jessie.dazzle wrote:

Incidentally, a little motivational experiment was recently made possible; with half a horn complete and laying flat, the missing half substituted by the floor, I had my "assistant" (who has quite a low voice for a female)….

“Incidentally, a little motivational experiment was recently made possible; with half of my "assistant" (who has quite a low voice for a female) lying flat and with missing half substituted by the floor….”

Anyhow, the large horn is large fun if they are properly made. I found it very useful to have driver inhaled into horn to run it without any crossover for a while to listen it and get familiar with sound. There is the only one thing that is more fun then a properly made large horn – the properly made large horn installed in an “active spot” of a room.

BTW, Jessie, if you were outsourcing the job of making your 40Hz horn then what price you feel would  be reasonable to pay for a pair?

Dominic wrote:

be careful here as mouth size is defined not by what you input, so much as the acoustic space and performance you want. The throat size can be fiddled with if you're careful but there's not much one can do to shrink the mouth. On a 'bass' horn you can lop off some of the final curve, because diffraction isn't a big problem at lower frequencies, but you change other things that way. You certainly can't change the mouth size by using the output of the back side of the diaphragm.

Dominic, yes and no. You are right - the diaphragm’s dumping is not something that affects mouth size but in some indict way it… does.

Let pretend that a horn has 50Hz rate and a driver with loaded resonance frequency of 40Hz. By minimization of back chambers it is possible to proximate the driver’s resonance to the horn rate and it will give substantial boost in horn equalization. So, if you have +2dB at 50Hz then would it possible to make the horn’s mouth not to be 50Hz but rather 55Hz? The difference in size will be a foot or two – I mean a lot. The bigger question would be if the bass reproduced by resonances would be the same as the bass reproduced by mouth size? I do not know the answer and I do not know that anyone knows certainly. There is too many “contingent upon” unloved.

Also, the cheating with mouth is another controversial subject. Certainly no one wish to cheat but in some case I have seen that small horn with ridiculously small mouth output OK bass. A good examples The Bruce Edgar’s Refrigerator bass module. Very lightly and cheaply built, electronically equalized, with underside mouth and reported response down to 20Hz. Ridicules, yes it is it but somehow it does not sound bad…. Could is be better if it was not cheated? I am sure it would. However, where is the balance between the efforts and benefiter with bass horns? No one knows…

Romy the Cat wrote:

Dresden wrote: … One very important component I'm leaving out of the cost of the horn is amplification (the horns will be active, using class-D amps).  The reason for my choosing class-D amplification is that the modules and various components for building what I consider very capable amplifiers can be purchased at low cost and assembled by me (again, the mantra is to save money for the purpose of appropriating it toward the casting of the horn mouth, said cost as of this date undetermined).  I have found two manufacturers which offer class-D amplification at reasonable costs, said amplification capable of delivering the target power and sustainable performance (one is located in Germany, the other in England). I see absolutely no rational to go for class-D amplification on bass horn. Leaving inside all alleged imperfections of class-D amplification’s Sound the only advantage that class-D amplification has is cost, size, heat generation and power. Yes, you can buy for $40 a module that will be cold-running and output 200-400W with 95% efficiency but the bigger question: do you need it? The JBL driver that you selected is 95dB sensitivity (would like to see more but it is me). Using it as a compression driver will give you extra 2-3dB sensitivity; the horn’s equalization will give you 6-7dB. So, we are will be arriving to ~103dB of sensitivity. A proper horn positioning might give you an extra 6dB, let say 2db from the room’s gain to make the number even. So, we are talking about 105dB. Even if you have a large room of 1500 sq feet then with 10W of amplification you will be able to develop sound pressure enough to make you deaf. So, why would you need a powerful amp in there, particularly the class-D amp? As single ended SS or a chip amp for 10-20W will do fine and might cost very much the same or negligibly more. You might look at the many high-quality amp kits available from some high-end oriented companies; some of them might be good. I think that you shell be able to find a prebuilt kit for under $100-$150 (retail) that would have a good SS single-ended amp, two stages amp of 20W. it is what I would be looking if I go for an “active” bass horn. The caT

Romy wrote :
"...if you outsource the job of making your 40Hz horn then what price you feel would  be reasonable to pay for the pair?..."

I will take the question to mean the price it might cost to pay someone to make similar horns (similar mass and rigidity; round section throat progressing to a rectangular mouth, which requires a mold).

It would be best to find someone who has never done such a thing, as he might agree to take on the work for, I don't know, $20 to $30k... However, the price for an additional pair would be double the price of the first pair, as the guy will have wised up by then!

I am going about this in a sort of one-off way. If I were planning to make several pairs, I would have used a less labor-intensive process; there would be less torture involved, and the theoretical price might be less... Knowing what's involved, I can't imagine anyone accepting such a job for anything like what we might consider a reasonable amount to pay for mid-bass horns.

Look at materials cost for the horns (meaning without taking into account labor or the cost of materials for the mold) :

Each horn flare uses 900 lbs of raw material, for a total of 5000€
This is for the raw flare, and does not include any exterior finisher or "WAF cover" (while the horns have a smooth interior, the exterior is quite "rustic", with a lot of deep bracing, looking something like the web of a spider who eats only waffles and looks only at the Eiffel tower)

To that I would estimate to have spent another 1000€ (because I did not skimp) for the back chambers and associated parts (8 x 28" diameter discs cut from 30mm thick hard plywood, 24" diameter sewer pipe with 5/8" wall, serious wheels, boxes of large bolts and a bunch of other hardware).

So I am up to about 6000€ in materials before considering labor costs, and we haven't even considered paying for a mold.

I am doing it in a way that a professional fabricator would most likely not consider kosher; if out-sourced, the job would be done differently, involving less man hours, but would probably end up costing as much as a pair of small custom boat hulls, as the process would likely be similar (serious molds followed by hand lamination or possibly a nasty chopper-gun).

I use non-toxic materials, which is good, because I have been at it evenings and weekends for like 3 months now, and am finally to the point of "pulling parts"... Working seriously (not the case lately) it takes me around a month to get half a horn to a sort of rough state, which I then set aside. Because I do not enjoy work that involves repeating a process, I then embark immediately on a week-long bender, slowly coaxing myself back to the workshop. Once all parts are to this rough stage, there will be a bit of finish work to do, making sure everything mates correctly. Then fabrication of rear chambers, painting and final assembly.

I may or may not make WAF covers for the exteriors (they could be added later).

I will post photos at some point.

Dresden wrote:

hmm...I didn't realise I had left my browser logged-in to your site (I left my PC on over night, downloading some files). '..the only advantage that class-D amplification has is cost, size, heat generation and power.' In my eyes, that's more than I could ever have hoped for in the present price range. I've had the pleasure to listen to some high-end amplifiers, utilized mostly with ribbon loudspeakers.  (I still prefer Bryston over most any other amplifier, when taking into account build quality, warranty, looks, and of course sound.)  But in terms of cost, the modules I've found are very promising. I intend to power the drivers to no more than 33% of their rated power capacity ([200W], AES total power capacity being 600W continuous pink noise), particularly to keep distortion ultra-low and driver power compression at or under the 2dB level. The purpose for wanting to implement class-D amplification is for use in small theatrical performances or musical venues, not for personal use (think an auditorium, small stage or music hall).  Of course, should a person have a home that could justify actually using such capacity, that would be a sight to see--and hear--in person. For personal use, yes, 20W may prove more than effective.

Dresden,

My idea to “talk” about horns implies visualization or possible pursuing of specific sonic objectives. I hope that “Sound” is always the subject of any posts at this site: it might render itself as the thoughts about nuts and bolts of grid biasing, the size of back chambers or the VTA setting. I do not particularly care about non-applied talks about audio,  the talks about audio while being blind of ignorant about results or demonstration of capacity to recognize and to use results. There are many communities (like DiyAudio.com for instance and many others) that might explore all imaginary subjects from many directions, done mostly by the idiots who have no sense of sound recognition, no well-structured sonic objectives and very superficial  and shallow appreciation of the actual sonic output of their actions. I would like do not convert my site into the DiyAudio.com type of idiocy and I hope that people who have inters in my site actually think first about own interests in sound and second about the way to get there.

To say honestly I do not understand what you are trying to do and some of the things you say does not compile in my mind as something that makes sense. You need to understand my limitation in the subject – I think about playback as complete result. I might abstract out of the “complete result” a specific characteristic of sound and look in this deeper, deconstructioning sound but  I tend do not glue sound from the multitude of accidentals micro-results. Why I go over all of it in the given moment? Because I feel that thinking, designing and talking about midbass horn is possible only in context of larger view of playback installation. To think just about midbass horn without thinking about everything else is like making a surgery on kidney without caring about the rest of the body.

I do understand that you would like to build a high quality 40Hz horn, good for sound reinforcement application and good for home use. But this objective sounds as oxymoronic to me as the objective to making a screwdriver that would take apart a precision Swiss watch and at the same time to be a useful to disassemble the Golden Gates Bridge. I mean the objectives and the means for sound re-enforcement tasks and the home use are so different that I hardly feel that it is possible to think about both of them and to use the same vocabulary.  I might be wrong but it is how I see the things and my explosion to what “out there” prove to me that I am not very far from what it is.

jessie.dazzle wrote:

Romy wrote : "...if you outsource the job of making your 40Hz horn then what price you feel would  be reasonable to pay for the pair?..." I will take the question to mean the price it might cost to pay someone to make similar horns (similar mass and rigidity; round section throat progressing to a rectangular mouth, which requires a mold). It would be best to find someone who has never done such a thing, as he might agree to take on the work for, I don't know, $20 to $30k... However, the price for an additional pair would be double the price of the first pair, as the guy will have wised up by then! I am going about this in a sort of one-off way. If I were planning to make several pairs, I would have used a less labor-intensive process; there would be less torture involved, and the theoretical price might be less... Knowing what's involved, I can't imagine anyone accepting such a job for anything like what we might consider a reasonable amount to pay for mid-bass horns. Look at materials cost for the horns (meaning without taking into account labor or the cost of materials for the mold) : Each horn flare uses 900 lbs of raw material, for a total of 5000€ This is for the raw flare, and does not include any exterior finisher or "WAF cover" (while the horns have a smooth interior, the exterior is quite "rustic", with a lot of deep bracing, looking something like the web of a spider who eats only waffles and looks only at the Eiffel tower) To that I would estimate to have spent another 1000€ (because I did not skimp) for the back chambers and associated parts (8 x 28" diameter discs cut from 30mm thick hard plywood, 24" diameter sewer pipe with 5/8" wall, serious wheels, boxes of large bolts and a bunch of other hardware). So I am up to about 6000€ in materials before considering labor costs, and we haven't even considered paying for a mold. I am doing it in a way that a professional fabricator would most likely not consider kosher; if out-sourced, the job would be done differently, involving less man hours, but would probably end up costing as much as a pair of small custom boat hulls, as the process would likely be similar (serious molds followed by hand lamination or possibly a nasty chopper-gun). I use non-toxic materials, which is good, because I have been at it evenings and weekends for like 3 months now, and am finally to the point of "pulling parts"... Working seriously (not the case lately) it takes me around a month to get half a horn to a sort of rough state, which I then set aside. Because I do not enjoy work that involves repeating a process, I then embark immediately on a week-long bender, slowly coaxing myself back to the workshop. Once all parts are to this rough stage, there will be a bit of finish work to do, making sure everything mates correctly. Then fabrication of rear chambers, painting and final assembly. I may or may not make WAF covers for the exteriors (they could be added later). I will post photos at some point. jd*

serenechaos wrote:

Dresden, I'm confused--  What is the target low knee? Upper knee? What is the flare rate?    Expansion profile? (or T factor -- Hypex, Exponential Tractix, etc). And you want to use one 12" driver?  or two in parallel? Or something different? (I didn't understand that part).   Are you setting the throat as a function of compression ratio, or ???   And the length as a function of mouth size?   Or wave length (or quarter-wave)?   And the bends; are you building a J horn?  Or something else?   I'm having trouble picturing this, and still not clear on what frequency range you're trying to run it in.   (And still wondering if you're tryng to build something that two horns would do a lot easier).  Robert

There are more efficient drivers available, if that matters.  As Romy pointed out, usually very different systems are used in PA and in homes.  I thought you were talking about a Front Loaded Horn, not a Compound horn. 
"using the acoustic energy from both the front and rear of the driver in a horn loaded fashion." as you put it.  

Yes, they have been built, e.g. Tannoy's Westminster & Autograph, Lowther's TP1, etc. 
Sound is a matter of opinion, and taste... 
I've experimented with them, very difficult to implement, and to balance the front and rear wave, much time-align... 
I felt it was a dead end, and is why I'm now building a five-way FLH system. 
YMMV, good luck! 
Robert

serenechaos wrote:

There are more efficient drivers available, if that matters.  As Romy pointed out, usually very different systems are used in PA and in homes.  I thought you were talking about a Front Loaded Horn, not a Compound horn.  "using the acoustic energy from both the front and rear of the driver in a horn loaded fashion." as you put it.   Yes, they have been built, e.g. Tannoy's Westminster & Autograph, Lowther's TP1, etc.  Sound is a matter of opinion, and taste...  I've experimented with them, very difficult to implement, and to balance the front and rear wave, much time-align...  I felt it was a dead end, and is why I'm now building a five-way FLH system.  YMMV, good luck!  Robert

Romy the Cat wrote:

Dresden wrote: hmm...I didn't realise I had left my browser logged-in to your site (I left my PC on over night, downloading some files). '..the only advantage that class-D amplification has is cost, size, heat generation and power.' In my eyes, that's more than I could ever have hoped for in the present price range. I've had the pleasure to listen to some high-end amplifiers, utilized mostly with ribbon loudspeakers.  (I still prefer Bryston over most any other amplifier, when taking into account build quality, warranty, looks, and of course sound.)  But in terms of cost, the modules I've found are very promising. I intend to power the drivers to no more than 33% of their rated power capacity ([200W], AES total power capacity being 600W continuous pink noise), particularly to keep distortion ultra-low and driver power compression at or under the 2dB level. The purpose for wanting to implement class-D amplification is for use in small theatrical performances or musical venues, not for personal use (think an auditorium, small stage or music hall).  Of course, should a person have a home that could justify actually using such capacity, that would be a sight to see--and hear--in person. For personal use, yes, 20W may prove more than effective. Dresden, My idea to “talk” about horns implies visualization or possible pursuing of specific sonic objectives. I hope that “Sound” is always the subject of any posts at this site: it might render itself as the thoughts about nuts and bolts of grid biasing, the size of back chambers or the VTA setting. I do not particularly care about non-applied talks about audio,  the talks about audio while being blind of ignorant about results or demonstration of capacity to recognize and to use results. There are many communities (like DiyAudio.com for instance and many others) that might explore all imaginary subjects from many directions, done mostly by the idiots who have no sense of sound recognition, no well-structured sonic objectives and very superficial  and shallow appreciation of the actual sonic output of their actions. I would like do not convert my site into the DiyAudio.com type of idiocy and I hope that people who have inters in my site actually think first about own interests in sound and second about the way to get there. To say honestly I do not understand what you are trying to do and some of the things you say does not compile in my mind as something that makes sense. You need to understand my limitation in the subject – I think about playback as complete result. I might abstract out of the “complete result” a specific characteristic of sound and look in this deeper, deconstructioning sound but  I tend do not glue sound from the multitude of accidentals micro-results. Why I go over all of it in the given moment? Because I feel that thinking, designing and talking about midbass horn is possible only in context of larger view of playback installation. To think just about midbass horn without thinking about everything else is like making a surgery on kidney without caring about the rest of the body. I do understand that you would like to build a high quality 40Hz horn, good for sound reinforcement application and good for home use. But this objective sounds as oxymoronic to me as the objective to making a screwdriver that would take apart a precision Swiss watch and at the same time to be a useful to disassemble the Golden Gates Bridge. I mean the objectives and the means for sound re-enforcement tasks and the home use are so different that I hardly feel that it is possible to think about both of them and to use the same vocabulary.  I might be wrong but it is how I see the things and my explosion to what “out there” prove to me that I am not very far from what it is. The caT

Yes, too low efficiency, even worse than Altec 515, (when loaded with small throat, in proper FLH, NOT A7 type "horn" which disqualified it also for my usage... 
I don't know how "colored" Tannoy would sound with properly designed horn though... 
Seperate amps could take care of lack of efficiency compared to the rest of the system after everything else was dialed in. 
I would still like to try 15" Tannoy Red or Silver (Gold is lower quality?) in 65Hz horn, (and am building horn with capabilitys for this trial) running from ~ 80Hz to ~400Hz, but will need to be AFTER five-way horns are built, and DSET amps are built, and working (as the Tannoys are less efficient). 
Might be able to build "resonating oops" and mid-bass in same channel. 

I don't know if this is what Dresden is thinking in this thread of not; I'm still not clear on his design / goal. 

Perhaps it's something like this: http://cgi.ebay.com/Pr-Tannoy-15-Monitor-Red-Autograph-Speakers-Huge-Sound_W0QQitemZ190266415283QQcmdZViewItemQQptZUK_AudioVideoElectronics_HomeAudioHiFi_HiFiSpeakers?hash=item190266415283&_trksid=p3286.m63.l1177

Dresden wrote:

I've concluded that building at least two--and perhaps three--different versions of a Mid/Upper bass horn design will be required to determine which of the three configurations perform best.

Unfortunately it is not so simple. Even if you built three different versions of an upperbass horn (with is a crazy things to do but a commendable experiment anyhow) then it would hardly indicate which configuration “performs best”. There are 3 things that I would like to point your attention

1)    The sound of your upperbass horn will be 60% depending from the way in which it imbibed into your room.

2)    The sound of your upperbass horn will be 30% depending from the way in which the GIVEN upperbass integrated with rest of the channels

3)    If you go went the pain to read many post of this site then you will see that I very seldom, if ever, give a direct recommendation what to do. I know that it pisses a lot of simplistic audio-idiots out there but there a lot of reasons for me to do what I do. My “homework” to you, as to a person who would like make commercial upperbass horns: what do you think the relation of this third paragraph with the context of this thread? Mind you that it very loaded question.

I like the title of you post” The Purpose and Approach”. This in many ways is the answer to the idea of perfect loading, or the perfect loudspeaker, or whatever else is “perfect”. This view kind of subside my excitement about the “generic” commercial projects and one of the major ingredients – “the purpose” is not plugged in the recipe of the cooking….

Romy the Cat wrote:

Dresden wrote: I've concluded that building at least two--and perhaps three--different versions of a Mid/Upper bass horn design will be required to determine which of the three configurations perform best. Unfortunately it is not so simple. Even if you built three different versions of an upperbass horn (with is a crazy things to do but a commendable experiment anyhow) then it would hardly indicate which configuration “performs best”. There are 3 things that I would like to point your attention 1)    The sound of your upperbass horn will be 60% depending from the way in which it imbibed into your room. 2)    The sound of your upperbass horn will be 30% depending from the way in which the GIVEN upperbass integrated with rest of the channels 3)    If you go went the pain to read many post of this site then you will see that I very seldom, if ever, give a direct recommendation what to do. I know that it pisses a lot of simplistic audio-idiots out there but there a lot of reasons for me to do what I do. My “homework” to you, as to a person who would like make commercial upperbass horns: what do you think the relation of this third paragraph with the context of this thread? Mind you that it very loaded question. I like the title of you post” The Purpose and Approach”. This in many ways is the answer to the idea of perfect loading, or the perfect loudspeaker, or whatever else is “perfect”. This view kind of subside my excitement about the “generic” commercial projects and one of the major ingredients – “the purpose” is not plugged in the recipe of the cooking…. Rgs, Romy the Cat

Dresden,

So the first two could actually be just one actual build, with alternate rear chambers? 
Wouldn't you change the throat size, as well as the compression chamber size? 
Then arrive at your "optimized" compound horn design.

Then you could compare this to design #3 which would be a straight FLH, correct? 
This may be the best way to do it, to hear the difference, to "prove it to yourself" rather than the suggestion Romy made about the third paragraph. 
I had to go through all that mess, and learn the hard way... 
I really thought the compound horn design was a good idea @ one time too... 
Robert