Simulated Measurements Part 2

I just so happen to have a cabinet the same size as the one I've been modeling, and with a baffle routed for the RS28 and RS150--just a coincidence, probably. I mounted the drivers in the cabinet, put it on a stand in the middle of my office and measured the drivers on-axis at a distance of 1 Meter. I used JustMLS to make the measurements, and used the free version of Praxis to display the graphs. The measurements are smoothed at 1/12 octave.

Not bad, if I may say so. The response is very similar in the driver's passband (let's say, between 1500 - 20,000 Hz). The only noticeable difference is that the drooping top end in my measurement is not as pronounced as it is in the simulation. But in reality, the drooping upper treble response of the RS28 is audible; and would probably show up in a measurement if I moved the microphone a few degrees off-axis.

Again, a lot of similarities. First off, notice that the cone's "signature" breakup mode (the 3 mountainous peaks) is about the same in both the simulation and measurement. This tells us that there is a good level of consistency in the cone material from the manufacturer's spec unit to my own. Next, let's look closely at the response of the driver from 200-3000 Hz. The simulation very closely approximates the response of the actual measurement; the only discrepancy is that the baffle step roll-off is steeper in the measurement than the simulation. But still, it's within 1-2 dB difference. In fact, the only noteworthy difference between the two graphs is that the simulation actually accounts for the bass response, where the measurement simply rolls off to infinity below 200 Hz. This goes back to how I was saying that it's very difficult to measure bass frequencies "anechoically" below 200 Hz. (There are tricks to measuring the anechoic bass response such as "ground plane" and "nearfield splicing," however these are advanced topics in measurement). In other words, the simulation has the advantage here, because my measurements are useless below 200 Hz.

Seems very close to me. Give Dayton good marks on driver consistency once again, as my measurements are extremely close to the manufacturer's spec.

Overall, we're still pretty close. There are two points to quibble over. First of all, the vented box tuning--shown by the double humps in the lower frequencies--does not quite match up between the simulation and the measured box, as mine is tuned slightly higher. This is my own fault, however, because I cut the vent 1/2" too short and didn't bother to fix it (hey, no one's perfect!). Second, the inductance rise on the simulation is steeper than the actual measurement. This is caused by the fact that drivers actually exhibit different inductance values at different frequencies, and--believe it or not--you can actually compensate for this in Response Modeler if you want to by using the "Overlay Imported ZMA function." For additional information on how to do this, view the included User Guide in Response Modeler (if you haven't already).