hi everyone, i was wondering if there is any sound difference in the passive membranes mostly used in portable speakers and passive radiators ( passive speakers with spider etc.), wich 99% of the time are used in the DIY community. the passive radiators seem to have better control because of the surround AND spider but is this really important or is this just a minor thing. passive radiators have a mass (added) limitation and are not that flat while a passive membrame can hold more (moving!) mass because the weight is more distributed over the piston erea instead of a heavy loaded spider wich can become uncontrolable( like a camper behind your car wich goes out of balance on the highway) and is way more flatter( so less space ).
I might suggest you have it in reverse. The passive membranes I am familiar with, are flat disks with only a ring mount and a surround so I highly suspect they would deform more quickly under added weight. Not to mention they are anything but linear under regular use. They flop around like fish out of water.
Let's hear what others think.
Let's hear what others think.
yes when you see them move they move out of balance but maybe that's just your vision, i don't think so but i don't know if this will change the sound quality.
Small passive membranes found in small portable speakers are just small passive radiators, so they don't have to have spiders. Their surround acts like a spider in the larger passive radiators.
A passive without a spider to guide its motion can do all sorts of out of balance motions. That makes them very non pistonic which is not what you want.
Surround of small passive membrans guides (pistonic) motion as good as spider alone in passive radiators. The point is that spider plus surround (of the regular passive radiator) provides much better pistonic movement. But we are talking here about small diameter passive membrans/radiators used in small portable speakers, so surround alone is enough. Bigger portable speakers (at least better ones) have proper passive radiators (5" or 6" diameter) with both spider and surround.
I’ve never seen a speaker with only a spider and no surround. After forty years of doing this I can’t think of one. Could you give me an example?
Try looking at one using a stroboscope, while playing appropriate sine frequencies. If different parts of it are moving like a fish flopping around, you'll see it clearly.
You misunderstood me... or I wasn't clear enough. My explanation about the "spider alone" was that small passive membranes are identical to the role of the spider alone. In conventional passive radiators, spider is providing much of the "spring" action (compliance, that is) and surround much less, but both together assures pistonic movement. On the other hand, surround of the small passive membranes provides all the needed compliance and pistonic movement (more or less) - so it is taking the role of a spider.
Believe it or not, there were and there are woofers (midbass') without surround - 24 years ago I measured and listened to a pair of Pioneer SF-21 hi-fi loudspeakers:
Look ma, no surround:
Construction of the woofer:
There is no surround, so to block the air hissing noise between the driver basket and the cone, short (?!) cylinder (with damping material) is attached to the cone, extending deep into the driver basket inside.
Some 50 years ago "edgeless" (surroundless) woofers from Fostex (SLE 20W, SLE 24W, SLE 34W, ...) were popular:
There are at least two modern hi-end loudspeakers with surround-less midbass drivers: Leedh E2 and Ilumnia Magister:
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why? do you get distortion this way, i mean they are used in jbl boomboxes worth 550$ while they "easely" could add a spider?
i want to make a custom passive membrane with a lot of weight, like a 5 inch passive with 130 grams of weight. i already make 2 for in a testbox i gonna test tomorrow and it seems the surround can handle the weight, not easely because it hangs in there and if you touch it it moves not really elastic like the surround don't act like a spider anymore( in and outward movement) but when the testbox is closed the inside air pressure will guide the membranes i guess.
Isn’t there rubbing and friction caused by the sleeve? Also air squirting out at high velocity due to the needed space bet the sleeve and frame? Unless the spiders can hold it perfectly aligned at all excursions it will rub too. I think it might have as many issues as it tries to cure. If it was that good we’d see more of this done. To be done right it would be expensive too.
No rubbing at all, gap is wide enough. Felt damping cures air noises. Pioneer driver has two spiders, so centering is not a problem. But yes, conventional suroundless desing in attempt to cure some problems unfortunately introduce different ones. Unconventional suroundless designs, like Leedh, are much better in that regard - their midbass drivers have "spider" entirely made of ferro-liquid which keeps the voice coil (and membrane) exactly centered.