Closed Vs Vented Enclosures

Status
Not open for further replies.
Jump to Latest
#21
system Q also applies to to vented boxes... hence the reference in the quote from Jon Marsh about the different types of vented boxes and the differing sound qualities.

An extreme example is an SPL-oriented box for car audio competitions... usually vented, designed with a huge hump in the response specifically to achieve very high SPL's in a certain constrained frequency range. One note bass is ever such a thing existed...

At the other end of the vented box system is huge EBS designs which have a shallow roll-off, very very low tuning, and come as close to sealed box group delay as you can get, going vented.

There is SPL and extension to be gained by going vented. There will also a price to be paid in terms of:

1) complexity of build
2) potential for error (fussier WRT parameters)
3) typically poorer integration with room... EBS subs are actually the very worst for this ironically. The extended shallow shelf means you get a large in-room "hump" in the lower end as room gain kicks in.

Given what I know now, if I did this all over I'd buy multiple cheaper 15" drivers (Dayton, Tempest classic, titanic MK III etc), and use either an LT capable plate amp or pro amp/BFD combo to simulate the LT cct... sealed. You gain huge spl because of the ganged drivers, and throw some away with the LT cct to gain extension and lowering of Qtc.

That's what I'd do, hindsight being 20-20

GB
 
#23
rollin24's said:
Ye thats so true, group delay doesnt mean anything as long as u got the aplication u want.....
anyways im gona use 2 peerless xls 4ohm drivers and i want it to be loud at about 20 - 45 hz since i listen to rap/hip hop music, but i also want sq so i think a vented enclosure will be good for this, but will the bass be as tight and as good as if i did a sealed enclosure?
Click to expand...

You haven't answered the application question. Nobody can thoughtfully answer your question until you do. Is it for car or home? How big of a car or room? How big a box can you tolerate? Is it the car or home version of the XLS? What are SPL goals, what will you power it with? IF you won't answer these, you will just get opinions. It would also help if you define what you think "tight" means. as it means different things to different people.
 
#24
richie00boy said:


It's a common misconception that LT means bad group delay. The GD is entirely based on what final Q is chosen.

Also excursion is identical regards specific SPL whether an LT is used not not (with a sealed box obviously). The only difference is what power is needed to reach the SPL - smaller box means more power.
Click to expand...
Hi richie00boy,

Re group delay, I was only going on the stuff posted on the linkwitzlab site, which seems to indicate that.
As my boxes roll off at about 12dB/octave (or less), room gain tends to boost the bass enough for me not to have to bother with any additional low-end boost.
LT is spoken of as a high-pass, but it looks like it still has 12dB boost at 10Hz, which might be good for some, but would probably break my poor little woofers at higher volumes.

A 12dB high-Q, high-pass just below resonance for a BR should avoid most of the excursion problems associated with such boxes - but may not provide as 'good sound' as a sealed box of similar volume.

So, Rollin24's - is it for car or home🙂?
 
#25
car(ford fairmont ghia xe) about a 150 liter box i sed the 4 ohm version of the xls so i referd to the car version, im gona use 2 of them and about 1000 watts rms (the mtx 92001 monoblock amp) and the goal is bass extention to about 20hz (-6db) and when i say tight bass is mean fast reacting bass
 
#26
In that case, go sealed and you won't need a 150 Liter box. I don't like vented boxes in cars, nor do I like them for high powered systems where they are likely to be abused and not have a highpass filter.

Since you like rap, go for a Qtc of 1.0 or so..... It'll be fine because the cabin gain will give you response way lower than the speakers F3 into halfspace.

BTW, bass is not fast, treble is 😉
 
#27
no see the thing is wateva i do, im still gona get a 150 liter box because im doing a fibreglass enclosure, takes up all the room 🙂 and im gona cut the sub of at about 80hz anyways with a low pass filter and a subsonic filter at about 15hz
 
#29
Cloth Ears said:
Re group delay, I was only going on the stuff posted on the linkwitzlab site, which seems to indicate that.
Click to expand...

As said GD depends only on final Q.

Cloth Ears said:
As my boxes roll off at about 12dB/octave (or less), room gain tends to boost the bass enough for me not to have to bother with any additional low-end boost.
Click to expand...

Yes that can be the case, no issues with that it works great.

Cloth Ears said:
LT is spoken of as a high-pass, but it looks like it still has 12dB boost at 10Hz, which might be good for some, but would probably break my poor little woofers at higher volumes.
Click to expand...

This is where everybody makes the mistake - they see the boost and think ooh added group delay and phase errors, and lumpy response. Think of it as the LT provides negative GD to bring the final GD and amplitude into line with what the designer wants (assuming they design for lower Q than the plain box has).

Cloth Ears said:
A 12dB high-Q, high-pass just below resonance for a BR should avoid most of the excursion problems associated with such boxes - but may not provide as 'good sound' as a sealed box of similar volume.
Click to expand...

Yes I agree.
 
#35
For a single driver in a closed box:

For Q=0.7
Volume=18 l
fc=66 Hz

For Q=1
Volume=8 l
fc=94 Hz

For two drivers side by side, double the volume. For two drivers in an isobaric configuration, halve the volume. The fc stays the same.

When considering the fc, also consider cabin gain.
 
#36
yeh i just checked it out on bass box its pretty good when the cabinet gain comes in, although the thing is i want bigger sound thats y i want to go with the vented enclsoure, u got any good ideas for that at about an fb of about 23hz??, i was thinkin of a 150 liter box, but y isnt that any good
 
#37
You can always add material to the inside of your fiberglass box to lower the internal volume. We've done things like soak household fiberglass insulation in fiberglass resin and place it inside, fiberglassed in MDF for added strength and a section we can mount things to.
 
#38
Closed V. Vented Subs

Personally, I really, really like my mains with the 10" base driver and a passive radiator (making the mains vented, but with double the speaker surface area) ... But for the sub woofer, my totally sealed box really does hold up in the very low freqs.


" sealed boxes have typically MUCH lower group delay, and usually sound far tighter and more musical. ... " - GreyBeard1

" Vented and closed speakers have a different sound. It is hard to explain to one who has not heard several different sealed and vented speakers in the same room. ..." - Ron E.

I agree with these guys.
 
#39
yeh but the xls is *recommended* for vented boxes, it wont play deep in sealed box, in fact in a sealed box it will roll of at about 80hz but in a vented it will rolloff at 21hz depending on box size... ure subs play deep in a sealed cauz there optiomized for that............. can u plz tell me y a 150 liter box is no good, i thought the bigger the box the better
 
#40
rollin24's said:
when the cabinet gain comes in,
Click to expand...
That's cabin gain.

rollin24's said:
it wont play deep in sealed box, in fact in a sealed box it will roll of at about 80hz
Click to expand...
Not with cabin gain.

can u plz tell me y a 150 liter box is no good,
Click to expand...
The low bass roll off will hold on longer but the middle bass levels will suffer, sim it and see 🙂 Also, power handling will be reduced.

i thought the bigger the box the better
Click to expand...
Not with this type of driver.
 
Status
Not open for further replies.
Top Bottom