Sound Quality Vs. Measurements

Status
Not open for further replies.
You might have a point there. My audio "bible" was a book from the 1980 published by National Semiconductor, called the "Audio/Radio Handbook". A fantastic publication explaining in detail and maths how to designs whatnot, of course, based on NS op amps, but still general enough to be worth its weight in gold. Chapters are:

1) Introduction
2) Preamplifiers
3) AM, FM and FM Stereo
4) Power amplifiers
5) Floobydust (equalizers, electronic XOs, etc)

My original version is in tatters now, saying it was used is an exercise in understatement. I mentioned this as a suggestion to a fellow from the US. He hunted it down, thesedays it's published by someone else under licence from NS, and he bought two copies ($14.95 per copy), kept one as I suggested, and sent me the other one as a thank you gift. He didn't have to do that, but I am nevertheless extremely grateful.

In those days, there was no Internet and no PC, so we had to read, a bad habit I never shook off to this day, I still love to read. Reading makes you take your time and gives you time to ponder some things out, Internet is far too superficial for that.

In case anyone wants to follow up, its ISBN is:

ISBN 1-882580-35-4 51495

Yep , would love to know what I did with my original copy of the audio bible, lost track of a lot of stuff after college ... :)

As to software and sims , yes they are good tools , unfortunately Wave is correct too , you see we learnt the basics before getting software assistance , most of the x and y generation never did , so it's about sims and software for them , they lack the ability to analyze , as they never had to..

Before calculators we had to memorize formulas and tables , forward and back , problems were solved with a lot of heavy lifting , this is not necessary Today, they have lost the basics, common sense is not so common anymore ..

Common sense Basics + software analysis is where it's at , I'm very rarely impressed with any of these youngsters i hire today , exception being those coming out of the military ....
 
This months Stereophile has an interview with Arnie Nudell , on a scale of 1-10 with 10 being the biggest AO on the planet , Arnie is a solid 10.5 ..:rolleyes:

As to high sensitivity speakers , we should first define before discussing , as its a constant moving target when in discussion , for accuracy and domestic sound reproduction I don't think anyone should set out to design low sensitivity or high sensitivity speakers , the design process and performance goal will dictate such.

IMO very high sensitivity speakers (98db/w/m) don't do well with micro dynamics , as in everything in life there is always a necessary balance , finding this balance will always mean giving up some sensitivity..
 
High efficiency speaker usually make best use of the magnetic circuit . A simple improvement is a magnet behind and in front of the cone . This naturally brings other problems . Often the ultimate limit of magnetic circuits is never thought of . The very fact a coil moves in a magnetic field describes an exponential linearity problem (or similar ) . As we all know that is best solved by keeping the movement small . Other factors apply . Stupid speakers like KEF / IMF seemed to ignore that . The BBC LS 3/5A was my favorite KEF . It was designed for mobile studios ( a truck ) .
 
This months Stereophile has an interview with Arnie Nudell , on a scale of 1-10 with 10 being the biggest AO on the planet , Arnie is a solid 10.5 ..:rolleyes:

As to high sensitivity speakers , we should first define before discussing , as its a constant moving target when in discussion , for accuracy and domestic sound reproduction I don't think anyone should set out to design low sensitivity or high sensitivity speakers , the design process and performance goal will dictate such.

IMO very high sensitivity speakers (98db/w/m) don't do well with micro dynamics , as in everything in life there is always a necessary balance , finding this balance will always mean giving up some sensitivity..

Agreed.

Once you push whatever to its extreme, there will be a price to pay. Speakers are no different.

You're right in saying we should define the efficiency range. In my view 91...95 dB/2.83V/1w would efficient, above 95 dB I'd call super efficient and would be a little suspicious of them forever wondering where's the price tag.

Just a suggestion.

Also, I am VERY glad to note that the NS book was obviously so popular. It seems many of us had its tutoring as our initial stage.
 
We do all know that I think ? It's very simple , the magnetic field is changing as the coil moves out . It is a non linear system . So many other things matter and I offered a fix . Speakers are usually SE if you think about it . I like SE amps , I suspect I wouldn't applaud the fix I offered . However KEF went too far .

For what it is worth I think the medium output Klipshe were better ( 98 dB / W ) . One English guy said to me the English have hi fi and Americans have Big Fi . He went on to say a 16 foot piano keyboard is Big Fi . I like both and think you can have both easily . Trouble is I like Big fi most . That's why Quad's are right for me , no choice then .
 
Last edited:
Loudspeakers are interesting, to be sure. One thing that DOES count with speaker efficiency, is improved magnetic path and magnet, which, like compression ratio in an automobile, gives you more efficiency, no matter what else you do. Unfortunately, really good magnetic assemblies, this includes the magnet and the steel cost REAL money, and are not the first choice of 'practical' designers.
Also, horns, which will make ANY loudspeaker much more efficient, do give improved 'internal clarity' because the speaker cone has to do so little to get so much sound output. One weakness of horns, unfortunately, is that it is almost impossible to make a full range one, therefore, a 2 or 3 way horn speaker having a stepped arrival time, normally, the K-horn being an excellent example of this.
 
We do all know that I think ? It's very simple , the magnetic field is changing as the coil moves out . It is a non linear system . So many other things matter and I offered a fix . Speakers are usually SE if you think about it . I like SE amps , I suspect I wouldn't applaud the fix I offered . However KEF went too far .

Nigel, I refuse to know that because it is not all that true in my opinion. Two things here. 1) There are some very good driver designs out there with massively overhung VC's and good magnetic motors that stay linear in a wide excursion area. 2) High efficiency = large cones, which bring their own set of problems. It is much more difficult to have a large cone operate like perfect piston than a smaller one, plus the way they beam sound is something which tends to reduce the optimum listening area. Everything is a trade off, and for in the living room, I prefer relatively low efficiency drivers with wide dispersion.

vac
 
Member
Joined 2002
Paid Member
High efficiency speaker usually make best use of the magnetic circuit . A simple improvement is a magnet behind and in front of the cone . This naturally brings other problems . Often the ultimate limit of magnetic circuits is never thought of . The very fact a coil moves in a magnetic field describes an exponential linearity problem (or similar ) . As we all know that is best solved by keeping the movement small . Other factors apply . Stupid speakers like KEF / IMF seemed to ignore that . The BBC LS 3/5A was my favorite KEF . It was designed for mobile studios ( a truck ) .
.

KEF/IMF speakers were indeed inefficient. This was to a great percent due to their x-overs. Their speaker units themselves were not that inefficient. And much of their inefficiency in turn was due to the cone mass & material, not to the magnetic circuit design.
I find it a bit streched for KEF designs to be called stupid. A lot of research and know how there.
Is it that you have something more specific in your mind?

George
 
I agree with all of that about the subtleties of Linearity . Thoes words were Robin Marshall ex BBC as told to me. I think my fix is easy and worth a thought . I suspect I love the very defect I see . I prefer paper if asking .

I have just tried a Fostex full range unit which I am very pleased with ( it has taken a long time to get there ) . 300 Hz and above . The bass is 12 inch ( Leak ) . It's my friends choice to do it this way . 300 W bass and 10 W SE top . Active crossover and using FFT to integrate the units . The Fostex is in a movable unit so as to get a good phase compromise . For now filters are second order .

It sounds a bit like the Quads now .
 
.

KEF/IMF speakers were indeed inefficient. This was to a great percent due to their x-overs. Their speaker units themselves were not that inefficient. And much of their inefficiency in turn was due to the cone mass & material, not to the magnetic circuit design.
I find it a bit streched for KEF designs to be called stupid. A lot of research and know how there.
Is it that you have something more specific in your mind?

George


Sad fact is when KEF put it right everyone ignored them . I was very friendly with KEF . The 107 was not a success which surprised me ( 90 dB ) . The KEF104 AB was I think a very good design . The 104 before it more exciting . 84 dB I think is too low . However 87 dB is noticeably better . I often ran a Quad 405 dry into a typical KEF . A tip with that . Use a 405 in reverse absolute phase as it is a phase inverting amp . Transients should be positive unless recorded that way . 405's can be bought for peanuts and are useful for using at parties .

The magnetic circuit on KEF was very good . It had to be as you say as the materials needed pushing .
 
Last edited:
Loudspeakers are interesting, to be sure. One thing that DOES count with speaker efficiency, is improved magnetic path and magnet, which, like compression ratio in an automobile, gives you more efficiency, no matter what else you do. Unfortunately, really good magnetic assemblies, this includes the magnet and the steel cost REAL money, and are not the first choice of 'practical' designers.
Also, horns, which will make ANY loudspeaker much more efficient, do give improved 'internal clarity' because the speaker cone has to do so little to get so much sound output. One weakness of horns, unfortunately, is that it is almost impossible to make a full range one, therefore, a 2 or 3 way horn speaker having a stepped arrival time, normally, the K-horn being an excellent example of this.

Unfortunately this internal clarity is why they have poor micro and somewhat shouty macro dynamics ..


Nigel, I refuse to know that because it is not all that true in my opinion. Two things here. 1) There are some very good driver designs out there with massively overhung VC's and good magnetic motors that stay linear in a wide excursion area. 2) High efficiency = large cones, which bring their own set of problems. It is much more difficult to have a large cone operate like perfect piston than a smaller one, plus the way they beam sound is something which tends to reduce the optimum listening area. Everything is a trade off, and for in the living room, I prefer relatively low efficiency drivers with wide dispersion.

vac


Yes magnetic push does become more linear with under hung assemblies , unfortunately long excursion woofers bring forth other issues , as they can't stop time ...
 
Robin Marshall

Not quite the horses mouth the link below . Robin and I discussed my idea . He felt the turbulence would be it's downside . ES 14 is too inefficient I feel . Also metal tweeters not my cup of tea ( then more than now , exception SL6's) . I once said to Robin that the LS3/5A needs 500 W transient form BBC research . He said nonsense becasue he was the one that had said it ! I like that in a person to be that honest . Meridian 105 was my preferred 3/5A amp .

Epos ES 14 loudspeaker | Stereophile.com

Quote
Marshall: There's a lot special. It's a back-to-front design in that it uses a 17mm-long magnet gap and a 5mm-long coil as opposed to the normal system which is a long coil, perhaps 12 to 14mm long, working in a gap 6mm thick. This gives us linearity. It also gives us tremendous thermal stability because the coil is always totally enclosed by a huge amount of steel. Within the limits of sensitivity, you've got no real coil heating to worry about.

The only drawback is that it's horribly expensive. A 17mm-thick magnet plate is not exactly a cheap way of making a bass driver. The magnet system in our bass driver costs double the price of a complete bass driver in most loudspeakers. We pay $20 for the pieces in the magnet system. The average OEM 8" bass driver might be costing its manufacturer $10 or $12. Total, finished. Just stuff it in the box and there you are. So it's a masochistic way to make loudspeakers.
 
Last edited:
Simulation software,

I see the available simulation of today as a large bonus to students, potential problems may lie more with instructors not being able to integrate it with learning methods.
Yes I can remember setting up Kirchoff and Thevenin equivelents to try and solve a transfer function, and then pages of math, there was some insight gained along the way and significant satisfaction when completed. More insight seemed to come from the especially difficult or messy computations where it was advantageous to think of how to simply further or look at boundary cases etc.
it just seems to me that with simulators students need to be asked different questions. Quesitons which through simulation will provide the insight of circuit behavior. Also since this younger generation has grown up with such software at there finger tips, it's just not as much as a distration to actually use the tool as it is for some of us older folk.

Just my opinion
Thanks
-Antonio
 
.

KEF/IMF speakers were indeed inefficient. This was to a great percent due to their x-overs. Their speaker units themselves were not that inefficient. And much of their inefficiency in turn was due to the cone mass & material, not to the magnetic circuit design.
I find it a bit streched for KEF designs to be called stupid. A lot of research and know how there.
Is it that you have something more specific in your mind?

George

I completely agree with this statement. KEF drivers (at least the ones I know from the eighties) were well build, and also measured well. They typically had a Qts of around .37, which is the sweet spot for many designs.
 
Simulation software,

I see the available simulation of today as a large bonus to students, potential problems may lie more with instructors not being able to integrate it with learning methods.
Yes I can remember setting up Kirchoff and Thevenin equivelents to try and solve a transfer function, and then pages of math, there was some insight gained along the way and significant satisfaction when completed. More insight seemed to come from the especially difficult or messy computations where it was advantageous to think of how to simply further or look at boundary cases etc.
it just seems to me that with simulators students need to be asked different questions. Quesitons which through simulation will provide the insight of circuit behavior. Also since this younger generation has grown up with such software at there finger tips, it's just not as much as a distration to actually use the tool as it is for some of us older folk.

Just my opinion
Thanks
-Antonio

I recently tried Spice . I got so bogged down . I still use a spreadsheet . A calculator is useful , often my phone as an idea comes to me sometimes miles from home . I an terrible at arithmetic and have to recheck . Like when pico or nano farads . It matters a lot and sometimes .........! I often get people to check my stuff after , usually nothing is changed as by then I have built it . I use Burr Brown Filter Pro freeware ( I bought it originally ) . I lost my fear of Chebishev filters with that . Sometimes the best solution a Chebishev . .

http://www.ti.com/lit/an/slyt113/slyt113.pdf
 
I remember reading the NS Audio/Radio Handbook from an employer's bookshelf in the 1980's. It was my introduction to the recently departed Bob Pease. And of course, Pease famously didn't like simulation, and never used it. I'm sure he wrote a "What's all this simulation stuff, anyhow?" column at one point - I do recall him complaining about simulations in his regular column.

There ARE a lot of gotchas in spice - just getting the multipliers right in component values can be interesting. When I was first learning about electronics (as a preteen in the mid-late '60's), mF was the abbreviation for what we now call microfarads, and mmF was what we now call picofarads. Things have since standardized (or maybe the "correct" standards already existed back then) that m is 10 to the -3, u is 10 to the -6, n is 10 to the -9, and p is 10 to the -12. And of course there's nine orders of magnitude difference between an m and an M.

But when everything is good (including the component models!), complex simulations can apparently do quite well. While I haven't loaded it in, I was impressed when reading about the performance of the amplifier and its simulation earlier in this thread.
 
diyAudio Member RIP
Joined 2005
That National handbook is a classic, and a lot of credit should be given to the editor Dennis Bohn, who went on to Rane a while later. I suspect Dennis wrote a fair portion of it as well. Of course it plugs National Semi parts extensively.

I still reach for it from time to time. There are two discussions within of phono preamps, with the far more astute, if still incomplete one at the end of the book, where the honest assessment of noise taking equalization into account appears. That was reprinted with slight modification in a later National circuit compendium.


Brad
 
Status
Not open for further replies.