Hi, does anybody know who makes any good quality flat surface 8" passive radiators? I see that Parts Express has something in 10" and a non flat surface 8", but I was hoping to have both characteristics for my project.
Alternatively does anybody have a set of 4 long throw flat surface 8" woofers with rubber surrounds that have blown voice coils? I could hack them up into passive radiators (trying to keep costs reasonable here, and don't want to tear up perfectly good drivers).
This is for an idea I have for a BR, only using passive radiators instead of ports, adding my ideas for enclosure compliance enhancement and crossovers for a compact system that plays like one twice its size.
Thanks in advance.
Alternatively does anybody have a set of 4 long throw flat surface 8" woofers with rubber surrounds that have blown voice coils? I could hack them up into passive radiators (trying to keep costs reasonable here, and don't want to tear up perfectly good drivers).
This is for an idea I have for a BR, only using passive radiators instead of ports, adding my ideas for enclosure compliance enhancement and crossovers for a compact system that plays like one twice its size.
Thanks in advance.
or for your home turf B&W A.D.R zz6416 8 inch Passive Radiator | eBay
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-492
oh flat surface....
all i can think of is
http://www.google.co.uk/search?q=Ce...g&biw=1366&bih=675&sei=2a3fT8vqBMKn0QXO_eGgCg
or you could get a cone PR, and modify it to be flat... using a round flat light object, and some foam filling....
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-492
oh flat surface....
all i can think of is
http://www.google.co.uk/search?q=Ce...g&biw=1366&bih=675&sei=2a3fT8vqBMKn0QXO_eGgCg
or you could get a cone PR, and modify it to be flat... using a round flat light object, and some foam filling....
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This might be what you are looking for:
10" Passive Radiator Speaker Repair Kit
The frame OD is 10", but because of the large surround it is more like a large 8" PR.
Pretty affordable, too.
-Charlie
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Hi,
I was going to suggest the possibility of making your own PR's using
refoam kits but the above kit seems to tick all the boxes. I've heard
of speakers where the ABR is simply built into box wall openings.
rgds, sreten.
I was going to suggest the possibility of making your own PR's using
refoam kits but the above kit seems to tick all the boxes. I've heard
of speakers where the ABR is simply built into box wall openings.
rgds, sreten.
DC-PI
For best results, [Sd] of the passive radiators should be twice that of the driver(s) used.
See Small [1] & Olson[2] for the design regimen.
[1a] Passive-Radiator Loudspeaker Systems Part 1: Analysis
Small, Richard H.
JAES Volume 22 Issue 8 pp. 592-601; October 1974
AES E-Library: Browse Entire Database
[1b] Passive-Radiator Loudspeaker Systems, Part 2: Synthesis
Small, Richard H.
JAES Volume 22 Issue 9 pp. 683-689; November 1974
AES E-Library: Browse Entire Database
[2a] The Drone-Cone, Phase-Inverter Loudspeaker
Olson, Harry F.
JAES Volume 21 Issue 7 pp. 582, 583; September 1973
AES E-Library: Browse Entire Database
[2b] Recent Developments in Direct-Radiator High-Fidelity Loudspeakers
Olson, Harry F.; Preston, John; May, Everett G.
JAES Volume 2 Issue 4 pp. 219-227; October 1954
AES E-Library: Browse Entire Database
For best results, [Sd] of the passive radiators should be twice that of the driver(s) used.
See Small [1] & Olson[2] for the design regimen.
[1a] Passive-Radiator Loudspeaker Systems Part 1: Analysis
Small, Richard H.
JAES Volume 22 Issue 8 pp. 592-601; October 1974
AES E-Library: Browse Entire Database
[1b] Passive-Radiator Loudspeaker Systems, Part 2: Synthesis
Small, Richard H.
JAES Volume 22 Issue 9 pp. 683-689; November 1974
AES E-Library: Browse Entire Database
[2a] The Drone-Cone, Phase-Inverter Loudspeaker
Olson, Harry F.
JAES Volume 21 Issue 7 pp. 582, 583; September 1973
AES E-Library: Browse Entire Database
[2b] Recent Developments in Direct-Radiator High-Fidelity Loudspeakers
Olson, Harry F.; Preston, John; May, Everett G.
JAES Volume 2 Issue 4 pp. 219-227; October 1954
AES E-Library: Browse Entire Database
Hi -
Well, I decided to go the 'build your own' route after all. I just ordered 4 8" rubber surround repair kits, and will look for a suitable flat rigid board material to use as the diaphragm once I model the masses needed. The 10" kit looks really good and the price is nice for it, but I wanted to stay with a rubber surround insead of foam and I plan to put the whole works in a box I hope to keep 10" or less in width. I wanted to go with a flat diaphragm to use as much interior cabinet volume as possible (I know, nitpicky, but I think a flat passive radiator panel looks cool, also).
I'm planning to probably use a B&C 8" woofer, but am open to other neodymium magnet high efficiency relative high excursion options here so there shouldn't be an issue with the relative passive radiator area as far as excursion limitations, but just to keep it interesting, I am planning to do this design as a dual chamber passive radiator system. The internal port will probably be conventional.
Well, I decided to go the 'build your own' route after all. I just ordered 4 8" rubber surround repair kits, and will look for a suitable flat rigid board material to use as the diaphragm once I model the masses needed. The 10" kit looks really good and the price is nice for it, but I wanted to stay with a rubber surround insead of foam and I plan to put the whole works in a box I hope to keep 10" or less in width. I wanted to go with a flat diaphragm to use as much interior cabinet volume as possible (I know, nitpicky, but I think a flat passive radiator panel looks cool, also).
I'm planning to probably use a B&C 8" woofer, but am open to other neodymium magnet high efficiency relative high excursion options here so there shouldn't be an issue with the relative passive radiator area as far as excursion limitations, but just to keep it interesting, I am planning to do this design as a dual chamber passive radiator system. The internal port will probably be conventional.
Unstable Design
Without a spider the PR will be unstable. A surround alone suspension will not prevent a non-pistonic rocking motion from occurring.
Here are some samples of what is available:
http://www.parts-express.com/wizards/searchResults.cfm?srchExt=Cat&srchCat=527
Regards,
WHG
Without a spider the PR will be unstable. A surround alone suspension will not prevent a non-pistonic rocking motion from occurring.
Here are some samples of what is available:
http://www.parts-express.com/wizards/searchResults.cfm?srchExt=Cat&srchCat=527
Regards,
WHG
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That depends, assuming equal excursion should should be twice,
but the real number is total volume displacement should be twice.
rgds, sreten.
Hi,
Not necessarily. Depends on a few things and a spider is not strictly needed.
A double (surround) suspension can help. B&W built a flat rectangular one
with what resembles a hinge dow one side and a surround for the rest.
rgds, sreten.
Something to think about. Half of me says the force applied will be uniform, so a single suspension should work. The other half of me is quite understanding of teeter-totter under heavy load of a driven cone. Guess you'll just have to let us know. I am assuming you are going to use something like 1 inch rigid foam board? Balsa is too heavy solid, but you could carve dimples in it to get the mass down and maybe have more rigidity. Any idea what the mass is going to need to be? You could use two surrounds, one on each side of the board, and if opposing in curve, maybe cancel some non-linearity.
But if a piece of foam board and two surrounds all glued into just a hole in teh box, quite elegant. No basket, cheap.
Contraindicated
I am well aware of that fact. But the recommendation of doubling PR [Sd] remains unchanged. The reasons for this are three fold:
1) The PR is operated at much lower and narrower frequency band than that of the driver; thus, there is no acoustical reason to make it smaller.
2) The larger PR [Sd] has a superior acoustical impedance match to that of the air surrounding it.
3) Suspension elements (surround and spider) are operated well within their linear elastic range.
Regards,
WHG
I am well aware of that fact. But the recommendation of doubling PR [Sd] remains unchanged. The reasons for this are three fold:
1) The PR is operated at much lower and narrower frequency band than that of the driver; thus, there is no acoustical reason to make it smaller.
2) The larger PR [Sd] has a superior acoustical impedance match to that of the air surrounding it.
3) Suspension elements (surround and spider) are operated well within their linear elastic range.
Regards,
WHG
Hi,
True. That way is best, but not IMO for the reasons given.
Its true given typical driver parameters, but not always.
Nevertheless there are plenty of examples with equal Sd
and say a PR one size higher, and the given fact is always
true, its Vd, not Sd, that needs to be double. Excursion
linearity counts not just Sd, double Sd with poor Xmax
is no better than Sd with x3 linear Xmax in reality.
rgds, sreten.
Rock-On!
If the suspension does not consist of dual compliances, separated by some axial distance, the PR diaphragm will most likely exhibit a rocking motion at system resonance. When that happens, air displacement becomes non-linear and the single compliance will become overstressed. Whether the second compliance is called a spider or not is a pedantic issue.
With a strobe light and signal generator you will be able to see the rocking.
Regards,
WHG
If the suspension does not consist of dual compliances, separated by some axial distance, the PR diaphragm will most likely exhibit a rocking motion at system resonance. When that happens, air displacement becomes non-linear and the single compliance will become overstressed. Whether the second compliance is called a spider or not is a pedantic issue.
With a strobe light and signal generator you will be able to see the rocking.
Regards,
WHG
Ad Nauseum
I suspect due to the repetitious argument presented here, [Vd] = [Sd]*[Xmax], that your issue is really a non-acoustic one. There is never just one dead sheep at the bottom of the cliff; so the "plenty of examples" argument remains unconvincing as well. If you do not like the advice given, then just ignore it.
Regards,
WHG
I suspect due to the repetitious argument presented here, [Vd] = [Sd]*[Xmax], that your issue is really a non-acoustic one. There is never just one dead sheep at the bottom of the cliff; so the "plenty of examples" argument remains unconvincing as well. If you do not like the advice given, then just ignore it.
Regards,
WHG
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Hi,
I cant argue the exact details. Was a problem with dome midranges
years ago I recall, at the time requiring dual suspensions to prevent
it, but I assume it can be prevented nowadays for dome midranges.
It is certainly an issue regarding PR's, and in the past I've recommended
against single suspension PR's over dual suspension for that very reason.
I don't know about the 10" PR kit. Making your own with (foiled) structural
foam I would go for dual suspensions, much like the old Celestion PR's.
rgds, sreten.
More on Rocking
Rocking happens when wave length becomes comparable to diaphragm dimensions. It is particularly pronounced when only a single compliance is used, as in the case of a compression driver, or when the whole diaphragm itself goes into a (-.+) mode, as in the case of a snail shell auto horn with a metal diaphragm. What is surprising is that the mode does not rotate, even though the diaphragm and suspension are bounded by concentric circles.
Regards,
WHG
Rocking happens when wave length becomes comparable to diaphragm dimensions. It is particularly pronounced when only a single compliance is used, as in the case of a compression driver, or when the whole diaphragm itself goes into a (-.+) mode, as in the case of a snail shell auto horn with a metal diaphragm. What is surprising is that the mode does not rotate, even though the diaphragm and suspension are bounded by concentric circles.
Regards,
WHG
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