msaudio wrote:

Putting The Mid Bass horns behind your head will not work. This thread was about Mid Bass Horns Project, do you thank you will be able to use any frequency above 80 cycles with rear fired horns that are behind your head? That is a Joke. It looks more like a low frequency horns thread. So you are building a set of horns that will have a range of 35Hz to 80Hz max if even 80 might be a big question mark, there will be some real bad phase problems, time alignment will make it so your forced to use digital crossovers and that is more of a joke. You would be better off with the way your system was to start with, an a few mods that are simple. I preach horns but i will be the first to say that over sized horns suck. You will spend a lot more then $1000.00 on a Attic horn fiasco and when it is compleat you will want to start over because of the disapointment. But this will work out just great because you will go to a large horns setup for bass, then in the future after you learn from your mistake you will be bad mouthing them to. But pride and you pocket book will take the hit.  Msaudio

Msaudio,

I hope you are today more sober then you usually are and will be able to comprehend what I say.  The horn will be not 35Hz to 80Hz max but most likely 50Hz to 200Hz. If you are willing to object anything then get familiar with the subject of the objection – it was written about it many times. Your comment about prospective problems with phase problems and time alignment are ridicules – the whole project meant to be time-aligned. I will spend tens time more than $1000.00 and I have no assurance that I will not face disappointment.  So, what? It will be not first time and I hope not the last time. What however I have is the pride and knowing the result I am accustomed I do very comfortable with the pride for what I do and what I am trying to accomplish. Sure, I would like to learn from the mistakes of others. I do learn and I do not mind to contribute to the composite consciousness of playback organization my own experience. This is what my site is about. I do honestly tell about my project and I do interest about criticism. Unfortunately your are trying to deliver a criticism at the level that I consider sub-acceptable for myself.  Your arguments are very weak not to say illogical or ignorant, at least it is that way how I perceive it.

jessie.dazzle wrote:

One simple way to get a feeling for how this might or might not work out would be to place your currnet mid bass arrays in the rear of the room and run them with a band pass filter from 50-200Hz.

Jessie,

unfortunately I do not think that it is possible. You see the exhaust of horns will be not toward to the listening position but way about it to the pitch of the cathedral ceiling. This is the whole key and the whole uniqueness of the project. The LF will be coming to the listening position but the more directional HF will be hitting the room and detracting in there. I anticipate that I will be able even to go away with very slow low filter on the midbass horns as there is no direct line of sight between the horn and the listening position. It is imposable in my view to predict how much reflected HF will hit the listening position. It is not to mention that the listening position will be hit very much delayed reflected HF, the HF that will be phase randomized. That randomized delayed HF will be much higher than Haas delay in relation to the main channels, so I think that those randomized delayed HF will be now even associated with main signal and will act as reverberation. I have no idea how to model it – it is very complex. My feeling is that to tune the midbass horn I will be with the low-pass filter – I will be driving it down until the horn will lose sensible directivity. My estimate that at 1000Hz I will lose at least 15dB-20dB from this midbass horn from listening position and if so then  200hz will not be a problem at all. Of course no one know how it turn out but the right way do not have the answers is do not try.

The idea I think is very elegant, I just hope that my carpenter and my framer will not give me bad news….

Wojtek wrote:

You mentioned it yourself that the most interesting midbass you ever heard was from corner horns. Why not utilize if you can a pair of K-horns (or clones) bass (midbass really) bins with sort of moveable fake corners? They can be found dirty cheap these days and can sound pretty exeptional in the 50-150hz band with a right driver and I think your Vitavox 15" are right drivers. I don't see any of your "exotic" ideas working except when you put those gargatuan Midbasses in the room and it will loose then all "homely" qualities you seem to value. At least it could be a good "test rig" which afterwards you could sell (once you make them to sound "proper") to faithful devotees for real money

oxric wrote:

Firstly, the costs involved and the real chance that this project might not work make this project statistically a horrible waste of money, time and resources which could be better spent in pursuing other solutions which are more likely to end in success. Your assessment of the cost of the materials must surely be either incorrect or grossly distorts the real financial costs of this project.

The cost. I do have a very clear, very realistic and well-budgeted plan (that I have my reasons not to publicize for now) but it will work ONLY if the space on attic will more or less comply.  I am OK with that cost. If the project will require more extended intrusion into the building framing or moving fundamentals of the stricture then the cost-benefit assessment will be adjusted and the conclusion will be drown accordingly. With all my appearance of being a super-compulsive nerd I am in fact a very pragmatic person. I for instance plan to do this in a way that will not drive the cost of the house down…

oxric wrote:

In addition, regarding the localisation of some of the upper frequencies where your mid-bass horns are likely to be operating. I doubt one could redress problems with the localisation of these low frequencies, especially if they cause vibrations and localised air ripples in the space above your head. Instead of the vibrations that move across the floor from a not properly isolated subwoofer, you would think that Zeus in the skies is taking care of the lowest notes.

A valid concern, I do not have an answer. I just do not know. My only sentiment is that I did have a number of experiences what I loaded channels to walls/ceilings and they behave very much different then direct radiators. You can take a monitor, low pass it at let say 1000Hz and place it in the middle of the room. The monitor will be well-localized. Then attach the monitor to a poll and place in at the very ceilings. The monitor will be load the whole room. I hope, just hope that I will be able to use this effect giving the fact that my midbass horns will be loaded to the ceiling, the cathedral profile of which will be the continuation of the horns’ mouth.

oxric wrote:

I imagine your answer would be that your Fane 8M upper-bass horns and low frequency subs would anchor the low frequencies in question….

Yes, this is certainly the hope but who can evaluate or predict the validity of the hope?

oxric wrote:

Thirdly, I cannot see from a purist perspective how you will get around the time delay problems (a point that MSaudio does not make forcefully enough) without resorting to equalisation in the digital domain, an area that I thought you considered a definite 'no-go area.' This should I think be used as a last resort but I do not think you have quite reached that point yet, unless you have carried out further research or experimentation which are not apparent in this thread.

I completely do not understand the concern about the time delay. The whole idea is to make the midbass in-time with the MF. Look at the diaphragm.

http://www.goodsoundclub.com/Site_Images/HousePlan.jpg

The pair of the “A” horns is something that I am planning to place in attic. If everything will go as I plan then they will be very much time alighted… and invisible in the room.

oxric wrote:

Fourthly, I think you have given insufficient weight to the very psychological effect of investing such an arduous amount of time and funds in such a project, irrespective of how successful you are at integrating the mid-bass. Your mind, even your 'bones' will know where the bass is coming from and you will never be able to forget that when you are listening to music I daresay. The last thing you would want is to put yourself in a situation where you are constantly on edge, asking questions about the quality and localisation or time delay issues rather than simply relaxing and enjoying your system after a very tiring and stressful house move.

Well, Rakesh, how different it from anything else? You instead of listening music could constantly to be concern about the VTA or cathode emission of your output tube. I think what you say is valid but it has no direct relation to my project.  I am well familiar with the fact the I do not build the midbass horns but I build Sound in my room and I am not planning to take my eyes from the ball. Well, if it turns out badly then all that I will need to do is to cover the triangular wall with dry plaster wall and forget that there are horns behind it. It is juts money. If all that we peruse are money then all that we find will be just money. I assure you that I’ve lost much more than what I might loose on this midbass project. I wish that that the midbass project was the worst lost I had in my life.

oxric wrote:

Lastly and most damning of all, in my humble opinion, you do not know what life has in reserve for you and you may meet the woman or cat of your dreams tomorrow, change jobs, or for any other reason, have to move home. I doubt that moving the rafters will be to the liking of the moving professionals you employ.

Do you think that if I change my job, meet the woman of my dreams or get deadly cancer then I will change what I am and switch from audio to Philatelia? Well, if so then don’t you think that while it not happen yet then it is good time to build the midbass horns? :-)

oxric wrote:

So as I said at the beginning, I hope you do go ahead and prove all the doubters such as myself, wrong.

msaudio wrote:

When you set in your chair looking and listening 2 your sound system you are trying to create in your mind and your ears the illusion of instruments placement on the stage in front of you, to make it more lifelike and real. So you putting horns behind your ears will take you out of what the recording engineer recorded in the first place. Examples a trombone frequency range 85Hz to 9500Hz, Male voice 100Hz to 8000Hz, the range you are looking for behind your ears and head with your mib bass horns is 45Hz to 200Hz. So part of your male voice that is always center of stage in front of you will be behind you out of phase. This is a fact and no argument. The only person that would argu these facts is the fool who thought about doing it in the first place and use money as no object for an excuse or saying someone is drunk when he does not drink.

jessie.dazzle wrote:

To my understanding, taken individually, your attic horns would be more obviously working in a half-space environment. For any output that is common to both the L and R channels (some in the case of stereo recordings and all in the case of mono), they would effectively be working as a single horn, in which case they could be considered to be working in a quarter-space environment. To ensure a full-time quarter space environment you could extend the dividing wall (the wall between the two horns) out along the apex of the ceiling. This will not ruin your living room if the dividing plane were made from a single suspended piece of plate glass, without a frame.

Yes, this is very good point and I have thought about it. From a larger perspective I do not like the whole idea of the horns sitting on the same wall, but it is what it is so far.

jessie.dazzle wrote:

Does your attic offer the possibility to make the horns longer?

Yes, I have pretty much unlimited depth of the attic and I am planning to make horns longer then calculated. To make judgment about it I would need to know what kind horn it will be (mouth size) and what kind free air resonance I will be able to get from my Vitavox 15” drivers. Then I will know what will be the length of the horn and knowing the arrival time from that calculated length I will know how I can cheat with the horn depth.

Romy the Cat wrote:

If I succeed to make my midbass horn at attic then I will face another problem that I do not know how to address at this point. The horns will be powered from Melquiades bass channels – it means it will use a good 70 feet speaker cable. If I go with Copper wire then it will have per foot: 4 ga  - .000292 6 ga  -   .000465 8 ga   -  .000739 10 ga  - .00118 12 ga  -  .00187 14 ga  - .00297   Let presume that I will go for 12ga cable it means that I will have: 0. 00187 * 70 = 0.139R. This permanent impedance is a bit bothers me. It is not the impedance distributed in the secondary of the output transformer but it I impedance that voice coil get increased. This perm impedance only adds compression to the sound of driver. It is very possible that for my 16R driver the .1R will be negligible but who knows how much negligible is negligible. I am a bit afraid to go with thicker wire as it usually comes with less interesting upper bass – the sound feels like become “hollow”. Sure, it possible to get involved in the cabling wars then, and I am sure I will. What are the alternatives? To run a long line level interconnect and to put the amps on attic? To fire-dangers in my view… I was thinking to do it with fire sensor above the amps in attic and close circuit TV monitor but I kind of getting more complicated then I would like it to be…

I do not like the construction he did but I love the picture of this horn at the sealing of some kind of bar.

http://www.minhembio.com/The_rose/122971

Will I be look as happy as this guy is after I go over my project?

This weekend I am starting to draw the sketch and the preliminary building plan for my midbass horns. I initially thought to recruit somebody who have done it to help me with plan but after consulting with a few people I feel confident that I have all necessary skills and knowledge to do the job myself. I will be posting all information at my site, whoever feel to comment or to criticize it as I go along, please do so.

The whole project is more or less clear in my mind but there are two questions with which I am not settled.

1)  Where to buy inexpensive birch plywood? There are American, Canadian, Russian and Chinese birch plywood. I would like to go with Russian – much better quality, but it got pricy nowadays. I would like to pay for ¾ sheets of 4 by 8 no more than $40-$45 in case of mass buy. If any of you know in your jurisdictions a sores to get cheap Baltic birch then let me know – I might arrange shipping. Still, I would like to get the plywood in New England and to pick up it locally

2)   The throat transition piece – I do not have a clear image how to do it. The throat will be 7” circle, then it will be a circular pipe of very low opening rate (like all hyperbolic it almost parallel in the beginning), then it will be gradual transition to triangular shape. The whole transition will take no more than a foot long and I see a very clear how it will be. What I do not know is how to make it: material, construction techniques, way to join it with the rest of the horn, etc etc etc… My leading idea to make it from concrete and while the cement did not solidify yet to place some stands in the concrete. How to mold the complex transition piece I do not know yet. I can draw it but I do not know how to make it. I will entertain any suggestions.

Can't help with the plywood source , I'd like to buy some for myself for that price . Transition piece I'd do from stacked plywood layers screwed and glued together and cut with jigsaw. The way John Hasquin built your upperbass horns .He posted the tutorial somewhere on the DIY, orr AA site. The one or two pieces when the shape changes from round to triangular would have to filed by hand. Or if you want to be really precise you could order (I think so) a ready to go pieces form Jeffrey Jackson .He built a CNC router and I don't think it would be a problem to make such project. You can make really massive throat piece that way. The connection to main horn would be a wooden collar/flange on the main horn attached to throat pieces with dowels and long screws. Regards, W

Here I would like to share some basic ideas about the skeleton of the horn. This is just a view from 50.000 feet but it will give some illustration what is brewing in my mind.

The one side of the triangular horn will be flat and will sit at level of the house sealing (attic floor). Two other sides of the triangular horn are curved. They are not continuously curved (I do not think I need to bend if for such a low frequency). They rather are a sequence of 7-12 flat panels (circle’s chords) that are mounded at different angle and by changing the angle they shape the hyperbolic curve.

Here are my more or less final circulations in metric: Hyperbolic at 0.6, Throat = 249cm (7' diameter), 45Hz, ¼ size

Since I would like to keep the proper hyperbolic curve then the bends in each curved side will be almost in logarithmic scale as hyperbolic curve changes a lot in the end of the profile. Here is some twist however. I would like to take advantage of my triangular shale and to make the first and second bendable surface to have asymmetrical bends (chords). If you look at the image then you will clearly see that chords on one side of the “bendable surfaces” are in the middle of the chord on another side. Doing this, I will increase smoothness of my opening. It will not be complicate to do it but it will be a bit pain in ass to circulate the sq area.

After a long contemplation about the material for the horn I have my leading idea of something that I call “Soft Shell Boat” approach. I did contemplated many different approaches, starting from very cheap and frugal (like most of the DIY Californians do) to very much overbuilt approach (two layers with sand between them). Considering my specific case and reasonable weight limitation on my attic I think my “Soft Shell Boat” approach will work very nice. The idea is to build an inverted boat hull with ribs outside. The Soft Shell will be most likely ¾ Russian plywood birches. Each connection between the chords will have before and after a set of ribs (brasses) made from 2x2 and 2x4 (asymmetrical). The 2x4 of the any nearby chords will be connected by 2x2 and 2x4 (asymmetrical as well).  The whole idea do not use very strong surface of the horn is to let the very massive ribs to care the load across the horn surface. If everything will go as I plane then it will be no more than one sq feet of plywood in free hanging mode.  The image below illustrates the idea for 4 chords (divisions between the chords are think black lines and the ribs are thick lines). For sake of simplicity the chords in the image are made with no angles.

Rgs, Romy the Cat

Jessie has already shared the smartest approach to the transitional shapes. The idea is to build it up or cast the weird stuff, until you get to a shape/profile you can easily work with plywood.  You will NOT want to try to make curves with 3/4" birch ply, so use this for the straight walls and lay up thin ply layers over a frame for the curves.  The price of plywood is currently at a 2-year high.  Good luck finding good 3/4" birch ply under $60/4X8 sheet.  Some birch ply will edge shatter if nails are placed too near the edges, so be mindful of that.  I recommend pre-fitting and then gluing everything in addition to nailing with ring-shank nails.

Best regards,
Paul S

Wojtek wrote:

Can't help with the plywood source , I'd like to buy some for myself for that price .