Encloseure size, PE vs Win ISD...

[brad1138]

Every driver from PE has optimum enclosure size from "BassBox 6". But it is usually way off from what Win ISD suggests. For example, Dayton Audio RSS265HF-4 10" Reference HF Subwoofer 4 Ohm has a recommended size of 0.53 Ft3,(Which seems really small to me), while WinISD says 1.3 Ft3...

Which one do I believe?

[Steve Lee]

I have the same issue and find it easy not to believe either of them at times.

Can anyone please attempt to offer a good explanation concerning the differences in the suggested alignments and do it well enough that the response could be made into a STICKY for permanent viewing?

[tomzarbo]

I think PE uses the "optimum" enclosure size in BassBox, which is auto-generating after Parameters are entered. It looks at the numbers and automatically calculates what it thinks is the best all around box size for each. That just gives you a rough idea for a quick peek when browsing through various drivers though, I wouldn't use it as fact for making your own box from. WinISD will do the job for that.

TomZ

[johnnyrichards]

All modeling software begins with any of a number of assumptions. Up to the user to understand what effect those assumptions have on the outcome.

[devnull]

Don't trust the speaker parameter database in any design software. I and others have seen numerous mistakes. Always enter the driver parameters yourself,

[fpitas]

I'd certainly trust WinISD a lot more, especially if the response curve it showed me was what I wanted. I also try things out in other programs like AJvented or AJsealed for a sanity check. But you're the designer. It's up to you to make the final call.

[anunnaki]

I have found WinISD to be very accurate for modeling. I use the suggested alignment as a starting point and tweak the design from there keeping a close eye on the compromises made from any changes.

it recently worked extremely well even with more complex designs such as an isobaric passive radiator alignment I did.

[LOUT]

Many speakers are also pretty flexible where you can use a different box size depending on what YOU want from them for bass-extension VS size VS max SPL VS delay etc..
I wouldn't necessarily say BassBox6's suggestion is conflicting with WinISD unless they give noticeably different results for the same driver in the same box size. I'd describe it more like they have different "ideals" in mind when forced to choose one enclosure size for a driver rather than showing the whole range of sizes that can work well with it.
I am curious what different things each sim takes into account and which aspects they might completely ignore when making a specific automated result like that.

[fpitas]

Yes, it's all about compromises. The (small) elephant in the room is that PE probably would rather not report larger box sizes, since that can be discouraging to some people.

[billfitzmaurice]

With a ported enclosure WinISD defaults to the maximally flat alignment, whatever that may happen to be. With sealed it defaults to 0.7 Q. It seems that the PE recommended sizes are on the small side, as driver buyers tend to want to go to the smallest box size possible.

[Steve Lee]

Thanks guys!

I think you have clarified this quite well.

[Chris Roemer]

There aren't TOO many Dayton drivers that I don't have at least 2 sets of measurement on - BOTH from PE !
With the WT/DATS, and the more recent OMNImic; it seems as though PE runs out new measurements (F/Z and T/S parms) on most drivers every 2 or 3 yrs. or so.
That's great for us DIYers, as long as you use the latest info. PE's "Woofer Selection Guide" hasn't had its driver DB updated in almost forever.

Also, there are SOME drivers (if you measure them yourself) that aren't very close at all to the published T/S parms.
Sometimes that makes a big diff. (in a box model), sometimes next to none at all. It depends.

[Whitneyville1]

When I've enter PE's Bass Box enclosure sizes into WinISD I can clearly see the compromises they make. For instance, a 12" Titanic III by PE's numbers give a 2.33 CU. Ft. enclosure. Win ISD suggests closer to 4 cu.ft. Is either one "wrong". No, but they different assumptions of what you want in the final product. When you play around in WinISD, you might choose a compromise of about 3 cu ft. if it fits your size and response requirements. The late Lou C.'s Veepers are my "critical listen monitors. He gave up quite a lot of bass response of the Peerless 830875 to go for the lowest distortion and a smooth response. Used with a sub, they are an outstanding monitor. So there are few "wrong answers" just choices.