Differences between SVS dB12.1 and dB12.2 drivers

[Ilkka]

There was some discussion regarding SVS' older and newer Plus series drivers in Craig's SVS/HSU thread and since I didn't want to hijack that thread again (!), I decided to open my own.

I'll post a quote from that thread first.

For those looking at a direct comparison to the SVS ... Here are the numbers on the pb12-plus. One area of interest - it was always said that the "Plus" was about 1.5 to 2 dB lower in SPL than the Ultra. Based on some recent tests, the "new" (12.2) plus delivered about 4 dB more SPL than the old (12.1) Plus, in SPL below 22 Hz ... just something to keep in mind.

Since I have measured both the older dB12.1 and the newer dB12.2 (both subs were 20-39PC+ cylinders), I can give a little bit more accurate info than the generalization above. First of all, we can't just look at the difference at certain frequency. We have to look at the whole range from 20 Hz up to 100 Hz. Below 20 Hz both subs will drop pretty fast in 20 Hz tune, so no point comparing that data, though dB12.2 is a little bit stronger there.

This first graph shows three frequency sweeps. The sweeps went from 100 Hz to 10 Hz and were 45 s long, meaning they would heat up the voice coil real good. These three sweeps were the three highest ones sub could produce without compressing totally. This first one is for the older dB12.1 driver.

And here are the same three highest sweeps for newer dB12.2 driver. Notice how the actual shape of the curve is different. Older driver produces more straight line and then straight drop, when the newer is one much more rounder and extends a little bit deeper.

You can calculate the SPL at different frequencies by yourself, but I already did it and put them in a table. The same table shows also maximum SPL with single sine waves, when THD was max 10%. Notice how the max levels are actually higher at some frequencies with single sine waves than with a long sweep (VC heats up more).

When looking at the table, it's pretty obvious that regarding only max SPL, both drivers are very similar, only 0.5-1 dB differences here and there, but not a constant difference. Only when THD is limited to 10%, differences go larger. Near tuning frequency at 20 Hz and higher at 80 Hz the newer dB12.2 is much more stronger than the older driver. But I highly doubt if anyone could hear this difference with a program material.

So how about Ultra then? It's still the same 1.5-2 dB stronger below 50 Hz than it has always been.

 

[craigsub]

As I had a pair of PB2+ here, and could also never get them to audibly distort until they actually "bottomed", it would appear from this info that the "10% THD" number is pretty much meaningless.

Over the weekend, when I get time, I will try to pull the archived info from my 2004 PB2+ test.

 

[Ilkka]

As I had a pair of PB2+ here, and could also never get them to audibly distort until they actually "bottomed", it would appear from this info that the "10% THD" number is pretty much meaningless.

As you said to Mark Seaton... Sometimes we have our differences. This is not one of those times...

 

[---k---]

Thanks. I find that interesting. The resoning behind the results is a little over my head. But, I find it really interesting that that DB12.1 appears to have more total output capacity. And that the DB12.2 only has more distortion limited power at only 20hz and 63hz; all other frequencies appear to be pretty much equal.

Not what I had expected based on the rumors of how much better the DB12.2 reportedly was.

Can you give us any idea of what the output looks like if it were limited to like 20% distortion? Or, what was the distortion at the max output level? Did the new DB12.2 have less distortion there?

I'm just not sure that looking at distortion onl at 10% gives the whole picture. I would like to see an average distortion. Or something that would give an idea of what happens if you keep pushing.

 

[---k---]

Hey, how can the they have more output when limited to 10% distortion than the max? What did I miss?

 

[Ilkka]

Thanks. I find that interesting. The resoning behind the results is a little over my head. But, I find it really interesting that that DB12.1 appears to have more total output capacity. And that the DB12.2 only has more distortion limited power at only 20hz and 63hz; all other frequencies appear to be pretty much equal.

Not what I had expected based on the rumors of how much better the DB12.2 reportedly was.

Can you give us any idea of what the output looks like if it were limited to like 20% distortion? Or, what was the distortion at the max output level? Did the new DB12.2 have less distortion there?

I'm just not sure that looking at distortion onl at 10% gives the whole picture. I would like to see an average distortion. Or something that would give an idea of what happens if you keep pushing.

You are completely right, looking at 10% THD doesn't give us the whole picture. That's why we have developed so called "THD sweeps", which will be used in the future tests. They will show the amount of THD at both low/mid and high (max) output level.

But it is almost impossible for me to start guessing the output at say 20% THD, because THD isn't the most predictable variables there is.

 

[Ilkka]

Hey, how can the they have more output when limited to 10% distortion than the max? What did I miss?

If you look closer, you'll see that I did mention this.

But it is due different test signals. Sweeps were taken with a 45 second long sweep from 100 Hz to 10 Hz. That is probably the most excruciating test for VC that I can think of. VC has to stand and dissapate a LOT of heat during that sweep. We all know that normal effiency for a subwoofer is only around 1-2%.

<10% THD numbers were taken with a single sine waves, which usually didn't last more than 3-5 second. So it is possible that subwoofer can output sometimes more SPL in this test at certain frequencies.


Hey, why Craig's comparo was locked??

 

[---k---]

Some of us arn't smart enough to catch it all the time.

Possibly this should be my new sig line:
"Looking for a used copy of 'Idiots Guide to Subwoofer Design, Testing, & Evaulation. PM me if you have a copy for sale. "