Home Theater Sub Design

[johnr66]

I'm am designing a vented box HT sub using WinISD (first time). I want to run this by you folks to be sure I am on track. Box will be 24hx20x20 I.D. w/ internal brace. Port velocity is .06. Will use around 100 watts rms max.

Will the tuning work well with the bass used in the deep explosion sounds used in today's movies? Will these ports be chuffing issue?
Thanks for your input.

Driver : Dayton QT385-4 15"
Number of drivers : 1
Box type : Vented
Box size : 5.500 ft^3
Tuning frequency : 25.00 Hz
Vent : 2 vent(s)
8.67 in length for each
3.00 in round


Relative
Freq Gain SPL 1w/1m
[Hz] [dB] [dB]
20.00 -7.55 84.25
25.00 -1.78 90.02
30.00 0.40 92.20
35.00 0.80 92.60
40.00 0.75 92.55
45.00 0.63 92.43
50.00 0.52 92.32
55.00 0.43 92.23
60.00 0.36 92.16
65.00 0.31 92.11
70.00 0.26 92.06
75.00 0.23 92.03
80.00 0.20 92.00
85.00 0.18 91.98
90.00 0.16 91.96
95.00 0.14 91.94
100.00 0.13 91.93

[bjorno]

Originally Posted by johnr66

..Will these ports be chuffing issue?


Driver : Dayton QT385-4 15"
Number of drivers : 1
Box type : Vented
Box size : 5.500 ft^3
Tuning frequency : 25.00 Hz
Vent : 2 vent(s)
8.67 in length for each
3.00 in round

..

Hi johnr66,

You will exceed maximum recommended Air Velocity of 10 m/S at an input power of 22W/4Ohm, i.e. use at least 4" dia. ports.

OTOH, your sub models very good using your driver/box data.

b

[johnr66]

Thanks Bjorno. I can't get WinISD to tell me port velocity with higher wattage. I guess I should find another software? I adjusted using two 4" ports. After reconfiguring the cabinet to accommodate the port length (I want the ports on the driver board), I'm ready to fire up the table saw.

[Richard Ellis]

John.... You really should consider going sealed.......
Your EBP is running at 53.48837209 which is right there (50) for going to a sealed system.......if you were running at 70-100 yeah, go ported.
Also remember your response will fall off at a 24DB per octave past Fb with ported vs. 12 Db per octave going sealed.
I came up with 3.21224057 Cubic feet of enclosure sealed........You can drop that down in size 15 % with a full stuffed enclosure.
That I would think is a much more tolerable & usefull size.

__________________________________________________ __Rick.........

[Aucosticraft]

Can you pls provide T/S for Dayton QT385-4 15".

[GM]

Greets!

I recommend you switch to at least the Pro version as it's a more elaborate, accurate program. In it, click on the 'signal' tab and input 100 W to view excursion.

Even my old 16 Hz Fb cabs are tuned a bit too high for many of today's movie LFE. Serious folks are using THs tuned to ~11 Hz or multiple driver IBs, so 25 Hz needs a high pass for some LFE. If you can tolerate a taller sub, then consider a bigger net Vb tuned low or better to add drivers and run them sealed.

FYI:

WinISD Pro tutorial: WinISD Pro Tutorial and Download (A detailed guide on how to use WinISD Pro) - Home Theater Forum and Systems - HomeTheaterShack.com

Downloadable driver files: Downloadable WinISD Pro Files - Home Theater Forum and Systems - HomeTheaterShack.com

GM

[bjorno]

FYI, A T-TQWT has IMO no port air velocity issues and smaller footprint than a BR box:

b

[johnr66]

I decided not to worry about getting so low Hz for this project. Size and cost are an issue. I looked at vented vs closed and I like vented better. Driver seems to be good for either. It will have higher SPLs in most of the low range and they cross at 16Hz. I used a 4 cu/ft sealed vs a 5.5 cu/ft vented box.

My current speakers, two 12" in their own box, F3 at 37Hz and output usable sound to 27Hz. This should be an improvement.



I used the T/S parameters from Parts Express.
Dayton QT385-4 15" Quatro Subwoofer 4 Ohm | subwoofer qt385-4 15" subwoofer dayton quattro dayton subwoofer dayton 15" woofer DayAudSub11408 | Parts-Express.com

Note some difference from the these:

QT385-4 15" Quatro Specifications

* Power Handling: 300 watts RMS/600 watts max
* VCdia: 2-1/2"
* Le: 3.5 mH
* Znom: 4 ohms
* Re: 3.45 ohms
* Frequency range: 20-125 Hz
* Magnet weight: 67 oz.
* Fs: 21 Hz
* SPL: 91.8 dB 2.83V/1m
* Vas: 6.60 cu. ft.
* Qms: 14.0
* Qes: .42 *Qts: .41
* Xmax: 10 mm
* Dimensions:
Overall Diameter: 15-1/8"
Cutout Diameter: 13-7/8"
Mounting Depth: 6-5/8".


I'll have to try the Pro ver of WinISD.

Bjorno, Interesting TH. I'll have to see how I can fold that into a box. Oh No! another TH project!

[sujiro]

There are lot of design which affects relationships. If you were to create home cinema design, it should be something that gets your appetite. Something that your family or other members of your family or even friends that they will not get bored on the place where they rest or sit while they watch something.

[Cokewithlime]

Originally Posted by johnr66

I decided not to worry about getting so low Hz for this project. Size and cost are an issue. I looked at vented vs closed and I like vented better. Driver seems to be good for either. It will have higher SPLs in most of the low range and they cross at 16Hz. I used a 4 cu/ft sealed vs a 5.5 cu/ft vented box.

I have recently(3 months ago) built two subs specifically for HT LFE channel effects using the Dayton QT385-4 15" Quatro drivers(pic of one unit below). The cabs have a internal working volume of 5.5 ft^3, use 2x 3" flared ports and are tuned to 18Hz. Each sub is driven by a 100w plate amp - XO @ 60Hz and high passed at 20Hz

I am able to drive the subs to full output(within xmax limit) of 110db with a f3 of 20Hz and a f10 of 15Hz without any port "chuffing"

The other Dayton 15" driver you mentioned is virtually(spec wise) a duplicate of the Quatro, so if you do go ahead and build using that driver I don't think you will have any problems if you choose to do a similar design.

A couple of notes however. The Quatro and the Dayton 15 are not the most musical of drivers but are a great bang for the buck in HT use and at full tilt during LFE scenes, will shake and rattle most small objects in the room that aren't nailed down - lol

btw - If you want any help with your project feel free to PM me