Semi-theoretical question.
I have some cheap 8" woofers here I bought at clearance and on a whim a couple of decades ago. Never got around to using them. While clearing up some stuff yesterday I noticed that the flat dust cap was coming off the face of the polycones
I don't need any more woofers but I do need a new party speaker set and I was wondering if; as these are a pretty bright woofer with thin bass; I could improve the midrange performance by gluing on a large dome dust cover and if so what size and type would work best with a 220mm driver
For the Australians on the forum I bought these when DickSmith was purchased by Woolworths and I paid about $25- each for these and they were never worth the original $60- sticker price despite the big magnets and large voice coils.
Party speakers so loud is usually more important than clarity etc
I have some cheap 8" woofers here I bought at clearance and on a whim a couple of decades ago. Never got around to using them. While clearing up some stuff yesterday I noticed that the flat dust cap was coming off the face of the polycones
I don't need any more woofers but I do need a new party speaker set and I was wondering if; as these are a pretty bright woofer with thin bass; I could improve the midrange performance by gluing on a large dome dust cover and if so what size and type would work best with a 220mm driver
For the Australians on the forum I bought these when DickSmith was purchased by Woolworths and I paid about $25- each for these and they were never worth the original $60- sticker price despite the big magnets and large voice coils.
Party speakers so loud is usually more important than clarity etc
why don't you start by damping the rear wave of the woofer and dealing with near field reflections like the spider and the woofer basket struts. You might consider F11 Acoustical wool felt and some dynamat. That can be a big start for you and not mess up your drivers in any way.
I thought it might be an interesting experiment seeing as the drivers were so cheap. But yes I do still have plenty of self adhesive felt pads here
Also due to a tadpole poking holes in the dustcaps of big subwoofer drivers I had on the table I need to order a couple of 115mm dust caps and if I order more dust caps at the same time postage won't cost me any extra
Also due to a tadpole poking holes in the dustcaps of big subwoofer drivers I had on the table I need to order a couple of 115mm dust caps and if I order more dust caps at the same time postage won't cost me any extra
Most improvements can be had with flexible fabric glue from the apex of the surround down into the outer-edge of the cone by about an inch.
audio blog: Large Driver Cone Treatement
Other than that: filtration.
audio blog: Large Driver Cone Treatement
Other than that: filtration.
Interesting Scott as I thought that only worked with paper cones
There was a post and thread a while back that discussed a similar question and in that I got the impression that higher frequency sound radiation came from the dust cap eare and why I was contemplating adding on a domed paper dustcap to replace the flat ones that are coming off
There was a post and thread a while back that discussed a similar question and in that I got the impression that higher frequency sound radiation came from the dust cap eare and why I was contemplating adding on a domed paper dustcap to replace the flat ones that are coming off
-you actually get high freq.s from multiple locations on the cone ("bending"), particularly in respect to the frequency.
Each edge of the diaphragm's surface (outer near surround) and (inner near dust-cap junction) is usually louder, and particularly the outer edge because it's so poorly damped by comparison to the rigid center. Still, it's freq. dependent - it's a material and structural mode, but it's not like you listen to pure tones: so you are always listening to an aggregate (..with harmonics and intermodulation), and that outer edge is typically higher in amplitude than the average elsewhere on the surface. This doesn't show-up at distance. It "averages-out" as you move further from the source.
Poly bends MORE than hard paper.. so you tend to get a wider range/bandwidth with something beyond the average. On the other hand, those higher amplitude peaks and dips (in-phase and out-of-phase) won't be as prominent with Poly (with a reasonably well designed driver).
Note: you might be able to improve the center-edge (VC connection) of the diaphragm with a new dust-cap and glue - the weight of it in reaction to a lossy glue (like the flexible fabric glue already mentioned) can improve things. (..usually though you start first with surround damping: Klippel recommends this as a first mod. more likely to be beneficial.)
Each edge of the diaphragm's surface (outer near surround) and (inner near dust-cap junction) is usually louder, and particularly the outer edge because it's so poorly damped by comparison to the rigid center. Still, it's freq. dependent - it's a material and structural mode, but it's not like you listen to pure tones: so you are always listening to an aggregate (..with harmonics and intermodulation), and that outer edge is typically higher in amplitude than the average elsewhere on the surface. This doesn't show-up at distance. It "averages-out" as you move further from the source.
Poly bends MORE than hard paper.. so you tend to get a wider range/bandwidth with something beyond the average. On the other hand, those higher amplitude peaks and dips (in-phase and out-of-phase) won't be as prominent with Poly (with a reasonably well designed driver).
Note: you might be able to improve the center-edge (VC connection) of the diaphragm with a new dust-cap and glue - the weight of it in reaction to a lossy glue (like the flexible fabric glue already mentioned) can improve things. (..usually though you start first with surround damping: Klippel recommends this as a first mod. more likely to be beneficial.)
Last edited:
I spent a few days playing with gluing felt onto the cone of some cheap vifa drivers many years ago.
I tried all manner of shapes and places, I also tried measuring (very) mear to the cone to see where the peaks in the response were coming from.
I had some success - enough to keep me playing for a few days. But not enough that I left the felt in place long term. In some cases I WAS able to tame some peaks, but without investing lots of time and building fancy tools, I was not convinced I would get all the peaks I wanted smoothed out fixed.
To be clear - it is certainly not a case of "put on the magic felt and the response becomes great..." else the manufacturers would do this as a matter of course!
The surprising thing was that the impact on T/S and efficiency was a lot less than I was expecting.
Have a play!!!!
I tried all manner of shapes and places, I also tried measuring (very) mear to the cone to see where the peaks in the response were coming from.
I had some success - enough to keep me playing for a few days. But not enough that I left the felt in place long term. In some cases I WAS able to tame some peaks, but without investing lots of time and building fancy tools, I was not convinced I would get all the peaks I wanted smoothed out fixed.
To be clear - it is certainly not a case of "put on the magic felt and the response becomes great..." else the manufacturers would do this as a matter of course!
The surprising thing was that the impact on T/S and efficiency was a lot less than I was expecting.
Have a play!!!!
There was an Australian loudspeaker manufacturer who was placing strips of balsa wood on the back of the driver (18W8545 IIRC) to improve the performance. I can't remember if it was to help with break up or better mids or better bass. All I remember is the RRP of the speaker was quite expensive.
Maybe slice the cone like a SS Revelator or melt ribs into it like the SB NAC aluminium?
I've used Visaton LTS50 to help dampen cones but these were paper based and I would doubt it would stick to polypropylene.
Maybe slice the cone like a SS Revelator or melt ribs into it like the SB NAC aluminium?
I've used Visaton LTS50 to help dampen cones but these were paper based and I would doubt it would stick to polypropylene.
This should get dealt with when you design the crossover, and it's a common speaker trade-off in multi-way designs.
You trade off sensitivity for bass. That is, you tilt the output downwards, until you have the right bass to upper bass/mid balance, and since all we can do is loose, that results in lowered sensitivity.
Thanx Eric
Perhaps you missed the bit in the first post about using these little woofers as the actual mid-range driver, ie: taking advantage of their inherent brightness. If replacing the flat dust cap with a dome would help I could do that easily enough and if a particular dust cap construction would make a big difference to performance I was thinking I could use that type of dust cap.
Paper Vs Treated paper Vs Cloth Vs Aluminium domes as against the original flat plastic coated paper question.
Just for fun I have placed an order for a few paper dust caps via eBay
A dollar each from China with free postage because I needed some big ones for the sub drivers the tadpole thought it would be fun to punch down and then rip off. What is it with small children and dust caps anyway?
And on other parameters.
In general, it would take a drastic change such as new different cone or voice coil or both to change things much, otherwise changes are very small.
Personally I would use them as-is and design/choose crossover and accompanying elements for the best full system results.
You want better high mids? ... maybe picking a tweeter which can be crossed lower is the ticket, rather than trying to extend midrange speaker upwards but not changing anything important.
As a side note, a cone mounted dustcap does not do much, it needs to be glued to voice coil so it is being actually driven.
Well yes, as these are going to be party speakers high fidelity isn't part of the design equation so perhaps a small 2 or 3 inch full range would do the job.
Had a dozen of these floating around since forever too.
Had a dozen of these floating around since forever too.
Some of the answers seem to be assuming you want smoother response / better fidelity.
I'm not sure that's what you are after. In this context, does "improve" mean make the mids louder? Make the mids more extended? Both?
If so, I'd suggest imitating guitar / PA speakers which do this e.g. the JBL E140 looks like a typical bass speaker, but "is specially designed for the bass guitarist or keyboard player who wants a bright, sharply defined sound."
That's marketing speak for "loud mids" 🙂
The E140 used a very light, stiff dustcap, like this:
4" Aluminum Speaker Dust Cap, JBL, Others, DC-4A
Since the VC was 4" and the cap is 4", I assume the E140 had the cap glued directly to the VC.
Last edited:
I just ordered my first calibrated microphone so I guess this will be experiment and see what happens.
Getting a new garage/workshop over the next few months so I will finally get somewhere to work in other than the dirty and dusty back yard under the carport. Using measurement software will be a totally new experience for me and I expect a big steep learning curve and a few mistakes along the way.
Getting a new garage/workshop over the next few months so I will finally get somewhere to work in other than the dirty and dusty back yard under the carport. Using measurement software will be a totally new experience for me and I expect a big steep learning curve and a few mistakes along the way.
That´s what I meant.
In that case the rigid (because of dome shape) light (thin aluminum sheet) dustcap is straight glued to voice coil, it even has a small lip around for better contact and does not even touch the paper cone, if you look from a side you see a (very short but still there) "neck" bcause VC is oh so slightly longer than needed, on purpose of course.
In the Guitar one (K/D/E-130) it provides tons of strong piercing mid highs, think 5 to 7kHz , the reason of its typical sound.
I guess effect is somewhat attenuated in 140, not because of a dome fault but because of much heavier voice coil (edgewound copper instead of Aluminum) but still brighter than any of the competition.
Thanx for the clarification.
I had an E-130 once, but don't remember it well enough to be 100% sure where the cap was attached.
- Status
- Not open for further replies.