re mass corner
The mass corner occurs at a frequency where the parallel combination of Rab, Raf, and Rvc, have the same resistance as the impedance of the capacitor equivalent to the total moving mass of the driver.
Raf is the horn radiation resistance and at high frequencies can be written..
Raf = (BL)^2 *St/Po*C*Sd^2
From the above in the electro acoustic model the value of Raf reduces as the ratio , St/Sd^2, (the throat area over the diaphram area squared), this reduces the total resistance value and increases fm.
The mass corner occurs at a frequency where the parallel combination of Rab, Raf, and Rvc, have the same resistance as the impedance of the capacitor equivalent to the total moving mass of the driver.
Raf is the horn radiation resistance and at high frequencies can be written..
Raf = (BL)^2 *St/Po*C*Sd^2
From the above in the electro acoustic model the value of Raf reduces as the ratio , St/Sd^2, (the throat area over the diaphram area squared), this reduces the total resistance value and increases fm.
Hello RCW
I appreciate your post.
But do you think that it would be a little clearer to all if you took the knowlege that you obviously have and explained it in a way that most everyone could understand?
It's one thing to quote a formula which you did very well and applied perfectly. It's quite another to explain exactly what you have posted to someone who does not understand the concepts involved.
A teachers toughest job is explaining a complex topic in terms that anyone can understand.
Mark
I appreciate your post.
But do you think that it would be a little clearer to all if you took the knowlege that you obviously have and explained it in a way that most everyone could understand?
It's one thing to quote a formula which you did very well and applied perfectly. It's quite another to explain exactly what you have posted to someone who does not understand the concepts involved.
A teachers toughest job is explaining a complex topic in terms that anyone can understand.
Mark
re formula
That post MWM was by way of reply to GM who enquired by what means mass corner increased with compression ratio.
GM himself quite often uses formula and numbers in his posts, so I considered that a reply of that sort was appropriate.
The explanation I gave is also about as simple as i know how to make it , and is a result that comes from classic work on electro acoustic analogue circuits by people like Beranek. Anybody who thinks that it is complicated should look at the explanation from the pure physics of the device before it is turned into a equivalent electrical circuit.
It is unfortunate that the subject of acoustics is one of the more difficult ones, and it took some of the best minds of nineteenth century science to explain it fully.
DIY audio is about acoustics, and in my opinion avoiding all mathematical explanation is not possible if a true, understanding is wanted, simplified word explanations are often simplified to the extent of error, or plain impossible to give with words without introducing large amounts of ambiguity.
That post MWM was by way of reply to GM who enquired by what means mass corner increased with compression ratio.
GM himself quite often uses formula and numbers in his posts, so I considered that a reply of that sort was appropriate.
The explanation I gave is also about as simple as i know how to make it , and is a result that comes from classic work on electro acoustic analogue circuits by people like Beranek. Anybody who thinks that it is complicated should look at the explanation from the pure physics of the device before it is turned into a equivalent electrical circuit.
It is unfortunate that the subject of acoustics is one of the more difficult ones, and it took some of the best minds of nineteenth century science to explain it fully.
DIY audio is about acoustics, and in my opinion avoiding all mathematical explanation is not possible if a true, understanding is wanted, simplified word explanations are often simplified to the extent of error, or plain impossible to give with words without introducing large amounts of ambiguity.
Hi Rcw,
you have my adulation. I often give up when a text arrives that is riddled with maths and complex equations. You obviously keep at it.
Having mastered the acoustics of horns, any chance you could write up your thoughts on selecting suitable (even optimum) speaker units and putting it in a horn WIKI?
you have my adulation. I often give up when a text arrives that is riddled with maths and complex equations. You obviously keep at it.
Having mastered the acoustics of horns, any chance you could write up your thoughts on selecting suitable (even optimum) speaker units and putting it in a horn WIKI?
re horns
I must admit Andrew that a masters in geophysics does help.
Leaches paper in section 7 deals with designing a system from specifications, in it you will find the details of how to derive the driver parameters that are optimum for a given design.
Basically you have to first define 7 parameters that you want, then see if a realisable driver is possible, I use a combination of the design from specifications, and design for a given driver to hone in on the ideal horn for a particular driver.
I must admit Andrew that a masters in geophysics does help.
Leaches paper in section 7 deals with designing a system from specifications, in it you will find the details of how to derive the driver parameters that are optimum for a given design.
Basically you have to first define 7 parameters that you want, then see if a realisable driver is possible, I use a combination of the design from specifications, and design for a given driver to hone in on the ideal horn for a particular driver.
To professor RCW
I may not have a masters degree in anything being largely self taught. But I have worked in design groups where none were the wiser. I tend to always try to understand the concept I have to apply in a holistic approach. Sometimes it takes a great deal of study. And I study untill I can explain it to anyone. Only then do I feel that I have a good grasp on the subject.
To apply horn theory to the real world takes more than a knowledge of the formulas. When you design horns in real life you find out that the formulas don't always describe what is happening. They that is the formulas are best guesses to predict what should happen. When reality and theory fail to meet it is usually a case in which the wrong theory was applied inapropriately to a design.
The statement asking for a clearer explanation was not a personal jab at you. Nor do I find the maths to complex. Although I must admit I have to clean off the dust and cobwebs in the back of my brain to do more complex math more often than I would like. You could probably run circles around me there
My only point is that there are some people reading these posts that do not need to be buried in JUST formulas. All formulas need a good primer and then they can be worked out by any determined person.
Mark
I may not have a masters degree in anything being largely self taught. But I have worked in design groups where none were the wiser. I tend to always try to understand the concept I have to apply in a holistic approach. Sometimes it takes a great deal of study. And I study untill I can explain it to anyone. Only then do I feel that I have a good grasp on the subject.
To apply horn theory to the real world takes more than a knowledge of the formulas. When you design horns in real life you find out that the formulas don't always describe what is happening. They that is the formulas are best guesses to predict what should happen. When reality and theory fail to meet it is usually a case in which the wrong theory was applied inapropriately to a design.
The statement asking for a clearer explanation was not a personal jab at you. Nor do I find the maths to complex. Although I must admit I have to clean off the dust and cobwebs in the back of my brain to do more complex math more often than I would like. You could probably run circles around me there
My only point is that there are some people reading these posts that do not need to be buried in JUST formulas. All formulas need a good primer and then they can be worked out by any determined person.
Mark
Speaking of visuals...
I too have looked at lots of horn designs, and this seems to me to be very "buildable".
It is really a box within a box within a box -- the outer two being flare extenders -- the inner being a pretty standard folded back horn.
Its sound is legendary and is allegedly down only 6db at 18hz
I too have looked at lots of horn designs, and this seems to me to be very "buildable".
It is really a box within a box within a box -- the outer two being flare extenders -- the inner being a pretty standard folded back horn.
Its sound is legendary and is allegedly down only 6db at 18hz
Attachments
re formula
I am a professor in its original sense MWM, since in this forum i have professed knowledge of a particular matter and provided proof, any one who can add to it or proove it untrue and subtitute his own better explanation then becomes the professor in his turn.
The point should be made that most of the horn theory one sees bandied about on the net is just reiteration of physics textbook stuff written, many years ago.
Most of these contain simplifying assumptions based upon teaching examples, "condsider an infinite exponential horn" being the typical, starting to chapters.
As soon as you depart from these idealised simplifying assumptions you enter a quagmire of numeric opproximation that for the most part is "ill posed", and beset with convergeance and rounding problems.
This is convienient for some because it leads to the assertion that horn design is therefore a black art, and it seems the the belief in some, that a particularly well cast spell gives rise to physical principles heretofore unheard of, hence giving horns the "mystical" dimension other types of loading lack.
I am a professor in its original sense MWM, since in this forum i have professed knowledge of a particular matter and provided proof, any one who can add to it or proove it untrue and subtitute his own better explanation then becomes the professor in his turn.
The point should be made that most of the horn theory one sees bandied about on the net is just reiteration of physics textbook stuff written, many years ago.
Most of these contain simplifying assumptions based upon teaching examples, "condsider an infinite exponential horn" being the typical, starting to chapters.
As soon as you depart from these idealised simplifying assumptions you enter a quagmire of numeric opproximation that for the most part is "ill posed", and beset with convergeance and rounding problems.
This is convienient for some because it leads to the assertion that horn design is therefore a black art, and it seems the the belief in some, that a particularly well cast spell gives rise to physical principles heretofore unheard of, hence giving horns the "mystical" dimension other types of loading lack.
AndrewT : There is a basshorn wiki,that Ive put some links to useful places online. If people have a link they should add it.
http://www.diyaudio.com/wiki/index.php?page=basshorn
http://www.diyaudio.com/wiki/index.php?page=basshorn
To RCW
The point should be made that most of the horn theory one sees bandied about on the net is just reiteration of physics textbook stuff written, many years ago.
Most of these contain simplifying assumptions based upon teaching examples, "condsider an infinite exponential horn" being the typical, starting to chapters.
As soon as you depart from these idealised simplifying assumptions you enter a quagmire of numeric opproximation that for the most part is "ill posed", and beset with convergeance and rounding problems.
This is convienient for some because it leads to the assertion that horn design is therefore a black art, and it seems the the belief in some, that a particularly well cast spell gives rise to physical principles heretofore unheard of, hence giving horns the "mystical" dimension other types of loading lack.
Let's clear one thing up. My name is Mark. Not Mwm.
To clear another thing up. I have read just about every paper available on the subject of horn design. I have access to a truly great technical library at the National Research Council here in Ottawa. The best papers I have in my personal library and turn to regularly.
I don't believe that horn design or most any loudspeaker design is a black art. I believe that it takes solid engineering to pull off a good design. I also have enough experience in the field to have seen that the papers and formulas are but theory as to what will happen under very particular circumstances. The best of which are fairly accurate but not infallable.
I have been and continue to be paid as a consultant in the loudspeaker industry. I've pulled off R&D including horns and driver systems. The design and construction ( by my own hands, not the engineering departments) of fullrange drivers with efficiencies above 105 db/meter. With frequency responses from 50 to 15khz. All from a 6 1/2" driver. Designed the phase plugs to!
If this all makes me a hack then so be it!
A basic tenant I have always held to is this:
That if I cannot explain something complex to a person with no technical background in plain english then I do not fully understand it.
Post what you want.
But be carefull that you don't hold your nose up so high that you drown in the shower!
Enjoy the posts.
Mark
P.S. I promise to play nice from now on.
The point should be made that most of the horn theory one sees bandied about on the net is just reiteration of physics textbook stuff written, many years ago.
Most of these contain simplifying assumptions based upon teaching examples, "condsider an infinite exponential horn" being the typical, starting to chapters.
As soon as you depart from these idealised simplifying assumptions you enter a quagmire of numeric opproximation that for the most part is "ill posed", and beset with convergeance and rounding problems.
This is convienient for some because it leads to the assertion that horn design is therefore a black art, and it seems the the belief in some, that a particularly well cast spell gives rise to physical principles heretofore unheard of, hence giving horns the "mystical" dimension other types of loading lack.
Let's clear one thing up. My name is Mark. Not Mwm.
To clear another thing up. I have read just about every paper available on the subject of horn design. I have access to a truly great technical library at the National Research Council here in Ottawa. The best papers I have in my personal library and turn to regularly.
I don't believe that horn design or most any loudspeaker design is a black art. I believe that it takes solid engineering to pull off a good design. I also have enough experience in the field to have seen that the papers and formulas are but theory as to what will happen under very particular circumstances. The best of which are fairly accurate but not infallable.
I have been and continue to be paid as a consultant in the loudspeaker industry. I've pulled off R&D including horns and driver systems. The design and construction ( by my own hands, not the engineering departments) of fullrange drivers with efficiencies above 105 db/meter. With frequency responses from 50 to 15khz. All from a 6 1/2" driver. Designed the phase plugs to!
If this all makes me a hack then so be it!
A basic tenant I have always held to is this:
That if I cannot explain something complex to a person with no technical background in plain english then I do not fully understand it.
Post what you want.
But be carefull that you don't hold your nose up so high that you drown in the shower!
Enjoy the posts.
Mark
P.S. I promise to play nice from now on.
Hi Qi,
is that a tannoy westminster you posted?
If so then I think the -6db is much higher than 18Hz.
The flare rate (don't know the symbol) is quoted as 0.9 from memory and this translates to about 30Hz - 35Hz. The horn length is truncated to about 12feet(3.5m) with the result that the mouth area is only about 5sqft (0.4sqm). It is intended for away from boundary location and so only gets floor loading rather than back wall or corner loading.
And yet I have seen it said that it sounds superb particularly the IMPACT of bass and it has no delay on mid and treble. Just a phase reversal to eliminate the crossover suckout.
is that a tannoy westminster you posted?
If so then I think the -6db is much higher than 18Hz.
The flare rate (don't know the symbol) is quoted as 0.9 from memory and this translates to about 30Hz - 35Hz. The horn length is truncated to about 12feet(3.5m) with the result that the mouth area is only about 5sqft (0.4sqm). It is intended for away from boundary location and so only gets floor loading rather than back wall or corner loading.
And yet I have seen it said that it sounds superb particularly the IMPACT of bass and it has no delay on mid and treble. Just a phase reversal to eliminate the crossover suckout.
Hi Andrew
Thank you for your post.
You are correct.
I agree -6db @ 18hz figure is "aggressive". It is from their website.
Some say it is an expanding pipe, not a "real" horn. Could that be it?
If a four-stack of labhorns will "only" get down to the mid-twenties (Tom Danley's own words), then something else is at work here for that figure to be true (heavy corner loading?).
All I know is...
I have heard it and loved it (there was a hint of colouration where the back horn acoustically crosses to the front horn -- a slight "hollowness").
It is a mature, proven design (Guy R. Fountaine is a legend, as you know)
It is smaller than a labhorn stack (it is approx 5' x 3' x 2')
Only one driver is required
The driver T/S parameters are well known (i. e., a less pricey substitute driver could be found as an option)
Built properly they are visually stunning (if you like "traditional")
Thank you for your post.
You are correct.
I agree -6db @ 18hz figure is "aggressive". It is from their website.
Some say it is an expanding pipe, not a "real" horn. Could that be it?
If a four-stack of labhorns will "only" get down to the mid-twenties (Tom Danley's own words), then something else is at work here for that figure to be true (heavy corner loading?).
All I know is...
I have heard it and loved it (there was a hint of colouration where the back horn acoustically crosses to the front horn -- a slight "hollowness").
It is a mature, proven design (Guy R. Fountaine is a legend, as you know)
It is smaller than a labhorn stack (it is approx 5' x 3' x 2')
Only one driver is required
The driver T/S parameters are well known (i. e., a less pricey substitute driver could be found as an option)
Built properly they are visually stunning (if you like "traditional")
Attachments
Hi,
The westminster is a totally different animal from a labhorn.
W is a full range hi quality domestic loudspeaker that will fill very large rooms (in fact it needs a large room to perform properly). L is a PA bass only (28Hz to 80Hz) designed for enormous power and when stacked can drive a large outdoor crowd to ecstacy (the legal kind).
W is a true horn in the triple sense:- Treble horn using the paper cone as a flare down to 1kHz, mid horn using the ply front wings from 300Hz to 1000Hz and back loaded horn from 30ishHz upto 300Hz.
There is no trickery involved just a carefully chosen set of compromises that give an overall performance that would be difficult to achieve in a smaller box with only 100W of drive.
The westminster is a totally different animal from a labhorn.
W is a full range hi quality domestic loudspeaker that will fill very large rooms (in fact it needs a large room to perform properly). L is a PA bass only (28Hz to 80Hz) designed for enormous power and when stacked can drive a large outdoor crowd to ecstacy (the legal kind).
W is a true horn in the triple sense:- Treble horn using the paper cone as a flare down to 1kHz, mid horn using the ply front wings from 300Hz to 1000Hz and back loaded horn from 30ishHz upto 300Hz.
There is no trickery involved just a carefully chosen set of compromises that give an overall performance that would be difficult to achieve in a smaller box with only 100W of drive.
Labhorn vs Westminster
Hi,
depends on what you are trying to achieve.
The Westminster is compromised even though overall it performs well and in a few respects very well cf. a vented cabinet.
The advantage of the labhorn is that it will go down lower if you extend the mouth or stack them. The larger mouth and similar flare rate will have reduced the ripple compared to the Westminster. When driven with low power they should have lower distortion and have the potential to easily handle peaks. They also save driving the main speakers with low bass allowing the mid/bass to perform better.
For a low bass speaker you can improve on both designs choosing the compromises that suit best your circumstances but anything deeper WILL require a bigger box/mouth and lower flare rate. What those two designs show is that some deep bass can be achieved even with ripple and drooping response with seriously curtailed length and reduced mouth size.
Hi,
depends on what you are trying to achieve.
The Westminster is compromised even though overall it performs well and in a few respects very well cf. a vented cabinet.
The advantage of the labhorn is that it will go down lower if you extend the mouth or stack them. The larger mouth and similar flare rate will have reduced the ripple compared to the Westminster. When driven with low power they should have lower distortion and have the potential to easily handle peaks. They also save driving the main speakers with low bass allowing the mid/bass to perform better.
For a low bass speaker you can improve on both designs choosing the compromises that suit best your circumstances but anything deeper WILL require a bigger box/mouth and lower flare rate. What those two designs show is that some deep bass can be achieved even with ripple and drooping response with seriously curtailed length and reduced mouth size.
AndrewT
But at what additional cost and effort?
For example, here is an outstanding example of DIY craftsmanship -- design concept, build quality, testing methodology, documentation, etc.)...
http://www.geocities.com/hulkss
It utilizes two LABHORNs with mouth extension.
According to the extensive testing on the web page it has an F3 of 30hz, and an F10 of 20hz in room (and it is HUGE).
I personally would still go with a DIY Westminster...
Using one driver not two. it is cheaper, smaller, better looking (IMO), and with greater bass extension (unless you are saying TANNOY is misstating its numbers of -6db @ 18hz)
I also find it interesting that Tom Danley's new "hot creation" is his TOWER OF POWER -- an 18" x 18" x 84" "tapped horn" tower (looks suspiciously like a TLINE to me, but WTFDIK)
If I were going the two LABHORN route I would modify the throat to accept one driver only, and vent the driver to a triple fold TLINE for the bottom octave (15hz tuning) -- OR, since it is the bottom-most octave (where the ear is most forgiving), a simple EBS should work just fine.
Artist concept (work in progress) ...
But at what additional cost and effort?
For example, here is an outstanding example of DIY craftsmanship -- design concept, build quality, testing methodology, documentation, etc.)...
http://www.geocities.com/hulkss
It utilizes two LABHORNs with mouth extension.
According to the extensive testing on the web page it has an F3 of 30hz, and an F10 of 20hz in room (and it is HUGE).
I personally would still go with a DIY Westminster...
Using one driver not two. it is cheaper, smaller, better looking (IMO), and with greater bass extension (unless you are saying TANNOY is misstating its numbers of -6db @ 18hz)
I also find it interesting that Tom Danley's new "hot creation" is his TOWER OF POWER -- an 18" x 18" x 84" "tapped horn" tower (looks suspiciously like a TLINE to me, but WTFDIK)
If I were going the two LABHORN route I would modify the throat to accept one driver only, and vent the driver to a triple fold TLINE for the bottom octave (15hz tuning) -- OR, since it is the bottom-most octave (where the ear is most forgiving), a simple EBS should work just fine.
Artist concept (work in progress) ...
Attachments
Hi,
I don't doubt your choice of the Westminster over a multi box and multi amp array. Particularly since you would be buying a professionally designed and tested speaker system that is guaranteed to meet specification and sound good to boot.
I fell in love with the Westminster the first time I read about it and saw the pics. But at what a cost. I just could not contemplate it then nor now. The last time I saw a price quoted it was over £13,000.00 per pair. How many labhorns and amps could you buy for that?
I will have to settle for much less but having had Tannoy Berkleys for nearly 30years and got used to the easy power delivery (although missing extreme low end extension). I do look forward to building and developing my proposed sub-bass horn using Tannoy drivers (all hidden in and dominating the loft)
However I digress, the main point I am trying to make is that it seems possible to make compromises in the design and implimentation of horns and still end up with adequate or somethings excellent performance. These compromises should be extendable to lower frequencies to allow true 20Hz or sub-bass performance to be achieved if we can get the balance right.
This thread and a similar one running concurrently may help achieve that balance.
BTW I looked at hulkss some time ago (a previous web page) and thought he had gone to a lot of work to lose both back wall and corner loading and still achieve a tiny increase in mouth size.
I don't doubt your choice of the Westminster over a multi box and multi amp array. Particularly since you would be buying a professionally designed and tested speaker system that is guaranteed to meet specification and sound good to boot.
I fell in love with the Westminster the first time I read about it and saw the pics. But at what a cost. I just could not contemplate it then nor now. The last time I saw a price quoted it was over £13,000.00 per pair. How many labhorns and amps could you buy for that?
I will have to settle for much less but having had Tannoy Berkleys for nearly 30years and got used to the easy power delivery (although missing extreme low end extension). I do look forward to building and developing my proposed sub-bass horn using Tannoy drivers (all hidden in and dominating the loft)
However I digress, the main point I am trying to make is that it seems possible to make compromises in the design and implimentation of horns and still end up with adequate or somethings excellent performance. These compromises should be extendable to lower frequencies to allow true 20Hz or sub-bass performance to be achieved if we can get the balance right.
This thread and a similar one running concurrently may help achieve that balance.
BTW I looked at hulkss some time ago (a previous web page) and thought he had gone to a lot of work to lose both back wall and corner loading and still achieve a tiny increase in mouth size.
AndrewT
Stated eloquently.
My quest, however, is to reverse-engineer and DIY build the Westminster
It has been done before (by MR GREEN of Bangladesh, a fine gentleman I am told).
It can be done again.
Also, I have read (source: MAGNETAR and others) that ideally the front horn should REALLY start as low as 80hz, not 200hz -- for articulation and detail.
This is one of the first tweaks I would look into (assuming the -6db @ 18hz is "real")...
Stated eloquently.
My quest, however, is to reverse-engineer and DIY build the Westminster
It has been done before (by MR GREEN of Bangladesh, a fine gentleman I am told).
It can be done again.
Also, I have read (source: MAGNETAR and others) that ideally the front horn should REALLY start as low as 80hz, not 200hz -- for articulation and detail.
This is one of the first tweaks I would look into (assuming the -6db @ 18hz is "real")...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.