# PB12-ISD compared to PB12-Ultra/2 ?



## Malice (May 1, 2006)

I suppose this is more aimed at TomV than anyone else, but please feel free to chip in!

Not being able to demo an Ultra/2 and compare to my existing ISD, what would you say the significant differences are in terms of performance and sound quality? My room is 21' 6" x 17' 6" so can withstand (or needs) a capable sub. I have to admit that more recently I am enjoying listening to multi-channel audio/music CDs/DVD's and was wondering if an Ultra/2 may be worth an upgrade (there is a S/H one for sale over on AV Forums in the UK).

:T 

Bob


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## khellandros66 (Jun 7, 2006)

Is your ISD a dual driver loaded one??

If so then there will be a gain in SPL at the lower and upper octaves bost most improvements will be 25Hz and down in terms of SPL. I also believe the Ultra uses a more robust BASH amp that is cleaner and more efficient. The ISD drivers are probably 2-3dB lower in terms of SPL. This doesn't mean its a bad driver but a mechanical limit compared to the Ultra Drivers.

If you have the single driver ISD then the difference will be very noticible. Not only would each driver be about 2-3dB louder but the combined two would also double that added gain, so a total of about 4-6dB louder. Remember that the amout of volume you perceive doubles every 3dB.

~Bob


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## Otto (May 18, 2006)

khellandros66 said:


> Remember that the amout of volume you perceive doubles every 3dB.


Hi there,

Actually, the amount of volume perceived doubles with an approximate 10 dB increase in measured volume. I think that's a widely accepted translation, as it's really impossible to measure this since it's based on human perception. 

It takes a doubling of amplifier power to garner a 3 dB increase in SPL.


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## Malice (May 1, 2006)

Thanks for the input. IHowever, as far as SPL is concerned, if the system is balanced properly then 85db SPL on my single ISD driver, will be the same as 85db on the Ultra/2 drivers, but it will be the high SPLs which could benefit where there are large transient SPLs which a sub with more "headroom" will handle more adeptly.

The Pb12-ISD (single) I have also has a BASH amplifier and I wasn't aware that in efficiency terms it would be any different to the Ultra BASH amplifier. But perhaps a comment from Tom may shed some light on that one.


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## Sthrndream (Apr 21, 2006)

Hi all,

Search on "fletcher munson" and you find the "equal loudness curves". The way humans perceive a "doubling" of volume is based both on the frequency and the SPL. IIRC, it can vary between 2dB and 10dB. 

The sound quality between a PB12isd and a PB12Ultra/2 may seem very similar at lower volume levels. But the louder the bass, the more the Ultra/2 will separate itself and offer very real audible benefits. In regards to output capabilities, it would take about 2.5 PB12isd subs to match a single Ultra/2

Tom V.
SVS


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## Malice (May 1, 2006)

:T


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## lienly (Sep 4, 2006)

hello all, happy pig new year.

12NSD, 325w, $600.
ultra2, 1000w, $2000+.

really big differences in both $ and power:whistling: 



Tom Vodhanel said:


> In regards to output capabilities, it would take about 2.5 PB12isd subs to match a single Ultra/2
> 
> Tom V.
> SVS


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