Adjustable passive radiator series tuned 6th order.

[Ridinhi 5,000+ posts]

I think I have my tuning down now. I should be at around 30 HZ. I will do a little weighing of my washers and see what I’m tuned at, but it sounds pretty good. Did a couple of videos. 3 of my screws are basically just floating, which you can hear a little in the video. This is what people mistake for ”rattling” often. It’s actually air squeaking out of the hole. The video makes it sound even more like a rattle. i used small 1.5 inch drywall screws, but now that tuning is almost done those will all be replaced with larger screws to plug all the leaks. I took the radiators out 9 times today and changed weights and played with tones and music.

What size is the enclosure?

 

[SlugButter]

Rather than weighing the washers, you can run test tones and see what frequency the sub "stops" moving at.

I need to weigh them. Once I figure out how much mass I want, I’m using the factory weight still, which is 255 grams. Every 1/2 inch drill hole removes 9 grams from the mass. I have to drill the holes as symmetrical as I can on the weight so the radiator cone stays linear.

 

[SilverSquared 10+ year member]

I need to figure out how much mass I want, Every 1/2 inch hole removes 9 grams from the mass.

Quoted you just to tell you...2 pints of whiskey and your name changes to ButtSlugger.
I love the goods you're using. I am aiming to use these passives or the Dayton ones in
my Hellcat once I build its system. Good work!

 

[Jimi77 5,000+ posts]

I need to weigh them. Once I figure out how much mass I want, I’m using the factory weight still, which is 255 grams. Every 1/2 inch drill hole removes 9 grams from the mass. I have to drill the holes as symmetrical as I can on the weight so the radiator cone stays linear.

I see. Is there a reason you can't just use a smaller washer(s) in place of the original one?

 

[SlugButter]

I see. Is there a reason you can't just use a smaller washer(s) in place of the original one?

I sure could. I’d have to use different sizes to weight it out and make sure they are exactly centered, but that is totally possible with these.

 

[SlugButter]

Finished up with the weighting and put the big boy screws in. Each radiator has 200 grams of added weight for an enclosure tuning of 29 HZ and a radiator FS of 16 HZ. Doing a front cover for it next and the front chamber after that.

 

[SlugButter]

I really need to just make a new rear floor for the car out of wood. Work has destroyed the carpet back there.

 

[Jimi77 5,000+ posts]

How you liking the radiators? I'm considering using them in a future set up. Do you really need 2, they supposedly have a ton of throw.

 

[SlugButter]

Or maybe see if 3 or 4 cans of be

How you liking the radiators? I'm considering using them in a future set up. Do you really need 2, they supposedly have a ton of throw.

Use 2 usually. What you want to do to get what you need for a passive radiator is calculate a normal ported box with a big enough port to get about 20 meters per second of port velocity. Then, take HxWXL of that port and divide it by 47 to get CM. That will give you air displacement needed. Now take SD X xmax of your radiator and make sure it’s as much as the port would be. The radiator needs to displace that much air or even a bit more so you don’t have to push them to max.

 

[SlugButter]

The box size also gets a little larger with 2 radiators. It’s a bit of a dance, but 2 always seems to work better than 1.

 

[mat3833 10+ year member]

How you liking the radiators? I'm considering using them in a future set up. Do you really need 2, they supposedly have a ton of throw.

2 is technically unnecessary, but the way it was explained to me(from a home theater perspective, doesn't translate exactly) is as follows:

For a given sub size tuned into the high 20s you will want to either run a PR one size bigger(Ex 12" sub = 15" PR) or run 2 PR of the same size. The benefit of running 2 PR is you can place them on opposing sides of the enclosure to cancel out the vibration they can cause.

A port moves a TON of air at tuning. So you would want a PR with 1.5x more Xmax than your sub has at minimum.

Passive radiator enclosures are more art than science. Each PR behaves slightly different than another and it will usually take a bit of tuning and testing to get it to perform how you want. They also don't model very well because there are a ton of variables that need to be taken into account.

Matt

 

[Buck 5,000+ posts]

2 is technically unnecessary, but the way it was explained to me(from a home theater perspective, doesn't translate exactly) is as follows:

For a given sub size tuned into the high 20s you will want to either run a PR one size bigger(Ex 12" sub = 15" PR) or run 2 PR of the same size. The benefit of running 2 PR is you can place them on opposing sides of the enclosure to cancel out the vibration they can cause.

A port moves a TON of air at tuning. So you would want a PR with 1.5x more Xmax than your sub has at minimum.

Passive radiator enclosures are more art than science. Each PR behaves slightly different than another and it will usually take a bit of tuning and testing to get it to perform how you want. They also don't model very well because there are a ton of variables that need to be taken into account.

Matt

Yeah there’s a lot of energy that comes from chamber pressurization at tuning, where like the cone movement can be relatively little, but the energy transfer trying to come out the box is so high. There’s only a certain power level you can run with a sub before you need a ton of PR’s.

 

[mat3833 10+ year member]

Yeah there’s a lot of energy that comes from chamber pressurization at tuning, where like the cone movement can be relatively little, but the energy transfer trying to come out the box is so high. There’s only a certain power level you can run with a sub before you need a ton of PR’s.

Yep, the awesome thing about PRs is they can have crazy high Xmax with pretty basic stuff. The 9" Spiders are good for almost 3"(76mm) of excursion peak to peak with the right basket and a 2" coil. Get yourself a 10 or 11" spider with that same coil and you can have a 15" PR with damn near 4.5" of excursion capability. The issue becomes managing weight and keeping things under control.

I was looking at having a pair of 18" PRs made with 11" Spiders and 2.5" "coils". Safe excursion was quoted at 115mm peak to peak. That's just bonkers.

I'd love to build a PR box with the 5100's driving them. But I would need space for 4-18" PRs and that's a bit much, lol.

Matt

 

[Jimi77 5,000+ posts]

Or maybe see if 3 or 4 cans of be

Use 2 usually. What you want to do to get what you need for a passive radiator is calculate a normal ported box with a big enough port to get about 20 meters per second of port velocity. Then, take HxWXL of that port and divide it by 47 to get CM. That will give you air displacement needed. Now take SD X xmax of your radiator and make sure it’s as much as the port would be. The radiator needs to displace that much air or even a bit more so you don’t have to push them to max.

Thanks.

 

[SlugButter]

Started on the front cover tonight. Didn’t have much time, but I got it drawn out, cut and started cutting the aluminum bar inserts. It took 3 beers long to do this.