# Midrange Waveguides, I knew you were waiting for this Abmolech!



## thadman

Waveguides, they are one of the new boners sweeping the technically inclined (and sometimes elitist) forums. Although, the subject of this post is one not often discussed, midrange (150-5000) waveguides. Their is a plethora of information available online (and off) thanks to Earl Geddes with reference to waveguides and compression drivers, but little regarding midrange waveguides

Judging from your enthusiastic posts concerning waveguides, you're (Abmolech) probably the most qualified member on this forum to assess the necessary attributes required for attaining optimal performance (least HOMs, most consistent power response) through their usage.

Rather than asking specific questions which presuppose certain circumstances which may not apply to all users of this forum, would you care to educate us on the benefits of midrange waveguides and how to properly design them?

Potential subjects to comment on:
According to my research, a spherical wavefront is the best match (least HOMs) for a conical waveguide and a planar wavefront is the best match for a OS (oblate spheroid(sp?)) waveguide and the throat is the most critical region regarding generation of HOMs. Also, conical waveguides begin to narrow in dispersion once the wavelength reproduced approaches the circumference of the throat. Earl Geddes also expressed interest regarding a different type of phase plug that minimizes generation of HOMs in the throat, but felt it was too costly to have them machined solely for his purposes and thus opted for open-cell foam in the Summa.


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## FoxPro5

It's all just bla bla bla technobabble ******** until you've put it in a car and had someone with superior ears judge it. 

What can i say, I'm subscribed for more!


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## thehatedguy

I have made said foam plugs for horns, and they do help out a lot especially with horns that have parallel sides.

Are you wanting to know how to design waveguides or horns? I have a few good links on horn design...only a couple on waveguides.

For a decent primer of sorts, check out the white paper on the Peavey Quadriatic Throat waveguide.


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## thadman

thehatedguy said:


> Are you wanting to know how to design waveguides or horns? I have a few good links on horn design...only a couple on waveguides.


Waveguides


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## thadman

thehatedguy said:


> I have made said foam plugs for horns, and they do help out a lot especially with horns that have parallel sides.


parallel sides, could you be more specific? The way I'm visualizing your description, the waveguide would have no expansion...which of course doesn't make sense, it'd be a tube.


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## Whiterabbit

I believe he is referencing designs such as fostex folded horns where the enclosure has two parallel sides, where the remaining two dimensions expand to increase horn cross-sectional area.


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## thehatedguy

Nah, back loaded horns aren't my cup of tea as they only increase low end efficiency numbers...helps even out the rising FR.

I think Earl has said all horns are waveguides, but not all waveguides are horns.

You can have expansion of the throat in one direction while keeping the other 2 sides parallel. 

Anyone take a look at that Peavy white paper? You would see what I am talking about in it.

http://home.carolina.rr.com/charliehughes/Articles/QTWaveguide/QTWaveguide.html

http://home.carolina.rr.com/charliehughes/Articles/Articles-Fr.html


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## thehatedguy

But I would argue that Eric Stevens from ID is the most knowledgible person who visits this forum when it comes to midrange horn/waveguide design. ID used to share buildings with Bruce Edgar.

But that is just being knickpicky.


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## Thumpper

I have wave guides on my tweeters...(2 sets of JBL 660gti)
and they do make a huge difference with the high freq


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## 60ndown

i have a wave guide


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## dBassHz

I've read a bunch of info on waveguides on the internet. The only car audio application that I have seen is Patrick Bateman's. There is a bunch of good information in his thread on Carsound.


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## thylantyr

re: Earl Geddes

Audio Guru? yes

Is this Summa speaker design the best in the world? no
http://www.gedlee.com/Summa.htm

For everyone lover there is a hater :wink:
http://www.audioasylum.com/forums/hug/messages/87777.html

http://nfp.cba.utulsa.edu/bajaja/FreeAudioReviews/Reviews/AudioMeets/GPAF2005/ReviewGPAF2005.htm


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## Tommythecat

thylantyr said:


> http://nfp.cba.utulsa.edu/bajaja/FreeAudioReviews/Reviews/AudioMeets/GPAF2005/ReviewGPAF2005.htm


You trust a retard who lists his suggestions as:
1) blah blah
b) blah

? Really?

And I would love to see Abmolech actually give out information instead of techno-babble and refer to information he wont share with anyone - and possibly not answer this thread in riddles like many expert members on here do.


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## demon2091tb

Tommythecat said:


> And I would love to see Abmolech actually give out information instead of techno-babble and refer to information he wont share with anyone - and possibly not answer this thread in riddles like many expert members on here do.


Riddles are fun, if they don't put the info in the riddles then wheres the work on our parts......Can't give all the elephants in a circus a free ride, some have to work.

Would love to know more.


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## thehatedguy

There are more people than him who frequent the forum who know about horn theory.


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## dBassHz

dBassHz said:


> I've read a bunch of info on waveguides on the internet. The only car audio application that I have seen is Patrick Bateman's. There is a bunch of good information in his thread on Carsound.


Opps... I thought this was general audio.

Go with a Unity horn


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## thadman

Assuming the member has weighted the pros (restricted power response, heightened sensitivity, etc) and cons (physical size, CTC spacing, etc) of waveguides and come to the conclusion that they'd be an integral part of their loudspeaker systems, what should a member go about doing if they'd like to design one?

These are all pretty common questions that should have special attention paid to, IMO

Are there any considerations that should be made in the throat, as to minimize perturbations of the wavefront? 

Can Cone/Dome drivers be integrated into an optimal waveguide, what attributes (T/S parameters) are desired?

How to integrate Phase Plugs that generate a wavefront of constant amplitude/phase into the waveguide (generates least HOMs)?

How large should the waveguide (mouth, throat, etc) be for a specific radiation pattern/bandwidth? Any equations?

Elliptical or Oblate Spherodial?

etc.


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## thehatedguy

Cones and domes can be used on horns pretty well, but a compression driver will offer many magnitudes of lower distortion and output over a cone or dome driver. The benefits of a cone driver on a midrange horn would be that the horn is physically shorter than one on say a 2" compression driver. A lot of the coloration people complain about in horns is from a high initial compression of the wavefront...that high compression can distort the wavefront. You will also probably find that the shorter horns with a rapid flare rate like the tractrix of L'cleach will sound more natural b/c of that. However, you will get beaming the higher you go b/c the polar response of those horns will greatly start to narrow. People generally like to use horns no more than a 4 octave range b/c of that. But as always, there are exceptions to those "rules" and great 2 or 3 way systems have been built.

On that note of the rapid flare rates sounding more natural, it comes at a cost...those horns will not load the driver all the way down the cut off frequency of the horn. Generally you want to 1.5-2x above the flare rate for the driver to load. But if running your drivers down to the bottom end of the flare rate is important to you, you might would want to use the jack of all trades and the master of none flare- an exponential horn. It will load nearly all the way down to the cut off and has better pattern control over the tractrix and L'cleach.

That Peavy white paper PDF that I linked to has some basic overviews and the first link had the math behind it in it.

Good place to start searching is here:

http://audioheritage.org/vbulletin/

Those guys have built every horn/waveguide out there, and a few have build pictures and the math to go behind it. At one point there was an OS spread sheet there.

This one was ok a while back:

www.geocities.com/adrian_mack/homepage.html

Here for some Unity horn stuff:

www.cowanaudio.com/index.html

This is a good one too:

http://ldsg.snippets.org/HORNS/index.php

You might like this site too:

www.volvotreter.de/dl-section.htm


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## thehatedguy

I know you like to DIY, but Earl is doing kits with the 10" driver and waveguide these days. I think the whole package- drivers, baffle with integrated waveguide, and foam plug is about $600 a side. He has a post in DIYAudio in the market place under the vendor's bizarre section. If I had somewhere to put them, I would get a set to try.


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## thadman

thehatedguy said:


> Cones and domes can be used on horns pretty well, but a compression driver will offer many magnitudes of lower distortion and output over a cone or dome driver. The benefits of a cone driver on a midrange horn would be that the horn is physically shorter than one on say a 2" compression driver. A lot of the coloration people complain about in horns is from a high initial compression of the wavefront...that high compression can distort the wavefront. You will also probably find that the shorter horns with a rapid flare rate like the tractrix of L'cleach will sound more natural b/c of that. However, you will get beaming the higher you go b/c the polar response of those horns will greatly start to narrow. People generally like to use horns no more than a 4 octave range b/c of that. But as always, there are exceptions to those "rules" and great 2 or 3 way systems have been built.
> 
> On that note of the rapid flare rates sounding more natural, it comes at a cost...those horns will not load the driver all the way down the cut off frequency of the horn. Generally you want to 1.5-2x above the flare rate for the driver to load. But if running your drivers down to the bottom end of the flare rate is important to you, you might would want to use the jack of all trades and the master of none flare- an exponential horn. It will load nearly all the way down to the cut off and has better pattern control over the tractrix and L'cleach.
> 
> That Peavy white paper PDF that I linked to has some basic overviews and the first link had the math behind it in it.
> 
> Good place to start searching is here:
> 
> http://audioheritage.org/vbulletin/
> 
> Those guys have built every horn/waveguide out there, and a few have build pictures and the math to go behind it. At one point there was an OS spread sheet there.
> 
> This one was ok a while back:
> 
> www.geocities.com/adrian_mack/homepage.html
> 
> Here for some Unity horn stuff:
> 
> www.cowanaudio.com/index.html
> 
> This is a good one too:
> 
> http://ldsg.snippets.org/HORNS/index.php
> 
> You might like this site too:
> 
> www.volvotreter.de/dl-section.htm


The subject of this thread is waveguides, not horns.


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## thehatedguy

Ok, all horns are waveguides...horns provide gain and pattern control whereas waveguides only provide pattern control.

If you bothered to read and search around some of the links that I have provided, you would know that they contain information about both horns and waveguides.

And seeing as no one else is here posting on this thread who knows anything about horn theory...I thought that I would share what I know about horn theory. Seeing that you are getting as much help here as you are on DIYAudio with the same thread, I thought you would like to have someone posting who actually knows what they are talking about...since your boy Abmolech hasn't made an apperance yet to bail you out.

Some people just have to be an ass for the sole purpose of being an ass, and I guess you are one of those people.


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## thehatedguy

I mean, we can check out this thread for help:

www.diyaudio.com/forums/showthread.php?s=&threadid=122488

Lot of people busting out at the seams to post on that one...


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## ca90ss

thehatedguy said:


> Some people just have to be an ass for the sole purpose of being an ass, and I guess you are one of those people.


Pot.......kettle.........black.


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## thehatedguy

I was here trying to help. And I was the only one here who was trying to help. If he doesn't want to learn, then fine...you guys start posting about the topic.


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## thadman

thehatedguy said:


> I thought you would like to have someone posting who actually knows what they are talking about...since your boy Abmolech hasn't made an apperance yet to bail you out.


Bail me out? I can do my own research. This thread is intended for the average member on this forum, to make information on waveguides readily available through the "search" function, thus the intentional "ambiguous" nature of the initial post.

FYI, Abmolech has responded, but on a different forum. Several members here were very quick to point out that he wasn't the _acknowledged_ expert on horns and waveguides over here (Jason and Mark), so he's left it to them to discuss the topic.



thehatedguy said:


> Some people just have to be an ass for the sole purpose of being an ass, and I guess you are one of those people.


Whats with the Ad Hominem? It isn't necessary and it really shows a lack of maturity on your part.


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## thadman

thehatedguy said:


> Ok, all horns are waveguides...horns provide gain and pattern control whereas waveguides only provide pattern control.


All horns are not waveguides and this is basically because they do not constitute appropriate guides for the wave fronts that we are attempting to propagate in them, this leading to ‘multimodal” propagation. Earl Geddes first used the term "waveguide" to differentiate it from a "horn". The two devices use different equations and approaches and should go by different names. 

Thus, once again, the subject of this thread is "waveguides" and not horns.


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## durwood

A cone driver is a waveguide-curvlinear cones especially usually have the smoothest response. Ideally, you would want to construct a waveguide that almost mates up with the cone and follows the contour of it. This is ideal, but realistically the cone moves so this is near impossible. We can only hope for a best case scenario. This is why larger sized cones can easily play lower. 

From my basic understanding, you need to pick your desired coverage angle/dispersion pattern and lowest frequency you want to direct, and plug away into some calculations. At one point I started to create such an excel spreadsheet, but I ran into some troubles with the equations-either from the site or my actual syntax. I got bored trying to calculate everything and just started building and experimenting.

Things to pay attention to:
Throat depth
Width of mouth=Wm
Width of conical section=Wc
Ideal ratio of Wc/Wm~0.65-0.7



> A property of constant directivity horns is that they have a straight-sided conical flare for a large section near the mouth, Keele [13] showed that such a horn has a constant directivity above a particular frequency given by ...
> 
> F = Kk / α * w Where α = included wall angle, Kk = 25.306 x 10³ and w = mouth width (metres)
> 
> Note:The constant kk (Keele's constant = 25,306) is a compromise value related to rectangular horns. *A value of 29,707 is a theoretically better approximation for circular ones* as this is based upon the directivity of a pulsating spherical cap. This can only be true however at low wave numbers, the ripples that can be seen in the off axis trace of the 3kHz waveguide are higher order diffraction effects due to far field mode propagation at high frequencies and the spherical cap model is not accurate at the high end. The best compromise is kk = 25,306. This does cause the directivity at the lower end to be compromised somewhat - the usual specification calls for the output to be -6dB at the specified frequency. The higher value can be used for the three section devices to more accurately specify the lower cut off since these are free of higher order diffraction.


Read more here (athough most is taken from the guru Earl Geddes)...

http://sound.westhost.com/articles/waveguides1.htm

If you use 150hz as your frequency where you want frequencies above this point to be constant directivity, I think you will find the mouth is going to be fairly large:

For example take a 90deg dispersion angle and 150Hz:

Mouth diameter = 29707 /(150*90) ~ 2.20m in diameter.

Another good thing to note from this is that the wavelength of a 150Hz wave is ~2.3m ...once the sound leaves the waveguide all bets are off as to what happens to the soundwave.


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