Can anyone explain to me what causes this subwoofer response

[pjpoes]

Can anyone explain to me what causes a maximum SPL response in WinISD to look like this. I see it often with certain types of speakers, and was wondering what exactly causes the less than even shape. My assumption is that some aspect of the speaker is causing it to be limited in the maximum output it can achieve at that frequency, and then the sudden peak at the end is the port. However, if anyone can give me more specifics about what in the woofer causes it, or if its a problem with the design of the box, let me know.

[Rademakers]

My assumption is that some aspect of the speaker is causing it to be limited in the maximum output it can achieve at that frequency

Indeed, and that aspect is Xmax.

It can be driver related. This is basically what you get if the mechanical powerhandling is lower than the electrical powerhandling at those frequencies. Such graph is often seen with budgetairy speakers, as excursion is one of the primairy victims. Or speakers with much higher Pe than needed.

It can also be due to the design of the box i.e. the volume is too large and/or the tuning is too low. You might be aspecting to much from a particulair driver. Tho I´ve seen it mostly related to the low budget speakers.

Wkr Johan

[pjpoes]

Thanks for the input, I figured it was something like that. That was a graph from an Eminence Pro Audio Driver I believe which is actually made by Adire Audio, the Lab 12 I think.

I have also noticed that drivers from Parts express, like the Dayton Refrence Series subs do that in most setups. I tried smaller boxes with higher tunings and the tuning that gives the flatest response also gives that look. Ah well, I'm sure its not a big deal.

[Ron E]

Look at the excursion curve and notice the similarities - all that means is that the driver is excursion limited. It says nothing at all about the driver.

[owdi]

It can be driver related. This is basically what you get if the mechanical powerhandling is lower than the electrical powerhandling at those frequencies. Such graph is often seen with budgetairy speakers, as excursion is one of the primairy victims. Or speakers with much higher Pe than needed.

Not really. Every vented cabinet where the Pe is not an absurd number will look like that. At the tuning frequency of the port, you are limited only by Pe. Above and below, you are limited by excursion.

pjpoes - the max SPL plot is pretty useless, even for maximizing SPL.

Dan

[pjpoes]

Thanks I always wondered as my real world results never matched well with the max spl plot. I use the SPL plot instead to know max spl and compare it with Xmax to get an idea of the loudest linear response I can get. This always is very close to my real world results. Only thing I find is that for the most part I can slightly exceed the xmax without having noticable inroom distortion, allowing me a bit louder free air response than predicted, but we are talking 2-3 decibles max.

I asked because I was just curious about the image, and wanted to know so that I can better understand the graphs I look at. Thank you again.