# Current (12.3) THD tests run on 20-39 PC+...?



## Vader (Jul 8, 2006)

Hi all,

I have been looking for FR and THD graphs for a 20-39 PC+ using the new 12.3 drivers. Iikka has results posted for a PB12 Plus/2 with 12.3 drivers, and since I have a pair of 20-39 cylinders, is that relatively close? Somewhere I read that the new 12.3 drivers are very close to the current Ultra driver (in the same vein as the new NSD driver being very close to the 12.2?), and I did find THD tests dated May, 2005 on a PC-Ultra cylinder over at AV talk. Thanx!


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## Blaser (Aug 28, 2006)

So difficult question that nobody has replied for more than 6 months. IMO, it is not possible to guess what would the THD graphs look like based on another driver... even if they are close enough in SPL capabilities. 

It is difficult to compare THD of dual 20-39 PC plus subs agains Illka's Plus/2 tests, as although both options have 2 * 12.3 drivers, they don't have the same power and enclosure volume.... but what should be expected is that for the same SPL levels, the dual 20-39 would have less distortion than the plus/2.

I think the 20-39 PC+ unit should be tested to have a precise idea. Maybe you can ask Tom V. to enlighten you on this!!

B Rgds
Blaser


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## Vader (Jul 8, 2006)

Based on explanations from Ilkka, Ed, and Ron over over the last few months, I have come to conclude the same thing: that I cannot use the PB12 Plus/2 as a guide (well, maybe a _rough_ one). Ilkka posted that he did test the 20-39 PC+ (12.2), but has not yet posted the results, which I am waiting for (at least, they will be very close to the 12.3 I am thinking). For now, I am using the results for the 25-31 cylinder (25Hz) as an approximate guide, just shifting the whole thing to the left to account for the lower native tuning frequency. In any case, it is only wanting to learn the most I can about my equipment and how to get the most from them...


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## Ilkka (Jun 8, 2006)

Though I will post the full results soon, here's a little preview for you. Add 6 dB if you have co-located duals. The 12.3 will be really close, probably around 1 dB more in upper bass range.


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## Blaser (Aug 28, 2006)

Hi Vader!!

Yeah you're right!! Even the PB12+ has not been tested by Illka... Let's wait and see the 12.2 driver results I'm impatient to see them also..

Hey Illka,

We are waiting impatiently!!Let's have the results :T 

Blaser


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## Blaser (Aug 28, 2006)

WOW!!!

Illka's fast like thunder!!!:bigsmile: I just clicked on the send button for my previous post and immediately saw Illka's graphs.... Excellent group delay behaviour Illka:bigsmile: 

Thank you!!


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## Blaser (Aug 28, 2006)

Ilkka said:


> Though I will post the full results soon, here's a little preview for you. Add 6 dB if you have co-located duals. The 12.3 will be really close, probably around 1 dB more in upper bass range.


Impressive to see that below 25 Hz, the larger enclosure/driver with a single driver gives same SPL as the dual driver sub!!!! Hence the benefit to go with duals!!

I think the 12.3 unit will have also 3-4 db less SPL at 20 Hz in the FR (compared to the db 12.2), but Max SPL will remain the same though:cunning: 

Blaser


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## Ilkka (Jun 8, 2006)

blaser said:


> Impressive to see that below 25 Hz, the larger enclosure/driver with a single driver gives same SPL as the dual driver sub!!!! Hence the benefit to go with duals!!


Yes, never underestimate the power of native tuning frequency. Also higher enclosure volume per driver helps to raise the efficiency. 


> I think the 12.3 unit will have also 3-4 db less SPL at 20 Hz in the FR (compared to the db 12.2), but Max SPL will remain the same though:cunning:
> 
> Blaser


No, both 12.2 and 12.3 will have almost identical frequency responses. Only the earlier 12.1 was different.


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## Blaser (Aug 28, 2006)

:surrender: Illka,

You're the best!!!!:bigsmile:


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