I began a previous thread about what adhesive to use when replacing woofer surrounds to these same speakers which are Technics SBX500. Their woofers are a flat disc instead of a cone.
The surrounds attach to the disc's underside and the original surrounds had an inward roll. I could not find replacement woofer foams actually described as inward roll and I read forum posts stating that to achieve inward roll, one simply inverted a surround.
That seemed simple enough and I thought it made sense.
It took some time to find a vendor with a seemingly compatible surround and they arrived today. Instead of one pair I ordered two in case I botch a first attempt. I had my fingers crossed that they would be a perfect fit when inverted. And they are very, very close to a perfect fit but not quite. There is a slight distortion to the inner circumferance when attempting to fit this way. The only way I can make these foams work is if I install them with the roll facing outward. Based on the dimensions I was able to gleen from the woofers in their present state,, the surrounds I ordered were by far the closest match.
This photo shows the new surround loose layed onto the woofer attempting to show the profile I'd have when installing it as an outie instead of an innie.
The surrounds attach to the disc's underside and the original surrounds had an inward roll. I could not find replacement woofer foams actually described as inward roll and I read forum posts stating that to achieve inward roll, one simply inverted a surround.
That seemed simple enough and I thought it made sense.
It took some time to find a vendor with a seemingly compatible surround and they arrived today. Instead of one pair I ordered two in case I botch a first attempt. I had my fingers crossed that they would be a perfect fit when inverted. And they are very, very close to a perfect fit but not quite. There is a slight distortion to the inner circumferance when attempting to fit this way. The only way I can make these foams work is if I install them with the roll facing outward. Based on the dimensions I was able to gleen from the woofers in their present state,, the surrounds I ordered were by far the closest match.
This photo shows the new surround loose layed onto the woofer attempting to show the profile I'd have when installing it as an outie instead of an innie.
Is it a case of the replacement surrounds having an angled inner edge, rather than a flat one? If this is so, then you may have to consider purchasing another set of surrounds of the correct profile.
Can't quite tell from the photo, but looks like the surround may contact the upper edge of the honeycomb at high inward excursions. If that happens, an annoying ticking buzz sound would be heard along with louder bass lines.
You could probably tape the surround temporarily in place and push the disc in to see if that will be a problem.
I was aware of flat inner edge vs angle inner edge from the get go. Those I focused on were of the flat variety. Some vendor sites that I visited did not differentiate flat from angle inner flanges. There were surrounds offered that listed a number of compatible speakers makes/models (with cone woofers) but yet included Technics SBX500 (flat woofer). Shopping solely by speaker make and model number would have been risky.
Those that I ordered do have a flat inner contact edge.
Yes, that was a potential problem that crossed my mind when I began searching for surrounds. And FWIW, the underside of the disc has a slightly wider diameter than the top side. Approximatel 1/16" of the disc's underside edge protrudes past the the topeside edge
I thought perhaps this might give some "wiggle room" to allow clearance so an outward roll would work.
Your suggestion of temporarily fixing the surround in place to check for clearance sounds like a good one.
From an acoustic POV the outward roll generates a wide range of standing waves that can audibly'color' its upper harmonics if not attenuated by its XO whereas the inner roll yields a slighter larger effective Sd.
@weltersys
I took your suggestion to temporarily affix the surround to the woofer disc and basket. My conclusion is that the outward facing roll will not come in contct with woofer disc edges as it operates even if driven hard.
The act of handling/manipulating the new foam surrounds has created another doubt in my mind. I am wondering now if they may not be compliant enough? Too stiff in other words.
This is pure conjecture on my part as the original surrounds had pretty much become dust. So I never had the opportunity to feel them and/or assess their compliance. Consequently, since these SBX500 speakers only recently came into my possession, I have never heard them when in peak operating condition.
I sourced the surrounds from a company called Midwest Speaker Repair. They offer six different 10" foam surrounds, two of which have flat attachents, I chose the one with dimensions that seemingly fulfilled my dimension requirements to a tee.
One of the other 10" surrrounds Midwest Speaker Repair offer is described as high compliance - thinner material. I would have been tempted by that option but it's inner edge is angled, not flat and I needed flat.
The description below is that used by Midwest Speaker Repair on their website to describe the refoam kit I purchased. It is also catagorized by Midwst Speaker Repair as a "Standard Refoam Kit".
So I must soldier on with the surrounds I have and sincerely hope they are not so stiff they turn these woofers into midranges.
$22.95–$24.95
FLAT attachment to cone
A – O.D. of the surround = 9.75″
B – Roll ends = 8.625″
C – O.D. of the cone = 7.625″
D – I.D. of the surround = 7.125″
I took your suggestion to temporarily affix the surround to the woofer disc and basket. My conclusion is that the outward facing roll will not come in contct with woofer disc edges as it operates even if driven hard.
The act of handling/manipulating the new foam surrounds has created another doubt in my mind. I am wondering now if they may not be compliant enough? Too stiff in other words.
This is pure conjecture on my part as the original surrounds had pretty much become dust. So I never had the opportunity to feel them and/or assess their compliance. Consequently, since these SBX500 speakers only recently came into my possession, I have never heard them when in peak operating condition.
I sourced the surrounds from a company called Midwest Speaker Repair. They offer six different 10" foam surrounds, two of which have flat attachents, I chose the one with dimensions that seemingly fulfilled my dimension requirements to a tee.
One of the other 10" surrrounds Midwest Speaker Repair offer is described as high compliance - thinner material. I would have been tempted by that option but it's inner edge is angled, not flat and I needed flat.
The description below is that used by Midwest Speaker Repair on their website to describe the refoam kit I purchased. It is also catagorized by Midwst Speaker Repair as a "Standard Refoam Kit".
So I must soldier on with the surrounds I have and sincerely hope they are not so stiff they turn these woofers into midranges.
10 inch Refoam Kit (F10-10)
https://www.midwestspeakerrepair.com/product/mw-audio-mt-4115-1-inch-dome-tweeter/$22.95–$24.95
FLAT attachment to cone
A – O.D. of the surround = 9.75″
B – Roll ends = 8.625″
C – O.D. of the cone = 7.625″
D – I.D. of the surround = 7.125″