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WE11 long throat ideas

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Posted on February 1, 2017 at 22:45:35
pix
Audiophile

Posts: 366
Location: sweden
Joined: March 18, 2006

What curvature formulas does those vintage long throat horns use?
Is it just an extension of the regular tractrix?

I am thinking of making an extension of my 2" throat horns down to 1,4" reaching to the bottom of the driver-exit just to eliminate that driver exit angle error (10 degrees meeting 4 degrees). By extending the current throat curvature (approx. 4 degees) the extension would be 107 mm long. But would it be a good idea to make it longer?

The horns are 200Hz tt-horns with Radian 750Pb drivers used down to 350Hz 1st order filter.

 

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RE: WE11 long throat ideas, posted on February 2, 2017 at 05:30:31
Mr_Steady
Audiophile

Posts: 945
Location: North Florida
Joined: August 19, 2014
Long throats are hyperbolic.

You can use them if you don't mind high distortion in the midrange, which is not the reason we fool around with horns.

I will try to write a more in depth response tonight.

To get you started you should read this article. There is a second part to it also. Search for it.


------------------------------------------------------------
Big speakers and little amps blew my mind!

 

Exit angle mismatch, posted on February 2, 2017 at 16:11:54
Mr_Steady
Audiophile

Posts: 945
Location: North Florida
Joined: August 19, 2014
So you are saying you are using a 1.4" driver on a horn that has a 2" throat? Build the extension, or get a 2" driver. Honestly I would recommend the 2" driver. Lots of reasons if you have the time.

Please remember what Kloss told you about the WE snail horns. The were designed to utilize the capabilities of the 555 driver, which is a very wideband driver that goes really low, 120Hz or something. Unfortunately acoustic horns are not wide range transformers. The snail horns are beautiful, but an anachronism. Build one to look at if you want.

Your filter is -3db at 350Hz? You driver is operating a lot lower than that.

Hope this helps,

Edit: I also meant to say that all horns are a ratio of loading to distortion. Slow expansions like the long hyperbolic load the best at the bottom, but have high distortion. Fast expansions like the conical do not load well, but have low distortion. If you take what physics gives you then you might use a hyperbolic horn for bass, especially since distortion is hard to hear in bass, and you might use a conical for a tweeter, because you don't care about low end loading, but you do care about the low distortion. Which brings us to finding the right compromise with the midrange horn where you want both. The tractrix fits the category, but I prefer the Spherical (Kugelwellen) profile.


-------------------------------------------------------------------
Big speakers and little amps blew my mind!

 

RE: WE11 long throat ideas, posted on February 2, 2017 at 16:30:46
Coner
Audiophile

Posts: 1865
Location: S.W. Washington state, USA
Joined: November 17, 2001
What are those drivers in pic?. You could find some
JBL 2482's and and add a tweeter. 2482's will go low enough.

 

RE: More information needed, posted on February 2, 2017 at 19:02:36
Paul Eizik
Audiophile

Posts: 1914
Joined: September 15, 2001
Pix

What is the length of the horns in the picture, and the mouth diameter or radius? Is the Radian 750Pb a 2 inch driver? Some of the other posters also seemed confused about this too, and a web search did not provide any info from the Radian catalog that came up. Are you attempting to couple a 2 inch horn mouth to an existing 2 inch driver? Or are you attempting to couple a 2 inch horn mouth to a 2 inch driver with a smaller horn mouth adapter? There have been adaptors like this available to couple a smaller compression driver to a 2 inch horn mouth (I have some JBL examples) but it's to hard to generalize about whether this would be an improvement, it all depends on the driver and the horns in question. Do you have a way to measure this experiment? You can download Room Eq Wizard for free (REW for both PC and Mac) and with this and a decent test microphone you can evaluate the results.

Paul

 

Radian 750Pb, posted on February 2, 2017 at 22:48:27
pix
Audiophile

Posts: 366
Location: sweden
Joined: March 18, 2006
These are Radian 750Pb drivers, which I assume is an older 850Pb
2" throat, 3" vc and 10 degree exit

 

Well, the reason for the extension idea is twofold, posted on February 3, 2017 at 00:40:25
pix
Audiophile

Posts: 366
Location: sweden
Joined: March 18, 2006

Thanks for your answer, I Think I have a better understanding now.

Actually, I hade two things on my mind.
1. The eliminiation of the cavity-error caused by an 10 degree 2" driver exit meeting and a 4 degree 2" horn throat.
2. Since I am doing an extension of the horn to solve the first problem, Is there reason to extend the horn even further?


No, The Radian 750Pb is a 2" exit driver and the horn has a 2" throat.
But the driver exit-angle is 10.4 degrees and the horn-throat-ending is about 4 degrees. This make a smal (but not negligable) cavity inside the driver exit (an anomaly in the horn curvature).

By removing the dust protection cloth at the driver, I could extend the horn going into the driver, all the way down to the air-vents, which in my case is approx. 1,4" in diameter. This means that the problem with driver-exit-angle and horn-throat angle will dissapear.

Since, the preasure alteration in the horn throat is high, this extension must be mechanically firm and sturdy. Still it needs to be quite thin walled to go inside the driver exit bottom. The last inch lip will be coneshaped with a 10,4 degree outside angle, and a 3-4 degree inside angle. I have made some sloppy experiments using carbon fibre/epoxi for a bent extension, which would meet this requirements (se pix).

By making a 107mm extension of the 200Hz Tractrix horn curvature, the diameter goes from 2" to 1,4" (everything else the same). The horn is still a 200Hz cut off horn and the frequency bandweidth is unchanged.


Now, to clear my question (which I Think you have partly answerd).
Whould it of any benefit to make this extension even longer (than 107mm), going to a even flatter curvature than the 4 degree exit discussed above. Or is the tractrix curvature opitimized as it is?

Note, the pix showes one of my experiment with a bent extension pice which is 2" in one end, and 1,4" in the other. In this case, the length is extended from 107mm to 200mm (so it´s curvature does not follow the tractrix curvature by the book). But as I said, this was more of an experimnent using carbon fibre, than evaluating sonic gains.

By making the extension piece bent the extension could be extended arbitrarily ceeping the WAF-factor low ;o)

Finally, I am not sure if I should make this straight or bent when it came to the real extension. I just wanted to show this piece as an alternative.

Finally, I understand that the WE555 is a unique driver. And that I will never come close to its properites with modern PA-drivers. Still the questions must be asked if there is something to learn from those days in modern designs.


 

Sure information supplied, posted on February 3, 2017 at 01:00:16
pix
Audiophile

Posts: 366
Location: sweden
Joined: March 18, 2006
Hi Paul
I have written some clearifications in Mr steadys post.
My first goal was to eliminate the exit angle missmatch between a 10.4 degree driver exit to a 4 degree horn throat (both 2" in diameter)

I figure I could do this by extending the horn curvature 107 mm in length, and letting the horn pass the driver exit, going inside the driver.

Secondly I figure, why sattle with an 107 mm extension?
Would it be of any gain indreasing this to (lets say 200-300mm) in terms of distorsion of cutoff?


Data:
The horns are 200 Hz cutoff tractrix (approx 600 i length and diamter). The horn throat are 2"

The Radian 750Pb is a 2" exit driver with 10.4 degree exit angle (about 1" Deep). It has a 3" voice coil

I am currently using a single serial cap making a very shallow x-over point at 350Hz. This was chosen by hearing rather than measuring. I have tryed several passive and active x-over configurations, but also digital (MiniDSP) -variants. But simple filters sounds best in my ears.

 

RE: Sure information supplied, posted on February 3, 2017 at 11:49:25
Paul Eizik
Audiophile

Posts: 1914
Joined: September 15, 2001
Pix

A horn is most efficient when the horn length is equal to 1/2 of the wavelength at the lowest target frequency. If the horns pictured here are 600 mm (23 5/8") in length they would fall short of being 200 Hz midrange horns:

13,500/200=67.5/2=33.75", which would be the ideal length for a midrange horn with a low frequency target of 200 Hz.

As a 350 Hz horn it should work as the half wave dimension for 350 Hz is 19.28" which is quite close to the 600mm (23 5/8") length.

Making the horn throat smaller than the 2" driver exit (if I understand your intension) would have the effect of making the volume of the air chamber in front of the driver diaphragm larger, which would have the effect of rolling off some of the high frequencies at some point, and this may be constructive or it may not. This is to say it could be useful rolling off a high frequency peak in the response, or it could just put a dip in the response which may not be useful.

A frequency response test graph would reveal if there is a peak in the response of this horn and driver combination that techniques like this could be used to tune out, but it's difficult to generalize if something like you are proposing would be an improvement or not. Tuning something like this "by ear"can be problematic as you can wind up with something that sounds good with one particular favorite recording, but worse with other types of music, and I've been there and done that.

So this all comes down to Cowboy Engineering: try it and see what happens.

BTW I would avoid a curved adaptor in a midrange horn, as this would assume that the wave front can maintain the same speed between the longer outside radius and shorter inside radius. Also a first order crossover is a good match for a horn where the bass end typically will roll off naturally at a quite steep angle.

I hope all this helps

Paul

 

RE: Well, the reason for the extension idea is twofold, posted on February 4, 2017 at 11:00:59
Mr_Steady
Audiophile

Posts: 945
Location: North Florida
Joined: August 19, 2014
It sounds like you've been reading Geddes. It's been awhile since I've read his book, and his posts on diyAudio, but IIRC Geddes was concerned about matching the exit angle of the driver and his OSWG, but this had significate importance to him because of the characteristics and the theory of the OSWG itself. It didn't seem to be as critical to him on other profiles, although he would certainly recommend it even for the tractrix profile. For him it was critical for the OSWG.

I remember a thread where he and I guy I think who was in Sweden conversed about how the man had made his own OSWG, and had taken a metal band saw to his driver and cut off everything in front of the phase plug, which you called air vents. It's what you are talking about doing. Geddes approved of this very much, but once again this is critical to him because this was an OSWG. I would point out that the throat of driver, that is from the phase plug to exit (mouth) of the driver is a horn, so in effect the dust cover is the horn extension from 1.4" to 2" if you follow me. Yes it's probably a different expansion rate that the tractrix flare, but no biggie. What you really want is horn that has a throat entry 10.4 degrees. The HornsPl. company designed some of it's fiberglass horns from the outset with a certain exit angle for a specific driver. Check them out on the Autotech site and diyAudio. Or you could build a new paper horn for you specific driver. :)

If your are really interested about the exit angle matching, then just go to diyAudio on the "Geddes on Waveguides" thread and ask him yourself. I have an OSWG that is 12" in diameter and is good down to 1200hz. I can tell you it has almost no throat. It is almost an entry, then a fast flare with a mouth.

When thinking about this and your driver and xover point I keep thinking about that ancient saying, "You strain out a gnat, but you swallow a camel." I don't mean this in a bad way, but I think you might be breaking bigger horn rules than Geddes connection rule.

Everybody has their own theories about horns, and audio, so I will tell you mine since it seems to be different from most commercial horn systems I see. It is; I follow the rules. The rules of acoustic horns. I learn the natural rules governing horn as best I can, the I stick within them. Have I bent and broken them before? You bet. But I found that if I stick within the rules I get better sound. Simple as that. Certainly doesn't make me smart. All the guys who design and sell home horn speakers know way more about horns that I do, but they can never resist the temptation to cheat, because they have to make them just a tad more commercially acceptable. A little smaller, a two way. IMHO I modified a Klipsch Heritage fully horn loaded speaker, and made it sound better than Paul Klipsch did. Still PWK was a horn genius, and I am not, if you follow me.

Linked below is a recent testing review by John Atkinson of a German horn loudspeaker. He astutely caught that the mid horn was being run outside of it's proper operating range. $50,000.00 speakers. See, they can't resist bending or breaking the rules, not even for $50K speakers.

About your bent tube. Remember, when the size of the soundwave is smaller that the neck of your horn, the horn ceases to exist. Paul made a good point about what happens in the bend when the soundwave is contacting the sides of the horn, but when the soundwave is smaller that the tube the soundwaves just start bouncing around inside the neck. This causes internal reflections, High Order Modes as Geddes would say. This creates distortion. A 10Khz wave is smaller that 1.4". In your case that means all the signal above 10Khz is going to become distorted.

Last thing. I will share my thoughts with you on the highpass for a midhorn. I once ran a 350hz tractrix horn with an EV K55 driver using a first order slope. It went into gross distortion constantly. In fact sometimes the diaphragm unloaded totally, and you could hear the diaphragm flopping and buzzing around, probably banging against the phase plug. Not good. It's not the K55's fault. It can go very low, because it uses a phenolic (polymer) diaphragm. Your Radian uses titanium or beryllium? Neither are made to go low.

I take a different view about all this than is probably commonly accepted. Paul talked about letting the horn's theoretical cufoff be part of your acoustic crossover. PWK did that. I don't agree, and I try not to do this. Several reasons.

If your driver is putting out signal close or below the Fc then the horn can't pass it, and the soundwave collapses at the mouth of the horn, then falls back down the horn back to the throat, and becomes standing waves in the throat. This creates distortion, and helps to overload the throat, which you may be overloading anyway by sending a lot of high end signal out as well. Like using it as a two way, trying to send one and a half decades of bandwidth through one horn. At least this is how I understand it.

Then on top of that you are sending substantial electrical signal to the driver below the horn's Fc. So the diaphragm is operating unloaded, which probably means it is vibrating violently, which is not conducive to good sound.

Myself I like to have the signal attenuated down -12 to -15db at the horn's Fc. Less distortion. Better sound. YMMV.

Now if you get lucky, and the driver just happens to roll off where you need it to, then you can always incorporated that into your acoustic crossover.

Whew! Man, I ain't even proofreading this one.

---------------------------------------------------------------

Big speakers and little amps blew my mind!

 

Single and double K-Tube cutaway designs, posted on February 5, 2017 at 08:24:45
moray james
Manufacturer

Posts: 1406
Location: Calgary on the Bow
Joined: May 19, 2002



I set mine up so the centre of the tube is at my seated ear level parallel to the floor each tube is pointing directly at my head more of less set up can vary plus or minus a little. Solid sections to the left and right cutaway sections up and down. will send another picture with a single cutaway version mounted on my EVDH1A with the extender nose cup which gives a two inch exit. Cup can be removes to reduce exit to 1.4" dia.
moray james

 

RE: Single and double K-Tube cutaway designs, posted on February 5, 2017 at 08:27:00
moray james
Manufacturer

Posts: 1406
Location: Calgary on the Bow
Joined: May 19, 2002







moray james

 

Your answer got me thinking, posted on February 7, 2017 at 00:25:22
pix
Audiophile

Posts: 366
Location: sweden
Joined: March 18, 2006
Thank you very much for an exhaustive and personally experienced reply. After all, there are no "truth" in this. Just different point of views, and a choice on whom to learn from.
First, to answer your question. No the Radian 750Pb has an aluminum -membrane.
Second, what you write about "You strain out a gnat, but you swallow a camel" is really what I needed to hear to get this horn extension ide a rest. I often get stuck in one specific detail, when I should discuss the whole system. I will later write down my complete system asking for advise where my weakest points are, and initially focus on them.
Btw, calculating with the horn cutoff (As PK did) as an acoustic filter sounds really like jeopardizing with the devil. A flapping membrane will surely put hard strain on the membrane surrounding even if not hitting into the driver dome. I prefer to handle this electrically with the filter. As I mentioned, I had settled on a 1´st order, 350Hz HP-filter for the horns. But surely there are more room for experiment here. Looking around, most people with similar setup uses higher order filters, which make me wonder if I turned back to my initially solution to easy. I have previously tried higher order passive, and active filters and also gone digital by using a miniDSP device. But after listening for months I always return to the simple solutions.
My experience of commercially driven gear is (as you described) that they are often far from optimized for their task, and that's why I seldom visit highend shows or hifi stores anymore. I prefer to learn and do it by myself. Ones avail I ask myself what is the goal of this hobby. For me it´s the craftsmanship, finding new ways to make things and understanding how (why) they work, more than the music itself. The feeling of turning (often cheap scrap) into good locking, well working gear gives me a good feeling.

Best
/Pix

 

Nope not yet, posted on February 7, 2017 at 22:56:29
pix
Audiophile

Posts: 366
Location: sweden
Joined: March 18, 2006
Hi Moray
As you know I have built a pair of K-15 cabs with Beyma P15Fe woofers.
But I have never tryed (or heard) the Karlson tubes.
I know Freddie said there are compeditrors to horns so perhaps later on I will try. The K-15 works fine, but I think they are a bit slow compared to my horns. I am not sure if thats caused by the woofer I chosed or the design itself.
BR

 

RE: Nope not yet, posted on February 8, 2017 at 09:13:39
moray james
Manufacturer

Posts: 1406
Location: Calgary on the Bow
Joined: May 19, 2002
I just wanted to take the opportunity to help Fred spread the K-love. I wonder if adding some high efficiency damping like corning 703 to your K-15 to increase the apparent volume of your cabinet would help? Plenty of space above and below the woofer and on the back baffle for a layer of on edge damping as well as on the walls of the upper cavity (damping on edge will have better absorption of energy than the material on the flat side will). Keeping in mind that an open volume of resonant air must be available in each compartment of the speaker and that the vent areas must also be open.
I looked but did not find data at Beyma for your woofer. Is the Qt of your woofer around 0.3? This should be desirable for obtaining the lowest tuning in the smallest volume. I think that Karlson cabinets seem to like lowish Q drivers I believe. I think that when you match the system Q of devises then they mate well appearing to have like sonic qualities. I don't know if this will help but getting the damping right can have a significant impact on driver performance in cabinets both vented and sealed. Good luck and please post more pictures of your speakers and system. Regards moray james.
moray james

 

RE: Your answer got me thinking, posted on February 8, 2017 at 17:18:41
Mr_Steady
Audiophile

Posts: 945
Location: North Florida
Joined: August 19, 2014
You're welcome pix. I was just trying to point out some pitfalls that you have to remember are there. I think the truth lies in the fact there are a lot of right answers, because everybody has a slightly different need. For instance I don't know how loud you like or are able to play because of your living arrangement and neighbors. You might listen at a rather low volume, so your speakers are less stressed, and distortion or compression isn't so much a problem. You can get away with more. I was writing from my view point, which is I like music, and I sometimes like it loud. Usually in fact. I can get away with playing it loud, so I need my speakers to sound good at loud levels with low distortion. That's harder to do. I have to be a little more conservative. I am happy to say that I think I have a pair of speakers that play as loud as any home speaker you could wish, and it has incredibly low distortion. I really love the way they sound, and with only three and half watts! I think if any of the bad things I described before were happening with your speakers you would hear it.

Since you like the technical side and you have the miniDSP, then you should buy the calibrated mic for it. As DIY as you are you will need to test your horn and woofer. You may be using the old tried and true passive xover calculations. Try finding a program that helps design an xover with a flat impedance. ALK Engineering sells xover design software. It really makes a difference with SET amps. Trust me on this one. If you don't mind active xovers then try one of the Marchand active xovers. I can't recommend them highly enough. They really are great, and they have little pc cards to change the slope and type of crossover. It makes it very easy to try different arrangements. Symmetrical, asymmetrical, anything you want.

Lastly a conservative recommendation for your set up might be a second order slope at 500Hz, if your woofer goes that high. Third order slopes are good for horns, and at least they actually do something, unlike first order slopes. First order slopes are good for direct radiators generally, or direct radiator only speakers I should say.

I hope you get to a point where your technical side and the musical side come together for you.

-------------------------------------------------------------------
Big speakers and little amps blew my mind!

 

RE: Nope not yet, posted on February 8, 2017 at 22:48:48
pix
Audiophile

Posts: 366
Location: sweden
Joined: March 18, 2006

Thank you Moray,
I have a roll of insulation wool in my shop, so I will try to add some inside the K-15.
When built I followed the original drawings by the book and have not tested this.
This picture shows how much wool I use. and there are definitatelly room for more

All progress is shown in the tread linked below

 

Here are the TS-parameters for 15P80Fe, posted on February 8, 2017 at 22:58:14
pix
Audiophile

Posts: 366
Location: sweden
Joined: March 18, 2006
THIELE SMALL PARAMETERS
Fs 32 Hz
Re 5.3 ohm
Qms 5.5
Qes 0.19
Qts 0.18
Vas 305 l
Cms 279 µm / N
Rms 3.2 kg / s
Efficiency % 5
Sd 0.088 m²
Xmax 7.5 mm
Vd 660 cm³
Le @1 kHz 1.2 mH

TECHNICAL SPECIFICATIONS
Nominal diameter 380 mm 15 in
Nominal impedance 8 Ohm
Minimum impedance 6.3 ohm
Power capacity 800 W AES
Program power 1600 W
Sensitivity 101 dB 1 W @ 1 m @ 2Π
Frequency range 30-4000 Hz
Recommended enclosure volume 40 / 150 l / 1.4 / 5.3 ft³
Voice coil diameter 101.6 mm 4 in
BL factor 22.1 N/A
Moving mass 0.088 kg
Winding length 20 mm
Air gap height 12 mm
Xdamage pp 52 mm

 

RE: Nope not yet, posted on February 13, 2017 at 18:58:25
freddyi
Audiophile

Posts: 3144
Joined: December 6, 2001
not all horns seem to blend well with the Karlson slot - For midrange, I didn't not like my Edgarhorn rectangular tractrix as much as a big radial horn. - IF your relatively heavy woofer can make it to 2K then give a K-tube a try. (that's in regard to using typical one-inch format compression drivers) I think a baffle that's wider than the compression driver's diameter and placed at the throat may help blending in some cases. Use cardboard to find out.

A K might be slow compared to horn - my K12 sounds a lot faster than my Klipcshcorns and perhaps other midbass/bass horns - its been awhile since I ran K15. K15 is somewhat tuneable via its rear lowpass gap area.
Karlson Evangelist

 

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