1. Umik 1 Calibration File

Jul 18, 2019  Hello, I have a MiniDSP UMIK-1 microphone and working with REW perfectly. Now I would like to setup my in-car DSP which is an Audison bitTen. I would like to ask that which one is the most suitable/closest equalizer type setting in the EQ menu of REW, or should I use the 'Generic' setting. Nov 17, 2015  I used a Umik1 and REW to find the trouble spots.did the DSP and then tune by ear. As any correction should not be flat. You need to overlay a preference curve I havent tried their full room correction, but have used Dirac, Acourate etc. All work real. Nov 18, 2017  Review Apicella Auto Sound DSP Tuning (Remote Tune) Just wanted to share my experience with my remote tune with /u/skiz32. I've always found it difficult to tune my vehicle and even more difficult to find someone competent and knowledgeable in DSP's.

For the past decade I've been on a quest to achieve what seemed to be the impossible in my theater room: state-of-the-art bass reproduction for EVERY seat, not just the sweet spots. We've written numerous articles on the benefits of multiple subwoofers and how when properly placed (and set up) one can smooth out the bass response across the entire listening area through the process of room modes manipulation which some regard as averaging, but in reality it changes their magnitude and timing so that there is less destructive interference (the major cause of seat-to-seat variations). The result is much increased efficiency and a more uniform sound field within the room.

Before digging into the details of this article, we suggest watching our YouTube video discussion that gives you a basic breakdown of this complex topic along calibration techniques with illustrations to help you on your path towards bass nirvana.

Home Theater Bass Optimization with Multi-Sub + mDSP Youtube Video Discussion

In rooms of predictable shapes and dimensions, there are clear guidelines regarding where to place the subs to achieve optimal bass response. But what about asymmetric rooms like mine? Well, your guess is as good as mine and thankfully this time I was armed with a little black box from a company called miniDSP to help take out some of the guesswork.

Does Pushing the Red Button Solve All Problems?

Auto Room-EQ to the Rescue?

Some may wonder, 'Why not just use auto-room EQ to solve my dilemma?' The problem with auto-EQ is they rarely work as advertised. Some don't even do low frequency correction for the subwoofer channel while others don't quite integrate multi-subs very well, as we've seen in the past.

Frequency Response vs. SPL - Front Row
Yellow: all 4 subs; Blue: all 4 subs + Audyssey

some auto-EQ systems do NOTHING to the subwoofer channel to improve bass.

This image was borrowed from our Multi-Subwoofer Calibration Article and demonstrates what happens when auto-EQ systems try to equalize each sub individually rather than first individually setting level and delay for each sub and then measuring the combined output of all subs simultaneously to apply global equalization. Audyssey has since then updated their algorithms, which helps considerably but we've found some auto-EQ systems do worse or nothing at all for the subwoofer channel. It's really a crap shoot, which is fine if you're a gambling man but we prefer to make our own luck.

Editorial Note about the Limitations of EQ
It's important to note that GLOBAL EQ alone cannot improve seat-to-seat consistency regardless of what any of the Auto-EQ companies claim. You need something far more sophisticated like Harman's proprietary SFM algorithm or a painstakingly manual process of EQ, delay, phase, and crossover adjustability, (like the approach we've taken with mDSP.) Seat-to-seat consistency is best first optimized through positional EQ (seat and sub placement), the proper deployment and setup of multi subs or low frequency bass traps or a combo of both. By itself, EQ is useful to flatten peaks and sometimes fill in nulls (only if they are small), but beyond that it can't manipulate room modes like positional EQ of multi-sub, SFM, or bass trapping does.

Bass Traps

Others may say, 'Why not just add a bunch of bass traps to fix your bass woes?' Bass trapping can be an effective solution for low frequency problems, but to get good results down to the sub 20Hz region, you will need a lot of them and they are quite bulky and unsightly. In addition, anytime you add passive absorption to the room, it turns mechanical energy into heat and thus reduces overall system efficiency. This means you lose overall headroom since you have to turn the bass levels up higher to compensate.
Please note I am not advocating against bass traps. Bass traps can still be a very useful tool as supplementation for reproducing music, especially in asymmetric rooms. Bass traps are often necessary when producing music using instruments in a recording studio environment. In such instances you simply have no alternative if you want better bass. However in reproduction of music in a home theater environment utilizing active subwoofers this is NOT the case.

Editorial Note about Bass Traps:
Bass Traps are acousticenergy absorbers designed to damp low frequency sound energy by reducinglow frequency resonances in a room in attempts to flatten out theoverall response. Since low frequencies are long wavelengths (ie 20Hzrepresents a 57ft wavelength), bass traps must also be quite large to beeffective down in the bass region. For more information, read ourarticle: Bass Trapping Ideas for Non-Ideal Spaces

Multi-Sub + DSP

Multi-subs + DSP or to borrow a term from Harman - Sound Field Management (SFM) is the better solution for reproduction of music in small room acoustics. Multi-subs allow the end user to deploy slightly smaller subs than one super sub and achieving the benefits of modal manipulation for reduction of standing waves while also increasing low frequency coupling. So instead of buying a hulking 15' ported sub, you can now consider dual 12' models or perhaps quad 10' models. While you don't achieve +6dB at all frequencies each time you double up on your subs and co-locate them, you do achieve almost this amount of gain at the very low frequencies where the wavelengths are physically much larger than the distance between the subs (ie. 30Hz = 38ft). Once you fix the seat-to-seat consistency issues utilizing multi-sub, you can then take advantage of equalization of a device like the mDSP 2x4 to fine tune and flatten out any excessive peaks.

Editorial Note about Harman's Sound Field Management (SFM)
Sound Field Management (SFM) is a reference to a very specific Harman proprietary system to reduce seat-to-seat variations. Part of it is the usage of multiple subs but there is also a proprietary algorithm developed by Todd Welti and Allan Devantier, under the investigation of Dr. Floyd Toole, that further reduces seat-to-seat variation, which is part of their PC-based “ARCOS” characterization, EQ and processing solution. During the characterization phase, each subwoofer is measured independently, and each is equalized, and otherwise adjusted independently only for the purpose of minimizing seat-to-seat variations. Only after that is completed does the system calculate the coefficients for global EQ, which is really only possible once one has reduced the seat-to-seat variations in response.

The Procedure

multi-sub + EQ can greatly reduce and even eliminate the need for LF passive bass traps for sound reproduction in home theater.

The first step to achieving excellent bass is proper placement of your subs and seats. In symmetric rooms you can follow our placement guidelines. However, in asymmetric rooms, you're going to need to make a small investment in a measurement system. REW is a very good acoustical measurement program and its absolutely FREE. Download it! Get yourself a calibrated microphone that is good down to below 20Hz and a mating preamp/USB DAC and you will be on your way.

A quick and dirty guideline to proper multi-sub setup:

1. Properly position all of your subwoofers for best performance. Also consider seating locations and how you can move them to help achieve this goal. This is known as positional EQ.
2. Get all of your subs playing the same bass signal (mono LFE + summed bass from all channels set to small in your receiver's bass management).
3. Route the subwoofer outputs of your AV receiver into a device like mDSP 2x4 to manipulate level, delay, PEQ function, etc.
4. Using your measurement system, be sure to adjust delay, level, phase, crossover points, etc to get all of your subs playing well together by minimizing acoustical cancellations and getting the smoothest frequency response possible for all of your seats.Start initially with the two most important seats, then expand outward to all of your seats as you hone in the response.
Note: Measure all subs + main L/R speakers in mono from 10Hz to 200Hz for each seat.
5. Once you've got all of your subs properly integrated, use EQ to flatten peaks and boost sparingly (never more than +6dB) to fix dips. If boosting doesn't fix a dip, don't do it!
Note: Since this is a manual process, I initially applied a small amount of EQ to each sub individually to optimize the response as best as possible. Then, I applied global EQ to really fine tune and flatten the overall response for ALL seats.

Getting All of Your Subs To Integrate at Very Low Frequencies
If you're using subwoofers with different bass alignments (ie. ported vs sealed) and/or bandwidth and output capabilities, you may need employ a HPF to one or more of the subs via mDSP to achieve proper integration of the summed response at very low frequencies where the subs begin to naturally roll off. In my case, I had a mix and match between ported (Status 8T speakers) and sealed (Velodyne DD-15+ and RBH SI-1010 subs) and was able to tailor the very low frequency roll-off response to achieve synergistic coupling of ALL subwoofers at and below the system -3dB point.

Here is a graph of all six of my seated positions BEFORE adding mDSP to the equation.

Bass Measurements Across all Six Seated Positions Before mDSP

While the bass response of the front three seats is flat and even across the entire bass region, the back seats have excessive boost below 40Hz and bad suck outs in the 40-70Hz range, particularly in the back right seat which I deemed the 'mother-in-law' seat. As bad as this may look, the results are actually quite good and difficult to achieve with a system employing only one subwoofer. The response measures roughly 15Hz to 100Hz +/-15dB or up to a 30dB swing depending on frequency or seated position. Certainly we can do better.

Bass Measurements Across all Six Seated Positions with mDSP

And so we have. Admittedly I cheated a bit. I added a 5th sub behind the mother-in-law seat knowing that I had better controls in place with the recently added mDSP product. This sub was purposely put there to neutralize the back seating area dip in the 50-70Hz range but it did much more than that. I was able to reduce the seat-to-seat consistency from +/-15dB to +/-5dB. In most situations, an end user can get pretty close to this type of response with just two or four subs depending on room symmetry and employment of delay and precise equalization compensation.

RBH SI-1010i In-Ceiling Subwoofer placed behind 2nd Row Seating