ATTN: Austin519
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From: Brooklyn, NY
ATTN: Austin519
Hey whats up. I know you know your stuff thats why I'm asking you this. Would this box be good for my 3 JL 12W3's? The specs are in the item description. Heres the link. Thanks.
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Joined: Sep 2001
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From: Austin, TX
96TL:
Thanks for the compliment
Before I go further let's look at the 12w3 box specs:
Sealed Enclosure: 1.00-1.50 cu ft.
Ported Enclosure: 2.00-3.00 cu ft.
BandPass Enclosure: 1.00 cu ft. for sealed box side, 1.6 cu ft. for ported side (including port), 6" dia., 12" deep
JL suggested Bandpass: http://www.jlaudio.com/subwoofers/pd...W3BandPass.pdf
The SoundDomain box:
Internal volume: 2.64 cu ft., or .88 cu ft. per woofer
Dimensions: 13 1/4" H x 38 13/16" W x 13 3/4" D
Thickness: Unknown MDF
Box Type: Sealed Box (so it looks like)
The eBay box:
Internal volume: 2.25 cu ft., or .75 cu ft. per woofer
Dimensions: 43 1/8" w x 14" h x 20 1/2" d
Thickness: 3/4" MDFP
Port Number and Size: 6, 4" dia., 6" deep
Box Type: Bandpass Reflex (so it looks)
First I want to say something. Neither of these boxes are very difficult to build. Additionally, neither are worth what they are asking for, especially not the used eBay box with holes already made in it from screwing in the RF subs. I'd suggest you build your own. But assuming you want one of these two...
Let's talk about the SoundDomain box:
It's a sealed box, so the box dimensions don't really matter as much as the internal volume. The internal volume per woofer is .88 cu ft. The internal volume suggested for your subs at a minimum is 1.00 cu ft. So you have a volume that's 12% less than you need. What will this cause? Well, JL figures out the needed volume of air in terms of air compression ratios and various other factors. Basically at room temperature, the w3 need around 1.00 cu ft. or more of air behind it in a sealed box to compress and decompress. With a smaller amount of air, you're compressing the air behind the sub to a higher pressure than if the air behind it had a larger volume. The sub will not be able to compress this smaller volume of air to the same level as it would a larger volume of air. Thus the Xmax (linear excursion) of the subwoofer will be diminished and the sub will move less, thus moving less air and not outputting as much sound. This air compression problem drops off as an inverse square...so the lower you go below the minimum set the worse the output gets exponentially. With that said, you can go under their minimum specs by about 10% if you live in a hot climate (where the air is less dense and thus easier to compress), a non humid climate (same effect), a high altitude climate (also same effect), and if you fill the box with Polyfill or similar (which will increase the volume of the box as seen by the woofer). However, if you live in a cold climate, low altitude climate, or humid climate...or any combination of these...I would seriously think about purchasing this box. Because the fact that the air is harder to compress not only means that the sub will output less, it also means it will output at a slightly higher frequency (unnaturally so) and will not be able to handle the same amount of power. So if you buy this box and don't live in the climate I said, don't push your speakers all the way.
the eBay box:
First know that I'm assuming this is a bandpass reflex box...which is what it looks like from the pictures. The sealed portion is the front between the plexi and holes, and the ported is from the holes to the rear of the box. Before I go on, I suggest you make sure that this box, as well as the other, has the correct hole size for your w3's. So now...
The dimensions the seller gave really make no sense when looking at this geometry of box...but just for calculations I'm going to eyeball it and say that each front window section (a total of three) looks to be about a 14"x14" square, and the distance from the plexi to the front of the hole is about 7". I'm also going to address each section in the front as if it was one section, so if you draw lines perpendicular to the three faces for mounting the speakers, you have two triangles in the front created, which I'm not going to address because of their neglibible area. Lastly, I am assuming his measurement of .75 cu ft. is per woofer for the rear ported section only. And before I start in on this box...know that these boxes, namely bandpass reflex boxes, are constructed to only pass one frequency band, usually a low band for subwoofers, say 25Hz - 60 Hz. If not tuned properly and specifically for the woofers that are to be placed in it, the bandpass box may pass hgher or lower frequencies, thus possibly not letting the sub achieve it's full potential.
So...first the sealed front part:
JL suggests 1.00 cu ft. for the sealed box portion of the bandpass box. Assuming INTERNAL dimensions of 14"x14"x7" for each sealed section...you have about .79 cu ft. per woofer, and we'll even say .83 cu ft. considering the triangles I mentioned earlier, which is generous. That is about 17% smaller than the JL recommended size. The effects are similar but much more devastating for a bandpass enclosure, and I'd have to take a lot into account when trying to figure out what this would do to the frequency and phase of the wave, but I'll just say it's not good. However you could probably get down to about .9 cu ft. for the sealed part and be alright, so again depending on climate you may be alright.
For the ported rear part:
JL suggests 1.6 cu ft. per woofer...and this box allows .75 cu ft. This is less than 50% of the volume suggested for the ported section, and is instant death for your sound reproduction. A bandpass box works by combining the effects of sealed and ported boxes, and the ports act as virtual woofers in this setup. Having a volume of less than half of suggested means that the woofer has under half the volume of air to compress; now since the sealed portion is smaller than suggested the woofer won't push as much air, but still having this little to push means that you'll get big high pressure areas and low pressure areas inside the box that were not intended. I can't really tell you what this will do to the wave, but I can say it won't be pretty, and will put even more stress on the woofer.
Finally the port:
Ports in boxes are not as big of an issue in terms of length, but in terms of diameter. The diameter of this port is fine. I will say that formula-wise the port isn't long enough, but it's not accurate to compare it to the 12" length of the JL box's port. Having a shorter port will lead to strange resonance within the port that makes for a strange sound, as well as destructive interference. Having two ports , especially that close...I don't think that was a good design plan either.
I guess what I'm saying is that I wouldn't go with either. Unless you can DIY, or unless you can get someone to do one for you, be they friend or dealer, then I guess this is all you have. Hope this helped...
Austin519
p.s. - the eBay guy...his RF subs would have hit harder in a better designed box...I believe that box was designed for looks, not efficiency or anything else. Especially with the way the ports were configured...
Thanks for the compliment
Before I go further let's look at the 12w3 box specs:Sealed Enclosure: 1.00-1.50 cu ft.
Ported Enclosure: 2.00-3.00 cu ft.
BandPass Enclosure: 1.00 cu ft. for sealed box side, 1.6 cu ft. for ported side (including port), 6" dia., 12" deep
JL suggested Bandpass: http://www.jlaudio.com/subwoofers/pd...W3BandPass.pdf
The SoundDomain box:
Internal volume: 2.64 cu ft., or .88 cu ft. per woofer
Dimensions: 13 1/4" H x 38 13/16" W x 13 3/4" D
Thickness: Unknown MDF
Box Type: Sealed Box (so it looks like)
The eBay box:
Internal volume: 2.25 cu ft., or .75 cu ft. per woofer
Dimensions: 43 1/8" w x 14" h x 20 1/2" d
Thickness: 3/4" MDFP
Port Number and Size: 6, 4" dia., 6" deep
Box Type: Bandpass Reflex (so it looks)
First I want to say something. Neither of these boxes are very difficult to build. Additionally, neither are worth what they are asking for, especially not the used eBay box with holes already made in it from screwing in the RF subs. I'd suggest you build your own. But assuming you want one of these two...
Let's talk about the SoundDomain box:
It's a sealed box, so the box dimensions don't really matter as much as the internal volume. The internal volume per woofer is .88 cu ft. The internal volume suggested for your subs at a minimum is 1.00 cu ft. So you have a volume that's 12% less than you need. What will this cause? Well, JL figures out the needed volume of air in terms of air compression ratios and various other factors. Basically at room temperature, the w3 need around 1.00 cu ft. or more of air behind it in a sealed box to compress and decompress. With a smaller amount of air, you're compressing the air behind the sub to a higher pressure than if the air behind it had a larger volume. The sub will not be able to compress this smaller volume of air to the same level as it would a larger volume of air. Thus the Xmax (linear excursion) of the subwoofer will be diminished and the sub will move less, thus moving less air and not outputting as much sound. This air compression problem drops off as an inverse square...so the lower you go below the minimum set the worse the output gets exponentially. With that said, you can go under their minimum specs by about 10% if you live in a hot climate (where the air is less dense and thus easier to compress), a non humid climate (same effect), a high altitude climate (also same effect), and if you fill the box with Polyfill or similar (which will increase the volume of the box as seen by the woofer). However, if you live in a cold climate, low altitude climate, or humid climate...or any combination of these...I would seriously think about purchasing this box. Because the fact that the air is harder to compress not only means that the sub will output less, it also means it will output at a slightly higher frequency (unnaturally so) and will not be able to handle the same amount of power. So if you buy this box and don't live in the climate I said, don't push your speakers all the way.
the eBay box:
First know that I'm assuming this is a bandpass reflex box...which is what it looks like from the pictures. The sealed portion is the front between the plexi and holes, and the ported is from the holes to the rear of the box. Before I go on, I suggest you make sure that this box, as well as the other, has the correct hole size for your w3's. So now...
The dimensions the seller gave really make no sense when looking at this geometry of box...but just for calculations I'm going to eyeball it and say that each front window section (a total of three) looks to be about a 14"x14" square, and the distance from the plexi to the front of the hole is about 7". I'm also going to address each section in the front as if it was one section, so if you draw lines perpendicular to the three faces for mounting the speakers, you have two triangles in the front created, which I'm not going to address because of their neglibible area. Lastly, I am assuming his measurement of .75 cu ft. is per woofer for the rear ported section only. And before I start in on this box...know that these boxes, namely bandpass reflex boxes, are constructed to only pass one frequency band, usually a low band for subwoofers, say 25Hz - 60 Hz. If not tuned properly and specifically for the woofers that are to be placed in it, the bandpass box may pass hgher or lower frequencies, thus possibly not letting the sub achieve it's full potential.
So...first the sealed front part:
JL suggests 1.00 cu ft. for the sealed box portion of the bandpass box. Assuming INTERNAL dimensions of 14"x14"x7" for each sealed section...you have about .79 cu ft. per woofer, and we'll even say .83 cu ft. considering the triangles I mentioned earlier, which is generous. That is about 17% smaller than the JL recommended size. The effects are similar but much more devastating for a bandpass enclosure, and I'd have to take a lot into account when trying to figure out what this would do to the frequency and phase of the wave, but I'll just say it's not good. However you could probably get down to about .9 cu ft. for the sealed part and be alright, so again depending on climate you may be alright.
For the ported rear part:
JL suggests 1.6 cu ft. per woofer...and this box allows .75 cu ft. This is less than 50% of the volume suggested for the ported section, and is instant death for your sound reproduction. A bandpass box works by combining the effects of sealed and ported boxes, and the ports act as virtual woofers in this setup. Having a volume of less than half of suggested means that the woofer has under half the volume of air to compress; now since the sealed portion is smaller than suggested the woofer won't push as much air, but still having this little to push means that you'll get big high pressure areas and low pressure areas inside the box that were not intended. I can't really tell you what this will do to the wave, but I can say it won't be pretty, and will put even more stress on the woofer.
Finally the port:
Ports in boxes are not as big of an issue in terms of length, but in terms of diameter. The diameter of this port is fine. I will say that formula-wise the port isn't long enough, but it's not accurate to compare it to the 12" length of the JL box's port. Having a shorter port will lead to strange resonance within the port that makes for a strange sound, as well as destructive interference. Having two ports , especially that close...I don't think that was a good design plan either.
I guess what I'm saying is that I wouldn't go with either. Unless you can DIY, or unless you can get someone to do one for you, be they friend or dealer, then I guess this is all you have. Hope this helped...
Austin519
p.s. - the eBay guy...his RF subs would have hit harder in a better designed box...I believe that box was designed for looks, not efficiency or anything else. Especially with the way the ports were configured...
Banned
Joined: Sep 2001
Posts: 2,418
Likes: 0
From: Austin, TX
96TL:
I forgot to mention...if you're going for the most efficient setup and best SPL (loudness), you'll want a bandpass or ported reflex setup. However, if space is an issue, or if you want an easy box to build that you can't screw up the sound reproduction on too much, go for a sealed box enclosure. Sealed box enclosures need a lot less volume than ported for an arbitrary speaker, and ported reflex needs a lot less than bandpass reflex.
Austin519
I forgot to mention...if you're going for the most efficient setup and best SPL (loudness), you'll want a bandpass or ported reflex setup. However, if space is an issue, or if you want an easy box to build that you can't screw up the sound reproduction on too much, go for a sealed box enclosure. Sealed box enclosures need a lot less volume than ported for an arbitrary speaker, and ported reflex needs a lot less than bandpass reflex.
Austin519
Thread Starter
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Joined: Jul 2000
Posts: 2,813
Likes: 1
From: Brooklyn, NY
Originally posted by Austin519
tre:
What? I know you're not laughing at my post length!
96TL:
Did I scare ya off with too much info bud? Hee hee...
Austin519
tre:
What?
I know you're not laughing at my post length!96TL:
Did I scare ya off with too much info bud? Hee hee...
Austin519
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Thread Starter
Ex-Mod
Joined: Jul 2000
Posts: 2,813
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From: Brooklyn, NY
Hey Austin, I got another question for you. What does the "Phase Warp" knob do on the old body RF amps? I have no clue. I keep it set in the middle. Does this affect my sound at all?
