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redesigning low ports... (Read 2666 times)
Adrian D.
Ex Member



redesigning low ports...
11/16/05 at 17:04:35
 
i just had a thought about replacing the two round ports with a single slot port and maybe increasing surface area but keep the same tuning to reduce port noise when using subs with high x-max.  anyone ever did this/thought about this ? i think it should be real easy to model the low vented box using win-isd.  ???
i remember someone put 3 or 4 ports on a hwk-18 instead of the two.
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gexter
Ex Member



Re: redesigning low ports...
Reply #1 - 11/16/05 at 19:40:59
 
Why not?
the port is based on length and surface area. as long as it matches it should not be a problem.
If you ran a baffle about 2" from the bottom inside all the way to about 2" from the back you could really create a new world. Maybe start from a rough calculation in winISD
make the bottom rmoveable and adjust from there. start with it on the low side and close to the back and.
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« Last Edit: 11/17/05 at 02:55:29 by gexter »  
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Adrian D.
Ex Member



Re: redesigning low ports...
Reply #2 - 11/17/05 at 05:28:51
 
Quote:
make the bottom rmoveable and adjust from there

this way the hw becomes tunabale similarily to the db ??? sounds nice, but i haven't got any time for fun and my future project is replacing my particle board db-10 with an mdf one.
now, the second replacement... replace the top port with a slot one, so that the hw would appear as a tall box with two slots, one on top one on the bottom. someone said that if you don't get the top port perfectly centered, you can get port noise.  i guess that puting a slot just like on the bottom could ease things a little... BUT, is it possible to get phase problems by firing both top and bottom ports in the same direction ?
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gexter
Ex Member



Re: redesigning low ports...
Reply #3 - 11/17/05 at 14:54:53
 
no diffinitive answer on that.
but the square port is less likely to produce port noise.
and I would only guess that it would be less than ideal to have too differant tuned ports in the same direction, but honestly I just don't know.
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Adrian D.
Ex Member



Re: redesigning low ports...
Reply #4 - 11/17/05 at 18:37:29
 
but still if i'd want to build one i guess that it's worth a shot with the slot port...instead of the low ports  ???
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« Last Edit: 11/17/05 at 18:39:53 by adi_ro »  
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J_Rock
Ex Member



Re: redesigning low ports...
Reply #5 - 11/17/05 at 22:10:20
 
you'll probably run into phase issues in the upper frequencies, but nothing noticeable like comb filtering since the frequencies are soo low and wavelengths so LONG.
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JohnF
Ex Member



Re: redesigning low ports...
Reply #6 - 11/26/05 at 01:43:24
 
The bottom wouldn't be much of a slot since the current ones are only 3/4" long.  Also, the way Steve has them placed in the bottom corners affects tuning.  They are effectively longer ports.  I would also think that the placement in the plans helps improve the airflow vs a long skinny slot port.  Lastly the bottom is tuned much higher and I've never had a chuffing problem there even with imperfect circles.  I have had some turbulence problems that sandpaper cured easily.

I believe there is some benefit to the recommended top port placement and slight variations from center can cause problems, however, a totally different location such as the front shouldn't be a cause of problems.  I do think it will behave like a normal bandpass port with a major change.  There may be no difference, but I trust Steve and with the design.

Regarding tunable HWKs-  I've often thought of trying it, but with moveable driver baffles not changeable ports.  I'd be very interested in the effect of changing the size of the center chamber that way.
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gexter
Ex Member



Re: redesigning low ports...
Reply #7 - 11/26/05 at 06:02:04
 
John
do you think a person could build the HWK with a large extention on the side of the center chamber with a type of plunger to shrink and expand the chamber volume.

For experiment purposes of course, that and interchangable ports
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« Last Edit: 11/27/05 at 05:30:46 by gexter »  
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JohnF
Ex Member



Re: redesigning low ports...
Reply #8 - 11/26/05 at 20:05:15
 
Gex,

I think that would be a waste of effort because I doubt changing it would have much effect unless it was to make it much smaller.  On the other hand moveable driver baffles, like the DB, would make it infinitely tuneable because at the same time you would change the ported chambers volume which will directly affect tuning.
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DirtDawg
Ex Member



Re: redesigning low ports...
Reply #9 - 11/26/05 at 20:56:17
 
[quote author=JohnF  link=1132164275/0#6 date=1132969404]Regarding tunable HWKs-  I've often thought of trying it, but with moveable driver baffles not changeable ports.  I'd be very interested in the effect of changing the size of the center chamber that way. [/quote]

John,

About 2 months ago I built an 8" HWK and built a DB style moveable center chamber. I know I talked about it in another thread, but, I actually made the overall size 6" longer so I could tune (GOOF around with) it.

I ended up making the low chamber (top) only about 1 inch longer, since it tuned about right, but the tuning on the high chamber was way too high for my taste on my first attempt and 4 more inches was a welcome benefit. They were still tuned different enough to forget about the phase difference.

It would be fun to make the center chamber in 2 pieces that were both moveable and the box a bit larger to tune the whole thing lower and play around with the damping chamber also. All I need to do is remove the chamber and saw it in 2, but the baby HWK has been evicted from the bedroom system in favor of a very unusual WO, using 8 - 4" drivers that fits under the bed. There's just no way to stop this insanity. Undecided
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JohnF
Ex Member



Re: redesigning low ports...
Reply #10 - 11/27/05 at 01:14:31
 
Dawg,

How did you construct it to have a good seal and remain moveable?  I have some tubular motors and remote controls, so using threaded rods that the motors turn could make it tuneable by remote control.  Made out of plexi could result in something cool.  I just haven't wrapped my brain around the 2 separate moveable but sealed baffles.
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