From the U.K.:

Rel T-7 Sub-Bass System (3-yr warranty). 200W Class A/B power amp.

15 kg. Connected to power amp, in parallel with main speakers. Extends bass down to 30 Hz!

Features

• Custom-designed 8" long-throw active down-firing drive units and 10" front-firing passive radiators

• Powerful 200 watt Class A/B power amplifier

• 3 Separate Rotary Controls for Hi/Low Level,LFE Level, Crossover Frequency

• Dedicated inputs for Hi Level (Speakon), Low Level (RCA) and 1 (RCA) each with individual volume control. Speaker level and the LFE input can be used simultaneously.

• Extremely low crossover points that allow seamless "blending" with any loudspeaker

• Accommodation of Dolby Digital AC3, DTS, MPEG 2 and any other digital sound format that includes a dedicated Low Frequency Effects (LFE) channel

• Proprietary REL-D™ digital amplifier input provides the appropriate Impedance and grounding environment for most Class D amplifiers

• 9 coats of hand-rubbed piano gloss black lacquer or high gloss white

• Nickel plated steel hardware throughout

• Milled aluminum feet.

Specifications

• Type: Passive Radiator, front-firing passive radiator, down-firing active woofer

• Active Drive Unit: 8in., 200 mm long-throw, steel chassis

• Passive Radiator: 10in., 254mm

• Lower Frequency Response: 30Hz at -6bB in room

• Input Connectors: Hi Level Neutrik Speakon, Lo Level single phono, LFE phono

• Input Impedance: High Level: 150k, Low Level: 10k, .1/LFE: 10k ohms

• Gain Control Range: 80 dB

• Power Output: 200 Watts (RMS)

• Phase Switch: Yes, 0 or 180 degrees

• Amplifier Type: Class AB

• Mains Input Voltage: 220-240 volts, 110-120 volts for certain markets

• Dimensions (W x H x D): 12 x 13.75 x 13.75 in., (305 x 349.2 x 349.2 mm)

• Net Weight: 15.4 kg

• Finish: Piano Gloss Black Piano Black or High-Gloss White Lacquer

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Excerpted from http://www.theabsolutesound.com/articles/a-guide-to-better-bass-tas-197-1/

DESCRIBING BASS PERFORMANCE

Perhaps the most prevalent bass problem is lack of pitch definition or articulation. These two terms describe the ability to hear bass as individual notes, each having an attack, a decay, and a specific pitch. You should hear the texture of the bass, whether it’s the sonorous resonance of a bowed doublebass or the unique character of a Fender Precision. Low frequencies contain a surprising amount of detail when reproduced correctly. When the bass is reproduced without pitch definition and articulation, the low end degenerates into a dull roar underlying the music. You hear low-frequency content, but it isn’t musically related to what’s going on above it. In music in which the bass plays an important rhythmic role—rock, electric blues, and some jazz—the bass guitar and kick drum seem to lag behind the rest of the music, putting a drag on the rhythm. Moreover, the kick drum is buried in the bass guitar’s sound, obscuring its musical contribution. These conditions are made worse by the common mid-fi affliction of too much bass.

Excessive bass is a constant reminder that you’re listening to reproduced music. On the other hand, if you hear too little bass, the presentation is thin, lean, threadbare, or overdamped. An overly lean presentation robs music of its rhythm and drive. Thin bass makes a doublebass sound like a cello, a cello like a viola. The rhythmically satisfying weight and impact of bass drum are reduced to shadows of themselves. However, overly lean bass is preferable to boomy bass.

Two terms related to the quantity of bass are extension or depth. Extension is how deep the bass goes—not the bass and upper bass, but the very bottom end of the audible spectrum. This is the realm of kick drum and pipe organ. All but the very best systems roll off these lowermost frequencies. Fortunately, deep extension isn’t a prerequisite to high-quality music reproduction. If the system has good bass down to about 30Hz, you don’t feel that much is missing. Pipe-organ enthusiasts, however, will want deeper extension and are willing to pay for it.

Much of music’s dynamic power—the ability to convey wide differences between loud and soft—is contained in the bass. A system or component that has excellent bass dynamics will provide a sense of sudden impact and explosive power. Bass drum will jump out; the dynamic envelope of acoustic or electric bass will be accurately conveyed, allowing the music full rhythmic expression. We call these components punchy, and use the terms impact and slam to describe good bass dynamics. A related aspect is speed, though, as applied to bass, “speed” is a misnomer. Low frequencies inherently have slower attacks than higher frequencies, making the term technically incorrect. But the musical difference between “slow” and “fast” bass is profound. A product with fast, tight, punchy bass produces much greater rhythmic precision. Although reproducing the sudden attack of a bass drum is vital, equally important is a system’s ability to reproduce a fast decay; i.e., how a note ends. The bass note shouldn’t continue after a drum whack has stopped. Many loudspeakers store energy in their mechanical structures and radiate that energy slightly after the note itself. When this happens, the bass has overhang, a condition that makes kick drum, for example, sound bloated and slow. Music in which the drummer used double bass drums is particularly revealing of bass overhang. If the two drums merge into a single sound, overhang is probably to blame. You should hear the attack and decay of each drum as distinct entities.

Portions of this article excerpted and adapted from The Complete Guide to High-End Audio (Third Edition). Copyright ©1994–2009 by Robert Harley. hifibooks.com

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A Guide To Better Bass (TAS 197)

by Robert Harley

Nov 04th, 2009

Accurately reproducing music’s low frequencies is the single biggest challenge facing the audiophile. The laws of physics make it difficult to achieve a smooth, extended, and articulate bottom end in our listening rooms. Consequently, many of us live with less than great bass performance.

But wonderful-sounding bass is immensely rewarding musically. The bottom end forms the tonal foundation of some types of music, and in others bass is the source of music’s rhythmic drive, propulsion, and energy. The visceral, whole-body experience of a great drummer and bass guitarist locking into a groove—the kick drum’s transient and the attack of the bass guitar strings combining synergistically—is one of music’s supreme pleasures (at least for me).

In this “Guide to Better Bass,” we’ll look at how you can improve the bottom end of your existing audio system, explore different options if you’re just starting out or upgrading, and consider some general principles for getting great bass.

Let’s start with some fundamentals about bass reproduction. Despite what I just wrote about the importance of bass, it’s possible to put together an extremely involving music system based on smaller speakers that don’t reproduce bass below about 50Hz. This is particularly true for listeners whose tastes lean toward chamber and smaller-scale works in classical music, singer/songwriters in pop, and acoustic jazz. Listeners with those musical inclinations are better off with smaller speakers with limited bass response than with full-range speakers of a similar price that may be compromised throughout the entire sonic spectrum.

Second, bass quality is vastly more important than bass quantity. A leaner presentation without much extension is preferable to lots of bass if that bass is thick, colored, and sluggish. If the bass isn’t well reproduced, we’d rather not hear it at all. The poor bass performance becomes a constant annoyance and a reminder that we’re listening to a reproduction. This is why a superbly engineered mini-monitor can be more musically involving than a large floorstanding speaker.

Third, accurate bass reproduction is expensive. The lower the frequency accurately reproduced, the more expensive bass becomes. Note the word “accurate” in both sentences; you can buy a $500 loudspeaker that has output below 40Hz, but it’s unlikely that the bass it produces will be accurate. Realistic reproduction of the bottom octave (16Hz–32Hz) requires large woofers, which in turn requires a large cabinet. The larger the cabinet the more prone it is to vibration that will color the sound. Enclosure vibration colors the music tonally and destroys music’s dynamic structure. The solution is to build heroic enclosures that don’t vibrate, but such enclosures are extremely dense, heavy, and expensive.

Fourth, a system’s bass presentation affects such seemingly unrelated aspects of the sound as midrange clarity and soundstaging. Thickness in the midbass reduces the midrange’s transparency. A cleaner midbass not only makes the midrange sound more open, it also lets you hear more clearly into the extremely low frequencies. Moreover, extending a system’s bottom end has the odd effect of increasing soundstage depth and our overall sense of the recorded acoustic, even on music with no low-frequency energy. I’ve heard an unaccompanied voice in a large hall reproduced by a pair of mini-monitors with and without a subwoofer. Adding the subwoofer revealed the full extent of the hall’s size, as well as presented the vocalist as a more tangible image within the acoustic.

With those concepts in mind, let’s see how we improve a system’s bass performance.

Match the Speaker to the Room

The deeper the loudspeaker’s bass extension and the more bass output it produces, the larger the room needed to realize great bass performance. Lots of very low bass will overload a small room, making it almost impossible to get smooth response. This fundamental fact is played out countless times at hi-fi shows as exhibitors fight to get a large full-range loudspeaker to work in a hotel room. If you choose too much speaker for your room, you’ll wage an uphill battle in getting good-sounding bass.

Loudspeaker Placement

Correctly positioning your loudspeakers is the single most important thing you can do to achieve better bass. The topic is beyond the scope of this article, but you can get an idea of its importance from the accompanying sidebar “The Physics of Bass.” For specific loudspeaker-placement techniques, download the free booklet “Robert Harley’s System Set-Up Secrets” at avguide.com/hifibooks. The booklet is an excerpt from The Complete Guide to High-End Audio (Third Edition).

Adding A Subwoofer to Your System

There are two reasons to consider a subwoofer. The first is if you like the sound of your main speakers and just want more bass extension, power, and impact. The second is if want a full-range sound but don’t want the intrusion of large, floorstanding speakers in your living room.

Both cases sound simple in theory, but in practice, getting a subwoofer to blend with your main speakers is quite a challenge. Although you’ll undoubtedly get more bass, you might not achieve a sound that is seamless and coherent from bottom to top. That is, you might be aware that there’s this big cone chugging away, seemingly disconnected from the rest of the music.

It’s possible, however, to avoid this nightmare scenario with a little knowledge. First, choose a subwoofer designed for musical accuracy, not home-theater fireworks. Some subwoofers exist to produce the highest possible sound-pressure-level at the lowest possible frequency for playing back explosions in film soundtracks. Others are crafted by musically sensitive designers with high-end sensibilities. Be sure which kind you’re buying.

Second, choose an appropriate subwoofer for your main speakers and your room. If you have a 5.5" two-way mini-monitor in a small room, a sub with an 8" driver is more likely to blend with your mini-monitors than a model with a 12" cone. Moreover, the smaller subwoofer is less likely to overload your small room. The smaller the room and the greater the subwoofer’s output, the greater the odds against achieving a musical result.

Third, use proper loudspeaker placement techniques (referenced earlier) so that the sub produces a smooth response. One of the huge advantages enjoyed by a subwoofer/satellite system is the ability to position the satellites for best imaging without worrying about the bass response, and then to put the subwoofer where it best integrates with your room.

Fourth, spend some time tweaking the subwoofer’s controls so that it blends seamlessly with your main speakers. On the one hand, getting two different products (the main speakers and sub), designed by two different designers, to work together in harmony is asking a lot. On the other hand, you have much more control over a subwoofer than you do over the bass output in a full-range system. Take advantage of the subwoofer’s volume, phase, crossover frequency, and other adjustments to perfectly dial it into your system. Generally, the lower the crossover frequency between the sub and main speakers the better; the main loudspeaker’s bass is probably of higher quality than the subwoofer’s, and a low crossover frequency moves any crossover discontinuity lower in frequency, where it will be less audible. In addition, a low crossover frequency ensures that you won’t be able to locate the sound source of the low bass. A subwoofer reproducing frequencies above 100Hz can be “localized”—i.e., the location of the source of the bass can be detected—which is musically distracting. Too low a crossover frequency will, however, burden small loudspeakers with excessive bass and reduce the system’s power handling and maximum listening level.

Another variable in subwoofer crossovers is the slope. Most use second-order (12dB/octave) or higher filters. Ideally, the crossover frequency and slope would be tailored to the particular loudspeaker used with the subwoofer. But because the subwoofer manufacturer doesn’t know which loudspeakers will be used with the subwoofer, these parameters are compromised for good performance with a variety of loudspeakers.

Some advanced subwoofers have an automatic equalization system built into them that removes the worst room-induced peaks and dips. For example, the superb JL Audio line incorporates the company’s Automatic Room Optimization (ARO) technology. You simply connect the supplied microphone to the subwoofer, press a button, and ARO measures the subwoofer’s response in the room and custom-tailors an equalizer to fill in the dips and attenuate the peaks.

A subwoofer’s phase control allows you to time-align the subwoofer’s wavefront with that of the main speakers. Here’s a simple trick for perfectly setting this adjustment. (This technique assumes that the phase control is a continuously variable knob, not just a simple “0/180°” switch.) Drive the system with a pure tone at exactly the crossover frequency between the woofer and main speakers. (Many test CDs include a full range of test tones.) Driving the system with a pure tone at the crossover frequency causes the main loudspeakers and the subwoofer to reproduce the same signal. Now invert the polarity of the main loudspeakers relative to the subwoofer by reversing the red and black leads going to both loudspeakers. Sit in the listening chair and have an assistant slowly vary the phase control until you hear the least bass. Return the loudspeaker leads to their former (correct) polarity. The phase control is now set optimally. Here’s why: When the main loudspeakers’ and subwoofer’s wavefronts are 180° out of phase with each other, the greatest cancellation (the least sound heard) will occur. That’s because as the subwoofer’s cone moves outward, the main speakers’ cones are moving in, canceling each other. When the loudspeaker leads are returned to the correct position (removing the 180° phase shift), the subwoofer and loudspeaker outputs are maximally in-phase. Any time lag between the main speakers and subwoofer has been eliminated. This technique works because it’s much easier to hear the point of maximum cancellation than the point of maximum reinforcement.

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http://www.whathifi.com/review/rel-acoustics-t-7

A fine effort, well worth auditioning if you want a compact sub with decent authority

For

• Composed, agile and informative sound

• fine build and finish

Against

• It’s just a touch soft with the leading edge of notes

REL's new T-7 subwoofer is an appealing product. It's compact, decently made and not afraid to go loud.

Push the volume levels northward and it stays firmly in charge and impressively composed for one so small.

Unlike most of its rival designs, REL has chosen to go the passive radiator route with this design instead of the more commonly seen reflex port.

In theory both approaches to bass tuning should yield similar results, yet the passive radiator route allows greater scope for fine-tuning the performance. REL has made it work well in this product.

Nicely compact – yet good and bassy, too

The T-7 is essentially a 30cm cube, but the combination of 20cm downward-firing driver, a 200 watt class AB amplifier and forward-facing passive unit means the sub can deliver generous doses of low frequencies when required.

REL is particularly proud of how its products perform through their speaker level inputs, and we can understand why - the T-7 sounds bolder and more informative when wired this way. Yet, even when connected through the line-level option, the subwoofer's poise and insight stays much in evidence.

The T-7 sounds right at home, whether adding a dose of heft to the large-scale action scenes of Inception or just dialling in a firmer foundation to the likes of Kate Bush's subtle, but rather lovely, Snowflake.

Remains agile and informative

No matter the source material, the T-7 remains agile and informative, and able to deliver really low notes without fudging the bass frequencies above.

By the highest standards, the definition of the leading edge of notes is a touch soft, which robs the sound of a little punch and precision. And it's this shortcoming that stops the T-7 from storming this class.

That said, if you're looking for a smart and capable subwoofer that's also on the compact side, this REL is well worth a look.

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http://hometheaterreview.com/rel-acoustics-ltd-t-7-subwoofer-reviewed/

REL Acoustics Ltd. T-7 Subwoofer Reviewed

By: Terry London, November 9, 2012

I have been having a great time the last six months reviewing a series of what I consider reference-level two-way stand mount monitors. This had been done in the context of my smaller two-channel system setup simply for musical enjoyment. This list includes the LSA1 Statement, Reference 3A deCapo-i, and Aerial Acoustics 5B. I became interested in reviewing a pair of subwoofers that would fit in, offering a physically small footprint as well as being relatively inexpensive, compared to the above-mentioned speakers. Based on having very positive listening experiences with REL Acoustics Ltd.'s physically large reference-level subwoofers, I was motivated to contact John Paul Lizars of Sumiko Audio, which is the U.S. distributor for REL Acoustics Ltd. After telling Lizars that I was seeking a pair of subwoofers for a reference-level two-channel music system, he recommended the T-7, which has a relatively small footprint. After setting up many two-channel systems with subwoofers, it has been my experience that using a pair, instead of a single subwoofer, leads to an exponential increase of what subwoofers add to the overall sonic performance of a system.

The T-7 is designed around a front-firing eight-inch passive radiator, with a down-firing active 10-inch woofer. The internal amp is Class AB and rated at 200 watts. On the back of the T-7 are the controls for input connectors (high-level Neutrik Speakon, low-level single phono, LFE phono), phase switch (0 to 180 degrees), crossover switch (variable between 30Hz to 120Hz) and gain control (80dB). Each T-7 is supplied with a 30-foot Neutrik Speakon cable - a nice touch.

REL Acoustic believes very strongly that, in order to get the maximum performance out of its subwoofers, you should use the supplied Neutrik Speakon cable that is easily attached to your amplifier's speaker terminals, along with using REL's Neutrik connector in the back of each subwoofer. REL does not recommend that you use the output from a preamp or receiver unless this is absolutely necessary.

I experimented using both REL's cable and connector and am in complete agreement with the company's suggestions. The T-7 performed at a much higher level with the Neutrik Speakon cable, compared to using an RCA cable from my preamp to the T-7. My speculative hypothesis is, that by using the amp's speaker terminals, the flavor and tonality of your amp is passed on by the T-7 for a more seamless blend between your main speakers and the subwoofer. Finally, REL Acoustics believes that while most subwoofersemphasize the mid-bass from 50 to 90Hz, the company's subwoofers can reproduce very low frequencies (at or around 30Hz), providing the subsonics found in music or special effects in movie tracks, which produce a more natural foundation to the music.

Although there is more benefit from a subwoofer than simply the extension of the lowest bass frequencies in the sound of the system, you do in fact get more dynamics and slam with it. However, in my experience, the wonderful and special attributes that a dialed-in subwoofer can provide to a listening area are sound-staging and spatial qualities between the players within the recording. The depth, height and width of the sound stage tremendously increases. You also get stronger image density and a more three-dimensional aspect for each player. Turning off the subwoofers flattens out the soundstage, creating a more two-dimensional image.

In my acoustic space, the placement and fine-tuning of the pair of T-7 subwoofers were straightforward and rather easy to do. Each T-7 was placed 24 inches away from the front wall on the outside corner of the two monitors and 30 inches away from the side walls. The phase was set at zero. Depending on which speaker I was using, the crossover point was anywhere from 35Hz to 50Hz. The volume also was adjusted according to the sensitivity of which speaker was being used in the system.

I used the system with the pair of T-7s on to listen to Jack Jeffer's big band arrangement of "DOUF March" (Mapleshade), which was recorded in a large hall. Magnificently, the entire soundstage totally opened up and the layering and air between the players dramatically increased in a natural way. The ambience of the recording space was also delivered where it had not been evident before the subwoofers were inserted into the chain.

I wanted to see how the T-7s would perform with a more powerful and deep bass frequency, so I listened to Dr. Lonnie Smith's 3B Hammond bass pedals on the tune "A Matterapat" (Palmetto Records). The bass pedal notes pressurized my room with the type of timbres that a 3B Hammond organ is known to deliver. Again, the spatial qualities made the listening experience more enjoyable and realistic.

Finally, listening to the late, great tenor saxophonist David "Fathead" Newman and his special rendition of "Alfie" (HighNote Records), the acoustic space and location of each player blossomed with the T-7s. The bottom octave of the sextet rhythm section increasingly became bolder, enticing you to tap your toes to the beat.

High Points

• The T-7 is built to a very high physical standard. Its appearance is beautifully finished, and offers great flexibility in setup to blend seamlessly with your main speakers.

• The T-7 will enhance the musicality of any two-channel system and still deliver all the dB levels and macro dynamics if used in a home theater situation.

• The T-7 was auditioned with over five highly regarded two-way monitors. With the built-in adjustments, it was easy to dial them in.

Low Points

• In a high-end two-channel music system, a pair of T-7s will deliver a much higher level of sonic improvement, as opposed to just one subwoofer. Therefore, you must have enough room for the pair to get the greatest possible sonic benefits.

• If your main speakers do not perform at a high level across the entire frequency spectrum, the T-7 might show up this weakness in your primary transducers.

Conclusion

I was not at all surprised by the build quality, fit and finish of the REL Acoustics T-7 Subwoofer. The company proudly manufactures all of its speakers with excellent craftsmanship, regardless of the price point. It was amazing to me that REL was able to bring much of the superlative sonic performance of its reference-level subwoofers to the reasonably priced T-7 Subwoofer. It will work great in a home theater system, but my goal was to see if it would add to the musicality in a two-channel high-level system strictly for music. It wonderfully did just that, the way that I described in this review.

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