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Topic: Would adding a front ported sub to a rear ported speaker essentially m (Read 2683 times) previous topic - next topic
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Would adding a front ported sub to a rear ported speaker essentially m

Would adding a front ported sub to a rear ported speaker essentially make it front ported?


Let's say the crossover frequency is 160 hz, wouldn't the low frequencies that normally come out of the port in the speaker now be coming out of the sub and sub port?

Would adding a front ported sub to a rear ported speaker essentially m

Reply #1 –
At 160Hz, the port probably has very little effect. 

Since you (I assume) are not the speaker designer the only way to know would be to block the port and do some tests to see what happens.  Try it with the crossover (but without the sub) and if blocking the port makes no difference that tells you the port isn't doing anything above the crossover frequency.

The port affects the tuning of the system  (the speaker in the box) so it's not as simple as "what comes out of the port".

If you had the Thiele-Small parameters for the woofer (which I 'm sure you don't have), you could measure the box volume & port dimensions and plug them into speaker design software along with the Thiele-Small parameters to approximate performance with and without the port.  By comparing the two simulated frequency response curves you'd know where the effects of the port kick-in.

Would adding a front ported sub to a rear ported speaker essentially m

Reply #2 –
Quote from: Gintoh on
Would adding a front ported sub to a rear ported speaker essentially make it front ported?


Well if you closed the rear port, yes. The location of the port in a vented cabinet is not all that important. Rule of thumb is that you put it as close to the front of the bass driver, but there is actually quite a bit of latitude if you do crazy things like run relevant simulations or measure results.

If you base your conclusions on placebophile listening tests, lots of  luck!

Quote
Let's say the crossover frequency is 160 hz, wouldn't the low frequencies that normally come out of the port in the speaker now be coming out of the sub and sub port?


Doug hit it square on. A well-designed port is doing nothing audible at 160 Hz, and not a whole lot more at 80 Hz in most decent-sized speakers. The acoustic output of the port is low-passed by the duct that feeds it. The corner frequency of that filter is usually tuned to be just above the fundamental resonance of the woofer.

Would adding a front ported sub to a rear ported speaker essentially m

Reply #3 –
Quote from: Arnold B. Krueger on
Quote from: Gintoh on
Would adding a front ported sub to a rear ported speaker essentially make it front ported?


Well if you closed the rear port, yes. The location of the port in a vented cabinet is not all that important. Rule of thumb is that you put it as close to the front of the bass driver, but there is actually quite a bit of latitude if you do crazy things like run relevant simulations or measure results.

If you base your conclusions on placebophile listening tests, lots of  luck!

Quote
Let's say the crossover frequency is 160 hz, wouldn't the low frequencies that normally come out of the port in the speaker now be coming out of the sub and sub port?


Doug hit it square on. A well-designed port is doing nothing audible at 160 Hz, and not a whole lot more at 80 Hz in most decent-sized speakers. The acoustic output of the port is low-passed by the duct that feeds it. The corner frequency of that filter is usually tuned to be just above the fundamental resonance of the woofer.


So if I set the subwoofer crossover frequency at 80 hz, will anything be coming out of the rear port on the speaker?

Would adding a front ported sub to a rear ported speaker essentially m

Reply #4 –
Quote from: peterh on
So if I set the subwoofer crossover frequency at 80 hz, will anything be coming out of the rear port on the speaker?


Subwoofer crossovers aren't brick wall filters so the upper range  speakers will still be receiving significant input as low as 30-40 Hz and there will be something noticeable  coming out of the ports when playing heavy bass.  However, the output in the same range from the subwoofers will usually be significantly greater.