The topic of room tuning or digital equalization has never been a more relevant topic in the world of consumer electronics with seemingly every feature laden receiver and most new AV preamps boasting some form of room correction software under the hood. For serious audiophiles and high end home theater enthusiasts with up to 7.1 speakers in their system - there is an exciting new solution on the market. The neptuneEQ 7.1 channel automatic room equalizer was designed to correct room acoustics and the audio components problems with a strong design emphasis placed on ease of use thus the unit is friendly to the D.I.Y user. This equalization system is designed for higher end consumer users at a cost of $3,995.
The NeptuneEQ has both balanced XLR and unbalanced RCA inputs and outputs for all eight channels and utilizes high resolution 96 kHz 24-bit conversion. The seven primary channels are tuned utilizing a one third octave equalizer and the sub or LFE channel utilizes a one sixth octave equalizer. In addition to equalization, this system analyzes the room and automatically sets the subwoofer crossover points to best fit your system's unique needs. It also calibrates speaker levels and sets delays to align the distances to the listening position for each individual speaker. The system comes with a calibrated microphone and cable so no external computer is necessary. There is a graphic display on the front panel that shows you menus and parameters and the unit is controlled via a circular navigation button similar to that on your DVD remote control. The two-rack space unit is made to sit on a shelf and comes with rack ears at a small additional fee. The neptuneEQ is a good-looking design, one that would fit well into any component rack.
Setup of the neptuneEQ is very straightforward and easy to accomplish. It is important to read the manual since there are several layers of complexity and sophistication that you will need to understand if you're going to get the best out of your system. The manual is well written and clearly explains menu navigation and operation in a step-by-step process. My 5.1 system is all balanced, so I utilized the XLR inputs and outputs which are clearly labeled on the back of the box. The neptuneEQ comes with its own calibrated measurement microphone for running tests and I like the fact that they included a 25-foot cable, which should be ample length for most home theater setups. They even include a small stand for the microphone and a weighted bag to make sure that the microphone does not tip over when balanced on your chairs, so you do not have to supply your own microphone stand.
The setup tests may be performed either automatically or manually. Obviously the easiest method for most consumers will be to utilize the automatic adjustments. The adjustments include equalization, speaker level, crossover frequency, delays, and woofer phase (extremely important). The tests can be performed all at once or as individual tests. For someone such as myself (a professional audio calibrator by trade who tunes recording studios and residential high end music and theater systems), with sophisticated measurement tools, automatic settings may also be fine tuned manually once the tests are run. This feature is an absolute necessity in my book. Another great feature in this box is the power amp sensitivity adjustment. This allows you to adjust for the fact that you may have mixed and matched different manufacturer's amplifiers and speakers to assemble your home theater system. You may also have a combination of balanced and unbalanced products in your system as well. A shortcoming is the fact that they do not allow for a sensitivity adjustment for the subwoofer. With so many manufacturers providing self powered subwoofers and unpowered subwoofers it seems like a sensitivity adjustment for the sub or LFE channel should have been included.
Neptune has also recognized the fact that listeners will have certain subjective preferences and has incorporated a section for what we would call tone control. There are nine tone control presets available to the end-user. Five of these presets are settings for what Neptune has labeled movie, music, television, games, and flat. The other four settings are user adjustable storage locations so that you can create and name four of your own tone curves.
For my initial tests I simply wanted to find out what the audio quality was like on this unit. The easiest way to do that was to do a manual setup and listen in stereo mode so I could use my high-resolution audio sources. In my system I use analog minimum phase parametric equalizers for tuning the room. Since the neptuneEQ is a one third octave equalizer, which means fixed center frequencies and fixed bandwidth, I mimicked my parametric curves as best as I could for the listening tests. The curves matched closely enough so that I could make my judgments based on sound quality as opposed to tuning. I primarily used my standard reference CD that contains a selection of pop, R&B, orchestral, country-western, blues, rock, and jazz recordings. After a fair amount of listening, considering the fact that I was comparing an ultra-expensive, professional grade studio analog equalizer to one using digital conversions in and out, I felt that the neptuneEQ sounded pretty darn good. As one would expect, the analog equalizers exhibited more depth more air, more solid imaging and separation of instruments. I would not say that the neptuneEQ meets studio standards but it will easily pass the test with movie soundtracks, Compact Discs, audiophile discs like DVD-Audio and SACD, television and other new school multimedia sources. Add in the effect of room correction to the minimal effect of the component even in the most sensitive of audio chains and you have a lot to gain in terms of overall audio performance with the neptuneEQ in your signal path.
Read more about the performance of the neptuneEQ on Page 2.
At this point I was anxious to try out the automatic setup procedure
and see how it would tune my room compared to the tuning that I had
done personally. I made the sensitivity adjustments, told the box which
speakers I was using, and turned off the crossover adjustment function
because I'm running my system full range. I then followed the manual
instruction as to how to place the microphone for testing. Neptune
suggests putting the microphone in five different seating positions to
take an average of the speaker response in the room. If you would like
to weight the averaging to a specific seat in the room you could place
the microphone positions closer together or you could do as few as two
averages to perform the tests. If you're the only guy that counts in
this listening room you could even leave the microphone in a single
position for all the averages, but moving it around a bit will give you
a larger sweet spot. I felt that the neptuneEQ did a very respectable
job of creating a fairly large sweet spot based on its averaging
method. Its average curve definitely made sense to me when compared to
how I do things when tuning a studio or mastering lab.
When running the automatic tests in the "adjust everything" mode,
the system will pause after each battery of tests allowing you time to
move the microphone to the next seating position. After the automatic
tests were performed I checked the results of phase, delays, and
balance and found them to be quite accurate. When it came to the
equalization decisions I had some reservations about some of the
results. For the left, center, and right speakers the automatic
equalization did a pretty good job from 40 Hz to about 10 kHz. But due
to the open architecture of my house, my right speaker is closer to a
corner than the left speaker, so the right speaker has a fairly
significant buildup at 20 Hz. Because the neptuneEQ's lowest frequency
center is 25 Hz it simply missed the buildup in my right speaker, which
is an obvious distraction when listening. In the high frequencies the
unit rolled off the frequency centers at 12.5 kHz and 16 kHz possibly
due to a slight high Q bump at 13 kHz. This removed the air from the
system and I needed to make adjustments to restore those frequencies. I
also had some issues with how the Neptune dealt with my surround
speakers. My surrounds are not located in a very good part of the room
and have a lot more problems in the frequency domain than the front
speakers. They have some narrow bandwidth dips that are fairly
significant, dips that I personally would not try to compensate for
when equalizing a room. But the neptuneEQ tried to boost these dips,
which removed some headroom from my system.
The saving grace with some of the above issues, especially the
high-frequency issues, is the tone control feature. With the tone
control I could flatten out the top-end cut that the Neptune
automatically put in and I could pull out some of the low frequencies
that the Neptune failed to remove. I could then store this setting in
one of the user presets. Of course, without an analyzer, one would have
to recognize the problem and make these adjustments by ear. With
regards to the factory stored tone control presets, my advice is use it
if you like it. People certainly have diverse listening preferences in
this world and this box lets you have it flat or colored to your
choice. After listening to several sections of several different movies
I would have to say that I was having an enjoyable experience.
This brings me to a basic philosophical difference I have with the
Neptune filter design. I believe that using one-third octave equalizers
to tune a room does not give one the flexibility needed to accurately
address room/speaker interfaces. With a one third octave equalizer, the
center frequency is not adjustable and the bandwidth is also fixed at
one-third octave. Using a parametric equalizer to tune the room, one
can set the center frequency to whatever the problem frequency is and
adjust the bandwidth so that you affect exactly what is necessary. A
parametric equalizer allows one to do a surgical tuning while a one
third octave equalizer in many cases tunes around the problem. Tuning
with parametric filters also has less interaction between the adjacent
filters and so there can be less effect on the phase response.
With that said at an engineering and philosophical level, the net
effect of the neptuneEQ on even the highest end of home theater and
audiophile systems is noticeable and tangible. I would rather have one
in the loop than not for most every system I can think of in the
To date I have only had a chance to look at a few other automatic
speaker equalization systems including the one installed by Meridian in
their 861 AV preamp and a few in-receiver models. The Neptune Audio
neptuneEQ performed better than most and as well as any of the top
level solutions. In terms of audio quality in its purest sense, the
neptuneEQ was one of the elite top performers. The neptuneEQ is a very
good sounding component and it can solve many room/speaker interface
issues that would make many home theaters sound better.