technological prowess, how were you able to get a JPG or PDF file of your target curve to attach to your post? Once I figure that out, I will be able to post them.

The article that was done in the Harmon paper did shows some of the curves and preference. I'm not looking at them as I type this, but IIRC, the one most preferred by listeners was fairly close to your straight line drop from 20 to 20K by about 10db over that entire range which is slightly more of a drop than your target.

The problem with all of this is that as volume changes, so does our perception of bass. The TacT 2.2XP has a feature called dynamic volume but I have yet to try it. Have you?

And you are correct that much of this is preference. Earlier today I was listening to the Chinese Drums cut on one of the Burmeister Demo CD's and the more bass in the target curve the better it sounded particularly since I was driving 8 15 inch drivers in my subs--and since there were no vocals to screw up, so much the better.

Clearly the TacT is a tweakers paradise (or an OCD's worst nightmare!!)
 
Apr 3, 2010
16,022
0
0
Seattle, WA
#5
If the image is on a server some place and you have a URL for it, then you can show it inline by putting
around it. If you try to host it here, it unfortunately shows up as thumbnails. RUR's posts link to external sites and hence, show up inline. Is this what you were asking?
 
Apr 3, 2010
16,022
0
0
Seattle, WA
#7
At the risk of answering the wrong question again :), you can use Print-screen function to grab any window on your PC, then take it into mspaint, crop and then save. Of course, RUR is going to chime in probably and say that TacT software can actually save those screens and make me look like a fool for second time tonight :D.
 

RUR

WBF Founding Member
Apr 21, 2010
647
0
0
SoCal
#8
At the risk of answering the wrong question again :), you can use Print-screen function to grab any window on your PC, then take it into mspaint, crop and then save. Of course, RUR is going to chime in probably and say that TacT software can actually save those screens and make me look like a fool for second time tonight :D.
That's exactly how I do it, Amir - printscreen to Paint. Crop the image with Photoshop and voila!
 

RUR

WBF Founding Member
Apr 21, 2010
647
0
0
SoCal
#9
The problem with all of this is that as volume changes, so does our perception of bass. The TacT 2.2XP has a feature called dynamic volume but I have yet to try it. Have you?
I sure have, though it's seldom used as my reference volume doesn't change much. What I haven't done is to customize the actual DRC curves i.e. the stock Fletcher-Munson curves are still being used.
 

audioguy

WBF Founding Member
Apr 21, 2010
2,731
6
38
Near Atlanta, GA but not too near!
#11
When is flat not exactly flat?

On another thread, I showed some charts of the Audyssey Sub EQ product on my four subs. After correction, it generated (as it is supposed to do) a ruler f;at response (as measured and corrected from 15 different positions.

The before and after SubEQ response is shown below:



One would think (but apparently one would be very incorrect) that if you ran a TAcT test signal through the filter created in the SubEQ that something representing a flat line should be the result.

Check this out:


That is a huge drop from 80hz to 10hz. I need to run REW or (soon) XTZ through the Audyssey SubEQ to see what IT thinks flat looks like.

Wierd!!
 

audioguy

WBF Founding Member
Apr 21, 2010
2,731
6
38
Near Atlanta, GA but not too near!
#12
I have been running my TacT using the two subs on the left of the room as the left sub and the two on the right as the right sub (even though I'm crossing over at 65hz so there really is no left or right). In doing it this way, I was taking advantage of the smoothed response of the front and rear subs combined but was NOT adjusting for the difference in distance between the front and rear sub. Running it through the Audyssey addresses that issue.

Only one small problem: It sounds much cleaner the original way.

The issue for me is if I keep it this way I have to reconnect my subs when switching from 2 channel to HT.

I tried to find a switching product that would allow 4 in and 4 out so that I could automatically connect any of the sub inputs (2 from the Onkyo or 2 from the TacT) into any of the 4 sub outputs. QSC has oe but it has an MSRP of $3700 so I will pass on that solution.
 

RUR

WBF Founding Member
Apr 21, 2010
647
0
0
SoCal
#13
When is flat not exactly flat?

On another thread, I showed some charts of the Audyssey Sub EQ product on my four subs. After correction, it generated (as it is supposed to do) a ruler f;at response (as measured and corrected from 15 different positions.

The before and after SubEQ response is shown below:
Chuck, what are the scales, especially what's the lowest frequency shown? Can't be 0Hz.

One would think (but apparently one would be very incorrect) that if you ran a TAcT test signal through the filter created in the SubEQ that something representing a flat line should be the result.
*snip*
That is a huge drop from 80hz to 10hz. I need to run REW or (soon) XTZ through the Audyssey SubEQ to see what IT thinks flat looks like.
An REW measurement would be very helpful. Don't forget you're comparing a 15 measurement, averaged plot (Audyssey) with a single measurement plot (TacT). Also, we need the scale answer from above. Also also, does Audyssey show 1/3 octave smoothing? 1/6 octave? Something else? (I'm not an Audyssey expert, by a long shot.....) Basically, we need to find out if we're comparing apples and ducks before we figure out anything else.

I have been running my TacT using the two subs on the left of the room as the left sub and the two on the right as the right sub (even though I'm crossing over at 65hz so there really is no left or right). In doing it this way, I was taking advantage of the smoothed response of the front and rear subs combined but was NOT adjusting for the difference in distance between the front and rear sub. Running it through the Audyssey addresses that issue.

Only one small problem: It sounds much cleaner the original way.
OK, slowly for the slow guy... Running correction thru Audyssey Bass(?) adjusts the distance for all four subs? If so, are you allowing the TacT to measure and set sub distance? If so, try turning that off, so that TacT isn't trying to correct the corrected distances.

What do you mean when you say "the original way"?
 

audioguy

WBF Founding Member
Apr 21, 2010
2,731
6
38
Near Atlanta, GA but not too near!
#14
There are no scales on the Audyssey curves but one could assume (by counting vertical scale lines), that the low end is 20hz. Audyssey won't comment on exactly how the curve is plotted. I'm not really concerend about how smooth the Audyssey curve is only the general slope relative to the general slope of the Tact Curve. Because the Tact sees the negative slope, it is creating a filter with a large boost at the bottom end. The chart below show the uncorrected response the TacT sees when I have things connected the "original way" excluding the Audyssey SubEQ.

The "original way" was the left front and rear sub were assigned to the TacT left sub output and the right front and rear sub were assigned to the right TacT sub out.

The Audyssey SubEQ has the time delays of the rear subs taken into consideration but no delay with respect to any other speakers.

The attached chart is the rigth two subs, no correction and no delay of the rear subs.
 

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RUR

WBF Founding Member
Apr 21, 2010
647
0
0
SoCal
#16
Looks similar to a number of available curves in the TacT database. If I can't find a match with an existing .cor file, I'll create one and post it here for TacT owners to try.

and welcome to the forum! :)
 
Jul 1, 2010
8,713
0
0
#18
This TACT piece in question...is it a digital preamp? I feel like the Joker, in Batman..."Where does he get all those wonderful toys?'

I want an iTunes plug in with a much more granular graphic eq and a parametric as well. I know, degradation from bit perfect and all of that...don't hear it, but I do hear a 2 db lift at 80 hz to give more body to low volume listening. This toy you boys have looks like a wonderful tool.

P
 

RUR

WBF Founding Member
Apr 21, 2010
647
0
0
SoCal
#19
This TACT piece in question...is it a digital preamp? I feel like the Joker, in Batman..."Where does he get all those wonderful toys?'

I want an iTunes plug in with a much more granular graphic eq and a parametric as well. I know, degradation from bit perfect and all of that...don't hear it, but I do hear a 2 db lift at 80 hz to give more body to low volume listening. This toy you boys have looks like a wonderful tool.

P
Tim, the bit of gear most/all of us are using is, indeed, a digital preamp - the TacT 2.2XP. It provides room correction for two mains and two sub-woofer channels, and configurable active crossover between mains/subs. The same RC is also available in other TacT gear, including (as an option) their digital amplifiers.

Parametric EQ is also provided, as well as "Dynamic Room Correction" using configurable Fletcher Munson curves. It is a wonderful tool. Their website is here, and I'd be happy to answer any specific questions you may have.
 

RUR

WBF Founding Member
Apr 21, 2010
647
0
0
SoCal
#20
Tim, a couple of other observations now that I'm properly caffeinated... The TacT will provide adjustments as small as 0.8Hz and 0.1 dB. How much more granular are you seeking? I think most folks would be surprised by how small a change in level is noticeable. 2dB is actually very easy to hear and I'd swear I often hear adjustments of 0.1-0.2dB.

(((acourate)))® is a Win XP solution, and supports "Intel Macs with XP".
 

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