Improving nearfield perfomance with calibration systems & EQ?

[TechnoTroll101]

Hi there,

I'm considering to buy the Wiim Amp to improve the performance of my desktop speakers (Heco Aurora 300 + Teufel Subwoofer).
The listening distance is only about 0.7m, so it's definitely a nearfield use. What I found out is that my speakers sound significantly better when the distance is at least 1m. As I'm listening to music when sitting in front of the computer, I wonder if the nearfield sound quality can be improved with a Wiim Amp. Is it something a calibration system can improve with EQ settings or do the physical characteristics of the speakers simply not allow for more?

 

[staticV3]

Driver summing is an attribute of physical loudspeaker design and cannot be compensated for using PEQ.

A KEF LS50 will always perform better nearfield than a Wharfedale Linton.

Nonetheless, PEQ may well help you achieve better sound in the nearfield, albeit not by improving driver summing.

 

[Mort]

Is there a rule of thumb / heuristic for minimum distance for optimal driver summing?

 

[TechnoTroll101]

I'm not sure what you mean by "driver summing" - I don't have any hiss or summing noises. What I meant by "sounding significantly better" is that especially the bass is better when taking a step back.

 

[Sokel]

I'm not sure what you mean by "driver summing" - I don't have any hiss or summing noises. What I meant by "sounding significantly better" is that especially the bass is better when taking a step back.

Think of it simply.
What happens if you stick your ear 2 cm from the woofer?
What if you do the same 2 cm from the tweeter?

As going further from the speakers there's an optimal distance where the response of the drivers is summing, blending into a smooth whole, depending the speaker of course.

You can find a guide here:

Correct Monitors - Genelec.com

www.genelec.com

Example:

Read the red area.

 

[anotherhobby]

Yes, DSP & room correction software can definitely improve nearfield performance. I have Revel M105s on my desk at a distance of 1M, along with 4 subs running as stereo pairs, and I run Dirac Live for room correction. Below are the uncorrected and corrected room measurements from the MLP. The blue line is the target curve I have set in Dirac. The sound quality improvement with Dirac is huge. Before upgrading to Dirac, I used REW's auto EQ and set the PEQ values manually in my miniDSP Flex, and the results were also pretty decent, although Dirac is much better.

 

[AnalogSteph]

Is there a rule of thumb / heuristic for minimum distance for optimal driver summing?

Sort of. It's going to depend on driver spacing and crossover frequency. This is why explicit nearfield designs tend to have small waveguides and driver spacing as close as possible. So e.g. KRK Rokits or Yamaha HS series monitors would be designed for shorter distances than ADAMs, JBLs and Kalis. And 3-way designs with mid-tweeter coaxes have an obvious advantage.

My personal rule of thumb for 2-ways would be about 0.1 m for every inch of nominal woofer diameter (roughly in accordance with Genelec's recommendations above), a bit more when driver spacing is not optimized for nearfield. Hiss levels need to be considered as a factor as well.

 

[Blumlein 88]

Even before I knew about critical distances, all my setups tended to end up at about the critical distance. Not sure what that says, but I suppose I wanted a little more of the room vs mostly direct from the speaker. Maybe I just needed better speakers.

 

[DVDdoug]

It could be a number of things in addition to the woofer & tweeter angles & distance... Just the angle to your ears can make a difference if you don't re-aim them when you move.

I like the sound of a bigger room (ideally bigger than I have at home) and as you move closer to the speakers you obviously get proportionally less reflected "room sound". If you are doing production and "monitoring" less room sound can be a good thing in an untreated room.

Also there is some cancelation around 2kHz because the off-center location of your ears (your left & right ears aren't in the same spot) and the timing-distance difference between the left & right speakers... At some frequencies the left & right waves arrive out-of-phase and cancel. The distance difference depends on the angle so your distance from the speakers affects the severity and the frequency(s) of the effect.

 

[TechnoTroll101]

Yes, DSP & room correction software can definitely improve nearfield performance.

The overall sound seems to be much better, but in my specific case it's mostly the bass response. Do you think the calibration system of the Wiim Amp could change the nearfield performance of the Heco Aurora 300? If that's the case, it would be awesome!

 

[Keith_W]

A bit of misinformation that has been given because you failed to explain exactly what you meant when you said that the sound is better at 1m than at 0.7m in your initial post. For a small bookshelf speaker like that, 0.7m is more than enough for the drivers to integrate properly. The dimensions are 195mm x 357mm x 315mm according to this, so 0.7m is about twice the largest dimension of the baffle distance from the loudspeaker. I assure you that the drivers will be integrated. Here is a very quick drawing I did with Sketchup to prove my point:

I assumed a 60deg arc from each driver. In reality the bass driver will be much wider than that, so this drawing under-represents driver integration. You can see that the two drivers integrate at 119mm, and by 0.7m you have a cone about 671mm diameter.

Bass is a different story. The wavelength of low frequencies is very long - a 100Hz freq has a wavelength of 3.43m, and 20Hz is 17.2m. Take a moment to think about how long that is, it is likely longer than your listening room. Furthermore, low frequencies form standing waves in ALL rooms without exception - this means there are peaks and nulls. The pattern of these peaks and nulls has to do with room dimensions and where the observer is placed. Even small differences in listening position can change the pattern dramatically, as you can hear with your own ears.

Here is an example I pulled up from my collection of measurements of my woofer at 30cm (green), 50cm (blue), and 100cm (brown). These measurements were taken with furniture cleared away. If you have furniture near your speakers (e.g. desk) the graph will be much more wavy.

So if you are hearing less bass at 0.7m, it is possible that you are sitting in a null. This disappears when you move slightly further away.

To answer your question - can your Wiim improve things? The answer is MAYBE, but only to an extent. DSP can get very complex, and the Wiim offers the most basic and most coarse DSP available - it is nothing more than a parametric EQ. More sophisticated DSP can manipulate the timing as well as amplitude, but even then the ability to deal with nulls is limited. DSP is an endless rabbit hole, some of us go nuts trying to refine it.

My advice is to take some measurements at 0.7m and 1m to see what is going on. It may be possible to move your sub to improve the situation. Without a mic, you are flying blind.

 

[TechnoTroll101]

[...]

So if you are hearing less bass at 0.7m, it is possible that you are sitting in a null. This disappears when you move slightly further away.

To answer your question - can your Wiim improve things? The answer is MAYBE, but only to an extent. DSP can get very complex, and the Wiim offers the most basic and most coarse DSP available - it is nothing more than a parametric EQ. More sophisticated DSP can manipulate the timing as well as amplitude, but even then the ability to deal with nulls is limited. DSP is an endless rabbit hole, some of us go nuts trying to refine it.

My advice is to take some measurements at 0.7m and 1m to see what is going on. It may be possible to move your sub to improve the situation. Without a mic, you are flying blind.

Thank you for your detailed explanation! I just tested the Kali LP-UNF in combination with my subwoofer and came to the conclusion that the Heco Aurora 300 still sound better, so I will definitely keep them and return the Kalis.

I'd like to create a measurement - I have an Audyssey XT32 microphone from my AVR (Denon X3500H) I could use. But which free software would you recommend me to use? I only use PEACE APO EQ on windows to give my speakers a 2db boost for 100Hz.

 

[Keith_W]

This is your microphone?

Ummmmmmm, I suppose you could use it but you won't be getting accurate results. If all you are doing is comparing bass at 0.7m vs 1m then it should tell you what the relative difference is. But for an absolute measurement, I wouldn't trust it.

The usual recommendation on ASR is a USB microphone, e.g. UMIK-1, UMIK-2, or Dayton UMM-6. Or an XLR microphone like the Behringer ECM8000, iSemCon EMX-7150, or Earthworks M23/M30. If you get an XLR microphone, you will also need an interface with 48V Phantom Power, like a Focusrite 2i2 or even fancier such as Motu Ultralite, RME Babyface, etc. You will also need to budget for a proper microphone tripod (and not that rubbish mini tripod that comes with the UMIK-1/2). It is worthwhile spending extra to buy a calibrated microphone.

For measurement software, everybody uses REW. It's free. Take a look at my REW help thread.

 

[staticV3]

But which free software would you recommend me to use?

Room EQ Wizard.

If you want to include your Peace EQ in the measurement, open REW's Generator, export a Pink noise track as .WAV (Mono, 1-2min), then play it back using any software of your choice.

To measure the in-room frequency response, open REW's RTA window and use the Moving Microphone Method:

The moving microphone method (MMM) for Dummies using REW

After getting a couple of weird results on my first MMM measurements, I went searching around the forums & YouTube for what went wrong. To save others from gathering various bits and pieces of info from a dozen sources, I decided to publish this quick write-up here. You can use it as a rough...

www.audiosciencereview.com

https://www.ohl.to/audio/downloads/MMM-moving-mic-measurement.pdf

You can also use the default REW measurement sweep, either directly in REW or by again exporting the sweep as .WAV if you want to include the Peace EQ.

This sweep will collect distortion data, phase response, decay (RT60), impulse response etc, but frequency response measured with it won't be very useful.