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Multi-Way Conventional loudspeakers with crossovers

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Old 6th May 2012, 06:51 PM   #11
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IMO, the box is about the right size and needs to be tuned to about 57 Hz. You need to keep the port sized to avoid air noises. You might need to put a right angle in the port tube for it to be long enough. The response will be about -3 dB at 52 Hz, and that's the best and flattest this driver is apt to do. The port could be 2" by about 5 and a bit inches long. If you make it larger, the required length will be impractical. Did you measure the T-S parameters yourself after some break in? Manufacturers are pretty good about the numbers these days, but I still like to confirm them. Trust but verify!
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Last edited by Conrad Hoffman; 6th May 2012 at 06:54 PM.
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Old 6th May 2012, 07:21 PM   #12
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Will try to change tuning fequency and see what happens.

I didn't mesure TS parametrs, but all mesurments are done after brake in.
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Old 7th May 2012, 03:39 AM   #13
mdocod is offline mdocod  United States
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Quote:
Originally Posted by pk2carlos View Post
Idea is to be used as a full range.
Then an enormous oversized hole in the box is acting as an unnecessary opportunity for resonances from the box/port and sound energy from the rear of the driver making their way out of the box.

Quote:
In theory the port should be as big as loudspeaker
According to what? A port as large as the speaker is actually rather unusual unless you are trying to build a transmission line. In this case, the driver being used has absolutely no need for such an oversized port. The very large diameter and short length is not tuning the box correctly for full range use.

Quote:
and since there is enought space I decided to use this one.
Port diameter and length is something that is best determined through simulation. Not a "whim."

Quote:
I don't think that smaller diameter would make any differenc or would it?
Smaller diameter of the same length would be a lower tuning, which is what this box needs if you want it to have a well behaved bass response.

Quote:
Wouldn't it be only shorter for the same tuning?
I can't come up with any reason that you would want to keep the tuning that you have in play right now, it's resulting in a nasty peak in response that is worse than the lull in response that this thread was started in regards to.

I would switch to a 1.5" diameter x 4-5" length, or 2" x 8"

Regards,
Eric
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Old 7th May 2012, 07:25 AM   #14
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Quote:
Originally Posted by mdocod View Post
Then an enormous oversized hole in the box is acting as an unnecessary opportunity for resonances from the box/port and sound energy from the rear of the driver making their way out of the box.
Could this realy be that big of a problem? But yes this idea did cros my mind.
I have damping fome and syntetic wool inside, so I don't think that is a problem, will mesure also the port and see what is geting out of it :-)


Quote:
According to what? A port as large as the speaker is actually rather unusual unless you are trying to build a transmission line. In this case, the driver being used has absolutely no need for such an oversized port. The very large diameter and short length is not tuning the box correctly for full range use.
As far as I know the surface of port should be equal or at least half of surface of driver. This is to avoid any noise created by port itself. I know that because of limitations of design this is rearly used, but I think I can use that size of a port and live with this design.



Quote:
Port diameter and length is something that is best determined through simulation. Not a "whim."
Smaller diameter of the same length would be a lower tuning, which is what this box needs if you want it to have a well behaved bass response.
I can't come up with any reason that you would want to keep the tuning that you have in play right now, it's resulting in a nasty peak in response that is worse than the lull in response that this thread was started in regards to.
The reason for high tuning frequency is as said before to be able to get out more from this driver in relation to cone displacment. The idea is to have port tuned at Fs of the driver. The simulation didn't look that problematic.
If you look at mesurmet you can see a prfect impedance respons, I only wish that response could be the same.


Quote:
I would switch to a 1.5" diameter x 4-5" length, or 2" x 8"
Regards,
Eric
Thanks, will try diffrent port and see or rather hear what happens
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Old 7th May 2012, 08:35 AM   #15
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I think you absolutely need to download Unibox and play:
Unibox - Unified Box Modeler Loudspeaker Design Software
This will help you answer the following questions:
1) What changes in the FR when changing tuning frequency
2) What will be the maximum power used before the driver reaches its xmax
3) How long a tube should be in relation with its diameter vs the tuning frequency
4) What will be the air speed in the tube

Ralf
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Old 7th May 2012, 09:32 AM   #16
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I'm using boxsim which is also very good and has already imported visaton drivers database Boxsim - Homepage

Where in Unibox do you see air speed in the tube, since I can't see it on link that you gave. Is there more to this software than it is shown on link?
I just don't want to install all programs that are available and than use it only once.
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Old 7th May 2012, 09:56 AM   #17
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As this deep presents in both configurations, vented and sealed, I donít think the port can be blamed. It might be room mode or reflections from nearest wall or what else is used as microphone stand. Also , if there is too big measuring resistor connected in series ,the resulting Qts will be higher and you could observe something similar.
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Old 7th May 2012, 10:04 AM   #18
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Unibox is specialized in low-end tuning (closed, reflex, radiator). Easy and powerful for what it does. You fill data in the first sheet and see detail on another sheet.
For example FR:
Click the image to open in full size.
or air speed:
Click the image to open in full size.
or cone excursion:
Click the image to open in full size.
Start with 1W as Nominal Power of the driver, see the FR, and only then increase the power to check air speed and cone excursion.

Ralf
Attached Images
File Type: gif unibox_response.gif (23.9 KB, 162 views)
File Type: gif unibox_airspeed.gif (22.3 KB, 163 views)
File Type: gif unibox_excursion.gif (21.2 KB, 108 views)
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Old 7th May 2012, 10:24 AM   #19
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Thanks Ralf, I tried to download it and download doesnt work.

Is this like worksheet for excel?
I use open office and don't know if works in open office.
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Old 7th May 2012, 10:27 AM   #20
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Quote:
Originally Posted by Moon Track View Post
As this deep presents in both configurations, vented and sealed, I donít think the port can be blamed. It might be room mode or reflections from nearest wall or what else is used as microphone stand. Also , if there is too big measuring resistor connected in series ,the resulting Qts will be higher and you could observe something similar.
It is probably the room that makes this kind of respons. For mesuring I use ATB pro so I think there isnt a problem and a proper mic stand, all of this shouldn't make any difference at 147 Hz.
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