some sub clarifications

[WilZirkle]

I have a Mirage 8" sub now that I would like to replace with something a little bit bigger. So I have been reading about subs for a little over a year and I'm still a little unsure of some things. I've played with WinISD and looked at Unibox, but I don't really understand what I am trying to get from them.

What I want is a sub that will play low, (don't I?). Its main use is for movies (I have Triton mains right now but will probably replace them with Swope 3 ways or Kahns). It will be in a big room that is 1/5 open to the rest of the house. I know I want to use a plate amp and not a separate.

Whenever I look at a sub woofer I look at the Frequency range and look for the lower number. I had for a while thought of getting the Titanic MK III 15" with the dayton 1000 watt plate but then when I looked at the specs it has a frequency range of 19 - 500 Hz. From that I thought I would be missing anything below 19 Hz but from more reading and WinISD I get the impression that it just drops off significantly below that.

I also read the AV Science forum and those guys seem to only believe in building subs that use 4-16 drivers, use external amps, and cost a lot of money.

So I'm not sure what I am asking exactly, I hate to say what do I need, because no one can really answer that. I guess I'm looking for some basic thoughts.

I like the easy button designs http://www.avsforum.com/avs-vb/showthread.php?t=1018171 There is one in google sketch up that uses a 15 inch driver and bash plate amp. It is probably what I would want to build.

Sorry for the ramble, but if it makes sense to anyone else, may I have your thoughts?

Wil

[---k---]

AVS is a bunch of crazy zealots. In my opinion, the information parroted there is beyond overkill. I stopped going there a few years ago.

First, typically I push 15" drivers because the cost of the driver isn't much more than the 12", but will give you 2x the output. So, if you can make the size of the 15" work for you, there is a lot to gain with little lost.

The drivers available for subs have come and gone over the years. Back when I built mine, there were a lot of very long throw, reasonably priced drivers available. Like the old TC drivers and Soundsplinter drivers. More recently, there were the diycable Tempest-X and Shiva-X drivers. These drivers all could take a lot of abuse and produce a lot of output. Unfortunately they have all dissapeared.

The Dayton RS Subs are very nice drivers. Very high sound quality and reasonably priced. They don't have the xmax of some of the other drivers, but can make a lot of boom. A Dayton 15" RS sub would be nice. Probably would be my recommendation. But, I'm not as familiar with the other drivers available.

There is the ported versus sealed debate. If you want low low frequency for movie sound effects, you're probably want a ported sub. it can be done with sealed, but you need a lot more driver, more amp and something to eq it. It gets complicated fast. I would recommend ported. A 300W or 500W plate amp should be good with ported. I like pro amps. A little more expensive, but a lot more power, better power, more durable, and never have EQ built in.

A Tuba horn is another option. I built one for my brother using a Dayton 15" DVC driver. It had tons of output with a 300W plate amp. Not the smoothest sounding, but fantastic for movies. And HUGE in size.

So, pick take a look at a Dayton 15" RS sub using Unibox or WinISD in a ported enclosure. Decide on the biggest box you can live with. Put that in to Unibox. Then you probably want to use a 6" diameter port. Vary the tuning (somewhere between 16hz and 24hz) and box size until you get a nice flat response with a smooth roll off. Finally, look at the port velocity, but not really that important with a super low tuning.

This thread may help you:

http://techtalk.parts-express.com/showthread.php?t=227978

[WilZirkle]

it's like you have ESP ;x( you took that gobeldegook I wrote and made a fantastic response. Thanks. I may...just may start on box building in the next week.

Wil

[---k---]

Always double check other people's models in Unibox.

Feel free to post the graphs and we can ooh and ahhh over them and make sure they look right.

[WilZirkle]

LOL I will. I'm waiting on Neo Dan to rework an easy button box design of his for me.

I've also been playing in sketchup with a design for my next speaker build, which will either be your kahns or the tmww version of the Swope. I still haven't decided, mostly because it't not time to pull the trigger yet.

[fbov]

AVS is a bunch of crazy zealots....

True, but they do have some very nice designs (Easy Button), and it's the place to go for horn subs.

Back when I built mine, there were a lot of very long throw, reasonably priced drivers available. Like the old TC drivers and Soundsplinter drivers. More recently, there were the diycable Tempest-X and Shiva-X drivers. ... Unfortunately they have all disappeared....

So, it's not just me...

The Dayton RS Subs are very nice drivers.

+1 if I were building now... down to a ported box. (mine are all sealed)

Without a lot of experience, you really can't tell from a spec sheet what a driver will do in a box, thus the popularity of simulators. Posting sims for what you plan to build is a good idea.

Don't get tied up in construction details (except for your enjoyment, or spousal approval) because tuned boxes aren't very sensitive. In your simulation, look at port length as you change box tune. You'll see that a small change in tuning frequency results in a large change in port length, meaning that large errors in port length can be tolerated without audible effects. Same for box volume....

That's one reason subs are so popular - they're hard to screw up - plus they give a good bang for the DIY buck!

Have fun,
Frank

[WilZirkle]

Ok I have not hear back from Neo Dan yet but I've been trying to model an easy button in Unibox. I don't really understand it all but I think I am learning. Yea me!

It looks like my driver is going to exceed its xmax. Is this really bad?



and here



Thanks for all the help!

[---k---]

I'm not an expert either, but I play one on the internet... Generally not a good thing to exceed xmax. That is at max power with 500W though. You can iterate the driver power (in the driver input section) to see how much power it actually takes. I probably would play with the model a little more to eliminate exceeding xmax. Try raising the tune a little to like 16hz or 18hz. That should shift that graph over. Also, you can try making the box a little smaller, which will make the roll-off quicker, or make it larger which will start the roll-off quicker but slower.

Nice smooth flat response is good. But here is mine:



I'm not saying this is the best or correct, but the theory is that the room will fill in the bottom end and EQ will fix the rest. If I could have used a bigger box, I would have and it would have made the graph smoother. The rolloff above 60hz is because I clicked the check box that the says something about model the effects of Le. I don't remember.

[WilZirkle]

I changed my driver and tried a smaller box.


At what point do I have to worry about port noise?



Thanks

Wil

[---k---]

Well, upgrading the driver works wonders.

It doesn't look like you have to worry about that driver in that box. You could probably optimize it a little more. I might try and get it a little flater by raising the tune to 14 - 15 hz and playing with the box size.

I'm of the opinion that port noise that low in frequency doesn't matter. Yes, you're going to get port chuffing, but if you're playing something at 10 hz to 20 hz, likely it is a big booming explosion and the port chuffing is tolerable. I wouldn't want that kind of port noise up at higher frequencies.

Also, it says 8 cm port. I'm not sure how you're getting that to work. I would anticipate you needing a 6" - 8" port diameter. At which point you might have trouble getting the length inside. So, check you're port calculations.

If I didn't have to input all the crap into Unibox everytime,

[WilZirkle]

That was with 3 ports but it only shows the diameter of the first I think it was a slot 1" by 6" or something. I played with the port diameter to get the length I needed to work with the box.
I've messes around with the Titan 15" too but now I'm back to the Ref HF 15 again, feeding it only 250 watts.
When I plug this stuff into WinISD Alpha my curves are not nearly so smooth.

[WilZirkle]

Unibox for Dayton 15" HF using 250 watt plate amp. Three ports 2.25*8.5 each.



Its based on the Easy button designs but I did my own modeling in Unibox. The tuning is a mix of trying to get the port size to work at the right length for my box and keeping the cone excursion down. I have no idea if I did anything right. Box will be around 27.75"H x 28.5"W x 28.5"D

Wil

[---k---]

Where is Thomas when you need him?

In general, I like the look of that. I'm not crazy about three 2.25" ports. I don't know why... I just always see big ports on big subs. You're going to be getting a lot of output out of those ports. Length is a problem with bigger diameter, but that can be worked around with an elbow if needed. Stay off the wall an equal distance as the port diameter... some say diameter/2. My gut says use no less than a 4" dia port. If it is getting too long, I wouldn't be scared to raise the tune to 14 or 15hz.

I wish PE would put out some standard designs guides for these drivers like Kevin at DIY cable did.

[WilZirkle]

ordered my parts from PE, decided to go with the Bash 300 plate amp because the dayton 250 was out of stock till the 20th.

[BeerParty]

Are you planning to build the box like the Easy Button - that is, with a full width slot port wrapped around the outside of the sub? The reason I ask is I created a spreadsheet that allowed me to design the box I used for the Shiva-X2 "Easy Button Mini".

If you post your desired box volume, size and tuning, I should be able to plug those numbers into my spreadsheet and generate some dimensions for you.

[WilZirkle]

Chris,

Yeah that's what I am doing. I had looked at your sketch up a few times and was going to ask for the model to start with but I think I got a lot figured out in sketchup that is making is easier to use. I used a spread sheet of my own and tweaked it back and forth with UniBox till my dimensions matched my what I needed. I would be interested in what you come up with though.

Volume is 286.708 liters. Size is around 2.25'x2.25'x2.25' and the tuning I came up with is 13Hz

Wil

[BeerParty]

Posting from my spreadsheet didn't format very well, but here you go:

Desired Tuning Frequency 13 Hertz

Material Thickness 0.75 inches
Port Height 1.25 inches
Port Width (individual) 8.00 inches
Number of Ports 3.00
Port Length (minimum) 60.00 inches

Box Width (external) 27.00 inches
Box Width (internal) 25.50 inches
Box Height (external) 27.00 inches
Box Height (internal) 25.50 inches
Box Depth (external) 27.00 inches
Box Depth (internal) 24.75 inches

Port Length Bottom Panel 25.00 inches
Port Length Rear Panel 23.00 inches
Port Length Top Panel 12.00 inches
Length Top Panel Remaining 11.50 inches

internal box (ignoring bracing)
Width 25.50 inches
Height 21.50 inches
Depth 22.75 inches
Volume 7.22 feet^3 (204.39 liters)

[BeerParty]

And a quick sketch-up of the layout:



3/4" material, double front baffle, 27" cube.

[WilZirkle]

I been messing with sketchup and I am getting better with it. I drew this over the past few days and the dimensions are bigger than I thought they would be.

[Hdale85]

If you can at all possible notch the corner of the port there so that there is less resistance for air flow. It's not needed exactly, but it does help. You just put it on an angle instead of a straight edge all the way to the corner, also you can cut a triangular piece to fit in the corner it self to sort of round out the whole corner. This will cut down on resistance quite a bit. Just a thought.

[WilZirkle]

Hdale,

I will use a large round over on those I just don't know how to do it in sketchup.

Wil

[WilZirkle]

Ok this is what I am planning to start building.



Its 2' by 2' by 3' The ports are open on the bottom, on top what looks like ports are just shallow cuts to make the sub look balanced.

Wil

[WilZirkle]

Not much progress over the weekend. I got two sheets of MDF and made some cuts. Nothing worth taking a picture of yet.

[JonMarsh]

Now, you've got to be careful here, or you're going to turn into another digital designer like me- great stuff on the LCD, but not enough sawdust being generated!

[mackintire]

I should forewarn you, I've talked to Neo Dan about the easy button cabinet. In reality it tunes lower than what WinISD states it should. Also the long port with those 90 degree angles tends to attenuate the higher port harmonics nicely.

If I remember the original easy button showed 17hz at -3db simulated and measured closer to 13hz at -3db. I think some of the more complex modeling software can calculated this box's port freq more accurately, but WinISD gets you in the ballpark

That was with a TC sounds LMS sub.

[WilZirkle]

I have a little progress. Almost everything is cut to size and I have put the inner cube together. Pictures are from my cell phone.





Those are 1.25" round overs on the port corners.

Then back side




Wil

[WilZirkle]

Got my baffle cut over the weekend



Looks like I have some sanding to look forward too



Its so close to fitting!! Grrr.



The two layers are clamped while the glue dries




Wil

[WilZirkle]

Boom Boom :-)

[BeerParty]

Boom Boom :-)

I take it from the smiley face that you have sound?

[WilZirkle]

Chris, I do, but the box is still just MDF. I'm floored with how much it puts out. My kids are impressed too.

[WilZirkle]

I have a confession. Over a year later and this thing is still just bare MDF, but it sounds so good.

[BobEllis]

That's a battle I fight a lot. Enjoying my speakers too much to pull them apart and finish them.