Subwoofer Sensitivity

maka78 · Post by **maka78** » Mon Sep 29, 2008 8:59 am

So I'm trying to understand the subwoofer sensitivity idea...

What I'm getting from my research is that the sensitivity is how many dB a speaker can create 1 meter away from it with 1 watt of power.

When I look up the TI12D Elite subwoofer, I see that the sensitivity is 86.16 dB, but it has a (2.83V) next to it. What does the 2.83V mean?

Just looking up the cyclone to compare, I see it has 90 dB of sensitivity for 1w/1m but does not mention anything about voltage.

Does this also mean that the cyclone is more than twice as loud than the TI12D for the same input power (86 vs 90 dB)?

Post by **Bfowler** » Mon Sep 29, 2008 9:10 am

2.83 volts is listed so you know what ohm laod the sub was tested at.

you could be running the ti elite at 2 or 8 ohms, and have very different efficacy ratings.

the cyclone is a SVC, so listing the voltage isnt necessary since its a 8ohm driver. it is what is is.

Tom is better then me at explaining the math behind it

Post by **stipud** » Mon Sep 29, 2008 9:15 am

2.83v is 1 watt at 8 ohms. If the Elite were tested in series (8 ohms), it would be equal to its 1W/1M rating. If it was tested in parallel (2 ohms), then it is ~6dB above its 1W/1M rating. This is because of the rule of thumb that you gain ~3dB every time you double power. 2.83v at 8 ohms is 1 watt, 2.83v at 4 ohms is 2 watts, 2.83v at 2 ohms is 4 watts. So in this case, its 1W/1M rating would be ~80dB, which for the Elite wouldn't surprise me. It's a power hungry beast!

1W/1M ratings let you compare how loud speakers will be on X watts, regardless of impedance.

2.83v lets you compare how loud speakers will be on the same amplifier, assuming the amplifier can support the impedance of all the drivers.

Usually though, a 2.83v rating is used to give a high efficiency number on low impedance woofers, so that uninformed people will think they are a better speaker.

maka78 · Post by **maka78** » Mon Sep 29, 2008 9:27 am

Wow, that's crazy low... no wonder they didn't sound as loud as I was expecting them to sound. I gotta admit they are really good in SQ though.

Thanks for the explanations.

Post by **stipud** » Mon Sep 29, 2008 9:31 am

This is why I generally state that Elites need 2000w each to sound their best. On less than 1000w I was always underwhelmed with them, and they seemed to really liven up in the 1400+ range.

Best Elite sub setup I heard was with a PAIR of Tantrum 1200.1's... one on each coil. It could drop and play tight bass like nobodies business! My RSD comp on 300 watts comes close in SQ to that setup, but waaaaaay short in bass output (of course with the 3000w on that Elite you could run 6 of these).

maka78 · Post by **maka78** » Mon Sep 29, 2008 11:58 am

stipud wrote:This is why I generally state that Elites need 2000w each to sound their best. On less than 1000w I was always underwhelmed with them, and they seemed to really liven up in the 1400+ range.

Best Elite sub setup I heard was with a PAIR of Tantrum 1200.1's... one on each coil. It could drop and play tight bass like nobodies business! My RSD comp on 300 watts comes close in SQ to that setup, but waaaaaay short in bass output (of course with the 3000w on that Elite you could run 6 of these).

Won't this blow out the sub if you have that much wattage on it and it only suggests 1200w to a sub?

I'm pissed now cause I got the Cadence 2500w @ 1 Ohm amp for 2 TI12Ds, when I should have really got the 5000w @ 1 Ohm amp from them. They sound good, but don't pound nearly as hard as some other systems I've heard, especially if they're pushing over 2kW.

maka78 · Post by **maka78** » Mon Sep 29, 2008 12:04 pm

stipud wrote:2.83v is 1 watt at 8 ohms. If the Elite were tested in series (8 ohms), it would be equal to its 1W/1M rating. If it was tested in parallel (2 ohms), then it is ~6dB above its 1W/1M rating. This is because of the rule of thumb that you gain ~3dB every time you double power. 2.83v at 8 ohms is 1 watt, 2.83v at 4 ohms is 2 watts, 2.83v at 2 ohms is 4 watts. So in this case, its 1W/1M rating would be ~80dB, which for the Elite wouldn't surprise me. It's a power hungry beast!

1W/1M ratings let you compare how loud speakers will be on X watts, regardless of impedance.

2.83v lets you compare how loud speakers will be on the same amplifier, assuming the amplifier can support the impedance of all the drivers.

Usually though, a 2.83v rating is used to give a high efficiency number on low impedance woofers, so that uninformed people will think they are a better speaker.

If, theoretically, an amplifier makes the same power on 8 ohms as it does on 1 ohm, does that mean the speaker will actually sound louder (use the power more efficiently) at the 8 ohm connection?

Post by **stipud** » Mon Sep 29, 2008 12:18 pm

maka78 wrote:Won't this blow out the sub if you have that much wattage on it and it only suggests 1200w to a sub?

I'm pissed now cause I got the Cadence 2500w @ 1 Ohm amp for 2 TI12Ds, when I should have really got the 5000w @ 1 Ohm amp from them. They sound good, but don't pound nearly as hard as some other systems I've heard, especially if they're pushing over 2kW.

No. Power ratings on subwoofers are nominally rated, based on excursion limits or thermal limits of the speaker. With clean power and music, you can run most speakers well above their rated power.

I would guess you could run the Elite on 1200w playing a constant test tone. Test tones make speakers heat up dramatically, so they have to be designed to dissipate this heat somehow. On dynamic music, you have only very short bursts of high power, so overheating the woofer is less of a concern. I certainly wouldn't recommend running 3000w of test tones to an Elite for more than a few seconds though.

Clipping is also very important. If you clip a 1200w signal, you may still damage an elite. Clipping at 3000w would be much worse... so if you are going to overpower a speaker in this fashion you not only need to listen to music instead of test tones, but you need to ensure your gains are set perfectly so as to never cause clipping.

Please read this:
http://bcae1.com/2ltlpwr.htm

maka78 · Post by **maka78** » Tue Sep 30, 2008 1:43 pm

How can you tell at what resistance is the sensitivity rating for a DVC subwoofer? I understand that if they have the V, then you can figure it out, but what if they don't? Is there a standard to pick 8 ohms if it's DVC 4 ohm/coil?

naughty · Post by **naughty** » Tue Sep 30, 2008 5:10 pm

If, theoretically, an amplifier makes the same power on 8 ohms as it does on 1 ohm, does that mean the speaker will actually sound louder (use the power more efficiently) at the 8 ohm connection?

no - it probably wont be louder

but in theory (on paper) at the higher impedance the amp should retain a higher damping factor thus control the speaker better hence it may sound better/more controlled but not necessarily louder

Post by **stipud** » Wed Oct 01, 2008 7:15 am

maka78 wrote:How can you tell at what resistance is the sensitivity rating for a DVC subwoofer? I understand that if they have the V, then you can figure it out, but what if they don't? Is there a standard to pick 8 ohms if it's DVC 4 ohm/coil?

It would have two possible ratings... a 2 ohm and an 8 ohm. If it only lists one efficiency rating at 2.83v, and it doesn't say which impedance it is, I would assume they went with the low impedance in order to inflate the efficiency number. 80dB at 8 ohms is not a very impressive number to most people.