GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Deep End DIY - Australian take one Macondo.

Post Subject: Deep End DIY - Australian take one Macondo.Posted by Romy the Cat on: 1/20/2016

I sometimes visit an Australian site and familiarize myself with progress of “acg” who it trying to build Macondo like acoustic system.

http://www.stereo.net.au/forums/index.php/topic/75784-deep-end-diy-my-first-speaker-project

A few weeks ago I requested at the site and answered a few open questions. I do not think I argued with anybody or was involved in any controversial topics. In fact it looks like the member in there were appreciative of my contribution. Well, for whatever reasons I got banned from the sites. My initial sentiment was why the hell they doing it? Well, thinking for another 5 seconds I realized that my initial reasoning was very accurate and in fact did not change over the last good 20 years: audio people generally and whose who elect themselves in administrative position particularly are fucking idiots. It is not a big deal. The stereo.net.au might joint a long list of the audio sites that do not deserve my presents and they can die this their little pathetic secret. Nevertheless, the efforts of the “acg” has nothing to do with the idiocy of the site administrators and sine I discovered that “acg” asked me direct quite intelligent questions and since I can’t answer them at the Australian site I decided to make the Australian’s Macondo discussion available at my site.

On 15 January 2016 - 09:58 AM acg posted the following post:

http://www.stereo.net.au/forums/index.php/topic/75784-deep-end-diy-my-first-speaker-project/?p=1527678

I do encourage you to register at the site and view the images and acg’s ideas are interesting. In his post he is asking:

@ Romy The Cat , one question. What I need to be sure of for this curved design is the horizontal distance between the acoustic centres of the Midrange Horn and the Upperbass Horn. I am really only just making a guestimate so far and it could easily be 50mm+ (2"+) or more than the distance that I have used which means that my curvy frame could get in the way of time aligning the horns. Are you able to drop a plumb bob from somewhere on the midrange S2 and tell me the distance to the throat of the UB horn (or better yet to the front of the Fane 8M driver or to some identified point on the driver). Using your listening distance and assuming an ear height I can figure out the what I need to know and make sure that the curvy frame is not going to get in the way. For example...

http://www.stereo.net.au/forums/uploads/monthly_01_2016/post-139669-0-45165500-1452815421.jpg

Well, acg, I am not wild about your idea of the curved frame, primary on the reason of esthetics but it is your speaker not mine and you shall do whatever pleases you. A few mandatory things that I would like to mention and I think you need to factor it into your design.

1) The Macondo channels shall form a curve or parabola with your listening position being in center of a curve. I have illustrated it years back at the following image: http://www.goodsoundclub.com/Site_Images/MacondoFrame31.jpg I would very much discourage you to angle the horns and many foolish people do, juts align the channels. To do so you would need to have a provision to move the channels closer and further. Your current design does not allow you to do it. You might avoid to move the channels closer and further if you calculate and factor in the curvature and listening distance into the initials destine of the channel arms.

2) During the alignment of the channels you do not need to drop a plumb bob from the horn throat or the driver exit but from the location of the driver diaphragm. The S2 have diaphragm on the back, so you overshooting in your design good 5-6 inches

3) The time integration of MF and Upperbass is tricky. You can calculate where the Fane diaphragm is, where the S2 diaphragm is and they pretty much not on a curve but on direct vertical line. The precession of that calculation is kind of not important as Fane is not flat and has dome depth of the diaphragm. So, doing subjective assessments of the integration benefits I realized that all that you need to do between those channels is putting the MF atop of the point of max amplitude of upperbass. 500Hz has a wavelength of around 2.2 feet, 1000Hz is around 1.1feet. With such a long wave you will have a very high precision alignment if you align them approximately by geometry and then lock acoustically by summation of amplitude measurement. I did exactly this and then, after I knew the final position of my MF driver I order a fixed, well calculated arm for my tweeter. In my case I make my MF drive to position atop of positioning table with .01mm accuracy. I personally do not feel it is the best idea and I would rather advise to make HF being able to be .01mm positioned by MF would be fine with 1-2mm. You would not need a machinist position table for it and some kind of general slider would be fine.

4) You do want to lock the location of the Midbass horn with the frame and it will be moving side to side. A horn that angles breaks time alignment.

Rgs, Romy the Cat

PS: I won’t be reading too much at the Australian site not to mention that I can’t see the pictures. So, if you need anything then ask here.

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