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excursion in 1850

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roborg View Drop Down
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    Posted: 11 July 2005 at 11:46am

Wondering what the real-world cone excursion gets to in 1850s near & below resonance...  Just had a listen to my club system after left it alone with a friendand guest DJ at about 3am.  They managed to beat the hell out of the coils in all the 1850s with a stupidly low cut-off (they were pumping >1K per cab with low-cut of 30hz  after i told the tw**s to leave everything after the mixing desk alone... (id set it to 50hz 24db.)  Building a lockable rack now.....  Was my fault as they didnt know how finnicky the horns are 

   The frightening thing was the cabs were still producing good bass output (+ funky steel mill sound) even though all the coils were partially unwound & fractured, one of the speakers had pulled off a cool stunt & lowered its DC resistance from 5.3 to 2ohms!  No wonder one of the amps had blown a fuse (was still delivering power tho, as it was in bridge mode and only one channel died )  My guess is they were beating out the back-plates all morning & no one noticed.  prolly trying to re-create that bass-reflex sound

  NE way damage is done & the re-cone kits cost R$105 (<20quid each  direct from the manufacturer so not gonna break the bank.  Will break my back putting the speakers back in the cabs tho

  Id be interested in hearing about what conditions the speakers in other 1850s had failed.  Im gonna uprate the amps soonish to 8Kw for 4 cabs, so was thinking of a 60-70hz low-cut & then let the infra-horn do everything down to 20.  Cabs finally got a soaking, courtesy of a pitcher of vodka & flyinghorse....

 

cheers,

  Rob

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Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Contour Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2005 at 12:09pm

You should get that infra horn working. I think it will be amazing with the right drivers.

Bes regards,

Walt

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rastaman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastaman Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2005 at 3:23pm
So your putting a low cutoff on the infra horn at 20Hz?

Did you ever decide whether it was a dual resonance Holliman design or just a simple single port (albeit folded horn style) cabinet? I keep thinking when I get round to building a new system, I'd like to start with something like that, depending how high they can go, maybe I could get away with HD15's for the next step up.

More info needs to be on your website soon
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Post Options Post Options   Thanks (0) Thanks(0)   Quote roborg Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2005 at 4:20pm
@contour:  i'm really undecided about drivers for the infra horn, the throat is waiting for something good, i'm feeling a couple (or maybe even 4) ciare 12.00's would be pretty good with 4K+ going into them, all depends on how much i can get them for out here.  The oversound sub800's are good when treated well (even if i have managed to destroy a few ) & v cheap, two 18's will be around 2.5:1 compression.
 
@rastaman:  The infrahorn for the club was designed as a true horn, but the holliman cabs are just plain nuts, they do go as low as the amp can go!  I think the patent is just one way of looking at them, i think the important part of the design is the velocity coupling & the very low tuning of the main port.  I reckon the velocity coupling acheives some intermediate impedance matching between the very low freqency helmholtz resonator & the speaker cone (the comp ratio is enormous >8:1)  I think the only true way to model the speaker is with a numerical sim & then try to make sense of what it turns up.  At the moment i have two of the 18" holliman cabs on the website at home with 12"ers bolted to the back.  They do rock da house pretty hard from a 300w amp.  Not experiencing any uncontrolled sensations yet, but then i am only playing music thru them!  In fact the open back produces quite an extended frequency range , kinda like a messed up scoop   I've had to jam some foam rubber in all the windows to stop them rattling, doors rattle alot too, in fact any enjoyment is masked by the continuous rattles, need a proper listening room.....
 
cheers
  Rob
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rastaman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastaman Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2005 at 4:47pm
Oh sorry, you were referring to the giant bricks and mortar W-Bin I guess 

So have you chocked up the slot some more to accomodate the 12"ers on the Holliman I'm guessing, are you still using just the thickness of the wood (15mm ply) or did you add some kind of super thin, super strong layer as suggested in the holliman.doc thats flying around the internet to up the velocity coupling.

Guess I should shut up, give you time to get your bills payed and take some more pictures of the Hollimans. The way I looked at your design the slot and lip provided a very small X in comparison to the X' provided by the horn/port part of the design, thinking of V as the volume of the air trapped inside the fold of the horn/port and the horn/port itself as X' meaning you had a low starting resonant frequency of V:X and then a fairly wide band of V:X+X' but I hadn't sat down and scribbled out the numbers as yet.

Your saying though you think it's all in the velocity coupling, does that make the major factor motor strength within the excursion of whatever driver used? I've got to stop relating drivers to engines, I'm thinking of this as a diesel engine, where the components have to be a little stronger to cope with the higher compression.

FYI there is a US dealer for the CIARE, I don't know if it's cheaper getting things shipped US > Brazil, than Europe > Brazil. I can look 'em up again if you like, I think I found 'em after a bit of googling.

PS I'd plan to use the Hollimans in windowless basements, there's a place downtown puts on shows and clubs in the basement of a store, seemed like an ideal place to pump up the room pressure to me


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roborg View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote roborg Quote  Post ReplyReply Direct Link To This Post Posted: 19 July 2005 at 2:26pm
yeah the slots are a bit more choked up!  But not so much so, they are about 1x10" so around 8:1 compression ratio for the 12's  The plate they drive through is still the old 15mm ply.  The actual slot itself is fairly deep (AFAICR the patent suggests a thinner plate would enhance velocity coupling only by reducing wall friction inside the slot itself, so i didnt try to make anything overly thin (ply is cheaper & easier to work with than alloy!)
  I agree that prolly the best sort of driver is one with a stronger motor, a good xmax has got to help too, as that'll prolly let you go for a lower compression (help prevent cone failure too)
  The x x' resonances in the design were (digs out excel file....) designed at around 25hz & around 100hz (very roughly.)
  My biggest worry with importing a brand is re-coning.  The ciare drivers look perfect, but if they require a recone (as is very likely!) i';d have to wait ages for shipping.  Locally manufactured brands can deliver in a day or two, so a bit too much fun on saturday night can be fixed for wednesday , bit like a good hangover....
 
cheers,
  Rob
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