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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#1 Something stirs in the Undergrowth

Post by IslandPink »

A new project is in the early stages ....

T90A
GPA 288-H , AH-425
285 GMF ... or maybe something else

45SE
GC or F2

Can you guess what it is yet ?


ILPS
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IslandPink
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#2

Post by IslandPink »

OK , the show is on the road .
Horns are close to being ready, from Martin Seddon at Azura .
425Hz Le Cleach Tractrix

Just last night bit the bullet and ordered two GPA ( Altec ) 288-8H compression drivers.

More on the overall plan tomorrow .

Might need some help on the bass options

MJ
"Once you find out ... the Circumstances ; then you can go out"
Lee S
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#3

Post by Lee S »

Awesome Mark.

I have heard the Azuras with AERs and Klipsch bass-bins all working from active crossovers belonging to a friend in Hong Kong... It was the most "real" sound I have ever heard. I would LOVE to have a listen to your set up when it's done if that's not too cheeky?

Good luck and I will be followin your progress with MUCH interest. Personally, I think front horn is the way forward with speakers... Everything else pales....

Cheers,
©2020 Lee
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IslandPink
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#4

Post by IslandPink »

Thanks for the encouragement .
Just give me about three years :D
Briefly, I intend to get together a mid and upper section ( driven from eg. 2A3 SE ) consisting of the 288-H ( autoformered down a bit ) with one of the Aurum Cantus efficient ribbons , so getting about 100-102dB overall on that . Bass I'll drive separately, maybe from Pass labs F4 ( need to build ! ) . I've now got an option to buy a pair of Supravox 285GMF which I have loaned - they will be the basis of something . Might have to be bass-reflex ( a BIG box ) although OB might just do it .

I'm following the 'Beyond the Ariel' thread on DIY Audio, but not going 100% down that route .

Mark
"Once you find out ... the Circumstances ; then you can go out"
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IslandPink
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#5 Plan

Post by IslandPink »

Summary of current ideas :

Supravox in large BR ( onken? probably otherwise )
driven by Pass F4 class A ss
cross 2nd order ~700Hz

Horn ( Azura AH-425 ) driven by GPA 288-8H alnico
crossing in 2nd order 700-ish
Autoformer ( Slagle ) adjusted down to match ..
Aurum Cantus G3 ribbon, crossing in ( 2nd order ) around 6-7kHz
So about 100 to 102dB/w

The mids and HF driven by 2A3 or 6C4C SE .

Thinking the F4 can be driven off SE amp, pick-off from after driver stage , since it has no gain .
Low pass for Bass will be at speaker .
700Hz High pass for horn & ribbon probably in amp if possible . Cross between horn and ribbon at the speaker .

MJ
"Once you find out ... the Circumstances ; then you can go out"
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Ali Tait
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#6

Post by Ali Tait »

So you'll be bringing all that to the next Owston then? :D
Lee S
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#7

Post by Lee S »

Hi Mark.

Why not try front loaded for the bass too? Maybe a La Scala enclosure or something similar. Probably not neccessary but they do say FLH bass is some of the best... Who am I to argue? That's what I am going to build anyway (eventually when I have time and room). FLH bass and then Azura coming in at about 200Hz or so and all the way up to the top with a single Lowther or AER. One day...... Hee hee.

Sounding good so far though.

Cheers,
©2020 Lee
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IslandPink
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#8

Post by IslandPink »

Hi Lee
You know, I did look at the Klipsch, and things like Christian Rintelen's Blue Thunder hybrid front/rear-loaded 15" unit in SP, but there are some problems. Anything with pure horn-loaded bass has to be HUGE to get down much below 100Hz. On those hybrid schemes like the blue Thunder or the Altec stuff it's based on, I have absolutely NO idea how they are desgned ( SP didn't help ) so I think I'd be getting in too deep .
I think the bass may go through more than one iteration , so I'm starting simple .

Mark

Ps. Ali - Owston 2014 perhaps !
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andrew Ivimey
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#9

Post by andrew Ivimey »

Steve threatened a few more months till the next Owston - we are impatient Mark, and all those horns!

Where did you pick up Aurum Cantus ribbons? They were much favoured by Mark Levinson many moons ago!

Looks a mess, sounds great!!!! - a motto, perhaps
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IslandPink
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#10

Post by IslandPink »

Andrew
I haven't bought the ribbons yet ! I'll have to wait until I can sell the old car ! I'd be interest to find out where to buy them cheapest .

Currently I have horns awaiting delivery from Australia and two compression drivers awaiting final parts to be finished and sent from Oklahoma ...oh and I have a pair of Supravox 285GMF's currently in OB at home .

MJ
"Once you find out ... the Circumstances ; then you can go out"
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#11

Post by IslandPink »

Bass options being considered but the Onken/Jensen keeps looking pretty good :

http://www.supravox.fr/kits/jensen.pdf

Given that each speaker will need 1 full sheet of 25mm birch ply, I'm not sure I'd ever be able to get them in the car & up to Owston ! Just getting them built and positioned in the front room may be close to the limits my back will impose !

Mark
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#12

Post by Dave the bass »

Ooofff :shock: A 4 x 8 sheet of 25mm Ply EACH :lol: Flippin' sod that! It'd be like gigging again!

DTB
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#13

Post by simon »

Mmmm, yeah. My 208 horns have 2 18mm thick 8x4 sheets of birch ply per speaker. Very rigid and very heavy. And very bad for backs. And knees. And arms.
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IslandPink
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#14 Horns/Ply

Post by IslandPink »

Ok, I ordered two sheets of 25mm Birch ply to collect next week . Only 200 quid !
and
The horns are flying through the air hoping to land some time early next week .
Will post a pic from Martin of some horns in next day or two .

An unwelcome feeling of responsibility grows .... :!:

MJ
"Once you find out ... the Circumstances ; then you can go out"
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#15 Re: Horns/Ply

Post by pre65 »

IslandPink wrote:Ok, I ordered two sheets of 25mm Birch ply to collect next week . Only 200 quid !

MJ
Did you haggle ? Last sheet of BB ply that I purchased was quite a bit cheaper by asking for discount ! (not B & Q)
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