Ported & sealed 2-in-1 subwoofer...possible?

[rocko1290]

I would like to build a subwoofer that could serve as a ported and sealed subwoofer at once. The ported would be for music/movies and the sealed for music. How I would do this is by putting a threaded PVC pipe as the port, and for music I would screw a cap onto the port. First of all, would this make an airtight seal?

How do you think this would work out? This should save me the cost of having to buy 2 subwoofers and will keep me within my budget range.

[ocaukrell]

wouldnt the sealed version be a smaller enclosure than the ported ?
if so the easy way would be to built the ported enclosure with either a hinged or sliding internal panel that when swung/pushed into place closes the box down to the sealed size and blocks the port at the same time.
could use some sort of rod hanging out of the port hole.

[Ron E]

You'll want to use a relatively high Q woofer. I'd just stuff a sock or a rolled up old T-Shirt in the port to close it off. You could also fashion some sort of cork or foam plug and it would work fine.

[bungy]

I gave this some thought aswell..i couldnt see any reason why it wouldnt be possible...

i was thinkin of a removeable panel in order to adjust the volume appropretly..

In the end i am currently building just a sealed unit to see how it performs on movies and music then i might try building another box.

Thing is the driver and backplate are so expensive and the box only cost about 30 quid. so i figured get a sealed one working then try a ported and see what the difference is.

keep us posted.!..

[rocko1290]

Why would I need to adjust the volume for a 2-in-1? Do yall mean smaller volume for sealed and higher volume for ported?

Ron E when you say a high Q what kind of range are you talking?

What exactly is the Q? It was my understanding that it is boost?

Wouldn't a T-shirt or sock have air leaks? Would a PVC cap provide a leak-free seal?

[sYkboy]

I have a RSS315HF in 4.0 cuft ported to 22Hz. I was thinking of making a replaceable baffle with the ports mounted in it. the new one would be a box to insert in the larger one and reduce the volume by half.

Just a thought.

[rocko1290]

Also why don't ported enclosures have a q?

[Cal Weldon]

Originally posted by rocko1290
Why would I need to adjust the volume for a 2-in-1? Do yall mean smaller volume for sealed and higher volume for ported?

What exactly is the Q? It was my understanding that it is boost?

Wouldn't a T-shirt or sock have air leaks? Would a PVC cap provide a leak-free seal?

1. yes a ported is usually a larger box than sealed for the same driver.

2. Q: The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a system. In an impedance plot, a driver Q can be determined by how high and narrow the resonance peak is. A high, narrow peak indicates a high Q, while a lower, wide peak indicates a low Q.

Q't: The Q of a loudspeaker's suspension plus the load of the rear chamber in a 4th-order bandpass box.

Qes: The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a driver at Fs, considering only its electrical (non-mechanical) resistances.

QL: The Q of a vented speaker cabinet resulting from all of the box losses (acoustic weaknesses).

Qms: The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a driver at Fs, considering only its mechanical (non-electrical) resistances.

Qtc: The Q of a sealed loudspeaker considering both mechanical and electrical resistances.

Qts: The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a driver, considering both mechanical and electrical resistances.

(Q definitions taken from the PE site)

3. while the sock might leak, if stuffed correctly it is known as aperiodic loading and sometimes sounds as good as sealed. It's almost like fooling the driver into thinking it is in a larger box.

[rocko1290]

Originally posted by Cal Weldon
[B]

1. yes a ported is usually a larger box than sealed for the same driver.

Why is this? Does it have to be?

How much of a difference does it make having a sealed sub for music? Would you say it is worth the effort of making a 2-in-1 subwoofer?

[Cal Weldon]

Originally posted by rocko1290
Why is this? Does it have to be?

Apparently, according to the "rules"

[i]How much of a difference does it make having a sealed sub for music? [/B]

That's completely subjective. I am a fan of sealed woofers but in some installations I agree ported is better. Sometimes a bass horn is the answer. It's up to the listener and the environment.

[i]Would you say it is worth the effort of making a 2-in-1 subwoofer? [/B]

No, I think that introduces compromises. I think each woofer should be built to match it's environment, not the source material. If you need two different woofers, have you deliberately introduced compromises in them? Or, on the other side of the coin, are you optimizing the benefits of each?


Hint: There is no incorrect answer.