Down-firing port on a bookshelf speaker?

[BeeTL]

As long as the base of the speaker is elevated properly, is there any reason not to do it?

If not, what would be a good rule of thumb for port size vs elevation?

[cjd]

Re: Down-firing port on a bookshelf speaker?

That significantly limits placement options since the space between the bottom of the box and whatever it's sitting on forms part of the port volume and must be consistent. Why not just go front-firing slot port?

I'm not sure I understand your question about port size vs elevation.

[BeeTL]

Re: Down-firing port on a bookshelf speaker?

That significantly limits placement options since the space between the bottom of the box and whatever it's sitting on forms part of the port volume and must be consistent. Why not just go front-firing slot port?

I'm not sure I understand your question about port size vs elevation.

Sorry...imagine the speaker has stumpy legs on the bottom, kind of like a down-firing sub.

Relative to port diameter, how tall should they be?

[Jay1]

Re: Down-firing port on a bookshelf speaker?

You can put a base on the speaker so it wont matter where you place it.

[BeeTL]

Re: Down-firing port on a bookshelf speaker?

You can put a base on the speaker so it wont matter where you place it.

That's exactly what I'm referring to, although I think the throat horn may be more about marketing.

[cjd]

Re: Down-firing port on a bookshelf speaker?

That's exactly what I'm referring to, although I think the throat horn may be more about marketing.

For the most part, it is. If you build the base below, sure. It's a volume game. I'm not sure there are rules as long as it's enough space. Tuning is a bit tricky (easier to fiddle and measure and adjust than calculate effective volume.) But again, you could just slot port for a similar-ish look and no more or less space taken up.

On the sub I built with a 3" port, bottom firing, I have 1.25" clearance.

[billfitzmaurice]

Re: Down-firing port on a bookshelf speaker?

For the most part, it is. If you build the base below, sure. It's a volume game. I'm not sure there are rules as long as it's enough space. Tuning is a bit tricky (easier to fiddle and measure and adjust than calculate effective volume.) But again, you could just slot port for a similar-ish look and no more or less space taken up.

On the sub I built with a 3" port, bottom firing, I have 1.25" clearance.

It is tricky, but yes, you can calculate it so that the section below the duct exit is actually an extension of the duct. And true, the flared section in the pictured cab is purely cosmetic, for the benefit of shoppers who don't know that a port output is omni-directional and think that low frequencies need 'steering'.

[fastbike1]

Re: Down-firing port on a bookshelf speaker?

The general rule of thumb for the end inside the cab is no closer to the wall than 1 diameter. Might want to keep that in mind for your bottom exit.

[BeeTL]

Re: Down-firing port on a bookshelf speaker?

For the most part, it is. If you build the base below, sure. It's a volume game. I'm not sure there are rules as long as it's enough space. Tuning is a bit tricky (easier to fiddle and measure and adjust than calculate effective volume.) But again, you could just slot port for a similar-ish look and no more or less space taken up.

On the sub I built with a 3" port, bottom firing, I have 1.25" clearance.

A slot port will not integrate well with the design I'm imagining, as it would add complexity.

It is tricky, but yes, you can calculate it so that the section below the duct exit is actually an extension of the duct. And true, the flared section in the pictured cab is purely cosmetic, for the benefit of shoppers who don't know that a port output is omni-directional and think that low frequencies need 'streering'.

Are you implying Polk Audio may be less than sincere with their Power Port bass technology PR?

:p

The general rule of thumb for the end inside the cab is no closer to the wall than 1 diameter. Might want to keep that in mind for your bottom exit.

I was hoping for half the diameter, but making adjustments will be easy enough.

[Jay1]

Re: Down-firing port on a bookshelf speaker?

It looks like it extends the length of the port across a second flare. Does that actually reduce noise compared to a standard precision port? Who knows. One of their claims seams fairly accurate at least.

compact design to mimic the properties of what would be a very long flared port opening

The power port didn't have anything to do with why I linked that pic :D

[fastbike1]

Re: Down-firing port on a bookshelf speaker?

Several of the bottom ported builds I've seen look they used 1/2 diameter. Like everthing else in the build, it's a compromise. It will change the build similar to having a rear port up against a wall. We rarely have the perfect place to put a speaker.

I always think that having speakers in a room, no matter how compromised, is better than not having music in the room.

:p
I was hoping for half the diameter, but making adjustments will be easy enough.

[Chris Roemer]

Re: Down-firing port on a bookshelf speaker?

A slot port will not integrate well with the design I'm imagining, as it would add complexity.

Are you implying Polk Audio may be less than sincere with their Power Port bass technology PR?

:p
I was hoping for half the diameter, but making adjustments will be easy enough.

Top venting works great too.
1/4" "hardware cloth" around bottom makes it easier to extract HotWheels that "fall" in there.

[moron#99]

Re: Down-firing port on a bookshelf speaker?

You can put a base on the speaker so it wont matter where you place it.

is there a place to buy formed plastic cones like in that base?
I need that dispersion reflector thing for an omnidirectional outdoor speaker.
or maybe there is a better standard approach?