# 16-46 vs. 20-39 in 12hz tune (plus models)



## mike c (Apr 25, 2006)

I realize that the 20-39 plus is the match for the PB12 Plus box.
I also realize that it is NOT recommended to use two port bungs to lower the tune too much.

BUT

what's the difference between a 20-39 with two port bungs and a 16-46 with one port bung (both tuned to 12hz)?

does that mean the 16-46 plus is better than the PB12 Plus? (can go lower with more output)?


oh and btw, on the AVTALK test of the 20-39 at 12hz tune ... it was still going at 10hz, at what frequency does it start to fall off? will there be a difference in the 16-46?


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## Ed Mullen (Jul 28, 2006)

mike c said:


> I realize that the 20-39 plus is the match for the PB12 Plus box.
> I also realize that it is NOT recommended to use two port bungs to lower the tune too much.
> 
> BUT
> ...


The 16-46 cylinder size (both PCi and PC-Plus) is unique in the SVS line-up in that it is designed from the outset to play in the 13-17 Hz bandwidth more efficiently than any other model we offer. It is usually only recommended for customers who are interested in 32' pipe organ music, or for those who simply want to capture virtually all of the infrasonic bass present on DVDs even if it only occurs for a few seconds over the entire movie. 

While the 20-39PC+ and the PB12-Plus can be retuned to 16 Hz, they do sacrifice some output capability in the process because retuning involves plugging one of the three ports. So the 20-39PC+ tuned to 16 Hz will not play quite as loud/clean in the 13-17 Hz region as would the larger 16-46PC+ with all three ports still open. Conversely, the 20-39PC+ in its native tune with all three ports open will play louder than the 16-46PC+ over the more common bass regions above ~20 Hz. There are always output/extension trade-offs involved when you alter Fb (the system tuning frequency).

The upshot is that either the 20-39PC-Plus or the PB12-Plus configured for the 16 Hz tune will provide a good facsimile of a 16-46PC-Plus except at very loud playback levels, where the extra port area and larger enclosure volume of the 16-46PC-Plus allow it to play louder/cleaner in the 13-18 Hz region.

We don't recommend running the 20-39PC+ or the PB12-Plus in the 12 Hz tune at high volumes - the tuning frequency is so deep that the woofer must shoulder the entire load all the way down to about 15 Hz before the resonators start to assist in output. Ditto for the 16-46PC+ - while it still retains dual 3" ports in the 12 Hz tune, it still has the same tuning point and the woofer still must handle everything down to ~15 Hz. 

Since woofer excursion requirements quadruple with each successively deeper octave, you can appreciate that a single 12" woofer - even one as capable as the 12.3 - will eventually run into excursion related compression at high playback volumes if asked to handle all frequencies down to ~15 Hz. 

To answer your specific question, the 12 Hz tune has a high pass filter which kicks in around 10 Hz, so that is about the limit of the quasi-anechoic extension in the 12 Hz tune. In-room extension into the single digits is possible with the 16-46PC+ in the 12 Hz tune - just don't push it to very high playback levels unless you are planning on duals.


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## mike c (Apr 25, 2006)

thanks Ed!


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