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Endo

Audio Voodoo

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I'm new here (obviously--as evidenced by the profile, left of this post... )

I'm in no hurry, but am in the market for some heritage Klipsch to improve my current system. As I read about the different designs--voodoo mystery is keeping me awake at night:

 

1. Why does a Cornwall, with a 15" driver, extend down to 38 Hz; but, an RF5, with 8" drivers, extends down to 34 Hz? This makes no sense to my small brain.

 

2. The 15" driver moves more air than two 8" drivers--and I speculate this translates to a difference in the quality of sound produced; but, what is this difference?

 

If I had unlimited funds, I would buy everything and keep what I like. Alas, this is not me.

 

Would anyone care to comment?

 

 

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Where are you located? I would recommend that if possible, you find some fellow forum members in your local area and give a listen to some different speakers before you make a buying decision. That doesn't specifically answer your questions but, to me it would be a good start on your journey.

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Here is a good discussion on the trade off between sensitivity and bass extension.  The RF5 is not as sensitive as the Cornwall.  It may produce more bass, but it will require more power.

 

http://www.salksound.com/wp/?p=56

 

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Generally loudspeaker engineers select a balance between size, sensitivity and low bass (pick 2).  The Cornwall III is larger with a higher -3 dB point, but at 102 dB/w/m is 3 dB more sensitive. Three dB is 2x the power.   Pick your preference. 

 

A smaller cabinet nets lower sensitivity at the same f3 or the same sensitivity with a higher F3.

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jimjimbo, Seadog, John:

Thank you for the responses--and for explaining what seemed crazy. All else being equal... I never understood bass extension as a function of sensitivity.

Edited by Endo
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On 4/11/2017 at 7:07 PM, Endo said:

1. Why does a Cornwall, with a 15" driver, extend down to 38 Hz; but, an RF5, with 8" drivers, extends down to 34 Hz? This makes no sense to my small brain.

If you take a woofer cone of a certain weight and place it into a basket structure with a loose suspension around the edge of the cone, it will have a lower resonant frequency in open air than a cone with a stiffer suspension.  So for 8" woofers to have a lower free air resonance that a 15" woofer, they must have a much lower suspension stiffness than the 15" woofer, all other things being equal.

 

If you take a woofer and stick a coin to the dust cap via glue or modeling clay, etc., it will lower the free air resonant frequency. So a woofer that's heavier (including the voice coil at the cone's apex) will resonate at a lower frequency, all other things being equal.

 

If you take a very floppy woofer with almost no suspension stiffness and drive it with an amplifier, it will have the tendency to "unload" or push the voice coil out of the gap or impact it into the magnet (traveling in the other direction). 

 

If you put a floppy/heavy-cone woofer into a small sealed box with the air behind the woofer cone trapped (like an air spring), it will raise the resonant frequency of the woofer+box.  You can then adjust the volume of air in the box (by resizing the box volume) to adjust the resonant frequency.  This is called "acoustic suspension". 

 

If you place a woofer in a vented box, then the woofer+vented box will have two resonant frequencies: one for the woofer as if it's in free air, and another resonance of the ports of the vented box - sort of like blowing air over the top of a coke bottle.  If you design the box and ports carefully, you can slightly lower the free air resonant frequency of the woofer by adding in the resonant frequency of the box+ports (which will be designed to be lower than the free air resonance of the woofer), and use the "back wave" of the woofer to drive it--something that the acoustic suspension design absorbs into the box.  This make the vented box about 3 dB more efficient (but not necessarily more sensitive) than a closed box bass bin.

 

So, using all the techniques above, the loudspeaker designer has choices to make on where the resonant frequency of the bass bin is designed to be.

 

On 4/11/2017 at 7:07 PM, Endo said:

2. The 15" driver moves more air than two 8" drivers--and I speculate this translates to a difference in the quality of sound produced; but, what is this difference?

 

Paul Klipsch was quoted as saying that "the more movement [of a driver]...the greater the distortion".  What he was talking about was modulation distortion (i.e., amplitude and frequency modulation, with frequency modulation being what many people call "Doppler distortion").  So the sound of a woofer that has to move a longer distance--all other things being equal--will produce more distortion.  Some people over time have gotten used to the sound of distorting woofers used in loudspeakers.  Others haven't.  In my experience, those that like low distortion tend to gravitate toward horn-loaded bass, while those that have gotten used to woofer modulation distortion (and also something else called group delay distortion) will tend to favor the "impact" of higher-distorting woofer/box designs.

 

The sound of modulation and group delay bass distortion is very distinct to my ears: it's an exaggerated and heavy sound--like something is that is moving and making sound but overshooting and producing its own sound--not what the recording has in it.

 

Good horn-loaded bass sounds like the real thing. Reference Richard Heyser's 1986 review of the Klipschorn: the sound of a closing car door sounds real with a good horn-loaded bass bin, while the vented box bass bin will sound heavy and exaggerated, and "sloppy".

 

Chris

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Using a woofer to produce bass in direct-radiating mode (i.e., open baffle, closed box, vented box/bass reflex) will have to move about 5x farther than the same woofer mounted in a well-designed horn-loaded bass bin to produce the same SPL (loudness) while listening on-axis.

 

This includes the K-33 woofer used in the Klipschorn, La Scala and Belle as a horn-loaded woofer (with an acoustic suspension box behind the woofer inside the bass bin) and the same woofer used in a Cornwall vented bass reflex cabinet. 

 

See https://community.klipsch.com/applications/core/interface/file/attachment.php?id=69997 for a discussion by PWK of the difference in sound between the Cornwall and the La Scala/Belle bass bins.

 

Chris

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On ‎4‎/‎11‎/‎2017 at 7:07 PM, Endo said:

The 15" driver moves more air than two 8" drivers--and I speculate this translates to a difference in the quality of sound produced; but, what is this difference?

Without knowing the x-max (how far a driver travels in and out) it's impossible to say which one will displace more air.  That being said, the cabinet and not the drivers ultimately determines how low the speaker will play.

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Chris gave a masterful explanation of speaker design and distortion.  We can look at graphs and see these things or see the distortion numbers for amp or other gear in the audio chain.  Now comes the question, when does distortion become audible to our ear?  Our hearing is most acute at picking up midrange distortion in contrast to bass distortion.  This is why you see just as many people enjoy direct radiator vs full horn loaded speakers.

 

Also when listening to the various type of speakers distortion becomes more apparent above average listening levels of around 88 to 90 db.  At these levels most of the Klipsch speakers, direct radiator or full horn loaded have minimal cone movement.  A good listening session is needed to see what you really like.  I can enjoy the sound of both type of speakers.  What I am saying in a nutshell is it is hard to pick gear or speakers just off graphs, distortion number, etc.

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One of the things that I didn't mention about modulation distortion:

 

The greatest effects of AM and FM distortion are to produce non-harmonic sidebands of distortion peaks at higher frequencies (mostly midrange) that the bass bin is simultaneously producing. 

 

For a Cornwall, that means that everything up to about 800 Hz (about an octave higher than a A440 tuning fork) will sound wooly and opaque (the so-called "elephant on the dance floor" that Nelson Pass described in his famous article on the subject).  This is the major effect of bass distortion, and is the reason why PWK put so much effort into the Khorn bass bin design.  He also was the biggest advocate of "keeping it clean" in terms of minimizing modulation distortion of anyone that I know or have read about.

 

For other Klipsch loudspeakers in the Reference series, etc. that also means that frequencies up to about 2 kHz are strongly affected.  That's the downside of direct-radiating woofers used in two-way designs.  Horn-loaded bass bins have 25 dB less modulation distortion, all other things being equal, than direct-radiating bass bins.

 

Chris

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As PWK said, "The fact of the case is that distortion is closely proportional to power output. Also the distortion is closely proportional to diaphragm excursion".   Things have to be kept in perspective when talking about distortion.  PWK wrote this in 1970 and technology has improved speaker design. Because of Klipsch high sensitivity speakers, excessive cone movement is just not happening at most listening levels.  I have heard the full horn Klipsch and compared them to the extended Heritage and Reference line, They all sound good and the differences are not that striking .  It is more a preference to what sound you want for your listening pleasure.

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43 minutes ago, derrickdj1 said:

As PWK said, "The fact of the case is that distortion is closely proportional to power output. Also the distortion is closely proportional to diaphragm excursion".   Things have to be kept in perspective when talking about distortion.  PWK wrote this in 1970 and technology has improved speaker design. Because of Klipsch high sensitivity speakers, excessive cone movement is just not happening at most listening levels.  I have heard the full horn Klipsch and compared them to the extended Heritage and Reference line, They all sound good and the differences are not that striking .  It is more a preference to what sound you want for your listening pleasure.

I have flanking Klipschorns with a modified Belle center, and Heresy II surrounds.  The attack clarity of the Klipschorns, especially with timpani, bass drum, etc., is unparaleled.  The Belle is just about as clean, but doesn't go as low.  The Heresy IIs just don't make it in that regard.  For movies, I always use a subwoofer that has relatively long excursion (the Klipsch RSW15), and it is definitely "muddier" than the horns.  Fortunately, it only operates full tilt below its crossover of 80 Hz (but it's roll-off above that is gradual, and it is still producing bass, however attenuated, at 125 Hz, and above), and the Heresy IIs are relieved of bass duty below about 80 Hz, as well, which may help.  For music, I sometimes turn off the subwoofer (and set the Khorns and Belle to "large"), because the sub just isn't as clean.  

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The direct radiating driver is always the weakest link in the chain.

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I agree with this...

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Everyone has their preference.  I am glad I'm a bit more versatile and like Reference, Heritage and Extended Heritage.:)

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^^^^^

As do I - and Chris' description of Cornwall bass as "wooly" is so right. Owning CW's, Belles and LaScalla at the same time really showed my extreme preference for horn loaded bass. And as I've said before so much so that I thought there was an issue with the CW's when shuffling in one for another. For me I gladly sacrifice Cornwalls extended bass for the clean, tight, fast bass of LaScalla. I find Cornwalls slow and muffled in comparison. 

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If I said this place is friggin' awesome... I'd be repeating myself; so, I won't be doing that.

 

However, the responses I got (above) from my initial post are "180-proof-awesomeness". Best taken slowly...

 

I am pleased to announce that I am the new steward of a pair of 1983 Cornwall (1.5?) with all original drivers and B3 crossovers, looking like they've been in a time capsule. [As an aside, both capacitors tested at 67.2 microfarads--exactly matching each other... Are they both fading at exactly the same rate, or is this how they left the factory, within nominal specs?]. I'm not touching them. The cabinet interiors were imbued with the soul of a man that could only result from both competency and a labor of love.

 

Having never before listened to any of the Heritage designs, I went to listen to them--with a few of my favorite recordings--and what I expected to take less than an hour, turned into 4 hours of listening (no, read: "experiencing") the Cornwalls.

 

Intoxicating. ...

 

I'm old enough to know better. But it occurs to me, an entire generation in this world, has grown-up without experiencing high-fidelity.

 

In my mind, the real Paul Klipsch could just as easily replace the imagined Howard Roark in the Fountainhead.

 

I love this place.

Edited by Endo
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Congratulations on your Cornwalls!  

 

I still remember the evening I brought mine home.  I stayed up listening until nearly 4 am, and I had to go to work 3 hours later.  

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On 4/13/2017 at 10:22 AM, derrickdj1 said:

We can look at graphs and see these things or see the distortion numbers for amp or other gear in the audio chain...  

... A good listening session is needed to see what you really like.  ...  What I am saying in a nutshell is it is hard to pick gear or speakers just off graphs, distortion number, etc.

 

As an aside:

Back in the 1950's, the German optics company, LEITZ Camera (aka: 'Leica') published an article which spoke to the peculiar and desirable qualities that had come to be associated with photographs produced from LEITZ optics (commonly understood to be among the best available at that time). The writer made the point that other lens manufacturers from that period (notable Japanese firms, in particular) were known for their high resolving power and clarity, but they lacked what some would call "roundness", "fullness" or "space" in the printed image.

 

The argument was that the Japanese engineers were over-correcting for aberrations; in other words, they were "too good". By "over-correcting", these other lenses--although impeccable in their sharpness and contrast--suffered from appearing "flat" when the negatives were printed.

 

LEITZ engineers, in contrast, stopped short of correcting everything possible--and identified boundaries beyond which they would not go. They deliberately engineered certain amounts of very particular aberrations be retained in lenses used for 35mm, consumer cameras--because they knew these aberrations resulted in what viewers were calling "space" and "volume" in the final, printed image. [Please don't misunderstand, Leitz lenses were not lacking in their sharpness--they just had something more]

 

What's my point in all this? I guess, its that if a person had tried to choose the "best" lens back then by only reading numerical specifications--then they were missing the point. Turns out there was a portion of art in all that optical science. Is there a place for art in the science of audio?

 

I sometimes wonder if "natural" sound (as opposed to reproductions of sounds) has certain and particular aberrations that might sometimes get "corrected" during the process of recording and reproduction? Do we ever "over correct" the signals in a way that makes them feel less natural? Do tubes fit in here somewhere? The digital/analog thing?

 

I have no idea. Just know I'm diggin' these Cornwalls. I feel like a kid again. What's that worth? ( priceless. )

 

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On 4/14/2017 at 5:26 PM, Endo said:

I'm old enough to know better. But it occurs to me, an entire generation in this world, has grown-up without experiencing high-fidelity.

Your exactly right, and I would think it's even more than one generation.

 

Congratulations on the Cornwalls and Welcome. Love the LEITZ story. 

 

35 minutes ago, Endo said:

Is there a place for art in the science of audio?

I think there is in any good speaker, from what I have seen from the lead Klipsch Engineer is they use science as a starting point and do plenty of listening and testing until they find a compromise both are good with, everything is a compromise. And in the end it is a good blend of science and art, these designs seem to stand the test of time very well. For quality of sound, and construction it must be pretty good to last generations and still kick the but out of many "new speakers".

 

I like the name Audio Voodoo, PWK must have had it, to start a speaker company in a small town like Hope that long ago, and still be doing the same today is amazing in itself, over 70 years.

imo 

 

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