SVS SB12-Plus Subwoofer Review

[gene]

And thanks to all of those participating in the one sub versus multiple subs discussion. I'm getting the impression that two subs can be better than one if you know what you're doing and take the time to set them up (although the debate still continues on that), but one sub is easier to place "properly" and easier for the average person to set up.

If you can symmetrically locate the subs with respect to the listening position, its real easy. Then all you need is a Y-Splitter from your sub out of the receiver, and 2 rca cables to feed each subwoofer line level signal.

 

[MarkS]

Hello Ilkka

Thank you for bringing this to my attention!

In reviewing the anechoic response plots, they do indeed seem a bit higher than intuition (or a little bit of algebra) might otherwise indicate they should be.

I couldn't find any fault with the subsequent pre-publication data analysis. However, the response given by the facility (where the measurements were originally done) when queried about the plots revealed that a gremlin had, in fact, crept into the data.

The measurements were indeed done at 2m; that fact is correct as stated in the review. Unbeknownst to me at the time, however, this particular facility automatically scales 2m plots to 1m. So at the end of the day I walk out with a collection of what I believe to be raw, 2m plots, that were in fact already scaled to 1m. Hence the measurements that appear in the review.

I have since rescaled the plots and forwarded Gene a copy of the corrected manuscript. Sorry for any confusion caused by the scaling errors!

Best regards,

Mark

Good review although the measurements seem really weird.

They measured its maximum output in an anechoic chamber (means 4pi environment) at 2 meter distance. This equals with 4 m ground plane. Or with 2 m GP, but you have to add 6 dB.

And they got nearly 115 dB above 40 Hz? I'm sorry, but that is just impossible for a 12" with 425 W. Even at 2 m GP that would be some serious performance. There must be a some sort of error. In 4pi the yellow line would represent its max output much more closely (add 6 dB for GP).

Normally sealed 12" subs are capable of 105-110 dB in mid bass range (at 2m GP). These measurements show over 10 dB higher performance (118-121 dB)...? That would be more than PB12-Plus/2 and Ultra/2 are able to do at those frequencies.

I also echo ManicMiner's comment; I wish room gain compensation control would have been measured too.

 

[gene]

I have since rescaled the plots and forwarded Gene a copy of the corrected manuscript. Sorry for any confusion caused by the scaling errors!

Mark;

All of your changes have been made for the graph and additonal graph we posted on this forum yesterday.

 

[Buckle-meister]

...all you need is a Y-Splitter from your sub out of the receiver, and 2 rca cables to feed each subwoofer line level signal.

Knowing nothing about electrical signals etc, I'd like to ask; does splitting the single feed from the receiver into two cause each sub to 'see' half the signal strength that just one sub would've?

 

[jaxvon]

Knowing nothing about electrical signals etc, I'd like to ask; does splitting the single feed from the receiver into two cause each sub to 'see' half the signal strength that just one sub would've?

Aside from additional resistive losses due to the extra cabling, I don't think so. The Y-Splitter wires the subs in parallel, thereby halving the impedance seen by the pre-out. This results in both subs seeing the same voltage and current (theoretically). Or I could be insane, but this makes sense to me.

 

[gene]

Knowing nothing about electrical signals etc, I'd like to ask; does splitting the single feed from the receiver into two cause each sub to 'see' half the signal strength that just one sub would've?

No as Jaxvon correctly points out. It does however double the capacitive load and halve the impedance but the former is usually very low and the latter is usually very high so its a non issue for any competently designed receiver or processor. I have 4 subs run off a single subwoofer output of my processor.

 

[Buckle-meister]

Thank you Jaxvon/Gene.

I have two sub-outs available to me so this information will doubtless come in handy at some point in the future (I have but a single sub at present).

 

[jaxvon]

Thanks Gene. Good to see I've learned something here at college.

Robbie,

The capacitance will be a non-issue as long as you use high quality, "normal" cabling (like Belden, Canare, etc). If you use magic cables from, say, Mapleshade, you might have issues.

 

[Sheep]

Thanks Gene. Good to see I've learned something here at college.

Robbie,

The capacitance will be a non-issue as long as you use high quality, "normal" cabling (like Belden, Canare, etc). If you use magic cables from, say, Mapleshade, you might have issues.

I like the one that's wrapped in a clear plastic bag. Priceless.

SheepStar

 

[ggunnell]

The November '06 issue of Sound and Vision magazine has an article on page 42: "Why You Need Four Subwoofers" by Sean Greer. Sean does a good job explaining room modes and the sub placements suggested by the Harman papers, THX, and others.