Tact question

Can any Tact users explain how far the system goes in terms of correcting low frequency issues?

Regarding room modes, I assume it just finds the room modes and attenuates them according to their relative strength at the listening position (comparable with adding appropriate low-freq absorption to the space).

I am more curious though how it handles the "troughs" in low-freq response. These troughs can either occur when the listener is located at a room mode "null point" or due to boundary interference effects at low frequencies (the interference effects can result in deep "notches" that may be around the 80-100Hz region depending on woofer placement relative to room surfaces). I think the term low-frequency "suck-out" best describes these effects

Does the Tact system try to compensate for these "suck-outs" as I always though this is not good practice as some can be very deep indeed (>10dB).

 

With Tact you set a target curve. Thats what you want the response to look like in the end. It then works out the amount of EQ needed (+ or -) to get the response to look like that. If you don't want it to add loads of EQ in a deep suck-out you have to draw the target curve so that it has a suck-out there, then when it comes to EQ the signal it will not add so much. I found the whole system a complete arse about face way of doing things. I would much rather they show you the response of your system as it is and let you tell it how much EQ to apply where and then show you how the response looks with that EQ.

the new TacT system seems a lot better thought out in as much as it takes an average measurement from a few places around the listening room, so it is less likely to over optimise the response for one spot.

It is not the same as adding absorption to a room though as absorption changes the speed at which sound decays in the room. EQ can't. Its a VERY big difference and an equally important one in my experience.

If I were looking for room EQ I’d rather have the Behringer or a DEQX and make the room measurements on a computer.

 

The Tact configuration system does sound a bit strange. I would like to hear it in action as it seems to polarize listeners.

Good point.

What have you found the differences to be subjectively between active EQ and room absorption? Thinking about it logically I would expect:-
i) with LF absorption treatments - very strong initial room response then a fairly rapid decay.
ii) with active EQ - wouldn't get the initial strong room response but a much slower decay.

 

Mostly room treatments for the bass make things far tighter and less boomy while with EQ the notes that are boomy just get turned down.

So if you had a big resonance at 60Hz with room treatments it would be much cleaner, tighter and less boomy but still sound stronger at that point. With EQ it would be just as messy sounding as it always was but equally strong sounding over all the bass. The best thing to do is use both.

It also depends what the room is like. I have found in larger rooms the room treatments give a lot more improvement than EQ but in medium / small rooms they offer about an equally important improvement, but in different areas.

 

Nice one dude, well put.

Will have to read up on those Behringer/DEQX posts when I get a chance.

 

So what is the best and/or cheapest way to get an accurate graph showing the frequency responce of your system at the listening position ?

 

the deq2496 plus ecm8000 mic will do that for you..cost £165 for me

 

For an accurate graph you want to use a computer software like EFT (about £80) as the Behringer will only show it on its little orange display. If you are really interested in the bass area any program that does frequency analysis and plays white noise will be pretty accurate though (CoolEdit / Audition, Audacity?).

 

Or you could use a Velodyne SMS-1 or one of their DD range with that module built in.

 

Prevention is better than cure...

One way of looking at room modes is that they are resonances excited by injecting power (at the right frequency) into the room. What happens is that the room absorbs the power more slowly compared to other frequencies. So, to prevent the problem, you inject less power and the "decay" falls into line with other frequencies.

The alternative is to use room treatment, but these typically are substantial physical objects.

The nice thing about room modes is that (unlike other acoustic problems) they are minimum phase and using simple frequency repsonse equalization gets the correct time domain behaviour.

Your subjective experience is what it is, but it does not mesh with the physical reality of the situation.

 

do you mean nodes ...not modes ?

nodes and anti nodes are created by constructive and destructive interference paterns. Ie imagine the wake of two boats of equal size and speed heading in the same dirrection. This is analogus to your speakers for a single frequency, then set in box were the side walls create reflections.

 

My speakers are capable of 20hz -2db, and differentiating E flat and F , though at times I could do with better power handling, one or two of those DD12 subs could be interesting though it wouldnt really help me get a better idea of my room speaker interface.

Can the Behringer measure and adjust Left and Right channels individualy ? and is it quite easy to hook up to a PC ?

 

Are you saying using active EQ at low frequencies is equivalent to adding LF absorption?

Isn't it not a case that adding LF absorption will inherently steepen the rate of decay for a given room mode. On the other hand, reducing the energy input (through active EQ) does nothing to change the rate of decay, it just starts the whole decay process at a lower initial value. Subjectively, I think there would be audible differences between the two methods for treating room modes (although I've never been able to compare the two myself).

Room modes are actually caused by reflected energy interfering with itself (unlike other reflection issues such as comb filtering which is reflected energy interacting with the direct energy). If the room surfaces offer minimal LF absorption, such as heavy masonry, then the rate of decay can be relatively long. Active EQ does not change that, it only reduces the initial energy input into the room.

Not dissing anyone, just trying to fully understand the pro's and con's of each method.

 

Andy,

this is the most effective bass correcting solution I ever tried, full stop. But it has it's limitations.

You can easily eliminate all peaks in the listening position, however high they are. You can lower bass responce and shape it any way you wish. Well, almost.
One thing you can not do - you can not compensate most dips in the bass. TacT generally advice NOT to raise dips as it may easily damage the drivers. My experience shows that at lower comfortable/night levels robust speakers like ATC 35 easily withstand dips up to 6 or even 10 dB. But you would raise the volume at your peril. Then again there are different sorts of dips. Most bass dips are the product of cansellation of standing waves. Here it does not matter how high you raise the level - these waves cansel each other. So leave deep dips as they are. On a bright side - narrow dips as horrible as they look on graph are not too much audible.
If you position your speakers the way that they have narrow dips at slightly different freq., you will need to leave these dips for both speakers when corecting the freq. graph. So both speakers will have both dips instead of one each. So, TacT's claim that you can put speakers wherever you want and then correct the freq. response is not quite justified imho. What is good - speakers work best when close to the wall, and I mean really close. And it does not matter how big and loose is the bass. Actually the bigger the better - it will be easier to correct. That's why bass traps are not welcome here.
I can tell you that bass becomes unbelievably better, it is dynamics higher up the freq. range that I do not quite like with TacT.
Regarding the new "advanced" system - I have my doubts, although I have never tried it. It allows for a wider listener area, but you can not avoid laws of physics - it's other pinpoint narrow area or a more approximated wider one. The old system imho is more "manual" and less "automatic", and you will need to spend a good month learning how to change gear - trying, measuring, re-measuring, moving speakers, drawing lots of freq graphs on your computer, before you will be able to achieve a really great satisfying results. Simple improvements are imminent - it takes just half an hour, but there are many nitty-gritty things that you will have to learn. On the other hand - it is fun and it is very educational, to know how even tiny corrections in some areas of freq. range can change the sound.
I have sold my ATCs, and my current speakers are omni-directional, and basically not suited for room correction. So I am thinking of selling my TacT. But I am glad that I have spent some time with it. I think every hi-fi enthusiast should.

 

I may be wrong, and others may care to chip in, but the new Lyngdorf RoomPerfect system does work for all types of speaker, unlike the older TacT systems. It also works in 1/12 octave bands, which allows for more specific corrections than other 1/3 octave systems.

 

This is correct, and you can say that theoretically the dynamics of a digitally EQed bass are screwed because it is mostly room reflections anyway. But in reality, subjectively bass down to 20 Hz ( well down to 10Hz indeed if speakers allow) becomes much better in all aspects, firmer, controlled, clearer, with better texture etc. and you would need to build a pretty elaborate and complex bass traps systems to match that, reducing your room by a fifth at least, which is crazy, so I would not worry too much about it.

 

Thanks for all that info. Shame I don't live near any of you Tact owners as I'd be interested to hear it in action.

I think the room modes issue is a big one in the UK. Compared to my native Aust, there is much more use of masonry internal wall constructions offering very little LF absorption. When you excite a room mode under those conditions, they come in strong and loud, smearing any adjacent frequencies in their wake!

 

Most people solve this problem here by filling their rooms with a lot of rubbish.

 

Andy you are right that EQ can not change the RATE of decay, it can only start it at a lower level. The effect should not be underestimated, it is at least as important if not more than the inital frequency responce.

I like Nomoretweaks way of doing things but I find bass traps are indeed 'welcome here'! I like to corner load my speakers and EQ to get a flat initial frequency response and correct phase but then I use bass traps to get a much quicker decay rate so the bass is far more punchy, dynamic and articulate. Otherwise it still hangs around like it always did after a note.

EQ or room treatments are not doing the same things so one is not better than the other. If you have a single peak in the bass the a bit of EQ will surely knock it on the head far easier than room treatments but if you want to improve the overall quality of the bass then room treatments will do more. Use both and you are even further ahead. You may notice even on my website I recommend the use of digital room correction in conjunction with treatments.

I think the reason A LOT of people find digital correction 'sucks the music away' is because it alters the frequency response but leaves the decay slope the same and that throws your minds ear off because it is not natural, the decay slope tells it there should be more level at that frequency and there is not - hence the 'disjointed music' comment you get a lot. Just my pet theory but it makes sense to me.

 

It's easy to forget that you have to consider the response in the both the frequency and time domains.

I've been lucky enough to hear a couple of well treated studios and the LF performance from largish monitors (typically 15" woofers) is truely staggering when done correctly.