Hi again everyone, I'm designing a sub woof box around the Parts express 15" Titanic 4 I received for my birthday. I listen to Classical and jazz and I love tight base, little overhang and bass extension, no boom lol. I know 0.7 q is ideal but I was wondering since I have the space would a 4.5 cubic box ( I have almost all the materials for this size and 400 watts rms power how would a q of around 0.64 please me? No chance of boom here 
. Have a great day!
. Have a great day!
What're you using as a crossover?
Where will this be placed in your room?
Do you have any eq available?
What will be powering it?
Do you have any particular low-end cutoff in mind?
What's the rest of your system?
Chances are you'll probably like it, but you haven't told us nearly enough for us to tell you what exactly it'll do...
Chris
Where will this be placed in your room?
Do you have any eq available?
What will be powering it?
Do you have any particular low-end cutoff in mind?
What's the rest of your system?
Chances are you'll probably like it, but you haven't told us nearly enough for us to tell you what exactly it'll do...
Chris
Hi,
Sealed and well stuffed might add about 20% to cabinet
volume and drop Qbox a little lower. If you like it tight
and extended then dropping Qbox below 0.7 will be
absolutely fine if you don't mind the larger cabinet.
Anywhere between 0.6 and 0.7 will be fine.
FWIW some would argue the best sealed alignment
is near Bessel *, Q=0.58. However many subs that
are suitable for sealed boxes need impractically large
cabinets for Qbox = ~ 0.6, compared to ~ 0.7.
rgds, sreten.
* It has the flattest group delay of sealed boxes.
Sealed and well stuffed might add about 20% to cabinet
volume and drop Qbox a little lower. If you like it tight
and extended then dropping Qbox below 0.7 will be
absolutely fine if you don't mind the larger cabinet.
Anywhere between 0.6 and 0.7 will be fine.
FWIW some would argue the best sealed alignment
is near Bessel *, Q=0.58. However many subs that
are suitable for sealed boxes need impractically large
cabinets for Qbox = ~ 0.6, compared to ~ 0.7.
rgds, sreten.
* It has the flattest group delay of sealed boxes.
Type of alignment
Here is my thinking. The box will be filled but not stuffed with acoustic fill. That would make the interior closer to about five square feet and lower the Q to about 5.6, a little weak perhaps but fast and tight with little boom. Mitigating the fact that it will be a little weak is the fact that I must employ corner spacing and the fact that the room is small, 10x13x8 so I'll get room gain there. I would expect about 18Hz minus about five or 6db from a baseline 105 db. Any one see a flaw?How do most feel regarding a .07 alignment verses Bessel allignment of .058? Oh buy the way I have almost unlimited eq available Up to 18 db boost or cut at 20 Hx 25Hz, 30 Hz and up. One channel of a big Crown amp is the driver. Thanks again Mark
Here is my thinking. The box will be filled but not stuffed with acoustic fill. That would make the interior closer to about five square feet and lower the Q to about 5.6, a little weak perhaps but fast and tight with little boom. Mitigating the fact that it will be a little weak is the fact that I must employ corner spacing and the fact that the room is small, 10x13x8 so I'll get room gain there. I would expect about 18Hz minus about five or 6db from a baseline 105 db. Any one see a flaw?How do most feel regarding a .07 alignment verses Bessel allignment of .058? Oh buy the way I have almost unlimited eq available Up to 18 db boost or cut at 20 Hx 25Hz, 30 Hz and up. One channel of a big Crown amp is the driver. Thanks again Mark
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Hi,
Stuff it bigtime. If you don't like the Q reduce the box size.
Corner placement is poor but you've fortunately got a
reasonable set of room ratios, allowing about 25%/
30% placement along a back (preferably) or side wall.
Low Q (0.5) is about using room gain, Q 0.7 isn't as much.
And FWIW when you get to Qbox = 0.5 there are loads
of deep tuned vented alignments that do a quasi 1st
order rolloff to match typical room gain and offer a
substantial increase in the low bass maximum SPL.
rgds, sreten.
Stuff it bigtime. If you don't like the Q reduce the box size.
Corner placement is poor but you've fortunately got a
reasonable set of room ratios, allowing about 25%/
30% placement along a back (preferably) or side wall.
Low Q (0.5) is about using room gain, Q 0.7 isn't as much.
And FWIW when you get to Qbox = 0.5 there are loads
of deep tuned vented alignments that do a quasi 1st
order rolloff to match typical room gain and offer a
substantial increase in the low bass maximum SPL.
rgds, sreten.
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Room gain is always there and you cannot choose when to use it just by changing the Q value.
AFAIK it's impossible to approach a 1st order rolloff by using any vented aligment which is a 4th order one...
Interesting comments about using Q with room gain by sreten. We should (OP) know (and model) the room (dimensions) then (with the driver).
More on Q by Tony (wintermute@diyAudio) and pics below for OP.
http://www.diyaudio.com/forums/multi-way/241449-new-program-room-response-simulation.html
http://www.diyaudio.com/forums/multi-way/252369-cabinet-size-help.html#post3844532
More on Q by Tony (wintermute@diyAudio) and pics below for OP.
http://www.diyaudio.com/forums/multi-way/241449-new-program-room-response-simulation.html
http://www.diyaudio.com/forums/multi-way/252369-cabinet-size-help.html#post3844532
Attachments
There's something awkward about a 4.5 cubic ft enclosure.Hi again everyone, I'm designing a sub woof box around the Parts express 15" Titanic 4 I received for my birthday. I listen to Classical and jazz and I love tight base, little overhang and bass extension, no boom lol. I know 0.7 q is ideal but I was wondering since I have the space would a 4.5 cubic box ( I have almost all the materials for this size and 400 watts rms power how would a q of around 0.64 please me? No chance of boom here
Is that the Titanic Mk III or Mk 4?!
Dayton Audio TIT400C-4 15" Titanic Mk III Subwoofer 4 Ohm | 295-420
Dayton Audio TS400D-4 15" Titanic Mk 4 Subwoofer 4 Ohm | 295-405
Plus the data is not the same in the Dayton Audio driver website vs. pdf and they need to correct this because is not the same driver specs or measurements where than with different drivers.
You get a benefit (using the pdf parameters above for simulation) from a Qtc of 0.7 to a Qtc of 0.6 but you don't gain nothing going lower than that (Qtc 0.5) in terms of output and extension.
DAYTON TS400D-4 Titanic Mk 4,
VB = 107.0 L, QTC = 0.706, F3 = 35 Hz (107L = 3.8ft³)
VB = 175.0 L, QTC = 0.600, F3 = 37 Hz (175L = 6.2ft³)
VB = 240.0 L, QTC = 0.550, F3 = 39 Hz (240L = 8.5ft³)
Your enclosure of 4.5ft³ = 127.5L with QTC = 0.66 (F3=35Hz) is adequate to me. You only need 330W to achieve max excursion (driver is 900 RMS).
DAYTON TS400D-4 Titanic Mk 4,
VB = 107.0 L, QTC = 0.706, F3 = 35 Hz (107L = 3.8ft³)
VB = 175.0 L, QTC = 0.600, F3 = 37 Hz (175L = 6.2ft³)
VB = 240.0 L, QTC = 0.550, F3 = 39 Hz (240L = 8.5ft³)
Your enclosure of 4.5ft³ = 127.5L with QTC = 0.66 (F3=35Hz) is adequate to me. You only need 330W to achieve max excursion (driver is 900 RMS).
Attachments
The four All APPRECIATED people!!. Inductor, your math seems to be spot on! I'm coming up with a roll off of about 5db by 18 hz. Interesting thoughts on corner placement, Placement with which I'm stuck with as well as the "odd" 4.5 cubic foot measurement was a build in far before I bought the house. . I've just never wanted to invest in the "TITANIC" before lol. Oh and as an aside, what a beautiful job of design. They list Xmax. at 18.9 but although I don't dare measure it ,it seems more like 22mm. But I digress, Corner placement will increase bloat!! 30-90Hz and decreasing Q to my estimated 5.9 will certainly lower the " boom factor. I was asked about EQ. Should I use it knowing the greater power requirements. using five db steps at what frequency and how much should be applied? Please keep in mind that my room is small, 13X10X8.5 and reaching 108 db should be more then I need. Oh just an aside I have yet to hear any ported system that could duplicate just a 12db per octave rolloff of a sealed box. Does anyone agree that I should "stuff the hell out of the box or just go with my original intent of full but lightly packed acoustic stuffing? Have a great day all, I'm here in Ct and at 3PM the weather channel is calling for a blockbuster of a snow storm on Wed. OMG HELP!!!!!
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Hi,
Just tedious misrepresentations of my post. Which you don't understand.
rgds, sreten.
Hi,
In a small room there is no reason to not well stuff a sealed box
that will be smaller than a lightly stuffed box for the same box Q.
The only sensible reason not to well stuff a sealed box is its too big.
Corner placement can be an absolute disaster in some rooms
with unfortunate dimensions, but your dimensions are good.
The standard recommendation for one sub for hifi is placement about
30% to 40% along the rear wall behind the stereo pair of speakers.
rgds, sreten.
In a small room there is no reason to not well stuff a sealed box
that will be smaller than a lightly stuffed box for the same box Q.
The only sensible reason not to well stuff a sealed box is its too big.
Corner placement can be an absolute disaster in some rooms
with unfortunate dimensions, but your dimensions are good.
The standard recommendation for one sub for hifi is placement about
30% to 40% along the rear wall behind the stereo pair of speakers.
rgds, sreten.
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Hi Sreten, Well there are a few reasons why you should not cram stuffing. For one thing it cost money lol. For a second the box is a wee too large I have no desire to lower Q much lower then the Q of 5.8-5.6 I'm getting now. Also after a certain " magic number " just adding more may actually lower efficiency. I am even More interested in any EQ I may apply including LOWERING 30 Hx by say three DB. Does anyone make an EQ with a setting lower then 20 Hz?
Hi,
If you insist on making a box that it too big by all means
don't stuff it well, though TBH the difference is marginal.
Like I said, once you get to a box Q of around 0.5,
there are a load of very low frequency vented tunings
that down to near vented tuning are quasi 1st order,
very room gain friendly, and very effective, over sealed.
Lowering 30Hz by 3dB is utterly trivial in terms of EQ,
and senseless in terms of worrying about too low box Q.
rgds, sreten.
If you insist on making a box that it too big by all means
don't stuff it well, though TBH the difference is marginal.
Like I said, once you get to a box Q of around 0.5,
there are a load of very low frequency vented tunings
that down to near vented tuning are quasi 1st order,
very room gain friendly, and very effective, over sealed.
Lowering 30Hz by 3dB is utterly trivial in terms of EQ,
and senseless in terms of worrying about too low box Q.
rgds, sreten.
No, no really. Perhaps your comment is not clear enought, to me at least, but you said:
and I guess you are trying to say something a bit different... but really, I don't know what are you talking about: It is impossible to tune a vented design to behave as a 1st order rolloff.
PD: Please, try to be a little bit less agressive. I am not misrepresenting anything at all and I quoted your words exactly as you wrote them.
Ha ha, good point! And usually forgotten.
I don't think that was meant literally. The point is, you can "undertone" the port to have a shallower rolloff. This generally has better time response at the frequencies of interest, and works better with room gain (well, that depends a lot on placement and the particular room I suppose, but shallower matches the general gain trend better).
Stuffing the box is also about reducing internal reflections. I reworked a friend's husband's old speaker and, even as an experienced speaker engineer, was absolutely shocked how much clearer the stuffing made them sound. Now those cabinets were average wood and not super thick cones, but still.
"Lowering efficience" does not really happen. Changing box size and stuffing just "moves the efficiency" between below resonance and above resonance.
Folks worry WAY WAY WAY too much about small changes in response, based on Thiele-Small parameters that change by the day and by the measurement method.
Unless you have a hugely thick cone and a box built like a brick outhouse, I'd urge you to get a big bat of fiberglass which is not too expensive compared to the rest of what you probably spent.
If the sound gets too "thin" you can always play with placement and EQ-or shove big hunks of wood into your box!
Certainly plays into the bigger scheme of things. Objectively if we were to employ first order acoustic roll off and Geddes multisub approach helps to fill in what a less than optimal room/placement conditions and do it relatively flat.
Have designed an MLTL with this shelving down of the response using a cheap peerless 6.5" woofer for against the wall use. The design goal was a first order acoustic <~80Hz (75 actual). Usable low end is 26Hz (goal was 27), below which there is a massive increase in distortion. Total system will have 8 of these. Main speakers employ half of them. Configuration lends itself bass loading the room at two points per driver. If I can easily hit 106dB at 26Hz with one, that's far more than what is required for my typical needs. The remaining 7 are for modal smoothing and headroom
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