i have resently constructed a sub enclosure.....
my question is how thick of dampining should i line the inside walls with?
1/4 inch 1/2 inch 1inch 2inchs.....please help i am not relly sure.....
thanks,🙂
my question is how thick of dampining should i line the inside walls with?
1/4 inch 1/2 inch 1inch 2inchs.....please help i am not relly sure.....
thanks,🙂
Check out this link.
http://integra.cyberglobe.net/caraudio/resources/fiberfill/
If it were me, I'd start with about 2 lb's in a box your size and go from there.
http://integra.cyberglobe.net/caraudio/resources/fiberfill/
If it were me, I'd start with about 2 lb's in a box your size and go from there.
It depends on:1)working principle of the sub(sealed,ported,band pass...)
2)specific driver and enclosure alignment(Q factor)
3)damping material(glass fibres,natural wool,polyester fibres,cotton...)
4)amplifier characteristic(damping factor and subjective "something" factor that seems still not found in amp spec`s)
5)Your taste.
As a general rule: do not overdamp ported designs.Sealed designes often reqiure more stuffening with more damp effective materials such as glass and natural wool.In sealed designs I`m always using glass since it have best absorption of low frequency compared to anything,but it represent certain health hazard and it`s no longer used for ported boxes. Band pass and transmission line damping is more critical.Let your ears be final judge.
Best regards,
2)specific driver and enclosure alignment(Q factor)
3)damping material(glass fibres,natural wool,polyester fibres,cotton...)
4)amplifier characteristic(damping factor and subjective "something" factor that seems still not found in amp spec`s)
5)Your taste.
As a general rule: do not overdamp ported designs.Sealed designes often reqiure more stuffening with more damp effective materials such as glass and natural wool.In sealed designs I`m always using glass since it have best absorption of low frequency compared to anything,but it represent certain health hazard and it`s no longer used for ported boxes. Band pass and transmission line damping is more critical.Let your ears be final judge.
Best regards,
Dustin Haug:
An interesting link on fiber-fill. Only problem is, David Weems has written that the increase in low frequency extension comes at the expense of overall system sensitivity.
If that is true, than I imagine what is happening is this. Suppose we have a box that is 90 dB @ 1M/1W through the midrange and down through the midbass, then is 6 dB down at 42 Hz. We add fiber-fill. We now are only 3 dB down at 42 Hz-quite a pickup. However, our speaker is only 87 dB @ 1M/1W through the midrange and midbass.
If this is the case, we haven't picked up anything. We have simply knocked down the midrange and midbass sensitivity, so the bottom end sounds larger, without really increasing the bass output.
Weems did not say this is what happens specifically. But he did say that overall system sensitivity goes down when you add fiberfill as the bass extension goes up, and I just extrapolated from there.
Tom Nousaine's article did not mention overall sensitivity of the system. However, Weems did.
Now, if the system adds 3 dB extra at the low end while subtracting only 1 dB throughout the rest of the midbass and midrange, that would be a different story. Until we have an article that deals with specific tests, or someone conducts specific tests themselves, we won't know. Until then, I think it is sensible to assume that any 3 dB in extra bass is counterbalanced by a 3 dB decrease in midrange/midbass sensitivity, for a total of zero increase in bass output.
My question is, have you tried this, or do you have an article that deals with this issue specifically?
An interesting link on fiber-fill. Only problem is, David Weems has written that the increase in low frequency extension comes at the expense of overall system sensitivity.
If that is true, than I imagine what is happening is this. Suppose we have a box that is 90 dB @ 1M/1W through the midrange and down through the midbass, then is 6 dB down at 42 Hz. We add fiber-fill. We now are only 3 dB down at 42 Hz-quite a pickup. However, our speaker is only 87 dB @ 1M/1W through the midrange and midbass.
If this is the case, we haven't picked up anything. We have simply knocked down the midrange and midbass sensitivity, so the bottom end sounds larger, without really increasing the bass output.
Weems did not say this is what happens specifically. But he did say that overall system sensitivity goes down when you add fiberfill as the bass extension goes up, and I just extrapolated from there.
Tom Nousaine's article did not mention overall sensitivity of the system. However, Weems did.
Now, if the system adds 3 dB extra at the low end while subtracting only 1 dB throughout the rest of the midbass and midrange, that would be a different story. Until we have an article that deals with specific tests, or someone conducts specific tests themselves, we won't know. Until then, I think it is sensible to assume that any 3 dB in extra bass is counterbalanced by a 3 dB decrease in midrange/midbass sensitivity, for a total of zero increase in bass output.
My question is, have you tried this, or do you have an article that deals with this issue specifically?
Using fill or lining in a reflex subwoofer cabinet is not desirable IMO. Too bad it's required in midbass applications.
The article did not provide enough information on what actually happens when fill is added to a reflex.
In a reflex enclosure, the box volume itself must remain a resonator to excite the 2nd resonator(port/radiator), by adding fill you do infact lower H(Fs/Fsb), but in doing so you lower Qb(resonance efficiency of box), thus while lowering effective low frequency extension, you have also proportionately lowered low frequency efficiency. It is suprising that the artilce leaves this 'little' fact out.
I see no reason to use fill in a subwoofer, becuase of this fact. In midbass applications, an enclosure shape with minimal standing wave gain should be used so that minmal amounts of lining can be used, that is if you wish to retain maximum bass efficiency.
KelticWizard: Weems was referring to overall sensitivity of the bass alignment, as this is totally seperate and not related to the efficiency of the mms/bl behaviour of the speaker.
-Chris
The article did not provide enough information on what actually happens when fill is added to a reflex.
In a reflex enclosure, the box volume itself must remain a resonator to excite the 2nd resonator(port/radiator), by adding fill you do infact lower H(Fs/Fsb), but in doing so you lower Qb(resonance efficiency of box), thus while lowering effective low frequency extension, you have also proportionately lowered low frequency efficiency. It is suprising that the artilce leaves this 'little' fact out.
I see no reason to use fill in a subwoofer, becuase of this fact. In midbass applications, an enclosure shape with minimal standing wave gain should be used so that minmal amounts of lining can be used, that is if you wish to retain maximum bass efficiency.
KelticWizard: Weems was referring to overall sensitivity of the bass alignment, as this is totally seperate and not related to the efficiency of the mms/bl behaviour of the speaker.
-Chris
Tom`s article is interesting but his conclusions are somewhat constrained IMHO.He took for granted dacron-polyester fibre is best damp material outhere,and that`s true considering anti-moth,price and ecological qualities.Every sound absorbing fibre material has different absorbing coefficient on specific audio spectrum,and polyester don`t shine on any part of it,comparing to glass fibre,cotton,natural wool,polyurethane soft foam ,in same thickness of course.It`s good on mid`s and high`s,but have poor absorption on bass.For instance,cotton fibres are very good on upper bass,on mid`s,and excellent on upper mid`s and high`s.Best absorption on bass is with glass fibres,and it will give the greatest "pretending to be bigger box then actually"effect.For the same reason polyester is desirable in ported designs:doesn`t damage much Q alignment,and do the job on mid`s and upper.
If you ever put your ear on bass reflex port you will hear why you need lining.Do not think that terrible noise consisting of resonances and standing waves couldn`t find their way out of box together with original signal.
Further seems logical to me that when you add fill and loose some efficiency on mids,only thing that is lost is the same noise,not wanted in the first place.This can be checked comparing driver response in well-damped sealed box vs.infinite baffle fitted driver, but I didn`t try this.
If you ever put your ear on bass reflex port you will hear why you need lining.Do not think that terrible noise consisting of resonances and standing waves couldn`t find their way out of box together with original signal.
Further seems logical to me that when you add fill and loose some efficiency on mids,only thing that is lost is the same noise,not wanted in the first place.This can be checked comparing driver response in well-damped sealed box vs.infinite baffle fitted driver, but I didn`t try this.
Dex-Rex:
While the stuffing has little to no effect on long wavelength frequencies as far as direct acoustic absorbtion, this is not relevant to the bass alignment. Aside from standing waves and other non-bass related noises in a normal enclosure, the stuffing/lining is abosorbing energy indirectly, this means that the pressurization oscillation(resonance) characteristics of the box is changed, to the friction caused by the stuffing. This is why fibergalss or acoustastuff, with a greater effective path of resistance is more effective than simple polyfill at increasing 'apparent' volume size of the enclosure. But, by this same reason, you DECREASE efficiency of the box as a resonator! This causes a poorer coupling to the vent or radiator, decreasing effective output levels. You should remember that the port/vent is primarily responsible for SPL at and around port tuning.
Use of stuffing and/or lining in a ported box should done conservatively, and NONE should be used in subwoofer applications. This means that midrange-bass enclosure shapes that reduce their inherent standing waves efficiently in the first place due to non paralel walls will be able to achieve higher amplitudes around tuning of the box than the same volume and port tuning with significanty higher amounts of stuffing.
-Chris
While the stuffing has little to no effect on long wavelength frequencies as far as direct acoustic absorbtion, this is not relevant to the bass alignment. Aside from standing waves and other non-bass related noises in a normal enclosure, the stuffing/lining is abosorbing energy indirectly, this means that the pressurization oscillation(resonance) characteristics of the box is changed, to the friction caused by the stuffing. This is why fibergalss or acoustastuff, with a greater effective path of resistance is more effective than simple polyfill at increasing 'apparent' volume size of the enclosure. But, by this same reason, you DECREASE efficiency of the box as a resonator! This causes a poorer coupling to the vent or radiator, decreasing effective output levels. You should remember that the port/vent is primarily responsible for SPL at and around port tuning.
Use of stuffing and/or lining in a ported box should done conservatively, and NONE should be used in subwoofer applications. This means that midrange-bass enclosure shapes that reduce their inherent standing waves efficiently in the first place due to non paralel walls will be able to achieve higher amplitudes around tuning of the box than the same volume and port tuning with significanty higher amounts of stuffing.
-Chris
CHRIS8,
Considering pure sub,ported/vented enclosures I agree 100%.But referring to closed mid/bas enclosures I think that good stuffing is unavoidable and very beneficial.You do loose some efficency on mids,but isn`t it the "bad thing" go away?
In sealed box design the mid/bass driver cone excursion is not affected by the dampening in the mids(and upper),so we get same amplitude on the cone but lower output.I wonder what`s the energy we lost?I suspect that is unwanted sound consisting of resonances,reflections and standing waves.Stuffed closed box on frequencies from low mids to high`s acts as much larger enclosure because of the fact that signal front wave sent into box is introduced with fill,where it`s attenuated AND time-delayed just like if the box sides were much,much further from driver,closing to infinite baffle response.That`s the way I see it.
Check this out: www.t-linespeakers.org/projects/tlB/appendix/index.html
Greet`s
Considering pure sub,ported/vented enclosures I agree 100%.But referring to closed mid/bas enclosures I think that good stuffing is unavoidable and very beneficial.You do loose some efficency on mids,but isn`t it the "bad thing" go away?
In sealed box design the mid/bass driver cone excursion is not affected by the dampening in the mids(and upper),so we get same amplitude on the cone but lower output.I wonder what`s the energy we lost?I suspect that is unwanted sound consisting of resonances,reflections and standing waves.Stuffed closed box on frequencies from low mids to high`s acts as much larger enclosure because of the fact that signal front wave sent into box is introduced with fill,where it`s attenuated AND time-delayed just like if the box sides were much,much further from driver,closing to infinite baffle response.That`s the way I see it.
Check this out: www.t-linespeakers.org/projects/tlB/appendix/index.html
Greet`s
I am in agreement. Perhaps since you seem to be new to English language, your phrasing was a bit confusing, and you did not quite understand me either.
My point is that if an internal shape for a midbass application is chosen that minimizes standing waves, then less stuffing/lining can be used, and then you only need to worry primarly about the midrange reflections that will leave the port opening.
Have a nice day.
-Chris
My point is that if an internal shape for a midbass application is chosen that minimizes standing waves, then less stuffing/lining can be used, and then you only need to worry primarly about the midrange reflections that will leave the port opening.
Have a nice day.
-Chris
For a ported box use convoluted acustic foam. 1.5" or 2.5" depending on box size. That sould suck up any motor noise made from driver rear. Sealed or PR can use Miraflex non itching fiberglass insulation sold in better hardware/home improvement stores. I think at the rate of 1/2lb per cu ft Vb.
Different damping materials
Does anyone know of the pros/cons of different damping materials?
I am especially interested in any experiences of rockwool, as I am thinking of using that in my new sub (sealed).
I have used fiber glass before with OK results. What about natural washed wool?
Thanks
/Marcus
Does anyone know of the pros/cons of different damping materials?
I am especially interested in any experiences of rockwool, as I am thinking of using that in my new sub (sealed).
I have used fiber glass before with OK results. What about natural washed wool?
Thanks
/Marcus
Miraflex is hard to beat. Rock wool that I've worked with in the past came from recycled slag, was dark grey and was the itchiest stuff I ever had the displesure of working with. Miraflex is almost free of irritation OTOH.
I'm trying to build home speakers for my first time. I know the volume and port size. How does adding stuffing affect the volume of my box? Do the woofers think the box is bigger, so it throws off the alignment of my port and a different size port would be apropriate? I'm building a 2-way system, with 1" tweeter and 2 - 8" mids per speaker (I'm not sure what they're crossed over at yet), how much stuffing and what kind should I use? For absorving mids I heard convoluted acoustic foam and polyester fill or polyfil I guess it's called is good for this thread. If the stuffing makes my woofers think my box is bigger, should I make my box smaller? If so by how much?
Off the top of my head I can't tell you. Do a Google search on sealed speaker boxes, closed speaker boxes, DIY speakers, etc. You'll find what you're looking for.
In a nutshell, here's the deal regarding sound absorbing material in speaker boxes for different situations with a built in safety margin for variations in crossover slope and frequency:
Subwoofers in sealed boxes:
Line the walls with cotton batting.
Fill it up loosly with fiberglass.
Insure box size maintains desired Q.
Subwoofers in vented boxes:
Line the walls with cotton batting.
Do not stuff.
2 Way fullrange or satellite sealed boxes:
Line the walls with cotton batting.
Fill it up loosly with fiberglass.
Insure box size maintains desired Q.
2 Way fullrange or satellite vented boxes:
Line the walls with cotton batting.
Do not stuff.
With subs, either vented or sealed, you may not need the cotton batting on the walls if the crossover is steep. But it won't hurt.
Simplistically, the purpose of the cotton batting is to absorb the back wave at higher frequencies so it doesn't wind up going through the cone and interferring with the front wave. This is particularly important with 2 way speakers. Cotton batting is available in various thicknesses, is cheap and is too often ignored. No real need to get involved with foam, wool or anything else.
I've built hundred of speaker systems using these simple rules and they have never let me down.
As mentioned, transmission line are a different story.
Hey, CHRIS8, no hostility. 😀
Subwoofers in sealed boxes:
Line the walls with cotton batting.
Fill it up loosly with fiberglass.
Insure box size maintains desired Q.
Subwoofers in vented boxes:
Line the walls with cotton batting.
Do not stuff.
2 Way fullrange or satellite sealed boxes:
Line the walls with cotton batting.
Fill it up loosly with fiberglass.
Insure box size maintains desired Q.
2 Way fullrange or satellite vented boxes:
Line the walls with cotton batting.
Do not stuff.
With subs, either vented or sealed, you may not need the cotton batting on the walls if the crossover is steep. But it won't hurt.
Simplistically, the purpose of the cotton batting is to absorb the back wave at higher frequencies so it doesn't wind up going through the cone and interferring with the front wave. This is particularly important with 2 way speakers. Cotton batting is available in various thicknesses, is cheap and is too often ignored. No real need to get involved with foam, wool or anything else.
I've built hundred of speaker systems using these simple rules and they have never let me down.
As mentioned, transmission line are a different story.
Hey, CHRIS8, no hostility. 😀
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