Sensitivity Ratings

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DMurphy

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Re: Sensitivity Ratings
« Reply #20 on: 30 Dec 2008, 07:32 pm »
I tried high sensitivity single speaker drivers and I didn't get the full spectrum of sound that I wanted.   I, therefore, traded sensitivity for watts and now really like the sound.

Cheers,
Tom

Right--I've been working with 3 super expensive ($500 - $1200) high sensitivity "full range" drivers trying to see if one would work as a wide range mid in the HT4.  Only one of them was really listenable in the highs, and none had any real low bass extension.  I've never understood the attraction of these things (particularly since I would be out of business if anyone did invent a full range driver that didn't need a crossover or two).

DMurphy

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Re: Sensitivity Ratings
« Reply #21 on: 30 Dec 2008, 08:14 pm »
My ST's are rated at 88db, right (did the ribbon change that)?  Well, they rock loud, and I can't imagine needing them to be a higher sensitivity.  I had them at 100dB on the Radioshack meter and they stayed clean without distortion, compression or the woofers bottoming out.  They had more room to play, too.  Nice!


Hi Nuance    The ribbon didn't affect the sensitivity--that's set by the woofers.  Even in pairs, they're less sensitive than either the 0W2 dome or the LCY ribbon. 

BPuckett

Re: Sensitivity Ratings
« Reply #22 on: 30 Dec 2008, 10:29 pm »
Well, I suspect that Klipsch places the microphone on the horn-loaded tweeter axis when they make their measurements, rather than on the more realistic axis that splits the difference between the tweeter and the other non-horn-loaded drivers.  Doing so would give a higher sensitivity rating than would be experienced during actual listening conditions where the listener's ears are not aligned with the tweeter axes.  Maybe I'm wrong, but I think that's what's happening.

Bob

Well, in theory sensitivity ratings are supposed to be made at 1 kHz, which would be below the tweet's operating range.  I really don't know how Klipsch came up with 97 dB. 

From all that I've read about loudspeaker technology, including going all the way back to Leo Beranek's "Acoustics" and farther, loudspeaker technology is mature technology, much like Class A and Class AB power amplifier technology.  Much of what passes for loudspeaker design today is aesthetic.  The trick is to make a good sounding speaker that is aesthetically pleasing and that is priced at a point that beats the competition.  That is what Jim and Dennis do.  My point is that, from what I've read, it is extremely difficult, if not impossible, to design a speaker with very high sensitivity without using horns to load the drivers.  Of course, the larger the driver, the larger the horn.  Thus, Klipsch loads only the tweeters to keep the speakers acceptable with respect to size.  So, I am implying that Klipsch ignores the 1 KHz testing convention by testing their speakers at a frequency that falls within the frequency range of the horn-loaded tweeters.  Hence, the unusually high sensitivity ratings claimed by Klipsch.  Buyer beware.

I've had good and bad experiences with both high and low sensitivity speakers.  As we've all heard many times before, do as much comparative listening as you can, preferably in the environment in which you will be using the speakers, with the ancillary equipment you intend to use.

By the way, I still love my HT3's, and I admire Jim and Dennis for their great craftsmanship abilities.

Bob

Nuance

Re: Sensitivity Ratings
« Reply #23 on: 30 Dec 2008, 11:21 pm »
Hi Nuance    The ribbon didn't affect the sensitivity--that's set by the woofers.  Even in pairs, they're less sensitive than either the 0W2 dome or the LCY ribbon. 
Thanks, Dennis.  That's what I thought, but I wanted to confirm.  Cool!

I love my SongTower RT's! 

For anyone who likes rock and roll, get your hands on Joe Satriani's "Rubina" and let it spin on your Salk's.  Truly awesome!

P.S.  "Rubina" isn't really a rock and roll song, but Satriani is mainly a rock and roll guitarist, so...

BPuckett

Re: Sensitivity Ratings
« Reply #24 on: 31 Dec 2008, 06:02 pm »
"Rubina", which is named after his wife, is on Satriani's 1st CD, "Not Of This Earth".  It is one of many beautiful instrumental ballads that Satriani has written and recorded.  Highly recommended.

Bob

Nuance

Re: Sensitivity Ratings
« Reply #25 on: 1 Jan 2009, 04:02 pm »
Thanks!  What a beautiful song!

The version I was listening to was the remastered version on the Satriani anthology discs.  The SQ is much better. 

Atlplasma

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Re: Sensitivity Ratings
« Reply #26 on: 1 Jan 2009, 06:28 pm »
My ST's are rated at 88db, right (did the ribbon change that)?  Well, they rock loud, and I can't imagine needing them to be a higher sensitivity.  I had them at 100dB on the Radioshack meter and they stayed clean without distortion, compression or the woofers bottoming out.  They had more room to play, too.  Nice!


Hi Nuance    The ribbon didn't affect the sensitivity--that's set by the woofers.  Even in pairs, they're less sensitive than either the 0W2 dome or the LCY ribbon. 

Hi Dennis:

FedEx says my STs with ribbons should arrive tomorrow.  aa I'll use them primarily with my Yamaha/Outlaw monoblock setup, so power shouldn't be an issue. But would I run into a problem if I tried to drive them with my Eico ST-70? It's a tube amp rated at 35 watts per channel. I've just replaced the caps and put in a new set of tubes. It sounds very nice on my M&K monitors, which Sound & Vision measured at 88.4 dB (similar to the STs). Of course they are fairly compact monitors and not full-range speakers.

Steve

DMurphy

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Re: Sensitivity Ratings
« Reply #27 on: 1 Jan 2009, 07:13 pm »
Eico ST-70, huh.  That was my first amp back in, well, 19...uh....forgeddaboudit.     I got the amp, a pair of AR4x speakers, and an AR turntable with a Shure cartridge for $277 delivered.  What was the question?  The SongTowers, right.  My Eico had no problems with the AR4's, and the ST's are way more sensitive than the AR's.  The ST's impedance probably falls a little bit lower in places, but I don't think it will be an issue.  I would crank up the Eico. 

JLM

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Re: Sensitivity Ratings
« Reply #28 on: 1 Jan 2009, 09:01 pm »
For whatever reason Klipsch speakers have been "known" for years to be over rated in regards to sensitivity.  It may go back to the days when only low powered tube amps were available.  Even today, most spl meters are sold to SET owners who worry about finding efficient enough speakers.

Another way to play the "efficiency game" is to build a speaker that doesn't produce (isn't rated to do) deep bass.  This allows for less woofer efficiency limitations.  OTOH it also takes the "heavy lifting" off the amp.  Again this has been a typical solution for "SET friendly" speakers for decades.

To my ear, most horn loadings have very noticable colorations, probably due to non-linear compression of the air or flexure of the horn walls, both of which are pushing the horn loading concept too hard.  And arrays of drivers have obvious comb filtering and vertical imaging issues.  Neither approach can be taken seriously for high quality reproduction.

I agree with you Tom and Dennis, most single (extended range) drivers, especially the high efficiency ones, are better termed (accepted) as mid/tweeters.  The Fostex F200A (and to a lesser degree the F120A) is an exception.  It is rated to 30 Hz and 90 dB/w/m, but is only rated to handle 27 watts.  And without a whizzer cone, beams above 4,000 Hz.  As Jim stated, there is no free lunch.

Atlplasma

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Re: Sensitivity Ratings
« Reply #29 on: 1 Jan 2009, 09:54 pm »
Eico ST-70, huh.  That was my first amp back in, well, 19...uh....forgeddaboudit.     I got the amp, a pair of AR4x speakers, and an AR turntable with a Shure cartridge for $277 delivered.  What was the question?  The SongTowers, right.  My Eico had no problems with the AR4's, and the ST's are way more sensitive than the AR's.  The ST's impedance probably falls a little bit lower in places, but I don't think it will be an issue.  I would crank up the Eico. 

As a matter of fact, my father built the ST-70 around 1963 or 64. I remember him soldering it on the dining room table. He also put together a set of AR2s and an AR turntable. My mother still has those units, but they need some renewing as well. (Perhaps a future project.)

I'm considering getting an A/B switch (maybe a Niles or Russound model) so I can switch between the Yamaha and the Eico.

DMurphy

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Re: Sensitivity Ratings
« Reply #30 on: 2 Jan 2009, 12:32 am »
Eico ST-70, huh.  That was my first amp back in, well, 19...uh....forgeddaboudit.     I got the amp, a pair of AR4x speakers, and an AR turntable with a Shure cartridge for $277 delivered.  What was the question?  The SongTowers, right.  My Eico had no problems with the AR4's, and the ST's are way more sensitive than the AR's.  The ST's impedance probably falls a little bit lower in places, but I don't think it will be an issue.  I would crank up the Eico. 

As a matter of fact, my father built the ST-70 around 1963 or 64. I remember him soldering it on the dining room table. He also put together a set of AR2s and an AR turntable. My mother still has those units, but they need some renewing as well. (Perhaps a future project.)

I'm considering getting an A/B switch (maybe a Niles or Russound model) so I can switch between the Yamaha and the Eico.

Fortunately, my Eico came wired.  And since you've opened up the possibility that I might have bought it in 1963--in was MUCH later than that.    June of 1966, to be exact. 

Manowar

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Re: Sensitivity Ratings
« Reply #31 on: 23 Jan 2009, 01:37 am »
Can the ST's be bi-amped??? Or are the two 5" drivers used in a push-pull configuration? :scratch:

DMurphy

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Re: Sensitivity Ratings
« Reply #32 on: 23 Jan 2009, 02:53 am »
Can the ST's be bi-amped??? Or are the two 5" drivers used in a push-pull configuration? :scratch:

They're both pushing.  And they're both pulling.  Just a simple parallel connection. 

avahifi

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Re: Sensitivity Ratings
« Reply #33 on: 23 Jan 2009, 03:53 pm »
Just my thoughts regarding horn loaded speakers.

To the best of my limited speaker design ability, I understand that horn loaded speakers gain efficiency by generating a resonant peak at the tuned frequency of the horn.  In other words a horn loaded driver is an acoustic oscillator.

I have always thought that oscillators oscillate.  Not only at their resonant frequency but when they see any harmonic of their resonant frequency.

The facts that horn speakers generate underdamped resonant peaks and also have response to signals other than what is desired, means that they pretty badly violate the goals of flat damped wide band response being a good idea for speaker design.

Correct me if I am wrong.

Regards,

Frank Van Alstine

P.S.  For years I have suggested either wrapping the outside surface of K-Horn horn structures with black cloth electrical tape or coating them with plastic modeling clay to tame metalic resonances from the horn structures.  Those that have tried this report that it makes stuff that was not supposed to be there go away to excellent effect.  I also suggest damping the metal framework of conventional drivers with plastic modeling clay for the same reason.  I have not managed to get Jim or Dennis to try this yet.  I hope they do.

DMurphy

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Re: Sensitivity Ratings
« Reply #34 on: 23 Jan 2009, 04:18 pm »
1) I've never heard a horn midrange or tweeter that I liked.  For the reasons Frank  mentions.  2) As I type, I have one CA15 woofer frame tightly wrapped in mortite, and another one nude, both ready to plop into test boxes and be connected to my magic comparo box.  And Saturday morning I will conduct a highly scientific A-B test and report the results to a waiting world.   

avahifi

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Re: Sensitivity Ratings
« Reply #35 on: 23 Jan 2009, 08:52 pm »
I hope you are not really using Mortite.  That is an acid based plumbers putty that might put out corrosive fumes that could damage voice coil wires.

Also I would expect to see more difference with midrange and high frequency drivers.  When I demonstrated this at B&W in Worthing many years ago, they found, using their laser inferometer, that there was acoustic output from the speaker framework that was only 10 dB down from the cones at some frequencies.

Regards, and thanks for trying.

Frank Van Alstine

R Swerdlow

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Re: Sensitivity Ratings
« Reply #36 on: 23 Jan 2009, 09:50 pm »
That will be interesting to know if clay dampening on the speaker frames makes a difference.

Is it possible that a stamped steel speaker frame would be improved more by dampening treatment than a cast alloy one such as the CA15?  I guess there's only one way to find out.

DMurphy

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Re: Sensitivity Ratings
« Reply #37 on: 24 Jan 2009, 02:25 am »
I hope you are not really using Mortite.  That is an acid based plumbers putty that might put out corrosive fumes that could damage voice coil wires.

Also I would expect to see more difference with midrange and high frequency drivers.  When I demonstrated this at B&W in Worthing many years ago, they found, using their laser inferometer, that there was acoustic output from the speaker framework that was only 10 dB down from the cones at some frequencies.

Regards, and thanks for trying.

Frank Van Alstine

Well, I really doubt that a brief exposure to mortite will do in any voice coils.  I'm going to be testing a principle, not a long term solution.  And if I run the CA15's full range, that will be a test of the midrange and treble (they're flat to around 8 kHz).  Obviously,  wrapping mortite around a tweeter won't have any effect.  There's no frame. So that leaves either the CA15's or perhaps the CA12's.  If you think the smaller CA will be a better test, I'll use those.  I actually have small cabinets that were designed specifically for the CA12's, so I'll just plan on doing that.  I'll also do some waterfall plots, although I kind of doubt I'll have enough resolution to pick up any differences. 

avahifi

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Re: Sensitivity Ratings
« Reply #38 on: 24 Jan 2009, 11:20 am »
Short term Mortite is OK, it is long term exposure with it that worries me about voice coil damage.

Yes I would suggest the smaller speaker.  I suspect the damping effect on speaker framework resonances will be more of a mid and high factor than at low frequencies.

Thanks much for setting up the experiment. I will be very interested in your findings.

Best regards,

Frank Van Alstine

Zheeeem

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Re: Sensitivity Ratings
« Reply #39 on: 24 Jan 2009, 03:52 pm »
Hmmm...  This is an interesting topic that's morphed into, well, a different interesting topic.

I have always distrusted sensitivity ratings.  I guess the main reason it that the measurement is at 1K, and I'm not sure that tells me much of anything about a speaker's performance.  (Same with Ohmage ratings, because resistance is anything but flat across the frequency spectrum.)  At best these are clumsy devices that probably mislead consumers more than they help.  Because I have had magnepans for the past nearly 40 years, I've simply tended towards amps with enough juice to drive them.  One key reason is that most of the gear I've seen destroyed has resulted from folks clipping their amps - a fairly obvious reason why inflating sensitivity ratings is not a good thing.

Vibration damping and plasticlay is one of my all time favourite topics.  Frank is, of course, the guru of plasticlay.  Some 30 years ago he wrote it up in Audio Basics, I tried it, and he was kind enough to reprint my letter to him extolling its benefits in a later AB issue.  (Remember when we wrote letters?)  In that case it was my fully damped turntable (and yes, the stuff is great for wooden box-style TTs).

One of my subsequent speaker purchases was the biro L/1 that Frank distributed for Mithat Konar, and my uderstanding (Frank can please correct me if I'm wrong) is that Mithat applied the same principles of internal damping.  As Frank predicted, I regret selling them 4-5 years back.

When my Tympani 1(U)s gave up the ghost 3 years ago, and my spousal unit insisted that I rebuild them instead of junking them (so much for WAF), it gave me a chance to try out approaches to damping the particleboard.  (In the tympanis, pretty much everything vibrates and makes "music" or something vaguely similar.)  I used silicone caulk in the corners and at the join between the elements and the particleboard, and plasticlay over the rear surfaces.  While it obviously couldn't solve the fatal flaws of the tympanis, the improvements were quite noticeable and for the better.

My current mains are VMPS RM30Ms.  In these, Brian Cheney uses mortite to tune the passive radiators.  The mortite is, technically speaking, on the outside of the enclosure, and well away from anything electrical.  So I think the issue Dennis raised is probably moot.  But it (1) is very useful and audible, because in this case its use is actually integrated into the design and (2) sticks really well (which is a potential problem with plasticlay).  IIRC Brian uses something to damp cabinet innards, and sells BH5 as an upgrade.  In the spirit of overkill, he's taken to building cabinets for his subs using 2" MDF.

So, Dennis, all I can do is encourage your experiments and let you know that I'll be really interested in following your results.