subwoofer driver

burdette · February 2003

Oh happy day (oh happy day) Oh happy DAY (oh happy day)...

I ordered a subwoofer driver today. I've been researching and reviewing drivers for a couple of months, bouncing back and forth on what to get, how much to spend.

Decided on the Stryke AV12.. got a good deal on - from what I've read and been told - a great driver.

12", 23mm Xmas, should have -3dB at 21 Hz in an box less than 3ft3.

Ahhh... I love the smell of MDF dust in the morning...

Ron-P · February 2003

Ahhh... I love the smell of MDF dust in the morning...

It also taste's good in your beer. Looking forward to pics of the project.

Peace Out~:D

scottvamp · February 2003

Isn't this the speaker Gonzo is waiting on?

burdette · February 2003

I think he is waiting on AV15s.

Dr. Spec · February 2003

Nice! What are you going to mount it in? Tube or box?

goingganzo · February 2003

the 12 was bult first. the 15 os being bult seccond. and was afected by the strike on east coast and ces. the cones got stuck on the dock and the voice coil were on back order. but all parts are at the speaker bulders. just have to wait a little longer. i have seen pics of the av12 and it looks sweet.

goingganzo · February 2003

here are some pics of the av 15
[IMG]http://D:\MVC-015F.jpeg[/IMG]

Dr. Spec · February 2003

So you have the AV15 now Bryan??!?! If so, AWESOME!

burdette · February 2003

I'm going with a box. Actually, it will be a bit trapazoidal.. like a pyramid without the pointy top.. about 15" square on the top and about 19" square on the bottom, 23" high without feet. Driver will be front-firing. I think I've settled any problems that were pushing me towards a sonosub. Not even sure I'll have to buy any construction materials.. I have more than a half sheet of 5/8" particle board, and a half sheet of 1/2" Baltic Birch plywood (this stuff has something like 8-9 layers in that half inch).

My only real design issue is the placement of the port. I can put it downfiring and have a straight tube, or I can put in front-firing (under the woofer on the baffle) and use a right-angle pipe. I have to have about 21 inches of length using a 4" port to tune to about 20-21 Hz.

Dr. Spec · February 2003

If you are going with a full power amp (500W) I think you will be a bit underported at a single 4" vent.

How hard will you be pushing this woofer. It has a xMax of 23 mm and can move a great deal of air at full power. You may get port noise and power compression at really high volumes.

Might want to at least consider two 3" ports unless you will be pretty sedate on playback.

What is the internal volume of the enclosure with polyfill, woofer, and vents inlcuded?

Make sure to brace that sucker really well inside - flexing cabinets are the bane of good sounding subs.

My SVS employs a very similar driver and it uses three 3" ports and a 525W amp, FWIW.

Doc

goingganzo · February 2003

get unibox it will help you sim up a good box and get you to tune the box and the port lenth. i am going with 2 4 in flaired ports for each of my 2 15. i expect them any time between now and my birthday.
march 4th
send presents to

i figure i will have 43 m/s port speed

burdette · February 2003

Actually, I was interested in multiple ports, but haven't found two good online calculators that give me corroborating results to help me do the design. Any help would be appreciated.... nudge nudge hint hint

I'll have the 250W amp from PE, no bass boost. This thing won't be pushed hard at all except the few times I'm alone in the house sans wife and children.. which ain't often. And even then, we aren't talking LOUD.

Internal volume of the box alone should be about 3.3-3.5 ft3. The volume of the driver is 2.33L, I'll have to subtract the port(s). I've been using 95 liters in my calculations.

Dr. Spec · February 2003

How much polyfill will you be using? From a design standpoint, it actually increases the apparent volume of the enclosure, despite actually displacing physical volume in the box. It won't be much, but we should count it just to be precise.

If you won't be playing LOUD, you might want to consider an even lower tune (maybe 17-18 Hz), if we can fit the ports inside.

Gonzo - is there a link to this "unibox" or can you put it on your website for a freeware download?

Edit:

Any reason you didn't want to go with a sonotube? It's so easy and cheap to build and they can accept really long vents that don't require bracing for support. The internal geometry is perfect for a subwoofer - equally strong in all directions, won't support standing waves, and incapable of flexing.

Hell, if aesthetics are the problem, build a high grade square wooden box around it and pretend it's a coffin in the corner.

burdette · February 2003

I have as yet failed to find a retailer for a tube. Lowe's here goes to 6".. that's it. That frustration led me to think box. Edit: I can get 12' lengths. I'll have to cut it.. and before that, get the dang thang home. You've got me thinking, again, about how easy a sonosub would be.

It was suggested to me to use two tubes, like a 16" and 18", put the 16 inside the 18, and fill the space with expanding foam. Said to make a much more dead tube. I'd like to use a 14" tube, 48" tall, if I could find it.. maybe inside a 16". That would give me a nice small footprint and plenty of internal volume. I won't do that, however, having to buy 12' lengths...

Only other thing... I just can't seem to get comfy with a downward firing woofer... for some reason I can't shake the feeling that I'm going to damage it SOMEHOW... kick it.. or my two year old will figure out SOMETHING. Also, honestly, this driver is pretty cool looking. I'd hate to hide it away. Ya, I know, that feeling will pass.. but after just laying down the dough, and not having even seen the dang thing yet, I can't imagine hiding it!

I'll look a little more for a tube.. that really was my first choice for construction (except for hiding the driver)... especially if I can go no larger than 16".

Thanks.
Edit...I realize that as you go larger in diameter, a port has to get longer. What happens to length if you go to 2 ports that are smaller? Say, a single 4" to double 3"?? I tried to do that calculation online, but kept getting a LONGER length for the double threes.. unless I'm supposed to cut the calculated length in half???

Dr. Spec · February 2003

http://members.tripod.com/~terryctheater/shivaphotoalbum/page12.html

http://www.concreteacc.com/sonotube.asp

http://www.usmix.com/Techsheets/Distributor/sonotube/

http://www.glaciernw.com/product.asp?p_id=295&d_id=251

Some stuff to check out.

BTW, I'm getting a 25" port length for two 3" round ports in a 3.5 ft3 enclosure and a 20 Hz tune point. And yes, the ports get longer as the numbe of them increases and no, you don't chop them in half.

A larger enclosure will increase the efficiency and decrease the tube length.

goingganzo · February 2003

http://www.linearteam.dk/
http://koti.mbnet.fi/jahonen/WinISDpro/
go to the first link down load win isd beta install it. dont use it
go to seccond link get win isd alpha
extract file then run alpha.
http://members.tripod.com/~terryctheater/shivaphotoalbum/page12.html

link to all sort of stuff like sweeps and others diy pages.

goingganzo · February 2003

if you do a 18 sono 3 feet high you can do 2 4 in flaired ports tuned to 20 hz the ports would be 30 in long. and also you can make the ports for very cheap. less than 5 bucks each.

burdette · February 2003

Thanks for the replies. I actually have WinISD already... it was one that was giving me a longer port for a smaller pipe if you use more than one. I've also written the formulas into Excel.

I don't want to go over 16", or I lose the advantage of small footprint. I want to go up, not out. I'd do 14" but that seems a little tight for a 12" driver.

I'd go multiple ports to decrease the airspeed, is that correct?

I have one question regarding "tuning" the box by changing the volume... I thought a couple of sources I read said.. that as you tune lower and lower beyond "flat", you get a nasty bump in response just before rolloff begins. They had curves showing as much.

I'll check back in for advice once I actually have the sonotube. I can't rush this. This is *supposed* to be a birthday present, and my birthday is still over a month away. But after working on and finishing that pair of 8" 3-ways, I've got the bug to keep going.. must keep building ... must keep measuring and cutting and

Seriously though, what the hell am I supposed to do with 7-8 feet of leftover Sonotube?? I thought about cutting it into a couple of pieces and letting my kids play with them.. but then I'll just be tripping over and cursing them nightly.

goingganzo · February 2003

the bigger the box you can get a bump but if you lower the tuneing you get rid of it but you lose some uper bass. it is a gentle slope vs a flat line with a roll off.

when i got mine i baught it by lenth but i payed more per foot than if i just got the whole lenth.

if you do a clone of the svs 1646cs you would get about the same output. the drivers are similar but a little different.

Dr. Spec · February 2003

Originally posted by burdette
I'd go multiple ports to decrease the airspeed, is that correct?

I have one question regarding "tuning" the box by changing the volume... I thought a couple of sources I read said.. that as you tune lower and lower beyond "flat", you get a nasty bump in response just before rolloff begins. They had curves showing as much.

Seriously though, what the hell am I supposed to do with 7-8 feet of leftover Sonotube?? I thought about cutting it into a couple of pieces and letting my kids play with them.. but then I'll just be tripping over and cursing them nightly.

Multiple ports obviously reduce air speed, but they also simply allow more air to pass without restriction at a given pressure differential. Try breathing through one nostril, then two, then your mouth - you get the idea.

The t/s parameters of the driver will tell you what vented alignment works best. The enclosure and the venting work in relationship with each other - if you alter one, you must also alter the other to compensate.

The larger the enclosure, the more efficient it becomes at allowing low bass to be produced with no roll-off, and the less vent length you need for tuning.

The slight rise you referred to is a function of the Qts of the driver and the enclosure alignment. The AV12 would probably work best in a vented alignment, since the Qts is .366.

To get the approximate ideal enclosure volume try this:

Vas = Equivalent air compliance (litres)
Qts = total Q of the driver at its resonant frequency
Fs = resonance frequency of the driver (Hz)
Dv = internal diameter of port (cm)

then,

Vb = 20*Qts^3.3*Vas
Fb = (Vas/Vb)^0.31*Fs
F3 = (Vas/Vb)^0.44*Fs
dBpeak = 20*LOG(Qts*(Vas/Vb)^0.3/0.4)

where,

Vb = net box volume (litres)
Fb = box resonant frequency (Hz)
F3 = -3dB frequency (Hz)
dBpeak = maximum peak or dip in system response

Note: This particular alignment should give you a fairly flat response (without the peak you were referring to) within the system's passband with the .366 Qts value of the AV12.

This alignment gives you a Vb of about 64 liters with virtually no hump before roll-off and an F3 of about 24 Hz. Of course you can go with a larger enclosure and drop the F3 considerably and alter the port length accordingly, and still have a very reasonable dB peak.

In fact, going with an EBS (extended bass shelf) size enclosure will probably be your best bet. Stryke recommends a 142 liter EBS vented enclosure as a suggested alignment. From my design references:

EBS systems are ported systems that are usually characterized as follows:

The volume of the box is larger (sometimes significantly larger) than that of a maximally flat ported system using the same driver.

The tuning frequency of the enclosure is at or close to Fs, the driver's resonance frequency

The power handling of the EBS is lower in the midbass frequencies when compared to the maximally flat systems.
However, the power handling at lower frequencies is usually better.

As with the standard ported systems, almost any driver can be used. However, the best results will be obtained with drivers of Qts <0.35.

One of the main reasons given for using an EBS system instead of the usual "maximally-flat" systems is to take advantage of "room-gain", the increase the bass response at lower frequencies, starting at around 1dB at 30 Hz and increasing to 9dB at 20 Hz, that you get in most rooms. This "room-gain" can tend to produce a boomy response with speakers designed to maximally flat to frequencies below 30 Hz.

To design an EBS system, model the response of a system using your driver, where the box size is 160% to 180% the volume suggested for a maximally flat response. Then, set the tuning frequency to near Fs for the driver.

If the cabinet is too large, the frequency response curve will be peaked below the shelf. Too small, and the shelf will be attenuated. Adjust the cabinet size to suit.

If the tuning frequency is too low, the shelf will roll off prematurely. Too high and the response peaks at the bottom of the shelf and the premature rolloff occurs again. Adjust the tuning frequency accordingly.

When tuned just right, the shelf level is not too low, and reasonably extended, with a smooth low end rolloff. Note also that if the box is very big compared to what's called for in a maximally flat alignment, there's a loss in midrange efficiency that may be more important than the small increase in low frequency output.

With Stryke's suggested alignment in a 142 L enclosure, two 3" flared vents 21" long will give you a tune of about 18 Hz.

Hope this helps. Remember, what curve looks the best in an anechoic chamber is not always what works the best in your room. My SVS has about 8 dB or room gain at 25 Hz and then trails back off to an F3 of about 17 Hz. With one port plugged, the FR is flat to 11 Hz - again a fortuitous combination of room gain and and EBS type alignment working well together.

burdette · February 2003

Thanks for the info, Doc. An EBS alignment is simply too large of a box - I determined that pretty early. Also, if you follow the Qts recommendation of <0.35 (I saw that somewhere, too), then the AV12 actually fails that criterion. I suppose it would be easier to do with a sonosub... 5ft3 is about 43" of a 16" tube.

I, too, calculate a Vb of ~64L for an optimally flat response. That is, nicely, a small box. I've played around with increasing the box size ... as I mentioned before, 99L is what I've been using lately. Gives me both an F3 and Fb of around 20-21 Hz. You recommended going ahead and tuning a little lower since I'm not concerned with maximizing SPL... I've done a little modeling to get F3 to around 18Hz... easily done (in terms of volume) with a tube.

Still trying to find tube that isn't 12' long... that would greatly ease my ability to do a tube. I know I can successfully construct the box.. but as you reiterated, tubes are pretty easy.

Thanks again for the info. Most likely I'll be hitting you up for more advice once the driver is in hand and the dust is ready to fly.
Stryke hasn't shipped my driver yet.. I'm a little irritated given that I ordered it last Friday.

Dr. Spec · February 2003

Just remember, Styke recommends an EBS alignment for a vented enclosure, and a PR alignment if you go with a smaller enclosure.

Honestly, I think you would be fine at 95-100 liters vented. Mess around with the enclosure size and port length and when you think you've nailed it, check with Styke before you break out the saw.

As for the sono-tube being too long, I think the solution is obvious - build two subs enclosures and add another driver down the road!

burdette · February 2003

This all may be for nothing.. and I'll give you a heads up too, gonzo. I'm not sure there is going to be a Stryke Audio from which to purchase. The events of the past week lead me to believe that Stryke has just about struck out in the business world. One of the reasons he gave me for not shipping my driver today was that he was so busy, including an appointment with a BK lawyer.

We'll see... if so, I guess I'll be "stuck" with a Shiva. The good news is there is a plethora of designs to study. In the big picture.. service after the sale and such, this development may be better than I realize now. But.. he said he'd ship on Monday, and I'll give him until then.

Dr. Spec · February 2003

This kinda sucks. What is a BK lawyer? I wonder if the "shipping dock strike" delay really was - or was it a cover for something else?

Did you get your AV15's Gonzo?

goingganzo · February 2003

not yet. but they should be shiping soon. stryke is a very small company. i put them on my credit card. if i get the shaft i will report them to my credit card company as a fraud and get my money back. my mom is a bamker. she has taught me well. i allways use my credit card on line. you get the best protecton.

and i can allways get the Tumult drop it in and plug 1 of the holes. then add a seccond later when i can get a amp to do them justice.

goingganzo · February 2003

just talked to my mother. and said what you sait and she said that he is proabley just squareing away his loans or sothing. he was proabley getting a loan or sothing. or consoldateing a loan. i would try him tomarrow. he proabley made a apointment at the bank. also i would order on the website. you can still get the pre order price. i think it is aginst the law to make you pay more than the avertised price. over at the htf everyone that has the av12 say they kick a$$

burdette · February 2003

BK is bankruptcy. He didn't ship last week because UPS canceled his account. He hasn't shipped yet because his new FedEx account doesn't start until Monday. He told me he had an appointment with his bankruptcy lawyer. Thems just the facts. I'm not trying to imply any shady dealings on Stryke's part. He told me today (in an email) he was sorry he hadn't shipped and that he'd credited my card for the price. I replied that I didn't want a credit, I wanted the driver, and that Monday was fine. I told him delays are fine if he just communicates what is happening.. but when I'm told one thing and it doesn't happen, I get grumpy. Honestly, I want that driver... I hope all is fine and he ships as he says. I noticed the Acoutic-Visions show the AV12 and AV15 as due in mid-March.

I've already formulated my back-up plan.. the Shiva for $125 shipped... 5ft3 EBS tube, flat to about 16hz. If it comes to that, the moment the Shiva arrives in the mail, I'll forget about this.

I wish Stryke luck.. I'm *trying* to do my part.

Dr. Spec · February 2003

If he doesn't ship, go with the Shiva!

Regardless of driver, it seems as if you are leaning toward an EBS tube anyway?

You can get sono-tube from any construction company in the area on the cheap. They throw the extra length stuff out all the time.

I really like your idea of a concrete liner between a 14 and a 16 - man that would be acoustically dead for sure. It might be impractical and too heavy though.

The enclosure tubing SVS uses is a proprietary laminate that is much stronger, thicker and denser than sono-tube. It actually gets turned to size on a CNC lathe to extremely close tolerances. It is completely acoustically dead and has survived being tossed off the top of the R&D facility (don't ask me how I know this). DIY'ers have begged them to buy it, but for obvious reasons they steadfastly refuse to sell it.

goingganzo · February 2003

thanks i thought the bk was bank dont know why. actuley fed ex is actuley cheaper to ship with using large and heavy packages. thanks for the update i was told i

"Here's the newest update. The ship with the cones on it arrived to the docks in LA on Feb 3. I emailed Thilo yesterday and received an email back from him. He said a shipment arrived to TC Sounds late friday. The cones should be in that shipment, but he has not been able to verify that for sure. If the cones are in there, drivers will be made in the next 2 days and shipped to me. I'll be prepared for them to arrive and have labels ready to go to ship them out so I can just stick them on and get them back out the same day. I'll keep everyone updated when they are on the way to me." so the friday would have been the 14

my bass is kind of weak right now i took out the ct120 to fix the hole in the wall when removed and to put the amp in the cabinet.

dr spec i have a queston for you. do you think i should put the svs bass box by the recever at the begening of the sub cabble or at the end near the amp. the run is about 40 feet. i have it at the end but if i put it at the begening i will get less ampflied distorshon from the run of cabble.

thanks

burdette · February 2003

I'm leaning towards the EBS because my goal is solid deep bass, NOT high SPL. If I ever have the need for higher SPL, I'll redesign an enclosure or build another sub.

I started with EBS, but went away from it when I focused on the AV12 and could use a much smaller box. I had a couple of box ideas which were great considering the smaller volume needed. But, if I go with the Shiva (and it's need for more volume) I'm back with a tube.. and given I have the same footprint regardless of height, I might as well go the extra foot or so (on a 16" tube) to get the 5+ft3 I need.

Fortunately, Adire provides their EBS alignment so I'm mostly just confirming their numbers. However, one thing that bothers me is port length. They recommend a single 4" port that is 12" long, flared on both ends. They recommend a 17" long port if you don't have flared ends. That 17" agrees with what I've calculated independently. But.. WinISD is telling me that the single 4" port produces a mach of 0.14, which is pretty damn close to the red zone (0.16). But going to two 4" ports forces the length to 27"... yet multiple sources say never go longer than 5x diameter, which would stick me at 20". I run into that "5x" rule of thumb with the AV12 also.

What is the best compromise? Obviously Adire isn't concerned about port noise from the single port. Two 3" ports, 14" long give a mach of 0.06. the same as a 27" long single 6" port.

Either way, I feel pretty comfy. I'd like to have the AV12, and hope it works out. If not, I think the Shiva will work fine, and at $125 to my door, can't complain about that.

Edit: I just received an email from Stryke, and called and talked to him on the phone. He says this thing IS going out on Monday... so I'm hopeful. If I don't have a tracking number in hand by Tuesday a.m., then Shiva it is.

goingganzo · February 2003

just got word that the av15 will be being ship out next week he will get them on monday. happy day is here soon. i will be getting much more for my b-day now lol.

subwoofer driver

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