books and information on loudspeaker construction

[elcapitan83]

Hello all,

I was wondering who could reccommend a few good books dealing with the principles of horn loudspeaker construction.

As much as I enjoy the learning I recieve here, I want to examine how my LaScalas operate from a "textbook" point of view.

Thanks,

scott

[Colin]

STEREO BOOKS

1. Modern Recording Techniques

by David Miles Huber, Robert E. Runstein

List Price: $36.99

Paperback: 576 pages; Dimensions (in inches): 0.98 x 9.29 x 7.04

2. Home Theater For Everyone: A Practical Guide to Today's Home Entertainment Systems

by Robert Harley, Tomlinson Holman

List Price: $19.95

Paperback: 272 pages ; Dimensions (in inches): 0.69 x 9.98 x 7.03

3. Complete Idiot's Guide to Home Theater Systems

by Michael Miller

List Price: $16.95

Paperback: 304 pages ; Dimensions (in inches): 0.88 x 9.13 x 7.40

4. Practical Home Theater: A Guide to Video and Audio Systems

by Mark Fleischmann

List Price: $19.95

Paperback: 216 pages ; Dimensions (in inches): 0.60 x 8.96 x 6.30

5. Introduction to Loudspeaker Design

by John L. Murphy

List Price: $24.95

Paperback: 166 pages ; Dimensions (in inches): 0.45 x 8.38 x 5.48

6. Build Your Home Theater in a Weekend (In a Weekend)

by Cub Karabian, Gareth M. Debruyn, Gareth M. de Bruyn, Robert Lyfareff

List Price: $24.99

Paperback: 384 pages!; Dimensions (in inches): 0.86 x 9.12 x 7.39

7. Basic Home Theater Installation

by Gordon McComb

List Price: $25.95

Paperback: 140 pages ; Dimensions (in inches): 0.33 x 9.02 x 6.04

8. Home Theater Solutions (Solutions series)

by Joel White

List Price: $24.95

Paperback: 240 pages

9. The Home Theater Companion: Buying, Installing, and Using Today's Audio-Visual Equipment by Howard Ferstler (Sen$ible Sound sceptic)

List Price: $40.00

Paperback: 437 pages ; Dimensions (in inches): 1.03 x 9.50 x 7.55

[boom3]

"Loudspeakers" by Badiemaff and Davis. Some of the stuff is outdated, but the essentials are still correct. Don't think it's in print, but it was reprinted beaucoup times and should be easy to find.

"Acoustics" by Harry F. Olsen. A peer of Paul's, Olsen was the technical guru of RCA's audio business for decades.

"High Performance Loudspeakers" by Martin Colloms. Colloms is indeed an expert, even though I don't agree with him on every point. He's also one of those that tends to sniff at horns, particularly bass horns.

Back issues of "Speaker Builder", available from AudioXpress. Although not published anymore, SB was a valuable pre-Web forum and in the back issues one can trace the development of Bruce Edgar's horn designs.

If you have a university with an electrical engineering department nearby, they should have most of these references

The papers of Paul Klipsch (of course). K&A used to sell these in a binder. He also issued a newsletter called "Dope from Hope". A few years ago, someone on this forum was offering a copy for a modest fee.

[boom3]

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On 12/27/2004 12:48:13 PM elcapitan83 wrote:

Hello all,

I was wondering who could reccommend a few good books dealing with the principles of horn loudspeaker construction.

As much as I enjoy the learning I recieve here, I want to examine how my LaScalas operate from a "textbook" point of view.

Thanks,

scott

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

In a nutshell: An acoustic horn is a transformer that transforms the high pressure, low particle velocity wave at the driver to a low pressure, high particle velocity wave at the mouth. It matches the impedence of the driver to the impedence of the air in the room. It can also be compared to an antenna, although the transformer analogy is more accurate. Lower frequencies=longer wavelengths=larger horns. A bass horn may be folded to conserve space. Midrange and tweeter horns cannot be folded without introducing severe response anomolies. See my post above for the reference to the Bruce Edgar articles in back issues of Speaker Builder. Bruce knows more about folded horns than anyone presently living and his articles will explain the topic very well.

[D-MAN]

With regard to Bruce Edgar, I prefer other authors.

Also, I have not run across any Edgar patents, or any published scientific work by him, except in self-promoting magazine articles. So I purposely avoid his stuff. Also, I think that he tends to bad-mouth other horn designers in order to make his seem "better", which I consider to be a cheap shot, as it were. I never read anything where PWK said anything even remotely bad about another designer or compeditor by name. As a matter of fact, everything that I've read by or about PWK has indicated exactly the opposite, he placed credit where credit was due to those whose "shoulders he rode upon".

One thing that I have noticed, PWK was a teacher and I think that Edgar is not. PWK published alot, whether he was right or wrong in his conclusions, but it's all out there for everyone to see, and so are his products. He also welcomed experimenters and corresponded with them about his design and why he chose certain things or not.

Frankly, you would be better served by looking up the Klipsch patents and published scientific papers (many are on this site under TECHNICAL QUESTIONS posted for the most part by Gil) and many other's patents having to do with horn loudspeakers. There are many historically important patents and information about various horn enclosures.

The proven old stand-by "Building Speaker Enclosures", Badmaeff and Davis, mentioned above is also valuable as it contains calculations for horns and discusses different horn types, the Lee Concatenary being mentioned but unfortunately absent.

DM

[IB Slammin]

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On 12/27/2004 2:24:10 PM D-MAN wrote:

With regard to Bruce Edgar, I prefer other authors.

Also, I have not run across any Edgar patents, or any published scientific work by him, except in self-promoting magazine articles. So I purposely avoid his stuff. Also, I think that he tends to bad-mouth other horn designers in order to make his seem "better", which I consider to be a cheap shot, as it were. I never read anything where PWK said anything even remotely bad about another designer or compeditor by name. As a matter of fact, everything that I've read by or about PWK has indicated exactly the opposite, he placed credit where credit was due to those whose "shoulders he rode upon".

One thing that I have noticed, PWK was a teacher and I think that Edgar is not. PWK published alot, whether he was right or wrong in his conclusions, but it's all out there for everyone to see, and so are his products. He also welcomed experimenters and corresponded with them about his design and why he chose certain things or not.

Frankly, you would be better served by looking up the Klipsch patents and published scientific papers (many are on this site under TECHNICAL QUESTIONS posted for the most part by Gil) and many other's patents having to do with horn loudspeakers. There are many historically important patents and information about various horn enclosures.

The proven old stand-by "Building Speaker Enclosures", Badmaeff and Davis, mentioned above is also valuable as it contains calculations for horns and discusses different horn types, the Lee Concatenary being mentioned but unfortunately absent.

DM

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

........the Lee Concatenary being mentioned .......

Just to be a wise a**, it is spelled "Catenoid"....

[D-MAN]

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On 12/27/2004 6:00:05 PM IB Slammin wrote:

........the Lee Concatenary being mentioned .......

Just to be a wise a**, it is spelled "Catenoid"....

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

No slack for me, huh?! My spell checker ain't helpin here.

Ok, The Lee Catenary Horn, then. Happy?!

I got the book at home! Don't make me look it up!

DM

[IB Slammin]

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On 12/27/2004 6:13:10 PM D-MAN wrote:

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

On 12/27/2004 6:00:05 PM IB Slammin wrote:

........the Lee Concatenary being mentioned .......

Just to be a wise a**, it is spelled "Catenoid"....

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

No slack for me, huh?! My spell checker ain't helpin here.

Ok, The Lee Catenary Horn, then. Happy?!

I got the book at home! Don't make me look it up!

DM

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

...... Don't make me look it up!.....

Well sure, I had to. ( I need spell check..BAD ) Only a mention of him for me too. Wonder if anyone has pix or specks?

Regards,

Terry

[D-MAN]

Terry, the ONLY reason that I brought that up was that I ran across a US patent for a catenary back-loaded horn that referred to the Badmaeff and Davis book, which I also own.

The poor guy also could not find anything on the subject anywhere to use in his patent for documentation of the catenary horn.

I thought it was rather strange that I had not ever seen or heard of one, either.

Thought I'd bring it up to further add to my quite impressive blatherings on the subject to lend the weight of knowlege and science to the discussion and therefore increase (even further) the already high regard in which I am held by those on this illustrious BBS.

DM

[Dylanl]

The book called " How to build speaker enclosures " by Alexis Badmaieff is a good book based on older speaker designs. It also has a few of the Klipsch & Altec line plans. I think the short horn, the Klipschorn & the VOT Altec. Good easy reading for the beginner.

[John Warren]

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On 12/27/2004 2:24:10 PM D-MAN wrote:

it contains calculations for horns and discusses different horn types, the Lee Concatenary being mentioned but unfortunately absent.

DM

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

The L.E.E Catenoid

[WMcD]

It is a difficult subject. To quote the Tappet Brothers (Tom and Ray on Car Talk), "If you make the explanation technically accurate, it is incomprehensible to the layman. If you make it comprehensible, it is inaccurate."

I have posted a lot of stuff and unfortunately don't keep track of it. There is an article on the K-400 in Technical Questions about two months ago. Maybe someone can point you to it.

I do suggest that you go to the website of the US PTO at www.uspto.gov. You're going to have to learn how to navigate and find Klipsch patents. You'll see one on a horn with a unitary sound path (sometimes called the (ahem) little bastard, and one with a dual sound path (the MCM 1900). Here Paul Klipsch describes the design process. In the query at the PTO, use Klipsch as "Assignee Name".

You'll also have to download one of a few .tiff viewer plug ins. The most recent IE will view but not print, in my experience. So you do need something like Alternitiff.

At one point I'd posted the AES paper on the LaScala. Anyone know where it is?

The overall issue is something which really can only be understood with a EE course in transmission lines. The horn is a transmission line of graduated acoustic impedance as it goes from small to large in cross section. That is part of why people call it a transformer.

The other issue is what is attached to the small and large ends.

At the throat (small end) you want a driver of specific qualities. That is to say a good impedance match. PWK refers to Wente and Thuras and some electomechanical properties. Don Keele describe these in terms of T-S parameters of Fs, Q, and Vas.

At the big end, you're talking about mouth size to make the impedance match. Keele did a good analysis on this too. If you read the patents you'll see how PWK is relying on the corner to be an extension of the small mouth bass horn, or 1/8th space. These are the same in round about principles.

One of the biggest issues is the impedance transfer function of the horn. This is the "Big Picture". Again a very tough thing to do without diagrams and a lot, lot of study.

An important point is that the reflections from a small mouth screw up the impedance at the throat. However, they don't screw up things too much if the driver absorbs the reflected wave. I.e. the thing in the driver which makes it a good match for sending power down the horn also makes it a good absorber of the reflection.

= = = =

The LS bass bin is a nice easy design. I'll set out some things here and you can mull over them. Or perhaps someone else out there in cyber space can. I've written on this before and people who have been around here can go to sleep.

The exponential equation for expansion of the horn cross section says something simple. The area doubles every X distance of path length. In the LS, it doubles every 12 inches. It starts with a throat of about 1/2 square foot.

There are two paths but you add the cross section of them.

At the bend at the back, the path away from the driver/splitter is 1 foot and the area is 1 square foot (doubled). Coming forward, it is 2 square feet about half way to the front (two feet of travel or X, and we have another doubling of area).

At the front, that is to say the mouth, the path length is 3 feet of X. The area is four square feet.

= = =

That 12 inch doubling is called Lahmed by PWK (Hebrew for L, sp?). It is the cut off frequency of the horn. You multiply the doubling by 18.1 and find the cut off Fc equivalent for the horn in the exponential equation here as a wavelenght. We find it is a bass horn with a 63 Hz Fc.

What is the proper mouth size? Classically, it has to have a circumfrence which is one wavelength at Fc if we're dealing with "free space". Fairly large. But if you are radiating into a corner, it can be 1/8 as large.

- - -

This corner thing is another matter of study and "thought experiment". Consider a matrix of rooms in an apartment building. A corner is shared by the four rooms on that floor and the ceilings of the four apartments. Hence 1/8 space.

Alternatively, you see the corner as the last part of the horn flare. Again, it is a different way of looking at the same thing.

- - -

If you crank the math. The mouth of the LS is just about correct for 1/8th space in view of Fc.

- - -

I must stand up here for Bruce Edgar. I don't sign on to everything he has written but most are very good. His articles in SB were real inspirations and he shared his valuable insights. He was the first in recent times to encourage home building of horns.

Gil

[TBrennan]

The Badmienoff-Davis book was my first speaker building book WAY back when. Great book with Bozak, Altec, Jensen and Klipsch plans.

And worth it just for the info and pictures of John Hilliard's (Hilliard was Altec's head engineering honcho and in charge of the design of the Oscar winning Shearer Horn; he's the Zeus of the Great Horn Gods) huge infinite baffle system built into his 2-story stone fireplace.

As for Bruce Edgar; I've talked to Bruce on several occasions, he's twice been a guest at Chicago horn club functions. And he's always been helpful to the DIY horny. And I'm here to tell you that Bruce has great respect for PWK and his work and is a treasure trove of PWK stories and lore.

Bruce makes some pretty damned good sounding speakers too. He and Tom Danley from ServoDrive are, IMO, THE horn guys today. Once we had Bruce and Tom at the same function; they see things differently and the discussions (and mutual respect) between them were a sight to see.

IMO the best new, turnkey horn systems today are the Edgar Titan and a ServoDrive Unity horn atop a Contrabass. My opinion ya understand.

Now IF the Jubilee had gone into production.......

[TBrennan]

Here's the Unity-Contrabass system Tom Danley brought to a function we had. Sounded very good and was shaking northwestern Indiana.

[elcapitan83]

thanks a lot, guys.

in particular, i was looking for the formulas between cabinet/horn dimensions and low-end response. i realize that the low end of the lascala is hampered by it's physical size. increasing the volume will not just increase the low end response, however. i was wondering how to calculate cabinet volume and motorboard opening dimensions for a given low frequency response.

lets just say that i wished to use the stock k-33e, and wanted a bass response down to 20Hz. What would the interior volume/ motorboard throat dimensions be?

thanks,

scott

[D-MAN]

The formula for calculating the horn back chamber is this:

A=V/2.9R

where A = throat area in sq. in.

V = back chamber volume in cu. in.

R = exponential doubling point in inches where the cross-section area doubles in size. In the case of 40 Hz, the value is 22.7 inches, 12" = 60 Hz, etc.

The Khorn values are 78" for A, 5100 for V and 22.7 for R.

The back chamber can be reduced in size by 15-20% according to PWK in the "little bastard" patent, "Small Horn with Unitary Path". He explains his reasoning for this. Personally, I think you would be better off using the calculated size or you risk raising the overall fc of the enclosure, as it ignores the volume taken up by the driver, which can be over one gallon of displacement (231 cu. inches).

This gets a little convoluted when the horn is short. The LS/BELLE shows a reduced back chamber volume, as does the Khorn at approx. 4800 cu. inches. Since the LS was originally intended for voice reproduction and PA use, it makes sense to save space that way.

The point is to effectively match the air volume in the back chamber to the volume of air in the horn based on its rate of expansion and initial throat area.

DM

[WMcD]

Well, it could be done. For example, the EV Patrician is a K-Horn scaled up to take an 18 inch woofer.

One question seems to be whether the throat size for a K-33 changes if you put a bigger horn in front of it. No, the throat size is set by the parameters of the driver. The LS and the Belle are smaller horns, but they use the same throat size and driver. This is why.

The back chamber size does change with the Fc of the horn. That is what is referred to above.

Scaling up a folded horn will probably create another problem. The folds are designed to have a small radius so that the higher frequencies are not attenuated. The attenuation arises because part of the pressure goes around the long outside of the curve, and another part goes around the shorter inside radius. So there is a path lenght difference created. When you scale up, this becomes a bigger problem.

I seems to me this is what EV ran into with the Patrician. The bass horn wouldn't go up as high as the normal design (Georgian or K-Horn) and thus EV had to use a re-entrant low mid to go down farther. The re-entrant horn didn't work well at high freqs (folding issues again) and thus they had to add a high mid. The they needed a tweeter too.

You could look at the MCM 1900. That is a 32 Hz horn. It could be reverse engineered from the patent document. The Jubilee is good too. EV made a bass horn somewhat like the 1900 but the reported results were not advertized as being anything wonderful.

The bottom line is that 20 Hz from a horn in a room is a very tough project. Some people have built very big horns into the basement. That is just about required.

Best,

Gil

[boom3]

20Hz? Why? If you are looking to reproduce X.1 sound effects (where X = number of main channels) from a movie track, you are better off buying a good (Klipsch or Velodyne) subwoofer. Far cheaper and much, much less space. If you are a regular listener to organ music, you know that 32 Hz is the lowest pedal note, and not many organs have that monster pipe anyway. Much of the very low bass experience we feel at a live organ concert is vibrations (conducted and sympathetic) of the structure, conducted up the pew to our backs and fannies. A good sub will help but can never quite reproduce the intrinsic structural tone of a particular church or concert hall. Very few CDs have anything musical below 40 Hz, no matter what the subject matter. Klipsch recommended an active 'rumble' filter for the Heritage products. 45 Hz for the LaScala & Belle, and 28 Hz for the Cornwall & Klipschorn. At least 12 dB/octave.

[elcapitan83]

ok, admit 20hz is a bit low!

let us go for 32hz, instead.

i dont know, the 'scalas are better from corner placement, but i was thinking of building a set of "bases" that the speakers would rest on. if i opened up the bottom chamber, i could pick up more interior volume, and i could lower the frequency response?

i had heard of some guys opening into the sqwak/tweet chamber and inclosing the back to pick up volume, and instead of doing that, thought it easier to construct my own "base" and tune until i get the response i want.

i use these speaks for stereo hi-fi only, and i really detest subwoofers. i thought that it would be more simple to do it this way...but...apparantly, its not so easy as all that.

[Colin]

CDs certainly do have things musical below 40 Hz, no matter what the subject matter! I am using a Real Time Analyzer right now, the Behringer DEQ2496 UltraCurve Pro. Let me tell you, even the human voice has harmonics that extend below 40Hz.