compression driver throats |
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
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Posted: 26 March 2013 at 7:19pm |
compiled above with another list including celestion. and beyma cd1014fe that I just measured
Beyma
CP750Nd – 24º CP850Nd – 7º CP755Nd – 12º60’ SMC65Nd – 15º CP385Nd – 16º30’ cd10 - 16º30’ CD1014Fe - 17 SMC225Nd – 13º1’ CP750Nd - 24º CP850Nd - 7º CP755Nd - 12º60' SMC65Nd - 15º CP385Nd - 16º30' SMC225Nd - 13º1' B&C 1"DE250 14.6° DE10 7.7° DE12 24° DE400TN 20.7° DE400 31° DE500 17° DE200 9.9° 2" DE85TN 34.5° DE750TN 22° DE950TN 17° BMS 4524 20º 4538 21.8º 4544 20.6º 4550 14º 4552 – 24° Celestion4554 26.7º 4555 30º 4590/4590p 1º 4591 1º 4540nd 14º 4552nd 24º 4592nd 10º 4594nd 3º 4595nd 10.8º CDX1-1745 20.16° total CDX1-1730 20.16° CDX1-1731 20.16° CDX1-1746 7.6° 18sound: NSD1095N, ND1090 = 27° NSD1480N = 10° jbl 2450 10+° radian 950 20+°/20.3 |
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Steve_B
Old Croc Joined: 29 September 2007 Status: Offline Points: 1587 |
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If you follow the link to minaximal’s thread on horn
construction, it gives a good idea of how to go about constructing a round
horn. A couple of things that I have found are that mdf makes a better plug and
don’t use hub pullers to release the horn from the mould. Due to how ply is constructed, when you turn it on the
lathe, you are cutting along the grain, then across the grain, then along the
grain…… If you are not careful you can get little ridges forming as you turn
the plug. Mdf is more consistent. I always glue and screw the layers together
and coat the wood with resin once shaped. I then finish off with increasingly
finer grades of wet and dry up to 1200 grit. Finally I use T-cut before
polishing with a release wax. Once I have made the initial horn from the turned
plug, I make a second mould from that and put the wooden plug away. Using hub pullers concentrates all the pressure on two or
three small points on the flange which can cause cracking. One way round this
is to make an extremely thick flange. I use a frame that supports practically
the whole area of the flange and then use a steel bar fractionally smaller than
the throat and tap out the mould with a hammer. I use both wax and release
agent, and rarely have problems with sticking moulds. If you go with this method,
ensure that you polish all traces of wax off the mould before applying the PVA
release agent. If you have problems with the release agent not flowing, you can
reduce the surface tension by adding a few drops of washing up liquid; this
stops it beading. There were some useful videos by hornmaster showing how the horns were made once the mould had been finished. Before you get to all of the above you need to design your horn. Call me cynical, but I would suggest that the throat angles
of compression drivers have more to do with the distance from the
diaphragm/phase plug exit and the throat exit, which has to be one of the
standard sizes. The actual diaphragm size also comes into this too. One of the advantages of designing your own stuff is that
you get to decide which areas of the design can be compromised and which cannot.
There is a lot of information about the different aspects of design out there
on the internet so I won’t go into any great detail at the moment. Exponential and tractrix horns give increasing directivity
with increasing frequency. This compensates somewhat for the fall off in power
response to maintain a level on axis frequency response. Conic horns (this
includes the OS and similar horns) have a more constant coverage but require
more compensation eq to give a flat frequency response. Abrupt changes in the flare profile (line array slots and traditional CD horns) will introduce ripples in the response, but may enable better pattern control. The size of the horn will determine how low a frequency the horn will maintain good pattern control. Depending on what you are using in the frequency band below the horn, it is sometimes better to lose some control so that the polar response of the two frequency ranges match at the crossover point. For one off projects where the horn is designed for just the one box, look at the system as a whole and try and maintain an even power response through the crossover region. If possible, build and measure the mid section below the horn to give you a good idea of how low the horn needs to go and how to match up the dispersion patterns. As you are designing the horn. you have more flexibility that way rather than designing the horn and trying to match that with a suitable cone mid driver. |
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Tony Wilkes
Old Croc Joined: 02 August 2004 Location: West Midlands Status: Offline Points: 4840 |
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It is easy to get way to anal about such things as throat angles etc. Whilst obviously the ideal would be to have the comp driver perfectly matched to the horn throat, I have heard way too many examples of duo's that on the face of it just will not work correctly together actually making a really nice noise.
Got to admit though that sound wise an OS horn perfectly matched to the comp does sound a bit special, not always the best dispersion pattern for P.A though :) Tony |
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www.forteaudio.eu - BMS - db-Mark Processors - Lexon (SAE)
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Non-Smoking Man
Registered User Joined: 14 June 2011 Location: Bracknell Status: Offline Points: 192 |
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Google Jack Bouska for a high level discussion of waveguide theory (also Earl Geddes re 'Oblate Spheroid flare shaping). And what a system he has! (Not pro audio as such but use of pro audio drivers.)
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Science over Religion
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minaximal
Old Croc Joined: 26 September 2004 Location: United Kingdom Status: Offline Points: 1780 |
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Did you mean this thread? http://forum.speakerplans.com/how-to-make-a-circular-waveguide-in-pictures_topic39526.html Steve B, has also posted threads about making circular waveguides, and theres been more technical talk on the DIY audio forum about exit angles etc. al |
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matty w
Young Croc Joined: 27 August 2008 Status: Offline Points: 798 |
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sorry de 85tn i mean
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matty w
Young Croc Joined: 27 August 2008 Status: Offline Points: 798 |
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would imagine the angle of throat is a good indication of drivers intended use.
the de950tn is an interesting 1! will look into it later when iv got more time.
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matty w
Young Croc Joined: 27 August 2008 Status: Offline Points: 798 |
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sorry for bad punctuation my phones hardwork and im tired lol
surely using an off the shelf horn is a bit like being able to buy an off the shelf bass horn and then finding the best driver for it,its just not cricket! u design the horn to the driver.
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matty w
Young Croc Joined: 27 August 2008 Status: Offline Points: 798 |
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good stuff minaximal ,some realy usefull information there mate :-D
id like to start a project building my own comp horns, my plan is to scour the web on different ways of going about building them.im sure i saw somewhere someone use lots of if u like gaskets of mdf stuck together forming the profile, does that make sense? seems to be alot going for the idea of not having to pick an off the shelve comp horn,to much of a compromise!
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minaximal
Old Croc Joined: 26 September 2004 Location: United Kingdom Status: Offline Points: 1780 |
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Hi, yes throat angles are important and often ignored.
The tannoy VQ is a type of oblate spheroid, basically a conical horn with a smooth short transition as close to the throat as possible, a very similar initial start profile to the peavey quadratic waveguide horns. for upper end off axis response there is no better than a type of oblate spheroid, the only drawback is the need to have a shelving filter to boost 6db the upper end frequencies, but at least unlike normal constant directivity horns the beamwidth doesn't narrow anything like them on an OS or strsight conical. there is no set throat flare rate and all comps vary, for single stack a wide dispersion conical or OS would be great for off axis, but will also array better due to minimal beaming. Here's my list of known exit angles: CP750Nd – 24º CP850Nd – 7º CP755Nd – 12º60’ SMC65Nd – 15º CP385Nd – 16º30’ cd10 - 16º30’ SMC225Nd – 13º1’ B&C 1" DE250 14.6° DE10 7.7° DE12 24° DE400TN 20.7° DE400 31° DE500 17° DE200 9.9° 2" DE85TN 34.5° DE750TN 22° DE950TN 17° BMS 4524 20º 4538 21.8º 4544 20.6º 4550 14º 4554 26.7º 4555 30º 4590/4590p 1º 4591 1º 4540nd 14º 4552nd 24º 4592nd 10º 4594nd 3º 4595nd 10.8º cheers al |
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matty w
Young Croc Joined: 27 August 2008 Status: Offline Points: 798 |
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perhaps i should start a new thread in the general section lol
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matty w
Young Croc Joined: 27 August 2008 Status: Offline Points: 798 |
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just to add for clarification,the tannoy vq speaker that uses the bms coaxial,that horn is that a tactrix?
i gotta get it clear in my head tactrix= kinda conical but with an ever increasing flare rate?
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