Build log: DIY rotary sub for contemporary HT in 100 year old house? - Page 42 - AVS Forum
First ... 40  41  42
Dedicated Theater Design & Construction > Build log: DIY rotary sub for contemporary HT in 100 year old house?
AndreasMergner's Avatar AndreasMergner 05:20 PM 11-18-2012
HT related this weekend: um, installed two shop lights in the basement. Wow, I wish I had done this earlier. I have been using one of those lights with a hook and hanging it wherever I'm working. The shop lights are so much better. Now, if I could just get some more lighting in the theater itself.

Cuzed, RT, I appreciate letting me know now what I'm in for. Approximately how much do you think this sweet little girl will disrupt my life??



RT: That is hilarious about your BIL. I hope it doesn't come to that....although *now* that I've put some money into the system it *should* sound better than it does. I wonder if I get new ?XYZ? will it sound better? Oh boy.
Sponsored Links
Advertisement
 
blackoper's Avatar blackoper 05:11 AM 12-21-2012
So quick question, is the design of the rotary subwoofer as simple as reading this failed build log appears? https://sites.google.com/site/amateuraudio/projects-1/the-rotary-sub - Like no servos or anything are needed. Just a much beefier version of say how a helicopter's blades work with the sub's in/out moving parts providing the pitch of the blades? Am I missing something then because it seems like a good 800 rpm quiet a/c motor, some heavy but quiet and balanced metal blades and then some beefy steel components for the blades/linkages/etc and you are done. I need to reread about your proposed/in progress design but thought I'd just ask too

Edit: ah was looking in the wrong thread. Reading through your slow rotary sub build thread again (it's been a while)
RTROSE's Avatar RTROSE 05:22 AM 12-21-2012
^^^^^blackoper, with your description you almost make a rotary sub sound easy to build. I'll let AM answer the technical stuff but I assure you it is quite a challenge to build one. Thy are not definitely not main stream and there is a reason why you don't see them mass produced commercially.

Regards,

RTROSE
blackoper's Avatar blackoper 06:28 AM 12-21-2012
Quote:
Originally Posted by RTROSE View Post

^^^^^blackoper, with your description you almost make a rotary sub sound easy to build. I'll let AM answer the technical stuff but I assure you it is quite a challenge to build one. Thy are not definitely not main stream and there is a reason why you don't see them mass produced commercially.
Regards,
RTROSE

I just got done rereading his thread. I may give this project a try after I get my other in progress stuff done. I actually have access to a nice cnc mill/metal shop and some very experienced metal machinists that would be able to assist. Could be fun to make one and then offer a cheap kit for the community. I know I'd buy one if it was available
AndreasMergner's Avatar AndreasMergner 07:01 PM 12-21-2012
blackoper: I think it is a somewhat simple idea, but as with a lot of stuff the devil is in the details. My design mounts the fan, linkage and driver on a shaft supported on both ends with angular bearings. The shaft goes through the vent in the driver. Then I plan to use a 3 phase motor and speed control to turn it. One issue I am having is that if you leave the driver whole, you have a large cone (mine was 15") in the way of your airflow. The Thigpen is only 17" in diameter, so that doesn't leave you with much! If you cut out the cone, then the coil is only supported by one spider and the bushing of the linkage. You have to mount the driver in nearly perfect alignment otherwise the coil will rub on the magnet. There is very little clearance. In addition, the driver has this rather strong magnet that wants to pull it to the shaft which will basically crush the coil instantly. There are ways to mount everything in a order that would work, I think.

Also note that going "beefy" and with metal blades you will need a strong driver and you will need to calculate the max frequency it will do based on the additional mass you are adding to the "cone". I need to get to ~25 hz because I am using a folded horn above that.

I don't know if any pictures are left on either thread, but I can edit the links to them if you ask. (They are a pain to fix.) The new version of AVS broke all my pic links.
AndreasMergner's Avatar AndreasMergner 02:43 PM 01-28-2013
So, I cut a 2' x 2' hole in the wall of my beautifully sound proofed room to allow waves of ULF bass to come through. That is not a lot, but it is something. rolleyes.gif

I put a fan in the hole where the rotary goes and I could hear it on high, but not on low. If I opened the door to the theater, I could definitely hear the fan on low. So, there's some sound attentuation going on in that rotary cavity. I think it will be enough so that you don't hear the rotary unless the vanes are deflecting.
RTROSE's Avatar RTROSE 03:38 PM 01-28-2013
Congrats! THAT is progress. I bet it killed you to cut that hole though.

Regards,

RTROSE
AndreasMergner's Avatar AndreasMergner 04:32 PM 01-28-2013
Yeah, I think that is why it took so long to do it!

I might rig up something to seal the hole when I'm not using the rotary...if I think I need it. The room with the rotary will be blocked off from the rest of the house with a wall so I shouldn't be getting too much infiltration from there, but then again my dehumidifier is there....but I have also thought to put the dehumidifier on a timer so it only runs at night. So many options when you have 2 months to think about things between doing actual (HT) things. biggrin.gif
RTROSE's Avatar RTROSE 08:08 PM 01-28-2013
Could you not put the dehumidifier on a switch so you would have more control over it vs. just running at night? That seems like a better option if you can do it that way. When I was in a construction lull I would go down to the theater and just think about how I was going to do something, usually this would pan out later when I actually got around to doing it. Mostly.

Regards,

RTROSE
AndreasMergner's Avatar AndreasMergner 08:21 PM 01-28-2013
I could put in a switch, but it runs intermittently so if I started watching a movie and forgot to flip the switch the dehumidifier may kick on. I don't think it is a huge deal if the dehumidifier doesn't run all day long. It is a big unit. (insert joke here) I just don't want the concrete floors getting moist. If it is running every day it will be fine. It is when it doesn't run for a couple weeks that it starts getting musty. I can play it by ear though.

Yeah, I like the planning. Usually I know what I need to do next. I have a bunch of work that I know what needs to be done, but it is overwhelming to some extent.
RTROSE's Avatar RTROSE 09:12 PM 01-28-2013
Ok. Understood. My parents have a dehumidifier that runs pretty much all the time in their basement, Did not think about the intermittent issue. I too would not want to see the concrete start getting moist as that invites all kinds of other stuff to come to the party and ruin things.

I had the overwhelmed feelings several times throughout my build, but it helped me to break each item down to smaller chunks so I could get at least one or two little things done so that way I felt like I was at least making some kind of dent in the the "to do" list.

Chin up, shoulders down and just keep plugging away.

Regards,

RTROSE
Augerhandle's Avatar Augerhandle 09:44 PM 01-28-2013
Quote:
Originally Posted by AndreasMergner View Post

I could put in a switch, but it runs intermittently so if I started watching a movie and forgot to flip the switch the dehumidifier may kick on. I don't think it is a huge deal if the dehumidifier doesn't run all day long. It is a big unit. (insert joke here) I just don't want the concrete floors getting moist. If it is running every day it will be fine. It is when it doesn't run for a couple weeks that it starts getting musty. I can play it by ear though.

Yeah, I like the planning. Usually I know what I need to do next. I have a bunch of work that I know what needs to be done, but it is overwhelming to some extent.
it shouldn't take much to automate it so that the dehumidifier power is shut off when your theater is turned on
First ... 40  41  42

Up
Mobile  Desktop