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Review of SVS 25-31 PC-Plus

Discussion in 'Speakers & Subwoofers' started by JohanZw, Mar 29, 2003.

  1. JohanZw

    JohanZw Auditioning

    Mar 29, 2003
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    Hi guys!

    My name is Johan Zwiekhorst and I review IT & AV hardware and software for a living for various hardcopy magazines in Belgium and the Netherlands. Recently, I reviewed the SVS 25-31 PC-Plus subwoofer. I have translated my article in English for you. Here it is...

    TEST SVS 25-31PC-Plus subwoofer
    Copyright 2002 by Johan Zwiekhorst, Belgium

    Very expensive bass for a very low price

    Streamer: SVS is an American brand of subwoofers which makes only that kind of speakers and sells them exclusively via the internet. The specifications listed promise a bass reproduction as good as or better than those of very expensive subwoofers, but the SVS subwoofers seem to be cheap in contrast. We ordered one and tested it.

    Full text: The subwoofer didn't become popular until home cinema systems and dvd's became more commonplace. Explosions and the rumble of engines have such low frequencies that common speakers can't reproduce those, at least not good enough. For that, you need a subwoofer. In fact, this reasoning can be applied to music as well. Both classical and modern music can use extremely low frequencies which can only be reproduced faithfully by a subwoofer. With classical music, instruments like church organs and double basses come to mind. Modern music can do that with synthesizers and bass guitars. Nowadays, you can go into a supermarket or some other store and buy a 'home cinema system' including a dvd player, amplifier or receiver, five speakers and a subwoofer for less than one thousand euros. Often people are quite impressed by that sound if they're only used to the sound of a tv set. If they would try and play music with such equipment, they would soon find out that it really can't do that properly. Virtually all of the relatively cheap subwoofers you can buy in stores are intended to enhance explosions and engine rumbles for films on dvd. Those subwoofers tend to either only and quite litterally 'blow air' - creating the impression of a very low tone without having to actually reproduce it, or they try to reproduce a tone but it is severely distorted. It may not always be apparent while playing movies, but you can hear it immediately when playing music with such equipment: the subwoofer will make it sound nasty and the sound can improve by switching it off, but then you won't have much reproduction of low frequencies left.


    As with all things, you can only get and expect quality by choosing quality components. That is true especially for a subwoofer: such a speaker should reproduce frequencies below 100 Hz (number of vibrations per second) or so, but then it should play an actual tone and not simply blow air. You can find subwoofers complying with this description, but you usually have to buy them in a hifi store and that means big bucks. An example is the British subwoofer brand REL (www.rel.net): they provide excellent subwoofers which perform brilliantly with both music and films, but they can be quite expensive. Their smallest model has a built-in amplifier of 150 W and costs about 870 euros. Compare that to SVS: their smallest model has a built-in amplifier of 320 W and costs considerably less at about 540 euros. A good subwoofer should have a driver with a diameter of at least 25 or 30 cm and contain its own built-in amplifier with at least 100 W power (preferably more). Such a subwoofer with its own built-in amplifier is called an active subwoofer. The contrast is the passive subwoofer, which does not have a built-in amplifier, so you would need a separate external amplifier for that.

    SV Subwoofers

    SVS is the abbreviation for 'SV Subwoofers'. The company was founded by two real bass fanatics: Ron Stimpson and Tom Vodhanel. Their surnames provided the letters for the company name. The purpose of their company was and is to make affordable subwoofers of high quality. Misters Stimpson and Vodhanel thought long and hard about the proper requirements for such a subwoofer and they investigated several systems during a long time. They tested various bass drivers from different brands, amplifiers of various power specifications and from several brands and a lot of different casings. Loudspeakers were destroyed, amplifiers went up in smoke and casings were disapproved. Eventually, they came up with a concept: the cylindric model. A cylinder-shaped casing is relatively cheap to make and yet very firm and rigid. Think of gasoline or gas tanks, then you'll see what we mean: those are also cylinder-shaped because you can distribute the internal pressure evenly that way while the entire construction remains cheap. If you would choose to use a cubic or rectangular shape, you would have to apply various struts, cross beams and other fortifications to make sure the case doesn't vibrate with the basses. The people at SVS do realize, however, that some folks just do not want a big cylinder in their living room. That's why you can buy cubic or 'boxed' subwoofers from SVS these days as well. That product range is very recent, however, so we'll get back to you about the SVS boxes and stick to the cylinders for now.


    At this time, SVS has three basic cylinder models: three cylinders varying from small to large. All cylinder models have the same diameter: about 41 cm. Their height differs and is dependant on the lowest frequency you would like to reproduce. Those two numbers are in the product name, by the way. The model 25-31 can go to 25 Hz and is 31 inches or 79 cm tall, the model 20-39 goes to 20 Hz and is 39 inches or 99 cm tall and finally there is the model 16-46 which can reproduce a tone of 16 Hz and is 46 inches or 117 cm tall. The actual loudspeaker is situated at the bottom of the cylinder (radiating to the floor) and is protected by a very heavy base plate. Above that base plate is a space so the sound coming from the speaker can escape into the room. That way, the sound doesn't go into your floor or into your ceiling, but effectively into your room. At the top, the cylinder is open as well in order to regulate the sound pressure. That is done by means of a portal system with three openings which is covered by a metal grid. The portal system is tuned to allow for a frequency spectrum that is as straight as possible from the subwoofer's upper range of about 100 Hz downto the very lowest frequency of the cylinder (according to the model 25, 20 or 16 Hz). It is possible, however, to change the default tuning of the subwoofer by means of a couple of foam port blockers which you can insert into one or two portal openings. Each plug lowers the lowest frequency of the subwoofer by an additional 5 Hz, but you would loose some power in the upper bass range. That is a matter of taste, so SVS provides you with the means to test the various possibilities and determine for yourself what you like best. Each cylinder model can be acquired in three variations: passive (the CS series), active with a 320 W amplifier (the PCi series) and active with a 525 W amplifier and an improved driver (the PC-Plus series). We tested the smallest model of the PC-Plus range: the 25-31 PC-Plus.


    Many people in Europe tend to be a little nervous about buying equipment over the internet. Will it arrive in prime condition, and what guarantees do you have when something goes wrong? Not good, money gone? Happily, that's not the case with SVS. They use the transport company Bax Global for their transports to Europe. According to our own experience, Bax Global cares for the goods they transport very well. The subwoofer as it was delivered at our door came in a box that was in immaculate condition: there wasn't even a dent. Bax Global will phone you as soon as the transport has arrived in your country (usually within a few days after having ordered it!) to agree on a delivery time. They stick to that agreed time. The people at SVS respond quickly to e-mails and provide quite a good warranty. If necessary, they will replace the driver or - if needed - the entire subwoofer if you're not satisfied, but you will have to pay for the extra transport costs. We contacted some people via the internet who had bought an SVS subwoofer and not one of them had a bad experience with the transportation of the subwoofer. All claimed their subwoofer arrived in prestine condition. So that's good news. When we opened our box, we found that the subwoofer is packed in very thick foam, so it should be pretty insensitive to shocks during transport.


    After we unpacked our subwoofer, we connected it to our surround equipment. We used a Sony STR-DB940 receiver of 5x 110W, front left and right speakers are Mission 774, center speaker is Mission m5c and rear speakers are Eltax Linear Response 6 Mk III. The next step is calibrating the subwoofer and the other five speakers so they all sound equally loud. For that, you need a decibel meter or sound pressure level meter. Please pay attention, because the sound level meters often used for the determining how loud discotheques and such venues are usually not good! They tend to be dBA-meters wich filter out the best part of the low frequencies, making them unsuitable for calibrating a subwoofer. You can still use those for calibrating normal speakers, just not for your subwoofer. You need a dB-meter with a so-called 'C' weighing for that. Just check if the meter you want to buy has a selector for 'A' or 'C' weighing. If it doesn't, chances are that it's a dBA-meter. Don't buy that. A meter with both 'A' and 'C' weighing should cost something between 50 and 70 euros in most electronics stores. To perform the calibration, we require test tones. Most 5.1 surround amplifiers have special test tones for speaker calibration on board, but these may not be correct for a subwoofer. There are special calibration dvd's you can buy to set up your surround system. We would recommend those. The ones from Avia and Video Essentials are both good. Configure your amplifier so that all speakers are set to 'small' (the default usually is 'large') and set their cut-off frequency to 90 Hz or lower. Some amplifiers cut off 'small' at 120 Hz and that is higher than the SVS subwoofers will go, so you would need to correct that. If your amplifier doesn't allow you to set the cutt-off frequency, you will need to experiment which configuration of 'small' or 'large' sounds the best. After that, start with the test tone for the front left speaker and set the master volume of your amplifier so that your decibel meter will indicate 75 dB from your normal listening position. Select the other speakers one by one and change their indivual volumes (not the master volume!) until each speaker - including the subwoofer - measures 75 dB. That's about it: now you can play music and films. For a more complete tutorial on calibrating a surround system, please visit our website: http://www.diskidee.be/av/cursussen/index.htms/3588. (This website is in Dutch!)


    We let loose about everything we had on the SVS 25-31 PC-Plus. First and foremost, it was evident that this subwoofer has way too much power for an ordinary European living room. 525 W is clearly intended for much larger (American?) rooms. We had to set the subwoofer output of our amplifier to -7 dB and the volume control of the SVS to barely 10% to achieve a sound pressure of 75 dB during our system's calibration. SVS told us their subwoofer inputs are quite sensitive and they plan to make them less sensitive in the future. If you were used to explosions in films sounding like someone slamming a car door shut, hold on to your suspenders! The SVS makes you live through such an explosion. You can all but feel your teeth rattle. The sound of tanks, ships, planes and space ships has never been so impressive. The real quality of this SVS subwoofer shines when playing music. From classical music to pop and rock, all basses sounded tight and full. A church organ that plays its lowest notes in a church will make you feel those notes in your gut: the SVS subwoofer could do that as well. Much modern music, from Metallica to Enimem, will contain low frequencies of even 15 Hz and lower. Our SVS model doesn't go that low (you would need the biggest one for that), but even those basses have never sounded as good.


    It is of course the intention that a subwoofer would produce impressive basses, but we don't want a 'boom box'. That means that a subwoofer should not only try to move air, it should rather try and produce the actual low-frequency notes. Only then, a subwoofer will be usuable for producing music and specifically signals with frequencies below, say, 90 Hz. That means: your subwoofer should do this better than your main speakers, otherwise there's no point in using one. Various kinds of classical music show this very well. Musical pieces with a prominent presence of a cello or a double bass come to mind, obviously, but a piano can do that as well. A lot of people may not realize this, but the lowest note a piano can produce has a frequency of 28 Hz! Modern music has examples as well. One of our favorite tests consists of playing a record with a solo bass clarinet, more specifically the track "Diepe adem" ('deep breath') on the instrumental cd "Omzwervingen - liedjes zonder woorden" ('Rovings - songs without words') by the Flemish singer/composer Willem Vermandere. If you play this number and switch off the main speakers, the subwoofer will be the only one left playing. And it will have to carry the entire melody (most of which is below 90 Hz). We were most impressed by the SVS 25-31 PC-Plus's ability to correctly reproduce the bass clarinet's melody. The Dutch percussion group Slagerij Van Kampen and their cd "Door" achieves almost perfection while being played with the aid of the SVS subwoofer. Absolutely wonderful. Does this mean we have no point of criticism at all? We do, but only one. It seems that the 25-31 PC-Plus 'lifts up' bass frequencies between 60 and 70 Hz (this is an estimation, we could be off by some Hz) a bit, so you can get a somewhat roaring effect while playing some pieces. Bass drums in pop music can sound a bit too powerful because of that. If that's a problem for you or not, will depend on your taste. We know quite a few people (and a lot of youths) who think such a sound is awesome. If a double bass sweeps over these frequencies and the subwoofer lets out some roaring, we would like that to be less. That's why we subtracted a couple of points on musicality.


    In one word: wow! This is without competition the best subwoofer we have tested thusfar, both for music and for home cinema. The PC-Plus model has way too much power for the average European living room, so you might want to look at the PCi model instead. You will find nothing on the European market that will sound better for that price.

    Johan Zwiekhorst.

    SCORES: SVS 25-31PC-Plus
    Musicality: 8
    Music reproduction Classical Orchestral: 9
    Music reproduction Solo instruments: 9
    Music reproduction Modern Pop/Rock: 10
    Film/Home theater: 10
    Acoustic Integration: 8
    Configuration: 10
    Construction & Finish: 9
    TOTAL: 73/80
    PERFORMANCE: 91,25%
    VALUE FOR MONEY: 90,63%

    Website: www.svsubwoofers.com
    Price: $379 for 25-31CS
    Price: $549 for 25-31PCi
    Price: $775 for 25-31PC-Plus
    You will have to convert this amount to euros (dollar and euro are more or less the same value) and then add (for Belgium) 3% import taxes and 21% VAT. The transport costs will set you back another 150 euros.

    Built-in amplifier: 525 W
    Inputs: low-level dual RCA + high-level stereo (filtering the main speakers' signal)
    Frequency range: 20-100 Hz, +/- 3 dB
    Low roll-off point: 25 Hz, adjustable to 20 or 16 Hz.
    Dimensions: cylinder 79 cm tall, 41 cm diameter
    Finish: black fabric
    Supplied accessories: power cable, two foam port blocking plugs

    1. dvd-video
    * Lord of the Rings: Fellowship of the Ring
    * Star Wars I: The Phantom Menace
    * Star Wars II: Attack of the Clones
    * U571
    * DTS demo disc #4
    2. dvd-audio
    a. Classical
    * Telarc DVDA-70541, Kunzel/Cincinatti Pops Orchestra: "Tchaikovsky - 1812 Overture"
    * Naxos DVDA-5.110001, Juritz/London Mozart Players: "Vivaldi - The Four Seasons"
    b. Modern
    * One Little Indian Records TPLP1O1DVD, Björk: "Vespertine"
    * Nonesuch 7559-79506-9, Philip Glass: "Koyaanisqatsi"
    * Warner 9362-48096-9, John Williams: music of the motion picture "A.I."
    3. cd
    a. Classical
    * Etcetera KTC 1250, Steven & Stijn Kolacny: "J. Brahms - Hungarian Dances"; Piano 4 hands
    * Chandos CHAN 9271; Felix Alexandre Guilmant, Symphony No. 1 for Organ and Ochestra Op.42 (I. Introduction and Allegro); Charles-Marie Widor, Symphony for Organ Op. 42 No. 5 (V. Toccata, Allegro); Francis Poulenc, Concerto for Organ, Strings and Timpani (I. Andanta)
    * Sony SK89183, Edgar Meyer: "Bach: Unaccompanied Cello Suites performed on double bass"
    * Telarc CD-80277, Michael Murray: "An Organ Blaster Sampler"
    * ASV CD DCA 626, Martin/Halstead/Fugelle: "Bottesini Vol.2" for double bass
    * BMG 05472 77515 2, Hille Perl: "...per la viola da gamba"
    * BMG 74321 8266 2, Günter Wand / Berliner Philharmoniker: "Bruckner - Sinfonie Nr. 8", Originalfassung
    * DICD 920178, Peter Benoit: "Hoogmis"; Alexander Rahbari conducts the BRTN Philharmonic Orchestra Brussels
    * Sony SK 89670, Yo-Yo Ma plays the music of John Williams; cello & orchestra; solo cello
    b. Modern
    * Dreyfus FDM 36164-2, Jean-Michel Jarre: "Metamorphoses"
    * Vertigo 546 797-2, Metallica: "S&M"
    * Arista 07822 19080 2, Carlos Santana: "Supernatural"
    * Sony 17-488590-10, Slagerij Van Kampen: "Door"
    * Sony SK 89191, Vangelis: "Mythodea" - Music for the NASA mission: 2001 Mars Odyssey
    * Universal 017 193-2, Willem Vermandere: "Omzwervingen - Liedjes zonder woorden"
    c. Special
    * Telarc20 CD-80342 "The Great Fantasy-Adventure Album", Erich Kunzel - Cincinatti Pops Orchestra
    * Telarc20 CD-84402-DTS "Telarc 5.1 DTS Surround Sampler"

    Receiver: Sony STR-DB940 5x 110W, DD5.1 + DTS
    Speakers: front Mission 774, center Mission m5c, rear Eltax Linear Response 6 Mk. III
    Dvd player: Samsung DVD-709, digital coax connection
    Cd player: Yamaha CDX-750E, digital optical connection

    Room 1: 50 m3, no carpets, most of the walls have furniture in front of them, no doors so open air flow to other rooms (total air volume in excess of 200 m3).
    Room 2: 100 m3, fixed carpeting "tapis plain", furniture leaves plenty of wall space free, access doors closed so no air flow to other rooms.
  2. terence

    terence Supporting Actor

    Nov 8, 2002
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    Glad you guys gave SVS a shot, great review.[​IMG]
  3. Edward J M

    Edward J M Cinematographer

    Sep 22, 2002
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    Excellent review! Very thorough, especially on the music end - great references for musical passages - thanks!

    The bump in the 60-70 Hz region was probably room induced, since the anechoic or quasi-anechoic FR curves show no such animal. Placement experimentation or a BFD might have tamed this.

  4. JohanZw

    JohanZw Auditioning

    Mar 29, 2003
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    I did think about room inducement, but the phenomena occurred in both rooms I tested the subwoofer in and moving the subwoofer about didn't make any difference. Still, I think the problem can be corrected with the aid of an equalizer. It wasn't a particularly serious problem, though. Enough to warrant a couple of points subtracted on musicality, but nothing to worry about.

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