Ported vs. sealed

 

Bronze Member
Username: Flame_rose

Post Number: 17
Registered: Sep-07
Hi guys;

Anybody can give a brief and simple outlay of the pros and cons of sealed vs. ported speaker cabinet designs?

ThanX
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 11872
Registered: May-04
.

You can find the information by placing either phrase in a search engine. The most basic difference is in the efficiency of the system with ported being 3dB higher than sealed. Sealed enclosures have a more gradual bass frequency roll off below system resonance with the vented enclosure rolling of at twice the rate of a sealed enclosure's -12dB per octave.


What other type of information are you asking for?


.
 

Bronze Member
Username: Flame_rose

Post Number: 18
Registered: Sep-07
Thanks Jan;

I'm also interested in frequency responce, timbre variation, placement within rooms. This has become of interest to me as I've completely "sealed" the rear port of my Jamo D590 speakers (by plugging the ports with a large sponge) to address bass boom (having optimized the placement to the Nth degree). It has paid off well in terms of boom but I've lost some air around instruments and the width of the soundstage is noticeably less. Both are not problematic to me, but what occasionally irritates me is the increase in midband coloration/cabinet resonance that I'm hearing. This is noted with both male and female vocals. Vocalists enjoy more presence and feel larger like this but the tonality of their voices is unnatural and "woody". I am wondering if this is an inherent weak point of all sealed cabinets or is this a specific occurance with my improvised sealing method.

Regards...
 

Gold Member
Username: Nuck

Post Number: 9441
Registered: Dec-04
MA, all the componants of a speaker are designed around the end product. Plugging the ports has lots of effects, and manufacturers regularly provide plugs for the effect that you have now.
Very few speakers will act properly, or at their best with the ports restricted.
Sealed units are designed around just that. Always sealed, and can perform quite well.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 11873
Registered: May-04
.

I have to say I'm not a big fan of foam plugs in ports.


The enclosure volume and type (sealed, infinite baffle, bass reflex, transmission line, etc.) work as a system with the woofer. A particular driver will be chosen for a specific cabinet type. The "Qts" of the driver is not that similar between a vented and a sealed enclosure. There is some degree of overlap between which driver can be used in a sealed cabinet and which can be used in a vented cabinet but typically a driver does best when it is chosen for a specific cabinet and going above or below the preferred "Qts" of the driver creates a system misalignment. This will result in a different system "Q" which will affect the response primarily in the midbass to lower midrange and upward depending on the system. I suspect you've simply created this misalignment of the system. You can try different materials if you really think closing the port is the best solution - which it usually is not. A tiny air leak in a sealed enclosure results in poor response throughout the operating range of the driver so if the foam plug allows air to leak out, you will have uneven response. Of course, room issues also cause irregular response. Room treatments would be the correct solution if that's the case.


As far as placement goes, the room determines the best placement in almost all cases. Put "loudspeaker placement/set up" in a search engine and read a few selections. Find the "WASP" method of placement and try it before anything else. The only significant difference between a sealed and vented enclosure as far as placement goes would be if the speaker has a rear facing port which will require a bit more distance from the surafce behind the speaker. This typically isn't problem since most speakers require a few feet between the cabinet and the wall anyway.


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Gold Member
Username: Nuck

Post Number: 9444
Registered: Dec-04
MA, you have place them to death, including the WASP, I presume. Maybe this room is not going to produce as is.
What kind of treatments have you tried/researched?
 

Silver Member
Username: Rysa3

Houston, Texas

Post Number: 267
Registered: Nov-06
One comment here, with a sealed speaker, you can place it much closer to a wall behind the speaker and still get optimal performance.

In my HT room, my mains, which are ported, really need some breathing room ( like 2.5 feet minimum from rear port, to be at their best. My surrounds, which are sealed, can go right up against the rear walls/corners without a problem.
 

Bronze Member
Username: Flame_rose

Post Number: 19
Registered: Sep-07
Jan> Thank u for your detailed reply. It is clear now what is happening to my sound.

Nuck> You are absolutely correct. I've had my speakers for over a year now and I've tried - methodically - just about every possible position and this is the best compromise I was able to get. What makes it more difficult is not just the HUGE rear port but also the 10' down-firing woofers. I even tried two different rooms with more or less similar results.

As for room treatments, I live in saudi arabia, therefore I'm screwed. Room treatment market is very very very small and limited to auditorium construction. The same applies to the speaker market (will change my speakers once funds allow). We've got the very exotic (Sonus Faber/JM Lab Be series / McIntosh) and the mainstream (sony/aiwa/samsung). The middle segment which i'm looking for doesn't exist and you're all aware of the risk of buying without a home demo. I'm currently using all Naim CD5i/Nac122x/nap150x/Naca5 and a speaker change to match is badly needed. Until then I have to get the most out of the Jamos.

Regards
 

Gold Member
Username: My_rantz

Australia

Post Number: 1788
Registered: Nov-05
Well Maher, there sure is nothing wrong with your source and amplification. What type of floor do you have - hard or soft? I don't know the speakers, but if they are down-firing perhaps carpet peices (if hard) underneath may help instead of plugging the ports.
 

Gold Member
Username: Nuck

Post Number: 9450
Registered: Dec-04
MA, have you looked at Naim's own speaker line?
 

Bronze Member
Username: Flame_rose

Post Number: 20
Registered: Sep-07
M.R.>
The floors are ceramic tiles. 20% of the surface is covered with furniture, while another 15% is covered with carpets. I will consider experimenting with carpet pieces underneath the speakers.

Nuck>
Well, Naim speakers are a bit out of my reach and for some reason I am not willing to go for bookshelves. I want a large presentation which I don't think bookshelves can provide regardless of the presence of a sub within the system. I also hear that naim speakers are a bit dry sounding and this is the exact opposite for what I am looking for in a speaker.

BWT, Bose is available here and although I hate their acoustimas sereis I wonder how their floorstanders would sound. Any experience?
 

Silver Member
Username: Rysa3

Houston, Texas

Post Number: 268
Registered: Nov-06
I demoed that Naim HT set up at CEs last year and didnt find them dry at all. Quite impressive actually. Might wanna listen to em.
 

Silver Member
Username: Nmytree

Post Number: 152
Registered: Aug-04
Decorative rugs on the walls can make for good divusion and some light absorbtion.

Bookshelves filled with books on the end wall your speakers face; can make for acceptable bass traps.

Decorative screens/dividers such as this one in the link (http://www.orientalfurniture.com/oriental-furniture/SSAMAKE.html ), in the corner, with several large pillows at the foot of the screen and a few decorative blankets draped over them; can become fairly good bass traps and aide in diffusion and absorbtion

There's a lot of things you can do with decorating that will aide in the sound of the room.
 

Silver Member
Username: Nmytree

Post Number: 153
Registered: Aug-04
I meant .....

Decorative rugs on the walls can make for good diffusion and some light absorbtion. Not "divusion".

Apparently DiVusion is a machine used for Diffusion Tensor Imaging in Neuropsychiatry.
 

Gold Member
Username: Nuck

Post Number: 9455
Registered: Dec-04
Well of course it is, silly.
 

Silver Member
Username: Nmytree

Post Number: 154
Registered: Aug-04
, Nuck.


I also forgot to mention placing several large potted fake plants (made out of fabric or silk) in the listening room can also help out.
 

Gold Member
Username: Frank_abela

Berkshire UK

Post Number: 2593
Registered: Sep-04
NMyTree

That kind of thing is very good for flutter echoes caused by mid and treble reflections but they don't help a huge amount on bass frequencies which is where Maher appears to have a problem.

Maher - naim speakers are not so much dry as lean in the bass. I fear you may be right that they may be a step too far away from the big presentation of the D590s, especially if you went with the N-Sat bookshelves, although the N-Sub integrates beautifully with them and allows you the opportunity to tailor the bass response of the system in your room.

That said, if your dealer has a pair of Arivas or Allaes these are the least dry sounding speakers Naim have ever made. The Ariva is a 2.5-way sealed floorstander which has a big powerful fast presentation. It has recently been discontinued so you may be able to pick it up for a nice price. The Allae (pronounced 'Ally') is a more expensive ported solution designed to go against the wall. It is in another league to the Ariva of course. And here's the nub of the matter - if you like the naim speakers, the chances are that you will love them, and find faults in most others. they are a fairly unique sounding speaker, which is why they are seen as much more niche market than the electronics. one last thing - the Allaes retail for similar money to the N-Sats and N-Sub combined. People have compared the two and some prefer the Allaes, some prefer the N-Sat/N-Sub combination.

Regards,
Frank.
 

Silver Member
Username: Nmytree

Post Number: 155
Registered: Aug-04
Hi Frank.

Yeah, I was just giving suggestions for all frequency needs, not just bass frequencies. But I did give two suggestions for bass.

I think many would be surprised at how effective two bookshelves are( more rectangular shaped, rather than tall and slim, stacked with books, placed on the end wall (facing the speakers' front baffle), in the corners.

Is it ideal? No. But if you're someone who can't afford professional bass traps or have little to no access to bass traps; those techniques really make a difference. Especially if you use large pillows made of wool or wool rugs in conjunction with the bookshelves or decorative screens.

And if you are someone who already has a large collection of books, you're already ahead of the game. Otherwise one can pick-up/buy a lot of books at yard sales, used book stores, Salvation Army...etc; for extremely cheap.
 

Silver Member
Username: Gamerdude

Ontario Canada

Post Number: 542
Registered: Apr-06
I'm a sealed fan, lets the woofer take more power before bottoming out. Also the bass is not sloppy and more controlled.

Just what I think..
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