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In Reply to: RE:More T350 lore posted by Paul Eizik on October 07, 2014 at 15:50:25
I guess I'm going to leave the stock horns on the T-350's. But I am going to change out the stock horn on the 1823M. Most likely a conical tractrix design. I too have been thinking of raising the OX to 4000 or 4500 Hz. What are your thoughts on a mid-bass horn design? Straight conical, tractrix, exponential? I have the room and 100% WAF.
Follow Ups:
ACMINC,
Your first instinct is correct. Getting rid of the fifty year old PA horn, and dropping in something better. It's the best first step for vintage horns.
Building horns and going four-way active is very ambitious, but while you are learning horn theory, and the art of horn construction, let me make a suggestion that you just go ahead and buy a decent pair of horns to listen to while you master all that.
Why do you want conical horns? Ultimate sound quality? Do you prefer a definate sweet spot all the time, or do you want to fill the house with music?
I posted a link below. It's not what you want, but it's just to show you what's out there. $550 and a week, and you could really do a lot for the sound quality of your speakers. Also, you could never build these, so when you build, it will be something different than this. If you want to talk about this horn, or other possibilities that's cool.
Learn what the difference is between hyperbolic, exponential, and conical, and what theoretical cutoff is, and you will be a long way to understanding audio horns. It will help you decide what you want, and what you are able to do, and the trade-offs, always with the trade-offs.
Jamie
Big speakers and little amps blew my mind!
Conical horns and tractrix horns are two different animals, though hybrids incorporating features of each are possible. I prefer tractrix horns on compression drivers for the midrange, but I've heard some good conical mid horns. The selection of a different high crossover point with the 1823M should be based on data from measurements. The 1823M does not have a phase plug and subsequently just can't go all that high compared to mids with phase plugs. Raising the crossover much beyond the 3500 Hz point spec'd by EV will tend to result in a hole in the response between the 1823M and T350. In the meantime you've got some work ahead prototyping some conical mid horns. You can quickly fabricate a functional conical mid horn with poster board and duct tape which will show you if you are on the right track. BTW the 8HD is a diffraction horn and will have a broader horizontal coverage pattern if the long dimension of the horn is vertical, though this may seem counter intuitive. Ditto for the T350. You should set them up this way for comparison to anything you may build.
Paul
hi Paul. The 1823M does have a phase plug.
You can see it when you open it up.
Quirck
The EV data sheets for the 1823 and 1824M make no mention of a phase plug or loading plug. Neither do the data sheets for the similar 1824S. A loading plug is promoted in detail as an important feature in the data sheets for the T350/T35 however. One could argue that the volume and geometry of the air chamber in front of the diaphragm in a driver like the 1823/1824 is designed to minimize destructive cancellation in the sound waves, and that this is the same task a loading plug would be put to. However they are quite different things. To be honest I have'nt currently disassembled any of my 1823's or 1824M's to examine this area, but a picture of something resembling a phase/loading plug in one of these drivers would make me a believer.
Paul
Hi, I have sent you two pictures, cannot post them here.
Quirck
Thanks for the correction and the pix! There was probably a patent concern for the reason that this was not mentioned in any of the data sheets. I have never replaced a diaphragm on any of my 1823/1824's but I did open an 1823 up some years ago, and if you don't remove the diaphragm then you won't see the plug. Also there's a metal screen obscuring a view of the plug from the mouth of the driver. BTW the pix came through fine (I've attached one here) but the two text attachments were blank, maybe because I'm running a Mac.
Paul
I made a conical horn to replace the B&C ME20 horn and the improvement was well worth while. I think conical is the way to go for hifi use. It doesn't have any 'horn' sound and provides a flat response up to 45 degrees off axis. Make sure you radius the baffle and transition nicely on the horn exit. I would avoid a round conical horn in open space as this focuses too much boost at one frequency due to edge diffraction. Mounted to a square baffle will give you a smoother frequency response. Also, pay special attention to the compression driver itself, noticing the geometry coming out the unit and making sure your horn matches with no abrupt changes in horn profile. Using digital EQ you can compensate for any loss in output near the cutoff.
Obviously, you have not studied the characteristics of conical and exponential horns.
Conical horns suck.
Here are my findings. Please post your horn builds with measurements.
http://croweaudio.blogspot.ca/2013/05/oblate-speherical-waveguide-diy-project.html
http://croweaudio.blogspot.ca/2014/06/oblate-spheroidal-horn-completed.html
http://croweaudio.blogspot.ca/2014/07/frequency-response-measurements-for.html
I don't build horns. I leave that to the pros.
All you have to do is to look at the data to know that conical horns aren't hi-fi.
Look up earl Geddes OS horns and reviews. Stop being so obstinate and insulting.
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