The problematic nature of high sensitivity drivers?

[Quakeos]

I’m not taking a shot at anyone at all here guys , I'm no engineer but I want to know your guys perspective on this. I don’t like SOME old jbl, klipsh and others with these large , high efficiency drivers due to their really quite shocking cone flex. For me personally, here’s an analogy. Imagine a violin made of chipboard , do you get a very nice mental image inside your head imaging a screechy cheap violin ? That’s to a little lesser degree how I feel about alot of high sensitivity paper woofers used in high-efficiency speakers or pro audio situations, trying to get a lighter cone among other things To get the dB up but then have to compromise on a piss poor cone stiffness , which means it will more than likely have abysmal Xmax, therefore serious lack off bass with depth , tonality and accuracy without having a behemoth-sized speaker! I have had the chance to listen to klipsh heresys numerous times and they sound fantastic but the bass is very poor IMO. again guys , I’m not calling anyone or anything out here just some food for thought with certain type model paper cones! I see the solution being stuff 100db sensitivity for people who wish to have true fidelity inside their homes and instead use Metal, ceramic , carbon , bamboo whatever you like as alternative woofers (obviously cone material is just one very brief thing in the big job of loudspeakers) and compromise on sensitivity. I DEFINITELY understand there are very excellent paper woofer drivers and I’m a big fan myself! However it seems to be with the tits high sensitivity drivers these start to be an issue.
Our rooms aren’t concerts!
What do you guys think??
I’m trying my best not to and have no intention of starting any arguments here, I just want to know your guy's thoughts.
Thanks guys ! Hope you’re all doing well

 

[TLS Guy]

Well you are confused about all this because you have never designed speakers.

First there is an absolute inverse relationship between sensitivity and bass extension.

Next we get to the matter of Q which defines the nature of the resonance of a speaker, which among other things is a weight on a spring. The weight is the moving parts, cone plus voice coil and dust cap if it has one. So if you up the weight on the spring then the spring will oscillate slower and with bigger swings,. Similarly if you make the spring softer, that will bring the same result.

So stiffer and lighter means less spring and a faster cycle. So we have a speaker with a higher fundamental resonance (Fs), but we have far less stored energy and therefore less oscillations before it comes to a stop. So it is inherently better damped. That is low Q, which is actually desirable in a speaker, but of course with the above trade offs.

So a speaker with a floppy suspension and or a heavy cone has a lot of retained energy and has a strong relatively under damped resonance and is high Q. In so many ways that is a highly deleterious trait in a loudspeaker.

As far as cone material, everyone looks for material that is very light and strong, therefore resistant to bending. When it does bend then you have cone break up. When this happens then often times you you get peaks and valleys in the driver response and beaming. If this is the case then you need to operate the driver 'in band" by proper crossover engineering. Some drivers are known as bend drivers by choice. These are drivers whose break up modes are accepted, but controlled in the design and build of the cone. This is tricky, but can be highly successful and extend operating bandwidth.

Lastly we get to the sensitivity/efficiency of the driver. The sensitivity is related to its spl at a 1 meter distance on axis with a defined input either 1 watt or 2.83 volts drive. For an eight ohm speaker it is the same number, but a four ohm speaker will take twice the power for the same voltage and be 3 db more sensitive. This relates to efficiency which is how much electrical energy is converted to sound energy and radiated into the room. Here a good speaker, with high dispersion will radiate less of its energy on axis, but more into the room as a whole, and appear less sensitive, when it may be more efficient than a more sensitive beamy speaker.

All this data is defined, by what is known as the Thiel/Small parameters of the driver, and its measured acoustic response. Before designing any speaker system this data must be known precisely for each driver.

Now this data is like the finger print and DNA of the speaker, and all are different. So that means box size, ports, crossover design, and optimal type of loading are specific for each driver. That is why you can not swap one driver for another in a given design. A driver has to be replaced with an exact replacement.

So it is essential to have a huge range of drivers at your disposal for designing speakers for lots of different applications.

Now don't confuse speakers and instruments. Instruments need lots of resonance with colorful harmonics of those resonances. For speakers, except to carefully augment lower frequencies in a controlled and precise manner, then resonance is a very bad thing, especially undamped high Q ones.

Lastly lets talk application. In speakers there is the Hoffman's Iron Law, that says there is an unbreakable inverse relationship between enclosure size and sensitivity/efficiency in the low frequencies.

So that all brings us to drivers and application. In the home and or if high spl is desired, then low efficiency is a bad thing, because it takes lots of power which heats up the voice coils which leads to dynamic thermal compression and voice coil burn out. In times gone by there were no really powerful amps. Even in a cinema 20 watts was lot of power. Hence highly efficient speakers. Every time you up sensitivity 3 db that is the same as doubling your amp power.
'
So when Altec, Klipsch, EV and JBL ruled this market, the drivers were of very high sensitivity. So the drivers did not have good bass extension. The bass was pulled up with massive back and often front loaded horns as well. Horn loading is the highest efficiency loading. The horns had exponential flare as a rule, and bass cut off frequency is entirely related to the size of the mouth. The bigger the mouth the longer the horn length has to be to get to the larger flare.

So those speakers had highly efficient drivers, horn loaded, coupled with HF units which were compression drivers on the back of mid and high frequency horns.

So in short what you are spouting about you have little understanding, and from here on out you need to read up on speaker design if you really are interested on what makes a speaker optimal for application.

Certainly if you do make good driver selection for application you will have a lousy speaker. Good design starts with intelligent selection. That is always the stating point and the more choices the merrier.

 

[highfigh]

The screeching of a violin bow on the strings has nothing to do with the materials used for the neck and body, it's from bad bowing technique (unless it's intentional). Rosin is applied to the hair to increase friction and when bowing, the hair pushes or pulls the strings in the direction of the bow's travel and, because the tensile strength and tension in the string prevents it being pushed by that amount of friction indefinitely, it releases and moves back to some previous position. The tension & mass of the string determine the fundamental frequency but it's similar to rubbing a wet finger on clean glass- it will grab and release.

 

[Quakeos]

Well you are confused about all this because you have never designed speakers.

First there is an absolute inverse relationship between sensitivity and bass extension.

Next we get to the matter of Q which defines the nature of the resonance of a speaker, which among other things is a weight on a spring. The weight is the moving parts, cone plus voice coil and dust cap if it has one. So if you up the weight on the spring then the spring will oscillate slower and with bigger swings,. Similarly if you make the spring softer, that will bring the same result.

So stiffer and lighter means less spring and a faster cycle. So we have a speaker with a higher fundamental resonance (Fs), but we have far less stored energy and therefore less oscillations before it comes to a stop. So it is inherently better damped. That is low Q, which is actually desirable in a speaker, but of course with the above trade offs.

So a speaker with a floppy suspension and or a heavy cone has a lot of retained energy and has a strong relatively under damped resonance and is high Q. In so many ways that is a highly deleterious trait in a loudspeaker.

As far as cone material, everyone looks for material that is very light and strong, therefore resistant to bending. When it does bend then you have cone break up. When this happens then often times you you get peaks and valleys in the driver response and beaming. If this is the case then you need to operate the driver 'in band" by proper crossover engineering. Some drivers are known as bend drivers by choice. These are drivers whose break up modes are accepted, but controlled in the design and build of the cone. This is tricky, but can be highly successful and extend operating bandwidth.

Lastly we get to the sensitivity/efficiency of the driver. The sensitivity is related to its spl at a 1 meter distance on axis with a defined input either 1 watt or 2.83 volts drive. For an eight ohm speaker it is the same number, but a four ohm speaker will take twice the power for the same voltage and be 3 db more sensitive. This relates to efficiency which is how much electrical energy is converted to sound energy and radiated into the room. Here a good speaker, with high dispersion will radiate less of its energy on axis, but more into the room as a whole, and appear less sensitive, when it may be more efficient than a more sensitive beamy speaker.

All this data is defined, by what is known as the Thiel/Small parameters of the driver, and its measured acoustic response. Before designing any speaker system this data must be known precisely for each driver.

Now this data is like the finger print and DNA of the speaker, and all are different. So that means box size, ports, crossover design, and optimal type of loading are specific for each driver. That is why you can not swap one driver for another in a given design. A driver has to be replaced with an exact replacement.

So it is essential to have a huge range of drivers at your disposal for designing speakers for lots of different applications.

Now don't confuse speakers and instruments. Instruments need lots of resonance with colorful harmonics of those resonances. For speakers, except to carefully augment lower frequencies in a controlled and precise manner, then resonance is a very bad thing, especially undamped high Q ones.

Lastly lets talk application. In speakers there is the Hoffman's Iron Law, that says there is an unbreakable inverse relationship between enclosure size and sensitivity/efficiency in the low frequencies.

So that all brings us to drivers and application. In the home and or if high spl is desired, then low efficiency is a bad thing, because it takes lots of power which heats up the voice coils which leads to dynamic thermal compression and voice coil burn out. In times gone by there were no really powerful amps. Even in a cinema 20 watts was lot of power. Hence highly efficient speakers. Every time you up sensitivity 3 db that is the same as doubling your amp power.
'
So when Altec, Klipsch, EV and JBL ruled this market, the drivers were of very high sensitivity. So the drivers did not have good bass extension. The bass was pulled up with massive back and often front loaded horns as well. Horn loading is the highest efficiency loading. The horns had exponential flare as a rule, and bass cut off frequency is entirely related to the size of the mouth. The bigger the mouth the longer the horn length has to be to get to the larger flare.

So those speakers had highly efficient drivers, horn loaded, coupled with HF units which were compression drivers on the back of mid and high frequency horns.

So in short what you are spouting about you have little understanding, and from here on out you need to read up on speaker design if you really are interested on what makes a speaker optimal for application.

Certainly if you do make good driver selection for application you will have a lousy speaker. Good design starts with intelligent selection. That is always the stating point and the more choices the merrier.

Hi TLS, thank you for your reply. I have designed several loudspeakers myself and I have a basic enough understanding to hear everything your saying and I totally agree, but I personally don't think I addressed my point well enough. I was referring to older model vintage speakers with very atypical pressed paper cones. And the violin was just an analogy but not to be taken seriously! The point I'm trying to get at is when I personally think of these drivers, I dont picture good sound. Of course on paper, high sensitivity has zero correlation to do with bass output, HOWEVER, it is the process of in real life to achieve these high sensitivities in a driver that isnt very large (lets just leave 15 and 18" out for a second here) they have to have abysmal xmax, very light duty construction cones, small triple roll surrounds etc... which then means it suffers low-frequency extension. I've never successfully heard an old, vintage, high sensitivity paper pressed paper driver putting out accurate, deep powerful bass. In a smaller summary, that's the idea I'm trying to express here, and just wanted to share my thoughts with you guys, and most of us don't want our music to be playing at 120db either, so I understand what I'm saying is almost like "yeah no kidding" and the modern interpretation of these speakers have addressed these issues but it was rather food for thought, seeing how loudspeakers have evolved.

 

[Quakeos]

The screeching of a violin bow on the strings has nothing to do with the materials used for the neck and body, it's from bad bowing technique (unless it's intentional). Rosin is applied to the hair to increase friction and when bowing, the hair pushes or pulls the strings in the direction of the bow's travel and, because the tensile strength and tension in the string prevents it being pushed by that amount of friction indefinitely, it releases and moves back to some previous position. The tension & mass of the string determine the fundamental frequency but it's similar to rubbing a wet finger on clean glass- it will grab and release.

I appreciate your feedback and it certainly sounds like the case,

however, it was just a simple analogy, and never intended to be taken seriously.such as if for example, I told you to close your eyes and think of a really crap speaker, you will just think of and be reminded of a crappy sound.

 

[lovinthehd]

Christian Murace I assume?

 

[Quakeos]

Christian Murace I assume?

You may have seen my posts yes.

 

[lovinthehd]

You may have seen my posts on social media Groups

It would have been a bizarre coincidence otherwise You might post up some of your speaker builds and the DIY subforum might be the best place for the discussion....

 

[Quakeos]

It would have been a bizarre coincidence otherwise You might post up some of your speaker builds and the DIY subforum might be the best place for the discussion....

Thanks lovinthehd, I’ll be sure to in future

 

[TLS Guy]

Hi TLS, thank you for your reply. I have designed several loudspeakers myself and I have a basic enough understanding to hear everything your saying and I totally agree, but I personally don't think I addressed my point well enough. I was referring to older model vintage speakers with very atypical pressed paper cones. And the violin was just an analogy but not to be taken seriously! The point I'm trying to get at is when I personally think of these drivers, I dont picture good sound. Of course on paper, high sensitivity has zero correlation to do with bass output, HOWEVER, it is the process of in real life to achieve these high sensitivities in a driver that isnt very large (lets just leave 15 and 18" out for a second here) they have to have abysmal xmax, very light duty construction cones, small triple roll surrounds etc... which then means it suffers low-frequency extension. I've never successfully heard an old, vintage, high sensitivity paper pressed paper driver putting out accurate, deep powerful bass. In a smaller summary, that's the idea I'm trying to express here, and just wanted to share my thoughts with you guys, and most of us don't want our music to be playing at 120db either, so I understand what I'm saying is almost like "yeah no kidding" and the modern interpretation of these speakers have addressed these issues but it was rather food for thought, seeing how loudspeakers have evolved.

Let me first point out that on paper high sensitivity has everything to do with limited bass extension as there is an absolute inverse relationship between flux density and bass extension.

Actually the old vintage drivers are just that. It would be surprising if cone, suspension, surround, and motor systems had not progressed over 80 years plus.

However even then, I think properly used some vintage drivers are not as bad as you maintain. Then as now there has been the spread between junk and excellence.

The first speaker that had any high-Fi pretensions at all was Paul Voight's driver in his Voight corner horn. It had a massive electro magnet. This line continues in the Lowther line of speakers, of small paper coned extremely high flux density horn loaded speakers,

The Altec Voice of the theater and similar products from EV and JBL, where all developed with the cinema in mind. The cinemas back then were larger than now. Power amps were low powered and primitive. So the order of the day, was good coverage of these huge spaces with good spl. and high speech intelligibility.
So you had these massive systems, of which the Altec Voice of the theater was the best known, most widely used and iconic. Do not forget that Thiel and Small had not yet published their famous paper and gave us the first mathematical model for the interaction of driver and cabinet. This of course led to a massive improvement.

The sentinel dates are:-

1825 Kellog and Rice, on moving coil drivers.

1954 and the fifties era: - Harry F. Olson, Bereneck et al with Elctroacoustic analogous circuits.

1961 Thiel and Small with there famous paper in Australia. Only Raymond Cooke CEO and founder of KEF grasped the significance of this paper. So KEF were the first to design drivers and cabinets using this model. The KEF factory at Tovil just outside Maidstone on the banks of the River Medway, was just 15 miles up river from where I lived. So as a curious kid of 14, I had a birds eye view and up close encounter of this momentous development. The first driver designed using these principles was the KEF B 139 bass driver. It is still one of the very best bass drivers of all time. I have 8 in my possession, with six in regular use. The work was not published outside Australia until 1971, when there work was published in the AES journal. So that is the date when improvements in loudspeakers really took off.

Amplifiers were also crude. 1949 was a pivotal year, when British engineer D.T.N. Williamson published his Williamson amp. This was the first amplifier to achieve 0.1% THD. It is widely considered the start of the Hi-Fi era. He worked closely with Peter Walker of Quad and Harold J. Leake to develop increasingly powerful high quality tube amps. Harold Leake in particular produced a range of beautifully crafted tube amps from 10 to 50 watts in the fifties. The Mullard tube manufacturer published excellent amp circuits back then for the DIY builder, which I built as a kid. I built a 33, a 10/10 for myself and a couple of 10s for others. I still have the 10/10. So Hi-Fi as we know it really did start in the UK, and set in train that era of the "Golden Age" of British Audio.

The point is that it took tandem developments in speakers and amplifiers to start the foundation of what we enjoy today.

The fact that a well restored Voice of the Theater set up sounds as good as it does is close to a miracle. Those products defined Cinema sound for generations. Actually I believe they are worthy of great praise and not criticism for what they achieved with so little to give so much pleasure to millions, especially during the dark days of the second world war.

 

[highfigh]

I appreciate your feedback and it certainly sounds like the case,

however, it was just a simple analogy, and never intended to be taken seriously.such as if for example, I told you to close your eyes and think of a really crap speaker, you will just think of and be reminded of a crappy sound.

A better example would be an acoustic guitar made of cheap materials- I was looking for something smaller & better for finger picking but most of what I found sounded like something from Sears or Montgomery Ward when they sold mail order by catalog, even if they weren't particularly cheap.

When I think of crap speakers, a lot of brands come to mind and I have heard many in over 40 years in the audio business.

 

[Johnny2Bad]

All things being equal, higher efficiency (high sensitivity) wins every time. Amongst it's desireable qualities is generally superior temperature handling which tends to reduce power compression, and leaving more money in the system kitty for other components given an in-room SPL requirement.

Of course, all things are rarely equal, so it's just one aspect that would need to be defined. But dismissing them out of hand is, in my opinion, a mistake.

 

[Swerd]

The Altec Voice of the theater and similar products from EV and JBL, were all developed with the cinema in mind. The cinemas back then were larger than now. Power amps were low powered and primitive. So the order of the day, was good coverage of these huge spaces with good spl. and high speech intelligibility.
So you had these massive systems, of which the Altec Voice of the theater was the best known, most widely used and iconic. Do not forget that Thiel and Small had not yet published their famous paper and gave us the first mathematical model for the interaction of driver and cabinet. This of course led to a massive improvement.

Thanks for your informative history lesson.

I often read posts extolling the benefits of hi-sensitivity speakers from people too young to remember when amps were low powered and expensive -- more expensive than good speakers. Over the years, the opposite has become true. Good amps are powerful and cheaper than good speakers.

 

[Johnny2Bad]

Minor addendum

" ... 1961 Thiel[sic] and Small with there[sic] famous paper in Australia. ..."

Although both were working in Australia at the time, Theile is Australian, Small is American.