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Discussion Starter #1 (Edited)
This is my first post on HTS.

I will be running the dayton 15" classic 4 ohm driver with the Dayton 240w plate amplifier off the line in from my ep1500.

I would prefer a sealed box. I will probably use birch plywood because I hate cutting mdf.

The T/S parameters are as follows:
Power handling: 250 watts RMS/350 watts max *VCdia: 2" *Le: 2.30 mH *Impedance: 4 ohms *Re: 3.1 ohms *Frequency range: 20-500 Hz *Fs: 20 Hz *SPL: 92 dB 2.83V/1m *Vas: 9.70 cu. ft. *Qms: 4.00 *Qes: .50 *Qts: .44 *Xmax: 8.5 mm *Dimensions: A: 15", B: 14", C: 6-3/8".

Any ideas on a good volume? According to Winisd, the optimum sizes for a cubic box would be

1) Cubic Sealed:
Width: 23.78 inch
Height: 37.13 inch
Depth: 14.84 inch

Needed Volume: 6.131 ft^3

2) Cubic Ported
Width: 30.04 inch
Height: 47.17 inch
Distance 18.63 Inch

Needed Volume: 12.918 ft^3

Would it be possible to do something more along the lines of 2-3 cubic feet? I would prefer a smaller sub both because of room placement and because of budget.

I should also add that I would be using this 90% for music.
 

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This sub has a Xmax of 8.4 mm. In a sealed cabinet of 5 cu.ft. it will handle 100 watts before Xmax is exceeded. In a 3.5 cu.ft ported cabinet tuned to 21.5 hz, it will handle 200 watts before Xmax is exceeded. Modeling was done with the application of a 18 hz subsonic filter which I'm sure the Dayton 240w plate amplifier has. The advantage of ported is smaller box, higher power handling and higher SPL. Ported has a 4 to 6 db SPL advantage over sealed. Porting would be one 4 inch flared port 18 inches long. Here's a SPL graph of the two models.

Dayton Classic.JPG
 

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Discussion Starter #3
I appreciate your response, it would seem that a smaller box would be advantageous because it would not overdrive the subwoofer at 240watts.

I was leaning towards a sealed because, first I was under the impression that ported boxes should be larger, and second because I would like to have a more accurate sub for music given that it is much harder to engineer an accurate ported sub.


The last sub I built was a 3 cu. ft box with a 5" port and dual infinity 1052w woofers tuned to 35 hz or so for my car's trunk. I think it sounded terrible.
 

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The last sub I built was a 3 cu. ft box with a 5" port and dual infinity 1052w woofers tuned to 35 hz or so for my car's trunk. I think it sounded terrible.
Probably due to the ridiculous amount of gain in a car environment. The response graphs above are similar, the ported offering more SPL.
 

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Discussion Starter #5 (Edited)
Slot port?
Round port?
Square port?

Multiple flared round ports?

Which is better? I want the greatest accuracy.

Im starting to think that a sealed box would be better overall because at my box size requirement of <4 cu ft, i get some really awful gain around 50 hz.
 

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For a ported sub, a 4 inch flared port full length (18 inches) is the easiest. Multiples aren't necessary because of the low port air speed due to the 8.4 mm Xmax. Remember that how this sub models in either sealed or ported and in room response are two different things. If you want the greatest accuracy, that's what REW and a BFD are for.
 

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Discussion Starter #7 (Edited)
Found a large cardboard box in my attic and figured that was the largest id be willing to build, so if that was a mockup its volume was 5.3 cu ft (19"x22"x22")

So say I made a 4.5 cu ft sub, would that be better or worse than a 3.5 cu ft sub?

Additionally, For aesthetic's purposes Id like the width to be larger than the height or depth, but Id also like the sub to fire forward as I figure downfiring would sound boomy on a hardwood floor.


edit: I looked at the text file for a 4.5 cu ft sub with a 5" port and it appears to hit 108 db at 20 hz. I will probably take your advice. Winisd wants a 22" port length to get a .10 vent mach.

Number of drivers : 1
Box type : Vented
Box size : 4.500 ft^3
Tuning frequency : 20.95 Hz
Vent : 1 vent(s)
22.61 in length for each
5.00 in round


Relative
Freq Gain SPL
[Hz] [dB] [dB]
20.00 -10.10 105.88
25.00 -6.48 109.50
30.00 -3.70 112.28
35.00 -1.68 114.30
40.00 -0.37 115.61
45.00 0.38 116.36
50.00 0.76 116.74
55.00 0.92 116.90
60.00 0.96 116.94
65.00 0.94 116.92
70.00 0.89 116.87
75.00 0.83 116.81
80.00 0.77 116.75
85.00 0.71 116.69
90.00 0.65 116.63
95.00 0.60 116.58
100.00 0.55 116.53


The optimum dimensions (I havent rounded off their numbers) are:
w: 21.58"
h: 33.63"
d: 13.5"
 

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Discussion Starter #9
If the box measurements of 19"x22"x22" are external, using 3/4 inch building material would give you an internal volume of 4.25 cu.ft. Subtract the displacement of the sub and bracing would leave you approximately 4 cu.ft.
Good point. Maybe I will build to that size then.

Only problem is I keep getting confusing port length requirements or ports that have too much vent mach.
 

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Discussion Starter #11
4 cu.ft box with 200 watts input can handle a 4 inch flared port. The air speed doesn't exceed 19 m/s at 20 hz. The plate amp has a sub sonic filter at 18 hz that needs to be figured in.
Ok, it is also the bass boosting dayton.
 

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That changes things. The 6 db of boost applied at 30 hz is going to use up cone excursion very fast. Heres a new graph with 4 cu.ft. sealed and 4 cu.ft. ported both with 6 db of boost applied at 30 hz and a sub sonic filter at 18 hz. The sealed takes 35 watts to reach Xmax, the ported takes 60 watts to reach Xmax. Ported shows 109 db at 30 hz, sealed shows 104 db at 30 hz.

Classic.JPG
 

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Discussion Starter #13
interesting. Looks like ported to me. Any advice on dimensions? Would a heatgun flare the port? does that graph show a 5" diameter 18" length port as you mentioned above?
 

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Any advice on dimensions?
As long as the internal volume is 4.25 cu.ft. you can make it any shape you want.

Would a heatgun flare the port?
Only if you know what you're doing. Buying a flared port would be the simplest.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=268-352

does that graph show a 5" diameter 18" length port as you mentioned above
I've only mentioned 4 inch ports. Here's a calculator to figure out the length you need for either a straight port or a flared port.

http://www.psp-inc.com/
 

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ampire said:
I was leaning towards a sealed because, first I was under the impression that ported boxes should be larger, and second because I would like to have a more accurate sub for music given that it is much harder to engineer an accurate ported sub.
This is an incorrect stereotype that continues to live on because most people don't know how to or just simply don't build very good ported designs. The fact of the matter is that when done right, a ported subwoofer is more accurate and offers greater performance than sealed, many times by a pretty significant margin.

As for being large, that is pretty much a necessaity for a LLT (large and low tuned enclosure), but not every ported subwoofer has to be a LLT. What Mike is suggesting is a great example.
 

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Discussion Starter #16
I am still having difficulty coming up with a plan. Im really not experienced with this, and my fear is throwing away several hours and $100 worth of building materials to get a sub that doesnt sound that good.

My ideas are
1) one Round port (somewhere around 4-5" diameter but length requirements in winisd is like 20" or so which is most of the box's depth in any given direction
2) slot port that stretches across bottom (more of a car woofer design), I dont think it will sound as good but its definitely easy to build and id probably flare the opening (cut some pvc and glue it to round off the slot http://www.subwoofer-builder.com/flares-rectangular.htm)
3) sealed box and make it small and live with it being not as loud but much easier to build and also transport.

Im really confused guys :daydream:
 

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If you are really worried about building a sub that doesn't perform all that well, what I would highly suggest in this situation is that you postpone the project until you can afford a better driver. Even though ported yields better performance than sealed, there is only so much you can do with that driver. Save up untill you can get something like a IXL 15, IXL 18, Tempest X, or Maelstrom X.
 

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Discussion Starter #18
Ordered the driver already before I made the post. I will probably just go simple and build a 3cuft sealed box. Its for music, not for home theater so much, I just like the wealth of knowledge you folks have.

My budget was ~$250-300 total, and it fit the budget for a $80 sub, $100 amp, and $100 birch plywood for box.

Ill post some pictures as the project materializes, for now I wait for the stuff to come. I still have a few days to go.

My mains don't get very loud as it is, in the front two Technics SB-l71 main's from 1981, in the rear two klh model 17's from 1965 that I rebuilt, powered off of a behringer ep1500 and a laptop with no real preamp equipment(so very low gain = no vol.) Whole system was $200 total so far not excluding the sub(+250 after). it sounds good to my ears and thats all i need :)
 
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