Proac 2.5 Down firign port question?

Hello
this is my first post and my first attempt on building a speakr
i chose proac 2.5 clone as my first (last?) project because i really fell in love at studio 140 (poracs) that ive heard in an audio shop.

my only problem is a really bad acoustics that i have at home, the speakers are standing against a huge glass window in my living room
so i thought of changing the port location of the procas to ta "down firing port" as i heard that it makes the speakers placement less critical.

i waned to ask how much replacing the port from back firing to down firing will effect the proac's sound? for the better and worse?

thanx for any help!!
-Rostislav.
 
Hi Roman asn Rostislov,

It is a really good idea. Actually so good, that is exactly what ProAc is now doing in at least the new D28. Maybe the D25 and D38 too but I am only sure they are doing it in the D28.

However, the D28 uses different drivers and crossover and design so I don't know if converting the Response 2.5 or making a hybrid will be so easy!

Research and good luck!

Regards//Keith
 
Thanx for your help

i presume placing the port forwared will deviate even more from the original sound (wich i would like to preserve)

experementing is not really an option and i have to decide what im going to do (because i wouldnt be able to change it later)

thats why i wanted to ask you guys how much the sound will change if i replace the back-firing port with a "down firing port"

would it change the bass response? should i make the port thicker and longer to compensate for the sound?

any info would contribute as i am not very experienced in audio.
really thanx -Rostislav.
 
I am not a speaker builder like Roman is. He is very capable, so you are in good hands.

Here is the hyperlink to the D28s. The D38 also uses a downward bass port that is ported sideways at the plinth.

Next thing you know Audio Physic and ProAc will merge!

I wonder what would happen if you put those guys in the same room!

Anyway, look at these and hopefully you will get some ideas: http://www.proac-loudspeakers.com/d28.php

Good luck!

Regards//Keith
 
Thank you Keith. Are you ever going to make it to Brooklyn to listen to my clones?
I am building another 2-way bookshelves, so don’t be shy and bring your ProAc for a shootout.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=119209

I’ve read somewhere that people have placed ports on the front panel instead of the back with good outcome.
Placing the port forward or down firing will change group delay at the bottom end. It will slightly change the character of the speaker but I don’t think it will be major.
Changing the size of the port, on the other hand is a big no-no if you want to stay as close as you can to the original. It will change bass response significantly (well, relative to the modification).
In all fairness, 2.5 clone may not have exact sound as the original but it’s just as good or better. Changing the position of the port aren’t very likely cause a catastrophe.