Time for a DIY sub project.

[billyjoe72]

First off howdy.

I usually hang out in HT, 2 channel, general and modifications. I mostly look and use info I see. I'm not rich. That being said I am always building or tinkering with wood. A while back some friends and myself were watching a movie in my garage and I took an extra ( cheap ) 12 inch pioneer woofer out of an old unused speaker and fitted into a 55 gallon drum and hooked up a low powered denon. Hmmmm I said. I moved the speaker here and there in the drum, moved the drum upside down, on its side etc. Lots of bass. Uncontrolled bass, but there anyway. So I've been watching you all talk and looking at websites listening and learning. I am going to use an arsenal 12". It has a nice name and looks pretty mean. No need for over the top yet. I'm not too concerned with size. My wife understands that.[] I know placement is important, but right now I just want to build a nice sub and worry about all else later. I watched you guys talk and it seems 5.5 or so cubic feet is about right. I tried that program and entered the data wrong somehow. Who knows. A drawing, schematic or words of direction would be appreciated. Ports and braces ( support ) seem to be my weakest area. You point me in a direction and I'll build it. I'm a visual person. The heavier the better I say. As far as powering it, I'll worry about that later too. I have a ksw 12 now. I would like to put that back in my garage. So if your bored and what to chime in on specific build plans that would be sweet.

Thanks for your time

[DrWho]

When entering driver parameters be sure to turn off the auto

calculation BEFORE your start entering any data. And then just leave

fields that you don't have data for empty.

The cheapest way to make a port is to go with a slot type, which winISD

will help you build (click the circle and it changes to a rectangle).

You should be able to get 110dB out of that driver with an F3 below 20Hz no problem.

[Jay481985]

Tell me

you speaker

your enclosure size

how good woodworking you are

bracing

amp internal or external hekc what type

what tools you have

with a f3 below 20 that means ported or pr

with the info I can draw up some autocad drawings. I charge 1 million dollars lol

joking aside with the parameters give me a few days.

[billyjoe72]

Good morning..

Speaker- arsenal 12"

Enclosure-program said closed 3.463 cubic feet

ported 6.968 cubic feet

Woodworking skills- I have all the tools.

Bracing- That's where I need help. I will brace the way someone tells me.

Amp- I would like an internal, but I would have to buy the speaker next

week and buy the amp two weeks from now. I don't like to

charge things. Amp advice would be greatful. I was looking at the

internal Dayton amp at parts express. I'm using my play money.

Ported or passive- you tell me. Which ever would have best results.

I don't have much knowledge with all the numbers you put out. I understand Hz, decibals, the simple stuff. The numbers I punched into the program were mostly numbers to me. I couldn't tell you what 80% of them were[] It did look to me like the ported hit a lower hz. What is F3?

I would like it to be taller rather than short and fat. If this effects the output one way or another, I will shape it accordingly. I eagerly await to be ordered what to do[]

Bill

[billyjoe72]

Just in case it matters, It will be complimenting a set of klf 20's, homemade center from scrapped klf 10 on ebay. ( $60 for guts + wood, what a steal ) and a set of cerwin vegas for rears soon to be replaced by my 20's when I find a pair of 30's close to me to put as mains.

Bill

[Dan1045]

I bought a sub amp from parts express before christmas and am quite pleased with it. I did a lot of reading and the steeper cutoff you can have for the sub amp, the better. So I chose the 240 watt one with 24db/octave crossover. It works great with larger speakers and with a pair of small satellites. If you dont need gobs of power, this is a good one and they put it on sale quite often.

Usually parts express ships free if the order is over $100 too.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=300-804

Dan

[billyjoe72]

Thanks for the info. I was originally looking at this one. Maybe this is overkill and I should look into a smaller amp. The arsenal 12 is 750 watts rms.

Bill

[DrWho]

Thanks for the info. I was originally looking at this one. Maybe this is overkill and I should look into a smaller amp. The arsenal 12 is 750 watts rms.

Bill

I would go with that one or its smaller 500W brother - depending of course on your final needs.

You will find the arsenal to be excursion limited and not power limited

(in other words, you won't be coming close to the 750W RMS of the

driver).

Also, F3 = the point at which the frequency response is down 3dB...the

-3dB point. It's just easier to say "F 3" than it is to say "minus

three decibal point" []

[billyjoe72]

Thanks..

So, I take it the lower the F3, the lower the driver in a proper enclosure will hit. ( Deeper ). Also curious about driver not hitting 750 watts. If you have the capability of throwing 1000 watts at a 750 watt driver would that mean the amp is working less to its potential than the driver? With that in mind, if you were building it, would you opt for twice the power for 80 bucks or get the little brother? Maybe get the little brother, take that money and instead of porting it, put in a passive.

Sorry about all the questions.

Bill.

[Jay481985]

questions are quite alright, this is a learning forum

As with amps, you should match amp with speaker, or have a slightly stronger amp

Yes the amp would work less but if you over drive the speaker it will fail due to thermal limits

porting and passive are mostly the same thing. Porting is

cheaper, the passive sound better. But passives cost alot more and the

thing is that passive are generally used for high excursion subs that

porting will cause port distortion (too much air going into too small a

hole)

[billyjoe72]

I appreciate the info again.

I believe I will go with a passive. Parts express has this one. There is a cheaper one for $25 but I won't get that cheap. A couple more questions if you guys wouldn't mind.

1. Is there a significant difference between ported and passive? Just for my records. Is it cleaner, deeper, louder to use passive?

2. Do I need to modify the box's size much to accommodate the passive?

3. Same question for the internal amp?

4. If I double layer the mdf all around, would it result in a better sounding output, or just a heavy sub?[]

5. If using passive, what position should they be in. Pointing directly away from each other I ***ume.[]

6. I've been tinkering and I think I will build it 21" w x 21" L x 28" H for 7.145 cubic feet not counting for amp space. I think thats right. This doesn't seem too big. The numbers I put in the program said it should be 6.968 cubic feet. Again, if I did it right.

7. How about spikes or feet for the beast?

8. To be continued[]

Thanks guys

[Jay481985]

I appreciate the info again.

I believe I will go with a passive. Parts express has this one.

There is a cheaper one for $25 but I won't get that cheap. A

couple more questions if you guys wouldn't mind.

1. Is there a

significant difference between ported and passive? Just for my

records. Is it cleaner, deeper, louder to use passive?

Just as the length and the wide of the port changes the tune of the

sub, a pr specs also change it. Just because plopping a pr into an

enclosure will not mean it will hit lower or louder. It needs to be in

accordance with the specs. I didn't have the time to look at a model

with that pr yet.

2. Do I need to modify the box's size much to accommodate the passive?

you need to have a wall to mount it to

3. Same question for the internal amp?

you need to cut a hole into the wall to mount it

4. If I double layer the mdf all around, would it result in a better sounding output, or just a heavy sub?[]

Less vibrations and better sound.... Dr Who fill in this blank

5. If using passive, what position should they be in. Pointing directly away from each other I ***ume.[]

Not

necessarily, they can be in any way just it has to be verticle or the

pr will not work. Meaning no horizontal mount cause the pr will sag and

not get a full stroke

6. I've been tinkering and I think I will

build it 21" w x 21" L x 28" H for 7.145 cubic feet not

counting for amp space. I think thats right. This

doesn't seem too big. The numbers I put in the program said it

should be 6.968 cubic feet. Again, if I did it right.

I know a 2X2X2 is 8 cubic feet external. the amp doesn't eat that much.

7. How about spikes or feet for the beast?

spikes for hardwood and carpet. Rubber feet for wood. It all depends

8. To be continued[]

I know it will []

Thanks guys

[billyjoe72]

To be continued...too funny. Again thanks for all the info. Like I said, most of those specs I put into the program were jibberish to me. I believe I got them in right. Here are the specs...

Arsenal 12 Specs

Top of Page

T/S Specs

Driver Specs

Znom

Dual 4 ohms

BL

21 n/a

Cutout diam.

11

Re

Dual 3.5 ohms

Sd

530 cm²

Outer diam.

12.5

Fs

27 Hz

Mms

196 g

Mounting depth

6.5

Vas

71.1 L

Xmax

20.5 mm

Weight

19 pounds

Qms

5.01

Spl

85.6 dB 1W/1M

Voice Coil diam.

2.5 inch aluminum

Qes

.59

Rec. Power

500 W

Voice coil

Dual 4 ohm

Qts

.538

Rms

750W

Cone

Paper/Kevlar fibers

Le

1.8 mH

Price

$220.00$160.00

Warrranty

3 years

As far as mounting the amp, I just didn't know whether or not I needed to add size to make up the difference in space the amp would take up. Obviously, DrWho likes heavy equipment according to your remarks.[] Again thanks for the info. Can't wait to get started. I've got some ideas on some finishes to consider. I might mix and match a few this weekend just to experiment. About the braces, if I double it up on the mdf like I said, I shouldn't need braces should I? I've never had nor heard a sub with that much kick. Well, hopefully that much kick. I don't know how much vibration that is. I do no that 1 1/2 inches of mdf is pretty damn strong. I hear a cranberry and vodka calling my name. I'll check back.[]

[DrWho]

1. ports and passive radiators both work on the same premise. Both

behave like springs that resonate at a certain frequency. The back wave

from the active driver creates a pressure inside the cabinet which then

stimulates the spring...effectively reversing the phase of the driver's

back wave which is the entire goal (converting the back wave into

usable acoustic energy). If you were to place the driver outside of a

cabinet on the floor, you would barely hear any sound because the back

wave cancels with the front wave (which is the entire purpose of

building a cabinet in the first place).

Anyways, there are slight differences between the behavior of ports and

pr's. It's easier to look at the "large signal analysis" first. All the

modelling we do in winISD is assuming that the system is perfectly

linear, but we of course know this to not be the case. At higher SPL's,

the air moving through the port starts to move faster. If it moves too

fast, we hear it as a chuffing sound (the promedias are a perfect

example of this). So it is neceassary to maintain a large enough

cross-sectional area so that the movement of the air is restricted as

little as possible...this of course requires the port to be much longer

in order to maintain the same resonant frequency. But no matter what,

you are always going to end up with some restriction to the air flow.

This restriction causes the air to compress inside which then

effectively increases the mass of the air in the port (one of the key

variables to the resonant frequency). And this slight increase in mass

actually ends up lowering the tuning point....it is for this reason

that it is always better to tune a port slightly higher than what you

calculate in winISD.

Moving onto passive radiators...you don't have any air compression

issues to worry about. All you need to do is make sure that the

suspension of the PR behaves in a linear fashion. This of course will

never be the case, but it's far more linear than ports. The other

advantage to PR's is they don't take up any internal volume. The

cabinet volume that you model in winISD is the free air space behind

the driver....and you can't include the airspace inside the port, which

usually means your cabinet needs to be an additional 1-2 cubic feet

larger (depending on the port of course). PR's take up far less space.

So what's the downside? well at very low SPL's the suspension is rather

stiff when the PR needs to move like 1mm. So basically you don't get as

much gain from the PR at low volume levels as you would at louder

volumes. But most people aren't listening to music at 70dB and if they

are....the difference wouldn't be percievable thanks to the

fletcher-munson equal loudness curves. The only other downside is a

quality PR is more expensive.

I don't mean to make the PR sacrifices sound worse than they really are

because the limitations of the design are far far far less than that of

ports.

2. No, but you need to modify the end subwoofer size to accomodate for

the extra volume that the port, bracing, and driver takes up.

4. The only side you should double up on is the face with the active

driver, but even that is a bit overkill. You want to add bracing so

that you minimize the area of free vibrating surfaces. Every time you

cut the area in half, you raise the resonant frequency up an octave.

The goal here is to move the resonance up out of the passband of the

woofer (so resonance above 200Hz would be overkill).

So after all that....bored or worn out yet? [] I haven't even touched

on active driver nonlinearities either! But I'll skip that for now, I

had an idea for your enclosure.

7 cubic feet looks real good btw. And it would go real well with two of these PR's:

http://yellow.mynethost.com/~bv126368/shop/catalog/product_info.php?cPath=24&products_id=41&osCsid=ce3c88fb42523a98b356ce0952f8fbe7

It would result in an optimal 20Hz tuning for your cabinet. The downside is it will cost you $140.

And then I would highly recommend going with the Dayton 1000W amp

(which is actually only 500W into 8ohms). You will be excursion limited

to 400W with both your active and passive drivers (yielding 112dB of

output). You'll notice that the dayton 500 and 1000 watt amps have a

slow roll off below 20Hz, which you can model with a high pass

butterworth of order 3 at 18Hz. This just happens to be rather

convenient because it totally controls the cone excursion below the

tuning frequency (providing for much cleaner output).

For the cabinet shape...I would recommend something similar to the

RT-12d. It's an equilateral triangle looking down from the top - active

driver on the front, and put the PR's on the sides. It tucks real nice

into a corner this way too. And then you can just put the amplifier

into the top panel facing up. If you don't like the aesthetics of this

you can always build a "lid" for it.

Or you can just go with a normal rectangular enclosure....active firing

forward and PR's on the sides. amp on the back. Just try to avoid any

two dimensions being the same (as these will amplify any standing

waves).

[Jay481985]

If you were to place the driver outside of a

cabinet on the floor, you would barely hear any sound because the back

wave cancels with the front wave (which is the entire purpose of

building a cabinet in the first place).

Umm I would beg to differ. Have you ever watched any adire audio video

of the tumult outside an enclosure. The problem is the is no spring

action and xmax is done relatively easy.

btw goto realmofexcursion.com to see them

[billyjoe72]

I don't know how to quote in here but....you wrote.

So after all that....bored or worn out yet? [] I haven't even touched on active driver nonlinearities either! But I'll skip that for now, I had an idea for your enclosure.

Nah..no way your boring me. I love learning this stuff. Knowledge is power right? But then again, so is a 1000 watt sub.[]

I will look into designing some kind of plans for that new Klipsch sub. Might be a good challenge.

Good evening all.

About that driver not making noise...I remember about 15 years ago when the car subs were getting big, a gentleman at a retail store showed me that exact thing. The driver was going in and out 2 inches with just a whisper of air noise. Couldn't even hear a beat. Then he slowly dropped it into the cab and BAM! Thumping begins. Nothing outside the cabinet. I think it was a JBL. I can't remember. But I had hair[]

Bill

[Jay481985]

give me an idea of the size of the enclosure, what exact speaker

(size), what thickness of the wood, bracing I can handle or you can.

etc etc ported or pr etc etc you get the point as much info as you can

give me and I can spit out autocad drawings

[ancientdude]

This is ontopic,

is it possible and recommended to use any sub as a PR?

It doesnt have to be specifically designed for it, does it?

[DrWho]

This is ontopic,

is it possible and recommended to use any sub as a PR?

It doesnt have to be specifically designed for it, does it?

short answer, no...

A normal passive radiator does not have any kind of motor or magenet assembly. It is simply a cone connected to a frame with a spider and surround. The lack of a motor allows for much larger excursion possibilities. Also, a normal driver has much too high of a resonant frequency which makes for a very high tuning point...

Umm I would beg to differ. Have you ever watched any adire audio video

of the tumult outside an enclosure. The problem is the is no spring

action and xmax is done relatively easy.

btw goto realmofexcursion.com to see them

I never said the driver doesn't move....it just isn't very loud - even with insane excursion. I was repairing a blown JBL 2226 when I noticed the problem...got her hooked up and running and high frequencies were there, but as I played lower test tones the sound quicly went away. In fact, the response of the driver drops off at 12dB/octave at frequencies where the radius of the driver is a 1/4 wavelength (so around 200Hz on a 15" driver). It was only until I dropped the driver into a cabinet that everything in the room started shaking.

In fact, the reason the response drops off so fast below the tuning point is because the rear wave of the driver passes through the port and does the same cancelation with the front wave - the lack of resonance in the port doesn't reverse the phase of the back wave.

[billyjoe72]

Two things. I like the idea of the style of the rt-12d. Is it designed specifically for a corner placement or do you think it will work anywhere? I'm not real hip on the idea of having the amp on top but cosmetics are not really my main concern. I'll do it if you think it will sound better with this design. Also, cubic feet on a three sided box is throwing me off. Any help on a formula? Keep in mind the amp has Dimensions: 11-15/16" W x 11-15/16" H x 5-1/4" D. I'd have to modifiy the height to add more space on top for it, but at 7 cubic feet I don't think it will be an issue. I'm going to do some more searching on a formula for the area.

toodles

Bill