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BudP
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#1411

Post by BudP »

No Lowther driver has a voice coil that is suitable for proper midrange and above midrange reproduction. Everything above 0,18-0,20 grams (including the weight of the former material) is not suitable. If it weights more - you will always feel/hear that gravity problem to some extent, of course depending on how high your reference points are.
Not sure I understand what you mean P.H. Are you pointing to an overall lack of acceleration across the mid frequency range of 250 to 6k Hz, due to too much mass and too weak a flux field? Or do you mean that the acceleration at higher frequencies doesn't match that of lower frequencies, with a break point at the all important 800Hz, the point at which a large diameter driver ceases to move in a minimum phase manner?

I do not have an argument with your statement, just trying to see how it applies to what I am finding. I deliberately chose 300Hz as the Eminence to Lowther crossover to free the Lowther from coloration's due to extensive non minimum phase movement from the rather light weight cone construction, knowing full well that passive crossovers do not "turn off" a driver, just turn it down by -60 dB or so.

rowuk I have been dealing with that "topple" problem by moving the slant in tweeter back from flush mounted to a position that causes orchestral "height" to assume a natural position,. What you might expect from 20th row seating in a proper concert hall. I am uninterested in reproducing the spl and dynamics of live sound, as it was recorded at the microphone or closer, preferring a healthy distance in the subjective sound field illusion. So I am very interested in the perceived phase, from a vertical phantom emitter, that places each instrument properly and keeps all of the frequencies involved in that instruments expression time aligned. Having the EnABL process on all drivers does aid in this as I have coherent information off of the drivers, to around -90db from signal level. Obviously not all of those tiny signals are individually audible, but the massive over sample and pick and choose filtering of our involved sensory systems, does allow a useful understanding to arise over a time period.

As for my level of discrimination, which I assume means reference points being high enough, I have no way to express this. If you can find a local audio friend who has invested in a pair of Dave Dlugos's Planet 10 Hi Fi full range driver Fostex based monitors, please beg a listen. That will tell you more than any amount of verbiage or arm waving I might present here.
"You and I and every other thing are a dependent arising, empty of any inherent reality" Tsong Ko Pa
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rowuk
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#1412

Post by rowuk »

BudP wrote:
No Lowther driver has a voice coil that is suitable for proper midrange and above midrange reproduction. Everything above 0,18-0,20 grams (including the weight of the former material) is not suitable. If it weights more - you will always feel/hear that gravity problem to some extent, of course depending on how high your reference points are.
Not sure I understand what you mean P.H. Are you pointing to an overall lack of acceleration across the mid frequency range of 250 to 6k Hz, due to too much mass and too weak a flux field? Or do you mean that the acceleration at higher frequencies doesn't match that of lower frequencies, with a break point at the all important 800Hz, the point at which a large diameter driver ceases to move in a minimum phase manner?

I do not have an argument with your statement, just trying to see how it applies to what I am finding. I deliberately chose 300Hz as the Eminence to Lowther crossover to free the Lowther from coloration's due to extensive non minimum phase movement from the rather light weight cone construction, knowing full well that passive crossovers do not "turn off" a driver, just turn it down by -60 dB or so.

rowuk I have been dealing with that "topple" problem by moving the slant in tweeter back from flush mounted to a position that causes orchestral "height" to assume a natural position,. What you might expect from 20th row seating in a proper concert hall. I am uninterested in reproducing the spl and dynamics of live sound, as it was recorded at the microphone or closer, preferring a healthy distance in the subjective sound field illusion. So I am very interested in the perceived phase, from a vertical phantom emitter, that places each instrument properly and keeps all of the frequencies involved in that instruments expression time aligned. Having the EnABL process on all drivers does aid in this as I have coherent information off of the drivers, to around -90db from signal level. Obviously not all of those tiny signals are individually audible, but the massive over sample and pick and choose filtering of our involved sensory systems, does allow a useful understanding to arise over a time period.
Bud,

I could not agree with you more. I reference row 15 as my desirable seat, but that could very well be due to the reference hall (Frankfurt Alte Oper) itself.

I need some EnABL details, I have read a bit about it but have not done any experiments myself. Can you point me in good direction?
Whenever I feel blue, I start breathing again.
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IslandPink
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#1413

Post by IslandPink »

Have been planning a bit, if not working ( as such ) in the background .
Vinylnvalves is going to lend me his pair of Supravox 285GMF - getting those in about 10 days time.
Having e-mailed James and Simon re. crossover for 'Quasar'-style 285GMF/FE208Ez information, I've now got the crossover suggestion, attached below.
HiFi Collective (Mundorf) air-cored chokes at 8.2mH and 2mm wire , vacuum-impregnated, cost £102 each , including VAT . Ho hum, not to worry :?

Will check next with perspex suppliers who can cut to order and do two speaker holes on each piece, to avoid me messing it up ( there's enough to do without that chore ! ) .

More soon ....
Attachments
F208 EZ Quasar Filter.png
F208 EZ Quasar Filter.png (10.66 KiB) Viewed 5890 times
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pre65
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#1414

Post by pre65 »

I'd be tempted to try some cheaper inductors to make sure the value was right. :wink:
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G-Popz THE easy listening connoisseur. (Philip)
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IslandPink
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#1415

Post by IslandPink »

Info I got from James is that choke value is not so critical even from 6mH to 12mH , as it's a first-order series crossover . Hence best to fix on a choke and then adjust the caps and series resitor by ear/measurement .
"Once you find out ... the Circumstances ; then you can go out"
simon
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#1416

Post by simon »

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IslandPink
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#1417

Post by IslandPink »

Ah very good - hadn't seen that . I'll have a look at the pricing on those.
If you get chance try the BI Industries planar resistors for the 3.3R .
"Once you find out ... the Circumstances ; then you can go out"
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#1418

Post by simon »

Haven't come across those before Mark, can you point me in the right direction?
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IslandPink
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#1419

Post by IslandPink »

http://uk.rs-online.com/web/p/through-h ... s/6253373/

I think they're really transparent . It was obvious when testing attenuation on the compression driver that these were better than anything else I had.
"Once you find out ... the Circumstances ; then you can go out"
simon
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#1420

Post by simon »

Thanks Mark, I'll check them out.
Jeramy1Patraw
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#1421

Post by Jeramy1Patraw »

If you are looking for an audio frequency detector, then this one will perfectly meet your demand. it worth owning .Just come to Detectorall to learn more about it.
Lynn Olson
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#1422

Post by Lynn Olson »

Good to see the project move forward, IslandPink! I'm curious how the Supravox 285GMF works out for you in the OB configuration.
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rowuk
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#1423 Nature first

Post by rowuk »

Jeramy1Patraw wrote:If you are looking for an audio frequency detector, then this one will perfectly meet your demand. it worth owning .Just come to Detectorall to learn more about it.
Thanks, but no thanks. I already have two. They are called ears and were custom designed for me.

When my ears are not enough, I have an app for my mobile phone called "Cleartune". I not only get the frequency, but its musical relationship too!
Whenever I feel blue, I start breathing again.
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IslandPink
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#1424

Post by IslandPink »

Thanks Lynn . The Quasar if I build it close to James's plans is a known quantity . The remaining work comes in reproducing what I've found from the many experiments so far, blending the wide-range mid driver to the Azura ; and how that sounds in stereo . I'm flexible on the high-pass for the Radian now - does not need to be 600 or 700, could be 1kHz - we'll how the trade-offs sound .
One minor tweak I want t do is to put the ~4kHz notch filter for the FE208Ez into the 'lower' amp. I don't want to tamper with the simplicity of the (passive) Quasar series crossover for the bass/mid.
I should be able to install a simple parallel R-C-L 'package' in the coupling from the driver to the 300B , working against the grid-leak resistor of the 300B . I haven't got around to trying that on LT SPice, but will soon .

Meanwhile lots of components are ordered and arriving some time ( hopefully ) before Christmas :
Chokes ( 8.2mH air-core low DCR ) , perspex ( two pieces 1000mm x 460mm x 20mm each with two driver holes CNC-cut ) , some Russian 4uF /160 PIO caps , some M6 stainless countersunk bolts for fitting the front panel to the sides . Will post a picture of the 'kit' when the parts are here.
Going to get the 'loan' pair of 285GMF this weekend .

Stop press : Just got the perspex pieces. Everything looks spot-on , dimensions, hole diameters & positions .
"Once you find out ... the Circumstances ; then you can go out"
Lynn Olson
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#1425

Post by Lynn Olson »

Well, I'm still open to the option of a perspex curved-wing dipole for the upper driver, and using a GPA/Altec 416 Alnico in a 3.5 cubic foot closed box for the lower driver. EQ applied to the lower driver compensates for the dipole LF rolloff of the upper driver, and if substantial EQ is required, it can powered off its own amplifier.

Chasing box colourations out of the upper box could be a tedious exercise, considering its size and weight, so that's why I leaving the door open to dipoles or compact bass horns. Folding the bass horn screws up the time and frequency response, though, and straight horns require a fair amount of depth.

A 515 mounted in a perspex curved-wing dipole could probably handle the 700 Hz to 200 Hz range pretty well, and closed-box 416 sitting underneath it could cover the 60 Hz to 400 Hz range without any trouble. Since the floor image directly underneath the lower driver effectively doubles its efficiency and power-handling (up to 300 Hz anyway), that's a good reason to have flexible efficiency and gain-matching between the upper and lower drivers.

One possibility is to have Dave Slagle make an autoformer (or transformer) with -1, -2, and -3 dB attenuation taps, and reversible so it also provides +1, +2, and +3 dB boost taps. This effectively converts a 16-ohm driver into a driver with tapped impedances between 8 and 32 ohms.

A transformer like this is basically a 35-watt output transformer without the time and added labour of a primary winding, and a couple extra taps between the 8 and 16 ohm positions.
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