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Top to bottom port design? (Read 3192 times)
HT-EXT
Ex Member



Top to bottom port design?
01/03/06 at 03:16:53
 
I want to experiment by removing the top port and putting four ports on the front of the HWK15. The top ports would be the same as the bottoms (4 x .75). How will this affect tuning and output(SPL)? Has anyone every consider designing some type of folded horn top to focus the energy into the room but still using the 6 x 8 port to fire into the horn? This horn could be attach or removed. That way energy could be focus into the room or focus up. THANKS for any HELP.
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Adrian D.
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Re: Top to bottom port design?
Reply #1 - 01/03/06 at 07:23:45
 
i asked about the low ports here.
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« Last Edit: 01/03/06 at 07:26:57 by adi_ro »  
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J_Rock
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Re: Top to bottom port design?
Reply #2 - 01/04/06 at 02:47:39
 
the top and bottom ports if the same size will decrease ouput since they will be 180 degrees out of phase at the resonant frequency if the drivers are wired in phase.

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HT-EXT
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Re: Top to bottom port design?
Reply #3 - 01/04/06 at 13:07:20
 
I have two DAYTONS with magnets in the center chamber and one speaker is out of phase. Will this cure the phase problem?
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Adrian D.
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Re: Top to bottom port design?
Reply #4 - 01/08/06 at 17:22:16
 
phasing problems are cured if one is out of phase.
my guess is that nothing bad is going to happen if you "play" with wiring to get the sound you like
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DirtDawg
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Re: Top to bottom port design?
Reply #5 - 01/08/06 at 19:39:16
 
[quote author=HT-EXT  link=1136261813/0#3 date=1136380040]I have two DAYTONS with magnets in the center chamber and one speaker is out of phase. Will this cure the phase problem? [/quote]

The drivers are facing in opposite directions. If they were wired in phase electrically then they would push against each other and each would damp the other's movement. I have read, on this forum, of someone (HB BASS I think) using that configuration to possibly help a pair of speakers that needed a smaller box.

With yours wired electrically out of phase with each other, they will move in unison. Since you have chambers on each side of the 2 drivers, which are moving as a unit, the pressure in the 2 chambers is out of phase with each other. By tuning each chamber to a frequency different from the other the out of phase condition of the chambers is sort of averaged and there is substantial output from one port while the other is not resonating. As the frequency changes, output will start to come from the second port while the first diminishes output.

So, you can't tune them to the same frequency and expect good results. Besides using only one frequency invites the "one note box" sound, which most of us try to avoid.
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HT-EXT
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Re: Top to bottom port design?
Reply #6 - 01/09/06 at 03:40:31
 
THANKS for the info. Is there any way to build a piece to attach to the top and focus the energy into the room instead of up. I am sure it would have to be angled, enclosed on both  sides but it's output volume would have to match the output of the 6 X 8 top port. I would not want to cut down the top port energy just push it forward. Would anybody have an idea to the volume or size of the scoop you need to use on top? Yes another dumb question.
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Adrian D.
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Re: Top to bottom port design?
Reply #7 - 01/09/06 at 12:50:53
 
try to put the box on a carpet, with the top port firing down in the carpet
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DirtDawg
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Re: Top to bottom port design?
Reply #8 - 01/09/06 at 13:41:58
 
[quote author=HT-EXT  link=1136261813/0#6 date=1136778031]THANKS for the info. Is there any way to build a piece to attach to the top and focus the energy into the room instead of up. I am sure it would have to be angled, enclosed on both  sides but it's output volume would have to match the output of the 6 X 8 top port. I would not want to cut down the top port energy just push it forward. Would anybody have an idea to the volume or size of the scoop you need to use on top? Yes another dumb question. [/quote]

Not a dumb question ..... you're just forgetting a detail and then over-thinking the issue.

The detail: those waveforms coming from your top port on a Housewrecker are longer than your room, most likely. Remember that the lower the frequency (longer the wavelength) the more the dispersion pattern resembles a perfect circle. Your room is already containing and directing much of the initial pressure wave from the cabinet. The only thing that will happen when you add something to the port is that the port volume will increase and the tuning frequency will be lower, creating an even more circular dispersion pattern.

If you turn the port into a horn there will be some focused energy near the port exit, but it will also be harmonically related to the horns cutoff frequency. In other words it would have to be LARGE to make the difference you're looking for.

One thing you might consider if you feel the impact is not adequate is that the room could be causing standing waves in your listening area to almost cancel completely your desired response. One way to test this is to simply move around the room, or better yet move your HWK around a little and listen in different areas. You will definitely notice a difference, but you might be able to improve performance in your listening area by moving the cabinet.

PS:
Many times bass traps can help by catching and reducing some of the reflected energy from the surrounding walls and reducing cancellations. Placing them can be as much fun as placing your speaker cabinet.
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« Last Edit: 01/09/06 at 13:56:14 by DirtDawg »  
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J_Rock
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Re: Top to bottom port design?
Reply #9 - 01/14/06 at 01:06:13
 
You could model the same type of ports int he upper chamber, i.e. 2 smaller circular ports facing out. Just figure out what the resonant frequency of the upper port is, then create 2 ports that resonant at that frequency.

if you want to disperse the upper port energy, you could levitate a cone above the port's center. This design is used often in omnidirectional speaker design:

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HT-EXT
Ex Member



Re: Top to bottom port design?
Reply #10 - 01/16/06 at 03:21:23
 
KILLER PIC!!! Thanks J-Rock that pic gives me all kinds of ideas. I did build a scoop that fits directly over the top port. I was able to get a +3db gain. This gain was focus at the listening area where it needed it the most. This also allowed me to unhook one of the HWK15 and now just the WO36 and one HWK15 is more than enough for the concrete bunker. THANKS for the help and keep the pics coming.
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J_Rock
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Re: Top to bottom port design?
Reply #11 - 01/16/06 at 03:37:59
 
I actually want to do something similar to the pic, but instead I am going to put a 10 inch woofer, then a very small and narrow cone with a tang Band full ranger in it.  

It will be somthing like a coaxial speaker, only the tangband isn't a compression driver and won't be firing through a voicecoil.

I also might try the same as the picture, with the tang Band firing up from within the large cone into a smaller cone.

If you had high enough sensitivity drivers, you could place one or two of the set ups like the picture in a room and be plenty loud.  Plus the whole directional aspect of a normal speaker is gone.  (well, theoretically it would work that well.)

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HT-EXT
Ex Member



Re: Top to bottom port design?
Reply #12 - 01/16/06 at 12:04:18
 
Do you know what size base for the cone you would start with and what length from the base to the point could be? Of course the combos can be endless depending on what type of tuning would be good for the room. Do you think the larger the cone area the lower the sound(Hz) will be or just better room loading. Let me know some of your ideas on HWK15 and cone combo. Thanks J-Rock.
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J_Rock
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Re: Top to bottom port design?
Reply #13 - 01/16/06 at 15:38:31
 
I think the main thing to play with and adjust would be the angle of the cones sides.  

Intuition would suggest a 45 degree angle with the horizon, but that may not be the case.  I have seen cones with straight sides with angles from 30 to 70 degrees of axis.  

As far as size, the cone in the picture is the largest I have ever seen in relation to the driver it is above.  The main thing I see is that the cones are generally the same size or larger than the source of sound. (excluding the cones with steeper angles, the cone would have to be very large) SO in the HWK case, the size of the top port or larger.  

Also, the cones are often not even straight, they curve inward. )(<----cut right there.

here are some pics of professional speakers:
http://www.cd-konzert.com/loudspeaker.htm

http://www.bolzano-villetri.com/

both are omnidirectional high end speakers, but give you an idea of what kind of things can be done to convert vertical soure to horizontal.
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