General Asylum: REVIEW: Behringer UltraCurve Pro 8024 RTA/Equalizer Accessory by Bruce from DC

Model:	UltraCurve Pro 8024 RTA/Equalizer
Category:	Accessory
Suggested Retail Price:	$170 (street)
Description:	digital parametric equalizer and real-time analyzer
Manufacturer URL:	Behringer
Model Picture:	View

Review by Bruce from DC on June 02, 2006 at 12:09:44
IP Address: 207.91.86.2

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for the UltraCurve Pro 8024 RTA/Equalizer

A substantial minority of audiophiles prefer smaller standmounted loudspeakers, precisely because their bass output below about 50 Hz is pretty anemic. For these listeners, the extra half-octave or so of bass below 50 Hz is a very mixed blessing -- usually because of most listening rooms' inherent resonance somewhere in that frequency range. They would rather miss out on hearing the bass fundamentals than have to suffer the bass boom at the room's resonant point. It is often a matter of dumb luck -- or heroic experimentation in speaker placement -- that a "full-range" speaker manages to reproduce realistic bass in many audiophile's listening rooms.
The addition of a subwoofer to standmount speakers, with adjustable crossover and level control, can achieve better results . . . but still a good bit of luck and experimentation, with both placement and adjustments is required. As anyone with a Radio Shack SPL meter and a recording of test tones can confirm, every normal-sized listening room has a nice bass peak of 8 dB or more somewhere between 40 and 50 Hz.
As a general matter, what people do when adjusting the subwoofer bass in their room (whether by ear or with an SPL meter) is match the level of the room resonance with the rest of the musical signal. This results in a more or less natural sound but pretty much kills the bass below the room's resonance, depending upon how high the resonant peak is. This setting is independent of the bass extension capabilities of the subwoofer. It's simply a product of the user's unwillingness to hear a bass boom. This was certainly my experience before I bought the Behringer unit, although, by luck it turned out that my main speakers began rolling off significantly at just about the room's resonance point, so by carefully adjusting the low pass setting on my sub, I could trim the room resonance peak down to about 6 db, which wasn't too bad. My final setting -- pre-Behringer -- was a compromise between my desire for maximum bass extension and my tolerance for room boom. However, by eliminating this resonance (boom) with a parametric equalizer, you can take full advantage of whatever maximum extension your subwoofer offers . . . whether it's to 20 Hz (or below) or to only 30 Hz.
Unless you're one of those freaks who sez "Yum. BASS!" and delights in rattling windowpanes, shaking knick-knacks off of bookshelves and other home theater style effects, this equalizer/real-time analyzer is the product for you. In conjunction with a calibrated microphone (another $70), this gadget, placed in series (preamp output> equalizer> subwoofer) with your subwoofer, "listens" to your room and adjusts (equalizes) the subwoofer's output to compensate for the room resonance. The process is automatic and uses pink noise generated by the machine. You put the microphone on a stand in your listening position and punch a button. After a few minutes, the calibration mode turns off, and the display shows the equalization curve that the machine has set. All you have to do is to set your subwoofer level "in the ballpark" and make sure that the low pass setting is high enough to give the equalizer room to work. The equalizer has a maximum range of 20 db so, for example, if your subwoofer is modest and really doesn't reproduce 20 Hz, the equalizer will figure that out and simply leave that band alone, rather than try and drive the sub and its amplifier into distortion.
I have used this product successfully with two different subwoofers -- a Mirage BPS-150, which is rated (and appears to measure) -3dB at 24 Hz (on a 24 dB/octave slope) and an REL Q-401E, which is rated -6 dB at 14 Hz (on a 12 dB/octave slope). The REL equalizes flat at 20 Hz; the Mirage does not. With both subs and my main speakers the Behringer unit achieved a seamless blend; and the subs "disappeared" except for obviously enhancing the bass capabilities of the main speakers.
The effect of this, sonically, is to give a greater sense of the acoustic space in which the recording was made (not appplicable, obviously, to studio recordings) and to give a more realistic quality to the reproduction of bass instruments, especially the double (string) bass. For acoustic jazz, the loudness of the bass no longer varies with the pitch of the note being played. It is possible to hear both the "buzz" of the string being plucked and resonance of the instrument body (which is producing the fundamental musical note) in proper balance with each other and with a realistic decay of the sound. For reproduction of classical orchestral music, eliminating this room resonance "cleans up" a lot of the "muddiness" that many recordings display with massed double basses and cellos playing loudly while preserving the "weight" of a symphony orchestra.
To be sure, the room still resonates at a certain pitch and it is not possible to remove all traces of the "boom" at the resonant pitch, part of which is the result of stored energy. This is not an amplitude problem, it is a "time" problem. It's not that one note is louder than the others, it's that one note is sustained longer than the others. This is particularly noticeable on bass transients, like from bass drums. A subwoofer that uses a tuned port rather than a sealed cabinet will also display this kind of behavior with any note that happens to hit its tuned resonance. So, this gadget doesn't fix everything to perfection.
Finally, after you run the auto-equalizing function, you should study the curve that the machine has generated. If you see a lot of boost in the lower part of the subwoofer's range you should listen carefully to make sure that you are not overtaxing the limits of your sub's driver and/or amplifier. It is possible to manually adjust the equalizer, so you can tweak the machine's settings. In addition, you have a choice of "target" curves for the auto-EQ. I have always used the "flat" curve, but if you find that you are taxing the limits of your modestly-endowed subwoofer, you might consider setting a target curve that has a gentle downward slope, rather than tweaking the equalizer settings by hand. The result might be more natural sounding, while avoiding overloading the sub at the lowest frequencies.
The only other product that is similar to this is made by Velodyne, at about twice the price. Velodyne's "digital drive" series of subs have this auto-calibration facility built in; and Velodyne recently has sold the auto-calibration/equalization electronics as a standalone package, without the sub.

Product Weakness: The product's many functions and capabilities are controlled by a complicated series of nested menus, accessed from the display. The manual, unfortunately, tells you the absolute minimum of how to use it. So, a little trial and error seems to be required. It took me several tries to get the auto-EQ function to work as it was supposed to.
Product Strengths: very effective at what it does, and at a modest price

Associated Equipment for this Review:
Amplifier:	Krell KAV-300i
Preamplifier (or None if Integrated):	none
Sources (CDP/Turntable):	Sony XA-777ES; VPI HW-19 Mk III
Speakers:	Joseph RM-7 si signature (Mk I)
Cables/Interconnects:	Goertz Triode Quartz, MI-2
Music Used (Genre/Selections):	jazz, classical, rock
Room Size (LxWxH):	20 x 12 x 10
Room Comments/Treatments:	uphostered furniture, filled bookshelves, rug
Time Period/Length of Audition:	6 months
Other (Power Conditioner etc.):	Equ=tech 2Q
Type of Audition/Review:	Product Owner

Product Weakness:	The product's many functions and capabilities are controlled by a complicated series of nested menus, accessed from the display. The manual, unfortunately, tells you the absolute minimum of how to use it. So, a little trial and error seems to be required. It took me several tries to get the auto-EQ function to work as it was supposed to.
Product Strengths:	very effective at what it does, and at a modest price