Does winISD have issues modeling Passive radiators

[mackintire]

I was investigating the idea of using 2x Dayton RSS390HF-4 in a balanced opposed location in a 6.5 cf box with a single 15' passive radiator.

One driver on the left side, the second on the right side with the radiator firing towards the audience.

I was considering one of the AE PR15-700 radiators. The results in WinISDpro alpha are not thrilling and I'm suspecting that winISD is calculating the result incorrectly.


Any ideas on what other programs to try to model this with?

[evilskillit]

Unibox can be used to figure PRs as well. I think it'll give you a similar result as WinISD.

You can't use a 15" PR with two 15" subs. Generally speaking you need twice as much passive radiation as you have subbage. You'll probably need at least 1 if not 2 of the 18" AE passive radiators to get the desired effect. Those things have a lot of stroke so 1 might work, but I'm guessing two. The AE units are VERY nice from what I've seen but adding mass can be a pain so you might also check into the units from Creative Sound Solutions or Exodus Audio. I'll look into the modeling and see what I see but I'm guessing that is the main source of your problem. General rule 2x cone area of PR to sub ratio.

[mackintire]

Unibox can be used to figure PRs as well. I think it'll give you a similar result as WinISD.

You can't use a 15" PR with two 15" subs. Generally speaking you need twice as much passive radiation as you have subbage. You'll probably need at least 1 if not 2 of the 18" AE passive radiators to get the desired effect. Those things have a lot of stroke so 1 might work, but I'm guessing two. The AE units are VERY nice from what I've seen but adding mass can be a pain so you might also check into the units from Creative Sound Solutions or Exodus Audio. I'll look into the modeling and see what I see but I'm guessing that is the main source of your problem. General rule 2x cone area of PR to sub ratio.

I was suggesting 2 drivers to 1 AE PR. I was also considering that the AE PR has a ton of stroke.


Anyhow....I think I am going go a different direction the where I was heading with this.

Something more along the lines of an AV15H in an Easy Button Max and see how that goes.

[evilskillit]

A bit of toying around shows that 2 of those things in a ported box of the same size tuned to about 16hz yields the same results. The RSS390 wants a really large box to play really low, if you're wanting a lower tuning you're probably going to need a larger box for those subs regardless of whether its PR, ported or otherwise.

What exactly are your goals and expectations with what you're working on?

As much as I really love the Dayton reference drivers their 15" sub wants such a large box I wonder what it's application is. It doesn't seem quite robust enough to work in a smaller box with lots of power and EQ, for a good low tune it wants a HUGE box. You can use them for OB or IB but you can get more stroke for your dollar from AE or Fi Car Audio for those applications. Every time I consider the RSS390HF because its almost the same price as the RSS315HF I end up back at the RSS315HF because it'll work a lot better in a realistically sized box.

[brent_s]

As much as I really love the Dayton reference drivers their 15" sub wants such a large box I wonder what it's application is. It doesn't seem quite robust enough to work in a smaller box with lots of power and EQ, for a good low tune it wants a HUGE box. You can use them for OB or IB but you can get more stroke for your dollar from AE or Fi Car Audio for those applications. Every time I consider the RSS390HF because its almost the same price as the RSS315HF I end up back at the RSS315HF because it'll work a lot better in a realistically sized box.

The 390HF "prefers" a sealed alignment, IMO. 4 ft^3 with no stuffing gets you a Q in the high .7s with a natural f3 of 31hz, f10=~19Hz. From there add stuffing and/or a bigger box and it just gets better. It's like a big NHT1259 from days gone by...needing 3 ft^3 sealed for a 12" is unheard of with today's drivers, but the 1259 had a natural f3 of 31Hz back in the early-mid '90s and it only needed about 100 watts to use all of its excursion to boot.

Don't forget the 390HO if you're looking for a "small" ported 15". It'll do good things in as little as 3 ft^3 with a 20ish Hz tune...an ideal candidate for PRs given the challenge of properly porting a 15" to 20Hz in that small of a box. Big for it is still 6 ft^3 or less where most 15"s are just getting started.

-Brent

[brent_s]

I was suggesting 2 drivers to 1 AE PR. I was also considering that the AE PR has a ton of stroke.


Anyhow....I think I am going go a different direction the where I was heading with this.

Something more along the lines of an AV15H in an Easy Button Max and see how that goes.

As skillit said, it doesn't quite work that way. You want at least 2x the displacement in your PRs as your driver has as a ROT. The 390HF's rated at 14mm Xmax so you'd want a single PR with at least 28mm of one way excursion, assuming the same Sd (more excursion=bigger surround=less Sd...usually). The AE, CSS, and Exodus PRs could all probably get away with 1:1 with the 390 if you ignore its Xsus actually being more like 21mm.

In reality, depending on tuning frequency, even a 315HF can push a single Exodus PR15 pretty close to its limits if you run without the right subsonic filter. I actually have a pair of 315HF/PR15s on deck once I get through a few non-audio projects.

-Brent

[mackintire]

Thanks guys I learn something new here everyday.

[evilskillit]

If you want that size box you might want to look at the RSS390HO instead of HF. It works much better in a smaller box. Then if you want to go with PRs model them, and check their excursion with the max power you intend to send to the thing and make sure they're not flying apart.