[Ultralight]

I figure things I don't have to bother Louis with I can ask here...

For single RS5, the sensitivity is published at 94.5db @ 8 ohm.
Then for dual RS5 (in parallel apparently) the sensitivity is published at 98db @ 4 ohm.
Such increase in sensitivity is nothing to sneeze at for low powered amps.  More headroom from the amp.

Question:
1. How is it that sensitivity for the SAME WATTAGE climbs with dual drivers?  Drivers have not changed.   I am not well versed with speaker design so am curious how that works.

2. Does that mean 3 drivers, 4 drivers become correspondingly more efficient?

Thanks,
UL

 

[S Clark]

UL, think of it as being like adding extra light bulbs to a circuit; you use more electricity but you get more light. However, if you keep adding light bulbs (in parallel) you can eventually allow so much current to pass that things begin to overheat and finally blow a fuse or trip a circuit breaker.

With speakers, adding extra drivers in parallel will give you more volume, but it allows more current to be delivered from your amp.  As you add addition electrical pathways the resistance drops, extra current flows, and it's harder on the amp.  Drop the resistance much below 4 ohms and many amps will blow a fuse, if your lucky. 

[gab]

For single RS5, the efficiency is published at 94.5db @ 8 ohm.
Then for dual RS5 (in parallel apparently) the efficiency is published at 98db @ 4 ohm.



 

I suspect that what Louis is doing with the second driver is a "0.5 way woofer" approach as described here:

http://www.bambergaudio.com/technical/2pt5.php

But he'd have to answer that one.

gab

[RDavidson]

Yes. The speakers with 2 front firing drivers are 1.5 way designs as specified on the Omega site (in the Outlaw section).

[G Georgopoulos]

it's not efficiency ,it's sensitivity...

[Ultralight]

Fixed in the original post. Thanks.

it's not efficiency ,it's sensitivity...

[Ultralight]

But my understanding, and I may be wrong, is that the sensitivity is rated PER WATT.  So one watt produces 94.5db in one speaker, and another 98db in a second speaker.  And both use the same drivers - just difference in quantity?

Thanks,
UL

UL, think of it as being like adding extra light bulbs to a circuit; you use more electricity but you get more light. However, if you keep adding light bulbs (in parallel) you can eventually allow so much current to pass that things begin to overheat and finally blow a fuse or trip a circuit breaker.

With speakers, adding extra drivers in parallel will give you more volume, but it allows more current to be delivered from your amp.  As you add addition electrical pathways the resistance drops, extra current flows, and it's harder on the amp.  Drop the resistance much below 4 ohms and many amps will blow a fuse, if your lucky.

[pstrisik]

UL, think of it as being like adding extra light bulbs to a circuit; you use more electricity but you get more light. However, if you keep adding light bulbs (in parallel) you can eventually allow so much current to pass that things begin to overheat and finally blow a fuse or trip a circuit breaker.

With speakers, adding extra drivers in parallel will give you more volume, but it allows more current to be delivered from your amp.  As you add addition electrical pathways the resistance drops, extra current flows, and it's harder on the amp.  Drop the resistance much below 4 ohms and many amps will blow a fuse, if your lucky.

Very nice analogy.  Really conveys the concepts of power, current, and impedance.  I've always intuitively understood it, but this helps understand it more cognitively. 

.........Peter

[pstrisik]

But my understanding, and I may be wrong, is that the sensitivity is rated PER WATT.  So one watt produces 94.5db in one speaker, and another 98db in a second speaker.  And both use the same drivers - just difference in quantity?

Thanks,
UL

I think you're correct UL.  And... distance factors into the equation as well.  93db/1watt/1meter, for example.   

So, the dual driver provides more volume for the same power.  Translates as not turning up your preamp's volume control as much to get the same volume level!

........Peter

[G Georgopoulos]

sensitivity/efficiency SAME THING...

cheers Guys...

[Ultralight]

That's what I do not understand. If your preamp, or integrated is turned to the same place on the dial, with a 4 ohm load (dual drivers) you are actually drawing MORE (approximately double) current since the load is 4 ohm rather than 8 ohm.   So you are not really getting greater efficiency.  Rather the amp is simply putting out more power (watts) for a specific setting.  So the sensitivity/efficiency stays the same rather than increase.     

That's why I'm trying to understand where I'm not understanding...   

The reason I'm asking is that I may consider low powered rigs in the future so sensitivity/efficiency matters.

Thanks,
UL

I think you're correct UL.  And... distance factors into the equation as well.  93db/1watt/1meter, for example.   

So, the dual driver provides more volume for the same power.  Translates as not turning up your preamp's volume control as much to get the same volume level!

........Peter

[JohnR]

Sensitivity and efficiency are not the same thing. Sensitivity is acoustic output relative to voltage, usually specified as 2.83V, efficiency is acoustic output relative to power, usually 1 Watt. (If the load is exactly 8 ohms, then the number is the same.)

With two drivers in parallel, efficiency increases by 3 dB, and sensitivity by 6 dB. That is at low frequencies (relative to driver spacing), where the two drivers can be considered to act acoustically as one.

With four drivers in series-parallel, efficiency increases by 6 dB, and sensitivity increases by 6 dB. So yes, efficiency increases each time you increase the number of drivers i.e. +3 dB each time you double the number.

Those are "all other things being equal" / theoretical numbers. You might like to download something like Unibox and have a play with it (http://audio.claub.net/software/kougaard/ubmodel.html). It will give you calculated figures for sensitivity and efficiency for various driver configurations.

[FullRangeMan]

I figure things I don't have to bother Louis with I can ask here...

For single RS5, the sensitivity is published at 94.5db @ 8 ohm.
Then for dual RS5 (in parallel apparently) the sensitivity is published at 98db @ 4 ohm.
Such increase in sensitivity is nothing to sneeze at for low powered amps.  More headroom from the amp.

Question:
1. How is it that sensitivity for the SAME WATTAGE climbs with dual drivers?  Drivers have not changed.   I am not well versed with speaker design so am curious how that works.

2. Does that mean 3 drivers, 4 drivers become correspondingly more efficient?

Thanks,
UL

In the parallel or tandem connection when
the number of speakers doubles (1,2,4,8)
there is an increase in SPL output by 3dB.
In series connection this benefit does not
happen.
The reason is serial is too slow to activate
all the drivers, the music signal came and
go by the same way/wire, hence the delay.
Parallel:

Serial:

[hibuckhobby]

I doubt the "distance" traveled has much to do with it.  The impedance halves in a parallel connection.
Depending on the amplifier, this of course, reaches a point of diminishing returns as the impedance
goes too low.  There is also the issue as JohnR indicated of doubling the surface area that is vibrating
and producing sound.
Hibuck...

[RDavidson]

That's what I do not understand. If your preamp, or integrated is turned to the same place on the dial, with a 4 ohm load (dual drivers) you are actually drawing MORE (approximately double) current since the load is 4 ohm rather than 8 ohm.   So you are not really getting greater efficiency.  Rather the amp is simply putting out more power (watts) for a specific setting.  So the sensitivity/efficiency stays the same rather than increase.     

That's why I'm trying to understand where I'm not understanding...   

The reason I'm asking is that I may consider low powered rigs in the future so sensitivity/efficiency matters.

Thanks,
UL

I think I understand where you're coming from. It's a little bit of give and take. The (paralled) speakers are a more difficult load (4 ohms) and certainly require more current, BUT this is negated a little bit because they have increased output vs a single driver speaker (of the same make). So actually, you'd turn the volume knob down a smidge to equal the same output of a single driver design, assuming the amp significantly increases its power output from 8 ohm down to 4 ohm. Yes, if you want to go the true high efficiency route, stick with a single driver as the power requirement is less (as the load is easier). The tradeoff is total output before severe distortion. But most into high efficiency speakers aren't into them because they want to shatter windows. It really boils down to your preferences and room size and listening distance to determine what would be best.