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maximum power for sn12-b & beyma cp750ti |
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roborg 
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Joined: 05 July 2004 Location: United Kingdom Status: Offline Points: 1026 |
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 Topic: maximum power for sn12-b & beyma cp750tiPosted: 01 February 2008 at 5:47pm |
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Almost finished a new mid-range. It's loaded with two sn12-b's & a beyma cp750ti on an p-audio 4230 horn. The horn dimensions are fairly similar to the porn-horn but with slightly greater dispersion, more or less 90degress -6db (at 1khz the mid-horn will matchup to the 2" driver horn, so a fairly acceptable design compromise. One of my mates (who will use the box) loved the square spikey-phase plugs i made in some mt102 clones, so i made some uber-spikes in this one!
What are peoples thoughts on the maximum i can drive these drivers with? The sn12-b is used in the porn-horn & i think the voicecoil & magnet assembly in the 750 is the same as the 755 neo used in the porn too.
Heres some pix, as the glue dries!
cheers,
Rob.
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What I cannot create, I do not understand
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Heathrow_B_line
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Joined: 11 January 2006 Location: United Kingdom Status: Offline Points: 7339 |
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Posted: 01 February 2008 at 5:52pm |
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wow
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Produce a killer sound. Take no prisoners.
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roborg
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Posted: 01 February 2008 at 5:54pm |
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i was gonna add, i have a bellringer ep2500 handy for the job, so i figured one channel at 4 ohms for the two sn12b's and the other channel @8ohms for the cp750ti
So the sn12bs would get 375w a piece (kinda underrated i reckon) and the driver 500w (probably about right once the LMS is set up) Other choice is bridging the amp & winding back to deliver 600w per sn12b & using another amp for the driver (maybe a decent reference amp too...)
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What I cannot create, I do not understand
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Mark James
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Joined: 15 January 2006 Location: rig side Status: Offline Points: 5306 |
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Posted: 01 February 2008 at 5:59pm |
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i get the distinct impression that complex wood work just doesnt scare you at all!
im liking the phase spikes,! my guess for power would be 375<450w for each sn12b [to allow you to run them at rms power and have headroom] but not having used them its a rough guess based on what others have said, but wow those look realy mad!!! |
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insert silly sentence here
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TONY.A.S.S.
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Joined: 21 February 2007 Location: United Kingdom Status: Offline Points: 6867 |
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Posted: 04 February 2008 at 9:58am |
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Are you leaving the flat surfaces to face the speaker or are you going to even up the loading by attaching something to match the shape of the cone.
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Disco Stu
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Joined: 03 March 2005 Location: United Kingdom Status: Offline Points: 2492 |
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Posted: 04 February 2008 at 10:36am |
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I was thinking the same as tony. I dont claim to know much about phase plugs but I believe the whole point is to stop one side of the cone seeing the other and it doesnt look like your cones do this.
Stu Edited by Disco Stu - 04 February 2008 at 10:38am |
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All you need to know is:
Sensitivity + Power Handling - Power Compression = Max Output My acts: www.myspace.com/thebowiexperience www.myspace.com/scheisseelektronisches |
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mykey
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Joined: 18 August 2005 Location: UK/Indonesia Status: Offline Points: 9680 |
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Posted: 04 February 2008 at 1:07pm |
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Nice woodwork
one question though
round throat square bung?
 is this just for showits going to be very complicated getting the sound from the cone to evenly exit the throat?
would be interested to see what you have in mind for the rear of the bung?
is it a pyramid type design with the point missing and instead a concave center?
wont be spot on but let us know how you get on
never seen that before, comments anyone?
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tweeter box
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Joined: 21 October 2007 Location: United Kingdom Status: Offline Points: 6784 |
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Posted: 04 February 2008 at 2:39pm |
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They look wicked!
Im feelin them phase plugs!
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TONY.A.S.S.
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Joined: 21 February 2007 Location: United Kingdom Status: Offline Points: 6867 |
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Posted: 05 February 2008 at 12:09am |
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I think it deserves to have a square speaker cone
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mykey
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Posted: 05 February 2008 at 6:29am |
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if the boke sounds ok I'm sure that will
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roborg
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Posted: 05 February 2008 at 11:09pm |
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@mykey, its not so complex! just needs alot of screws to hold it together whilst it all sets, although at times i was cursing a bit ;) The squareness (and length of the plugs) & distinct angular design is mainly for show, the exponential is actually pretty exponential rather than tractix or a (better) cd design with a better designed throat (needs experimentation or direct rip-off.) The design is basically to look fairly interesting & also be pretty efficient with about 90degrees dispersion. Its only about 2:1 comp ratio (i think its 1.9ish) so not super efficient & of course the phase plug isnt a phase plug at all, its just to bung up the front of the speaker.
@tony, yeah i'm filling the back with some plywood slices to roughly match the cone profile, but going to leave about 1cm between the cone & the back of plug. Yeah some square car subs would fit nicely ;)
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What I cannot create, I do not understand
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roborg
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Posted: 06 February 2008 at 1:01pm |
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here are the two chucks of plywood im going to use for this cab. Shown here with glue setting. I wanged round the edge with a 45deg bit in the router b4 i give it a finish off in my 'woodwork lathe' (an elecric drill in a vice...) The end of the 'plug' will be cored out slightly for the dust-cap to give >1cm clearance for the whole cone.
I would have made a mould but, as i'm only making 4 plugs, it was faster, cheaper & less messy to make them out of plywood.
With a lowish compression ratio i've never found (by a listening comparison to 1.5khz of two horns, one with a plug fitting to 3mm & the other to ~1.5cm) any discerenable difference once the horn was integrated with a comp-driver & bassbin. I suppose that's because the low pass formed by the compressibility of the volume 'behind' the throat isn't sufficiently low enough to affect much output below x-over.
on the subject of moulds, here's the first plastercast i ever made of a speaker using cling-film.
You can see its possible to produce a really nice finish (this 1 is very rough tho.) The places where the film wrapped over & made the wrinkles can be eliminated by having a good depth of plaster (to increase the pressure on the film & press it into the cone surface, u need to ensure the cone isn't pushed into the speaker if you want the mould to fit to the edge of speaker suspension) Any cling film left sticking into the plaster i burnt off with a heat-gun hehe. Damn good fun making moulds & plugs, but v messy.
cheers,
Rob. Edited by roborg - 06 February 2008 at 6:48pm |
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What I cannot create, I do not understand
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