Fane 12-250TC Retro Speaker.

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Scottmoose
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#16 Re: Fane 12-250TC Retro Speaker.

Post by Scottmoose »

Cressy Snr wrote: Sun Mar 25, 2018 5:33 pm I'm not doing it - too small a room; but these drivers would IMO, do really well on an open baffle running wide open, with a 15, or better still, an 18 inch bass helper underneath them.
Box size the issue Steve? FWIW, two things you might want to look at:

1/ Shift to a quasi-aperiodic load. I don't like the aperiodic term as it's not accurate but you know what I mean. ;) Dates from the dawn of time, they were fooling with these in the '30s so novel it isn't. Get your sealed box (say, about 60 litres) with a reasonable amount of internal damping, drill about 40 holes in it & make sure they're covered internally with damping. That should bleed off enough pressure without resonanting to reduce the box Q a bit.

2/ Electrical equivalent. Well, not really, but it's sometimes done with woofers in an undersized box to damp down the LF. Not especially well-known, but it's been done for years. Same box size & stick a ruddy great cap in series with the driver. Probably about, oh, call it 150uF should be a reasonable compromise. Done right you end up with a response curve that follows a similar shape to an EBS vented box; the cap compensates for the rising response caused by the high box Q, until you reach the impedance rise at resonance, where the response will flattens out a bit as you'd expect before dropping away again. TBH, I don't recall seeing anybody do this with wideband drivers, just woofers, although it will certainly have been done at some point. Nothing new under the sun.
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#17 Re: Fane 12-250TC Retro Speaker.

Post by Cressy Snr »

Thanks for that Scott....interesting; the colander speaker :)
Box size is not really an issue with these drivers, I was just commenting on the fact that the TS parameters would IMO, also make it a great driver for use on a baffle, for those of us into OBs.
I'm quite happy doing a sealed box with it.
Last edited by Cressy Snr on Mon Mar 26, 2018 3:12 pm, edited 1 time in total.
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#18 Re: Fane 12-250TC Retro Speaker.

Post by Cressy Snr »

pre65 wrote: Mon Mar 26, 2018 11:02 am I'd be interested to see what size they were going to be Steve, I'm still thinking about my 12" drivers in a semi omni.
A 100L enclosure is what I'm going for 450x800x300 (WxHxD) for a basic rectangular box.
Mine will be a little taller to account for the taper, or I'll lose volume.

Your drivers might need a different size box, depends on the TS parameters and what kind of loading
you want (ported, sealed, TL)
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#19 Re: Fane 12-250TC Retro Speaker.

Post by IslandPink »

Scott - the driver Q is already pretty high ( >0.6 ) - more OB than sealed - will it work for aperiodic ?
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#20 Re: Fane 12-250TC Retro Speaker.

Post by Scottmoose »

Cressy Snr wrote: Mon Mar 26, 2018 3:06 pm Thanks for that Scott....interesting; the colander speaker :)
Box size is not really an issue with these drivers, I was just commenting on the fact that the TS parameters would IMO, also make it a great driver for use on a baffle, for those of us into OBs.
I'm quite happy doing a sealed box with it.
Got you. Brain not working.

You might want to look at going semi-aperiodic anyway though with 100 litres if it's going to be near a wall; Q is a touch high & you may have some bass peaking < 150Hz. Not much, but worth keeping in mind in case of need. Simplest version of all -don't seal the driver too tightly to the box. ;)
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#21 Re: Fane 12-250TC Retro Speaker.

Post by Scottmoose »

IslandPink wrote: Mon Mar 26, 2018 3:25 pm Scott - the driver Q is already pretty high ( >0.6 ) - more OB than sealed - will it work for aperiodic ?
Sure, providing you're not attempting to get a lower system Q than the driver's capable of. The main value of a leaky sealed box / quasi aperiodic for me is allowing a smaller cabinet size for a given system Q. The slightly easier impedance is nice to have too.
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#22 Re: Fane 12-250TC Retro Speaker.

Post by Cressy Snr »

Scottmoose wrote: Mon Mar 26, 2018 3:28 pm
You might want to look at going semi-aperiodic anyway though with 100 litres if it's going to be near a wall; Q is a touch high & you may have some bass peaking < 150Hz. Not much, but worth keeping in mind in case of need. Simplest version of all -don't seal the driver too tightly to the box. ;)
Aye, Nice little classic +3dB hump around 60Hz followed by 12dB/octave rolloff, with my 100L box. Should give a nice "punchy" bass. Not strictly accurate but with a bit of care, should be nice and tight, which is exactly what I'm looking for. Should be able to get a decent balance below resonance, with the cabs about 6" out. Driver will be around 2' 6" off the floor.
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#23 Re: Fane 12-250TC Retro Speaker.

Post by Ray P »

IslandPink wrote: Mon Mar 26, 2018 11:19 am I really had no idea what those are, until I looked them up...
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#24 Re: Fane 12-250TC Retro Speaker.

Post by Cressy Snr »

I found this nice little chart on the 'net.
Image
Haven't seen it in over twenty years.
Last edited by Cressy Snr on Fri Mar 30, 2018 6:34 pm, edited 1 time in total.
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#25 Re: Fane 12-250TC Retro Speaker.

Post by Cressy Snr »

Reduced the box volume to 80L. Best compromise between size and bass performance. 80L is the point of diminishing returns ie box needs to become exponentially bigger for only a couple of Hz reduction in resonance. Little point in going over 80L

Nice little weeekend project for the Easter holiday, off for some sheet materials tomorrow, to build a prototype.

Had the bare drivers going again this afternoon, with our Ant and the missus being the 'ears' We agreed that these buggers are
absolute stunners. No need for tweeters, so ultimate simplicity.
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#26 Re: Fane 12-250TC Retro Speaker.

Post by Ant »

I cant work out how they made the things go so high and not sound harsh at all.
Stick your ear in it and move your head up and down relative to the cone, the thing seems to be playing different frequencies. Like a uni q or a tannoy dual concentric. The cone and the 2 wizzers output seem to be integrated very well.
Uncanny for a big driver
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#27 Re: Fane 12-250TC Retro Speaker.

Post by ed »

Watching this with hyper interest Steve....

are you still thinking about sealed box?.....I just did the sums on that driver and it comes out at 354 litres tuned to 55hz Butterworth.

I'm intrigued because I was playing with sealed before I gave up a few years back. I still have the seas fa22s which were made for sealed boxes, but they're still gathering dust. If memory serves they want 80 litres but they're chalk and cheese to the drivers you have...

I'm tempted to revisit the whole closed box thing.
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#28 Re: Fane 12-250TC Retro Speaker.

Post by Ant »

For a laugh I made a pair of sealed box subs last week using a pair of very cheap 12" qtx drivers and a pair of cardboard boxes that were 18x18x14 inch. Loads and loads of parcel tape to seal them up properly. and they were quite nice. Wired them up in parallel with the mets.

Then the wife saw them and the fun was over......
They were abit 'boxy' in hindsight.......
I quite like sealed boxes
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#29 Re: Fane 12-250TC Retro Speaker.

Post by Cressy Snr »

ed wrote: Fri Mar 30, 2018 8:16 pm Watching this with hyper interest Steve....

are you still thinking about sealed box?.....I just did the sums on that driver and it comes out at 354 litres tuned to 55hz Butterworth.
Yep, sealed it is.
With my original 100L enclosure the cutoff frequency I get is 59 Hz.

Trying different enclosure volumes, it seems that 80L is the point of diminishing returns. At 80 litres, I get a 60 Hz cutoff, increasing box size beyond that, shifts the cutoff barely at all (59 Hz @100L , 58 Hz @ 120L, 57 Hz @ 200L, 55Hz @ 350L). So why not just accept 60Hz and go from there, was my reasoning.

OK, the system Q is 0.89 at that size, but to be perfectly honest, I never found raised Q to be a problem with the sealed designs I was doing in the late 70s, with cheap paper cone drivers, cabs rammed up against walls, provided said Q didn't go above 1.
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#30 Re: Fane 12-250TC Retro Speaker.

Post by Cressy Snr »

Here's the "back of a fag packet" design.
Cab is 12 inches deep externally and built from 3/4 inch sheet. Don't you just love the organic approach.
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