Passive Radiator and Sub Enclosure Vibration

[dwell]

I am considering building a sub using the Peerless 830452 10" subwoofer and 840841 10" passive radiator. I mostly will be listening to music and sometimes will use for HT at reasonable levels. I have downloaded UniBox and am playing with different configurations and the choice using of one or two passive radiators is the first major design decision.

My question is how much is the combination of a single sub and single PR going to want to vibrate because of the weight of the PR? All other factors aside am I better off using two PR's and locating them on opposite sides of the enclosure or going with one PR? I don't want my subwoofers dancing across the floor. What have your experiences been when working with passive radiators?

Thanks in advance for any input you can give.

[Asdonk]

hello there
I have build a 31 litres cabinet with a peerless xls10 (830452)and 2 PR s (830481)
the 2 PR s are giving much more vibration then a xls10 with 1 PR
I know this because I have also the xls10 with 1 PR
the xls10 with 2 PR is tune to 25 hz, with test signals it starts shacking like a washing machine at about 26-27 hz
first I have removed the spikes and put the subwoofer onto small
rubber feet, this gave a much better result
another thing is that with 1 PR you can tone the subwoofer to 20 hz very simpel
with 2 x PR you will not get that -3db, more like 25 hz which is good enough with music
with 2 x PR I use the 400 gr PR, almost like the Sonus Faber B1 Gravis subwoofer

[Svante]

10" XLS with 1 PR in a 14 liter box:

http://www.tolvan.com/lillkub.AVI

[Asdonk]

14 liters, that is very small
what -3db is it tuned to

[Svante]

Well, the box was not intended to use "as is". It was an experiment of a collegue of mine with electronic compensation, and the "walking" was a funny side effect that we found. For some measurements he actually had to stand on the box to keep it still.

[John_E_Janowitz]

Take a look at the PR FAQ first. This will help answer a lot of your questions.

http://www.aespeakers.com/phpbb2/vie....php?f=4&t=549

Couple things to comment on. You should have PR's that displace a minimum 2x the air that the woofer does or you will run out of excursion on the PR. The other option is to give a very stiff suspension on the PR so you can't bottom it. All you are doing in that case though is taking away output, which is not a good option. The stiffer the suspension, also the more mass you need to get the same tuning, so you have more wear and tear on the suspension. PR's should have the softest possible suspension as to more closely approximate an ideal port.

PR's due to high mass can create a lot of force on the cabinet. Opposing PR's cancel the net force on the box so it doesnt' move. Carver's first little Sunfire sub would walk all around the room and at times even unplug itself due to this issue.

John

[Asdonk]

xls10 with 1 PR in appr. 31 liters will work

http://vikash.info/audio/xls10/

[dwell]

John, Thanks for the link to the PR FAQ, I had not found that one. Very helpful.

Asdonk Thanks for the info and links.

I am probably going to use two PR"s one each on opposing sides of the enclosure.

My current main speakers (Sonus Faber Concertos) are on stands and one option is to build a pair of subs that will be close to the same width as the existing speakers then place the speakers on top. As my speakers are relatively narrow this will require the amp, driver and PR's to be located on the sides of the relatively tall and narrow enclosure. I'll do some box design and volume calcs and subtract bracing, speaker, PR and amp volume and see if this is feasable.

Thanks again!

Alan

[Asdonk]

hoi Alan

sonus faber uses the xls10 woofer in a 28 litres enclosure with 2 x PR, one on each side, you can simulate this in Unibox
but I do not know if the xls10 was used )830452' or a custom made xls10

[Cal Weldon]

Originally posted by John_E_Janowitz
You should have PR's that displace a minimum 2x the air that the woofer does

Agreed.

Originally posted by dwell
I am probably going to use two PR"s one each on opposing sides of the enclosure.

Excellent idea.