Blog Forums DIY Speakers and Subwoofers I need an order of operations. Reply To: RE: I need an order of operations.


@opulentone – watching now. And yes, a driver is a driver. It is all about learning to create the driver’s best enclosure. The skills always translate.

Piston diameter was entered wrong. You need to measure the peak to peak of the surround (unless that is what you measured). Most times, a speaker’s “size” is the size of the speaker plus the basket. You want only the piston diameter. For example, my 30W/4558T00 subs are 12″ subs. BUT, for piston diameter, it is only 244mm (that is what the spec sheet said, I measured 243, but I was doing it with a straight edge from my compound square set on top, so within 1mm, why not just add it from what the spec sheet said).

If you get the diameter wrong, all other calculations on which it uses that number will also be wrong. So that is a potential issue.

Now, notice that the diameter you entered as 6.5″ (Piston Diameter, D) in DATS is the value you should enter as Dd in WinISD. From Dd, WinISD can calculate the Sd value, and from that with I forgot what other value, it calculates Vd which is Volume displacement (IIRC).

Now, if you also notice, I entered Qes from DATS. So if you enter the values I show in the sheet there, it should pass the driver check integrity.

 Now, I have not learned a good way to measure XMAX yet, and I took XMAX off of the product spec sheet, same with Power (for Pe, enter the continuous or RMS value of the driver, preferring that followed by Long Term Continuous 100 hr if the RMS value is not present.

Now, Scanspeak, in their infinite wisdom, listed two values for peak and linear excursion. The highlighted ones are correct whereas the ones to the left under “Key Features” is wrong. The Key Features one is the peak to peak excursion. You need to divide that in half, which when you do, you get the values I highlighted in Yellow.

For power, they listed it as IEC18.4 for the 100hr RMS. THAT is the one you want. The 18.2 long-term max power is a different measurement, and you will be riding your sub harder if you use it. Basically, use the lower power rating that is meant for long term when choosing what to enter for Pe.

To recap:

1) pull out a ruler and measure from the center of the surround (the domed part at the edge that sits highest) going from peak to peak.

2) look online and try to find a datasheet for the driver to pull the XMAX and Pe (RMS Power rating) from (unless it is on the label for the driver somewhere).

Once we deal with that, you should be ready to rock.

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