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"Need Major Help On DIY Sub"

post #1 of 82
12/28/12 at 3:40pm
Thread Starter 
I decided on building my own dual 15 in. ported subs. This will be the first build I've ever done. I need a lot of help and advice from those of you who have done this before. I think I settled on a driver. It's a MCM 15in. pro loudspeaker rated at 98db which is good right?

Here's the link to the driver - http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-2983-/55-2983

I think the max box I can build is 18w x 24h x 20d. Does that sound big enough? also I wanted to go with a dual front ported design under the driver, maybe dual 4in. ports?

Please give me some advice and help if you can because I'm stuck in a rut right now.

Thanks, Jack
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post #2 of 82
12/28/12 at 3:48pm
Is this for ht? I can't model it right now but it looks like more of a midbass type of woofer.
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post #3 of 82
12/28/12 at 4:08pm
pretty low xmax, You probably will want more excursion. With those dimensions you are much better off going sealed, ported needs a bigger box.
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post #4 of 82
12/28/12 at 4:10pm
Yep, that is a PA driver.
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post #5 of 82
12/28/12 at 4:43pm
Thread Starter 
yea its for ht use. what if i uped the box to 20x24x22? Would that make a difference. The reviews said that it is better used as a subwoofer for pa. Any other driver recommendations around $150 or under?
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post #6 of 82
12/28/12 at 5:25pm
What amp are you going to use?
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post #7 of 82
12/28/12 at 6:00pm
Dayton DVC's are only $120 and they are probably close to the best in that price range, someone could argue with me if they want I don't mind :P and they are the go to sub for f20's and THT's

Add 20 bucks to that budget and you can get a 15" dayton hf (which can you give you cleaner results with an f20 compared to the DVC). I've also had the HF in a 24" cube ported to 18 hz and it kicked. It was no f20 but it also wasn't a slouch below 30hz. Can't say that about a $500 best buy subwoofer.
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post #8 of 82
12/28/12 at 6:41pm
Thread Starter 
Brian-
A crest audio ca-6 or some sort of crown amp. My uncle has the fa series of crest amps and recommended the ca for subs. What would you recommend??

DooDoo-
How do those compare to the MCM sub I mentioned above. It is 8 ohm. and has a sensitivity of 98db. Also could I build a 20x24x22 box for a 15in. and tune it to 20hz.? If so what port diameter and what length. I'm hoping to run dual ports to have a symmetrical look.

Thanks for your help guys!
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post #9 of 82
12/28/12 at 6:53pm
Did you say you want to build two subs?

With that amp you could do two of the Dayton HF 15's in sealed boxes. You would get 500 watts to each driver. Would be a good setup.

If your only doing one sub I would spend a little more and get the Dayton HO18. You would bridge the amp and get 1200 watts to the driver.

Each of these would require about a 4-4.5ft^ cabinet.
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post #10 of 82
12/28/12 at 6:55pm
the sub you seem focused on doesn't even play at 20hz.


Operating Bandwidth: 30Hz ~ 2.5KHz - it's a pa speaker and not a very good one either.


The guys chiming in on the daytons are totally right. a 15 dvc or even stretching it to the new 18 would be worlds better.
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post #11 of 82
12/28/12 at 10:03pm
Quote:
Originally Posted by studioholic55 View Post

Brian-
A crest audio ca-6 or some sort of crown amp. My uncle has the fa series of crest amps and recommended the ca for subs. What would you recommend??
DooDoo-
How do those compare to the MCM sub I mentioned above. It is 8 ohm. and has a sensitivity of 98db. Also could I build a 20x24x22 box for a 15in. and tune it to 20hz.? If so what port diameter and what length. I'm hoping to run dual ports to have a symmetrical look.
Thanks for your help guys!

Sure you could put it in a box tuned to 20hz, but that woofer's going to have a poor response, and when you feed it that much power its going to bottom out. You also need a high pass filter if you plan on building a ported sub.

A 20x24x22 box built with 3/4" material would need a pair of 3" x 19" ports for a 20hz tune. This driver will work perfectly in that box

http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-469

$150 for the next couple days.

I think your problem is you're caught up on sensitivity... That doesnt apply to the sub-bass range.
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post #12 of 82
12/29/12 at 5:44am
Quote:
Originally Posted by studioholic55 View Post

Please give me some advice and help if you can because I'm stuck in a rut right now.
Well, you can muddle through all of this, and in about three or four months you might be able to figure out how to successfully design your own cab from scratch:
http://techtalk.parts-express.com/showthread.php?219617-The-Speaker-Building-Bible

But if you want to be assured of a successful build in a far shorter time frame build an existing design.
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post #13 of 82
12/29/12 at 6:28am
Easy choice here, THT or F-20! If too big then you don't want bass! Sealed to me is better for their size and extension but you need more money to equal the spl.
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post #14 of 82
12/29/12 at 12:36pm
Thread Starter 
Jay-
That was my biggest question about subs. There sensitivity. If I built a box that size with 3/4in. birch and with the Dayton driver could I use 2 4in. 17in. long ports? I'm very confused when I comes to ports.

I'm definitely on a budget and right now I'm running dual 8in. sealed subs. frown.gif Anything would be an upgrade. What do you guys recommend or use for amps on your subs?
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post #15 of 82
12/29/12 at 6:09pm
What's your budget? That would help to steer you in the right direction. You have great people helping you. smile.gif
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post #16 of 82
12/29/12 at 6:34pm
Quote:
Originally Posted by studioholic55 View Post

Jay-
That was my biggest question about subs. There sensitivity. If I built a box that size with 3/4in. birch and with the Dayton driver could I use 2 4in. 17in. long ports? I'm very confused when I comes to ports.
I'm definitely on a budget and right now I'm running dual 8in. sealed subs. frown.gif Anything would be an upgrade. What do you guys recommend or use for amps on your subs?

A pair of 4x17 ports in the above box size will tune you to 27.5 hz. You would need 4" ports closer to 40" long to tune @ 20hz... There isnt really anything wrong with the higher tune if output is more important then extension. You could build a pair of those RS15HO subs with dual 4" ports and power them with an EP4000 for $270, giving you about 650 watts per channel. The amp has a selectable 30hz high pass filter, which when activated would give the above sub a ruler flat frequency response and completely protect the driver.

http://www.musiciansfriend.com/pro-audio/behringer-ep4000-europower-power-amp?src=3WWRWXGP

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post #17 of 82
12/29/12 at 6:57pm
Thread Starter 
Whats the rule of thumb on ports? Do bigger diameter ports increase extension or decrease it? I could go with 6in. ports to i guess. My budget is under $200 for the driver, hopefully cheaper because I hope to build 2. I'm planning on starting with one and building the second after. My uncle is trying to see if he can pick me up a EV p1250 for cheap. The behringer is a good option too. I'm not to concerned about extension. I want it to be loud and clean for movies and music but this isn't in a dedicated ht room. It's in a basement with unfinished cement walls still in some portions. I would just like to get my money's worth.

I truly appreciate all of you guys's help and really respect your opinion. Thanks:)
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post #18 of 82
12/29/12 at 7:16pm
Larger diameter means the port has to be a lot longer for the same tune as a smaller diameter. The 4" ports are twice as long as the 3" ports for a 20hz tune in your given box size. A pair of 6" ports wouldnt even work. A very large cabinet allows ports to be smaller, but you already stated your limit for cabinet size. The diameter and the length in a given volume determine the tune.

It sounds like the sub I modeled for you in post #16 would work very well for your needs. I'm not familiar with that EV amp, but it would need a 30hz HPF to work like the EP4000 in the above design.
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post #19 of 82
12/29/12 at 7:39pm
Thread Starter 
Ok, I think that design should work for me too. Will I be missing something by not hitting down to 20hz or is 27 "good enough" for most? Also what if I had dual 3in. ports instead would that make a good difference?? Thanks for the help Jay.
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post #20 of 82
12/29/12 at 8:07pm
Lowering your tune to 20hz means you either need to add an EQ with a HPF, or use a plate amp, which will have a built in filter around 20hz. The smaller ports increase your chances of hearing port noise with high output, but the pair of 3" should be fine if you use a 500 watt plate amp.

If you're not chasing ULF then 27hz will be fine. That's the thing about DIY, you get to build what works for you.
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post #21 of 82
12/29/12 at 8:18pm
Thread Starter 
I'm planning on buying a dbx-120 sub-harmonic. Would that help get me closer to 20hz.? Also If I go with the planned 4in. ports can I buy the Precision Port model and leave it at the standard length that it comes at(being 17in. i believe)?
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post #22 of 82
12/29/12 at 8:31pm
That DBX120 doesnt look like something that should be used, and isnt a HPF. Something like this ART 355, while limited for sub duty, would give you true eq bands, and a completely adjustable HPF

http://www.amazon.com/ART-355-Dual-Channel-31-Band/dp/B0002E53WY/ref=pd_cp_MI_0

Yes, on the 4" ports at the full 17" length if you want a 27hz tune. If you want a 20hz tune you can do the same thing with a pair of 3" precision ports.
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post #23 of 82
12/29/12 at 8:53pm
When you lower the diameter you increase port noise so you may not like that. You won't really know what you're missing until you hear a setup that plays down to 20hz or below. If you want bass that low at high output for cheap, you need to go big, like horn big. Then you have the f20 or tht for your options.
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post #24 of 82
12/29/12 at 9:56pm
Thread Starter 
Thanks guys I really appreciate all the help and new knowledge you've given me. smile.gif
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post #25 of 82
12/29/12 at 10:06pm
Thread Starter 
Also one last thing. If I instead go with the 3in. ports should I keep them at 17in. because the precision port site calculator shows a length of 10.7.
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post #26 of 82
12/29/12 at 10:13pm
Quote:
Originally Posted by studioholic55 View Post

Also one last thing. If I instead go with the 3in. ports should I keep them at 17in. because the precision port site calculator shows a length of 10.7.

17" yes. Not sure what you're calculating...
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post #27 of 82
12/29/12 at 10:27pm
Thread Starter 
Ok that answers my question. I'm also planning on upgrading my LCR. Would the Fusion-10 Maxs from diysoundgroup be a good deal?
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post #28 of 82
12/30/12 at 12:35am
You should take the speakers to a different thread with full details on your setup and placement. That speaker looks it it needs to be placed up against the wall.
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post #29 of 82
12/30/12 at 7:52am
Thread Starter 
So in conclusion I'm better off buying a "home audio" category sub instead of a pro sub? Also what is the difference between the HO and HF model subs and which should I get?
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post #30 of 82
12/30/12 at 9:20am
HO = small/average sized ported box

HF = large sealed box/huge ported box

Pro audio drivers need massive cabinets to tune low, and the models with enough xmax to work are expensive. You can also look at car audio drivers, many of them work well for home applications.
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