Audio Logitech Z5300 - Fill sub with dampening material ?

M

mod-the-pc

Disciple
I have been using a logitech z5300 for a few months. The problem with the sub is that the bass is boomy and not tight. Will filling the enclosure with some sound absorbing material dampen the booms ? It is a ported sub with two "chambers" with the driver between the chambers. Which side of the driver (or which chamber) should be filled ? The speakers are out of warranty and I don't mind opening them.
 
what sort of dampening material do you have in mind?

What is the sub enclosure made of.

Try stuffing the port alone first , with foam or cloth :D
 
@Greenie: Noob question warning!!

will a soft stuffing in the ports really help? Won't the kind of force the material has to withstand make it unusable?

Will it be a good idea to minimize the port with some mdf sheet stuck and nailed to perfection and then cut out slowly as per the listener's taste?
 
greenhorn said:
what sort of dampening material do you have in mind?
What is the sub enclosure made of.
Try stuffing the port alone first , with foam or cloth :D
Click to expand...
The enclosure is made of wood (mdf ?). I'm planning to use corrugated foam like this one
corrugated_n_foam.jpg

Or will some other material be an ideal fill ?
@greenhorn & Chaos : will try closing the port by stuffing in some cloth.
 
between loud boomy bass and less but tight bass, I'd choose the latter :)

Try glasswool, or polyfill from pillows ( easier to get. Just buy a cheap pillow and rip it up ;) ) to stuff the insides
 
another n00b question from me...

Doesn't closing the port blow the speaker's diaphragm? The displaced air has no where to go right?
 
Kumar said:
another n00b question from me...

Doesn't closing the port blow the speaker's diaphragm? The displaced air has no where to go right?
Click to expand...

nope , it just makes it harder for the speaker to move , but the trapped air provides better damping , and reduces the boominess of the bass :)

but the volume levels will decrease a bit though
 
1. Glasswool + ported box = floor full of glasswool

2. Stuffing material + bandpass box = zero bass output.

Your only options are:

a. Placement. Moving the sub away from a wall can drop the bass output considerably, leading to less boom.

b. Equalisation. EQ can reduce the peaky output of a 4th order bandpass box like the one you have. The peak for such small woofers is usually in the 60-80Hz range, so some negative EQ (about 6db) with a parametric equaliser can even it out. Shoot for a Q of 1.5-1.8, a notch frequency of 65 Hz, and a null of about -6dB to tame the notch.

c. Level. Simply backing the sub level off will reduce the peakiness of the output. If your woofer does not have this control, then this option is not feasible. The MX5021 didn;t have it, but the Creative bass units all have a control for the sub level.
 
@greenie: damping a ported box may raise the box Q. It has the opposite effect in a sealed box. This also depends on the kind of material used.
 
low_bass_makker said:
Is it a band pass or a ported one.

Pluging the port will result in great loss in output
Click to expand...

Ditto,

The Z5300 uses a patented dual chamber subwoofer to pound out twice the bass of conventional designs to deliver deep, loud and powerful bass.
Click to expand...

I think that makes it a bandpass enclosure.
 
sangram said:
Glasswool + ported box = floor full of glasswool
Click to expand...

my sub doesnt spew glasswool from its port. I had the inner end of the port covered with cloth ( actually did it to stop things from getting in actually :p)

2. Stuffing material + bandpass box = zero bass output.
Click to expand...

wouldnt it just work as a sealed box of the same volume?

I've seen subs that came with foam bungs to seal their ports :ashamed:

i'm not even sure that the Z5300 is a bandpass anyway. Its claimed as both :p . I think the marketing types just got carried away
 
Technically, a bandpass box does not expose the driver to free air except through the port in one half of the box. If you seal the port, the driver motion never couples to free air and therefore you get no bass. I actually meant plugging the port, not stuffing the box.

Covering the port makes the port aperiodic, it's not ported anymore. Unless you use acoustically transparent material (and sometimes even then, as things change at low frequencies where we are also pressurising the air and not just using it as a transmittive medium) it is impossible to retain the acoustic property of the port.

Ideally just reduce the volume of the sub. That cures most of the boom. I also have a little 5.1 system with such a sub. Keeping the sub level down makes it sound bearable with music (the extra bass is always welcome for games though).
 
I'm not sure if the sub should be called a ported / band-pass one. The cross section of the sub looks like this

If I fill the sub with polyfill, which chamber should be filled? A or B or both ?
 

Attachments

  • Sub.PNG
    Sub.PNG
    1.4 KB · Views: 97
It's a 4th order bandpass box.

Stuffing to be applied to section A, if at all.

Stuffing the ported half will be counterproductive, unless you use open-cell foam. It works quite well, and has an expansion coefficient of about 1.3 which is not as good as glasswool or even polyfill. Dacron also works well, but is fairly loosely packed so is unsuitable for a ported enclosure.

Stuffing the box increases apparent box volume, which brings down the system Q and makes the bass 'tighter'.
 
Update:
@Chaos / greenhorn - I stuffed the port with cloth and there was total loss of bass. I guess I need to fill the enclosure as sangram/greenhorn suggessted. I'll try it out soon and let you all know
 
Back
Top