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Simi's Official 12" subwoofer build.

similost

similost

Rockin and Rollin....
Well hot damn... My bonus is paying for this, AND, I got the wife's approval, so here's the official thread.

The plan.

Two boxes. 12" front firing woofer with front port. (help me decide.. slot, or round tube) The boxes will be 3cu ft. internal. I hope to use 1" birch ply, but may have to go with 3/4". Just depends what I find.

The box outside dimensions will be 22"w and 14" high. I will need to adjust the depth depending on the wood thickness, but I'm thinking around 19" or 20" deep.

The woofers will be GR SW-12B. http://gr-research.com/sw-12b.aspx Thanks to dumptruck for pointing these out to me.

I plan to tune the box to 21hz... unless you can show me something better. I'm just winging this point...

I am looking for a low pass filter or crossover. I want it to be between the pre-amp and the sub amp. I don't want to use a plate amp, nor do I want a passive crossover, but if I have to, I will, but would rather not. If you know of something, PLEASE let me know.

These will be placed under my Barzilay cabinets, so that's the reason I'm being pretty specific on the size of the boxes.

Once everything is all done, I'll be wrapping these in some beautiful cherry veneer I have, and then adding black grills... UNLESS.. someone might happen to know of a couple Barzilay wood grills available... but I doubt that will happen....

So, PLEASE, I am open to any and all suggestions. Other than changing the box size. I really need that to be my one and only constraint.

As I aquire the parts I built thesse with, I will list them below.

EDIT:
This is a list of parts being used....

a pair of Eminence LAB-12 drivers. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-570
Ahsly FET-500 amp to power them. http://www.ashly.com/retired/manual/man-fet200_500.pdf
Harrison Labs LP-1 crossover http://store.hlabs.com/pk4/store.pl?view_product=26
A couple packages of Driver mounting screws and T-nuts.
A Pair of Square Terminal cups with gold 5 way binders. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-284
 
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ooooohhhh... NICE Ray... I had seen those, but I didn't think they would work, but now that I really look at them, and think about it, yep... I get it now.. THANKS!!!!! That's one less thing to sort out.. .

So, knowing this now, what would you think a good crossover point would be? I'm thinking right around 50hz? Maybe up to 80?... I was even thinking as low as 40... My Barziwaves have plenty of punch once the volume gets up there, especially around 40hz, but for lower volumes, I'm not sure... guess I can just buy a hand full of these and experiment would be my best bet huh?
 
Hard to say where to bring in the subwoofer without subjective experience of the system, but your Barzilay is vented IIRC, so should have fairly low excursion down to Fb, under which it goes up pretty fast. This frequency might be a good point to cross-over and really keep the TD15M from moving much.

Thanks for posting these line Xovers RayW, I never saw these before and they look like fun. I assume they have their way to swamp the amp's input impedance so as not to have the Xover frequency vary?

az
 
Yes, the Barzilay's are ported and tuned to 37hz.. I'm thinking I'll try the 50hz and the 70hz filters.. .

So anyone see any reason not to tune the subs to 21hz?
 
Simi, those are only 85 db in sensitivity....I assume your E waves are in the 90's at least? Ray, thanks for the linc, looks good for adding a sub to my Indignias!

Russellc
 
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I would use a flared port if possible, I know that space is probably limited on the baffle, but they look bad-ass and you will not have any port chuffing.
Make sure that you brace your cabinet well. I would get a full 5'x5' sheet of 1" baltic birch, or two sheets if you need it, but have enough to put a shelf brace or two in there, makes a world of difference. Also, consider dadoing the corners or box jointing them if you have the capability. The dado is easier, one reason being you can keep the dado blades set up from when you carve the channels that your slot braces slide into.
Make sure you spike your subwoofer as well.
 
Yes, I saw they are 85db... and my waves are right around 100. I did wonder about this too, but figure if I up the volume on the sub amp, I should be able to keep up with them. I'm having a hard time finding drivers that are higher SPL rated, and keep the costs reasonable, and also having a low Fs like these do. This is also why I wanted a filter before the amp, that way I can keep as much overhead as possible in it...

I was planning of going with a 3" flaired port, around 10" long, but dumptruck said that would allow the air to move too easily and unload the driver faster. I'd be afraid to go with a 2" port and get chuffing... This is why I asked for thoughts about the port... see what others think, and have found that works for them. I do have plenty of room on the front baffle. I almost thought about two 2" ports, but we all know cutting one hole is easier ;)

This is my design and working out the kinks phase... I am open to any and all suggestions except box size, but these will get built. I'd like to keep this under $500... but $400 would be nicer hence my driver selection. Can you show me something that might be a better choice and not too much more money?
 
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similost said:
Yes, I saw they are 85db... and my waves are right around 100. I did wonder about this too, but figure if I up the volume on the sub amp, I should be able to keep up with them. I'm having a hard time finding drivers that are higher SPL rated, and keep the costs reasonable, and also having a low Fs like these do. This is also why I wanted a filter before the amp, that way I can keep as much overhead as possible in it...
Click to expand...

Perhaps, but what has to be considered is the effect on the sub drivers in doing so. Excursion vs. frequency vs. input power type thing.

Granted, with 100dB speakers, you're probably running relatively low input power on average but if I did my math right here's what you're up against:

115dB from the 'waves takes roughly 30 watts. 115dB from the 85dB sub would take roughly 1,000 watts. What happens to the sub's excursion and thermal limits up there?
 
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similost said:
Yes, I saw they are 85db... and my waves are right around 100. I did wonder about this too, but figure if I up the volume on the sub amp, I should be able to keep up with them. I'm having a hard time finding drivers that are higher SPL rated, and keep the costs reasonable, and also having a low Fs like these do. This is also why I wanted a filter before the amp, that way I can keep as much overhead as possible in it...

I was planning of going with a 3" flaired port, around 10" long, but dumptruck said that would allow the air to move too easily and unload the driver faster. I'd be afraid to go with a 2" port and get chuffing... This is why I asked for thoughts about the port... see what others think, and have found that works for them. I do have plenty of room on the front baffle. I almost thought about two 2" ports, but we all know cutting one hole is easier ;)

This is my design and working out the kinks phase... I am open to any and all suggestions except box size, but these will get built. I'd like to keep this under $500... but $400 would be nicer hence my driver selection. Can you show me something that might be a better choice and not too much more money?
Click to expand...

Ahh, adjustment on the amps may cure the problem. May lose overall efficiency, but compromise must be made somewhere...

Russellc
 
Just my opinion but I would use a steeper slope on your XO then 12 db. I normaly like 18db at 50 hz. I find it blends very well with my LF.

Simi, I use an Ashly XR1001 and it really is a very good sounding unit. I don't do plate amps either! :no:
 
similost said:
So anyone see any reason not to tune the subs to 21hz?
Click to expand...

According to BB6, that woofer in a 3ft^3 box tuned to 21Hz will need a port that's 4" diameter and 22" long. You gonna put a snorkel on top? Going down to 3" gives a vent velocity of 33.5m/s which is well into chuffing territory. I try to stay under 20m/s.

If you want to tune that low it might be a good candidate for a passive radiator.
 
As much as I would love to have an Ashley, I just can't justify the cost for this. Al am also very limited on space in my credenza the gear is in. I can fit in another 4U amp, but that's going to max me out. Just not gonna have room for a crossover. This is the reason I was looking for a small filter, just like these plugs..

So explain to someone that doesn't really understand crosoover slopes too well... how much of a difference is there between a 12db and 18db slope? and please don't say 6db :D... what kind of difference would you hear?

Man... ya'll really are making me rethink the sensitivity of these drivers... I doubt I'd be running them with my speakers if my speakers are running over 100 - 110db.. but still.. to get them up there, is a 200w driver at 85db really going to get me there?????

And this is why I am asking all of this before I start buying.. .yes, I can get the wood, but I need to gigure out the other bits.. like now maybe drivers.. ugh...

OH... BTW, I do plan to use a shelf brace inside the box, and I would like to have 1" ply.. I hope the store has it... and yes, I was actually thinking of using Locked Rabbit joints.. .but if not, I got a couple of other nice routed mitered joint ideas... ain't gotta be pretty, just gotta be solid. It will be covered...
 
Huh.. thanks for that info Ray. I didn't know what kinda velocity starts huffing... ... and yeah, I saw the 4" would have to be too long when I was looking at it last night.. so that's why I had thought about two 2" tubes.. .Or I could use two 3" tubes...

OR... I could always just cut a rectangular port... Just wondering what would be my best bet... hell.. the rectangular ports on my bass bins work well. Just might be the easiest way to go...

Passives is a nice idea, but that just puts me into more money, and more parts and numbers to figure out. I really want to make this as simple as possible..
 
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Simi,

What about a slot port with a rectangular insert that can be slid closer to the back of the inside of the enclosure and moved or tuned forward in 1/2" increments until you find what your looking for. :scratch2:
 
similost said:
So explain to someone that doesn't really understand crosoover slopes too well... how much of a difference is there between a 12db and 18db slope? and please don't say 6db :D... what kind of difference would you hear?
Click to expand...

The slope is the amount of output that will decrease from the XO point per octave. So a 12 db slope XO will drop (attenuate) 12 db per octave. So an 18 db slope will get the higher frequencies (on a low pass) out of the playable range quicker.
Does that make sense?
 
similost said:
Yes, the Barzilay's are ported and tuned to 37hz.. I'm thinking I'll try the 50hz and the 70hz filters.. .
Click to expand...

I guess 37Hz is kinda low and would not have the sub cover much, I guess the 50Hz filter is a good starting point. The B'waves will still take care of the punch region.

IG
 
Huh... I like this idea.. BUT... and this is only cause I don't know any better... if you did something like this, how would you know what size to cut the hole, then how far to move it to get your tuning you want?

I mean... say I decide to tune the box at 28hz with just strictly the size of the slot... then say I want to try 23hz.... so if I make the slot longer (deeper into it with an extension piece(like a slide pipe sorta)) into the box then would that start tuning me downwards to 23hz? Or would it start tuning it up? Seems if I remember, longer is lower, right?
 
juniorJBL said:
The slope is the amount of output that will decrease from the XO point per octave. So a 12 db slope XO will drop (attenuate) 12 db per octave. So an 18 db slope will get the higher frequencies (on a low pass) out of the playable range quicker.
Does that make sense?
Click to expand...

Yep.. makes a lot more sense to me now.. thanks... faster roll off basically... .Now I just gotta start understanding octives... I mean I understand and octive in music, I just don't in speakers... but I know each music note is a hz of one or another... same principle to speakers?
 
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