Realalistically....how much?

[Lewis Moon]

I'm lofting a sup (supplemental woofer) using the Dayton 8" Reference (RSS210HF-4) in a closed box....I'm going for speed and precision, not kidney stone break up...and the box comes up pretty small. I'm going to stuff it with Acousta-stuff and just want to get the zeitgeist on how much to reduce the volume of the overall box. I've seen between 15 and 40%...
I've plugged the numbers into WinISDPRO and come up with a curve I like at around 1492 Cubic Inches (Think Columbus) prior to stuffing...
What say the cognoscenti?

[MJL21193]

Hi,
The ideal closed, unstuffed box size for this driver is ~30 litres (learn metric for speaker talk ) giving a Qtc of ~.7.
Adding a heavy amount of stuffing can reduce the box size to ~18 litres - near enough to your 1492 square inches.

Efficiency is pretty low for this unit and power handling is not great. Looking at about 100db max at 50 watts before the driver runs out of linear excursion.

[Lewis Moon]

I'm a woodworker...we do everything in inches.
100 db would blow out the windows in our small living room.... Like I said, speed and precision rather than earthquake power. I like acoustic jazz and folk/vocal. Think Scott LaFaro or Sufjan Stevens....of course there's "Super Bon Bon" by Soul Coughing....
I'm using a 200w RMS Hafler/Fosgate amp. I figure that will be enough power for the sound levels the wife will permit.

[Lewis Moon]

A bit more to fill in the gaps as to the reasoning behind this design.
I have a set of vented monitors that head south pretty steeply somewhere just below 100hz. I would like to supplement the curve down to about the lower range of the bull fiddle (40 hz). I don't want bass that sounds like goose farts on a muggy day. I want to hear the striations in the horse hair on the bow as it is pulled across the strings of the bass. Musical in a word.

[MJL21193]

Originally posted by Lewis Moon
...I don't want bass that sounds like goose farts on a muggy day. I want to hear the striations in the horse hair on the bow as it is pulled across the strings of the bass. Musical in a word.

You get poor sound from poor design and execution, not from any particular alignment. Let's remember that many (most) of the higher quality / higher price speakers (and sub woofers) are vented.

IMO a properly designed vented design outstrips the equivalent closed design.

Originally posted by Lewis Moon
I'm a woodworker...we do everything in inches.

With 23 years in the carpentry trade...I have a feel for both. Here in Canada, all residential work is in imperial (inches, feet) but the commercial sector (my area) is all metric.

[GM]

40% reduction is theory, real world varies: http://web.archive.org/web/200210070...ces/fiberfill/ Also, different materials require different stuffing densities.

Accurate reproduction down low requires a compression horn, but the size can be pretty intrusive, so a critically damped 0.5 Qtc sealed is the traditional choice. This dates to when 'subs' had to be XO'd at > 250 Hz due to the size/cost of passive XOs though, so in today's world where it can be XO'd wherever we want combined with our poor hearing acuity down low, higher Qtc alignments can be used to keep box size reasonable.

GM

[Ron E]

If you stuff the heck out of the box, you can realistically expect a 20-30% reduction in volume. You want to keep the stuffing a few inches away from the woofer basket (and pole vent if there is one) or you may end up with a really dull sound.

Speed is a misnomer, and most of the "effects" you cite are well beyond the frequency realm of a subwoofer. To get a good solid 40Hz out of a sealed box I would look at a 10-12" woofer. Many subwoofer problems are more integration problems than problems with the woofer or alignment. You need to pay close attention to crossover frequency and placement. Stereo subs (perhaps built as stands for your mains) is more hifi, IMO.

[HK26147]

IMO: One Q&D evaluator of woofer merit is still R Small's EBP: ( fs/ Qes ) - with EBP in the vicinity of 50 or less indicating a sealed enclosure would be more suitable, while EBP of around 100 suggesting a vented enclose.
The RSS210HF-4 has a EDP of 87;
P.E. shows suggested sealed and vented boxes ( generated by BassBox? ).
So it can be "jammed" either way.
Since bass taste is subjective; there are those who prefer a low Q and there are those who have designed for higher Q.
( I measured the Q of my sealed MTM at .7 )

[Lewis Moon]

I didn't see where PE suggested volumes....where did you see that? (not that I would follow their advice explicitly)
I did some measurements using the 1492 box and subtracted the volume of the amp, driver and bracing, multiplied for the stuffing and came out with an apparent volume of 1827 which gives a Qtc of .715 and an F3 around 42 hz. How does that "sound"?

[HK26147]

2008 Catalog page 173:
Sealed .36 cu. ft. 57Hz f3
Vented 1 cu ft 32 f3.
* The PE cat says based upon Bass Box 6 using "typical" loss and stuffing and "optimum" volumes:
In general I have found that to mean a .707 Q for a sealed box, and for a vented a QB3 or SQB3 alignment with a Ql estimate of 7 ( a middle of the road sort of thing ).
Qtc's are points on a continuum, the generalization is that high Q's are "warm" and lower Q's ( .7 -.8 ) are "transient perfect" and lower Q's around .5 are usually regarded as over dampened.
But you have advocates/designs on both ends of the Q range.

I do agree that if you have space for a bigger driver than an 8" that it should be used. Bass is a matter of displacing air - and an 8" has a disadvantage in that it's small diameter means it must have a greater stroke ( excursion ) to move the required Vd. to achieve a target SPL.
A larger woofer ( bore ) has to move less to displace the same vol of air.
For the same amount of money ( sometimes less ) as that 8" there are several 10's and 12's that would work - especially in light of how frequently drivers go on sale at PE & MCM.