Which power value of the actual speaker is the best for the simulation and design ported boxes?

I have simulated 4 ported boxes using different power values (Pe) for a DD 506 D2 redline woofer. My rule for the boxes is to not overpass Xmax at 30 Hz and higher frequencies. On DD's website there are 3 power values for the 500 series woofers, for RMS power 150 (minimum recomended) and 400 Watts (actual), and for peak power 1200 Watts, so I simulated boxes using 150, 400, 1200, and finally 450 Watts (if for 400 Watts RMS the peak power is 3x400 = 1200 Watts, then in my opinion for 150 Watts RMS 3x150 = 450 Watts is the correct peak power for this speaker). Here is the project:

In stock here on SBL for this speaker the Pe = 1200 Watts in the calculator. If I tried to design a box using my rule, the Vb is small, and the port length is huge, so the box is abnormally big for this woofer, and the woofer's basket not fits in the box + the woofer overpassing the Xmech at lower frequencies than 30 Hz. So this box is not good for this woofer.

I changed the Pe to 150 Watts: Vb is huge, Fb is too high, box is big too, group delay is huge around the Fb - wrong box too for this woofer.

I changed the Pe to 400 Watts, then for 450. Both boxes are buildable with normal outer dimensions, the sounding will be probably acceptable on both, and the Xmech is not overpassed at lower frequencies than 30 Hz. On 3D designer is the box what is designed with Pe = 450 Watts.

For example for Monacor Raptor 6 woofer there are displayed 2 power levels on every website: 100 Watts RMS, and 300 Watts max. If in calculator I use Pe = 100 Watts, the box is wrong like for the DD when I used 150 Watts in simulation. In stock here on SBL for this speaker Pe = 300 Watts, and as you can see on 3D it is no problem to design a good sounding buildable box for this woofer using my 30 Hz rule. Here is the project:

So these are the reasons why am I asking this: which power is correct for simulation: RMS, max, peak, or even the amp's power if the amp is weaker than that power what woofer can handle?

I did not use the attachements because you cannot see the comparison between the boxes at Graphs if you click on the box...

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+51 LayinLo

21 Nov 2019, 02:32

I would recommend that you stick to using the RMS (root means square) wattage. This will be your continuous thermal power handling limit of the woofer you are modeling. Max and Peak are almost always interchangeable and generally mean the same thing when commonly used. Digital Designs probably lists 150-400 watts RMS as the recommended power handling


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+51 LayinLo

21 Nov 2019, 03:05


If you'd like, I'll take a look at your project when I get home and see if any improvements can be made with your design. From what I recall, DD makes box recommendations on their site. They have a different approach and philosophy in regards to the way they design the subs and the end user builds a box but It's been a while since I read any of their literature. Just going out on a limb here, but that should be one of their 6" subs so it probably needs 0.25-0.5 cu ft and a port even as small as 0.5" x 8" is probably gonna be 30" long or so before it tunes it to around 35 Hz. Anyhow, let me know and I'll give it a look when I can if you want.



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+156 P-Bass

22 Nov 2019, 22:48

Thanks for your answer. I decided to design a box for the DD 506 with my 30 Hz rule using the parameters from DD's site and Pe = 400 Watts. The box what I simulated completely in SBL's simulator and designer is on 3D-box too and on Graphs: red line.

I find out that the parameters are not identical on different sites, and I know that a different simulator makes different results, so for comparison the green line on Graphs is a box what I simulated in WinISD using parameters from, and the blue line is a box simulated in WinISD using the parameters from DD's site. So now, I dont know that the comparison-simulations are OK, but the differences are really big compared to SBL's results (maybe really my simulations in WinISD are wrong...)

+156 P-Bass

24 Nov 2019, 20:41

Hi, LL

As an another example for this "problem", I tried to design 4 ported boxes for this dual voicecoil woofer:

Monacor SPH-200CTC

Monacor SPH-200CTC

Fs: 22 Hz, Vas: 75l, Qts: 0.22

with a little bigger port areas than minimum recomended for the actual box's Fb (in Graphs at all designs the red line is the line for the actual Pe, the other 3 lines are for the other 3 Pes). Here in SBL's database the RMS power is 60 Watts, and Max power is 100 Watts. In designer (Calculator) the stock value for Pe is 100 Watts. First I designed a box for Pe = 100 Watts (Xmax is not overpassed at 30 and higher frequencies), then I find out that for 60 Watts it is plausible to design a buildable box to not overpass the Xmax at 20 and higher frequencies, so I designed that. Then I chcecked Monacor's website to download the original datasheet for this woofer, and in that datasheet the RMS power is 2x60 Watts, and Max power is 2x100 Watts. So now, first I designed a box for Pe = 120 Watts (Xmax is not overpassed at 30 and higher frequencies), then for Pe = 200 Watts - to not overpass Xmax at 30 and higher, the box is not buildable with speaker's basket inside, and with acceptable port area + it is too large, but for 35 and higher it is buildable.

Here are the designs:

You recomended me to use the RMS powers, so in this case the Pe = 100 and 200 Watts boxes are not OK, and the best box for this woofer to not overpass the Xmax at 30 and higher frequencies is the box designed using Pe = 120 Watts.

To not overpass the Xmax at 20 and higher frequencies + to sound clear and as loud as it is possible using this woofer, I must reduce the power down to 60 Watts on the amp, and use the box which is designed using Pe = 60 Watts. Am I right?