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Discussion Starter #21
Yes... I've considered it, but I don't want the IB backlashing into the garage and creating more noise for the house. I would lose the sound insulation of the room... which is something I worked very hard to accomplish. :yes:
 

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Discussion Starter #23
Here's what Rodny and I talked about doing today...



We can adjust it a little bit if needed.
 

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Hey Sonnie, what a neat project! This isn't going to help matters I know, but there is a calculation for it. What it boils down to is your going to need a 3.25 gap from the top of the base plate to the baffle instead of 2" I'm sure if we put our heads together.. we could figure something out, even though (in my perception) things just got a little more restricted.
 

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Discussion Starter #25
3.25" is not a problem at all... we can handle that. I stuck 2" in there just because that's what my PB12-Plus/2's are. I just figured it would be the same. But since we changed it to a front angle... thanks to Paul's suggestion, it gave me plenty of room. I can get more volume if needed... probably up to about 24 cubic feet.

I guess the next steps are:

  • Making sure we are close enough in the ball park for volume.
  • Determining what frequency to tune it to.
  • Port size and length.
  • Where to install the port (will it fit top to bottom and can it be fired out the bottom center or top center ... or does it need to be out one side... or two ports, one on each side).
 

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Discussion Starter #27
That sounds good to me.

Right now I'm at 581 liters... I suspect there will be more than 11 liters occupied by the bracing and subs, so I probably need to up that some.


Is that 34" including the ¾" wall? That would make the pipe part actually 33¼".

So can I stretch the internal height to say 36" and adjust the width if needed... then place the port center of the box either ported up or down?
 

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Make the actual port (I'm assuming you'll use sonotube) 34" long and then roundover in addition.

The port should be firing out one of the sides on the long 90"+ dimension. 36" definitely won't cut it, the internal port opening wants to be a minimum 8" from any obstruction, preferably more.
 

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I have a few reservations.

Physically moving that huge and heavy box into place.

Panel resonance will have to be dealt with by bracing.

Bass localisation. The Plus2 is quite a compact source in comparison.

Phase-related response errors.

If the box is ported at one end with the driver at the other the physical separation of the sound sources might prove problematic for the nearest seats.

Have you considered placing the enclosure(s) in the garage firing through the wall into the HT?

Only the slight noise escaping through the panels to worry about.

You can have two widely spaced enclosures for a better bass spread without cluttering the HT.

Much greater freedom in design without worrying about finish.
 

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If the box is ported at one end with the driver at the other the physical separation of the sound sources might prove problematic for the nearest seats.
Because of NF seating, this was my first thought.. I'm thinking that orientating the port with the drivers might serve you best, but you don't have the height for a single.
 

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Discussion Starter #33
Physically moving that huge and heavy box into place.
True, it will be heavy, but nothing that can't be handled and it will only have to put into place once.

Panel resonance will have to be dealt with by bracing.
Yes... it will need proper bracing, no doubt. Rodny will be helping me and he's really good at it... not that he's built one this big, but together I'm sure we can handle it. :yes:

Bass localisation. The Plus2 is quite a compact source in comparison.
Keep in mind I will have the levels matched and I have a pair of Plus/2's. They are crossed over at 80Hz and these in the rear will be crossed over at 60Hz.

Phase-related response errors.
I've not experienced any problems with this thus far with the rear sub at 0 degree phase. I've tested it in 30 degree increments up to 180 degrees. I don't see how swapping subs will change this, but maybe I don't understand something I need to understand.

Have you considered placing the enclosure(s) in the garage firing through the wall into the HT?

You can have two widely spaced enclosures for a better bass spread without cluttering the HT.

Much greater freedom in design without worrying about finish.
That would be ideal, but I can't take up the room in the garage. The attics stairs fold down next to the outside of that back wall, so anything protruding into the garage would be a nono. Plus it's a small hallway to an outside door... I don't see that working, even though it would be nice. What would be even mo betta would be my wife allowing me to extend the room all the way through that hallway, but it would require moving the stairs and a whole lot more I just really don't wanna get into.


If the box is ported at one end with the driver at the other the physical separation of the sound sources might prove problematic for the nearest seats.
Because of NF seating, this was my first thought.. I'm thinking that orientating the port with the drivers might serve you best, but you don't have the height for a single.
There will be two drivers and the plan is to locate them 1/4 distance from each end...



It would seem like the simple solution to this is two discrete enclosures with a port for each one.



I believe Stevecallas stated I would need at least 260 effective liters and a 6" diameter port that is 31" long. Would this be correct for a 13Hz tune?

Speaking of tuning to 13Hz... is not the purpose of the port to augment the tuned frequency? If so, how is anyone going to localize 13Hz?

At any rate... would sealing off each driver for two discrete enclosures be the best solution?
 

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If the box is ported at one end with the driver at the other the physical separation of the sound sources might prove problematic for the nearest seats.
Speaking of tuning to 13Hz... is not the purpose of the port to augment the tuned frequency? If so, how is anyone going to localize 13Hz?
It's not that you would localise port output, it's that due to the length of the sub and your proximity to the drivers, the driver output and port output may not have had enough space to mesh by the time the driver output gets to your seat, and the driver output would be louder in relation. You could solve it by placing the edge of the sub where the port opening will be the same space from your seat as the center point between the two drivers. I'd probably face the port side towards the side wall corner too, keep it about 1' away though. Ideally such a sub would be a good 6' or so away from you, like say, in the front of the room where some other ones are :devil: , but I think you already covered that.

Keep in mind, 570 liters is pretty big :nerd:

I believe Stevecallas stated I would need at least 260 effective liters and a 6" diameter port that is 31" long. Would this be correct for a 13Hz tune?
No, the 260 liter, 6" diameter port that is 31" long would be for the more common ~15hz tune design. You'd have to do something like 320 liters and a 6" diameter port that is 35" long to get it to work with a single driver sub. That's definitely doable, but I don't see what you are gaining, as the ports would still be best firing out the sides.
 

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Discussion Starter #35
You could solve it by placing the edge of the sub where the port opening will be the same space from your seat as the center point between the two drivers.

I'd probably face the port side towards the side wall corner too, keep it about 1' away though.

Ideally such a sub would be a good 6' or so away from you, like say, in the front of the room where some other ones are :devil: , but I think you already covered that.
I'm not sure I have a lot of options, but it will all be around 6 feet from the main listening position, which is just in front of the steps you see in the pic below. The back row is generally where we put the kids that complain about reclining and they probably couldn't tell the difference one way or another... actually, I'm not sure I could tell a lot of difference... :dumbcrazy:

Here's an idea of what it will look like (excuse the old photo but it was the only one with no furniture in the room)...






No, the 260 liter, 6" diameter port that is 31" long would be for the more common ~15hz tune design. You'd have to do something like 320 liters and a 6" diameter port that is 35" long to get it to work with a single driver sub. That's definitely doable, but I don't see what you are gaining, as the ports would still be best firing out the sides.
I was only thinking it might make it better for the back row if we make it two enclosures... at least each port will be closer to its own sub... like this...

 

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Discussion Starter #36
How about doing away with the down-firing and have each sub fire out the side right beneath the port...



Would I lose any extension... seems like I read somewhere that downfiring gained some extension.
 

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If your own seating position is ~6' away, then I wouldn't worry at all. Two enclosures would definitely make constructing and moving the subs a lot easier. Downfiring won't add extension per se, but I often see it associated with smoother FR's in room. I think what you were referring to is when the baseplate is close to the drivers though, like with an SVS sub. The drivers essentally couple with that air between the baseplate and it acts to lower the Fs of the driver a bit. That's not necessary for this sub though.

Make sure you are taking breathing room for the external port opening into account as well - at least the diameter of the port, preferably more.
 

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Discussion Starter #38
Separating them into two enclosures seems to make more sense... although we will be cutting it close on the port clearance. The internal width could only be about 45" or so.... a 35" port tube will still leave us 10" of clearance.

As far as external port clearance... they should be about a foot from each angled side wall.
 

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Sounds like a plan is formulating. My thinking was that you sat in the chair that backs up to the sub/subs. We certainly didn't want your head a ft away from the port:dizzy:
The internal width could only be about 45" or so.... a 35" port tube will still leave us 10" of clearance.
Your good, I've built tighter in a pinch..10" is very doable.
 

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Discussion Starter #40
Sounds like a plan is formulating. My thinking was that you sat in the chair that backs up to the sub/subs.
We put folks we don't like back there... :devil: Just kidding of course, we actually don't let anyone we don't like in the room at all. :devil: :devil:
 
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