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-   -   PA bandpass cabinet (http://www.diyaudio.com/forums/pa-systems/9755-pa-bandpass-cabinet.html)

Bull 11th January 2003 05:05 PM

PA bandpass cabinet
 
To produce pure very deep bass for pa/disco i guess you need a bandpass cabinet.When i mean deep ,i mean 15hz-20hz lowest.
A suitable lowpass filter would cut off at 280hz.

I just bought an amazing book by EMINENCE
[High power loudspeaker enclosure design and construction]

There are two designs for bandpass. 2x 12 inch or 2 x15 inch using Beta 12,Delta 12,Kappa 12,Gamma pro 12,kappa pro 12,to chose for 12 inch cabinet.And Beta 15,Delta 15,Kappa 15,Kappa 15lf,Kappa pro 15,Omega pro 15.

The design is a 3 chamber ported bandpass design.
And I have decided to make the 2x 15 inch version using the Omega pro 15.

The Eminence book has some good pictures and designs,but the construction details or materials are not listed[except for the measurements.

Could someone please help me out on the following queries;

1. what wood do i use for the cabinet? MDF or plywood

2. What wood do i use for braces and battens?
MDF,plywood,partical board

3. Which way is better to connect the two bass drivers? in parallel,more power but lower ohms,or in series,less power given to drivers,more ohms.

4.Because the drivers are mounted inside the cabinet,the design has a removable back,how do I seal the back so that air does not escape through the joins?

5. How should i power them? using a poweramp of 800w rms min to drive the woofers,or a poweramp of 1600w rms,because both drivers if wired in series are total 1600w rms.

6. How do i make very strong corners and joints,because the subs will be used in a rough enviroment,disco,small hall or club,people might sit on the speakers and heavy speakers will be placed on top? I know Butt,and tongue and grove joints are used for hifi speakers,but what do pa speakers use the same method or something alse,maybe like standard corner reinforcement joint?

7..Last but not least, what parts of the 3 chambers should be lined with acoustic wadding?

If you can respond to these questions ,i will be gratefull.

BAM 12th January 2003 12:49 PM

PA woofers should be 8 ohms, usually. Wire them in series. Most PA amplifiers can handle a 4-ohm load on each channel.

In selecting your woofers, go to http://www.partsexpress.com and do a search in the search blank for eminence. then take a look at each picture of the drivers you are considering and choose the one with the beefiest magnet for the best results. A big, beefy magnet means that the driver can really move the air quickly and support long cone excursion. It can also stop and start the cone faster for quicker transient response in a large cabinet.

JBL 12th January 2003 01:11 PM

I d'ont thnik that any eminence loudspeaker will go down to 15hz. In fact I doubt that you will find many satisfactory speaker that will go down to that frequency.

You can get near, like 30 hz. And the crossover is to high for this application. The frequency of the crossover need to be at 100hz or lower in this design.

I would use plywood for pa speaker.

dub57m 18th September 2010 11:08 AM

Hi Ball
Did you build these Bandpass cabinets? If so, how successful were they?
Do they need a lot of watts to give the right balance with full range cabinets.
Cheers

DrBoar 26th May 2011 09:13 AM

1. MDF is good for permanent location, Plywood is much better if you will drag it around from place to place (does not break or flake, lighter and not so sensitive to wet conditions

2. Use hardwood, mdf and softwood is good for crossbraces only

3. seal with a thin butyl strip

I would not use any damping material in a box that is used below 200 Hz you only reduce the bass output.

Top Shelf 27th May 2011 04:30 AM

:) BALTIC BIRCH!!!! 3/4" ,braced about every 10"..... 15-20hz ? Dubstep? Pipe organ? Most club music bass is centered around 40-60 hz

DavidL 27th May 2011 10:31 PM

Why are people trying to talk to some one who posted 8 years ago? sheesh he last posted in 2008 also.

firechief 27th May 2011 11:54 PM

Quote:

Originally Posted by DavidL (Post 2586145)
Why are people trying to talk to some one who posted 8 years ago? sheesh he last posted in 2008 also.

Uhhhh - good point. Either the subject is still valid and folks are still looking for an answer, or someone dosent look at the dates:( This must be social networking at its best. Can we really talk to the dead for only $29.95?


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