Fine tuning sonosub design, boring background then exciting Qs at end (1 Viewer)

[Kyle Jones]

I'm about to make sonotube sub project, and I'm just hoping to borrow some peoples ears to get some advice on the final tuning of it. All this sub stuff has just made me realize that I've been out of stereo-land for too long as far as the technical side goes and I seem to have pretty much forgotten everything. I came about the sonotube idea based from the reccomendation from a bud on another forum (I would almost assume he's a member on here somewhere). I trust his ideas, but right now I'm starting to feel guilty for asking him soo many questions, so I'm hoping to ease his burden here.

Quick Background-

Getting married soon, moving into a condo... my options lean towards small enclosures.

I currently run Marantz sr5200 reciever, energy C3 shelf speakers switched that I recently switched to, (energys have excellent sound quality IMHO, but I'm used to having two 6.5" on each main speaker so I find that i'm missing that. I'm starting to lean towards wanting a little bit of extra bass for music now)

The parts-

The amp is the non bass boost 250watt version from PartsExpress.

The proposed enclosure is sonotube.

For the sub... between PPI flat piston 12" I have and JLaudio 10w3v2 (2 ohm coils), the 10" JL looks like it will be my choice. According to real-world from when they were in my car, and according to WinISD. Short-cut to JLs specs on this woofer so you can follow along as well here... *edit- guess I can't post URLs yet. add www and cut and past this jlaudio.com/subwoofers/pdfs/10W3v2_MAN.pdf *


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bla bla bla close to time for those exciting Qs (I say that loosely)

basically with future-wife-imposed size constraints, and what WinISD says, the JL looks like a good compromise for my situation. It still has excellent peak excursion and I already know I like the sound of the sub.

From there... I've now decided on 14" sonotube and I'm going to play around with a 60L ported enclosure (port length was around 24" I think... my papers in the garage now... *sigh*), and I also want to try something around 30L with a sealed enclosure.

I really do prefer tighter bass so the sealed enclosure will be a bit of an experiment. If you put in the specs of the JL into WinISD it comes out with enclosures close to these sizes anyway. The horrible reality of me playing with WinISD is that I truly believe I have forgotten everything.

The phase plot part of WinISD seems useless in this scenario. I don't see how the phases will be a problem for me.

The group delay on the sealed box peaks at 6ms, and 29-30ms for the ported enclosure. To me, this seems really high...Is there any way to bring the delay down on the ported enclosure, or should I even bother? Maybe this will boil down to personal preference, which is why I think I should try both.

What about for the ports, where's good to read about port considerations? Am I fine at the legnth of port it's at? How important is that bell shape on the end of the ports... I can duplicate something with router bit, but does it really need the special acoustic bell mouth like I see on a lot of the DIY sonosubs. I come accross soo many little rules of don't go beyond this volume and don't beyond go this length... I do believe I'm past the length already... how much of a consideration should this be? and what about port velocity... does the mach .09 this configuration comes out to, equate to noticeable in real-world?

Thanks for any suggestions, you can probably see why I felt guilty for bugging my bud about Qs.

 

[Dustin B]

What's your cost on the JL Audio driver and what diameter of port are you planning on?

 

[Kyle Jones]

^

I got them from a large sale in the JL booth just before we were able to buy them at any stores here. After tax it came to something like $250CDN each (talked to another shop around Christmas that wanted $380CDN which almost seems higher than retail). I used them in my car for a while, sold the car to get engaged, now they are sitting around waiting for sonotubes. For the price I paid, and the specs of the sub, they were a decent deal.

Port diameter I was considering was 4"ID

 

[Kyle Jones]

Ok - seeing as most of the sonosub pages are about how to build sonotube as opposed to design considerations, a couple answers to my own questions...

exit and entrance to port bell-mouthed to help deter whistling effects.. therefore my reasoning states I should be able to do this myself with some success.

Few port considerations I have found, length over 20" not recommended (port noise thing?), keep at least a diamater of the pipes distance from any wall. How noticeable it is going slightly outside these parameters in the real world... I don't have experience with so I can't say.

Still not sure if I should try to it set up different ports.

The JL ported box delay btw- is 30ms around 20hz, and is half that by 30hz, 8ms at 40hz, 5ms at 50hz etc. 20 hz isn't so much a concern, but 15ms at 30hz still seems like a fair amount.

JL Sealed is 6ms peak delay around 30hz then starts to drop and meets up with ported box around 55hz.

any ideas if the delay is smoething to be concerned about? the line on the JL ported enclosure seems similar in slope but an average of about about 3ms more delay than a 260L, 20hz ported tempest, or almost on par with 124L,22hz Shiva... if that helps give a comparison seeing as I know there are bound to be a lot of experienced people on here with those subs from Adire.

 

[Aaron Gilbert]

Check out Adire's web site in the technical section, they have some great information on port design. http://www.adireaudio.com
The bell shape, known as a flare, varies in importance. It will help greatly if your port is undersized for the amount of output you require from it. If you aren't passing much air through the port, then flares are not really required. I would not trust the mach number in WinISD as anything but a rudimentary guideline. If you get a bit more advanced program (I like Loudspeaker LAB), you will see that you can actually graph the port frequency response and air speed. The maximum air speed (which I believe is what you get with WinISD) only occurs at the tuning frequency and drops off rather quickly on either side of that. In my case, the port is tuned below probably 95% of the material that my subwoofer plays. So even though I am not using flared ports and they are somewhat undersized, port noise is a non-issue. Your port length should be fine. Port length for a subwoofer is not prone to the same possible problems you could have in a two way full range system. The two ports on my subwoofer are 28" long each. Where the flares can come in handy is if larger or dual ports simply are just too large for your enclosure. One 3" or 4" flared port can do the job of a single 4.5" or 6" port (if I am remembering right) in terms of port noise, yet still retain the shorter length of the 3" or 4".

Good luck with your project!


Aaron Gilbert

 

[Mike Keith]

In my experience, 17m/s is the magic number for Port Air Velocity, keep it below that and you will not have any possible port noise. You could never get enough flare with any Router bit I know of so either buy a flared port or make the diameter large enough to keep the velocity down under 18m/s. The rest is pretty simple, do get too caught up in all the fine details, the Room will play a much bigger role then any of the fine tuning points ever will.

 

[Kyle Jones]

Thank you both for the helpful input. I will make a few different options for myself to see what I like, and then I have another to make for my brother. I'll come back on and see if I can give any constructive feed-back from what I may or may not learn.

We'll see how much I can get done before the amps arrive...

 

[Kyle Jones]

Here's the result of little over 60litre box, 14" tube...

oh crud, I still can't post friggin urls...

as per usual add a www and have at 'er

angelfire.com/ky3/teamswift/sonosteel.html

either way - very very pleased.

 

[ZoranM]

Kyle, nice looking sonosub. The stainless steel must look sharp in person.

I was hoping you might be able to provide some insight in a project I was considering.

I have RF (Rockford Fosgate 1000w class d) amp sitting in the garage from a car I recently sold. Also I have (2) JL W6 10 inch subs sitting in the garage from the same car. I was considering building 2 sonosubs. (one JL for each tube) and using the RF amp to power it. Now I know the ohms for Home audio and car audio are different and can have very "bad things" happen to your HT receiver/amplifier.

But if my HT reciever has a sub out, can't I run the sub out cable to the RF amp without it damaging my receiver or my JL subs?

Or am I just trying to "fit a square into hole made for a circle"?

Also did you find that WinISD provided more help then not? Or would you recommend a different program?

Thanks in Advance for any help or insight you can provide.

cheers,

Zoran

 

[Kyle Jones]

The problem is runningyour DC amp on AC. The RF amp will suck way too much current for your poor little house in comparison to a proper plate amp.

Go to partsexpress.com and peruse what they have there. I'm using their 300-794 (128USD each) which is supposed to be 272watts into 4 ohms. For most of my listening it's at 1/4 level, but for the subcrawl the gain is turned up. As a warning, if you do for some odd reason like the gain up beyond half, you may want to look into the 500watt version... only because with the stereo volume down you'll notice there is background noise from the sub with the gain cranked up. My sub has two 2 ohm coils wired in series for the 4 ohm load.

WinISD works as a fine guideline. The sub seems to have a very flat response when away from the walls as the program suggests (minus effects of the room). I just wasn't impressed with the port noise where the sub is moving air more than anything. If I were to put such a thing in my car where I might occasionally turn it up to these higher levels, I would go with a bigger port or a couple of them.

Keep in mind, I'm no expert, just going by what I've found.

here's a small vid (0.1 meg) of the sub crawling with no sound as my camera doesn't have sound unfortunately.

members.shaw.ca/countach4sale/images/sonosteelcrawl.wmv

 

[ZoranM]

Yeah I figured that about the AC to DC conversion.

I guess I'll check out parts express. (Do you know if they have a Canadian distributor?) I'm in Edmonton so I don't want to get screwed on the shipping and duties.

That's a pretty cool sub crawl you got going there. What were you playing at the time?

Thanks for the suggestions.

Also that Countach is pretty damn sweet.

cheers,

Zoran

 

[Kyle Jones]

As you can probably see in the title, I'm from Calgary, so we are pretty much neighbours. I ordered a couple of them, and after shipping I think it ended up being just over $200CDN or so each. I would assume cheaper than the price of your RF amp. The 250 watt plate amp should be very sufficient for you and the neighbours.

As for the Countach, I hate linking like that, but I don't have much choice right now. It belongs to a friend and he was thinking of selling it. It's been worked over in all the right areas and is second to none... selling price is fair for what's done if anyone happens to be in the market.

The sub crawl was done on a frequency sweep just so I could keep it to a short burst.

 

[ZoranM]

$200 CDN. is definetly not unreasonable, guess I'll have to take a look at that. Thanks for the help!

cheers,

Zoran