Romy the Cat wrote:

You need to decide what length of the horn you can afford. When I mean “afford” I ment the position of the horn in context of the rest of your system. You know the lowest cut off - 40Hz. So, the most suitable for you length and the mouth size will give you the throat diameter. If you have unlimited space in your room then be advised that starting form some point the increase of length and minimization of the throat will increase loading but also will introduces some unwanted colorations. You see, the longer horn is them more “parallel” it is. A horn that we use for audio have very slow opening at beginning and in very long horn the “beginning of the horn” section is very long, it might be a foot or two of virtually parallel walls. For the frequencies that the 40Hz horn will be caring the “virtually parallel walls” are the essentially the parallel walls.  I have no idea when it becomes a factor but too long horns tend to be congested and colored. So, you have a horn, you have a throat diameter, then you need to find a driver. To decide on a driver is very complicated ceremony and my absolute rule is following in it: “It is absolutely imposable to predict with a serenity how a driver will sound after it will be loaded in a given horn.” You might do for compression driver, or for conventional driver, in fact any driver that you will be using with back chamber will become a compression driver.   The section of driver is a big subject… Linearity is not something that I would even care; do not think about it as you have no control over it anyhow. I laugh when people talk about linearization of bass horn frequency response. Where are you? A well-sounding 40Hz horn is very interning accomplishment to experience. If you are near US’ New England and if you listen serious music then I would like to be invited after you finish the projects. Rgs, the Cat

Romy the Cat wrote:

Yes, the Dresden’s talk about 40Hz horn and 90Hz horn as the similar horns, particularly if he does not want to "cheat", stroked me as odd too. 90Hz horn is a nice a manageable 40” piece of furniture. The 40Hz is the monster in a house and a good reason to divorce for some women. Also, it VERY hard to differentiate between the “accurate, smooth, full-bodied sound” at 40Hz and 90Hz as at those frequencies the location of the horns (The Macro-Imbedding) and the construction of the horn become too important. I ran 125Hz horn and am getting out it 95Hz in “hot spot” (not the best way to do the thing BTW), so God knows what Dresden will get with a hole 4 time larger. Still, unquestionably the 40Hz is WAY more powerful weapon to fight for good sound. I also do not at ease with notion that the low-passing of long horn is too bad. It is most likely Dresden’s will have a MF channel at 500-600Hz that will decay very fast. Still most of the bass drivers in a straight horn will shoot with excessive HF and the low-pass of a long horn will be good remedy against using a high order low-path crossover on bass channel. The Cat

serenechaos wrote:

There's a big difference in 40 - 400 and 90 - 400 Hz.  40 - 400 might also be stretching the bandwidth which will be horn loaded?  (FLHs by nature are narrow band, 40 - 400 is over three octaves...) And, besides the coloration Romy mentioned, a very long horn will act as an acoustic low-pass filter.  Integration.  I mean all drivers having the "same type voice."  I don't know what you plan below 40 or above 400, but they need to have the same general "Sound."  Or you can end up with something that sounds like so many good drivers playing, instead of one integrated "Sound."  Just a few of the problems I've been dealing with in building a 65 Hz mid bass horn.  Which is MUCH smaller than 40 Hz.  But is easy to integrate with a tapped horn from 25 Hz up to where it comes on.   Something that would hit 40Hz does sound like an interesting challange...  Robert

1)      If you decided to use the 12” JBL 2206H driver then I doubt  that you might talk about 4” throat. A 12” driver with wide outer suspension might go with 7”-8” throat. The 6” might do, though it might be a stretch. The 4” I think it too much.

2)      With 40Hz cutoff of non-rapid Tractrix opening (that most like you will use) and 4” throat you no way will end up with 7'6" horn’s length. I have no way now to look at the right number but how I “feel” is you shell be arriving under 8’ of length and 40Hz cutoff with 8” throat. With 4” throat you will be looking at 12” or so…

3)      If you planning to move next year then it does make send to stats he constriction at the new place. You will take used consideration the idiosyncrasies of the new real-estate, room layout, and the recourses of the local subcontractors. With properly-made mass-loaded 40Hz it might be important.

4)      So, the 3-Way system. 40-400, 500-10K and up most likely. It might do. I personally like the “fundamental” channel that allow MF driver to run free. If you have a good MF driver that cans confidants, linearly and with good quality to all the way down to 500Hz then it is very good.

5)      Your MF channel is very much directional and need be at conventional distance from floor.  Your 40Hz will have a mouth let say 6x4 feet that is very unconventional and will not be sitting next to the MF channels. So, you most likely will hang it above or place them on the sides. The 400Hz of first order it relatively directional signal, so be reaper that the 40Hz will suck imaging out MF channel. Pay attention what Macondo does. It has a small “local” 100Hz horn that cares the “location” of lower MF and ground it to the necessary spot. In this configuration the location of lower frequency channels become less important. Jessie for his Project used the similar configuration and pay attention how offensive he was planning to go – he plans to put his 40Hz horn in other side of listing position…. and who know – it might work and his upper bass horn hold the right location of  fairly directional lower mid range.  There are a lot of moments like this in horn practice.

6)      Rane active crossovers in my view are very sub acceptable, particularly in bass,  but it is me… what we are taking about bass then it is very difficult to go with active devise….

7)      If you have an idea how to make the 40Hz horn visually pleasing then it might be very interesting. I truly would like to see how it will turn out to be. I will do my 40Hz horn if I decide to move, so any ideas of make 40Hz with “humane face” sound very practical to me. Alternately you might go not for 40Hz but for 25Hz and instead of moving to North Carolina you could move into your new 25Hz horn. :-)

8)      If you planning to make the 40Hz horn commercially available than what you feel might be the conditions? Jeffery (from Indiana?) does 40Hz for GOTO driver and the last time he showed up at this site he was looking at $15K for the job. It sounds like here and there reasonable.  Is any specific price target that you have in your mind. I do not ask how much it will cost but rather what you feel is the prices that make you worth to do it. The reason I ask is that if I go for the similar project then I would like to know where the threshold is after (or before) which it makes sense do not do it myself but to outsource it.

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.

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