Something stirs in the Undergrowth

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chris661
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#1921 Re: Something stirs in the Undergrowth

Post by chris661 »

IslandPink wrote: Sun May 14, 2017 8:05 pm Bit more detail work today, ready for assembly of the slot bit ( and perhaps some lash-up of OB ) tomorrow.
Just tested the Supravox for resonance in open air using the series resistor and voltmeter method. Came in at 54.5Hz. Maybe it would get closer to the datasheet value of 47Hz with more running-in ? - maybe not.
I dropped the resonance on a 15" from 45Hz down to 38Hz, so it's possible yours will do similar.
For a silent break-in, I recommend pink noise with a steep low-pass filter at 20Hz. That just puts very-low-frequencies through the driver. It's quite peaky, so there won't be much heating in the driver but you should get plenty of movement to loosen everything up.

Chris
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IslandPink
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#1922 Re: Something stirs in the Undergrowth

Post by IslandPink »

Thanks. I'll probably just put some 30Hz or something though there from a sig gen & get it moving a few mm. That's the easiest for me, have done it on other drivers.
James said he's going to measure one of his to compare.
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IslandPink
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#1923 Re: Something stirs in the Undergrowth

Post by IslandPink »

Just got the (correct) Faital 8FE200 driver from CPC.
http://www.faitalpro.com/en/products/LF ... =401030100
Well this does sound like a driver I can work with :D
Straight out of the box and playing resting on the floor, it's making music . Has good midrange tone and a dynamic 'alive' sound with low-level detail. The hunch based on the high Qm ( 13 ) and low Rms did pay off.
It's not without its faults, the bumps and spikes above 2kHz are pretty aggressive on-axis, but with a 2mH choke in series it sounds a lot better behaved and still has good tone. The plan will be for this to provide the midrange fundamentals and start rolling from 500Hz ; 1st-order first then steepening to 2nd-order. If need be, I will apply some ideas like a suspended phase plug or ring ( near the centre or edge ) to tone down any nasties.
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IslandPink
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#1924 Re: Something stirs in the Undergrowth

Post by IslandPink »

OK moving ahead with the 'SLOB' now .
Just assembled the main bit,( See pic - nice bit of French bling fitted )...
Slob_3.JPG
... done a test and a bit of listening with some makeshift baffle parts .
First thing, resonance of the 285GMF has gone down from 54.5Hz to 36Hz with the slot loading.
Listening - well, too early really as I need to improve the baffle a fair bit and get a decent low-pass on there in approx. the right place. I will say that it seems pretty inefficient in the bass and low bass compared to the midrange, though :? not what I wanted.
However bass notes have good tone and there's some 'kick' even though the bass is pretty quiet, so maybe the phase is good. More soon...
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IslandPink
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#1925 Re: Something stirs in the Undergrowth

Post by IslandPink »

Ooh, now hang on I think this project has legs.
Still taking shape as far as the baffle engineering goes ( why does everything here have big holes cut in it ? ) but has taken a big step up in bass output & quality.
Slob_4.JPG
Slob_5.JPG
I've got something like a 240Hz low-pass on the SLOB now and the Faital 8FE200 on the floor for mids. Not expecting anything out of this but a way of getting some idea of what the bass is doing, but this afternoon I played track 5 from 'Tago Mago' which I normally fast-forward through and it sounded really interesting.
Then more significantly for low bass, just now I was going through Don Juan's Reckless Daughter by Joni and the Jaco low-note on 'Overture' has more of the fundamental there than I've heard recently. Then, further on the big drum on 'Dreamland' stopped me in my tracks - sounded properly like a big drum with real impact and tone. That's the best I've heard it.
So, onwards and upwards with the wood-scavenging.
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andrew Ivimey
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#1926 Re: Something stirs in the Undergrowth

Post by andrew Ivimey »

ummmmmmmmmmmmmm pardon me for breathing but I don't think any woofer/dooffer is going to sound any good placed on the base of the speaker cab/open baffle arrangement ...
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#1927 Re: Something stirs in the Undergrowth

Post by IslandPink »

And why not my dear fellow, please explain yourself with diagrams. I have got other options, mind you ...
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#1928 Re: Something stirs in the Undergrowth

Post by IslandPink »

I was only joking about the diagrams .... are you thinking of a driver that needs to go up to 300 or 400Hz ?

Meanwhile, I've been applying the Salt Test to the 8FE200 :
SaltTest1.JPG
This with a signal generator feeding a small amp and scanning through frequencies above 1kHz to see if I could determine anything about resonant areas.
Now at first I thought I could just rely on the salt to move away from the areas of max amplitude and identify the clear(ed) bands .
SaltTest2.JPG
However after a few minutes I realised that the whole cone is slightly convex radially, so you can see salt move away from different zones depending on exactly how you tilt the driver. So the above pic & markings proved to be wrong.
So my further work was done by tilting the driver back & forth and watching the salt run across zones of the cone at a frequency of interest, and see where it was bouncing up & down most as it drifted across. This gave me more believable & repeatable data.
I identified a few frequencies of interest from listening and from looking at the datasheet for peaks . What I found in terms of location on the cone is as follows :
1.25kHz : Most of cone together but interestingly outer 20% hardly moving
1.6kHz : outer edge of cone & border into accordion surround
2.5kHz : Near outside , about 80% of cone radius
3.4 to 3.5kHz : about half-way out or a bit more - 50 to 60% cone radius
4.8 to 5kHz : join of dustcap to cone inner

So my plan to use an annular ring mask to kill some spikes is not so good - too many areas contributing different peaks.
I think I will hang a phase-plug ( being made soon , rapid prototype based on previous one used in horn ) in front of the dustcap & join , which will blend the dustcap & cone movements together in that area ( should still capture midrange output ) , then take a razor blade to the cone & try & apply some of those ScanSpeak-style slices diagonally from approx the 50% to the 90% region. if something terrible happens, the driver only cost £47 so I can get another couple. I think I'll try two slices 180 deg apart and do them and let the glue ( most likely PVA ) dry, before trying some more.
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IslandPink
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#1929 Re: Something stirs in the Undergrowth

Post by IslandPink »

In for a penny in for a pound.
It's fair to say I've probably invalidated the warranty on this driver :
Faital_cuts1.JPG
So I sketched-out the first two diagonal cuts from about 20% to 90% of the paper cone width with a 2B pencil.
Based it sort-of on some pics of the Scanspeak sliced-cones.
Took a single-edged razor blade and cut through. The cone did not collapse or horribly distort when I did this - the edges stayed together - yippee ! first success. Then I chamfered the front edges ( the cone has a bit of thickness to it ) a bit, to make a little trough about 1 to 2mm wide for the PVA adhesive to sit in.
Then the messy bit, I used a standard PVA wood glue bottle/nozzle to apply the glue. Not really ideal. Quite a bit of overspill, then also some running of the first glue line when I tilted the cone over to apply the second glue line. Probably won't make much difference to the sound. I wanted the glue to sit in the cut a bit to work down and penetrate before removing it. Then I wiped back a bit with kitchen roll.

So, I'll leave this to dry about 3 hours then try a tentative listen at moderate volumes. If nothing has gone horribly wrong I'll do another two or four cuts tomorrow.

edit : Sorry forgot to mention that before putting the PVA into the cuts, I'd applied some pieces of masking tape to the back of the cone to prevent it leaking through.
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#1930 Re: Something stirs in the Undergrowth

Post by IslandPink »

OK just testing now. I made the mistake first of listening to the driver without having removed the masking tape on the back and it sounded OK but a bit dead and lacking in low-level detail. Once that was gone now it sounds a bit more lively and really quite a bit better near-axis, lots of the harshness has disappeared. the guitar notes have lost some edge, but that maybe of no consequence once the horn is blended in above 700Hz. This is without any crossover in the amp or at the speaker. Onwards and upwards with two more cuts tomorrow evening and that may well be enough !
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#1931 Re: Something stirs in the Undergrowth

Post by IslandPink »

More on the driver mods later.
Meanwhile :
http://hifipig.com/birds-eye-view-of-hi ... and-fun/2/
I hate him I hate him I hate him !! how has he made it work ? :
"Living Voice are very much the epitome of High End. Their room always sounds great, and so it should with them making loudspeakers that cost hundreds of thousands of pounds and matching them with electronics from the likes of Kondo which cost similar. However this year, and we were not the only ones to notice, their room was totally singing. The Vox Palladian system was visually beautiful, the sound had gone up to another level, from a level that seemed impossible to improve on from last year, it was totally captivating. Plus Kevin put on some dub for us, just showing that High End people don’t just play classical on their very expensive systems….thanks for the experience guys!"
Keep working on the pretext for a visit Nick !
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#1932 Re: Something stirs in the Undergrowth

Post by Cressy Snr »

Living Voice - speakers for the jet set. :D
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chris661
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#1933 Re: Something stirs in the Undergrowth

Post by chris661 »

Lets take a look at that Living Voice system...

The box behind the main speaker is some kind of horn subwoofer. The size, circular cutouts and website description make it sound awfully similar to the LABhorn, a 2x12" FLH.

A few notes from my observations...
- the midrange and midbass horns appear to match in exit angles, so they'll have similar dispersion around the crossover frequency.
- the whole thing appears to be mechanically time-aligned.
- they're using external crossovers. They're big boxes, and there's no telling what voodoo might be in there.
- the whole system is horn-loaded.


Chris

More from the website, copy and pasted below. I think it reveals quite a lot.
"The main system features the Vox Palladian and Palladian Basso horn loudspeaker system. Weighing in at 800kgs this is a 5-way fully horn loaded design, housed in two pairs of enclosures with a bandwidth of 20Hz to 45kHz. The Palladian Basso bass system is a folded exponential horn driven by a pair of long-throw high power drivers with reinforced paper diaphragms.

These drivers are powered by a 500watt MOSFET bass amplifier with 36dB/octave low pass filtering and modest EQ covering the frequency range 20-70Hz, where it crosses over to the Vox Palladian, which covers the lions share of the frequency range, operating from 70Hz upwards with a sensitivity of 105dB/w @1m.




LF drive unit is the Vitavox 151, a massively constructed 15″ bass driver designed specifically for horn loading. It uses a 2.1kg AlNiCo magnet to focus 1.4 Tesla onto the small 57mm diameter voice coil. This motor system drives a very light (45gm) straight sided paper pulp diaphragm with extreme precision.

The driver is loaded into the folded exponential horn geometry through a phase correction plug that ensures that the integrity of the pressure wave at the diaphragm is preserved at the mouth of the horn. This mid bass system operates from 70Hz – 400Hz.




The MF drive unit is the Vitavox S2 compression driver with proprietary diaphragm of chemically hardened aluminium. Its 1.4 Tesla AlNiCo magnet drives a featherweight 3″ diameter aluminium diaphragm of just 50 microns thickness.

This driver is coupled to a radial exponential horn development through a complex phase correction plug. This driver system operates between 400Hz and 5kHz with dispersion at crossover of 90 degrees horizontally, and 120 degrees vertically.




The HF drive unit is a Living Voice modified TAD TD-2002. This employs a 48mm Beryllium diaphragm formed by a process of high purity vacuum evaporation that weighs only 0.13 of a gram.

A powerful ALNiCo magnet produces a flux density of 19.5K Gauss. It is loaded to a unique proprietary Living Voice horn geometry machined from LG2 bronze. The high frequency system is operating 5 kHz – 15kHz.




Ultra high frequency drive unit is the Vitavox T9: It uses a 1kg AlNiCo magnet with 1.4 Tesla to energise a tiny 30 micron thick aluminium ring.

A symmetrical exponential horn with bullet shaped phase plug provides output from 15kHz – 40 kHz with 30 degrees of horizontal and vertical dispersion.

This unit has been developed specifically for the Living Voice Vox Palladian loudspeaker system in conjunction with Vitavox."
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Nick
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#1934 Re: Something stirs in the Undergrowth

Post by Nick »

I think Marks question was "how has he made it work" not whats in the boxes.
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ed
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#1935 Re: Something stirs in the Undergrowth

Post by ed »

Nick wrote: Thu May 25, 2017 10:24 am I think Marks question was "how has he made it work" not whats in the boxes.
Couldn't the answer to that question have something to do with the ingredients?

as an aside, full marks for over the top.
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