[kryptonitewhite]

Hey all, a newbi to the forum for the most part...I'm playing with the idea of doing dual 18's at 8Hz because bottom c just seems interesting. I will probably actually do 7Hz for tolerances and losses. I'd like to build the enclosure to those parameters ignoring that I will probably stuff it heavily, "lowering" the actual outcome. I don't want to plot it in WinISD with it set to heavy stuffing and just know that it will actually come out lower or pretty close to it.

How much will heavily stuffing the enclosure really affect the overall performance?

 

[Mike P.]

Quoted from another thread:

Every pound of polyfill increases apparent volume of an enclosure by 0.1 cubic feet for a maximum increase of approximately 10% of total volume.

 

[thxgoon]

Bear in mind that stuffing only has this effect on a sealed enclosure. Is this what you were planning?

From my understanding too much fill in a ported design decreases efficiency (though I don't know exactly why).

 

[kryptonitewhite]

Quoted from another thread:

Every pound of polyfill increases apparent volume of an enclosure by 0.1 cubic feet for a maximum increase of approximately 10% of total volume.

thanks Mike! So I'm wondering, since I threw my Bass Box Pro 6 and WinISD programs out like a dummi, If I model any driver (after redownloading WinISD) in say 20 cubes without stuffing and model another until it has the same Fb or F3, for the sake of argument say it ends up being 15 cubes.... will everything be the same? Same FR curve, same excursion at given frequency per watt, same impedance curve?

I'm guessing no, impedence will be completely different, group delay, so on....


I really want to get the enclosure as close to 7Hz as possible non-stuffed....because I don't want to "fake" however far I come short. make sense? When i blast an 8Hz tone...I dont want to be unloading because I "faked it" rather then being right at port resonance and having seriouse gain, low excursion, high power handling...so on.

 

[kryptonitewhite]

Bear in mind that stuffing only has this effect on a sealed enclosure. Is this what you were planning?

From my understanding too much fill in a ported design decreases efficiency (though I don't know exactly why).

I think you are correct on the efficiency part...and I'm willing to sacrifice a little to gain some SQ from damping out of the deal if it's not too much. But thats yet another reason why i want to get as close to it as I can and don't want to cheat

 

[thxgoon]

If I model any driver (after redownloading WinISD) in say 20 cubes without stuffing and model another until it has the same Fb or F3, for the sake of argument say it ends up being 15 cubes.... will everything be the same? Same FR curve, same excursion at given frequency per watt, same impedance curve?

I'm a little confused as to what you're asking. Are you saying that you want to model at 20 cubes unstuffed, then go as small as you can with stuffing for the same specs? If you're using a sealed design, then yes. If you're using a vented design then no.

 

[kryptonitewhite]

I lost my bass box pro 6, i'm not as familiar with winisd. if i recall correctly, under vented design you could do stuffing: none, minimal, normal, and heavy.

I thought stuffing a vented box had similar or the same results as a sealed box. but i guess not, so that made this very easy!

8Hz is rediculous anyway, I think I may go back up to 16Hz or 20Hz...which is still much much lower than I need for my application

 

[Bill Fitzmaurice]

Quoted from another thread:

Every pound of polyfill increases apparent volume of an enclosure by 0.1 cubic feet for a maximum increase of approximately 10% of total volume.

The theory that stuffing increases the apparant volume of the box is a misconception. Stuffing lowers the box Q, which can tame a resonant peak in a sealed cab that's too small, giving a flatter response. It does not significantly lower Fb or increase sensitivity as a larger box will.
Most box programs lack the ability to model the effect of stuffing density and thickness. McBean's Horn Resp does have this ability. It shows the effect of stuffing on response, and the basis for that effect, which is system impedance, with both sealed and vented alignments.

 

[kryptonitewhite]

The theory that stuffing increases the apparant volume of the box is a misconception. Stuffing lowers the box Q, which can tame a resonant peak in a sealed cab that's too small, giving a flatter response. It does not significantly lower Fb or increase sensitivity as a larger box will.
Most box programs lack the ability to model the effect of stuffing density and thickness. McBean's Horn Resp does have this ability. It shows the effect of stuffing on response, and the basis for that effect, which is system impedance, with both sealed and vented alignments.

there we have it!

I think I will skip the stuffing, and I may just go large sealed as well. Thank you for the clarity! You can't fake it...thats what I wanted to know

 

[avaserfi]

The theory that stuffing increases the apparant volume of the box is a misconception. Stuffing lowers the box Q, which can tame a resonant peak in a sealed cab that's too small, giving a flatter response. It does not significantly lower Fb or increase sensitivity as a larger box will.

This lowering of a systems Q is similar in effect to increasing cabinet size in sealed systems with regard to frequency response. This seems to be the primary concern to most.

If the goal of the stuffing is removing of resonances polyfill is a terrible choice. Rather, a dense acoustically absorbent material such as OC705 or 8lb mineral board would be far superior. Do note that excessive use of such a material will reduce the ability of the box to act as a spring air-mass system. Meaning it will no longer be able to resonate properly.

 

[Bill Fitzmaurice]

This lowering of a systems Q is similar in effect to increasing cabinet size in sealed systems with regard to frequency response. This seems to be the primary concern to most.
.

It should be, but I'd guesstimmate that 95% of the posts I see in various places the poster plans on using stuffing to make the box smaller than it should be, on the mistaken assumption that in so doing the result will be the same as with a larger box in all regards, including sensitivity and F3. Vague and imprecise comments on the effect of stuffing reinforce that notion, and unfortunately many of those comments come from sources who should know better.

 

[kryptonitewhite]

Anyone know the low tone in Bass I Love You and Toccata in B? I've seen it posted by people using spectrum analyzers but I don't believe they are correct with low frequencies.

 

[Ricci]

Toccata is probably 16hz and "Bass I love you" I'm not sure about but I think it is even lower. I'll play that track and give you a good guesstimation.

 

[kryptonitewhite]

Toccata is probably 16hz and "Bass I love you" I'm not sure about but I think it is even lower. I'll play that track and give you a good guesstimation.

kick , i'd trust an ear using sign waves to compare more than those free analyzers...ive played sine waves on them and they were way off.

are those 18" 06' XXX's in your sig??? That's my dream right there!

nevermind...10's or 12's? was a quick glance...no time at work

 

[Ricci]

Actually you were right the first time Jordan those are 18's (5th one is on the way:help. The "little" driver in the middle is a Klipsch 12" driver:whistling:. That's right. The little driver that looks like a 5" mid is a regular size home audio 12". Look again.

 

[kryptonitewhite]

those are some beautiful pieces of equipment you have there! I'd like some speaker of them if u have some!

I posted this same topic on 1 other forum, they got a lot of my pics...I'll link ya'll

http://www.avsforum.com/avs-vb/showthread.php?t=1074047

 

[Bill Fitzmaurice]

kick , i'd trust an ear using sign waves to compare more than those free analyzers...ive played sine waves on them and they were way off.

Next time you measure see what registers way down low with the system turned off. If you have a highway within a few miles of your house you can measure appreciable levels below 30 Hz that's ground conducted traffic noise. Home heating furnaces have also been the source of low frequencies that made many a builder ecstatic over how well his system seemed to be working, until he turned the system off and found he was still reading 70dB at 20 Hz while not hearing a thing.

 

[kryptonitewhite]

I meant PC analyzers that you can play CD's on your computer and "localize" the frequency range. I wish i had an RTA! I have access to oscilloscopes and RTA's at work though....someday

 

[NEO Dan]

See this at the top of the page, click on it

This is the home of REW, a really great tool for measuring, it's accurate and FREE BTW:T

*****
Bill,
now that I think about it why is it you still draw up your curves instead of using REW?

 

[kryptonitewhite]

See this at the top of the page, click on it

This is the home of REW, a really great tool for measuring, it's accurate and FREE BTW:T

*****
Bill,
now that I think about it why is it you still draw up your curves instead of using REW?

Thanks Dan! Now I have REW and I downloaded the 3 test tone cd creators, as I threw all of my CDs out a while back.