A different look at horns vs direct radiators???

[Deang]

Anyone here besides Dennis hang out at other forums? Just curious.

Found this thead, thought you all might like it.

http://srforums.prosoundweb.com/index.php/mv/msg/18098/0/0/0/

[Don Richard]

Your statement:

"...and in the case of the Khorn this wavefront curves around the front face of the enclosure creating a virtual horn segment large enough to cause horn loading to below 40 Hz"

is not supported by anything I ever read by Paul or his proteges. In fact the two sides of the horn cause an intereference dip at some frequency. The front face of the Klipschorn is far too small to be an effective baffle at 40 Hz. If you are saying that the K-horn (plus corner) becomes the throat of a "virtual" 40 Hz horn formed by the room, then we must specify room size, wall stiffness, etc. In fact, even if the throat/driver could be tunnelled back into a room corner, a 90 degree room corner forms a conical flare, which would greatly reduce low-band efficiency.

If you read the current information on the Heritage Klipschorn, on this website, you will see that the walls of the room forming the final horn flare is clearly mentioned, as it has been in every brochure that I have seen, going back to the early 1960s. PWK undoubtedly approved, if not actually wrote, this description.

In "How To Build Speaker Enclosures" by Alexis Badmaieff and Don Davis, dated 1966, the authors say, "Figs 5-7A, 5-7B, and 5.7C illustrate the dual path the horn takes and how it is mated to the corner of a room to provide the final flare of the mouth. The listener actually sits inside the horn". Don Davis is a well known audio engineer whose credits include working with Richard Heyser and Crown Corporation to bring Heyser's Time Delay Spectrometry instrument to the audio engineering community. He also founded SynAudCon, a company that trained engineers in the use of TDS equipment, equalizers, and studio design. His newest edition of "Sound System Engineering" is considered a bible for audio engineers.

In fact the two sides of the horn cause an intereference dip at some frequency. The front face of the Klipschorn is far too small to be an effective baffle at 40 Hz.

In The Dope From Hope, Vol.2, No. 12, dated 10 November 1961, PWK writes:

"Back in 1948 we were aware of an interference effect from the right and left sides: a 40 deg. off-axis microphone placement under anechoic conditions (such as an inside corner outdoors) results in a deep response dip at about 280 cps. Also under similar conditions with a hard floor or ground there is an interference between the horn radiation and its mirror image below ground, and a microphone at a 4 foot height will show a dip at 350 cps.

These are typical standing wave phenomena: in spite of such effects the system radiates power and does so smoothly if all precautions are observed. In fact our claim of "10 dB peak-to trough ratio" can be bettered by several decibels".

In fact, even if the throat/driver could be tunnelled back into a room corner, a 90 degree room corner forms a conical flare, which would greatly reduce low-band efficiency.

The Khorn bass horn is composed of multiple conical segments. There ain't a curve to be seen anywhere in that enclosure. If you are suggesting that the Khorn has insufficient low band efficiency, you are just plain wrong. This has absolutely not been my experience, nor that of anyone who has listened to Khorns in a decent listening room.

"Last but perhaps not least, is the fact that the resistive component remains appreciable for a considerable range below cut-ff, so that some useful contribution of sound energy is avaialble from large-throat speakers". So, it seems that a woofer with a back chamber resonated above nominal horn cut-off is acting like an "infinite baffle" below the horns cut-off and that is why we still get usable bass out of horns below nominal cut-off.

You got that part right. Any horn can output below Fc, with reduced efficiency and increased modulation distortion. I never said they could not.

[boom3]

Your statement:

"...and in the case of the Khorn this wavefront curves around the front face of the enclosure creating a virtual horn segment large enough to cause horn loading to below 40 Hz"

is not supported by anything I ever read by Paul or his proteges. In fact the two sides of the horn cause an intereference dip at some frequency. The front face of the Klipschorn is far too small to be an effective baffle at 40 Hz. If you are saying that the K-horn (plus corner) becomes the throat of a "virtual" 40 Hz horn formed by the room, then we must specify room size, wall stiffness, etc. In fact, even if the throat/driver could be tunnelled back into a room corner, a 90 degree room corner forms a conical flare, which would greatly reduce low-band efficiency.

If you read the current information on the Heritage Klipschorn, on this website, you will see that the walls of the room forming the final horn flare is clearly mentioned, as it has been in every brochure that I have seen, going back to the early 1960s. PWK undoubtedly approved, if not actually wrote, this description.

In "How To Build Speaker Enclosures" by Alexis Badmaieff and Don Davis, dated 1966, the authors say, "Figs 5-7A, 5-7B, and 5.7C illustrate the dual path the horn takes and how it is mated to the corner of a room to provide the final flare of the mouth. The listener actually sits inside the horn". Don Davis is a well known audio engineer whose credits include working with Richard Heyser and Crown Corporation to bring Heyser's Time Delay Spectrometry instrument to the audio engineering community. He also founded SynAudCon, a company that trained engineers in the use of TDS equipment, equalizers, and studio design. His newest edition of "Sound System Engineering" is considered a bible for audio engineers.

In fact the two sides of the horn cause an intereference dip at some frequency. The front face of the Klipschorn is far too small to be an effective baffle at 40 Hz.

In The Dope From Hope, Vol.2, No. 12, dated 10 November 1961, PWK writes:

"Back in 1948 we were aware of an interference effect from the right and left sides: a 40 deg. off-axis microphone placement under anechoic conditions (such as an inside corner outdoors) results in a deep response dip at about 280 cps. Also under similar conditions with a hard floor or ground there is an interference between the horn radiation and its mirror image below ground, and a microphone at a 4 foot height will show a dip at 350 cps.

These are typical standing wave phenomena: in spite of such effects the system radiates power and does so smoothly if all precautions are observed. In fact our claim of "10 dB peak-to trough ratio" can be bettered by several decibels".

In fact, even if the throat/driver could be tunnelled back into a room corner, a 90 degree room corner forms a conical flare, which would greatly reduce low-band efficiency.

The Khorn bass horn is composed of multiple conical segments. There ain't a curve to be seen anywhere in that enclosure. If you are suggesting that the Khorn has insufficient low band efficiency, you are just plain wrong. This has absolutely not been my experience, nor that of anyone who has listened to Khorns in a decent listening room.

"Last but perhaps not least, is the fact that the resistive component remains appreciable for a considerable range below cut-ff, so that some useful contribution of sound energy is avaialble from large-throat speakers". So, it seems that a woofer with a back chamber resonated above nominal horn cut-off is acting like an "infinite baffle" below the horns cut-off and that is why we still get usable bass out of horns below nominal cut-off.

You got that part right. Any horn can output below Fc, with reduced efficiency and increased modulation distortion. I never said they could not.

Sorry to be disputatious...the concept of sitting inside the horn is advertising puffery from the 40s, and is just not true. Real horns don't have doors, windows, etc as openings. If it was true, why did Paul state that a false corner need not extend beyond four feet? The Davis book repeats the Klipsch advertisng line, out of respect for Paul. I think we agree on the results, just not the description of how we get those results. My point was that other would-be corner horn designers should have the right understanding of what corner actually does for a horn.

[DrWho]

Well technically, the Khorn does need the corner to finish its flare, but only because it doesn't have its own back. Nevertheless, I think it's more of a semantic argument rather than one of getting into the performance behavior.

[DrWho]

Anyone here besides Dennis hang out at other forums? Just curious.

Found this thead, thought you all might like it.

http://srforums.prosoundweb.com/index.php/mv/msg/18098/0/0/0/

I hang out on PSW off and on. Most of the people there remind me of when I was 16 so I only take it in small doses. []

[ZAKO]

The 60th anniversary Khorn has its own back,,,And can be moved away from the room corner... But still sounds better with corner augmentation.

[DrWho]

SO! you software nuts run the numbers above. I have sketched out the cuts for a horn for two JBL 2226 drivers. I was off a little on the back chamber volume. So......the horn will be a little longer and the mouth will be a little bigger.

You're not making one are you?

I'm beginning to wonder if the 2226 isn't just a bad driver for horn loading...more on that to follow.

[jwc]

You're not making one are you?

I haven't decided. I have one drawn out that I've been working on for a little while. I was hoping you or Edgar could throw those specs I posted and get your opinion.

You could put in 3 K31's or two JBL 2226's. The two JBLs need a little more back volume which I can change. This is just me dorkin around bentz. I don't want to steal your thread. Interested in your build. I've never seen you post anything you've built...except a few blurbs on that tapped horn. Like to see a cool project on the forum.

jc

[Edgar]

I took another look at my Jubilee HORNRESP model, and found some mistakes. I think that this one is better. The frequency response differences between new and old are very small, essentially identical below 100 Hz and above 500 Hz, with a maximum difference of about 2 dB at 200 Hz.

Greg

[Edgar]

Edgar and Bentz

Model this?  Not sure if this will fit in your "space" Bentz.

Mouth (exit) 7580 sq cm

Horn length (throat to exit) 122.7cm

Throat 870 sq cm

Put it in a corner. 

Here's what I get for a pair of JBL 2226J in the horn that you describe. Modeled as an exponential contour. Somebody check my numbers, please.

Greg

[Edgar]

I just noticed that I forgot to reset the Atc and Vtc parameters. If you set Atc to the throat area and Vtc to zero, the high frequency hump disappears. There is essentially no effect below 1000 Hz, though.

Greg

[WMcD]

It is not inaccurate to say the corner forms the final flare. Nonetheless, the corner is not a very good flare.

You can look closely at Keele's optimum mouth size for a horn in a corner, in his Optimum Mouth Size article. The K-Horn mouth is way too small.

An other way of looking at it shows up in his article about What's so Sacred. There we see a sketch of a hyperbolic feeding a conical and both are staight axis. There we see that the optimum mouth for the hyperbolic is where the slope of hyperbolic wall equals that of the matching the conical. There is no discontinuity. The math works out very closely.

That shows up in efforts to make a geometrical model on paper of any bass horn as mated to a corner.

1) Suppose you take an LS. The mouth size is 4 square feet. Now, look at the corner. You can find a place where the corner has an area of 4 square feet. It is fairly close to the corner. And you can't get the LS mouth that close to the corner. The bulk of the box gets in the way. One exception is if you turn the LS vass unit around to face the corner. This may be why good results are reported (by Greg928) in that situation.

2) The K-Horn has a 4 square foot mouth and the Jubilee has a 5 square foot mouth (pretty close, you can look at the figures given by Klipsch). You can estimate the size of an equivalent straigh axis bass horn with corner mentally. Generally you have the mouth of the bass horn in a baffle made up of the front plywood slab and the top slab. Let me guestimate those as 10 square feet. This pretty much sets the realistic size of the throat of the conical horn which is the corner and which the bass horn cabinet looks into..

What does this show? For the K-horn we have a 4 square foot mouth of the exponential bass horn in the cabinet, with a 10 square feet baffle made up of the face and top of the cabinet, feeding a conical horn which has a 14 square foot throat.

That makes for quite a discontinuity of the bass horn if the corner is the final flare. There is a sudden jump in the transition area from 4 square feet to 14 square feet.

Wm McD

[garyrc]

Somebody mentioned wall stiffness re: corner horns ....

I have had my Klipschorns in two rooms. The first had specially built ultra-stiff walls with 8" on center studs (in the corner area, extending to 5' out on both sides), and a floor braced with lintels against the joists in the crawlspace (as recommended by an audio magazine) --- it looked like Stonehenge down there. In that room the response of the Khorns was pretty good, with a dip somewhere around 200 Hz, and smooth bass not only to below 40 Hz, but an increase in very clean bass at 35 and 31.5 Hz centered warble tones!

In my current room, with ordinary sheetrock walls and 16" O.C. studs the same Khorns roll off below 40 Hz, and don't sound quite as clean and precise when low tuned tympani or big bass drums are beaten. When we finally redo the room, we will have 8" on center studs in corner areas, and lintels in the basement!

[seti]

Somebody mentioned wall stiffness re: corner horns ....

I have had my Klipschorns in two rooms. The first had specially built ultra-stiff walls with 8" on center studs (in the corner area, extending to 5' out on both sides), and a floor braced with lintels against the joists in the crawlspace (as recommended by an audio magazine) --- it looked like Stonehenge down there. In that room the response of the Khorns was pretty good, with a dip somewhere around 200 Hz, and smooth bass not only to below 40 Hz, but an increase in very clean bass at 35 and 31.5 Hz centered warble tones!

In my current room, with ordinary sheetrock walls and 16" O.C. studs the same Khorns roll off below 40 Hz, and don't sound quite as clean and precise when low tuned tympani or big bass drums are beaten. When we finally redo the room, we will have 8" on center studs in corner areas, and lintels in the basement!

That is very interesting. I live in a home built in 1890. The crawl space is 3 - 4.5 feet. I have been adding extra supports to make the floors more rigid. You know how old houses can be. I am going to add extra supports under my khorns now. I use concrete bases with floor jacks in case I need to make adjustments later.

[DrWho]

You're not making one are you?

I haven't decided. I have one drawn out that I've been working on for a little while. I was hoping you or Edgar could throw those specs I posted and get your opinion.

You could put in 3 K31's or two JBL 2226's. The two JBLs need a little more back volume which I can change. This is just me dorkin around bentz. I don't want to steal your thread. Interested in your build. I've never seen you post anything you've built...except a few blurbs on that tapped horn. Like to see a cool project on the forum.

Well sorry to dissapoint, but my boss kinda nixxed the idea. I just spent all last week repairing equipment and discovered that he purchased a few other items, which means we don't have enough space to go bigger anymore. [] So vented cab it is...*yawn*

I've got a final interview with a company on Monday, so hopefully I'll be figuring out an audio budget for the next few months. I've been dying to build some of my own horns and have always followed your build threads with great interest. Eventually I'll be getting around to a straight horn cab that can cover the 80-800Hz decade. I don't think 800-20kHz is asking too much for a 1.5" driver and then 80Hz and down can be covered by an array of direct radiating subwoofage.

Btw, did I not post pics of my tapped horn? I actually built that thing with the intent to throw it away, so maybe I can post some assembly pics as I tear it down.

[Daddy Dee]

Mike,

Hope all goes well on your interview on Monday.

BTW, the project you are anticipating sounds very interesting.

[jwc]

Good luck on the interview.

Yes, I saw pics of the tapped horn.

Maybe it's time for me to start a project......bass horn that is. My straight bass horn Fc of 80Hz was a success. May go bigger. Time is an issue though.....and so is my back.

jc

[jwc]

Greg. BTW. Thank you for the post with the curve and input parameters.

You know, when I put data into Horn Resp for a Tractrix horn, the Fc predicted from HornResp is diiferent that the Fc calculated for the horn. Example, if I put in numbers for a 1/2 space tractrix 90 Hx horn, Horn Resp will tell me the Fc is about 111Hz. This one happen if the horn is designed full space.

This doesn't happen with the Exponential Horn Resp predictions. If I put in a 90Hz 1/4 space horn, then the predicted Fc is 90 Hz.

jc

[DrWho]

Hey JC, which equations are you using to compare against hornresp?

[Edgar]

Greg.  BTW.  Thank you for the post with the curve and input parameters.

You're welcome.

You know, when I put data into Horn Resp for a Tractrix horn, the Fc predicted from HornResp is diiferent that the Fc calculated for the horn. 

Try opening up the Tractrix Flare calculation box by double-clicking on either S1 or S2, clicking on the "F12 Calculate" radio button, and entering not only the length but the Fta (tangent angle at the mouth).

Greg