Sub

[MegaWatt]

My current HT sub is crap, it's 'David-301 D-BOX 12" powered sub from costco'. It's pathetic! Could i use a car audio sub with that amp and get better SPL and SQ? Would it even be worth it? The sub i have available is a alpine DVC 4ohm+4ohm, Fs 29Hz, Vas 45L, Qts 0.47. I am willing to build a box to spec if i need to.

 

[rnatalli]

My experience with car subs is that they tend to be boomy, but I admit I don't have a whole lot of experience with them. What's wrong with a good HSU or SVS HT sub? Although, building a sub is a fun project.

 

[annunaki]

Car subs are boomy if you use the enclosure recommended for the car. An enlosure designed for home use will sound pretty good. If you get me the rest of the T/S parameters, I may be able to get you some enclosure sizes that would work well in your home for the Alpine sub. Is it a Type-E, Type-S, Type-R, or Type-X?

 

[agarwalro]

Car subs are boomy if you use the enclosure recommended for the car. An enlosure designed for home use will sound pretty good. If you get me the rest of the T/S parameters, I may be able to get you some enclosure sizes that would work well in your home for the Alpine sub. Is it a Type-E, Type-S, Type-R, or Type-X?

Good advise. and a thanks for being so helpful.

 

[MegaWatt]

My experience with car subs is that they tend to be boomy, but I admit I don't have a whole lot of experience with them. What's wrong with a good HSU or SVS HT sub? Although, building a sub is a fun project.

I would love to buy a HSU or HT sub, but it's not in my budget right now so i want see if i can improve my system a tad with what i already have laying around here.

Car subs are boomy if you use the enclosure recommended for the car. An enlosure designed for home use will sound pretty good. If you get me the rest of the T/S parameters, I may be able to get you some enclosure sizes that would work well in your home for the Alpine sub. Is it a Type-E, Type-S, Type-R, or Type-X?

If you could do that i would appreciate it. The sub i have is SWR-1242D, i think you can find the parameters here. http://vault.alpine-usa.com/products/documents/OM_SWR-1242D.PDF BTW I'm a carpenter by trade


Would the amp from my crappy 'David-301 D-BOX 12" powered sub' power that alpine okay? If not what are some of my options here?

Thank you for the quick responses guys.

 

[annunaki]

Do you know what the impedance is of the current 12" sub? If you have a digital multi-meter (DMM) you could check by removing the sub from the enclosure and removing the leads from the amplifer. Once you know the impedance it may be possible to find out if it is usable or not. The other issue that would come into play is whether or not the amplifer has built in infrasonic filters or limiting circuits. What type of continuous output wattage is the amplifier capable of?

The Alpine type-R subs I have seen in the past worked quite well in lower tuned vented applications. Hopefully this stands true for the current models as well. I know they are similar in design to the Type-X which worked well in low tuned applications.

If I have some time tonight I will model the sub for you and let you know the results. If worst comes to worst, you could pick up a basic plate amp (200-300 watts) for about $100.00.

 

[annunaki]

OK, I plotted the sub and you can do a 3.5 cubic foot enclosure (net internal volume after woofer, port and bracing displacement) tuned to 23hz. You would use dual 3" aero ports (flared on both ends) at a length of 17-15/16" This will give you anechoic response of -3db at 20hz and -3db at 83hz if using a 4th order (24db/oct.) crossover at 80hz. This should be a pretty impressive sounding sub based upon the response curve especially compared to what you are used to.

This is very much a vented box woofer as well. Sealed enclosures do not offer very good response with this sub.

I think you would be extremely happy with the sub in a vented enclosure compared with what you are used to.

 

[MegaWatt]

Thanks annunaki. Could i use a single square port like this http://www.subwoofertools.com/forum/ported-box.asp?Ew=22&Eh=22&Dia=6&Xmax=18.2&Vd=0.071&NumW=1&Vb=3.5&Fb=23&Qts=&Vas=&Fs=&CE=0 or this http://www.subwoofertools.com/forum/ported-box.asp?Ew=18&Eh=18&Dia=6&Xmax=18.2&Vd=0.071&NumW=1&Vb=3.5&Fb=23&Qts=&Vas=&Fs=&CE=0 ?

 

[annunaki]

It would be ok to use a vent like that but you must take care to flare the edges with a roundover bit. 90 degree bends do not help with port noise. Dual 3" aero ports would have much less chance for noise. If one does not have experience with slot vents round ones are better off used.

The other issue is if the vent becomes too narrow you will have issues with noise as well. A 1-1/2" x 9-5/8" vent would be about the same as dual 3" ports just make it 19-1/16" long.

1-1/2" openings are about the narrowest I like to do.

If you did an enclosure at 26" deep x 17" wide x 19.5" tall (external dimensions figuring 3/4" MDF) you could do a slot vent above or below the woofer on the 17" x 19.5" panel, or you could also mount the 2-3" aeroports there as well. This would give you gross internal volume of 3.956 cu.ft. Displacement of a rectangular vent of 1.5" x 9.625" constructed internally of 3/4" mdf and the wwoofer itself would be .336 cu.ft. leaving you with .12 cu.ft. for bracing and/or amplifier displacement. That should be more than plenty.

The cuts you would need for the enclosure would be:
(2)- 17" x 19-1/2"
(2)- 17" x 24-1/2"
(2)- 18" x 24-1/2"

The cuts for the port would be:
(1)- 11-1/8" x 18-1/16"
(2)- 1-1/2" x 18-1/16"

Cuts for bracing:
(4)- 15-1/2" x 8-5/8"
(1)- 15-1/2" x 24-1/2"

You will need to router in the opening (1-1/2" x 9-5/8") of the port on the face of the 17" x 19-1/2" panel 3/4" from the edge. I would center it along the top or bottom of the enclosure.

Since I do not have a fancy design program, send me your email address in a pm and I will send you some plans (hand drawn) for a fully braced enclosure using the cuts above.

 

[annunaki]

Keep in mind that the port designs they have for you are taking up close to 1.15 cu.ft. in volume inside the enclosure. It is being accounted for, but there are 90 degree bends which do not help in terms of port noise and turbulence. They do have significant port area which may be a tad excesssive but not really a negative. They are also leaving no extra volume for woofer, bracing, or amplifier displacement. The second option you had was best.

 

[annunaki]

With my design if you want to go larger for port surface area we can figure that in as well. There should not be any audible port noise with my design based upon the figures given. I will check later tonight how much longer the port requirement would be to make the vent 1.5" x 15.5" It would be equivalent to just under dual 4" ports.

 

[MegaWatt]

Some plans would be great! I wanted to do slot vent because i figured it would be easiesr, cheaper, and add some extra bracing at the same time. If i could do rounds ports for relatively cheap with pvc i would, but i think you mentioned that they need to be flared on each end. Do you buy these? How much and where? Also should/could the sub be downfired for a better effect?

You have a PM.

 

[annunaki]

Some plans would be great! I wanted to do slot vent because i figured it would be easiesr, cheaper, and add some extra bracing at the same time. If i could do rounds ports for relatively cheap with pvc i would, but i think you mentioned that they need to be flared on each end. Do you buy these? How much and where? Also should/could the sub be downfired for a better effect?

You have a PM.

I would not suggest the sub be downfired. The ports can be purchased here, if you want to do them instead.

Since you now have the plans for the slot vent you may just want to go that route.

 

[vios500]

What do you think of the supercube I,II or III

 

[annunaki]

His budget does not allow the purchase of a new sub at this time.

 

[MegaWatt]

Annunaki thanks very much the plans look awesome! I can't wait to build this box and test it out. Looking at your plans i see 1 horizontal window brace and 2 vertical window braces on the top side and 2 on the bottom. The bracing plan looks good, but the 2 vertical window braces on the top will need a notch to accommodate the port tunnel. This means those 2 vertical braces can not have the recommended 5 1/2"h x 5 3/4"w openings, they would have smaller windows. Something like 4 - 4 3/8"h x 5 3/4"w.

Do you see any problem with that?

 

[annunaki]

No that will not be a problem. I forgot to figure that. I was in a hurry when I did it. They would need to be notched for the port. When the enclosure would be in the final assembly stages, the top panel (with port attached would lock into the two top vertical braces. The enclosure should be rock solid at that point.

I would be anxious to hear it if the build is executed correctly (which you should be able to handle). My guess is you live a bit too far away.