How large should be my port

Hi my friends! I am complete new into this hobby of building speaker boxes and after making a lot of research I still couldnt discover how to solve this question.


I have 2 speakers (125w RMS - Taramps 7driver HD 250S) which have a really really really nice sound (from low-high). I built a box with the following inner dimensions: 30 cm wide, 20 cm tall and 15 cm depth = 9 liters. The wood is 1cm thick however the front panel is not thick so I could easily cut the holes (it's 3mm and I will surely improve the thickness of the front wood in the coming days). Picture below:



I know I should use a much larger box with these speakers, however I dont have any space left for the place where this box will be placed in my house.


My question is this: I already made a hole in the box with a diameter or 6cm to put the port. My question is: how long must be the tube that I will insert into this box in order to get a good low bass (30 hz? maybe 40?). You can see in the picture below I 3D printed a tube with 6cm diameter and 10cm long, but I still dont like the bass (it does not improve much when compared to have the box sealed).




To quickly answer your question, you should find an online speaker box simulator. 

Otherwise, DIYaudio is a much better place for builders.

There are a handful of us that can help you here on agon. Unforturnately DIY won’t give you anymore help without some extra info from you. 1st you need TS Parameters on your drivers and the interior dimensions of your box. Get your driver spec’s and there are several free online calculators out there. For simple port frequency spec’s you can use this, but be aware, this won’t tell you how your drivers will perform without TS parameters.

Port Length Calculator (

Went to the website, looked up HD250s, they do not show TS parameters.  However, they do show FS on this speaker, which is 77hz.  I'm sorry my friend,  you will never get any deep bass from these drivers.  


yes the fs is too high get yourself better drivers these are car woofers

     Timlub’s comments regarding drivers, TS parameters, box dimensions and port size:


Oh the horror!!  Why do this…so many well designed inexpensive speakers you can purchase.  I have a JBL Charge 5 that sounds incredible and is Bluetooth ready.