[starlet]

Since it is not advisable to place speaker too near the rear wall, why is that not all speakers are make to have forward facing port? Will this not help solving some placement problem?

What about bottom facing port?

What are the advantages and disadvantages between these design?

[JohnR]

The problem with a forward facing port, as I understand it, is that you do get a certain amount of midrange energy coming out of the port. If the port is on the rear this is less likely to be audible.

Or you could do what I do, and "just say no to ports"  

(Actually, that's not quite true... I do like ports for teeny drivers...)

[starlet]

Does an enclose design need a bigger cabinet volume to produce the same bass as an ported one?

Is there any site where I can read about all this basis?

[JohnR]

Not quite that simple... generally a ported box is larger than a sealed box for the same driver, and it has a more extended bass response. However, it really is dependent on a lot of things... here is a graph I have posted on a different site that shows a bunch of response curves. These are all the *same* woofer! The pink line is sealed, the rest are bass reflex. One could reasonably argue that the pink (sealed) response has more bass than the red (ported) response.



http://www.diysubwoofers.org might be a useful resource. Other than that I honestly think that downloading version 3.x of Unibox and playing with it is a great way to learn about what's going on. Tim Verry told me this ages ago and I've been repeating it ever since

Otherwise, perhaps more information on what you are trying to find out might help get other answers.

HTH

[JohnR]

Hm. Perhaps it would help if I answered the question in a different way. You can't just increase the size of a sealed box to get the same amount of bass as a ported box. The reason why is because the shape of the curves is different

[starlet]

Thanks for the input John.

I am trying to find out more about speakers design as my next upgrade, if I ever have any extra cash, would be to replace the 6.9s.

In my set up, due to room constrain, the speakers can only be place about 1.5 feet away from the rear wall. The 6.9s is doing fine with this placement but they are two way bookshelf.  The side walls are far away so I am not too concern about it.

Any recommendation about good 3 way speakers which are not that sensitive to rear wall effect (at an affordable price) or any particular design type that I should look at?

[JohnR]

I don't have any specific recommendations, perhaps others might?

This article (graph) explains why ported boxes have a habit of sounding boomy especially if placed close to walls:

http://www.adireaudio.com/tech_papers/enclosure.htm

Some manufacturers seem to tune speakers to purposely have a peak before rolling off. Bleah.

[BikeWNC]

John,

What are the pros and cons of filling the port with something like open cell foam to reduce a boomy bass?

Andy

[MaxCast]

John,

What are the pros and cons of filling the port with something like open cell foam to reduce a boomy bass?

Andy

Stuffing the port tends to tighten up the bass at the expense of decreased extension.

You may want to try lining the inside with black hole, stuffing or some other type of resonance damping material.

[ABEX]

Do not know why ,but rear ports have always been better for for me.Atleast for my room and taste.

I do have a sub that has a port to the front now.If I could do it over I'd rather not have a sub that is ported.

[JohnR]

Adding to what MaxCast said, if the port is really stuffed (making a sealed box), then looking at the graphs above, the response will change from something like say the black line to something like the purple line. However, there will be a lot of variation depending on the woofer and the tuning of the box.

[JohnR]

Starlet, you might want to look into something like the GR Criterion and a separate sub (or two). You could talk to Danny about retuning or moving the port if necessary.

[MediaSeth]

My speakers are a 2 1/2 way design with a midbass port in the rear and a bass port on the front.  I either have the best or worst of both worlds, port-wise  I put large foam squares across the corners in my room behind both speakers, and the speakers themselves are good distance from the walls.
The last sealed-box I had were 1973 Advents that had the foam surrounds redone and a weird custom dustcap on the bass drivers. (looked like handmade paper you see at craft fairs, only grey). I can't use those as a reference for how a sealed enclosure sounds...except that I did notice a gentler roll off and less-punchiness.

[ABEX]

It is best to have a Rear Ported ,close as you can get Full-Range and an enclosed Sub to handle down to 16-20Hz. if it were me.It can be the difference in people that like Horns to people that like Planer SPeaker's also.Hard to find that equalibrium because there are always tradeoffs and room acoustic problems.

Ports tend to Cuff so there is distortion to think about.Closed speaker's try to recreate whatever was produced so in a way they create a distortion from  recorded music.Punch might be the advantages in front ports.

Everytime you add a sub there is something lost.It is better to have a fullrange speaker instead.

In the final outcome I think now it comes down to getting speaker's that fit your rooms dimensions and sonic taste instead of getting wall to wall monitors that you can't possibly fit or are overkill.

Hell, I am thinking of getting Micro Components now or taking the size of units to be more practical. Things that are the size of an ART DAC would really help with the performance of Mark Levs for amps.

Small footprint full range speaker's are what I want for a regular sized room.

JMO