Let's get horny! (aka building a horn design resource)

[paulspencer]

Horn design seems one of the most difficult areas to get into. There is a lot of information out there, but it occurs in dispersed fragments. I have yet to find a good, simple, one-stop resource that can help someone start from scratch. It's overwhelming, one has to wade through a lot of lingo and there seems to be no estabilished method.

I can't even find a book on horns (recommendations anyone?)

I'm trying to piece it all together for myself for a basshorn project ...

IDEA: create a simple online resource with everything a diyer needs to know in concise format

Everything? Not a comprehensive manual, but a simple explanation of the minimum you need to know.

* has anyone seen anything like this?
(if so, please show me)

* who would like to contribute?

I would like this to be a collaborative effort. We could do a wiki. I'd like to publish an edited version on my website, and also have it in a pdf format so that it can be downloaded.

Outcome:
My goal would be that a diyer who wants to design a horn could read the resource and in the shortest possible time be able to start using hornrsep (for example) right away and get a reasonable result just like with a vented box.

It could include:
* introduction - brief discussion of horns, pros and cons
* horn types
* terminology
* horn theory basics - charts, formulas
* driver selection guidelines
* simulation - basic guide to hornresp and any other programs
* case studies - 1 of each type of horn so that you will find something similar to anything one is likely to want to try
* plans - including all that is necessary to implement a pre-existing design for anyone who wants to do a copy rather than go through the process

I'd especially like to hear from HE and horn experts and I'll be following this post up with lots of questions (many of which I'll have to search first).

Contributions sought:
* horn projects you are willing to provide info on (or you have already documented) - either your own horns, or ones you have seen
* anyone willing to put together a basic tutorial on using particular software
* anyone willing to help with writing any part of the guide
* horn newbies and diy newbies to ask all the newbie questions that I want to make sure are covered (no sense writing a guide to learning German that only a German can understand!)
* horn enthusiasts to answer all the questions!

Disclaimer: Please be aware that what I publish on my site will be heavily edited, and possibly re-organised, and any unnececessary content removed. I say this in advance as I don't want to offend anyone, but anything submitted will be treated as raw materials and stripped back to bare essentials.

 

[wboyd]

I to am in the throws of a horn project right now. It is my eventual goal to have a 3-way horn stack controlled by a Berhinger DCX 24/96. The things that seem to slow me down at this point are time and money!

I have most of the pieces that I need:

75 hz Tactrix mid bass horn completed (test model at least) driven by an Electro Voice 12 mid bass driver.

My highs will be coming through a BEC 25 coupled to a DDS horn

I have not decided on a design for my bass horn as of yet. I have been seriously looking at building a Lab 12 based sub, but this seems like a pretty complicated (and expensive) build. I could get the tuba24 or 36 plans from Billfitzmaurice.com (I have heard good and yet mixed ideas about his designs, but usually good in general. My woodworking skill are decent at best, so I try to stay away from really complex designs.

I got most of my info on horns from a guy buy the name of John Sheerin. He was local to me until about a year ago. He took a job out in CA. His site has tons of horn info as well as theory (but no designs posted). check it out at http://ldsg.snippets.org/HORNS/index.php. I learned alot from this guy, very sharp person.

After doing tons of research on the subject I have found many resourcefull sites on the web. Some however, are easier read than others.

And yes, the idea of a really easy to follow DIY resource on the web is an excellent idea. I wish that I had found an easy, concise resource earlier on than I did...would have saved me alot of time and money. Alot of my blood, sweat and tears have gone into my current test models.

If you like, I will keep you updated on my progress in the future...although it has been slow lately. I will try and get a new website up and post the details there in the future....

So much to do...so little time.

Have a great one,

Wayne

 

[DorinD]

Very good idea, PaulSpencer! Also, a separate topic here, dedicated exclusively to horns, could be a solution to concentrate the information.

@wboyd
Sorry for asking you for an opinion about my 3way horn DIY project here http://www.diyaudio.com/forums/showthread.php?s=&postid=689484#post689484 because seems evident to me that you have ways more experience in horn construction.

I use PAudio E10-200S driver for bass, Selenium D405 plus HM47-50 for middle and ST350 for hights. Also, I use a good quality and ready to use passive cross at 600Hz (6dB/octave) and 5kHz (18dB/octave).
Before burn-in the middle and hights sound crispated and 3-5dB louder than the bass. But after a week of burn-in all is at the same level and sound fine (bass was increased and hights were smooted).
I thouth like you to use a Behringer DCX2496 to cross the ways but now I'm thinking to remain to passive crossing and use a Behringer DEQ2496 to make tweeks.
Sorry to be off-topic!

 

[John Sheerin]

Hey Paul,
As Wayne mentioned, I have some information on my website (actually I think you already know...). I have one page where I made a feeble attempt to lay out how I design horns, going at it from a DIY perspective. The problem in writing such a page is that horn design is really complex, so it is hard to know how detailed to get and hard to get detailed enough without writing a book. Also, when you go for more detail, the tendency is to skip over a lot of basic stuff, assuming your audience is already familiar with it. To really completely model and design a horn system, you must resort to FEA techniques which most DIYer's cannot employ. I feel like it's kind of a cop-out on my part to say that's where I get the last bit of my information in the computer design phase, but that is the only way I can really get it. (Of course you can always just build something, measure, and iterate, but it is hard to engineer as sophisticated a system that way).

Wayne - nice to (virtually) see you. Shoot me an email - I have an idea for an easier LAB12 horn. Btw, I am back in Indiana.

John

 

[paulspencer]

Wayne and Dorin, thanks for the feedback. Keep me updated, I'd like to see what you come up with. I may set up a website a section with examples of horns that diyers have built.

I'm keen to get DCX sometime in the relatively near future as it seems to open up a lot of different possibilities, especially for someone like me who wants to try everything ...

John, I was hoping I might hear from you. Yes I have seen your site, in fact read at some stage virtually the entire contents over the last 2 yrs. My goal would be to make information more accessible, and help diyers have a faster learning curve. As you say, most of us won't be horn experts.

For those who want the performance without the learning curve, I'd like to put together some examples documented sufficient for a diyer to do a copy. If we have a number that are willing to describe their system, and submit photos and scanned sketches, I can put together some CAD plans.

 

[cyclotronguy]

John

Drop me a line please... off forum.

Cyclotronguy

 

[mike.e]

Wayne and Dorin, thanks for the feedback. Keep me updated, I'd like to see what you come up with. I may set up a website a section with examples of horns that diyers have built.

I'm keen to get DCX sometime in the relatively near future as it seems to open up a lot of different possibilities, especially for someone like me who wants to try everything ...

John, I was hoping I might hear from you. Yes I have seen your site, in fact read at some stage virtually the entire contents over the last 2 yrs. My goal would be to make information more accessible, and help diyers have a faster learning curve. As you say, most of us won't be horn experts.

For those who want the performance without the learning curve, I'd like to put together some examples documented sufficient for a diyer to do a copy. If we have a number that are willing to describe their system, and submit photos and scanned sketches, I can put together some CAD plans.

Paul,If you email me we can discuss something here. What ive tended to do is keep an eye on the forums,and post my generic help to people and if they still need help,they email. There is info about-enough to build things of decent quality but its just spread out. A page with links and step by step process would help.

You have to believe that the people who really want one,will get it and the ones who give up,are the ones who might not appreciate it anyway

Heres What I did
http://www.diyaudio.com/wiki/index.php?page=basshorn

Its about all I can be bothered with really,Im not qualified to do much more. The midrange horns people are building are easily seen on volvotreter.de etc.

Much of the info required is in olsons acoustics,and its no use telling people half the story. A certain understanding of drivers and physics is required - then some horn theory can be give,length,mouth size requirements(dinsdale horn files) then the edgar horn type of reactance annulling. Or just build a tuba

Mike.e

 

[paulspencer]

Well, I think I got a bit ambitious with this thread about how far I might go. Instead of an all-out effort, I've settled on putting together a few pages now in progress on the wiki.

I'm starting with bass horns

faq:
http://www.diyaudio.com/wiki/index.php?page=Bass+Horn+FAQ

glossary:
http://www.diyaudio.com/wiki/index.php?page=Bass+Horn+Glossary

design guidelines:
http://www.diyaudio.com/wiki/index.php?page=Bass+Horn+design+guidelines

The idea here is to get some basic info together in a very concise format. Putting all the dispersed info together. Others have written articles, this is just a simple reference with the terms, some faqs and some basic info to start designing a bass horn.

Don't expect anything polished for a while, and keep in mind at this stage it might contain some errors and misconceptions.

 

[MJK]

Paul,

You wrote :

"Dont over compromise and make your basshorn a transmission line!"

How are you going to do this in a reasonably sized enclosure? What size mouth will allow this goal to be achieved?

 

[rick57]

Excellent ~ ambitious ~ idea

You should see if Bruce Edgar can contribute; and in case you didn’t know there’s good info at www.volvotreter.de/ .

Cheers

Richard

 

[paulspencer]

I didn't do that response (I think mike.e added it), but its a good question.

If someone can shed some light on when this becomes an issue, I'll include it.

What is "reasonable" will vary a lot for different people. According to my current info, a single 40 Hz bass horn should have a mouth and physical length approx the same as the Lab horn when corner loaded. This is without any shortening. IMO this is reasonable for a lot of DIYers. In fact, it seems that the Lab12 is a good horn to build (difficult in constructing aside) if one is corner loading. From what I can see, it only really compromises the mouth area and length if you want it to horn load below 40 Hz.

I have some basic guidelines to work out the length and mouth area you should aim for, but I'm not sure how to also include an expansion contour ... thoughts anyone?

 

[MJK]

OK, 40 Hz is a good frequency to shoot for so lets use it as the goal.

"it seems that the Lab12 is a good horn to build"

What are the mouth dimensions of the Lab horn? If we include corner loading, we should be able to determine if it is horn loading or TL loading at low frequencies. I think corner loading is going to be the only option that will produce a reasonably sized horn.

 

[paulspencer]

The mouth of the Lab12 is 0.53 x 1.1m

 

[MJK]

Ok, if I do a little math I come up with the following fc's with respect to the Labhorn.


Mouth Area = SL = 1.1 m x 0.53 m = 0.583 m^2


Mouth cut-Off Frequency

fc = c / [2 (pi x SL)^0.5] <--- derived from 2 x k x aL = 2


Without boundary reinforcement :

fc = 127 Hz

With floor reinforcement :

SL' = 2 x SL

fc = 90 Hz

With floor and one wall reinforcement :

SL' = 4 x SL

fc = 64 Hz

With floor and two wall reinforcement :

SL' = 8 x SL

fc = 45 Hz


With the rectangular shape, I do not know how you can corner load this cabinet. So my guess is that best case, horn loading probably does not become effective until about 64 Hz. If there is significant bass output in the 40 Hz range, then I would propose that it is more TL loading then horn loading. There is nothing wrong with a TL/horn approach.

Please correct me if I have done something wrong in the calculations above.

 

[paulspencer]

Martin, if it were me using the lab horn, I'd place it so that the mouth fires into a corner. Hence it would be set back a little, either along the side wall or back wall pointing to the corner formed by the side and rear wall.

As shown in the first example on John Sheerin's site:
http://ldsg.snippets.org/HORNS/basshornfea.html

[IMGDEAD]http://ldsg.snippets.org/HORNS/images/hornfea/FEA_horn_in_corner.jpg[/IMGDEAD]

Apparently another placement can extend the cutoff lower, but I think it's makes the horn intrude a bit much into the room

 

[slowmotion]

Hi all

I would recomend anyone interested in building horns to get
McBeans Horn Loudspeaker Response Analysis Program:

http://www.users.bigpond.com/dmcbean/

This program is very good for getting a feel for what might work
and what might not work with horns.
The program is also very simple to use,
when you get used to it you can "make" ( simulate ) a new horn in seconds.

After "making" at least 144 different horns in a simulation program like Horn Response,
with different drivers and so on, you might get to the point that you
want to actually design and build a prototype horn.
Several spreadsheets are available for designing horns, you can also use
spreadsheets and programs like Horn Response in combination.

I have to say that IMHO it is very difficult to build a good sounding horn.
Most of the horns I've built have been no good.
Straight horns are not so bad, but whenever you start folding a horn most of the theory goes out the window.
That include the nice results you got in the simulation programs.

Of course you have to measure your prototype(s) ,
redesign, make more prototypes, and so on and so forth

I know I sound very negative here, that is not my intention
Personally I think a good multiway hornsystem is the only way to reproduce music in the home.

Regarding reading matter and so on:

I've found a lot of information on the US patent site:
http://www.uspto.gov/patft/index.html

Another good source is Journal of the Audio Engineering Society:
http://www.aes.org/journal/search.cfm

cheers

 

[paulspencer]

Jan,

I've made a very sketchy start to a wiki on Horn Response, which I've used quite a few times, but have to confess I don't yet know exactly what every entry means.

Got some links to spreadsheets? I'd be interested to see them.

I have to say that IMHO it is very difficult to build a good sounding horn.

Why is it so hard?

I'd like to see if it can be made easier, if it is REALLY that hard

Most of the horns I've built have been no good.

Do you know why they didn't perform well? Were they bass horns?

At the moment my focus is on bass horns (keep that in mind with my above comments) ...

Straight horns are not so bad, but whenever you start folding a horn most of the theory goes out the window.
That include the nice results you got in the simulation programs.

I've been reading a little on this. Apparently some of the ill effects are driver dependant, and this isn't quite so bad for folded bass horns if the bandwidth isn't too wide and you cross reasonably low.

Anyone know how high the lab12 can go?

 

[slowmotion]

Hi Paul

Jan,

I've made a very sketchy start to a wiki on Horn Response, which I've used quite a few times, but have to confess I don't yet know exactly what every entry means.

Got some links to spreadsheets? I'd be interested to see them.

One of the more interesting spreadsheets is the one of Jean Michel Le Cléac'h:
http://ndaviden.club.fr/pavillon/lecleach.htm#ancre68820
Some good information also on this page if yu can read french.

More links on the single driver website here:
http://melhuish.org/audio/horninfo.html

I think Volvotreter also had some on his webpage?

Gotta run, more later

cheers

 

[slowmotion]

Hi

Jan,

Why is it so hard?
I'd like to see if it can be made easier, if it is REALLY that hard

Making a good direct radiator speaker system is already very hard.
A good multiway horn system is harder.
The potential for good sound is IMHO greater with a multiway horn system,
but there's also a bigger possibility of screwing up.

Do you know why they didn't perform well? Were they bass horns?
At the moment my focus is on bass horns (keep that in mind with my above comments) ...

The biggest problem with basshorns IMHO is that in order to really function as horns at low frequencies they get really big. You have touched on this in your wiki, a lot of the "basshorns" out there is really more like a labyrinth or transmission-line. I started out building the normal "small" basshorns and found out that they either did not go as deep as was expected, or that the response wasn't really that good. IMHO a good basshorn should function as a horn in it's intended passband. If the horn is too small , for instance, you would perhaps get a better result using a vented box or a transmission line instead. Or maybe a set of open baffles with really generous radiating area.

I've been reading a little on this. Apparently some of the ill effects are driver dependant, and this isn't quite so bad for folded bass horns if the bandwidth isn't too wide and you cross reasonably low.

My feeling on this is that you might - BEND - a midbasshorn carefully and get away with it up to maybe 300Hz. If you want to fold a horn I would try to stay under 60-80Hz. The wavelengths get so long then that the folds are not that critical. On the other hand a true horn
for use under 80Hz gets really big. And you need two of them for stereo.
Might have to build it into the walls , or under the floor, or something. Depends on how low you want to go. I feel that slightly under 40Hz is doable for horns placed inside a normal room. A friend of mine have 2 Labhorns in his living room, fireing straight into the corner,
they certainly sound very impressive.



cheers

 

[MJK]

Paul,

Thanks for the picture. I had not considered that placement option.