How do Klipsch get these high efficiency numbers?

[paulspencer]

Helping a friend choose some speakers for a home cinema setup (gasp - not diy!), I've come across Klipsch synergy speakers. My friend is keen on them, and I'm perplexed by them, in particular their quoted efficiency seems ridiculous!

Take the F-3 for example. 97 db @ 2.83v/1m and "8ohm compatible." It has a horn loaded CD and two 8" midbass drivers in a bass reflex enclosure with bass down to 35 Hz.

How do we get such high efficiency?

Working backwards, let's assume that there is no BSC and that the impedance is a little on the low side, meaning that this is not a true sensitivity rating as the input power is in fact more like 1.5w giving us say 1.5 dB extra. So in reality it is more like 95.5 dB for two drivers. That means each driver must be 92.5 dB sensitive. That is a bit of a stretch. If you look at hifi drivers of that size designed for the same bandwidth, 91 db is about as good as it gets, unless the driver has a sloping response with greater midrange sensitivity to tweak the numbers up.

So with some fudging, I can get within 1.5 db. But what should it be? Using those drivers with a sensible 3db of BSC, we should in fact see 91 dB as the efficiency to allow us to place it into the room rather than against a wall. Or, if we accept wall placement, using it only for home theatre, then 94 dB.

I've wondered, what is the point in using a CD/horn with small hifi drivers? A waveguide loaded dome should do just fine.

Or have Klipsch found the magical piece of unobtainium in driver design? I'd like to see their SPL response given 1w of input.

I found their sound surprisingly good - tonal balance seemed reasonable, although I found them lacking in the sweeter sound I'm used to and the deeper soundstage and box resonance free sound of my open baffle speakers.

Can anyone shed some more light on this? I know this topic has come up before, but I'd like to tackle it again.

[Glowbug]

They make it up?



I know it's a very short response to a lot of text...but...

[Jack Hidley]

Very short woofer coils, so the instant the speaker needs to produce any bass below 100Hz, instant distortion.

A sloped up frequency response.

Pick your sensitivity measurement at the 4kHz spike.

I bet the speakers minimum impedance drops below 4ohms.

There is no free lunch, just exaggerated claims based on incomplete information.

And yes, you would never want a CD horn in a home environment with a low RT60.

[Rybaudio]

I've seen the measured responses of a dozen or so Klipsch speakers and they hold up to spec, but they do use somewhat of a "trick" to get the numbers higher. This was pointed out to me by a former boss of mine who used to be a systems engineer at Klipsch. I've attached a (crude) drawing of a typical Klipsch speaker on axis amplitude response. The horn keeps the sensitivity high on the upper end of the response. On the low end of the response a big ported box is used which results in a peak around tuning. Where the midwoofers' response is flat (in the mass controlled region) the response does drop a little bit. This is how they get the nominal sensitivity high.

[QSerraTico_Tico]

Originally posted by Rybaudio
I've seen the measured responses of a dozen or so Klipsch speakers and they hold up to spec, but they do use somewhat of a "trick" to get the numbers higher. This was pointed out to me by a former boss of mine who used to be a systems engineer at Klipsch. I've attached a (crude) drawing of a typical Klipsch speaker on axis amplitude response. The horn keeps the sensitivity high on the upper end of the response. On the low end of the response a big ported box is used which results in a peak around tuning. Where the midwoofers' response is flat (in the mass controlled region) the response does drop a little bit. This is how they get the nominal sensitivity high.

[paulspencer]

Ahhh, now that's making sense, thanks.

Jack, could you elaborate on the short VC?
How is that an advantage with efficiency?

Surely this would mean no real xmax, hence no real bass capability. They do appear to be fairly conventional midbass drivers, I'd imagine with 4 - 6 mm xmax.

So far I've found with efficient speakers, they haven't sounded good enough to make the extra output useable. I heard some Adire HE10s next to some Focal MTM speakers, and the Focals sounded listenable at a louder volume. The HE10s would happily go much louder than my ears wanted - too harsh.

I'd love to hear an efficient high output system with the relaxed sound I get from my system, but I haven't found one yet. Not a big issue right now, but there will come a time where I'll be considering an array of smaller conventional hifi drivers vs pro drivers.

[Gary P]

My experience measuring my old Heresy speakers shows that the high efficiency rating was a bit of a stretch. The tweets may have been 97dB, the mids 94dB or 95dB and the woofer came in at only 92dB. The frequency response was very tilted up and very rough.

[Magnetar]

Twin woofers when closely spaced may gain 6db in sensitivity over a single. Add two more and your up even more- also don't forget the mirrored pair reflection on the floor and the additional boundary gain from the rest of the room

For example run a pair of these in parallel - 8 inch woofer

99- 100 db with 2.83 volts is probable with these eights

[Syncroniq]

Hi,

You can see a meassurement of a klipsh here...

Stereophile meassurement

High reflex tuning as mentioned.

[Caferacer]

Ughhh. That looks like an ear burner.