Product Review - PSB Stratus SubSonic 3i Subwoofer (15") - October, 1998

John E. Johnson, Jr.



PSB Stratus SubSonic 3i Subwoofer

Sealed Enclosure - One 15" Driver - 2" Voice Coil - 40 Ounce Magnet

350 Watt RMS Amplifier

Manufacturer's FR Specs: 24 Hz - 150 kHz ± 3 dB

Size: 18" H x 17 1/2" W x 17" D

Weight: 54 Pounds

MSRP: $899 USA


PSB International, 633 Granite Court, Pickering, Ontario, CANADA L1W 3K1; Phone 905-831-6555; Fax 905-837-6357; E-Mail [email protected]; Web

Following our nice experiences with the PSB bookshelf speakers and one of their smaller subwoofers, we decided to take a look at their larger subwoofer, the Stratus SubSonic 3i. This unit has a 15" driver in a sealed enclosure, along with a 350 watt rms BASH amplifier. The BASH design uses a switching power supply that is much more efficient than conventional power supplies, meaning that less heat is dissipated, but more importantly, there is additional energy that can go to the speaker when music and movie sound tracks demand it.

The 3i is not really very big as far as 15" subs go, but it is big enough. It has a black matted wood top, and the rest of the enclosure is surrounded by a black knit sock which is pulled over the enclosure, tightened, and knotted at the bottom after attaching the plastic feet. This keeps the cost down ($899 is not very much money for a sub of this power), yet the subwoofer has an attractive look to it.

The rear panel has a toggle on/off (standby/auto-on) switch, a non-detachable ungrounded AC cable, rotary controls for volume and low pass frequency (50 Hz - 150 Hz), PSB Stratus SubSonic 3i Panela phase toggle switch (00 or 1800), one pair of input line-level RCA jacks (left/right), one pair of high-pass (> 80 Hz) output line-level RCA jacks (left/right), one pair of speaker-level input five-way binding posts, and one pair of speaker-level high-pass (> 80 Hz) output five-way binding posts.

We tested the 3i in our audio and home theater labs using many of the reference components listed on that page.

I was immediately struck with the fact that the 3i has a very tight bass, rather than a rolling sound. This is a little bit unusual for a subwoofer with such a large driver, and is more characteristic of subs with several smaller (e.g., 10") drivers. I am not quite sure how Paul Barton keeps the driver under such control, but nonetheless, it is there. I know he has spent a tremendous amount of time at the National Research Council Facility in Ottawa, Canada, testing drivers and enclosures. Obviously, that research time has produced results. One possible reason (among several) is that the system rolls off sharply below 25 Hz and is down by about 10 dB at 20 Hz (see chart below).

With music, the 3i blended seamlessly to the other speakers. Occasionally, subwoofers will sound "separate" from other speakers, but not the 3i. This may have to do with the tightness.

Using our DVD collection, I found the 3i capable of maintaining its poise with the best of them. "Lost in Space" has some great special effects both in the video domain and the audio. The 3i punched out explosion after explosion, rocket engine roar after roar, with no strain. It doesn't move air like the $2,500 subwoofers, but for $899, it moves more than its share. It has an excellent limiting circuit that keeps things under control, so that if you should get overeager with the volume control, the bass will not get out of hand, but rather, attains a high level without going any higher even if you turn the volume control up further (prevents clipping).

Room Response - PSB Stratus SubSonic 3i Subwoofer -- Set to 90 dB at 25 Hz -- (This is not maximum output, but rather just the response in an "average" room with the volume set to 90 dB at 25 Hz.)
1 meter 13 feet
10 Hz 61.0 dB 10 Hz 59.3 dB
12.5 Hz 66.8 dB 12.5 Hz 69.9 dB
16 Hz 66.1 dB 16 Hz 72.6 dB
20 Hz 72.7 dB 20 Hz 83.4 dB
25 Hz 89.9 dB 25 Hz 90.3 dB
31.5 Hz 96.7 dB 31.5 Hz 87.0 dB
40 Hz 97.7 dB 40 Hz 97.6 dB
50 Hz 90.9 dB 50 Hz 89.5 dB
63 Hz 101.4 dB 63 Hz 95.5 dB
80 Hz 101.3 dB 80 Hz 97.0 dB
100 Hz 98.4 dB 100 Hz 101.8 dB
125 Hz 93.7 dB 125 Hz 84.4 dB
160 Hz 87.7 dB 160 Hz 86.2 dB

I found a maximum output of 104 dB at 31.5 Hz (1 meter), which is very reasonable. As you can see, the 3i shows a considerably flat room response down to 25 Hz, after which, there is a steep rolloff. In general, subwoofers are not damped internally with wads of stuffing, so the enclosure can be a little boomy. As with other subs, I found the most pleasing effect by setting the 3i low-pass to 50 Hz - 60 Hz. This prevents chestiness and boominess that creeps in when low-pass settings of 120 Hz are used.

In summary, I am very pleased to see that Paul Barton continues to make great products at entry-level prices. The PSB Alpha bookshelf speakers astounded everyone (including me) when they were introduced several years ago at $199 the pair. In the $500 to $1,000 range, the Stratus SubSonic 3i Subwoofer is one of the best we have seen, and it should be on your list of items to check out when shopping for the big whammy.

John E. Johnson, Jr.

© Copyright 1998 Secrets of Home Theater & High Fidelity
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