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- DrewsBrews 7:42PM
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Passive Radiators
I have built a bunch of speakers with PRs. Not to beat a dead horse but, the Stealth Force Ones had PRs and after playing the piss out of them at high volume, they are smoothing out it seems. I haven't measured them yet from my previous measurements but, I think they are finally breaking in. They don't sound quite as boomy,like they did on Saturday in Indiana.
I am listening to some old Metal like Loudness, Iron Maiden, Dio etc. A lot of that stuff lacked lowend any way but, the remasters seem to take away more, lol!
I always like Aja from Steely Dan. Hard to tell if there is too much bass there. So many remasters.
The other one I use is Rush, Moving Pictures. I know how that bass drum should sound.
New recordings.....lol! I guess I don't listen to new stuff, although, I think Ads sound better these days but maybe not. Some of them sound horrible.
If you made it this far, what are your experiences with passive radiators?
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I want add, I never had a peak 1 octave above tuning, which I have. Listening to Aja, too much low end. Other PR designs I have done, no problems.
As with much of box tuning and alignment, you have to do the modeling and simulation before the build and measurements after the build to get what you want.
Yep, model, build, measure to verify, listen to voice. Sometimes ya don't know what ya got 'til ya measure. Sometimes ya got what ya modeled, but it sounds bad. Sometimes, yer model, yer ears, and yer measurements match.
Have you ever used a tune checker? I have a driver connected to a tube on a flat surface with craft-foam on the flat and around the tube. This way I can check tuning without cutting driver holes for ports and PRs. I recommend a 5.25" or larger for this task, but who doesn't have a single spare laying around?
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Hell no, lol! Never did that. Never heard of it!
Funny thing is,I can design a system with WinIsd, it will be perfect. Other times it will be so far off, its insane. I say it's reality versus computer. Some times the computer is correct. I guess, you can say, input shit, output shit, too.
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I've never used WinISD enough to know how it works. I prefer Unibox or Jeff's Woofer and Box Designer spreadsheets. I guess VituixCad does it too.
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I certainly did this, but no way to break in the PRs without hammering them. Pretty hard to do unless you push the woofers to their limits for quite a while.
I don't know the answer, but I do know, after 6-8 months, my reference system smoothed out. This speaker, when I brought it to Indiana, the PRs were barely moved.
I put 50 watts to the woofers for an hour with the PRs. The woofers were broken in.
I had no more time to get the PRs broken in.
My reason for the post.
Has anyone had a problem with PRs until they were broken in?
Ok, that is something I never heard of...
I usually move mine by hand before installation, but you can only do so much.
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Nothing free is good.
What software should I get?
Both I listed are free, and fantastic.
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Thanks Wolf -
But now I am wondering - what does the tub
e checker do that DATs can't do?
The tune tester is used with the dats or other impedance rig. They work together.
Any box you have can be tuned, and this allows the tuning sans driver installation. Have an unknown PR? With a known box and a hole, you can measure its tuning. Simple as that.
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WinISD is notoriously inconsistent. It sometimes gets you in the ballpark, but verification is evident.
I've used passives a bunch and never had any break in issues. Though, a few of my passives were woofers with the magnets removed.
AH, that's great! I bought some buyout 12 inch PRs some years ago without T/S specs.
Now I can use them.
I received my SB 8" passive radiators on Friday. They look great but weigh almost nothing. I swear the cardboard packaging Madisound used weighed as much if not more than them. All good. I look forward to starting that project in a month or two.
What sort of specs does one seek in a woofer when deciding to go with a passive radiator build?
Any woofer that models well in a ported box will work fine with a PR.
The deciding factor is when the port is too long for the box and tuning you want.
That's where a PR excels.
A PR on the opposite side of a subwoofer will help keep the box from "walking"
Jeff Bagby also mentioned that you could tune a PR below the woofers Fs and protect
the woofer a bit from excessive excursion.
Yep small boxes with low tunes can go a bit nuts for length of a port of adequate diameter.
The air inside the box is a spring. The smaller the air volume, the "stiffer" the spring. You need a hefty force to resist that spring to get it to resonate at a low frequency. The inertia of the air mass inside the port provides this force. For a small diameter port, the inertia is locked up in acceleration force of the smaller air mass in the port moving long distances within the cycle. A larger diameter (and longer) port has more air mass so it must accerate less (and thus move less far within the same cycle) for same inertial force.
Keep scaling up that port diameter to the same dia as a PR cone... Eventually, with appropriate amount of mass, the air moves so minimally that it is within the excursion limits of a PR. The PR basically allows a bit of a "cheat" since metal weights are so much more dense than an air mass in a port that would be many feet long by that point.
Thanks, Drew!
I get it.
For my up coming project I chose to use a passive radiator instead of a port tube because of overly high port resonances (simulated). I could have fit a port in the box pretty easily, and that would have been far cheaper, but the PRs solved that port resonance issue as well as maybe some midrange leakage. The port would have been on the rear panel so I'm not sure how big of a deal it really would have been. But since these are the nicest drivers I've ever used I figure $80 for both PRs isn't a bad design choice.
Makes sense to me
My 2 cents from a fairly recent project of mine; I also found PR a bit less infringing into the mid range, and relative ease adjusting (and re-adjusting) the weights vs port lengths > a real advantage. Because of the steeper rolloff (vs port) very easy to hear a 1 note (narrow range) focus (guess I'm smitten to sealed woofers for this reason) so I'd tend to go a smidgen lower than higher (tuning) if just passive. With my PR and ported projects my preference is to roll-off the steepness with a shallow eq. Trade off a couple of low dB for realistic bass.
It is the comprising that we must do that makes this hobby so relatable to real life situations.
I was thinking of lowering my tuning as well after thinking about my problem. Maybe it will lower that peak. Funny thing is, it is 1 octave above tuning. Seems there would be an easy answer to what is causing it.
I had a ported system with an 'over active' port, and was able to adjust by putting a sock in it.
I haven't tried it on a PR system, but maybe a bit of internal damping somehow?
Or, possibly a bit of leakage out the bottom, i.e. a tightly stuffed aperiodic vent?
Are you sure that it isn't the interaction of the low crossover point and the woofer impedance peak causing the peak in response? just a thought, not questioning your design abilities. If you haven't done so, I would take a near field woofer measurement and plug your woofer crossover into your favorite modeling program, I have found that in some instances it better shows what the crossover is actually doing.
I have taken close mic measurements of both the woofer and PRs. I also have impedance mesurements but I haven't looked at the impedance in that way. Will look at it when I get home from work. Mostly I was looking at the tuning and minimums. I will post the measurements if I get time tonight. I haven't done anything with them yet but just thinking I might get rid of some resistance on the mid and tweet to level it back out. I guess I didn't break the woofers in enough, idk. They seem to be getting louder and louder as I have been playing them.
Also was thinking about raising the lower crossover. You may be right about the low crossover.
Yep. Very hard to do a low crossover point passively without introducing a hump in that region due to interaction with the rising impedance of the woofer in box. I'd second Nick's recommendation to take a near field woofer measurement. Two actually. One of just the raw woofer with no crossover connected and one with the crossover. That would be very telling.
What do you guys know about these radiators?
https://essspeakers.store/collections/parts/products/ess-factory-10-gray-flat-disc-passive-radiator
Are they just replacement cones or complete passive radiators and could they be glued to a cutout effectively if just a cone?