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"...Jessie, I pulled posts from Macondo Axioms thread and encapsulated them onto a new thread dedicated explicitly to your project. I hope you do not mind..."
No problem... I was actually starting to feel a bit apprehensive about going "off thread" in the original location.
I just noticed that there is a slight error in the word "Project" (you wrote "Peoject").
"...Also, and it is very-very important, the bottom line all the midbass horn will a short straight line instead of a radios. That will enable to lower midbass horn relative the top of the lower midrange driver. If to be too “obnoxious”, then I would even conceder to make a small bite-off at the bottom of the midbass horn in order to bring it even lower..."
If you look closely at the images, the "bite" was in fact taken out of the mouth of the horn.
"...However, if you go for non-spherical shape then I would strongly encourage making non-even amount of segments. So it should not be eight segments but nine or eleven, in order to eliminate any near-parallel surfaces inside the mouth of the horn..."
Very good point! (easy to accommodate)
"...The point that I was making is that lower midrange horn is sitting, at least in my case, right at the height of my ear. So, when I was blubbering that Macondo can be integrated from as insultingly close distance, I implied sitting position. If to stand up at extreme nearfield position then obviously the lower midrange horn will be shooting right at your face and the total balance of sound will be very incorrect (I low-pass my Fundamentals Channel very shortly). So, you might not be able to stay in front of your speaker at nearfield and to conduct the music :-)..."
Ahh.... Ok. So I'll have to dig a pit in the floor.
"...BTW, find among your neighbors someone who has an OK sounding Tannoy Red installation and try to listen it… Try to puck those neighbors who do not do anything with driver, crossovers or enclosures. You might find it educational..."
If you could meet my neighbors, you would find even more humor in the above suggestion... I will keep my eyes open for a pair to buy... No risk as it is easy to resell them.
"...A few comments. Vitavox S2 in 400Hz horn crossed at 3200Hz will sound acoustically much lover. If it is a new plastic diaphragm then it will run all the way to 1000Hz. Therefore the Lower Mid-Range could be cut shorter then 3200Hz. It was very interesting to experiment with it and move the crossover points up and down, letting both S2 channels to work together in mid range..."
Once the frames are in place with the horns I will get the mic and the RTA out and get more serious about setting up the crossovers. I like the idea of letting the 180Hz horn take on a bit more of the work... Its just a question of discovering at what point to hand off the job to the more qualified horn, while avoiding acoustic redundancy.
"...Also, you did VERY good going for Lower Mid-range not 250Hz (as I did) but 180Hz. It was what I am “non-violently” considering to do as well..."
Yes, when interested I remember close to 100% of what I read... So you should really say that I did very well in retaining what I read in your posts before making the decision... It is largely from your experimentation that I drew my conclusion.
"...The driver can handle lower but the horn can not. So, my idea was to do for 170Hz-180Hz horn and drop the crossover point for 500H second order..."
With the 170-180Hz horn why not use 1st order at a higher cut off frequency ?
"...As you understand with a frame of the fixed height is kind of complicated as it will narrowing the window through which the tweeter might shoot. I still, nonetheless, am considering doing it, perhaps going for exponential profile..."
Here is an opportunity to make your frame telescopically adjustable :
Cut off your vertical mast at 3/4 of the way up from the base, then buy 2x1m of square section tube that just fits inside your vertical mast (if you ave trouble finding the correct size, you may have better luck using 4 smaller tubes welded as one)... Get your welder guy to weld one meter of this smaller tube to the vertical part of each of the top 1/4s of your original frames... Also have him drill 3 holes (of a diameter that will accept a large bolt) one in the back, and one on each side of each vertical mast about 5" below the cut, then weld on a big nut centered over each hole... run the bolts in a few threads and insert the top 1/4 (depending on your ceiling, you may have to tilt the frame on its side)... Set the height as desired, and lock all bolts on your new telescopically adjustable frame... Done.
BTW : Today at lunch time I picked up the metal for my frames... The design requires a total of 182 cuts... Even with the super saw this place has, it took one man all of Friday to measure and cut everything... I don't even want to think how long it would have taken me to do it by hand. It is designed so that welding it should be very easy, with minimum possibility for error.
"...Also, since the tip of your from will me small you might consider also a following arrangement. Sure, you can angle the axis of the big horn more sharply..."
I have to think about this idea of stuffing the top of the tower up into the mouth... It could help with "packaging"
"...I would like to pass some observations regarding my virtual experiences with location of amplification within the frame of my Macondo. Your acoustic system (by the way you need come up with a name, at least for us to refer to it) will be somehow similar to Macondo and I think you might consider my past examination of this subject.
About the name... Ok, but I need a few more days to learn the Bantu lingo...
If you go for building off dedicated amplifiers then locate them in frame might make sense, considering that the design olds amplifiers and thier packaging will be made having the idiosyncrasy of the frame in mind. However, I would not recommend to putting Lamm ML2 in the application layer of your speaker, and I would keep Lamm sitting on the floor next to the loudspeaker. ML2 is too large, 88 pounds of rectangular mass, with 2 large tubes which dissipate a lot of heat. I think it is irrational to stick the entire amplifier with its power supplys inside of frame. You would need to make and very strong, very strict, very expensive arm-shelf for that amp, and then to trash the arm-shelf, as when you go for dedicated amplification, as dedicated amplification will acquire completely different arm-shelf.
Well there is no problem for the strength of the arm, but the ML2 may not be the right amp to place there. With regard to the heat issue : Were you refering to degradation of listener comfort, or would warming the horn/driver possibly become an issue?
Also, Lamm ML2 is quite sensitive to what it sits upon. You'll have experimented, I'm sure, with various platforms and suspenders for these amplifiers and you will have witnessed is that they does affect the sound of ML2. I presume that the arm-shelf within in your frame will not, or might not, be an optimal surface to care ML2. Whatever this surface will be you will be forced to use it as you will not have space to put anything under ML2 (you will have ~10-11” to play with).
I currently have the amps sitting on a double layer of... WALKER POINTS!!!... Ha... Just kidding (this is a reference back to the golden days of "verybigamp")... Really, they are sitting on 50mm thick blocks of... laminated hard wood, which in turn are sitting on... are you sitting down?.... 5 blue racket balls (or squash balls), which in turn are held in place by big cast iron pipe flanges which you can find at Home Depot.... the entire platform floats... I mean really FLOATS (I will take a photo some time).
There is another factor, which might the laughable for others, but to me personally it would be a major impediment - I hate to see loudspeakers. I religiously distaste any loudspeakers of the bright colors, any equipment with bright features on it, or any other explicitly creamy features on something which is visible - in most cases the acoustic systems. I paint all my stuff in matte black. The darker, the less informing installation is looking is the better to me. I tend to listen in dark, I tend to close my eyes, and if I open my eyes than I would like to be less distracted with playback appearance.
I agree 100%... But there is political pressure... I will probably have to listen to the W in WAF who has asked for a light finish (after all, she is letting me get away with quite a lot)...
All that aside : In my testing, what gives the best sonic results so far is sealing the horn with polyester resin, then applying several generous coats of bees wax to the inner surface... It ends up looking a bit like pale colored unpolished marble... The resin could of course be tinted whatever color simply by adding pigment... I got to this point by trying one of my moulds with a compression driver (I use the resin and wax to prepare the mould)... I then took it further. I may find something that works better, as I have not tried that many different surface treatments.
To me personally it would be extremely distracting if I would have two full lit 6C33C seating inside of my loudspeakers, in the open space, right and the level of my eyes. So if I were doing amplification mounting inside of the frame then I would hide the lights from the tube at any cost. By the way, do not forget that Lamm ML2 is not a symmetrical amplifier that will make it slightly ugly looking inside a speaker’s frame for the people who even enjoyed watching the tubes glowing… :-)..."
Well again, I don't know if I will really put the ML2s in the frame... Nevertheless, in the seated position (is in the black and white line print above) the tubes would be obscured by the mouth of the Upper-Bass horn.
Thanks again for all the input.
jd* |