Something stirs in the Undergrowth

Dedicated to those large boxes at one end of the room
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IslandPink
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#2086 Re: Something stirs in the Undergrowth

Post by IslandPink »

You're confusing me with someone who is a current expert on where to get them :D ( bought mine in 2009 -ish )
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simon
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#2087 Re: Something stirs in the Undergrowth

Post by simon »

According to the Aurum Cantus website the only dealer in the UK is Absolute Analogue, but I couldn't find any info on their website.

http://www.aurumcantus.com/aurumcantus- ... s3-uk.html
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Ali Tait
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#2088 Re: Something stirs in the Undergrowth

Post by Ali Tait »

Ok thanks chaps, will have a scout around. Fancy trying a pair.
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#2089 Re: Something stirs in the Undergrowth

Post by IslandPink »

They do look a bit scarce, having checked EBay . :(
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#2090 Re: Something stirs in the Undergrowth

Post by Ali Tait »

Parts Express have them at good prices, there will be shipping and customs on top though..
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#2091 Re: Something stirs in the Undergrowth

Post by IslandPink »

I remember paying over £400 for the pair about 8 years ago, so that's probably as good as you can get. I had a look for other units, the G2Si is the next best, couldn't find anything from Fountek that was quite right. Next level up would be the RAAL ones :D
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#2092 Re: Something stirs in the Undergrowth

Post by IslandPink »

More crossover tweaking this afternoon. Bass sounded a bit heavy/loose after more listening, I have just grappled with removing the 100uF Mundorf cap in the series crossover, now got a 65uF GE polyprop/oil in there, I can clip-lead in extra 20u/30u/40u . I reckon the sweetspot is somewhere around 85uF for this, with the FX120 pair ( which is 16ohm together ) - a touch lower than the original Quasar.
I will do a bit more on the mid/HF cross later. Once I've got it more or less nailed for a mono speaker I'll try out the 2x2 mid array. Final crossover values might need to be tweaked when it's stereo.
I will draw up the circuit soon.
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#2093 Re: Something stirs in the Undergrowth

Post by pre65 »

Nice one Mark.

I've been in touch with the grim reaper, and asked for you not to be taken before you have a fully finished stereo pair that are exactly as you want them to be. :lol:
Last edited by pre65 on Fri Aug 18, 2017 3:41 pm, edited 1 time in total.
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IslandPink
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#2094 Re: Something stirs in the Undergrowth

Post by IslandPink »

Thanks - much appreciated.
However two things are likely to happen first -
1. All the drivers I've chosen will become obsolete
2. My hearing will start to go
Looking on the bright side ! :D
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#2095 Re: Something stirs in the Undergrowth

Post by IslandPink »

Horn thoughts still going on in that pat of the brain set aside for this.
Back loaded horns if done really well ( I'm thinking of Ron Clarke in this context ) are attractive on paper for all sorts of reasons ( light responsive driver ; equalisation without phase errors, in bass to lower mids, from rear horn ; reduction of driver excursion improving mid/HF performance of driver ) . The trade-off is the delay between front & back outputs. I have seen one experienced poster ( 'Serenechaos' ) build the Austin A166 horn and find the delay too much, after extended listening. Also James told me he could hear the delay on the Jericho horn.
Worth checking the numbers :
A166 : 3.65 or 3.7m from rear of driver via horn to 'splitter' at back then forward to front baffle again. This is something like 11mS .
Dallas II : about 2.6m, so about 7.5mS
Fostex 208 'factory' plan : ~ 2.55m - ie.7.4mS
Jericho - haven't yet measured but must be in the 2.5m range given size and no. of folds - so 7.5mS again
Vox Olympian : 2 waves at 500Hz = 4mS - so that delay is relevant from midrange down to frequencies around 80Hz. However ... the bass horns for 70Hz downwards are pretty big and there might be 3.5m or more of path in those, which would put the low bass more than 10mS adrift.

No easy answer on this stuff - as usual with horns.
Hope to go and have a listen to some FE208Ez horns next weekend & try to check this aspect amongst other things.
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#2096 Re: Something stirs in the Undergrowth

Post by Ali Tait »

IslandPink wrote: Fri Aug 18, 2017 12:36 pm I remember paying over £400 for the pair about 8 years ago, so that's probably as good as you can get. I had a look for other units, the G2Si is the next best, couldn't find anything from Fountek that was quite right. Next level up would be the RAAL ones :D
Have you heard the RAAL Mark?
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#2097 Re: Something stirs in the Undergrowth

Post by IslandPink »

No, but they're highly recommended by Lynn, Gary Dahl and Romy - who uses a custom ( 'teardrop' ) one costing thousands ( and ~108db/w ) .
There are only two on their website , note - some good technical blurb too. However I think there's a more efficient one called the 'Lazy' which Gary uses. Not sure of the cost. I think the bigger one on the website ( 95 or 96db ) is kinda-affordable , some searching may return prices.

Ok some more work today, now I've installed the 2x2 array of 103/105 drivers on the baffle instead of the FX120's .
Upped the capacitor in the series crossover to 165uF. Some adjustment of that likely, but not far off .
Array2_3way.JPG
Well, first impressions -
These are at least 1dB more efficient than the pair of FX120's, so I will have to reduce the series resistor to the 285GMF.
Female vocals ( and perhaps male vocals - but needs bass upping ) sound a little bit better than the FX120's :D

So it may be that the equation 2 ( FX103e) + 2 ( FF105WK ) = AER
is more valid than the equation 2 ( FX120 ) = AER .
Good news, if so ... both on cost and availability .
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Ali Tait
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#2098 Re: Something stirs in the Undergrowth

Post by Ali Tait »

Cheers Mark, will look for more info.
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#2099 Re: Something stirs in the Undergrowth

Post by IslandPink »

Some good discussions by PM with Scott on the subject of group delay ( GD ) , driver Q , back-loaded horn front/rear blending.

BLH front/rear blending is a very interesting subject. What I'm mulling over at the moment, is that there are really two sorts of GD we're dealing with here. One is the GD across a continuous output that is typical in mid-bass enclosures with one driver going from bass to mids - and we know there are differences in performance there between ported, sealed and OB - which are tolerated to greater or lesser extent by different people. However, the situation in a BLH is that there can be two separate pass bands, one from the front, one via the horn, each of which is well-corrected for GD ; but there's a 'step' between the two. This also applies to front-horn combos like the Vox Olympian.
For example in the Dallas with FE208Ez, the horn-loaded output is very flat in phase from 400Hz down to 60Hz . Then the front output from the low-Q FE208Ez is also very flat in phase because it's on its upslope , operating more or less in the 'velocity-controlled' region before the mass comes in.

The we join these two with a 7.5mS delay on the low-frequency bit !
Each 'output' rolls off either side but we can't keep them from interacting over about an octave each way.

So without listening I don't know what is or isn't acceptable to my ears. The advantage of the flat phase is each of these individual bands is that the tone and dynamics will be maximised over each frequency range. However in the middle the phase fronts can only line up at selected small frequency ranges. Also the delay in the middle will ensure that things like kick-drum and low bass guitar notes are 7.5mS behind the snare-drums ....

What I will say is that from my experiments with the folded horn, the effect of a flat phase response over even ~90 to 500Hz is a sound that is not matched in terms of dynamics or tone by any OB solution I've heard, including what I'm now listening to.
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#2100 Re: Something stirs in the Undergrowth

Post by IslandPink »

:D
Empty leather chairs... but Ron pops in with a comment below - nice .


Who knows exactly what Youtube can tell us with undemanding music, but things sound quite tight in the mids & upper bass !
There's another clip with Jan Gaberek - elsewhere. Also vaguely useful.
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