Help with port tuning

[aktivkampi]

Hello again.....

I need some help with the port tuning for my 2235's. I use them in 145 Liter cabs (each) with two ports of 32 cm. Is this correct ??? I have tools to calculate something, a friend told me, that would be the correct tuning for the 2235. they are used in an active system crossed at 80 Hz, 18dB/oct. What will be the correct tuning. Any help or advice I would thank for....

Greetings Aktivkampi

[aktivkampi]

Sorry... I've forgotten something

The diameter of the ports are 12,1 cm !!!! And I've no calculation tool !!!!

Aktivkampi

[Hoerninger]

And I've no calculation tool !!!!

Moin,
versuch's einmal mit WinISD (frei):
http://www.linearteam.dk/

Gruß Peter

[robertbartsch]

...most here in the U.S. probably do not use metric system measurements but that is a good guess on my part. If you could convert these measures you would probably get more responces.

[grumpy]

I can't imagine a lack of responses due to not being comfortable using the metric system...

That tuning looks "safe" and complementary to a "normal" living space
room gain, if a bit lower (~24Hz) than was used for JBL Studio Monitors
such as the 4430.. for sub use, I could see your chosen tuning making
reasonable sense. If a bit more "oomph" was wanted, a peaking 2nd order
high pass filter (3-6dB peak at the tuning freq) could be added electronically.

[duaneage]

It's practically impossible to calculate ports and volumes and expect to get it right without testing. Start with long ports and start cutting until Fb is met. If you don't know how to do this read up on the process in The Loudspeaker Design Cookbook by Vance Dickerson.

To spend all that effort and money building a sub without proper tuning and testing seems a waste. Even cloned systems need to be tested and retested from time to time since drivers vary and there is break-in with new surrounds.

In the end if what you come up with sounds great then I guess you're done with the project.

[cooky1257]

That gives a tuning of around 35hz with a fairly steep roll off below that.

[grumpy]

I need to learn how to read... "2" ports. ... Cooky is right.

plug one port and you have another option (estimated SPL at 100W,
18dB/oct, 80Hz LPF included):

[felixx]

Will be ok if you use a variable port?This way you could tune more "friendly" for you room and your taste.
The Tannoy go further with his "Dual variable distributed port" sistems.

Any of you guys have experimented round port versus rectangular or square ports?
Or no ports at all?Only rectangular hole tuned?
It seems the round ports have a noise behaviour comparing with rectangular or square tuned hole.

[Hoerninger]

Or no ports at all?Only ... (a) ... hole tuned?

It must be regarded as a (short) port as some distance in the air must be taken into acount too.
___________
Peter

[4313B]

I like round ports. They're neato.

[felixx]

It must be regarded as a (short) port as some distance in the air must be taken into acount too.

Ofcourse.Short port,mostly exactly like the thickness of the front baffle.

http://www.src-el-main.com/maxonicpage.html

[Hoerninger]

... mostly exactly like the thickness of the front baffle.

There is a theoretical approach that indicates for more. But in practice ist must be determind empirically.

http://www.src-el-main.com/maxonicpage.html

???
____________
Peter

[felixx]

Quote:
http://www.src-el-main.com/maxonicpage.html
???

The "port" length is only the thickness of the front baffle.This way the noise of the "vent" is insignificant,negligible.

There is a theoretical approach that indicates for more. But in practice ist must be determind empirically.

Mostly by year?
What do you think about Tannoy dual variable distributed port on both sides of the woofer?
I wonder how they can do this variable.....without causing noises.
Basicaly is only a few "holes" on both sides and those are closed or left open.
The mechanical sistem who work this way should be something very good build and to not introducing suplimentar noises,vibrations or other problems....
http://bv-bb.net/bonvivant/audio/refino/sys_096_02.html

[Hoerninger]

The "port" length is only the thickness of the front baffle.

... added with a correction 0,5*Pi*R, R is the diameter of the port. If L is the thickness of the baffle then the effective thickness is L' = L + 0,5*Pi*R.
(W.Reichardt / L.Beranek)
This would be my approach for a round port.

Mostly by year?

As last step by ear, first with gear in the lab. If you can't change the port it must be done with volume - or another speaker.

What do you think about Tannoy dual variable distributed port on both sides of the woofer?

This concept is not known to me, I go with old school.
____________
Peter