Building a Dayton 15" classic 4 ohm, sealed

[ampire]

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.

[Mike P.]

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.

[ampire]

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.

[Mike P.]

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.

[ampire]

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.

[Mike P.]

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.

[ampire]

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"

[Mike P.]

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.

[ampire]

Mike P. wrote:

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.

[Mike P.]

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.