|Revel B15 Subwoofer|
|Home Theater Loudspeakers Subwoofers|
|Written by Jerry Del Colliano|
|Friday, 01 June 2001|
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The Revel B15 sub is the first subwoofer from Madrigal’s Revel speaker line in their comparatively affordable Performa series. Priced at $2,995 in Black Ash and $3,295 in faux Rosewood, Cherry or Sycamore wood veneers, the B15 addresses some traditional subwoofer problems with new, highly successful solutions. At nearly 20 cubed inches in size, the B15 is slightly larger than subwoofers like my reference Sunfire Signature, yet it still retains a modest physical footprint.
The B15 is far more than a product that simply fills out a product line. This is a major design accomplishment. First off, the output of this 15-inch subwoofer is staggering at 113 dB at 20 Hz and an awe-inspiring 126 dB at 30 Hz. Revel has made headlines with a Harman-financed research and development budget that makes other high-end speaker manufacturers sick with envy. The B15’s 15-inch driver is yet another example of how Revel is creating products that the rest can only hope to copy. This driver has an incredible three-inch maximum throw distance and very low distortion. Revel downplays the influence of JBL in their work, but set aside everything you have read in the tweak magazines and understand that JBL makes some of the finest subwoofers known to man for professional and studio applications. Having JBL technology and manufacturing techniques available to you when you are designing a reference level, high-end audio and home theater subwoofer has an effect that cannot be ignored.
The amplifier in the Revel B15 is an ass-kicker at 1000 watts, with peaks in excess of 1400 watts. This also helps to reduce the level of distortion and woofer recoiling problems. Upon studying many of the better subwoofers in the market, Revel found that nearly all of them change their roll-off points as the volume increases, which means that you get less lower bass as you crank the volume. Most subwoofers do this to overcome the use of weak amplifiers and/or the thermal release for their tremendous heat. The Revel B15 is physically larger than average and uses far better components to accomplish higher, more accurate output. The magnet on the B15 is 130 ounces and can move insane amounts of air because of a larger cabinet, an advanced driver and a monstrous amp.
Where Revel really steps on the accelerator is their addition of a three band parametric EQ. All great subs need EQ to attain the highest level of performance and integration with full-range loudspeakers, yet EQ has historically been much maligned by under-enlightened audio reviewers and stereo salesman for years. The B15 does give you EQ and, better still, the setup tools you need to make the EQ easy to use correctly.
The biggest breakthrough in the Revel B15 subwoofer is the LFO (Low Frequency Optimization) software, which is the first successful solution to the age-old question of how to correctly set up a subwoofer in a music and/or home theater playback system. In my system, the subwoofers have been set up by Bob Hodas, a world-renowned professional acoustician, using a SIM System II dedicated room analyzing system. While I recommend Bob Hodas with two big thumbs up for those who are looking to get the most out of their AV system, the Revel B15 with its LFO software is a huge step towards you being able to actually set up a serious subwoofer by yourself, with happening results in your system and, more importantly, in your room.
The Revel LFO software can be downloaded for PCs (or Macs using PC emulation software) from Madrigal.com and works in conjunction with a CD of 1/12 octave test tones provided by Revel in your B15’s packaging. You will also need a SPL (Sound Pressure Meter) from either Radio Shack (about $40) or a more accurate device, which will cost more.
As you start the LFO software, you can choose either the Novice or Advanced mode. Both modes lead to the same results. The Novice is more geared toward assisting you, the end user, in setting up your own woofers, as the Novice setting has more detailed directions and logical progression of steps.
The first question asked is, "Do you listen to mostly music or home theater?" This requires an easy enough answer that you enter right into the LFO software on your PC. You also have a dialogue box in the LFO software that allows you to make notes about any details of particular room settings, like the physical placement of the sub(s), etc.
You are next asked, "How many seating positions will be used?" You can toggle up to as many as eight positions. With each setting, the LFO software adds an extra chair to the screenshot, which you can drag and drop in the approximate location of the seating position.
Your AV preamp is the next factor you need to consider. Most people don’t even know that their AV preamps are sophisticated crossover systems. The Revel B15 needs to know what kind and where your crossover is going to be set. The THX standard is 80 Hz and Revel suggests you start there. You can use a different crossover if you like, but you may start at 80 for the sake of THX reference. On a Proceed AVP, like the one I use in my reference system, you can use the menu to choose the THX Standard as your crossover mode.
After you are done with your AV preamp, you will want to prepare your room for testing, which includes quieting your environment. This means that you must turn off any music and your HVAC and especially setting your system up to bypass the surround modes and stereo set-up. With these steps complete, you are ready for the Revel set-up Test Tone CD.
In playing the Revel Test Tone CD, the first test is to set the level of your main speakers to 80 dB, which requires you to use the volume control of your preamp and your SLP meter so that you are set at 80. After that, you turn the subs back on and the speakers off to measure the volume output of the woofers, making sure that they match at 80 dB as well. This will require adjustments to the volume knob of the B15. The SPL meter can be placed near your seating position.
Once the sub and the main speaker levels are set, you are ready to set the phase. This is the part where we, as mere mortals, start wildly guessing what phase setting is best. Realistically, there is no way to really tell without actually measurements like the ones you are going to get from the LFO software, even though nearly all powered subs now on the market come with phase control. With the phase adjustment on the back of your B15, you adjust the phase from 0 to 180 degrees until you find the highest level of output on your SPL.
Using the LFO software, you then scroll through the phase set-up directions and get to the Sound Level Measurements, which will come from the test CD and readings from your SPL. When you have the right screen on your LFO software and/or a legal pad and pen ready to go, you can press Play on the CD and start measuring output from your speakers and sub in your SPL meter every 1/12 octave. You can then enter in the levels that you have gotten from your SLM, based on the frequencies recorded on the CD and coming from your speakers and sub(s). Once you are done with this task, which takes only a few minutes, the LFO software outputs a graph that shows all sorts of curves that no one expects you to really understand. Even so, clicking the next button moves you amazingly into an exact layout of the back of your Revel B15, with graphic illustrations of exactly how to best EQ your sub in that location. Revel even goes so far as to hand-draw red circles so that you can see precisely where to dial in your sub’s settings.
Your first set-up may or may not be in the best location. The Revel LFO software gives you a very easy and very intuitive "save as" functionality that allows you to try this process over and over again. Remember, placement EQ is the best way to begin setting up your sub. The pros recommend that you try a number of locations in your room, so that you know you are in the best location for your environment.