[Mike P.]

What is the net volume of the box?

 

[Mike P.]

The RL-i 8 would definitely be a better option if price wasn't an issue, but it has been out of stock for a long time, second hand is the only option to obtain them.

 

[Mike P.]

The TB's will output 105 db at 30 hz and drop off below that, not bad a a pair of 8's in 1 cu.ft.

 

[Mike P.]

I did some modeling of the TB 8, you can get an extra 7 db at 20 hz if you lower the tuning to 27 hz and modify the HPF to 24.3 hz with 2 db of boost from 31 - 35 hz. Pink is with the default HPF and boost the amp comes with.

 

[Mike P.]

The TB's will output 105 db at 30 hz and drop off below that, not bad a a pair of 8's in 1 cu.ft.

That should be 108 db at 30 hz, I forgot to model in the default boost the amp comes with. The above graph shows the default HPF and boost.

 

[Mike P.]

Just curious, how big is the room this sub is going in?

 

[Mike P.]

Room gain will boost the low end so the end result will be better yet.

 

[Mike P.]

The default values for the amp are R17=10K and R18=60K. The closest to that from the boost tables is the bottom line of the "2db of Bass Boost" table. The HPF would be about 30 hz and add the boost. The table states the boost is 2 db from 36 - 40 hz. To add that to the modeling, add a Parametric EQ filter, input the "Center Freq" as 38 hz, the gain as 2 db and the "Q' as 1.2, as stated in the boost table. Do the same for a 24.3 hz with 2 db of boost from 31 - 35 hz. Check cone excursion with input power applied to verify the sub is within Xmax. You can try other combinations of HPF and boost to see the effect it has on the output of the sub.

 

[Mike P.]

The cone excursion of the default values dictated that a lower HPF could be used. The next lower HPF was 24.3 hz.

 

[Mike P.]

WinISD Pro (version 0.50a7)

 

[Mike P.]

With a 29 hz tuning a 8.5 x 1.5 slot port is 32.5 inches long. With a HPF at 24.3 hz and the boost that goes with it and 500 watts input power the port air speed is 32 m/s at 29 hz, definitely at the limits. I'm not sure how you're coming up with 13m/s.

 

[Mike P.]

I modeled peak air speed with 500 watts input power.

 

[Mike P.]

Forgot about that ohm thing. :whistling:

 

[Mike P.]

Green is with 250 watts input, HPF at 21.6 hz and 2 db of boost from 25 - 30 hz. Maximum air speed is 25 m/s at 28 hz. Pink is the wrong modeling of 500 watts.

 

[Mike P.]

Sounds good. Don't forget your camera when you start building. :yes: