So why are sealed boxes so unpopular?

It's the designer's choice

You as the designer have control over all of the factors you mention. A sealed box (for a given driver) is the safe (read easy) option, and it inherently has quite good sonic quality. But it also yields less low frequency output. In this region the BR box is more efficient. Above resonance it has less distortion (in fact, at resonance it has quite low excursion).

But the overall result is in the hands of the designer. You must decide the alignment (LF response). If you give it maximal flat response, group delay will be high, and room gain will cause the bass to be exaggerated (unless you listen in a massive room); you may have to place it away from any boundaries.

A BR box can give you a nice tight bass sound, but it requires a bit more work, and is also much more prone to boundary reinforcement effects.

I don't believe it is a black-and-white issue. Sealed enclosures can sound bad, too. It all hinges on what alignment you choose.

My 2c
 
I didnt think that sealed were unpopular in the DIY sector, lots of people seem to use them or say they are going to.

In the consumer market lots of it is about whose goes deepest and loudest so ported makes good marketing sense. Its funny however that all sealed speakers, in reviews, are always given really good reports on how good their bass is.
 

RJ

Member
2004-10-19 4:29 pm
Order of preference using 2 Dayton 8" Classic woofers;
1. ML-TL - smooth & tight bass, really clear & clean sounding. Doesn't sound like a $22.00 speaker and it had punch!!!
http://img.photobucket.com/albums/v641/rjakubin/StuffedTL-1.jpg
2. Dual-Chambered Ported Enclosure. Deep Bass with lots of Growl. Most excellent for Rock, Dance & Hip-Hop. Lots of punch. As diysubwoofers state this box is great for low Xmax woofers and no fears of below resonance cone destruction.
http://img.photobucket.com/albums/v641/rjakubin/Dual-ChamberReflexBox-1.jpg
http://www.diysubwoofers.org/prt/dual_chamber.htm
3. Closed box. Sounded OK but just not deep enough & no punch
4. 4th order Bandpass - Drums sounded great but no punch and sound quality was a little muddy.
5. And last, a ported enclosure. Musicians sounded like they were playing in a cave.
 
David Gatti said:
Vented boxes are more complex,]
True, you need to drill one more hole, but I think it's not that much more complex.

produce excessive excursion below resonance (especially important in HT),]
True, but you can tune below 20 Hz to bypass this problem.

greater group delay (poorer transient response),]
Same as above.

produce chuffing and other noise,]
Same as above and also with vent speed under 17 m/s, not noticeable.

need bigger boxes,]
IMHO, not true, to achieve the same deep bass, the sealed box would need to be way bigger than the vented box.

reduce baffle strength (due to extra hole),]
True, but negligeable.

and integrate poorly with room gain.]
The sealed box rolloff is always too fast versus room gain, unless you're in a car. You can easily tune the rolloff of a vented box to integrate perfectly with room gain.

Can someone remind me as to why they're so popular? [/B]
All of the above and also like people said, the high efficiency.
I would like to add the deep bass you get by tuning under 20 Hz is better in HT also. LoTR and the like will never be the same.

There's the FR curve of a ported subwoofer I built, in a room. It's not at maximum power (but near) and it's not in a corner. The person I sold this to will make me soon a new curve with the subwoofer corner loaded at maximum power.
 

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RJ said:
5. And last, a ported enclosure. Musicians sounded like they were playing in a cave.

I've never heard a ported loudspeaker that allowed the bass player to sound like he/she was playing in the same room as the rest of the band. There always seems to be a disconnect between the perspective of the low frequencies and the mids/highs.

There was one speaker that I had that did seem to get it right though - Dahlquist DQ-16. This was a ported enclosure that was sopposed to have a quasi-bessel alignment that allowed the bass to roll off at 6dB per octave like a sealed box. Additionally, the speaker was sopposed to look like a purely resistive load to the amplifier. Wish I could figure out what the designer (Carl Marschiotti (sp)) did.

Thanks RJ, now I'm gonna have to build a stuffed TL just to hear how it compares to AS speakers :)
 
Ouroboros said:
A sealed box integrates much better with 'room gain'.

A ported enclosure rolls-off at 24dB per octave, a sealed box rolls off-at a much gentler 12dB per octave.

Yes, if you look under the tuning point. But if you look higher than the tuning point it's another story. You can tune it in the 15-20 Hz and the rolloff is a nice 2 dB per octave from 15-20 Hz to 80 Hz or more.

The sealed subwoofer will always rolloff faster than room gain can climb.
 
simon5 said:


Yes, if you look under the tuning point. But if you look higher than the tuning point it's another story. You can tune it in the 15-20 Hz and the rolloff is a nice 2 dB per octave from 15-20 Hz to 80 Hz or more.

The sealed subwoofer will always rolloff faster than room gain can climb.

What you are saying makes perfect sense when using large drivers in large cabinets that are going to play LOW.

But back to 99% of speaker land where 5-6.5" drivers are used, and you can nolonger use this as an advantage. Yes with a 10-12" bass driver you can tune to 20hz and keep group delay low, but in a situation where tuning lower means 50hz instead of 70, you can nolonger keep GD as low as a sealed box.
 
Alot of us are willing to compromise quality [slightly]

I dont go sealed because Id need 2 DPL12s to get the output I have now.And shipping those over here would cost too much.

Also for high SPL usage,tiny sealed enclosures with high excursion drivers produce excessive 2HD[see linkwitzlab.com 'thor']

People probably pick out ported vs sealed due to response differences rather than time domain problems[show me the outdoors tests!]

The fact is that ported boxes dont HAVE to go deeper than sealed,but because we tune them like that,they MUST sound worse.
 

ThorstenL

Previously: Kuei Yang Wang
Konnichiwa,

David Gatti said:
Can someone remind me as to why they're so popular?

More BASS for BUCK.

Same principle as McDonalds/BurgerKing "Supersize" meals, if we feed you [email protected] we can at least feed you a lot for little money....

And DIY'ers tend to define themselves by commercial designs (guilty as charged myself BTW).

Sayonara
 
So far I'm not convinced of any real benefit of vented boxes, unless you have a very large and loud system.

Another thing is that a 2nd order roll-off is a better match for subwoofers. Dolby bass management rolls off below 80Hz at 12dB/oct, so combined with the sealed box you have 4th order, which matches well to a 4th order low-passed subwoofer.
 
David Gatti said:
So far I'm not convinced of any real benefit of vented boxes, unless you have a very large and loud system.

Another thing is that a 2nd order roll-off is a better match for subwoofers. Dolby bass management rolls off below 80Hz at 12dB/oct, so combined with the sealed box you have 4th order, which matches well to a 4th order low-passed subwoofer.

There you are you see its all about the application.

Not once have I ever seen someone recommend a ported enclosure IF a sub is going to be used.

Ported box = a bit more bass from smaller drivers.
 

ShinOBIWAN

diyAudio Member
2004-02-25 9:13 pm
UK
RJ said:
quote:
The sealed box rolloff is always too fast versus room gain.

My T-Line sub-woofers graphed using the same size box Only the stuffing was changed. The red line sounded the best in room.

Fact is that ported boxes 'excite' room modes far more than a sealed design.

This means that in some rooms the response from a ported cabinet can be lumpy. Whereas sealed would be far less so. Dipole bass is best of all in this regards.

Personally I'm a huge fan of sealed and design around its lack of SPL and extension with regards to ported by using Linkwitz Transform and multiple, carefully selected, high quality drivers. That way you have the best of both worlds, low GD/Phase, high SPL, top notch transient response and very good extension.

Never heard a ported cabinet sound quite as realistic as a sealed design using this methodology.

Good transmission lines are very much superior to BR and in a completely different league.
 
It's actually an interesting question. I've been working on a straightforward 2 way for my bedroom. Initially, I was going to use a ported 7". As it turned out, an 8" would fit in the same cabinet if used sealed.

So the comparison becomes-

Sealed 8 vs ported 7 in a ~20l box. Well then it gets very interesting.

The 7 will reproduce bass around it's tuning frequency better. But this is a very narrow range, and, considering the frequency range from 20-100 hz as a whole, the 8" has better excursion and distortion capabilities.

The efficiency of the ported 7" isn't that much better because the 8" has an inherent efficiency advantage.

Midrange clarity of the 8" is better since you can stuff the enclosure heavily and damp the rear wave better.

Transient response under 100 hz will be better for the sealed 8", no matter how you try to tune the box since you cannot realisitically tune it flat to 20 hz or some such. Although, you can argue the main problem will be below tuning frequency, and this might be a wash.

The real question is probably, which gives the best in room response. This cannot really be modeled or expressed dogmatically. It must be measured. If the ported system is flat to ~35 hz and there is significant room gain above this, either from a small room or modes, the bass will be boomy and lack definition. On the other hand, in a large room, the dip below a sealed box's F3 may make the bass thin.