DIY Sub with DAYTON RSS315HF-4 in progress; Can someone check my math?

[bcycle]

So I have begun DIY sub project. I have ordered some parts including A DAYTON RSS315HF-4 12" HIGH FIDELITY SUBWOOFER (295-464) and a DAYTON SA240 240W SUBWOOFER AMPLIFIER (300-804 ) from Parts Express. Originally, I was going to use Dayton's 15" Quatro driver but that would have required a 6 cu.ft. box. The one I ordered is supposedly a higher end driver allowing for a smaller box one is (closer to a 4 cu.ft.) My plan is to build a box around 25"H x 18"W x 22"D with some simple bracing and a 4" flared port, locating the driver on the front of the box. I used some software to determine that this one models F3 around 21.15Hz which for my needs should be just dandy. The tech guy at Parts Express also suggested I "use as much damping (fill) as possible (without blocking the path from the rear of the woofer to the port). This will decrease group delay (boominess)". But, after adding more stuffing, the F3 jumps up to about 27hz! Now I don't know if my old ears can even hear 27hz, but I'm wondering if this is the right driver for the money. On the other hand, I'm still pretty close to my goal of spending around $200.00 for parts to build this thing.

My goals is to build a Sub that's not to big, sounds good for music and HT. I won't be playing at ear splitting volumes but pretty llou from time to time. If you had to configure these parts, what would you do? Would you use different parts keeping in mind the budget? Any other suggestions are welcome!!

Thanks,

Greg

Driver Specs:
Specifications: *Power handling: 400 watts RMS/700 watts max *VCdia: 2-1/2" *Le: .95 mH *Impedance: 4 ohms *Re: 3.3 ohms *Frequency range: 23 - 1,000 Hz *Fs: 23 Hz *SPL: 89 dB 2.83 V/1m *Vas: 3.00 cu. ft. *Qms: 3.00 *Qes: .52 *Qts: .44 *Xmax: 14mm *Dimensions: A: 12-3/8", B: 11-1/8", C: 5-3/8".

[simon5]

Why stuffing made the F3 climb? F3 will go down with stuffing, unless you overstuff...

[bcycle]

See attached, thanks

Originally posted by simon5
Why stuffing made the F3 climb? F3 will go down with stuffing, unless you overstuff...

[lousymusician]

I'm a new guy here, so you can take my reply for what it's worth, but since I just went through the same choices for my sub I'll throw in my 2 cents.

I went with the 15" Quattro in a ~2.5 ft^3 sealed box (16'"x 17.5" x 20" outside dimensions), and the 300 W BASH amp. I just got the thing running yesterday, and have spent a few hours doing setup and tuning this weekend.

WinISD models my box at f3 = 40 Hz, Qtc=.755. In that box the Quattro should handle about 200 W, good for over 110 dB. At that level, it won't botttom even at 10 Hz. With music having no content under 35 Hz, it will go even louder. I'll never hit it's limits!

In my irregularly shaped combined living room/dining room/entry hall (4400 ft^3, longest dimensions 25' x 24.5' x 9'), I'm seeing response pretty flat to 30 Hz. I couldn't really hear much from a 20 Hz warble tone, but all of the crystal in a hutch on the back wall of the DR started to rattle like a sustained earth quake. I don't think my room would want too much more bass!

The HF wants a much bigger box, vented or sealed. It really didn't look good in a sealed box. In a small box the Q was too high, in a big one the LF excursion is not controlled (limited power handling/SPL). In a vented box it goes a bit deeper than the sealed Quattro and would play a bit louder, but it's a lot bigger and a bit more expensive. Like any vented box, below cutoff the cone excursion is not controlled and needs a high-pass filter. Ultimate volume is limited by excursion at 109 dB @ 35 Hz.

None of that means you made a bad choice, the HF should play very low at non-OSHA approved levels! It's all about the compromises you want to make. For me, I took 4 dB less at 20 Hz in exchange for a smaller box, less $, more ultimate party SPL (not that I'll ever need it) and no fear of ever bottoming out the woofer. Plus that 15" woofer really makes a visual statement in the room! I'm glad my wife tolerates my obsessions!

[simon5]

Read this, might find it interesting :

http://web.archive.org/web/200208082...ces/fiberfill/

[bcycle]

Good info. One reason I'm asking people to look at my numbers is that with bass Box Pro I'm getting this with the HF driver:

--Description--
Name:
Type: Vented Box
Shape: Prism, square (optimum)
--Box Parameters--
Vb = 3.239 cu.ft
V(total) = 3.487 cu.ft
Fb = 19.99 Hz
QL = 6.488
F3 = 23.44 Hz
Fill = normal
--Vents--
No. of Vents = 1
Vent shape = round
Vent ends = one flush
Dv = 4 in
Lv = 22.2 in

And from the 15" Quatro in a vented enclosure I'm getting:

Box Properties
--Description--
Name:
Type: Vented Box
Shape: Prism, square (optimum)
--Box Parameters--
Vb = 5.484 cu.ft
V(total) = 5.711 cu.ft
Fb = 19.25 Hz
QL = 5.98
F3 = 27.91 Hz
Fill = none
--Vents--
No. of Vents = 1
Vent shape = round
Vent ends = one flush
Dv = 4 in
Lv = 14.03 in
A
B
C
--External Dimensions--
A = 36.21 in
B = 22.95 in
C = 15.51 in
--Internal Dimensions--
A = 34.71 in
B = 21.45 in
C = 13.26 in
--Wall Thickness--
Front = 1.5 in
Side = 0.75 in
Driver Properties
--Description--
Name: 295-560 (published)

--Configuration--
No. of Drivers = 1
--Driver Parameters--
Fs = 21 Hz
Qms = 14
Vas = 6.6 cu.ft
Xmax = 0.394 in
Sd = 126.1 sq.in
Qes = 0.42
Re = 3.45 ohms
Le = 3.5 mH
Z = 4 ohms
Pe = 300 watts

I'm still not 100% on how to inteperate these specs (but I'm learning). But in vented boxes, they look pretty close except the HF shows a smaller box and better vent contol (I think)

Originally posted by lousymusician
I'm a new guy here, so you can take my reply for what it's worth, but since I just went through the same choices for my sub I'll throw in my 2 cents.

I went with the 15" Quattro in a ~2.5 ft^3 sealed box (16'"x 17.5" x 20" outside dimensions), and the 300 W BASH amp. I just got the thing running yesterday, and have spent a few hours doing setup and tuning this weekend.

WinISD models my box at f3 = 40 Hz, Qtc=.755. In that box the Quattro should handle about 200 W, good for over 110 dB. At that level, it won't botttom even at 10 Hz. With music having no content under 35 Hz, it will go even louder. I'll never hit it's limits!

In my irregularly shaped combined living room/dining room/entry hall (4400 ft^3, longest dimensions 25' x 24.5' x 9'), I'm seeing response pretty flat to 30 Hz. I couldn't really hear much from a 20 Hz warble tone, but all of the crystal in a hutch on the back wall of the DR started to rattle like a sustained earth quake. I don't think my room would want too much more bass!

The HF wants a much bigger box, vented or sealed. It really didn't look good in a sealed box. In a small box the Q was too high, in a big one the LF excursion is not controlled (limited power handling/SPL). In a vented box it goes a bit deeper than the sealed Quattro and would play a bit louder, but it's a lot bigger and a bit more expensive. Like any vented box, below cutoff the cone excursion is not controlled and needs a high-pass filter. Ultimate volume is limited by excursion at 109 dB @ 35 Hz.

None of that means you made a bad choice, the HF should play very low at non-OSHA approved levels! It's all about the compromises you want to make. For me, I took 4 dB less at 20 Hz in exchange for a smaller box, less $, more ultimate party SPL (not that I'll ever need it) and no fear of ever bottoming out the woofer. Plus that 15" woofer really makes a visual statement in the room! I'm glad my wife tolerates my obsessions!

[lousymusician]

My apologies - I had a bad entry for the Vas of the HF in Win ISD. The overall curves do look very similar now. Both subs could probably use some filtering to prevent over-excursion and chuffing below 20 Hz, but that's pretty much a given with a vented woofer.

Now that I have established my lack of credibility, I'd guess your sub will come out just fine!

[bcycle]

Ah, I feel better now. Also simon5's post had some very interesting stuff (no pun intended). Apparently overstuffing the cabinet can lower the f3. The link that describes this wacky concepthttp://web.archive.org/web/200208082...ces/fiberfill/ was working today but now seems to be broken.

Originally posted by lousymusician
My apologies - I had a bad entry for the Vas of the HF in Win ISD. The overall curves do look very similar now. Both subs could probably use some filtering to prevent over-excursion and chuffing below 20 Hz, but that's pretty much a given with a vented woofer.

Now that I have established my lack of credibility, I'd guess your sub will come out just fine!

[pjpoes]

I think people haven't gotten a little carried away with the use of WinISD and Bassbox, etc. They rely so heavily on how subs model in these programs, and make such a big deal about making them look in a free air theoretical model what they want in their room. My understanding is that you dont want a sub that measures flat to 20hz free air or it will have too much energy in that area in a room, because of room gain. Most Subs I have seen designed by proffessionals, in both real and kit form show an FS that is much higher than what most people are desiging around here, and I was told that was quite intentional.

I can say my own recent project, using this subwoofer in a 2 cubic foot box, which gave me a very high fs of about 37hz or so, with a little eqing, which I first modeled and later measured to get the numbers right, and now I have a response that is flat to below 20hz. I can hear something with 20hz warble tones, whether its the fundamental I can't say. Without the eq I still get an F10 of 20hz or so.

As for the excursion issue, yes it is known that subs will exceed excursion, given too much power, below the tuning frequency. However, generally this tuning frequency is low enough as not to be a big issue. Most ported speakers are not designed with a highpass filter in the low end, but dont see this over excursion very often. I wouldn't worry about it, if anything, even with an active filter, I would be more concerned with the effect the filter will have on the phase response. Look at how a sub models with a high and low pass filter, and just to really screw things up, try throwing some eq into the mix, see how that looks.

[lousymusician]

Originally posted by pjpoes
I think people haven't gotten a little carried away with the use of WinISD... ...I can say my own recent project, using this subwoofer in a 2 cubic foot box, which gave me a very high fs of about 37hz or so, with a little eqing, which I first modeled and later measured to get the numbers right, and now I have a response that is flat to below 20hz. I can hear something with 20hz warble tones, whether its the fundamental I can't say. Without the eq I still get an F10 of 20hz or so.

As for the excursion issue, ...Most ported speakers are not designed with a highpass filter in the low end, but dont see this over excursion very often...., I would be more concerned with the effect the filter will have on the phase response. Look at how a sub models with a high and low pass filter, and just to really screw things up, try throwing some eq into the mix, see how that looks.

Face it, WinISD is a pretty fun toy! The last time I built a speaker, a hand calculator was the height of technology. This is much more entertaining, and I understand the tradeoffs in my choices much better for having the easy simulation tool.

I much agree with your basic point that it's too easy to get caught up in chasing numbers. I designed for an F3 of 40 Hz, counted on room gain to fill in below that, and it seems I got what I expected.

My concerns about headroom and excursion are basically about conservative design. I want a system that will handle ludicrous movie soundtrack infrasonics or accidental abuse gracefully. I don't have the freedom to design fancy limiting circuitry into my amp, so I tried to choose a woofer, a sealed box and an amp that had similar performance envelopes. To me, a design that would allow the driver to bottom too easily is out of balance. Since I have to live with my compromises, I chose what I'm comfortable with. If the same conservative approach means low group delay, so much the better.