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It's time to build a DIY Ported 20Hz- Sub, single 15" or 4x 8"

20K views 18 replies 3 participants last post by  javi404 
#1 ·
So I'm looking to build my first DIY sub for my home theatre, I've build plenty of sub boxes for car audio in the long ago past but this is my first for a home.

There are so many options out there now that I would love some feedback on some of the ideas I have and figure this thread can serve as a home for some feedack. I am sure to post the build and results in another thread.

Right now this is what I am looking for:
Replace passive Onkyo 8" ported 30Hz sub (will go down to my office)
Build passive (open to active) sub, primarily for 50Hz->18Hz (or lower) frequency response for everyday listening in my living room.

My fronts each have dual 6.5" drivers with dual 2.5" passive radiators (towers) and pretty decently go down to around 35Hz.
I'm really looking to hit what I'm missing from my current sub and get nice responce down to the 20Hz range.

From previous experience building subwoofers for car audio (more than 10yrs ago) I know there is cabin gain.

I'm assuming there is room gain that can help me in the less than 45Hz range? (I should probably measure the room at some point)

The biggest debate in my head right now is do I go for a bunch of small drivers such as 4x 8" or 1x large driver like a 15" or 18" from parts express, mcm electronics, or amazon?

What are your thoughts on multiple smaller drivers (tighter sound?) vs 1 large driver (looser sound?)
Size is not a problem for my build. I'm already thinking about a large 6" port.

Hope I didn't write too much for my first post to this forum.
I hope to contribute as much as I gain from home theater shack. :D
 
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#2 ·
Well first hello and glad to see you in the DIY section. What is your budget?

I would say go as big as your wallet can afford. Just include your amp and wood supplies as well in the budget.

For 20hz I am thinking nothing less than a 15". But thats me. Just make sure when trying to compare woofers that you are compairing total displacement. So your 8's might be better than a single 15 with minimal Xmax.

How big of a box do you want?

You could build a horned sub also that offers killer 20hz performance for minimal dollars. But they are BIG.

Sealed is good if you can afford multiples and want a small cabinet. Ported for me offers the most usability from one woofer. So if you want more performance and are stuck with the single woofer then ported is a good option.

And dont think that 8's are going to sound any tighter than a 15. What Q alignment are they in plays a big part also for sealed and Fb for ported. An 8" can sound just as "loose," as a 15 or bigger.
 
#3 ·
I was looking to spend no more than 300 bucks.

I'm probably going to stick with an existing / external amp for now.
If anyone can recomend a nice plate amp that can power a 15" I'll definately consider it.

I still have some math to do but now I'm wondering if 20Hz is low enough for tuning now. I recently read a review on here and the lower than 20Hz content in some movies was mentioned. unless its not worth it I'm going to plan to tune to 18Hz.

I can go big if i get creative with box design, maybe a tall sonotube in the back of the room, maybe a long thin but high box behind the couch?

I'm a huge fan of ported boxes myself so ill stick with that design but horn might be pushing the limit on size since most designs I have seen are large cubes and more complicated wood cutting/measuring.

I was mostly thinking many small subs to do interesting design (like behind couch) but I think I im leaning towards a decent 15" sub. I'de be happy to take any feedback on decent 15 inch subs as well.

I'm going to start looking at drivers and boxes in winisd (any other good free software out there?) and post some results / plots as soon as I have some time this week.

Thanks for all your help already.
 
#4 ·
Off the top of my head these are the top contenders for 15" under 300:
Dayton Titanic 15"
Fi SSd 15"
Fi Q 15"

I am sure there are some more but these are the ones I can think of for now. They will all simulate well and like nice ported boxes also.

I am still holding out for SI to come out with their 15". Should be priced at under 200(179). They would be perfect for your application but not out yet.:( And it could be some months from now also.

In regards to a plate amp......well most of the Fi subs will take more than a simple cheap plate amp. But you could use a O Audio 500 watt amp and just be limited amp wise. Or you could just buy a Behringr amp such as the Inuke amp.

Your call ....some like to have the amp on the back of the sub and it turns on automatically verse a poweramp which is stand alone.

A lot of people are happy with a big ported box tuned to around 17hz for movies. While others need more.(Me) So you have to start some where. And thats your call. A pair of 15's is a nice start for a HT.
 
#5 ·
Off the top of my head these are the top contenders for 15" under 300:
Dayton Titanic 15"
Fi SSd 15"
Fi Q 15"
Yes, I have been itching to buy one of the Daytons, possibly the titanic, and have also looked at the HF and HO versions.
But it seems like the price difference might be right to just to pull the trigger on the Titanic.

I have also looked at many car audio subwoofers but I feel like there is more value in the Titanic.

Unless someone has new ideas to throw at me ill be pulling the trigger on that beast for my soft 300 sub budget.

I am sure there are some more but these are the ones I can think of for now. They will all simulate well and like nice ported boxes also.

I am still holding out for SI to come out with their 15". Should be priced at under 200(179). They would be perfect for your application but not out yet.:( And it could be some months from now also.

In regards to a plate amp......well most of the Fi subs will take more than a simple cheap plate amp. But you could use a O Audio 500 watt amp and just be limited amp wise. Or you could just buy a Behringr amp such as the Inuke amp.

Your call ....some like to have the amp on the back of the sub and it turns on automatically verse a poweramp which is stand alone.
After looking at all the plate amps out there I like what they offer in general. High leven inputs, extra low pass filter, sleep modes. But the one thing that started to push me in another direction is if the amp fails, I have to possibly modify the box or seal that hole to replace it.

I'm deciding to keep the amp seperate from the sub for that reason. going with existing or new external amp. (started too look for things outside of my $300 range, but the 300 was for the sub alone.)

im thinking a thousand watt amp will do fine with either high input or a hi/low converter.

A lot of people are happy with a big ported box tuned to around 17hz for movies. While others need more.(Me) So you have to start some where. And thats your call. A pair of 15's is a nice start for a HT.
I think im going for the 17 Hz, One thing I will do is figure out a way to tune lower if needed. Ill worry about that closer to final product purchase and start of design/build.

I'm not opposed to an external port as long as its somewhere hidden.

I would love to go for dual 15 subs but since I am in a rented townhouse, I am trying not to push the limits with my neighbors. I figure one 15 is enough for me right now.
One advantage I do have is I work from home so when I'm done for the day, my neigbors are still on their way home from work. Nice to be able to crank it up in the daytime.

I've seen much in the forums about EQs for subs. What are my options and do I need it really?
:scratch:

parts express part numbers for anyone curious about the subs in questions:
(I'm too new on this forum to post links)

15 Titanic:
295-420

15 HF:
295-468

15 HO:
295-469
 
#6 ·
Dayton Titanic
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-420
Dayton HO
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-469
Dayton HF
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-468
Fi SSD
https://ssl.perfora.net/www.ficarau...Speakers/0040_SSD/product_overview.shopscript
Fi Q
https://ssl.perfora.net/www.ficarau...0_Speakers/0030_Q/product_overview.shopscript
Now the Fi Q has more Xmax and is about 300 each. I have had dual opposed sealed sono SSD 15's and they sounded awesome. But we are starting to push the budget.

EQ is always a good thing to have and REW downloaded. Minidsp is a cheap and very nice option as is the Behringer DCX2496. EQ will help in having your sub sound the best it can within its own design.

http://www.minidsp.com/onlinestore/browse/7-minidsp-kits?sef=hc

DCX
http://www.parts-express.com/pe/showdetl.cfm?partnumber=248-669
The minidsp is cheaper than the DCX.
 
#8 ·
Well from my experience Fi is a high quality manufacturer that makes nice subwoofers. They are one of my top 3 go to for subwoofers and value.
 
#9 ·
#10 ·
I will have a look at the imulations on WinISD later when I can but a quick note would be that you want as much displacement as you can get. So with the HF/HO only having about 14 Xmax and the others having 20+ it would seem mute to say the HF or HO could do any better.

SO in your choices I would say the Fi Q is the biggest "mover of air," and then the Dayton Titanic.

But I will simulate them later on and see what I get.
 
#12 ·
Sorry for the late reply. What were you thinking of going with?

All those simulations have the woofers hitting Xmax with minimal wattage because of the boost. Dont forget that you will get room gain so you might want to add in EQ after it sits in your room. The most wattage I could use was with the Fi Q and that was about 140watts. SO you would not need much power. With the added EQ you gain about a .5db over no EQ and more wattage.

And your Titanic file did not have enough info in the T/S to be useful.
 
#14 ·
I used your files and opened WinIsd. I then just clicked on the down tab on the simulation window in WinIsd. That will let you look at excursion or spl or many other options.

The down tab is right next to the driver tab.
 
#15 ·
So, I have been playing around more in WinISD.
I've pretty much made up my mind to go with the FI, long story short, the 28mm xmax will just plain and simple allow that beast to take more power and go louder.

I'm currently playing around with this design: 4.5CF @ 17Hz
5 inch port 36 inch long (might have to make this an external port)

comparing 3 different options

4x 8 inch
1x Dayton 15HO
1x FI Q15 dual2 ohm

I turned off all EQ and Filters and threw 600W at everything to see what it looks like.
I focused on cone excursion and SPL and then took a few screen shots with the FI pumped to 1200 and 1500W just to see what it looks like.

Am I on the right path here or should I be looking at some other parameters such as group delay?

One question I have is about ordering the Q15 from FI. There are some options I am not sure about and I am also not sure how those options affect my modeling of the sub.

example:

Cooling:
P Chamfer:
High QTS:
Spider:
I Heat Ring:
Internal Lead

Any help is greatly appreciated.
 

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#16 ·
#18 ·
Check out my build. I think you're going down a similar path. I would recommend a lower tune (at least 15Hz). Make sure you read the LLT sticky post. I love my MiniDSP. It's one of the only ways you can get a good digital HPF that can go low enough to tame an LLT. Make sure you amp doesn't have an HPF built into it (they're usually at 20 to 25Hz; useless for Real Men home theater subs).

You're going to need ~7" diameter port. If I had mine to do over again, I would slot-port (I did with my little 8" - easier to build and sounds great).

If you're only ever going to have one sub, then I recommend going with the big xmax. I love having my dual coffins. Dayton is the least sub-20Hz clean SPL/$ you're going to find. But I had just my one for a while, while I was building the 2cd. One was not enough to make me happy.
 
#19 ·
Just to update.

I ordered the FI Q15.
The only option I added was the cooling just for the of it.

It was nice to find they took paypal. That means it didn't come out of my loose budget. It came from money I forgot i had in my paypal account.

Currently deciding on building a slotted port or trying to figure out a flared port option.

can't wait to unbox sub when it gets here.
 
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