Thiele Small and Cab Volume

[cobaltsixty]

I have searched the forums but forgive me I cannot find a treatise on this.

How can I best determine the suitability of a speaker for an old TNT150 Bass Cab by using the Thiele Small Parameters ?

Here's the setup:

1. SWR Bass 350 AMP / 350W into 4 ohms.

I need a 15" Speaker to go into the cab I mentioned.
It is not necesssary to achive max wattage from the amp, just optimal.
I don't need to stay with any set Ohms.

My ignorance lies here:

Is it possible to match a speaker to this cab volume and CLOSE to the power of the amp AND get a useful sound ?

It seems to me a 2 to 8Ohm Spkr is applicable but will the cab volume limit the mechanical performance of the speaker assuming some software program states that the volume is within limits for the speaker. How critical is thaat volume number ?

Obviously I would need to determine at what point to stop increasing volume from the amp to avoid damage no ?

[Dookie]

First you need to measure the "inside" of the box. How High,Wide and deep.

No idea how big your box is but as an example.
30 X 22 X 16 inches deep inside.
This equals 10560 square inches.
Divide this by 1728. 12 X 12 X 12 = 1728 or the amount of square inches in a square foot.

10560 divided by 1728 = 6.111 cubic feet
Subtact the volume of the speaker and braces or ports to get your total box volume.
Some just subtract 10% of the box volume for the above.
So roughly you could say the above box is 5.5 cubic feet. Next you measure your port on the inside and see the area it has. Round or square or slot etc. Use a speaker program to determine the boxes tuning freq. and last find a speaker that will work well with the speakers volume and tuning.

Run your measurements here. Someone here or myself may have time to give you the numbers you need.

Doug

[cobaltsixty]

Groovy,

Thanks Dookie !

I will post the math up here.

[IAmPhil]

I have a 1983 TNT 130 and it is 2.05 cubic feet (with a Black Widow mounted in it) and it is tuned to 58 htz with the funny little 4" x 4" triangle port that's only .75" deep.

If you change the port to 4" round x 6.9" long you will change the tuning down to 41 htz (the resonate frequency of the low E string). This makes a noticeable difference.

Then find a 15" speaker with a resonate frequency around 41 htz and you're in business. I'd get one with a neo magnet so you don't break your back. My Black Widow is 17 lbs and a neo Celestian is 5 lbs.

I know this post is 8 years old but I looked for this info when I got on here and couldn't find it so I measured and learned so hopefully I'll make someone's life easier.