Hi,
I just got rid of 2 Boston G5 10" and got a G5 12" + radiator. I'm building a box in my tyre well (only 130mm deep) so i'm going to mount the G5 inverted and the radiator flat. The box is out of fibreglass with a flat top where the drivers are and molded bottom to the curves of the tyre well. its around .9 cu ft (boston recommends 1 but i though i take some away as the driver volume is included with this figure).
My question is, has anyone had experience with radiators and their effects to SQ?
Full Version: Passive radiators?
My primary concern with this idea is the passive radiator is mounted vertically.
Generally speaking since you are using a larger passive radiator than the driver cone the weight of the passive cone is sufficient to control the resonance at Fs, allowing a better roll-off and extended bandwidth control. The passive radiator allows a 29 degree roll off slope compared to say a reflex system of 24 degrees, and at this juncture is 180 degrees out of phase to the driver. This is not a problem (normally) as the driver phase inverts at Fs.
With the passive cone having this close a ratio to the driver (In this case 1:1) there is a distinct possibility of incurring a notch at the lower end of the roll-off, this can be audible and may require a filter to remove it. This "effect" (notch or dip) at the passive radiator own resonance, is located below system cutoff, the notch increases the slope of the low frequency roll-off, and degrades transient performance.
The big advantage is the ability to adjust the response to suit the cabin, which possibly only the reflex system can offer, however with less ease.
Generally speaking since you are using a larger passive radiator than the driver cone the weight of the passive cone is sufficient to control the resonance at Fs, allowing a better roll-off and extended bandwidth control. The passive radiator allows a 29 degree roll off slope compared to say a reflex system of 24 degrees, and at this juncture is 180 degrees out of phase to the driver. This is not a problem (normally) as the driver phase inverts at Fs.
With the passive cone having this close a ratio to the driver (In this case 1:1) there is a distinct possibility of incurring a notch at the lower end of the roll-off, this can be audible and may require a filter to remove it. This "effect" (notch or dip) at the passive radiator own resonance, is located below system cutoff, the notch increases the slope of the low frequency roll-off, and degrades transient performance.
The big advantage is the ability to adjust the response to suit the cabin, which possibly only the reflex system can offer, however with less ease.
The advantage of the passive radiator is extended low freq. power handling because it prevent the woofer from unloading below Fs.
should work fine.
as for notches and peaks, it'll be outside the audible range, as long as Xmax is not exceeded.
should work fine.
as for notches and peaks, it'll be outside the audible range, as long as Xmax is not exceeded.
i've read that you should use a smaller active driver with a larger radiator, but i spoke with boston and they said to use the 12" radiator with the 12, and 10" radiator with the 10? I'm little confused now, is this information correct?
I'd have thought the best option is to use a matching one.. Peerless say to use the same size.
http://www.tymphany.com/datasheet/appview.php?id=28
http://www.tymphany.com/datasheet/appview.php?id=28
i think its in case when the manufacture of he driver doens't offer a radiator, so you may have to find a different radiator. If both boston and peerless say match them, thats good enough for me. Can't wait to test the box out.
Advantage of a same sized driver is the MANUFACTURER can use a similar surround, cone, and basket for both and cut down costs. Since cost is the main concern this is a wise decision.
However from a audiophiles perspective a lossy surround and spider on a much larger passive radiator pays high dividends.The advantage is the resonate notch is OUTSIDE the passband. The other advantage is the passive radiator is non-linear in respect to the driver. This allows for tuning over a significantly wide bandwidth. This requires a specific passive radiator made for this application, and you CANNOT use a larger drone clone for this. There are some other advantages as well, but I suspect non of this would be of interest to you.
Make sure to use a suitable active filter for the notch.
However from a audiophiles perspective a lossy surround and spider on a much larger passive radiator pays high dividends.The advantage is the resonate notch is OUTSIDE the passband. The other advantage is the passive radiator is non-linear in respect to the driver. This allows for tuning over a significantly wide bandwidth. This requires a specific passive radiator made for this application, and you CANNOT use a larger drone clone for this. There are some other advantages as well, but I suspect non of this would be of interest to you.
Make sure to use a suitable active filter for the notch.
Thanks for the above info. i've also read that the phase could be out. Is this due to installation? or just design.
design - both should be in the same plane to avoid phase cancellation.
abmo - missed you man 
passive radiators also have a large group delay
QUOTE (Pulse-R @ Sep 24 2006, 01:32 PM) 
design - both should be in the same plane to avoid phase cancellation.
yeah, they are both on the same plane. We'll just have to wait and see. I'm looking forward to it as this isn't a very popular solution for car audio.
Finally got them installed and sound deadened the boot. Have to say, the results are amazing. Sub bass is now smooth and very, very deep but still punchy and tight. 
Can't even really tell there is a sub there. I ended up using a .9 cu foot box which is glassed into the tyre well. I'll post pics in the thred soon. now i just have to get rid of those annoying viarabtions in the doors 
Can't even really tell there is a sub there. I ended up using a .9 cu foot box which is glassed into the tyre well. I'll post pics in the thred soon. now i just have to get rid of those annoying viarabtions in the doors
QUOTE (Pulse-R @ Sep 23 2006, 11:31 AM)
The advantage of the passive radiator is extended low freq. power handling because it prevent the woofer from unloading below Fs.
should work fine.
as for notches and peaks, it'll be outside the audible range, as long as Xmax is not exceeded.
should work fine.
as for notches and peaks, it'll be outside the audible range, as long as Xmax is not exceeded.
i've always wanted to find out more about this actually. especially seeing as I bought gspot's old G5 and radiator.
can you explain how the radiator extends low frequency power handling? do I need to use an infrasonic filter below the frequency the radiator is tuned to?
cheers!
PR for all intents and purposes has similar response to using ported. However unlike ported where, where when you play below tuned freq, it looses all air suspension for the driver and sub can unload. PR still retains air suspension for driver when a note plays below tuned freq, thus increasing power handling significantly below tuned freq, as a ported box has virtually zero power handling at these freqs
peace
Cyberpunky
peace
Cyberpunky
hence, do I set my filter at, say, 5-10Hz below tuning, or do I switch it off completely?
you dont need it, but i run one @15Hz just to stop wasting amp power, anywhere between 10 -20 Hz should be fine...if you running PR then Id go 20Hz as not much point trying to go lower with that config
peace
Cyberpunky
peace
Cyberpunky
Thanks Cyberpunky you're a champ. been wanting to know the answer to this one for quite a while...
you coulda asked... thread miner!!
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