Product Review

Thiel SmartSub SI-1 Subwoofer Integrator

Part II

February, 2005

John E. Johnson, Jr.


In Use

I tested the SI-1 with a pair of Thiel PCS speakers, a pair of Carver Platinum Mark IV quasi-ribbon speakers, and a Thiel SS2 subwoofer. The main system consisted of a McCormack CD transport and DAC, Lexicon MC-12B SSP, Balanced Audio Technology VK-5i preamplifier, and McIntosh MC-602 power amplifier. Cables were Nordost.

I used a variety of music and movie soundtracks described in the review of the Thiel SS2 Subwoofer.

You can obtain the parameters for various speakers by going to the following URL at Thiel:

This database lists the parameters for many brands and models of speakers. If yours is not listed there, you can send Thiel an e-mail request and they will get the parameters for you if they can.

For the PCS speakers, I used a Low Frequency Limit of 55 Hz (its 3 dB down point), a Sensitivity of 87 dB,  and a Low Frequency Extension of 20 Hz. For the Carvers, I set them at 20 Hz, 85 dB, and 15 Hz respectively. They were both set at Reflex.

What amazed me most was that the audio now sounded like a unit rather than a set of speakers and a subwoofer. The blend was uncanny. This was the case whether using a set of Thiels, in this instance the PCS, or speakers of another brand and type entirely (the Carvers are dipole ribbons, where sound comes out the front and back).

Keep in mind that the parameter settings can be changed to suit your listening preferences. The suggested ones in the database or specification sheets are just a starting point. You can change the parameter settings with the remote control while music is playing, and see what the effects on the sound are. (Remember, the Integrator is not an EQ unit - although that feature might be added later. It is designed to blend a subwoofer with the main speakers. EQ is a different matter entirely.)

As many of you know, I am a big fan of deep bass. I had tremendous fun with the Integrator, as it gives such huge control over how the subwoofer works together with the main system.

Instead of the Integrator, you can use the Thiel SS2 subwoofer with Thiel's passive subwoofer crossover unit, such as the PX02 (MSRP $350), which is a two-channel crossover (the PX05 is a five-channel version at MSRP $500). The PX02 is 2" H x 7" W x 6.5" D and weigh about 2 pounds. Each one is made specifically to go with the SS series and various Thiel speakers, such as the CS2.4s that we reviewed some time ago.

A photo of the PX02 is shown below. The bus bar on the left channel input is for when using one input channel. You would remove it if connecting both front left and right speakers. The XLR output goes to the SS2 XLR subwoofer input.

The Thiel passive crossovers provide much better integration between their subwoofers and speakers than the generic bass management of SSP and receiver sub-outs.

On the Bench

Here is a graph of the room response of the setup using the Thiel PCS monitor, SS2 subwoofer, and SmartSub Integrator. Notice that with just the PCS and no SS2 or Integrator, the response falls off sharply below 75 Hz. With the PCS, SS2, and Integrator, the response is flat(ter) all the way to 20 Hz with the Integrator Low Frequency Level set to -6. With it set to +6, the bass response is above the rest of the spectrum. The peaks and dips are due to the room. The next feature to add to the Integrator would be a 6 band Auto-EQ, with a microphone jack on the back panel. This would bring those low frequency peaks and dips - that most rooms have - under control.

If you like a lot of bass, you can certainly set it to +6, but the main point is that you can make it flat. I had a PCS sitting on top of the SS2 for this test, but you can put the SS2 wherever you want, and dial in the distances from the rear and side wall on the back of the SS2. So, between the SS2 and Integrator, you have as many specific electronic settings as have ever been available for a subwoofer.

I also used the SS2 and Integrator with a pair of Carver Platinum Mark IV quasi-ribbon speakers. Here, as with the Thiel PCS, blending was superb. Below is a room response curve. With just the Carvers and no SS2 or Integrator, you can see how the response falls off below 45 Hz, even though the Carvers have four 12" woofers in each speaker. Adding the SS2 and Integrator solved the problem, giving a flat response to 20 Hz.


Thiel's new SmartSub SI-1 Subwoofer Integrator is one of the most significant subwoofer technologies to come along in years. It's expensive, but worth every penny. Providing unheard of flexibility, it not only lets you get a flat low frequency response,  but allows you to accurately and seamlessly blend your Thiel subwoofer with various brands and models of main speakers. I can't imagine any home theater aficionado not wanting one of these.

- John E. Johnson, Jr. -

Copyright 2005 Secrets of Home Theater & High Fidelity

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