Product Review - B&K AVR307 Surround Sound Receiver - May, 2002
Power: 150 Watts RMS x 7 into 8 Ohms
Formats: DD, DTS, THX-EX; RS-232 Port for Upgrades; 24/96 DACS
Size: 7" H x 17" W x 15 1/2" D
Weight: 58 Pounds
B&K Components; Web http://www.bkcomp.com/pcindex.html
Visit the B&K website, and you find the following quote by Walt Whitman: “Simplicity is the glory of expression.” Visit the product page for the AVR307, and you find yet another quote by Walt Whitman: “Perpetual moderness is the measure of merit in every work of art.” (Someone at B&K likes Walt Whitman!)
“Simplicity” and “Moderness” are virtues that should definitely be embraced by any receiver manufacturer these days. There are so many features, that setting up a receiver can be both overwhelming and intimidating. And with the perpetual onslaught of new audio formats and the amazing pace of technological advancements with DSPs, one can be modern today and feel out of date tomorrow!
So, has B&K embraced these virtues in the design of the AVR307? Read on!
The AVR307 is THX Ultra certified. There are seven channels of amplification, and each channel is rated at 150W into 8 ohms and 185W into 4 ohms. 1% metal film resistors are used in the entire active circuitry, and a Class A pre-driver circuitry drives a Class AB MOSFET output stage.
With regards to analog A/V connections, there are 7 inputs and 5 outputs, all with stereo audio, composite video and S-Video capability, plus a set of 7.1 surround outputs. A set of 5.1 inputs is present for the DVD-Audio/SACD buffs. Note that these are analog pass-through inputs, and there are no bass management features that can be used with these inputs. The AVR307 is not alone here: most receivers lack this capability. There are also 2 component video inputs and 1 output. The manual states that these should pass HDTV signals without compromise. Their bandwidth specification, however, is stated to be 10 MHz. This restricted bandwidth will definitely compromise the signal. Perhaps there is a mistake in the manual. It should be more like 100 MHz.
On the digital side, there are 6 coaxial inputs and 5 optical inputs. One output of each type is also available. The digital inputs cannot be assigned to any source, however, the source name is editable in the setup menu. An IEEE 1394 port is present as well, although this is not currently used.
There is no AC-3 RF demodulator and no phono section. B&K makes external devices that can be purchased separately.
But what formats can it decode? Well, almost all! Dolby Digital 5.1 and EX, Dolby Pro Logic and DTS 5.1 are the supported formats. Notable exceptions are Dolby Pro Logic II and DTS ES Matrix/Discrete. Also, the THX certification brings with it the standard set of THX goodies like Cinema Re-Eq, Timbre Matching, Adaptive Decorrelation, and Bass Management. All the decoding as well as the 96 kHz, 24 bit A/D and D/A conversion is performed using Motorola’s DigitalDNA technology with their 56362 chip.
The setup procedure for the AVR307 is exactly the same as that of the B&K Reference 30 Preamplifier/Surround Sound Processor, which was reviewed by John Kotches. I won’t repeat what was already said about the setup procedure. Instead, I will focus on some aspects of the menu system that I liked, and some that I did not (The scan of the menu system is courtesy of John Kotches).
Most receivers that are THX certified offer a speaker size selection of “Large” or “THX”. In the former case, a full-range signal goes to the speaker, and in the latter case, frequencies below 80 Hz go to the subwoofer. The AVR307 provides additionally flexibility in that the crossover for the main speakers is selectable from 20 Hz - 200 Hz in 5 Hz increments. I don’t know why the upper limit goes all the way to 200 Hz, because frequencies above 80 Hz from a subwoofer are easily localizable, and even the little modular speakers will handle 120 Hz. In any case, if you need to crossover at higher frequencies, you can. Note here that the crossover is only engaged if the speaker is set to small. In addition to being able to select the subwoofer crossover frequency, the crossover slope can be changed. I just wish that this flexibility could be extended to the other speakers too.
One problem that plagues all listening environments is resonance. Resonance colors the sound, and consumers try to mitigate its effect by designing rooms with carefully selected dimensions, optimizing loudspeaker and listener placement, and by using acoustical treatment. If you don’t know the resonant frequency of your room, you can compute it using the following formula: 1130 / (2L). In this formula, 1130 is the speed of sound in air in feet/second, and L is the room length, in feet. What you get is the fundamental resonant mode frequency. All integral multiples of this frequency will also be problematic. Since a room has three dimensions, there will be basic resonant frequencies in all of those directions, so you can calculate them, using the same formula shown above, for not only the length, but the width, and the height. For example, if your room is 20' long, by 15' wide, by 8 feet high, the resonant frequencies will be 28.25 Hz, 37.67 Hz, and 70.63 Hz respectively.
Even though the effects of resonance can be reduced, they cannot be eradicated by the methods mentioned above. In comes DSP! The AVR307 provides a notch filter that can attenuate the excess SPLs at and around a resonant mode. Both the frequency of the notch and its width (Q) are selectable. I really like this feature and used it to tame a nasty mode in my room. For a future version of this product, wouldn’t it be nice if the receiver came with a microphone, which you place at the listening position and then press configure. The receiver then generates a sequence of test tones, measures them and performs DSP voodoo to provide a flat in-room response. There are such products that do this, however, it would be nice to see it in a mass market receiver!
The AVR307 provides the ability to assign the number of speakers that are to be used with each listening mode. For example, you may wish to use 7 speakers when in “Surround” mode and only 2 speakers when in “Stereo” mode. For each “Favorite” audio mode, “Surround”, “Stereo”, etc., one can assign the number of speakers to be used. When the source format changes, the AVR307 seamlessly switches to the selected number of speakers. I like the flexibility of this feature.
The part of this setup that lacks good explanation in the manual is whether to use 6 or 7 speakers in a 7.1 channel setup. There are currently no DVDs with a 7.1 channel mix. All the new formats, Dolby Digital EX (THX EX) and DTS ES Discrete/Matrix, are 6.1 channel formats (Dolby's is actually 5.1 with a matrix sixth channel embedded in the stereo for the rear channels) . THX Ultra2 receivers will have some software that will be able to extract information for the rear surrounds, but the AVR307 is not Ultra2 certified.
So where does this 7th channel come from? The answer to this lies on page 49 in the AVR307 manual. A careful inspection of this mode reveals that if you select 7 speakers in the menu, the rear surrounds receive the same signal as the side surrounds. However, if you select 6 speakers, some additional decoding is performed, and this decoded signal, a mono signal, is sent to the rear surrounds. In fact, the display reads “Dolby Digital EX” when you select 6 speakers and the source is Dolby Digital, and it reads “Surround 7” if 7 speakers are selected. There is already plenty of confusion with all the formats that are out there, so I feel that this issue merits some detailed explanation in the manual. Some figures about speaker positioning in the various modes would also be nice.
“Presets” are a feature of the AVR307 that allow you to save settings and recall them instantly. The information that can be saved includes the audio source, video source, volume, audio mode and number of speakers, the tuner station and band settings, levels for the center, rear and subwoofer, and whether you want EQ to be on or off. There can be 40 presets in each of two zones. Recalling a preset involves either using the menu and selecting the preset, or punching the preset number followed by the select button on the remote. I used the latter option, since using the former option was cumbersome. The figure below shows what the menu looks like: each screen displays partial information for a preset. If you don’t remember the number for the preset that you would like to recall, you have to press the arrow key, up or down, until you get to the desired preset. I would much rather have several presets listed on a page, and then I either select one from that page or scroll down to the next set of presets. This would be much faster.
The menu system took some getting used to. Once I was acquainted with some of the peculiarities, which required occasional assistance from the manual, I was able to navigate around quite easily. The flexibility does lead to some of the complexity in the menus, however, I feel that some improvements in both the manual and the user interface could make this process easier and simpler.
The receiver comes with a universal remote capable of controlling up to eight devices, including the receiver. It is preprogrammed with codes to operate over 1000 audio and video components, and if your device is not in its database, it has learning capability. There are also 5 macro buttons, and each of these buttons can send out up to 15 commands. There are also dedicated buttons to adjust speaker levels. I found these to be very useful in making temporary adjustments to the source without having to navigate through the menu system. Another nice feature is the ability to retain volume and surround control while operating a different device. This is achieved by pressing the device button, DVD for example, twice. The small LCD screen will then display “A_DVD” instead of “DVD”, indicating that the audio controls are active in this mode. All the buttons on the remote are backlit. Also, the “Light” button is large, and it is located at the bottom of the remote, so it is easy find in a dark room. I liked this remote.
Upon receiving the AVR307, I plugged in all the cables, popped in a CD, and pressed PLAY. Out came the sound from all 7 speakers. I pressed the “Stereo” button on the remote hoping that would engage only the front 2 speakers, but that did nothing. It was time to read the manual. It turned out that the receiver was set to play a stereo source with 7 speakers. After digging through the manual, I found that this behavior could be rectified by either pressing “Stereo->Select->2” on the remote, or changing the speaker selection for this mode in the setup. I chose the latter, and after that, everything was happy. I don’t know if this is the default factory setting, but if it is, I would like this changed. Out of the box, a stereo source should be decoded as stereo and only the front mains should be engaged. If a user wishes to change this behavior, they can do so during the setup process.
Once the receiver was properly setup, I found no anomalies with either DVDs or CDs. There were no hiccups in detecting the source format. Like the Integra 9.1, however, there was a delay before any sound would come out of the speakers. On this receiver, the delay was about a second longer (about 2 seconds on average). This problem existed with both DVDs and CDs. I would like to see this delay reduced.
One other aspect of the receiver that bothered me initially was a popping sound I heard when I skipped between tracks or when the source was interrupted. B&K says that this is “due to the absence of muting in the output circuit. This is how B&K can offer an accurate and detailed reproduction of the source signal.” Several other processors behave similarly. It just takes some time getting used to.
In describing the sonic attributes of this unit, two words come to mind: punchy and refined. The amplifier performed effortlessly, even at high volumes, with no signs of clipping.
Patricia Barber’s “Café Blue” (Premonition Records), track 11, “Nardis”, has an excellent percussion solo. The cymbals sounded crisp, never erring towards being bright, and the drums were punchy. In Buena Vista Social Club’s production of Ibrahim Ferrer (World Circuit), track 5, “Mami Me Gusto”, the voice of Ferrer was free of grain and chestiness. And in Vivaldi’s “The Four Seasons” (Sony Classical) performed by the Venice Baroque Orchestra and Giuliano Carmignola, the soundstage was big, and the dynamics never sounded compressed.
My impression with movies was equally positive. The reproduction of my two reference tracks, the pod race in “Star Wars, Episode One” and the Normandy Invasion scene in “Saving Private Ryan” had a visceral impact. The 360 degree soundfield created by the pods and the bullets was very convincing.
To evaluate the performance in 7.1 surround mode, I watched “Star Wars, Episode One” and “Gladiator”. The former movie has a “Dolby EX” track, and the latter one has a “DTS ES Discrete” track. Since the AVR307 lacks “DTS ES Matrix/Discrete” decoding, I watched this movie in the “DTS SUR EX” mode, which is DTS 5.1 plus THX EX. The surround mode was set to use 7 speakers. When watching these movies, the front panel read “Surround 7” and not “Dolby EX” or “DTS ES”. I went back to the manual, and a careful inspection showed that both 6 and 7 channel setups produce sound through 7 seven speakers. In a 7 speaker setup, however, no matrix decoding is performed. The surround-back left and right speakers reproduce the same sound as the surround left and right speakers respectively. In a 6 speaker setup, you still get sound out of 7 speakers, however, matrix decoding is enabled. This is confusing, and I would like to see some more explanation of this in the manual. How did it sound? Well, there was some improvement in the soundstage behind me, however, I could live without this improvement. I had the same opinion when I watched "Gladiator" through the Integra 9.1, which has “DTS ES Discrete” decoding.
The one format that I missed while watching regular television was “Dolby Pro Logic II” (DPL-II). I, like several other reviewers at Secrets, find this to be an improvement over “Dolby Pro Logic”. I hope that an upgrade from B&K to remedy this situation is on the horizon!
Towards the end of the review process, I plugged my Proceed AMP3 into the system for stereo listening. One of the big complaints that folks have with receivers is the compromise that results from the use of a single power supply that is shared by both the amplifier and preamplifier sections. The other complaint is often directed towards the compromise in the quality of the parts used to attain a desired price-point. So, I wanted to see what this setup would accomplish. I don’t think that there should be any surprise when I say that the sound was definitely improved. Note here that the AMP3 is about $500 less than the AVR307, and it only offers 3 channels of amplification, with each channel sporting its own power-supply. Was the difference dramatic? No, but there was a definite improvement in the sense of rhythm, the bass definition, and a smoothening of the mid-range. The law of diminishing returns is upheld here! The AVR307 preamp section alone, however, was a great match for the Proceed. This is definitely the highlight of the system, with the only lacking sonic quality being tight bass which still seems to be reserved for more expensive processors. Again, the difference here was not big, and from a price/performance criteria, the AVR307 wins. The reason I write this is because there is an obvious path to improving the sound quality of this system by using an outboard amplifier. Also, the two unused amplifier channels can be used to drive your speakers in the second zone. Here is a PDF that shows B&K's instructions for making the change. You will need Adobe Acrobat to read it.
How did it compare to the Integra 9.1?
The last receiver I reviewed was the Integra 9.1, which I found to be a very fine sounding performer as well. While I did not have the 9.1 receiver on hand during the current review, I did have some recollections of its sonic attributes. What I write here is therefore purely from memory.
First of all, both receivers sound very good. The differences between them are subtle, albeit perceptible. On orchestral recordings, I preferred the sound from the AVR307. I found the sound to be a touch punchier, which produced an improved bottom end. The AVR307 amplifiers are rated 20W higher than the Integra’s, so it could just be that the small extra reserves on the B&K were enough to accomplish this. The same held true for movies. On vocal recordings, however, the slight edge went to the 9.1. I found the vocals to be a touch smoother with the 9.1.
With regards to setup, the 9.1 was much easier to use, although it lacked the flexibility of the AVR307: no room mode compensation, and no adjustable crossover selection, for example. It just took me a little longer to figure out the AVR307’s interface, with an occasional glance at the manual. After that, however, I had no problems.
So, the differences in sound quality are subtle, however, the differences in usability are not. You should therefore play with both receivers - not just listen to them - to figure out which one better suits your personality.
The AVR307 is an extremely fine sounding receiver. It is both software and hardware upgradeable, so you can be sure that this system will not become stale and in need of replacement. It is just a matter of time before we see upgrades for decoding the missing formats: DPL-II and DTS ES Matrix/Discrete. The bass management features are very flexible, so you can optimize the integration of the speakers in your setup. The subwoofer fine tuning is especially nice. And you can tame the room modes that plague most listening environments. If you want DSP modes, however, you must look elsewhere because there are none, which is fine by me. This receiver is one that you must audition. Recommended? Absolutely!
- Sumit Chawla -
Amplifier – Proceed AMP3, White Audio Labs MonoBlocks
Speakers – Osborn Eclipse, Krix Esoterix, Revel Ultima Voice
Subwoofer – HSU Research TN1220
Cables – MIT2, Monster THX Subwoofer Cable
Power – PowerPlant P600
DVD Player – Panasonic A110
Television – Toshiba 40H80 HDTV
Satellite Receiver – Dish
© Copyright 2002 Secrets of Home Theater & High Fidelity
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