EQ vs. Room Treatments

[Guiria]

After searching a few threads here I still have an unanswered question...Can you get the same effects from EQ'ing speakers as you can with room treatments.

Do these new receivers that come with EQ functions (such as Denon with Audyssey MultiEQ) basically replace the need for room treatments?

My initial thoughts are no. Room treatments will still provide improved midrange response and imaging, probably among other things.

What say ye?

 

[WmAx]

After searching a few threads here I still have an unanswered question...Can you get the same effects from EQ'ing speakers as you can with room treatments.

Do these new receivers that come with EQ functions (such as Denon with Audyssey MultiEQ) basically replace the need for room treatments?

My initial thoughts are no. Room treatments will still provide improved midrange response and imaging, probably among other things.

What say ye?

The best option is to use both of these things together. I can never recommend just one. But obviously, if you need the most inexpensive option, EQ is the first thing to purchase. Insert a Behringer Feedback Destroyer EQ between your pre-out and sub-woofer amplifier in order to correct peaks in LF response, and also to apply a preferred roll off point/rate. For mid and high frequency correction, room treatments are by far the preferred option. EQ should be used for customized tonal response adjustment in the mid and high frequency bands, not room error compensation. If you go to a DSP device that has convolution, then you can correct mid band room problems to an extent. But the best option again is room treatments.

-Chris

 

[no. 5]

My initial thoughts are no. Room treatments will still provide improved midrange response and imaging, probably among other things.

Yeah, you cannot use an EQ to remove wall reflections.

 

[Glenn Kuras]

There is no way you can EQ a null and EQ will doing nothing for ringing within the room. Which is just as important if not more important then having a flat response curve.

Here is a typical non treated room.

There is just no way EQ could be begin to solve this problem. Even if it could it would only be for that one small area of the room. Move a foot to the left/right and the whole thing now changes again.

I will say for areas below 40 Hz, EQ can help to bring down a peak here and there though. Over all if you treat the room you will be much happier with the sound.

Glenn

 

[Guiria]

So EQ can effectively solve low bass frequency humps while room treatments are effective at all frequencies specifically higher (non-LFE) frequencies.

doh...gotta go back to work.

 

[bpape]

EQ is a bandaid for frequency response issues caused by suboptimal speaker, sub, and seating placement which is sometimes required in real rooms. It cannot do anything to deal with decay times, ringing bass making dialog difficult to understand, smearing of imaging based on reflections off the side wall, nulls coming off the back wall (or any other null that is room position related), etc.

As WmAx said, usually a combination is the best solution. If you can only swing $100, either DIY some treatments or live with the limitations of a cheap EQ. It'll help some but not a lot. Other than that, treating your room is considered by many to be the biggest bang for the buck improvement you can make to your overall listening experience.

Bryan

 

[D.R. Payne]

I've been experimenting with RoomEQ Wizard and Acoustisoft R+D for several months. This is a big topic and I don't claim to be an expert. As far as I can tell, EQ can only alter your perception of the semi-anechoic frequency response, the sound that travels directly from the radiator to your ear. EQ cannnot affect sound energy in the time domain. The time it takes sound to decay below the noise floor and the confusion of direct sound mixed with sound that has reflected off of one or more surfaces can be affected by absorption and diffusion. If you're willing to invest some time and $$ in acoustic measurement software and equipment and learn how to read the measurements you can get the best sound out of your room with purchased or homade acoustic treatments. I am still working on this for my room.

My gear:
Acoustisoft R+D
external usb Sound Blaster card with RCA inputs
Behringer omnidirectional studio microphone
simple Behringer mixing board (to serve as a pre-amp for the mic)
50 XLR cable to keep the computer far away from the measurements
microphone boom to gaurantee stability of the mic and repeatability of the measurements

Happy hunting...

 

[Sheep]

EQ is a bandaid for frequency response issues caused by suboptimal speaker, sub, and seating placement which is sometimes required in real rooms. It cannot do anything to deal with decay times, ringing bass making dialog difficult to understand, smearing of imaging based on reflections off the side wall, nulls coming off the back wall (or any other null that is room position related), etc.

As WmAx said, usually a combination is the best solution. If you can only swing $100, either DIY some treatments or live with the limitations of a cheap EQ. It'll help some but not a lot. Other than that, treating your room is considered by many to be the biggest bang for the buck improvement you can make to your overall listening experience.

Bryan

You can use an EQ to tailor a flat speakers response to your own personal preference as well.

SheepStar

 

[Audiacc]

Insert a Behringer Feedback Destroyer EQ ....

I would stay away from this one if I could. I bought it
and discovered feedback destroyer does not work at 96kHz sampling rate (feature does not respond, no LED comes up). Not a single word of explanation about this in the manual. Audio analyzer part on the 1024 model is a joke.
Limiter and compressor do not work (no audible difference)
If I was to buy again I would check ebay for some dbx EQ instead of this.

I admit it I bought it for live sound reinforcement and not home theater setup. Maybe it is good enough for home theater...

 

[Savant]

This topic has been covered extensively in this forum, et al. I have said this before and I will repeat it here: While EQ cannot address time domain problems (e.g., "ringing"), there are Digital Room Correction (DRC) systems that can. I'm not advocating their use - at least not exclusively. I only point out that they exist and they have been shown to work in some applications.

As others have pointed out (including above), the best approach to address LF problems is room treatments. When all practical avenues in that regard have been exhausted, DRC (or even good EQ - but not in the time domain) can help address particularly stubborn problems in the lowest octave or two.

Of course, Gene has made the (not incorrect) point that addressing the frequency (amplitude) domain inherently addressed the time domain. Assuming I'm not butchering his thoughts too badly, in simple terms, reducing the amplitude of a mode inherently reduces its "ringing" on the back end. While true, this sometimes isn't enough since it's often the "ringing" that's the problem, regardless of the amplitude.

My advice is always to get the best most practical room treatments you can, then - as deemed necessary - look into "tweaking" with something like DRC or EQ.

 

[gene]

Do these new receivers that come with EQ functions (such as Denon with Audyssey MultiEQ) basically replace the need for room treatments?

Room EQ doesn't negate the need for passive room treatments. It compliments it.

My advice for getting better bass goes in order of importance:
1. multiple subs properly placed: anyone serious about getting good bass and still using 1 sub to do it is seriously missing out
2. some passive treatments where necessary but they tend to be big and bulky to be effective for low frequencies
3. room EQ provided it has enough resolution (at least 1/12th octave) and you have the proper measurement tools and know how to interpret the results

That being said, I have almost no passive room treatments in my room below 150Hz and I have achieved +-5dB bass response from 15Hz to 200Hz for all 5 of my listening seats using 4 subs and Audyssey Pro MultEQ. Audyssey is one of the few room correction devices that deals with amplitude and phase which does help time domain response.

Note: It took me hours of measuring, tweaking, and customization of the EQ curves to achieve what I have done so I don't recommend it for a beginner. Had I implemented more low frequency passive treatments, my life would have probably been a little easier.

 

[peerlesser]

If the budget is limited, even two subs with proper placement and fully automatic 8033 DSP for time-domain DRC will give rather good result.

If the problem is like this for example:

8033 Anti-Mode DSP will correct it automatically to something like this.

Below that level, decay time are pretty much the same even with 8033. But for its price <300$ there are no other options, unless you want to set up the EQ yourself with computer.

I fear that the mentioned 1/12oct resolution would not be enough for subwoofer room-EQ, as the center frequencies are can be more than 2Hz away from the real value. They must not miss more than 0.5Hz for that parameter. This is where SMS-1 fails. It also has poor autocalibration, and the response it draws is unrealistic as its smoothed with 1/3oct.

The best result is always with both DSP and treatment. For subwoofer range, an accurate auto-DSP is usually easier option to get audible results. Only thing I have seen to work there is 8033 Anti-Mode and the most highest class receivers with Audysseys.

Room treatment works well in high frequencies and makes global improvement. For low frequencies new DSPs works better, but the results are not as global.

 

[bpape]

Thank you for illustrating my point. You show an example where you've dealt with peaks. It's done nothing for the nulls. As for treatment being for high frequencies only, sorry, not buying that. THIN treatments, yes. However, treatments can certainly deal with the 70Hz up range that this curve still shows as problematic - and can do so for all seats in the room depending on the cause of the nulls.

Bryan

 

[gene]

I fear that the mentioned 1/12oct resolution would not be enough for subwoofer room-EQ, as the center frequencies are can be more than 2Hz away from the real value.

That is why I said "at least" 1/12th octave. And I agree the display of the SMS-1 is virtually useless as we indicated in our review. I always use LMS and a 1/12th octave FFT to verify results.

Thank you for illustrating my point. You show an example where you've dealt with peaks. It's done nothing for the nulls. As for treatment being for high frequencies only, sorry, not buying that. THIN treatments, yes. However, treatments can certainly deal with the 70Hz up range that this curve still shows as problematic - and can do so for all seats in the room depending on the cause of the nulls.

Nulls can be dealt with to a very minor extent with systems like Audyssey. Ultimately using multi subs properly placed helps considerable and if the null is only a few Hz wide, its usually not audible.

 

[fmw]

Perhaps the easiest way to explain it is that room treatments change the reflectivity of the room. EQ changes the frequency response of what comes from the speakers. They do different things in different ways and don't replace each other.

 

[bpape]

You're correct. They don't replace each other - they compliment each other. In most cases, the best solution is in order:

- Proper placement for best response and avoiding nulls/peaks
- Treatment to deal with decay time, kill reflections, and minimize response abberations for the whole room as much as possible
- EQ the peaks that remain that are common to all seats. If one seat has a peak and one has a null at the same frequency, you can't fix it for both.

As for narrow nulls not being heard, it depends on how deep they are and where they fall. If you happen to have one that falls on a fundamental of a bass string or a drum whack, it can be quite noticible.

It also depends WHERE in the range it is. A 5Hz wide null from 30-35 would be much more noticible than a 5Hz wide null from say 100-105.

Bryan

 

[WmAx]

I would stay away from this one if I could. I bought it
and discovered feedback destroyer does not work at 96kHz sampling rate (feature does not respond, no LED comes up). Not a single word of explanation about this in the manual. Audio analyzer part on the 1024 model is a joke.
Limiter and compressor do not work (no audible difference)
If I was to buy again I would check ebay for some dbx EQ instead of this.

I admit it I bought it for live sound reinforcement and not home theater setup. Maybe it is good enough for home theater...

I have not used the FBQ units, but I have used other Behringer equipment with no issue. The FBQ is a popular model for bass peak reduction in HT circles, and many people seem to use use this unit without issue. As for the audio analyzer that is built in - I would not bother. There is superb freeware called Room EQ Wizard that is a full blown analyzer that can directly connect and configure the FBQ units. All you need is a reasonably accurate microphone to connect to your computer. As for the limiter and compressor having no audible difference, and combined with other issues you are having - it seems likely that you either do not know how to use the device properly, or it was a defective unit. There are forums that specialize in helping to use these FBQ models along with the freeware. Check www.hometheatershack.com for such a specialist forum called the 'BFD Forum' - they can probably help you resolve your issue(s).

-Chris

 

[peerlesser]

Thank you for illustrating my point. You show an example where you've dealt with peaks. It's done nothing for the nulls. As for treatment being for high frequencies only, sorry, not buying that. THIN treatments, yes. However, treatments can certainly deal with the 70Hz up range that this curve still shows as problematic - and can do so for all seats in the room depending on the cause of the nulls.

Bryan

Most people use subwoofer below 60Hz or 80Hz. As in this case, the range down from 70Hz is the problem. Still agreed EQ wouldn't help if there were nulls, unless it can address more than one source independenty. Placement and multiple sources are great for working out the nulls. However, using treatment there would be most efficient using custom designed bass-traps or such pinpoint accurate absorbers. This requires measurements and design with computer setup and is therefore not for everyone. Neither is stuffing half of the reflective area of the room with thick treatments, which eventually would blindly yield to the result.

For example absorbing ringing 18dB peak requires 64 times the loss-ratio, which is not possible unless every square meter on the room surface delivers 0.98 Sabines of absorption. What treatment material has a factor of 0.98 from 16 to 60Hz? Just for comparison: 2.5 feet thick mineralwool has a factor of about 0.98, but few would have the option to cover the walls with it.

As the consensus is, both treatment and modern DSPs are required, or the outcome is less optimal.

 

[bpape]

Agreed on both being needed. I'll also agree that from about 35-40hz down an EQ is a better option due to sheer size and issues with tuned absorbers.

On the other, I'll still have to disagree. One doesn't need to cover every square inch - one simply needs to identify WHERE the offending reflections are that are causing the cancellations and address that area. A very common one is the center of the rear wall. A properly designed broadband bass absorber that is maybe 6" thick can cut that null in half in terms of intensity while at the same time addressing the decay time in the room across the entire spectrum - and doing so pretty effectively from about 50hz up.

Corners are often used because they're at the end of 2 or 3 of the room's dimensions so you get multiple benefits in multiple dimensions from a minimal amount of coverage without overdamping things. They're not the only thing that needs to be done in a room though.

Another common problem is SBIR which sometimes cannot be dealt with via placement due to sheer usability of the space, screen size selected is too large pushing speakers right against a wall, etc. In those cases, appropriate treatment directly beside/behind the speakers can help to minimize the effect and if done correctly, can create an inverse curve in the area where the sub and mains overlap (which they do since xovers are not brick walls) and use that to help minimize frequency response issues. Again, these also serve double duty in bringing down the broadband decay time in the room.

What's important to remember is that ALL peaks and nulls which are room induced are the result of reflection. From the stand point of bass response, ones that come back and mix in phase cause a peak. Those that come back out of phase cause a null. Damping the reflection will not elminiate the issue but can minimize the extent to which they build on each other or cancel each other. Using an EQ will increase or reduce the intensity of both by the same amount - thereby leaving the same relative change in response.

Using purely tuned absorbers ignores much of the spectrum. Yes - if I have a frequency response peak/null at say 60hz, I can build a trap for that which is relatively narrow and will address the frequency abberations. But, it also leads to the mistaken assumption that the bottom end has now been 'fixed' which it has not. We've only dealt with the frequency aspect and not the time aspect. The decay times of the rest of the bass range (outside the 60hz that we 'fixed') is still going to be 1-2 seconds to decay 60db. Even if you subscribe to the 30db (RT30 vs RT60) method, they can still be quite long enough to cause masking of detail.

Ringing bass, long decay times, etc. are probably the biggest cause of things outside the bass range like dialog intelligibility issues, etc.

Good discussion.

Bryan

 

[Savant]

Bryan,

Using purely tuned absorbers ignores much of the spectrum. Yes - if I have a frequency response peak/null at say 60hz, I can build a trap for that which is relatively narrow and will address the frequency abberations. But, it also leads to the mistaken assumption that the bottom end has now been 'fixed' which it has not. We've only dealt with the frequency aspect and not the time aspect. The decay times of the rest of the bass range (outside the 60hz that we 'fixed') is still going to be 1-2 seconds to decay 60db. Even if you subscribe to the 30db (RT30 vs RT60) method, they can still be quite long enough to cause masking of detail.

I'm enjoying this thread - it's about the most civil discussion on treatments vs. EQ I think I've seen!

Re the above paragraph: I was a little confused. Whether an LF absorber is tuned or not does not change how it functions. Any absorber addresses both amplitude and decay. The way you wrote the above made it appear that an absorber only addresses amplitude. which is not the case. In fact, the opposite is actually more likely at low frequencies; the decay will typically be affected the most. It may not be affected enough, which I think was your point. But, relatively speaking, absorbers address decay "more" than amplitude. (If such a comparison can even be made, physically speaking... )