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PB1-ISD review (1 Viewer)


Mar 29, 2003
Hi guys,
I haven't visited this forum for quite some time now. It seems you found my Dutch-language review for the PB1-ISD on diskidee.be or diskidee.nl. I'm sorry I couldn't get a translation to you any sooner, but here it is...

© 2004 by Johan Zwiekhorst, Belgium

SVS PB1-ISD subwoofer

Small cube with big sound

Streamer: SVS is an American brand of subwoofers which makes only that kind of speakers and sells them exclusively via the internet. We have reviewed a cylindric model of them before and were very impressed. Now a cubic-shaped subwoofer is on our testbench: the smallest one SVS has to offer. Is that one as good?

Full text: Most people were confronted for the first time with a subwoofer when home cinema systems became more commonplace. Those subwoofers, however, prove to be boom boxes more often than not and these are totally incapable of enhancing music. If you want an ordinary speaker to deliver really deep low frequencies, you need a big box. You can't get around that. The smaller the box, the less equipped it is to generate low frequencies. That has to do with moving air. Low frequencies come with a certain volume of air that is brought into motion and that means there is sound pressure. You can only do that if the conus of your driver has a diameter that is big enough. Think of 25 to 30 cm (10 to 12 inches). The larger the conus diameter, the more impressive the low frequency reproduction will be. The big problem here is, that not everyone has the room to place these really big boxes, especially if you need at least two of them. In a surround system, there can even be four or more. On top of that, your amplifier has a serious disadvantage: it will have to spend about 95% of its energy on generating lows and that leaves only 5% for mid and high frequencies. You can get around all of these difficulties by using a subwoofer.

Separating lows

We have two ears so we can determine the direction of sounds. That's stereo hearing. As it turns out, the directional sensitivity of our hearing decreases with frequency: that means we can't tell which direction a sound is coming from if its frequency is below, say, 80 Hz or so. This is a handicap of our hearing, but it turns out to be an advantage when we go shopping for speakers because it means we don't have to buy big boxes. We simply have to split off all of the low frequencies and divert that to one single loudspeaker that will handle just the lows: the subwoofer. So our main speakers will only need to be able to reproduce tones down to about 60 or70 Hz (to be on the safe side). Did you know that even bookshelf loudspeakers (very small speakers which have to be put on stands to get them to ear level) of reasonable quality can accurately reproduce tones of 60 or 70 Hz? That means that going shopping for main speakers just became a whole lot easier. No need to go for the big boxes, because you're no longer interested in how good they reproduce bass: that's why you have a subwoofer! So look for speakers who are really good in reproducing high notes, mids and higher bass down to some 60 or 70Hz. If your partner would like small bookshelf speakers so they'll be visually less intrusive, that's no longer a concern. Modern slim and thin floorstanders are no problem either. Your WAF (Wife Acceptancy Factor) will rise to new heights. As an added benefit, your amplifier doesn't need to be as powerful anymore. So you see: there are lots of advantages to using a subwoofer. The main trick is integrating the subwoofer with your mainspeakers so they create a complete and coherent sound image. That means you shouldn't be able to hear where your main speakers leave the lows to your subwoofer: the transition should be smooth and the timbre shouldn't change much or at all.


At this time, SVS has an entire collection of cube-shaped subwoofers, besides their cylinder-based models. The cubes range from small to large. The PB1-ISD we're reviewing here is one of the smallest, while the largest one is called B4-Plus and contains no less than four drivers! 'PB' stands for 'Powered Box', by the way, and that means that there's an amplifier built into the box. If the name contains only the letter 'B' in front, that means there's no amplifier built in and you have to provide one yourself. A subwoofer without a built-in amplifier is called a passive subwoofer; one with a built-in amplifier is an active subwoofer. The following number indicates the number of drivers in the box: one, two or four. Next, there's a hyphen and then 'ISD', 'Plus' or 'Ultra' and that indicates the type of driver(s) used in the box. The 'ISD' is the 'Improved Standard Driver' which was custom-made for SVS and has a kevlar cone. The 'Plus' is a TC-Sounds db12 driver with an aluminum cone and the 'Ultra' is a high-performance driver of the same manufacturer and it has an aluminum cone as well. The cubes are constructed in such a way, that vibrations from very low frequencies are prevented as much as possible. They are made out of high density fiber materials and feel extremely rigid. If you knock on the box, you hear nothing but your knuckles hitting something completely dead (acoustically spoken). The finish depends on the model. The PB1-ISD has a polyurethan finish which looks like texture paint - in this case black, but for $50 more you can get three other colors. Like the cylinder models, the driver radiates towards the floor and to prevent your floor being used as a sounding board, SVS has mounted a base plate there. That means the sound has to travel from between the driver and the base plate into your room. That way, you don't need spikes and you get perfect thunderous bass even on wooden floors or carpets. The PB1-ISD has one port at its back and SVS has tuned it to 22 Hz. The built-in amplifier is the same one from the PCi cylinder series and has a power rating of 320 W.


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, we can say 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. 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. Now 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 mastervolume!) until each speaker - including the subwoofer - measures 75 dB. Furthermore, you will need to configure the distance of each speaker to your listening position: this way, the amplifier can use a time-delay for each speaker, ensuring that the signals from all speakers reach your ears at the same time. That's about it: now you can play music and films.

Integration in a stereo system

If your surround amplifier is of the kind that uses its subwoofer output only for the LFE channel (LFE = Low Frequency Effects) on dvd's and is incapable of diverting low frequencies from your main speakers to your subwoofer, you will have to make sure yourself this happens. The same applies if you want to integrate your subwoofer into a conventional stereo system, because standard stereo amplifiers usually won't have a subwoofer output. SVS took these circumstances into account and so SVS subwoofers have two kinds of connections: a low-level connection for the subwoofer output of an amplifier and high-level connections for your main speakers. That means an SVS subwoofer has eight loudspeaker connectors: input and output for left and right and for each a positive and a negative connector makes eight in total. It works as follows: connect your mainspeakers not to your amplifier, but to the output connectors on your subwoofer. Then, connect the subwoofer input connectors to the speaker connectors of your amplifier. Yes, you neeed a second set of loudspeaker cables for that. This way, the loudspeaker signal passes from your amplifier through your subwoofer before reaching your speakers. This allows your subwoofer to function as a low pass filter: it will separate all the lows and keep them to itself while sending all the higher frequencies to your main speakers. All you need to do is control at which crossover frequency the subwoofer will start to keep the lows for itself. You can determine which crossover frequency is best and how loud your subwoofer should play by ear, or you can experiment with the aid of a sound pressure level meter. The higher your crossover frequency, the easier your main speakers' job will be and the better they will play the higher frequencies. In fact, redirecting all low frequencies to your subwoofer pretty much has the same effect as if you would have bi-amped your main speakers. When your have configured your subwoofer crossover frequency and output level correctly, you should be able to have your system play a continuous tone from, say, 200 Hz downto 20 Hz and your loudspeakers and subwoofer configuration should play this seamlessly from beginning to end and without you being able to hear where the crossover point is between your main speakers and your subwoofer. If you can tell where that transition occurs, you either haven't configured your system properly yet or your crossover frequency is much too high.


As far as acoustic integration is concerned, the SVS PB1-ISD is almost on par with its bigger brothers, safe one item. The PB1-ISD doesn't have a continuously adjustable phase control: you can switch it between 0 and 180 degrees, that's all. Whether this presents a handicap, depends on where you have located your subwoofer. If you put the subwoofer close to your main speakers or at the other end of the room, a switch will usually suffice. A continuous phase adjustment would be more advantagious, however, if you want to place your subwoofer elsewhere in the room. In our test setup, we had located the PB1-ISD right next to our right front speaker. The correct phase setting turned out to be 0 degrees, so we didn't have to flip the switch. The most important question is, of course, how does it sound? As always, we have evaluated the performance of the subwoofer for both movies and music. To that end, we let just about everything we had loose on the PB1-ISD. You can find a list of all films and music we used at the end of this article. As it turned out, the PB1-ISD has just about the perfect power for our listening room: the subwoofer's gain ended up turned about half-way while the subwoofer output of our surround amplifier was set to -5 dB. After that, we just had to turn up the main volume to end up with a sound pressure level of 75 dB.


We didn't expect the sound picture created by the PB1-ISD to be virtually identical to the one from its big brother SVS 25-31PC-Plus which we tested before. The explosions of the depth charges in U-571, the thunderous moves of the balrog demon on the bridge of Khazad Dûm in Lord of the Rings, the roar of tanks, ships, airplanes and spaceships all sound as impressive as with the 25-31PC-Plus subwoofer. That is no small feat, since that one was the best we ever heard in that price category and far beyond that. This PB1-ISD manages the same for even less money! Yes, it does have less power (320W versus 525W for the 25-31PC-Plus), but it didn't need more in our test setup!


What about music performance, however, especially if you want the subwoofer to take over all the lows from your main speakers (even smaller ones)? We paid particular attention to this aspect in our test of the SVS PB1-ISD. The best subwoofer for music we have heard thusfar came from the English brand REL (see rel.net).Well, REL can expect some very stiff competition because SVS offers a subwoofer that is at least as good for a whole lot less money! Whether the PB1-ISD has to deliver the violence of the lowest pedals of a church organ or the more subtle low notes of a cello, it does so without even straining itself. Even the very difficult double bassnotes in Norah Jones' song "Cold Cold Heart" came through sounding just like a double bass should sound when its strings are plucked. And if Diana Krall reaches her voice's lowest notes, the PB1-ISD manages to give her just a little more spaciousness and presence. Of course we also performed our bass clarinet test: we played the instrumental track "Diepe adem" from Willem Vermandere's album "Omzwervingen" with the main speakers switched off; so the subwoofer has to carry the entire melody. Just like its big brother, the PB1-ISD passed this test with flying colors. The low piano notes in the Rachmaninov piano concerti got just the extra weight they needed to convince us that an actual concert piano is playing in our listening room. We couldn't find one single point of criticism. Whatever we let loose on the subwoofer, it handled it marvelously. Last time, we subtracted some musicality points for the SVS 25-31PC-Plus because it emphasized a certain frequency range a bit too much (something we have been able to correct, by the way, by blocking two of the 25-31PC-Plus' three ports). The PB1-ISD had no such problem.

What about electrostats?

Electrostatic loudspeakers are notoriously difficult to integrate successfully with a subwoofer, so we decided to try that as well. We decided to use Audiostatic ES-300 and Audiostatic ES-100 electrostatic loudspeakers (see audiostatic.com for more information), the Sony STR-DB2000 digital surround receiver (6x120W) and the Pioneer DV-668A universal dvd player (which means it can also do dvd-audio and sacd). The reason the marriage between an electrostatic loudspeaker and a subwoofer is so difficult, has to do with the very different method for generating sound by the two speaker systems. Conventional speakers are also called dynamic speakers: they use a paper cone to move air. At the end of that paper cone, there's a funnel-like extension with a coil wrapped around it. Behind that coil, there's a magnet. When you apply power (like the output from an amplifier) to the coil, it will generate an electromagnetic field and that will be attracted or repelled by the magnet. Since the coil can move and it is fixed to the paper cone, the cone will move as well and thereby move air, thus generating sound. SVS subwoofers are dynamic speakers as well and so use this method to produce sound. The big problem with the paper cone system is that it has quite a lot of mass. That means moving it back and forth costs energy. Furthermore, this way of generating sound comes with a fairly high level of distortion. Electrostatic speakers work quite differently. An electrostatic speaker or ESL (= ElectroStatic Loudspeaker) consists of a very thin membrane suspended between two stators. A stator is a metal plate with lots of holes in it or a fence-like structure of wires. You apply a high voltage to the membrane, which is charged electrostatically (hence the name of the entire speaker system). Then you use a transformer to multiply your amplifier's music signal to several thousand volts and apply the positive side to one stator and the negative side to the other stator. That means the stator will have an electromagnetic field wich will either attract or reject the membrane, thus moving air and producing sound. Because the membrane is so thin, its mass is very low. That also means it produces very little distortion while generating sound. Furthermore, the ESL is extraordinarily fast. The question is: can a subwoofer keep up? To keep a long story short: the SVS PB1-ISD can! Because we used full-range electrostats, we could set the crossover frequency for the subwoofer relatively low: we selected 90 Hz. It would be extremely difficult to marry the sound characteristics of the subwoofer with those of an ESL if the crossover is set higher than, say, 100 Hz. The higher the crossover, the better you can hear the distinction between the ESL and the conventional woofer. That is also the reason why many so-called hybrid ESL systems (an ESL for the midrange and treble plus a conventional woofer for the lows) don't work very well. However, the SVS PB1-ISD proved quite easy to integrate with the Audiostatic speakers and it ended up extending the Audiostatic's lows while we couldn't hear the transition. Our hats off to SVS: this is quite an accomplishment!


This cube with sides of almost half a meter each does the name SVS justice on all counts. The sound quality is just as good as that of its bigger brother. If your room isn't too large, you will find nothing that sounds better for this price and a lot more - except perhaps the SVS 25-31PCi which is even cheaper. Not everyone will want a cylinder in their living room and then a cube may present a better choice. I don't know of any subwoofers sold in the European Union (whether they are European, American or Asian brands) that come anywhere near this SVS PB1-ISD in terms of value for money.

Johan Zwiekhorst.

SCORES: SVS PB1-ISD (max. 10 points)
Musicality: 9
Music reproduction Classical Orchestral: 9
Music reproduction Solo instruments: 9
Music reproduction Modern Pop/Rock: 10
Film/Home theater: 9
Acoustic Integration: 7
Configuration: 9
Construction & Finish: 9
TOTAL: 71/80

Website: svsubwoofers.com
Price: $599 for PB1-ISD in black
Price: $649 for PB1-ISD in other colors (grey, tan, gold and white)
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: 320 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: 22 Hz, not adjustable.
Dimensions: 53 x 46 x 51 cm (HxWxD)
Weight: 35 kg
Finish: black textured polyurethane (four other colors available for $50 more)
Supplied accessories: power cable

1. dvd-video
* Lord of the Rings: Fellowship of the Ring
* Star Wars I: The Phantom Menace
* Star Wars II: Attack of the Clones
* U-571
* 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"
* Teldec 4509-94545-9, Zubin Mehta/Israel Philharmonic: "Mahler - Symphony No. 2 in C minor "
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 X10078(2), Earl Wild (piano) + Jascha Horenstein / Royal Philharmonic Orchestra: "Rachmaninov - Piano Concertos etc."
* 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, Alexander Rahbari/BRTN Philharmonic Orchestra Brussels - "Peter Benoit: Hoogmis"
* Sony SK 89670, Yo-Yo Ma plays the music of John Williams; cello & orchestra; solo cello
b. Modern
* Verve 589 597-2 (hybrid sacd), Diana Krall: "The Look of Love"
* Blue Note Records 7243 5 32088 2 0, Norah Jones: "Come Away With Me"
* Dreyfus FDM 36164-2, Jean-Michel Jarre: "Metamorphoses"
* Vertigo 546 797-2, Metallica: "S&M"
* Vertigo 824 499-2, Dire Straits: "Brothers in Arms"
* 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
Subwoofer: SVS PB1-ISD, low-level analog connection: Bettercables Interconnect (subwoofer interlink 15 m)
Dvd/sacd player: Sony DVP-NS930, digital coax connection, 5.1 analog connection (with Oehlbach Blue Magic 5.1)
Dvd player: Samsung DVD-709, digital coax connection
Cd player: Yamaha CDX-750E, digital optical connection

Receiver: Sony STR-DB2000 6x 120W digital amplifier
Speakers: front Audiostatic ES-300, rear Audiostatic ES-100
Subwoofer: SVS PB1-ISD, low-level analog connection: Bettercables Interconnect (subwoofer interlink 15 m)
Universal dvd/dvd-audio/sacd/cd player: Pioneer DV-668A, digital coax connection, 5.1 analog connection (with Oehlbach Blue Magic 5.1)

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)

Edward J M

Senior HTF Member
Sep 22, 2002
Thanks for taking the time to post that informative and thorough review, Johan.

We all enjoyed your prior review of the 25-31PC+, and it's nice to see that the ISD driver can (in your opinion) provide just as good sound quality as the dB-12 Plus driver when operated within its clean limits.



steve nn

Senior HTF Member
Jan 12, 2002
Nice review Johan and it's always nice to see another.

Your review brings to light a recent experience I just had with a SVS product, that being the PB10-ISD. I never would have thought that it's performance capability would come in at such a high threshold. With having owned other dB-12/TV-12 Ultra SVS products (still do) it has given me a little wake-up call concerning their entry level offerings. I guess what I mean to say is their standard/bar for entry level is quite high and it correlates with your experience with the 12-ISD--dB-12 driver.

If a guy has decent in-room gain and listens at a -15 give or take about level. I can see the PB12-ISD doing it's job in a much larger room than previously thought of.

Jeffrey R

Stunt Coordinator
Feb 5, 2002
Good write-up. Although I am unsure why you describe the PB1-ISD (now PB12-ISD) as not having a continuous phase control. My PB1-ISD has a continuous phase control from 0 degrees to 180 degrees, not the flip switch you describe.


Mar 29, 2003
Hi Jeffrey,

The model I was reviewing didn't. Here's a photograph of the back panel: (it seems I can't post a link, so you'll have to copy & paste this URL: ) svsubwoofers.com/images/PB1ISD/s300ishothr.jpg. As you can see, there's a phase switch, not a continuous control.


Supporting Actor
Sep 2, 2000
Hmm, it seems Johan is correct. That is the picture of the amp currently on the SVS site
for the PB1-ISD (PB12-ISD). You mean SVS used to have a continuous phase adjustment knob
on the PB1-ISD amp, but then removed it in amps produced later? That doesn't seem likely, as SVS
doesn't normally remove features already offered in it's subwoofer models, if anything, it adds them.

Jeffrey R

Stunt Coordinator
Feb 5, 2002
Wierd. Well, my PB1 definitely has a continuous phase adjustment knob. If I knew how to post a picture of my amp, I would. But the amp in that picture Johan linked to is very much different from my amp. From left to right, my amp has gain knob, phase knob, auto on/off switch and crossover knob and on/off crossover switch. There's got to be other PB1 owners out there who can chime in. Or maybe Ron or Tom can clear this up.


Jun 2, 2001

The PB12-ISD (new name for this sub) has had a continuously variable phase control for quite some time now. It's one of the running upgrades we've made over the years. Especially for dual sub installations this feature has long since been viewed as critical by SVS. Most reviewers seem to agree with us on that now.

We even have an old picture up on the site still so I sure can't fault Johan here. I think my last round with our staff photographer captured one though so I'll see if I can't (finally) get that updated this week.


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