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Old 12th May 2012, 01:13 PM   #5391
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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 .
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Old 12th May 2012, 01:21 PM   #5392
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Quote:
Originally Posted by gpapag View Post
.

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 by nigel pearson; 12th May 2012 at 01:26 PM.
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Old 12th May 2012, 01:32 PM   #5393
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by john curl View Post
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 ..


Quote:
Originally Posted by vacuphile View Post
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 ...
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Old 12th May 2012, 01:36 PM   #5394
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Default 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

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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 by nigel pearson; 12th May 2012 at 01:40 PM.
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Old 12th May 2012, 01:36 PM   #5395
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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
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Old 12th May 2012, 01:50 PM   #5396
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Quote:
Originally Posted by gpapag View Post
.

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.
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Old 12th May 2012, 03:11 PM   #5397
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Quote:
Originally Posted by magnoman View Post
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
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Old 12th May 2012, 04:12 PM   #5398
benb is offline benb  United States
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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.
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Old 12th May 2012, 05:00 PM   #5399
bcarso is offline bcarso  United States
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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
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Old 12th May 2012, 05:11 PM   #5400
Pano is online now Pano  United States
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Quote:
Originally Posted by a.wayne View Post
Unfortunately this internal clarity is why they have poor micro and somewhat shouty macro dynamics ...
Bad crossovers are the more likely culprit, IME.
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