I'm looking too extend the lowend on my sub. It hasn't been built yet, as I keep learning new stuff every week (if not on a daily basis) from you guys. This keeps me changing (improving) my cabinet specs. What i'd like to know now, are the effects of adding mass to the cone. From WinISD, it appears to lower Fs and SPL, and raises the Qtc so you need a larger volume. Sometimes much more volume to keep the same Qtc. Also it seems to degrade transience at very low frequencies a little. I was considering adding 40-50grams to my cone, and about 1cuft. to my cabinet to maintain the same Qtc. Adding 40 grams gives me +3.79db @ 30hz, and 4.63db @ 20hz. Thanks as always guys.
Fs 25.5hz
Qms 4.57
Qes .28
Qts .26
Vas 4.7cuft
Re 4.16ohm
Fs 25.5hz
Qms 4.57
Qes .28
Qts .26
Vas 4.7cuft
Re 4.16ohm
adding mass isnt a great idea if you ask me.
You lose sensitivity only to lower Fs and increase Qts which means nothing really in terms of max output, but changes frequency response.
If you want your sub to go low, you need excursion plain and simple. Lowering the Fs trades higher frequency efficiency for a tiny bit of low frequency extension, but if your driver bottoms out at 30hz with no mass on the cone it will be just as loud when it bottoms out with mass on the cone!
You lose sensitivity only to lower Fs and increase Qts which means nothing really in terms of max output, but changes frequency response.
If you want your sub to go low, you need excursion plain and simple. Lowering the Fs trades higher frequency efficiency for a tiny bit of low frequency extension, but if your driver bottoms out at 30hz with no mass on the cone it will be just as loud when it bottoms out with mass on the cone!
If you don't plan on ever driving the woofer hard enough to bottom it out, bottoming out is not so much of a problem. If you wanted the sounds coming out of it to be lower frequencies than currently possible, the high Fs *is* so much of a problem.
If you don't mind the efficiency hit, and you can design around the Q changing, and you don't plan to overpower the thing anyhow, I say go for it.
Just don't use a magnetic chunk of stuff right near the center of the cone on a very small woofer... excursion reduction through magnetic tug-o-war! (free woofers lead to experimentation)
If you don't mind the efficiency hit, and you can design around the Q changing, and you don't plan to overpower the thing anyhow, I say go for it.
Just don't use a magnetic chunk of stuff right near the center of the cone on a very small woofer... excursion reduction through magnetic tug-o-war! (free woofers lead to experimentation)
I really dont plan on shaking the walls. I'm in an apartment with whiney nieghbors. I was doing research and found that nickels (according to usmint.gov) are exactly 5grams each. If I do decide to try it out, i'll use nickels but i'm not sure what adhesive to use. Maybe good old polyurethane glue. My driver has a 13mm xmax, not monsterous, but a healthy amount of travel.
GuyPanico said:
Interesting that some of the others just retell you what you have already stated. You seem to have a fair handle on it, thanks to some freeware. My suggestion is to experiment - build the box halfway between the two extremes and try it with and without the added mass.... You can attach nickels temporarily and for low volumes with double stick tape - if you start rocking out, don't be surprised if the nickels go flying
For permanent attachment : www.thistothat.comI wouldn't add mass to a speaker I was going to mount so it fired up or down...
SY, thanks for clearing that up.... I didnt mention the thermal limited power region because the goal of adding mass seems to be increasing efficiency at very low frequencys. At low frequencys the speakers are often excursion limited. But also there at the low frequencys volume displacement is the most important thing. Adding mass wont get you very far.
So why would you want to add mass again?
So why would you want to add mass again?
Hi,
I hammered some lead to form a pair of lead foil half moons and used double sided tape to attach near the centre of the cone (210mm). I knew it would reduce efficiency and wondered about upsetting the balance of an existing speaker (KLS3gold - 3way).
It seemed to pull up the mid bass and have no effect on upper bass (a big surprise) but the biggest shock was how deep the speakers seemed to go in the low bass.
I deemed the experiment a great success except that at high volume (no distortion audible) the lead would occasionally pop off and land on the floor about 2 feet away. More sticky tape I think or hammer the lead foil even thinner.
I also tried adding an inline resistor (a short length of nichrome wire after the xover)to the bass speaker that had a mismatched Qts and this also lowered the bass cutoff point but to a lesser extent.
I hammered some lead to form a pair of lead foil half moons and used double sided tape to attach near the centre of the cone (210mm). I knew it would reduce efficiency and wondered about upsetting the balance of an existing speaker (KLS3gold - 3way).
It seemed to pull up the mid bass and have no effect on upper bass (a big surprise) but the biggest shock was how deep the speakers seemed to go in the low bass.
I deemed the experiment a great success except that at high volume (no distortion audible) the lead would occasionally pop off and land on the floor about 2 feet away. More sticky tape I think or hammer the lead foil even thinner.
I also tried adding an inline resistor (a short length of nichrome wire after the xover)to the bass speaker that had a mismatched Qts and this also lowered the bass cutoff point but to a lesser extent.
Added MAss method
A ring of plumbing solder is always good to use. Or if less mass is needed you can make segments of a ring. It can be glued to the termination on the cone between it and the dust cap.
Added mass is an old trick and it is still in use. I used to do work with a manufacturer that made drivers for velodyne. THey used a large mass load to lower the fs of a driver to get it into a in a smaller box. I'm surprised that no one mentioned tha yet. You will definitely loose efficiency but you can get better bass for a smaller enclosure. Power limiting is very important when you are trying to get away with this.
Come to think of it the Polk subs stuff have a very heavy cone to. Same idea. Added mass can be used as a plus when factored into the design. they used to do a compound driver system with a flow controled vent. Damn heavy drivers in that to. That was back around 96/97
MArk
A ring of plumbing solder is always good to use. Or if less mass is needed you can make segments of a ring. It can be glued to the termination on the cone between it and the dust cap.
Added mass is an old trick and it is still in use. I used to do work with a manufacturer that made drivers for velodyne. THey used a large mass load to lower the fs of a driver to get it into a in a smaller box. I'm surprised that no one mentioned tha yet. You will definitely loose efficiency but you can get better bass for a smaller enclosure. Power limiting is very important when you are trying to get away with this.
Come to think of it the Polk subs stuff have a very heavy cone to. Same idea. Added mass can be used as a plus when factored into the design. they used to do a compound driver system with a flow controled vent. Damn heavy drivers in that to. That was back around 96/97
MArk
Some might say, gasp, adding cone mass results in slower bass! Isnt that the arguement why smaller drivers have more articulate bass than larger ones? Or has voice coil inductance been the real problem? Perhaps it might even be a factor of high order distortions or efficiency gain from increased radiating area.
In an ideal driver wouldnt the cone be massless and without resonance? Since we must have mass and springiness, A looser suspension will provide lower resonance without consequences in the efficiency.
Has anyone compared side by side listening to a driver with and without mass? I seriously doubt anyone would prefer the massed driver unless the alignments were rediculously whack!
In an ideal driver wouldnt the cone be massless and without resonance? Since we must have mass and springiness, A looser suspension will provide lower resonance without consequences in the efficiency.
Has anyone compared side by side listening to a driver with and without mass? I seriously doubt anyone would prefer the massed driver unless the alignments were rediculously whack!
Hi
Big woofers tend to sound slow because being “big” they have large Voice coils, which have a lot of inductance. It is the Rdc and Le, which form the “low pass” filter in the mechanical system.
Adding mass to a woofer, assuming it is anchored to the VC securely, does not affect the “speed of response” at all.
The reason is that woofers are “acoustically small” and so operate on the slanted portion of the radiation impedance curve (for the radiator size vs. wl).
This means to have flat response, a “small” radiator must have a velocity that falls at the inverse of the slope of the radiation resistance (6 dB /Oct).
In a woofer, this is accomplished by the action of the driver’s series Rdc, coupled through the BL conversion in the motor, to the moving mass.
The moving mass looks like (electrically) a capacitor and that forms the R/C filter that has the roll off that makes the driver measure flat.
Adding more mass, does make the capacitance larger, lowering the frequency where the transition from Velocity to Acceleration response happens, but that is at the bottom end of the response. The added mass has no impact on the driver’s “speed” or high frequency cutoff.
I don’t know off hand but that driver in your Icon looks like one of Dan Wiggins drivers.
It is worth pointing out that his voice coil invention does allow for the construction of a much larger VC motor than normal for a given R/L corner (a very good thing)
His drivers, because of his gap thing, would be the exceptional case where you have a large displacement, a strong motor AND low inductance.
Adding something you can remove later makes playing with parameters fun but what also makes sense, given the availability of modeling programs, would be to model the system and then, in the computer, add some mass. There have been HiFi speakers I have seen where mass was added to the cone, right from the factory so it is worth seeing what can be done.
Happy bass
Tom Danley
Big woofers tend to sound slow because being “big” they have large Voice coils, which have a lot of inductance. It is the Rdc and Le, which form the “low pass” filter in the mechanical system.
Adding mass to a woofer, assuming it is anchored to the VC securely, does not affect the “speed of response” at all.
The reason is that woofers are “acoustically small” and so operate on the slanted portion of the radiation impedance curve (for the radiator size vs. wl).
This means to have flat response, a “small” radiator must have a velocity that falls at the inverse of the slope of the radiation resistance (6 dB /Oct).
In a woofer, this is accomplished by the action of the driver’s series Rdc, coupled through the BL conversion in the motor, to the moving mass.
The moving mass looks like (electrically) a capacitor and that forms the R/C filter that has the roll off that makes the driver measure flat.
Adding more mass, does make the capacitance larger, lowering the frequency where the transition from Velocity to Acceleration response happens, but that is at the bottom end of the response. The added mass has no impact on the driver’s “speed” or high frequency cutoff.
I don’t know off hand but that driver in your Icon looks like one of Dan Wiggins drivers.
It is worth pointing out that his voice coil invention does allow for the construction of a much larger VC motor than normal for a given R/L corner (a very good thing)
His drivers, because of his gap thing, would be the exceptional case where you have a large displacement, a strong motor AND low inductance.
Adding something you can remove later makes playing with parameters fun but what also makes sense, given the availability of modeling programs, would be to model the system and then, in the computer, add some mass. There have been HiFi speakers I have seen where mass was added to the cone, right from the factory so it is worth seeing what can be done.
Happy bass
Tom Danley
Yes, that is an XBL^2 driver, Adire's Tumult to be exact.
Well I'm opposed to adding cone mass myself just because it seems to have more disadvantages than advantages to me.
It is true that inductance limits high frequency bandwidth, not mass, but adding the mass will decrease your efficiency at higher frequencys and lower maximum SPL(in the thermal limited power region). The efficiency is usually gained in the excursion limited power region, but maximum SPL will not be increased here.
In a rare case it might help though
Well I'm opposed to adding cone mass myself just because it seems to have more disadvantages than advantages to me.
It is true that inductance limits high frequency bandwidth, not mass, but adding the mass will decrease your efficiency at higher frequencys and lower maximum SPL(in the thermal limited power region). The efficiency is usually gained in the excursion limited power region, but maximum SPL will not be increased here.
In a rare case it might help though
BassAwdyO, you seem to be missing the thread starter's point entirely. You keep mentioning the extremes of excursion and power when the intention is never to approach these. What he wants to do is lower the frequency extension capability of his sub at *less than maximum* output levels, without caring about the loss of efficiency. What he wants to do will likely work like a champ, for his situation under those conditions.
As far as adding mass goes, don't think that it's a DIY-only thing. As mentioned "some" hifi speaker companies do it as a matter of course. If you dig deep enough on This Very Website, you will find that Adire adds mass to their drivers. One customer said there was a little disc under his dustcap that had come loose and was rattling. Dan Wiggins himself responded that Adire put that extra mass in there. Why?
To
Lower
Fs.
Let's not get started on "slow bass", please!
As far as adding mass goes, don't think that it's a DIY-only thing. As mentioned "some" hifi speaker companies do it as a matter of course. If you dig deep enough on This Very Website, you will find that Adire adds mass to their drivers. One customer said there was a little disc under his dustcap that had come loose and was rattling. Dan Wiggins himself responded that Adire put that extra mass in there. Why?
To
Lower
Fs.
Let's not get started on "slow bass", please!
Here's a little reminder (perhaps some will have never heard)
13mm of Xmax will get you a LOT of bass, even sub-bass. When I was a kid looking through the Parts Express catalog, big excursion was 5mm, and quite often you would really spend some $$ to get even that. It doesn't take a lot of cone motion (or power) to get some serious bass. Not everyone has an unconcious goal of being deaf by age 55.
Besides all of which it's all still theory. GuyPanico, build a box with whatever compromises you find necessary, with whatever mass you feel like adding. Make sure it's well-secured to the cone and preferably well distributed as well. Then report back what you find. My prediction: it will get as loud as you like and as low as you like and sound good doing it.
Good luck and happy building!
P.S.: don't forget the photographs!
13mm of Xmax will get you a LOT of bass, even sub-bass. When I was a kid looking through the Parts Express catalog, big excursion was 5mm, and quite often you would really spend some $$ to get even that. It doesn't take a lot of cone motion (or power) to get some serious bass. Not everyone has an unconcious goal of being deaf by age 55.
Besides all of which it's all still theory. GuyPanico, build a box with whatever compromises you find necessary, with whatever mass you feel like adding. Make sure it's well-secured to the cone and preferably well distributed as well. Then report back what you find. My prediction: it will get as loud as you like and as low as you like and sound good doing it.
Good luck and happy building!
P.S.: don't forget the photographs!
BassAwdyO said:
I bet your neighbours don't think so!
Guy, give it a try, but be aware you might need to play with your crossover to get everything back in balance. I second the suggestion of plumbing solder, though coins do work as well. Hot melt glue is good for attachment, it's strong, but can be removed if required, (unless you have paper cones, in which case just about any adhesive won't come off without damage).
Could this be applied as a rule of thumb and is there a way around this? Since almost all otherwise good PA woofers have big voicecoils (4" and up).
It's yet another explanation I read in the past few days and it's an answer i really would like to know, since the slow sound bothers me since the day I've got a system (I don't have unlimited money to spend, to find out either
)Mvg Johan
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