A7 PORT SIZE MODIFICATION

[ngccglp]

Hi,

As suggested by another thread, I reduced the port size to about 90 sq inches. What I did was to use a piece of MDF to cover over the port. I made use of the existing screws so that I do not need to remove the original panel.

Is this method acceptable or do I really need to cut a new piece of wood to replace the orginal panel?

BTW, the bass boom already reduced significantly. I know this for sure because I need to lower the high freq to balance the sound again.

Thanks
David

[Fitts]

I've done something like what you did and then went to the trouble of "doing it right" and found no audible difference. I would leave it as you have it and just enjoy it.

Regards

[ngccglp]

Hi David,

I played around with various sizing and listened extensively to the same few songs I used as reference.

Surprisingly, when I went back to the original port, it sounded the best. When I'm using smaller port, altough the bass seemed cut somewhat, the 'impact' or 'whack' of the drums seemed muffled.

Also, as I successively reduce the port area, the bass first decrease, then increase again. Do you have the same experience?

Thanks
David

[RacerXtreme]

I changed the port volume on a set of A7's but sold them years ago. Built them from scratch from Altec blueprints and did the horn in a woodgrain veneer. The horns and the entire cabinet came out pretty nice. I took my time....

Don't remember what size ports I ended up with. Think I had JBL E-140's in them at the time.

I tried different porting on Altec 210 cabinets too. Did the math, and tried different things, but ended up with this.



For some reason, (and maybe it's just me....) I always though they were over-ported. As I get my stuff back up and running, I will definitely experiment some more. Picked up six 515's so I'm gonna stuff four JBL 2225's in two of the 210's, and four Altec 515's in the other two cabinets. All I need is one more 400 watt 2225
and I'll have eight 15" woofers in the big Altec cabinets. I think it's going to be a challenge to "blend" them in together, but I'd like to try. The JBL's will give me a bit of that "thump" that the Altec's don't have, and the 515's will give me the tremendous mid-bass that they're famous for. Yeah, I know.....I know....... I probably need some 18's for the low stuff, but eight 15" woofers should move a lot of air.

Check out the ports on the mini A2 cabinet. They're pretty darn close to being sized just right.

[Fitts]

I tried the full port as recommended in the original Altec plans and found it to be too large for my 16 by 12 listening room. I decided to use a 75 square inch port based on factors that included the throat opening of the cabinet. I did try a 100 square inch opening and went back to 75.

Try it, I think you will find 75 offers good control and solid bass.

Regards,