Article: Calibrating Desktop Speakers using Focus Fidelity Filter Designer

[mitchco]

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[mitchco]

 

10 hours ago, JR_Audio said:

Hi Mitch. Ah, great you are introducing a new (at least for me new) room correction solution. I will read through it and will give it a spin. If you have a regular room, you can do so much with room correction to get good sound, much more than with most of the “tweaks” that are used to improve the sound. Thanks for writing.

 

Hi Juergen, good to hear from you. Totally agreed - room correction, properly applied, can make an outstanding difference in sound quality, especially for the price! 

Kind regards,

Mitch

[mitchco]

9 hours ago, Confused said:

@mitchco - A fascinating article.  I have to admit that the very concept of "room correction" for desktop speakers had never occurred to me, but it seems obvious now it is out there!  Thanks for writing this.

 

You mention at the start of the article that correction for a desk top set up is "highly demanding", and the ultimate conclusion is that the Focus Fidelity software did a good job.  Can it be extrapolated from this you would recommend Focus Fidelity for a conventional (not desktop) hifi set up?

 

I have spent quite a bit of time with REW, and have obtained reasonable results, but I always feel it would need a LOT more time and effort to get everything "just so".   Is Focus Fidelity a better option than REW, in terms of results obtained versus time invested? 

 

I am planning to make some changes to my room, which will include some room treatments etc., so it would be great to have some (reasonably) user friendly software to assist with periodic updates.  I know this stuff will never be easy, it does take effort to move along the learning curve, but any software that might help just a little has to be of interest.

 

 

Hi @Confused Yes, Focus Fidelity will work fine for any setup.

 

While I use REW daily for acoustic measurements, it is not marketed or sold as "room correction" software. While one can use it for taming some peaks in a room, it is not at the same resolution as "purpose built" room correction software with it's 65,536 tap length FIR filter. Parametric eq's or PEQ's don't have any excessphase correction capabilities, so it is missing half of the "transfer function" for proper room correction. At low frequencies this translates into the difference between smooth bass versus smooth and clear bass using Focus Fidelity. Once you hear the clarity of the bass, it is hard to go back to anything else.

 

Kind regards,

Mitch

[mitchco]

@jrobbins50 Yes, AL will work for desktops as well. @Crom The process of designing a custom room correction filter takes some effort and understanding. This is one of the reasons why I write "step by step" articles of walking through the process. If you can follow the steps in the article and arrive with similar results, mission accomplished :-)

 

Focus Fidelity joins a "very" small group of room correction software that can achieve accurate sound reproduction both in the frequency and time domain for just about any loudspeaker and room combo.

 

Kind regards,

Mitch

[mitchco]

Hi Bob, good idea!

 

Kind regards,

Mitch

[mitchco]

Hi @dm68thanks! I don't know if David @Focus Fidelity has that feature in the export filters yet... In the interim, an easy way to to split the stereo filter is to use an audio editor like Audacity to open up the stereo filter and select "split stereo track into two mono tracks" like so: https://manual.audacityteam.org/man/splitting_and_joining_stereo_tracks.html

Then select the top split track and Export as "other uncompressed file" and in then click options and choose .wav as the header and in encoding choose 32 or 64 bit float (based on the format exported by Focus Fidelity Filter Designer) and save as left channel. Repeat for the right channel and now you have two separate mono channels for HQP.

[mitchco]

 

23 hours ago, Yourmando said:

Does applying speaker EQ from anechoic data before running the room correction software improve the end result? Or does a SOTA room correction  software obviate the need to apply anechoic speaker EQ?

 

@Yourmando thanks for your comments. 

 

I have performed this myself, using the same anechoic data, and my tests show that it does not improve the end result. Of course, if one is not using room correction eq, it helps.

 

SOTA DRC/DSP, that is correctly applied, not only alleviates the need for anechoic speaker eq, but can be applied at a much finer resolution than a few PEQ filters can do. I.e. the response tracks closer to the ideal minimum phase response. In addition, the left and right channels have virtually identical frequency response which means the phantom stereo image is dead centre along with a number of other benefits as described in this article.

 

As you know, the much bigger problem to solve is the room itself - room modes, standing waves, non-minimum phase response in the low frequencies with +20 to 30 dB SPL response variances are large issues to deal with. Using SOTA DSP/DRC makes way for even sounding bass that is crystal clear. When I say SOTA room eq, I mean DSP that works both in the frequency and time domain, like David's Focus Fidelity as reviewed here.

 

The issue I have with h/w DRC (i.e. Trinnov, JBL Synthesis, Storm et al) is that the onboard DRC has very little resolution below 100 Hz where there are only 2 bands of eq. So right where you need the power of DRC those devices have none. You can find a comparison along with the math behind it if you search my threads a bit.

 

Don't get me wrong, I appreciate the anechoic data and if you are not using room eq, it is beneficial. But if you are using SOTA room eq, there is no real benefit to applying eq using anechoic data before DRC.

 

[mitchco]

3 hours ago, MagnusH said:

As a REW user, and considering Dirac is useless nowadays, I warmly welcome new DRC with time/phase corrections. I don't know how this software compare to the few real DRCs out there, like Acourate and Audiolense, but if nothing else it sure looks much more modern.

 

Good news anyway, I might give this a try!

Hi @MagnusH, I can say that David's software is in the same class as Acourate and Audiolense wrt to time/phase corrections.

[mitchco]

Hi @markus8 Currently, I have too many projects on my plate, I will see what I can do...

[mitchco]

Hi @dathzo Having spent more time with both DL and FF there are two differences that have come to light.

 

Dirac uses IIR filters at low frequencies. IIR filters cannot address the non-minimum phase behaviour at low frequencies that exists in virtually every room. This requires excess phase correction, which means a FIR filter. While Dirac does use FIR filtering, it is not at low frequencies. One can verify this by using a FIR filter designer to open up a Dirac correction filter, extract the excess phase response and observe no excess phase correction at low frequencies.

 

The other issue is the result of Dirac's averaging algorithm. More measurements for the calculation means a loss of correction resolution at the listening position. In this AES paper https://www.aes.org/e-lib/browse.cfm?elib=15154 it was noted via listener preferences that "measurements more localized to the primary listening seat correspond better with listeners’ subjective ratings, particularly below 300 Hz." My measurements (and listening tests) comparing Dirac with another DSP software that has full FIR filtering shows this as well: https://audiophilestyle.com/forums/topic/58546-article-dirac-live-2-digital-room-correction-software-walkthrough/?do=findComment&comment=1098275

 

Based on my tests, both measurements and listening, Focus Fidelity does not have these issues. 

[mitchco]

@dathzo the method of capturing a Dirac filter is in the post I linked. My complaint is not the number of measurements, but the averaging algorithm used. Again, looking at the link in my previous answer to you, one can see in the comparison chart a loss of correction resolution from 100 Hz to 800 Hz in the Dirac correction. And looks to be over-correcting at 90 Hz. As I said in my previous post, David's FFD is using a different algorithm for multiple measurements and does not have these issues. Cheers!

[mitchco]

@Markus8 Yup, I have been in touch with David. Great to see FFD on Mac! I hope to update the review, but currently don't have the time or an ETA. Will circle back when I do.