subwoofer driver

[burdette]

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]

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]

Isn't this the speaker Gonzo is waiting on?

[burdette]

I think he is waiting on AV15s.

[Dr. Spec]

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

[goingganzo]

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]

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

[Dr. Spec]

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

[burdette]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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.

[Dr. Spec]

I am not familiar with the 5X rule of thumb. Can you explain why?

I do know if you use flared on both ends (which I recommend), the port length needs to be a bit longer to achieve the same tune point. I calc'd it out with flared ends (k=.850) and I'm getting about 23" for two 3" ports and a Fb of 18 Hz.

What are you coming up with?

My SVS is around 5.8 (edit: ft3 - duh) internal volume and I'm thinking the ports have gotta be around 28 inches long......

[burdette]

I read the 5x rule in several places on the net. Can't say exactly where - I've read just about every page I've found and there are a LOT of DIY subwoofer pages... which is nice. No, I can't say why specifically, I think port noise was the general reason.

I'm getting about 21 inches for two 3" ports on WinISD, and I think it calculates assuming no flaring, so I suppose 23" sounds about right to be "a little longer."

I assume you mean ft3 and not liters... I'm coming up with about 5.4ft3 overall... I've got a spreadsheet that adds in driver volume and port volume to the volume calculated for the cabinet (roughly).

I should know tomorrow which driver I'm getting.. either Stryke sends it out or I'll get the Shiva. Then I can finally finalize some of this rather than just play around. It has been fun playing on WinISD with the EBS designs. I'll get much more benefit from lower extension than I will ability to play loud... so it is a good choice. Thanks, again, for the reminder/suggestion. I'm not sure I totally understood the concept of EBS when I abandoned it earlier.

[Dr. Spec]

Yeah, that would be ft3 - I fixed it. It was late, what can I say?

It's easier to cut a port than to stretch it. :-) Go with 23" inches and see what happens.

If you can find a reason for the 5X rule, I'm all ears. I know one thing for sure - Tom V at SVS is a DIY legend, and if he uses 3" ports that are longer than 15", it must be completely OK.

As long as you keep the velocity out of the red zone, I see no reason against it. I'm not an expert though and would still like to see the physics engineering logic behind this supposed rule of thumb.

I like the EBS concept and I'm glad you revisited it. Taking advantage of room gain to fill in that slight sag in the FR before the tune point makes a lot of real world sense. I'd be interested in seeing your FR sweep after you are done. Ron-P built a sonosub - get with him for details on build or visit the tons of DIY sono-tube sites.

[goingganzo]

i thing the 5x rule aplys to rediance. just stuff some extra polly fill around the ports. and you will be fine. if you want to save some cash buy the flaired ports ends and some pvc and make your own.

[Dr. Spec]

Originally posted by goingganzo
i thing the 5x rule aplys to rediance. just stuff some extra polly fill around the ports. and you will be fine. if you want to save some cash buy the flaired ports ends and some pvc and make your own.

What does "rediance" mean?

I agree - custom port length is very easy with thin wall PVC and purchased flared ports - good call.

[goingganzo]

sorry about that it is resonance. aka you get the port resonance near the tume resonance and you have problems. that is what i think. inseead of spending alot for the aero ports. i baught a 4x4in flaired port end and mated it with some thinwall pvc and used culpings to do it. then you paint the port and pvc when you paint the front of the box. or you just paint the port and pvc if you laminate the box.

[Dr. Spec]

Ahh...I get it. All tubes have a natural resonance frequency.

You don't want the tube's natural resonance frequency to be anywhere within the bandpass of the sub. High or lower is fine, though.

I guess the question to be asked is this: How do we calculate the natural resonance frequency of a given length of tube?

Have either of you received shipping tracking numbers yet?

[burdette]

No tracking number yet.. he told me last week he'd get it to me this afternoon or evening. I'm on faith now... I really want that driver and hope it all works out, but I'm already acclimated to the expectation that it ain't gonna happen and that I'll be ordering a Shiva this week. I can only go UP from here.

I've been planning on PVC tubes the entire time. Stryke told me he uses them and simply flares the wood itself with a 3/4 roundover bit. Always looking for a reason to buy another carbide router bit. Parts Express has some flared ends that could be mated to longer tubes.. I'm trying to find out how good the fit is.

Right now, I think I'm sold on two 3" ports, each around 21 inches long.. or the 23" if flared. Dickason's book says go with the largest diameter you can, but a single 6" port is supposed to be 42" long.. I don't think I want to do that.

I agree that if SVS violates the 5x rule, perhaps there isn't much to it, especially considering they also use drivers that move a lot of air. There are a ton of resources on Shiva, but not that much to look at for DIY applications of the AV12.

Doc.. do you have an opinion on just how much I should worry about flared ends? If I use two 3" pvc pipes and flare the wood...?? Also, opinions on having both ports upward firing? I want to use 16" sonotube, and don't want to try to squeeze a port on that baffle. 4" wouldn't fit, anyway.

Thanks.

[Dr. Spec]

Definitely use commercial flares - they increase the effective port area more than simply rounding the edges of the wood will.

I also recommend having both ports fire upwards - opposite the direction of the woofer.

See Ron-P's "There's A New Subwoofer In Town" in Off-Topic for some nice photos of what to expect.

Also go here for how to jam three 3" ports into an 18" tube endcap if you really want to flow some air.

http://www.svsubwoofers.com/subs_pcplus_features.htm

It's interesting - the AV12 looks EXACTLY like the SVS ISD with the cone from the dB12. Check out both drivers and tell me what you think!

[goingganzo]

win isd pro will give you the resonance. i think it is a lenth thing the longer the port the lower the resonance fr. i have read by adding extra fill around the port you can reduce this efect.

[goingganzo]

did you get your av12 shiped? he just got in the av15 and shiped 1/2 of them today. i dident get mine but he will ship them tomarrow he sent out 36 out of the 60

[burdette]

My AV12 should be here tomorrow. I just ordered the 250watt amp from PE, the no-bass-boost model.. on special and no shipping, so I got it to my door for $120.

[Dr. Spec]

Originally posted by burdette
My AV12 should be here tomorrow. I just ordered the 250watt amp from PE, the no-bass-boost model.. on special and no shipping, so I got it to my door for $120.

Excellent news guys! Looking forward to progress reports from both of you.

Gonzo will be first out of the gate, I think. All he has to do is wire up the drivers and button them up in the enclosure. The rest is already done.

Make sure to get out the SPL meter Bryan - I've got a fin on 130 at one meter.

[burdette]

Got a port question for you, Doc. I know I've sortof asked around this before, but the port dilemma is my final hurdle.

WinISD is telling me that if I go 142 liters for an EBS alignment, and tune to 18 Hz, I need two 4" ports, each 38" long. If I go two 3" ports, they have to be 21" long. A single 6" port is too long.

I can find commercial double-flared port kits that max out at 17". If I change my tuning to 19.5Hz, I could use the commerical 3" kits. Drop off is quick... changing that tuning changes the -3dB frequency from 17.3 Hz to about 18Hz.

EDIT: Stryke's website shows an F3 of 16Hz for the same EBS tuned to 18Hz... I'm not getting that at all with WinISD... mine shows -5dB at 16 Hz with an 18Hz tune.??? end of edit

I can find 4" flared ends, but I'd have to connect them to PVC pipe and I can't find references on whether they'll fit (I asked PE, no reply yet). I know gonzo did this, but I don't know if the ends he found are the same ones I've found (PE and Madisound and a few other places on the net).

I know you strongly suggested commercial flared ends. So, what is the solution to all this? Frankly, at this point, I'm tempted to just buy 4" PVC pipe and save the money on kits or ends, round the wood some, and (most likely, I'm assuming), be just fine because I certainly will NOT be after the high SPLs. Those kits are $13 a pop and I have to change my tuning to use them. It seems like two 4" ports could move a lot of air, and I'm really wondering if I need to be so concerned about flaring right now given my usage...? WinISD gives me a mach number of 0.04 for two 4" ports, 38" long.

I really don't have to decide this right now as far as construction schedule, but I need to place another order with PE and I'd like to get everything at once. $8.50 shipping is too much for some port ends that run a buck each.

[Dr. Spec]

You are overlooking the obvious - if you are stuck with a 17" port, simply alter the enclosure size to accomodate for the shorter ports. A 6 ft3 enclosure should do the trick if you are using twin 3" ports x 17" long.

With sonotube, it's as easy as pie - just add some height! Go with an 18" tube diameter to keep the height reasonable - around 42" should do it.

Also, bear in mind SVS uses a single 4" flared port for its CS and PCi subs and the T/S parameters for the AV12 are probably VERY close the SVS ISD. A single 4" port of 17" will get you very close to a 18 Hz tune with your original 5 liter enclosure.

The Parts Express kits are very nice, BTW and should serve you well either way.

Hope this helps!

[goingganzo]

if you go with the 4x4 flaired ends and make your own it mates op nice. you just have to make sure you sit the flair and the pvc all the way down on the culping.
6 cf gives you a 31 in vent for dual 4 in and dont you forget to add a in to the 31 for the flairs.
5.5cf gives 34in

actuley i went out and got some wire and some more bana conectors.

[burdette]

Originally posted by Dr. Spec
You are overlooking the obvious - if you are stuck with a 17" port, simply alter the enclosure size to accomodate for the shorter ports. A 6 ft3 enclosure should do the trick if you are using twin 3" ports x 17" long.

Also, bear in mind SVS uses a single 4" flared port for its CS and PCi subs and the T/S parameters for the AV12 are probably VERY close the SVS ISD. A single 4" port of 17" will get you very close to a 18 Hz tune with your original 5 liter enclosure.

The Parts Express kits are very nice, BTW and should serve you well either way.

Hope this helps!

It does help.. I very much like having my thoughts confirmed by those with more experience. I like to take risks SOMEtimes, but sometimes not.

True enough, a single 17" port will work ... the reason I started looking at multiple ports was due to the mach number I'm getting from WinISD. The single port shows a mach of 0.15, and the number turns red at 0.16 (I think).

If that mach number isn't a concern, then I suppose my question is answered. Increasing size to accomodate two 3" ports only 17" long isn't what I want, so I think I'll go with the single 4".

Thanks, Doc and gonzo.

I'm waiting to hear the FedEx guy come into the office.. he should have a big, 25lb box for me! Got word that my amp shipped yesterday as well, should be here Friday.

[goingganzo]

also i was told to play a 10hz sogonal throgh the subs to break them in. it will move them throgh most of their range and is not audible.

[burdette]

Two things.. first.. my AV12 did indeed arrive today.. in an unassuming plain white box. Opened the box, looked in, and thought "wow" and "cool." Took out the packing and took out the woofer and thought "Holy Shit." In fact, I do believe I actually said "holy shit" out loud.

This thing is a beast... a monster... I am absolutely impressed with the look, feel, build quality... holy shit. Not since I was the first on my block to get a Dolby C cassette deck have I felt this puffed up about a piece of my gear. Anyway.. wanted to pass that along. I can't even imagine being in the imposing presence of gonzo's two fifteen-inchers (I think there might be a good title to a sci-fi porn flick in there somewhere).

Second.. christ I can be such a fucking woman sometimes with worrying. It usually serves me well in that I rarely have buyers' remorse or think "oh I should have...." about a project. But geez.. these ports. I went to Lowe's this evening and they have SUCH a selection of pipe and connectors.. I'm definitely ordering the flared port ends from PE for $1.09 each (in fact I got 3 in case I mess one up) and picking up the rest from Lowe's. I should have less than ten bucks in the port and can make it any length I choose. Thank you for not bitch slapping me during that, my one and only subwoofer project-related panicky moment. I'm feeling much better now.

[goingganzo]

when you cut your pvc make sure it is seated all the way ti the botom if the culping or the lenth will be off. but that wont afect you very much unless you have 2 or more ports. i hope i get my subs someday.

[Frank Z]

Originally posted by burdette
I can't even imagine being in the imposing presence of gonzo's two fifteen-inchers (I think there might be a good title to a sci-fi porn flick in there somewhere).


THAT is a mental image I did not need..THANKS A LOT!!

[goingganzo]

just got my tracking # today and it should arive today. good thing i have most of the day off. i will post some pics as soon as they arive. and if i can find the digital camera.

[Dr. Spec]

Gonzo:

Have you actually assembled your ports yet? The last I saw you just had the flares in the box.

[goingganzo]

it is all done and i got my subs today happy day. did you check out the suround on the thing it is like an inch high. these are massave the 2 subs weigh as much as my old velo did with box. they are so sweet looking too. i dont have a digital camera at hand so i will have to wait till monday to take pics. just amagine my box with 2 sweet subs in it. the ports are easy to do you take you cleaner and put it on bith the flair and culping then add the glew.push in till seated then 1/4 twist. repet steps for thinwall pvc pipe. but it is harder to seat so use extra force. then cut hole in endcap put other flair in then join togher. after you have i side thrigh hole for port.

on my first atempt when i was makeing the ports for my sono tube i got 1 longet than the other caues i didnot seat them very well.