Front Port vs. rear port

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Karnaaj

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Front Port vs. rear port
« on: 19 Sep 2004, 07:34 pm »
I have a pair of Soliloquy 5.0 monitors.  They sound good and look beautiful but I'm wondering if I can do better with front ported speakers.  The maximum I can get my speakers from the rear wall is 30" which, from everything I've been reading, is not ideal.  Would I see a big enough improvement switching to front ports to warrant the change or should I keep the Soliloquys?  Thanks.

p.s. the room dimensions are 15ft by 12 ft.

mcgsxr

Front Port vs. rear port
« Reply #1 on: 19 Sep 2004, 07:41 pm »
Well, can you express a little more about what you find wanting with your speakers, in your room?  You do mention that you have read that 30 off the wall might not be ideal, but are you experiencing bad things with your current placement?

I have my Totems (rear ported) about 26 off the wall - WAF prevents "optimal" placement, but I think they do fine there.  I do augment with subs, but the Totems on their own sound balanced well enough top to bottom.

There are speakers (often British, or Euro) designed to be near walls, that might offer better sound, but it really depends on what you are after.

Mark in Canada

Val

Front Port vs. rear port
« Reply #2 on: 20 Sep 2004, 01:10 pm »
Although port location could be a factor in your particular situation, it has more to do with how the speaker was designed regarding bass output. A speaker that is relatively flat in the bass when away from boundaries shouldn't be placed near boundaries because room gain will augment its bass and make it sound boomy. A back port will probably make it worse, as would the bigger the speaker (supposedly more and flatter bass) and the smaller the room.

For example, take a look at Audio Ideas Guide's rave Amphion Athene review. AIG's measurements show that the frequency response of the (back ported!) Athene drops below 200Hz when measured well away from boundaries, but room gain will fill its low end very well when placed close to walls, as Andrew Marshall says. Amphion is a good and relatively inexpensive speaker brand, by the way.

You could experiment with blocking the Soliloquy's port.

Val

Morty

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Front port vs. rear port.
« Reply #3 on: 23 Sep 2004, 07:54 am »
I have had many speakers in my home.
All rear ports became wooly if located too close to wall.
I had a set of Amphion Xenon with side firing woofer and rear port.
Same story, but in addition, the side firing seemed to worsen the speakers ability to "connect to the room". - There seems to be plenty of bass, but after a while, one realize that bass is very uneaven and not physical "down there".
Typically for all Reflex systems, the bass is uneaven; Some places in the room, there will be an overload of bass, some areas will lack bass and, hopefully, some areas will be about correct. If you are really lucky, or in the position to arrange your HiFi system without regard to wife and estethics, you may even be able to use this area as your listening sweet spot.
So, what I am saying is that among reflex systems, a front port with all speakers firing straight forward will give you less problems with the bassoutput and - as a general rule - will allow for positioning closer to the back wall than the other designs. I guess the front port will have somewhat less "help" from the room and also somewhat less measurable effect on the bass performance.  But your ears will tell you different. A front port will (if engineered correct) sound more even and better.

Today I use dipole. All units; bass and tweater is firing both ways.
One should think that the law of nature would eliminate the very lowest frequencies but if engineered well, this restriction can be minimized a lot, if not totally eliminated.
The funny thing, - and pleasant,  with such dipole systems is the way it connects to the room.
- Move around in the room - the bass is equal and even - all over!
- Move the speakers closer or farther from the back wall; Not much difference in bass performance, only a bit LESS bass if too close to the wall. And of course, the perspective and ROOM definition becomes less defined.
I guess owners of Quads, Magnepan etc. have experienced some of the above.
Here's a link to my dipoles: Forsman VSS III:

http://www.forsman.no/English/Products/Products.htm
Regards
Morty

BobM

Front Port vs. rear port
« Reply #4 on: 23 Sep 2004, 12:41 pm »
If you need to stay close to wall boundaries then either a front firing port or a sealed speaker or perhaps use of a passive radiator (like the Thiel's) would probably have less room interactions than other alternatives. If you're going for a front port though make sure that it isn't too small. Small front ports tend to chuff audibly. Then again, overly large ports tend to let high frequencies through their opening, unless something is done internally to keep them out (like separate internal chambers or low pass filtering materials).

There are lots of theories on port size and location. You may want to ask your question of the experts at www.madisound.com

Enjoy,
Bob

Morty

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Front port vrs. rear port and so on..
« Reply #5 on: 23 Sep 2004, 10:51 pm »
Quote from: BobM

QUOTE:
If you need to stay close to wall boundaries then either a front firing port or a sealed speaker or perhaps use of a passive radiator (like the Thiel's) would probably have less room interactions than other alternatives.
UNQUOTE.
Agree! But the order should be, reflex, radiator, and then, ("best") sealed.  Open baffle, of course being the refernece...

Quote:
If you're going for a front port though make sure that it isn't too small. Small front ports tend to chuff audibly. Then again, overly large ports tend to let high frequencies through their opening, unless something is done internally to keep them out (like separate internal chambers or low ...

UNQUOTE.
Well, agree  too, but really, a speaker with a small reflex port, either front/ rear orientated, are ALLL low qality speakers.
Distortion from "breathing"  is only one of several typical design faults.

JLM

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  • The elephant normally IS the room
Front Port vs. rear port
« Reply #6 on: 25 Sep 2004, 12:19 pm »
Realize that bass notes are omnidirectional, so except for chuffing, the output from the port (if properly designed is bass only) doesn't much matter what side of the cabinet it's coming from.  The force of air coming from your port is minimal and so the air pressure from the port probably couldn't be measured 4 inches away, so how could the wall 30 inches away make any difference?  (Compared to the port, the open space around the speaker is huge, so the pressure of this highly compressible fluid, air, will drop extremely quickly which eliminates it's affect on the port output.)

Most designers argue against front ports as it's output would be out of phase with the woofer (best then to put it in the back so it's heard less).  But that paramount to admitting that you have less than an ideal design to start with (as mentioned by others above).

Yes, as you move toward a wall/floor/ceiling/corner the large omnidirectional bass sound waves "see" the amount of free space they're radiating into reduced and thereby reinforcing the bass output, but that relates to the overall output from the speaker, and for the most part is independent of the port (or no port) design used.  The Cardias sort of speaker positioning guidelines relate more to keeping the side/back wall distances from becoming multiples of each other (and so reinforcing the overall output) at given frequencies.

The dipole/bipole/open baffle/infinite baffle concepts are completely different animals and in many ways provide a more natural soundscape/bass reproduction versus the pin-point imaging and artificial bass that many audiophiles are accustomed to and strive for.  They're not without their own set of challenges, including limited driver selection, possible need for equalization, and more space/permanent installations involvement.