Discussion about ported bookshelves/towers with sealed subwoofers

Hi,

There's alot of sealed subwoofer lovers around here and everywhere else. I guess the group delay caused by a ported subwoofer is a lot irritating to them.

I also see that a good portion of those are using ported bookshelves/towers speakers, to extent the bass response they say, to use a lower crossover on the subwoofer.

If they can hear group delay on a subwoofer tuned at 25 Hz for example, why they can't hear group delay on a bookshelf/tower tuned at 80 Hz?

It seems pointless to me to use a ported bookshelf/tower if you want to avoid the group delay problem caused by ported subwoofers.

I want to know if I'm missing something? I mean if you tune around 80 Hz, an instrument playing at that frequency will be almost two full cycles behind other frequencies.

It's a strange behavior IMHO, but maybe I'm plain wrong and I would like to know it if it's the case.

I hope to get alot of opinions on this!
Thank you very much!
 
Plug the port with some open cell foam, turning your bass reflex port into an aperiodic vent. Next best thing to sealed bookshelves. Group delay can be offensive in subwoofers but it is even more offensive to most when it occurs in the midbass. It's generally accepted that if you have a subwoofer, you want to plug the vent on your main speakers.
 
Hi,

There's alot of sealed subwoofer lovers around here and everywhere else. I guess the group delay caused by a ported subwoofer is a lot irritating to them.

I also see that a good portion of those are using ported bookshelves/towers speakers, to extent the bass response they say, to use a lower crossover on the subwoofer.

If they can hear group delay on a subwoofer tuned at 25 Hz for example, why they can't hear group delay on a bookshelf/tower tuned at 80 Hz?

It seems pointless to me to use a ported bookshelf/tower if you want to avoid the group delay problem caused by ported subwoofers.

I want to know if I'm missing something? I mean if you tune around 80 Hz, an instrument playing at that frequency will be almost two full cycles behind other frequencies.

It's a strange behavior IMHO, but maybe I'm plain wrong and I would like to know it if it's the case.

I hope to get alot of opinions on this!
Thank you very much!

Group delay effects are audible proportional to the volume. If you have a bookshelf speaker tuned to say 55hz and add a subwoofer. Typically, you'd crossover in the 80-120hz area. The group delay of that 55hz signal is going to be less noticeable if the bass end of your bookshelf speaker is rolling off at 12dB/O and the subwoofer(s) are taking up the slack.(even less noticeable if a sock is stuffed in the port too :) ).
 
Why are so many speakers ported on the market if they know we need to add subs anyway? Why don't they just make the speakers sealed?
Because they sell and most buyers have no clue.
It looks better on paper; lower and louder; the lesser SQ is not in the specs.

IMO SQ is most important and ports are a mistake (also for subs); just use more boxes or horns if it needs to be lower/louder.
 

eriksquires

Member
2013-05-10 4:11 pm
I have a sub I can plug or unplug as the case may be. Whatever this group delay thing is, I can't hear it.



What I can say is that integrating a speaker into a room is difficult, and the lower in frequency you go, the harder it gets. Plugging ports IMHO doesn't so much affect the audibility of any group delay, but raises the lower cut-off frequency, making those issues less likely to happen.



My own opinion:



Use bass traps



Use EQ on the sub.



Treat the sub as part of the main speaker. By this I mean perform all of the time/phase/amplitude analysis you would as if you were designing a multi-way speaker/crossover.



Design your sub to peak at 16-20Hz and roll down about 1.25 dB/octave.



Magnificent with movies or music.





Best,




E
 

Zvu

Member
2009-01-15 6:52 pm
Belgrade
Answer is port noise and port resonance.

In a booshelf/floorstanding loudspeaker tuning frequency is usually higher, 35-55Hz. Port noise with right choice of woofers can be avoided. With subwoofers it is different matter. They need long excursion and are tuned much lower with port resonance frequencies that gets in to critical lower mids and turbulence gets bad no matter how good the port flare is designed. Port noise and port resonance are much more offensive to the ear than group delay. That's why subs need to be PR or closed.

Ported subs in home are just wrong. Bars and clubs are different matter of course.
 
Last edited:

Zvu

Member
2009-01-15 6:52 pm
Belgrade
Zvu,


Aren't you basically talking about lowering the port velocity? That is, using a big enough port that velocity is lower and therefore less likely to rub the port the wrong way??


Best,


E

Port air speed and port resonance - two separate things.

Velocity is lover with larger port surface but then the port gets longer which in itself lowers resonance frequency of the port tube that gets too close to operating band so it needs very steep low pass filter. 24dB per octave isn't good enough for that.