Romy the Cat wrote:

The view is from the  mouth of the right horn.

Last night I was playing with my ¾” Baltic Birch. What I realized is that my Jew frugality played a bad joke on me.  At this point I do feel that ¾” of plywood is not enough thickness for my 43.5Hz horn. I understand that it will be heavily braced, perhaps each 8 inch but still I do not like it p I would like more substance in the horn skin. If course not only the Jew frugality and my desire to buy less plywood made me to decide for ¾ inch. The weight was a big consideration factor and the fact that 1.5inch wall for instance will minimize the operational, useful volume of my horn’s mouth. Anyhow, now after hours of dealing with ¾” Baltic Birch I do feel that it was a mistake – I need a thicker walls.

Now is the question what can I do? This is complicated as the math for the ¾” is doe and we are pretty much ready to cut the wood. If I glue two of ¾ layers then it will be twice heavier, still I wonder if it makes sense for me to go for it. I have some alternatives that I am weighing now.

1)      Each section between the brace to feel with mixture of send and roofing contrite.  The roofing contrite is tar-like plastic that is wonderful dampening. I might even drop into the roofing contrite some lead shots (I have 800 pounds)

2)      To make colossal amount of bracing, pretty much to built a second layer with 2 x4 that will sit behind the plywood on screws and polyurethane glue.

3)      Discover if exists some kind of heavy-mass construction spray-adhesive (foam) and to damp that foam (perhaps mixing it with sand) into the section between the 2x4

4)      Forget the frugality and reasoning and to glue second layer of plywood to my current 3/4 plywood

I have all options on the table now…

Romy the Cat wrote:

Last night I was playing with my ¾” Baltic Birch. What I realized is that my Jew frugality played a bad joke on me.  At this point I do feel that ¾” of plywood is not enough thickness for my 43.5Hz horn. I understand that it will be heavily braced, perhaps each 8 inch but still I do not like it p I would like more substance in the horn skin. If course not only the Jew frugality and my desire to buy less plywood made me to decide for ¾ inch. The weight was a big consideration factor and the fact that 1.5inch wall for instance will minimize the operational, useful volume of my horn’s mouth. Anyhow, now after hours of dealing with ¾” Baltic Birch I do feel that it was a mistake – I need a thicker walls. Now is the question what can I do? This is complicated as the math for the ¾” is doe and we are pretty much ready to cut the wood. If I glue two of ¾ layers then it will be twice heavier, still I wonder if it makes sense for me to go for it. I have some alternatives that I am weighing now. 1)      Each section between the brace to feel with mixture of send and roofing contrite.  The roofing contrite is tar-like plastic that is wonderful dampening. I might even drop into the roofing contrite some lead shots (I have 800 pounds) 2)      To make colossal amount of bracing, pretty much to built a second layer with 2 x4 that will sit behind the plywood on screws and polyurethane glue. 3)      Discover if exists some kind of heavy-mass construction spray-adhesive (foam) and to damp that foam (perhaps mixing it with sand) into the section between the 2x4 4)      Forget the frugality and reasoning and to glue second layer of plywood to my current 3/4 plywood I have all options on the table now…

Are to planing to stop by in a few weeks to lift the thing 20 feet upin air before we slide it to the attic?

The Cat

msaudio wrote:

I have built quite a few bass horns and found any thing over 1/2 inch ply wood reinforced is all you need, in front of your baffle. If you had ever built a few on your own and had the right equipment to test you would realize this, but when your a hasbeen you just try to overbuild thanking there is some sonic improvment. You should of let us horn pro's design and build it for you and you wood had the best then, instead of paying some carpenter with no horn building background off of some scibble you had on paper. Audio Geeks do this because they have been jerking off to high fidelity magazine's for to many years. Instead of looking at picture's you should try building something yourself, then when you talk about the subject you at least will have some credibility. A real jew would of built it themself to save the money on the labor. 3/4 plywood is all you need.  Preaching Horn Religion  MSAUDIO

MSaudio, before I did not build and did not managed projects to build midbass horns. This is my first 43Hz horn and I hope the last one - I do not do it for fun of building but because I know how to use it and intend to do so. Ironically what I do, would it be electronics or anything with acoustic system, is well exposed at my site: in pictures, explanations and in honest analyses of result. In contrary you claim that you “has built quite a few bass horns” but any my request to tell about them ended up with from idiotic accusation of me in homosexuality to absolutely ignorant claims about the use overly low resonance frequency in horns. I do not know who are you but I think that you are a fake. I quite know ALL capable horn builders in US and I do talk with many of them, consulting with them and compare notes about my project. I do not know you and I have a feeling that you do not exist. You most like another audio fool who do not understand what is going on at this site and decided to invent MSAUDIO - Preaching Horn Religion Character -  a full of parochial fears son of bitch with a complex of US’ Midwest pomposity.  Unfortunately, whoever you are, you are a bit overplaying and your functional MSaudio character looks more like a cardboard situate…

Back to the subject of skin thickness for midbass horn. I do not think that 1/2 inch plywood is enough for 43Hz horn. I heard a number of midbass horns with thin skin and I like none of them. I am sure that the thickness of the skin was NOT ONLY the factor. I heard only one midbass horn that I did like. Incidentally it was 50 Hz horns made from two layers of 1” wood, separated with 1 inch of sea sand. Unfortunately I will not be able to put THAT type of constriction to my attic.

Anyhow, I do appreciate your intention to be useful but be advised that the credibility and familiarity with specifics your have expressed might make me very soon just to ignore your posts. I do it with some other posters at this site; you are in the very near list.

Romy the Cat wrote:

I do not have a final design of my back chamber. The image above is a concept that I deliver to my carpenter – we will go from there to see what we can do. I certainly would like do not overbuilt the back chamber. The notion of adjustability is very good but the back chamber most like will be adjusted ONLY once. Well, I do admit that I would like to be able to play with back chamber volume with respect to the plate loading of the 3C33C that will be driving the midbass driver. But in which extend I need to go I am not sure yet. A site visitor last night proposed to me his way to do it – with two set of slotted surfaces - it might be a good idea, I need to think about it. I will need to come up with a design this week. The walk-ins are welcome….

FS: 47HZ
Re: 9.57 Ohm
Qms:9.173
Qts:0.304
Sd: 8.04^2m^2
Cms:2.35^4
Vas:7.42 cub.ft(212L)
dB 1W/1M: 99dB

Based upon his predictions I decided to stay with max sixe of back chamber of of 140 liters or 19 by 19 by 24 inches of I get near or above resonance of 40 Hz reactance-load driver. If after I load the drive into the horn I get low 30s resonance then I will go for the size of back chamber 19 by 19 by 16. The images below show the Jeffrey’s predictions.

Impedance and SPL at 75 liters (gray line) and 56 liters (black line).

Romy   If you would thank about what you are building and what it does, you would grasp the concept of my thanking. You have a 7inch hole on your bafflle with your woofer on the back side of it in a sealed box. The only presure that this device has is behind the cone from a sealed box and in the front of the cone were it is trying to figure out how to get threw the 7 inch hole. These are the area's that need to be real strong. After the sound goes threw the 7 inch hole there is no stress on anything, Sound will not buckel or deform the wood walls of your horn in any way. All you need to do is just remove the resonance of the horn skin, witch any long piece of wood has. This could be done with fiberglass and 1x2 strips. Also the resonance of the horn skin might be above the frequency that you intend to use it in the first place.  Good luck   Preaching Horn Religion    MSAUDIO

msaudio wrote:

Romy   If you would thank about what you are building and what it does, you would grasp the concept of my thanking. You have a 7inch hole on your bafflle with your woofer on the back side of it in a sealed box. The only presure that this device has is behind the cone from a sealed box and in the front of the cone were it is trying to figure out how to get threw the 7 inch hole. These are the area's that need to be real strong. After the sound goes threw the 7 inch hole there is no stress on anything, Sound will not buckel or deform the wood walls of your horn in any way. All you need to do is just remove the resonance of the horn skin, witch any long piece of wood has. This could be done with fiberglass and 1x2 strips. Also the resonance of the horn skin might be above the frequency that you intend to use it in the first place.  Good luck   Preaching Horn Religion    MSAUDIO

Yes, I know that back chamber and the mounting baffle need to be very strong – I spec them for 2.5” thickness. Regarding the “after the sound goes threw the 7 inch hole there is no stress on anything” – I very much disagree.  The resonances are very easy to detect by spilling sand over the horn skin and also by holding hands over the horn surface.  The people who REALLY build many bass horns (not the virtual horns of your imagination) almost unanimously report that mouth of the horns has maximum vibration from own sound. That is in complete correlation with what I experienced touching a few bass horns. If you report that sound does not stress anything after throat then I would question if you ever dealt with ether horn construction or with horn listening.

The units that i put in my pictures JBL AND ALTEC A7 both designs have a resonance just like all wood that you would rap your nuckels on even 2 inch thick plywood will resonate at a given frequency, that goes for glass, cement, metal, they all doit.  The nuckel test on the A7 is about 350 Cycles with no overtones or vibrations. The problem with the A7 Is the weak box constuction with no extra 2x2 reinforcement on the large side walls and back, those are the real problems. When you put a tone threw the woofer at 1 watt you get out 103 db at 333hz. So you thank you are going to hear a spike or see one on your RTA at 350 hz, Sorry you won't. Altec A7 that i have is the one that has 1 1/4 rapped dense fiberglass around the horn with fiber washers stapled to horn, and it has a single tone only when you put your nuckel on it, without viberation. I use mine for playback in my studio not for monitoring. These A7 are not perfect to use for sound reproduction, they serve a purpose with a large room of 46X30.  Preaching Horn Religion   MSAUDIO

I realized that this thread is slowly becoming the most sophisticated web recourse about Midbass Horn available. Trying to keep the thread educational I would like to introduce to my readers one more objective of my project. The subject is super important and could be a full blown own thread on it’s own but I decided to imbed this subject into my midbass project thread as to me, it is a part of my whole vision.

Many audio people unfortunately do not recognize that bass note is not a just “frequency bump” but a full of character LF event.  Audio people recognize zillion little characters in MF “bumps” but we for some reasons they do not presume that LF events have the same magnitude of characters. I think we do that because it is very difficult to get LF and as we eventually get some bass then we are so happy that we go alone with it without questioning it too much. However, most of the LF bumps that audio people get sound like the same note and the whole bass has no a lot of discrimination of character.

Topologically any single ported or dipole bass application sound like the same note.  The sealed enclosure might have some character but in relatively narrow band pass. I think that reasons for it is that all of them use in one way or another resonance of the system to amplify bass. So, is any way to get bass amplification with use of resonance and to use acoustic system as a strictly linear resistive-load transducer? Yes, here we have a midbass horn.  You see, in a properly design long horn the driver resonance does not exist. I mean it exists but it smeared by the that reactance and the whole driver operation see purely resistive load. Add to it a need for no super stiff suspension, no excursion, high compliance to low currents, sensitivity and etc and we have in my view an opportunity for LF notes to sound in max synchronization with the current of signal.

So, to have the max possible magnitude of sounds at LF is one of the objectives of my midbass project. This, combining with the super softness that I am craving from midbass horn will make me very happy.

http://www.GoodSoundClub.com/TreeItem.aspx?PostID=13846

I warn that I do not know where the super softness and super notes discrimination is coming from. My vision is to behave like Cats do. When Cat does not feel good she stop eating and put herself in hunger. The stoppage of the food stop bring the organic poisons that we get via food and the Cat body begin to self-regulate itself, in fact removing the former poisons from the body. (Read the works of Herbert Shelton and Ragnar Berg about intentional starvation/fasting). So, my idea is the similar: give to horn the best driver, best signal and make it absolutely flawlessly designed and the refuse to poison horn with all know to me sources of poisoning. My presumption is that then a midbass channel will be performing with “Original” non-poisoned Sound instead of demonstrating the artifacts of multiple mistakes midbass horns usually demonstrate.

Paul S wrote:

…. why do I keep having the sense that the long, near-parallel sides make for unwanted noise?