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Old 27th January 2013, 10:04 AM   #1
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Default Design of bass-reflex speaker

Hello to all:
Im new in this forum, and i am trying to desing a 3 Way speaker system, using VISATON Speakers.The tweeter and midrange it is a high end and the woofer it is a 10".
The question is, if there are any speacial position for the woofer in the enclosure. For example it important to place the woofer in the middle of the frontal box?, or perhaps it's better to place the woofer just 33% (33% over the internal lenght total of the enclosure) ,then over the center of the woofer the 66%.
it is possible to obtanin more cancelation of rebound waves in this position? i think the realtion between lenght,deep...and postion of the woofer it is important to cancel the waves of internal rebounds over the bass-reflex frecuency.
and the last question...the position of the bass-reflex..it's better behind or in front?

thanks for all
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Old 27th January 2013, 12:02 PM   #2
tvrgeek is offline tvrgeek  United States
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The woofer is the most tolerant. Download "The Edge" Its a little free program that lets you play with the position and size to see what effect it has in the response. As far as "rebound" I think what you are worried about is midrange reflections. You deal with that best by proper stuffing. Place the mid and tweet where you need them, and what is left is the best place for the woofer. For practical reasons, big heave magnets should be low to make it harder to tip over. This is one question you don't need to overthink.

Front or rear port? Well, if you are building a bookshelf to actually sit on a bookshelf, then front as the port does need air to port into. It is usually advised for a rear port to lessen the audibility of midrange out the port. With a port, there will always be some combinations of distance, cone to port, and position in the room that will cause some comb effects. Rear will tend to shift them down. So, the convention is woofer on bottom, port on rear top.
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Old 27th January 2013, 02:49 PM   #3
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Thanks for your answer. But,respect to the woofer position, the wavelenghts of the woofer produce are very long in comparation with the midrange, then the internal vawes reflections of the first rebounds are not important...but what happend with the 2 on or 3 rebounds of vawes? Then...the fase not be the same for the main vawe of the woofer.
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Old 27th January 2013, 03:01 PM   #4
balerit is offline balerit  South Africa
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Quote:
Originally Posted by danielgonzc View Post
Thanks for your answer. But,respect to the woofer position, the wavelenghts of the woofer produce are very long in comparation with the midrange, then the internal vawes reflections of the first rebounds are not important...but what happend with the 2 on or 3 rebounds of vawes? Then...the fase not be the same for the main vawe of the woofer.
Have a look here where I have minimized the phase distortion, if that is what you are referring to.
Mac
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Old 27th January 2013, 05:10 PM   #5
ODougbo is offline ODougbo  United States
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daniel, could use a lot more detail on your post.

Box size
Box shape
Drivers, etc.

If I were out to cancel standing waves - I'd look at a box with some angles; "boxes" always echo, 15 angles, sides, top, back or combinations can make a huge improvement (IMHO).
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Old 27th January 2013, 07:23 PM   #6
balerit is offline balerit  South Africa
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This is an old debate and one that in my opinion is a lot of baloney. A large room will have standing waves but a small loudspeaker enclosure will have minimal effect. A box shape is mainly designed for appearance, some people use the picture frame ratio but I use the square root of two. The placement of the midrange and tweeter in relation to the woofer is far more important.
Mac
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Old 27th January 2013, 07:57 PM   #7
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If you havent already, download and try Boxsim. It will model most Visaton drivers and you can use the 'driver position' and 'common outer housing' functions to tweak the driver heights and centre line offset and see the impact on frequency response and polar patterns.

Off course this is simulation using anechoic data, and room abberations arent simulated.

As others have stated, the midrange and tweeter positions will have a greater impact due to the wavelengths involved.
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Last edited by mondogenerator; 27th January 2013 at 08:01 PM.
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Old 27th January 2013, 08:05 PM   #8
balerit is offline balerit  South Africa
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Quote:
Originally Posted by balerit View Post
Have a look here where I have minimized the phase distortion, if that is what you are referring to.
Mac
Duh, I forgot to post the link:

http://novelbooks.weebly.com/photos.html

Mac

Last edited by balerit; 27th January 2013 at 08:30 PM.
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Old 30th January 2013, 05:34 PM   #9
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thanks for all the answers and considerations

ODougbo, the drivers are visaton Woofer : W 250 S8 Visaton
Midrange:G 50FFL Visaton (Dome)
Tweeter:G 20 SC Visaton
Respect to the box shape,and size it's 90 liters enclosure with 31 Hz bass reflex, and rectangular shape.
I like to cover the internal face of DM with sound absorbing material.

respect to the midrange an tweeter...it is important the position to cancel the rebound of waves if both drivers are type dome?

Thanks
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Old 30th January 2013, 06:52 PM   #10
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mid and tweeter baffle positioning is even more important using domes, since both mid and tweet are likely to have very wide dispersion. With a cone mid of 4 inches or more the problem is lessened but still a consideration.
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