[freerider]

So this is what I'm thinking.  I had to go with 4 - 4" diameter, 14.25" long ports, since 8 ports would just look weird.  This should be the same port volume as 8 2" x 6" tubes.

Let me know what you think.



back side

[gprro]

I'll take a crack as this one, I'm up late anyway, if you're designing away right now don't get too far. For a 6.76 cu. ft enclosure, 4 4" diameter ports would have to be much longer to tune to 33hz, somewhere around 15.5 inches long I think(quick calculator on my iPhone) so not 100% sure, but they would have to be much longer. It's not just the total port opening area, it's each ports opening area in relation to length, tuned to the enclusure volume, per number of ports. Larger diameter ports need to be longer to tune the same as smaller ports. The amount of ports can also change tuning vs. total port area by lenght.

I think there's also something to be gained in low end extension by aranging the woofers in a long line. A square box might not go as low. Admitedly I've had a couple beers so I could be off on that, but not too far  Should still make a quick punchy sub. If they're suitable drivers, you could make a few 1/4 horns or tapped horns, although it gets much more complicated...long story short, the design would work, but you may lose a little extension, and you'll need longer ports.

[freerider]

I'll take a crack as this one, I'm up late anyway, if you're designing away right now don't get too far. For a 6.76 cu. ft enclosure, 4 4" diameter ports would have to be much longer to tune to 33hz, somewhere around 15.5 inches long I think(quick calculator on my iPhone) so not 100% sure, but they would have to be much longer.

Yup, you are correct.  They would need to be 14.25" for an Fb of 33Hz.  Goes to show what I know about speaker design.

I edited the post.

What I don't understand is how I'm going to get mid 20's in a room, when my speaker SW tells me the F3 for this design is 40.21Hz? 

[Danny Richie]

I think there's also something to be gained in low end extension by aranging the woofers in a long line. A square box might not go as low.

This is correct.

A single woofer or a tight group will hit a -3db of 35.6Hz by the numbers.

A line of 8 or them will get you a -3db of at least 6Hz lower. A line of 12 of them will get you about 9 or 10db lower.

[freerider]

What causes the difference?

[turkey]

Could you possibly build a cabinet and put it on top of your equipment cabinets? It would be wide and not very tall. In essence, a line array turned on its side and crossed-over as a sub.

Another option might be to put it under your equipment cabinets. I don't know if this would raise the TV up too high for comfortable viewing or not though. You'd also need to build a really sturdy sub enclosure if done this way.

[freerider]

Sorry for the grainy picture, but as you can see here, I'm very limited to what I can put where.

I can't put anything under or above my entertainment cabinet.  It just wouldn't look good enough to pass the WAF.

About all I have the 'permission' to do, is replace the end-table (with a subwoofer box) by our couch.

[Danny Richie]

What causes the difference?

The way the longer wavelengths couple.

[dvenardos]

What if you build the line array and put it where the MFW-15 is and move the MFW-15 to where you wanted to put the new sub?

[freerider]

A single woofer or a tight group will hit a -3db of 35.6Hz by the numbers.

A line of 8 or them will get you a -3db of at least 6Hz lower. A line of 12 of them will get you about 9 or 10db lower.

Then I guess that when I finish my LS6's, they will go lower than this franken-box I'm designing?

I hope this will be a worthwhile effort in the end...

[freerider]

What if you build the line array and put it where the MFW-15 is and move the MFW-15 to where you wanted to put the new sub?

Thanks, that's a good idea, and half of what you said will likely happen.  The MFW-15 will get replaced with the new sub box, because the new box will be so ugly (depending on your POV).  But since there are two windows, and curtains, and a surround speaker in the corner where the MFW is now...there wouldn't be room for a line array standing on it's end.  Primarily, it would obstruct the windows somewhat.

[dvenardos]

  What about if you laid it on its side, made a coffee table out of it, and put it in front of the couch? You could make a really nice piece of furniture out of it. It doesn't seem worth it if you can't make a line array out of it.

[Danny Richie]

Then I guess that when I finish my LS6's, they will go lower than this franken-box I'm designing?

Yes it would.

[chlorofille]

A line of 8 or them will get you a -3db of at least 6Hz lower.

Any difference in the low bass if the enclosures were built by :

1. Each woofer having it's own enclosure OR
2. All 8 woofers sharing one long, tall enclosure, braced of course with a single top firing port.

[Danny Richie]

Any difference in the low bass if the enclosures were built by :

1. Each woofer having it's own enclosure OR
2. All 8 woofers sharing one long, tall enclosure, braced of course with a single top firing port.

Ported and tuned the same they will be the same. You have to be careful using one port with all those woofers to make sure they are loaded the same. Otherwise the ones nearest to the port will be loaded differently than those further away from the port.

[Beatcoaster]

What about a wedge shaped box behind the couch?

[freerider]

Not a bad idea, but the layout picture is a little off.  My couch actually has a vertical back, so I could put a thin box back there, but the woofers would fire directly into the couch, with almost not gap between them.  I wouldn't want to pull the couch away from the wall, far enough to have the woofers fire upwards.  I'd lose 8" to 10" of room that way (and the 100" curtains I just bought and hung for my wife would have nowhere to go except on top of the box.)

[Danny Richie]

Do a line source design. Stand it up next to the couch. Let the woofers fire down the wall that the fireplace is on and let the ports fire off into the corner. This will really increase the output of the port because it will couple with the corner and wall. You can then tune it lower and get added output at the tuning frequency. By doing this you might get a -3db down in the 20Hz range.

[freerider]

Thanks Danny.  Maybe this picture will help.  Honestly, I don't get some twisted pleasure shooting down everyone's ideas, it's just that there is no way, on God's green earth, my wife will approve a monolith blocking our windows, or any other portion of the room.  Don't get me wrong, I'd love to crank out a line source woofer, for the fun of it, but I just don't have the flexibility to make it happen in this room.



So, with the line source off the table, it doesn't sound like the box version I drew up is a worthwhile effort.

Maybe I should buy a couple Neo 8's or dome tweeters, and make some bookshelf speakers instead?

[ebag4]

Just one more line source sub idea for you to shoot down  .

What if you put short legs on the back of the enclosure and laid it down with the drivers firing up?  Would it push your couch out too far to make it meet the WAF?

Best,
Ed