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change speaker port rear to front


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hi i have 2 old klipsch RF-# front speakers that are rear ported. i am building a 140" A/T pj screen and want to place speakers behind it but space is very limited.

 

basically speaker is 390mm deep with grills off and i have 470mm. is it possible to change the port around so it faces front? or will it be helpfull just to plug the speaker with a foam plug?

 

thanks

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In theory not too hard - is the port removeable?  I.e. is it something like a cardboard tube with a plastic horn that is pushed into the back of the cabinet?  If they were speakers I didn't care about I would buy a drill based hole cutting set, match up the size of the hole, cut it out of the front (mask off the veneer with paper masking tape so it doesn't chip).  Pull the vent out of the back, put it in the front and glue the plug you cut out of the front into the hole in the rear.  Builders adhesive or something that has gap filling properties would be best.  Finish with some no more gaps or similar.

 

In practice - might not be worth the effort depending on where the bracing (if any) is located in the cab, whether you can cut around it and where the port will end up inside the cab after it's moved.

 

I wouldn't just plug up the vent, the bass reflex designs are very carefully calibrated around that vent working.  The placement of the vent may be important as well - mucking around with it or plugging it could dramatically reduce the efficiency of the speaker at lower frequencies.

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6 hours ago, hopefullguy said:

is it possible to change the port around so it faces front?

It is possible but do not expect a good result.

It has been designed to have it work in phase with the driver and you may end up getting it out of phase.

In general, although accepted as "the truth", it is irrelevant whether the port is forward or backward firing as far as the placement of speaker in the room. I have seen Tannoy speakers with rear ports put 5cm from the back wall (in the shop) and still work brilliantly. It is a placement of the speaker in the room that really counts and what will work in one location might not in the other.

I know that most people will disagree with the above.

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If you are running a subwoofer then I'd personally plug the ports. This will reduce low frequency extension of course but it might actually help the mains blend better with a sub and will also tighten up bass response (ringing at low frequencies). 

 

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27 minutes ago, hopefullguy said:

reason for enquiry was due to only 80mm behind front speakers once placed in position next to pj screen.. no other placement options. just not sure if 80mm is any good but in the end no choice.

IMHO that is plenty of room.  You shouldn't need any more than about 20-30mm to not have an audible effect on the sound.   If they were flush against the wall...then you might cause problems.  Run an experiment maybe, use your hand and crank the bass on something and see how far you can feel the port choofing away away from the cab.  

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7 hours ago, hopefullguy said:

reason for enquiry was due to only 80mm behind

 

Don't plug the ports (or move them to front).....  Just run them with 80mm clearance.... that's your best bet.  I will be fine, especially if crossing over to subwoofers.

 

Re: Whether you can get away with moving them from front to back (which you shouldn't do) ..... the answer is mostly yes you can.   As long as you are keeping the port in the same area/end of the cabinet.... the distance to the driver is similar.... and the port isn't particularly large for the frequency range it operates at (ie. it won't leak high frequencies too much)

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