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Port size for DC lvl 2 12"


Casparado

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Hey guys/gals, first post. Just as a quick hello to introduce myself... I am 40yrs old, live in NorCal, and have been installing my own car audio since I was 16. Every vehicle I have ever owned has remained with stock sound for only months before the bug bit me. I have been watching SMD on you tube for quite a while and I am SO HAPPY I finally found the community, so thank you! Anyway on to the meat of my question...

I have a single 12" Infinity Kappa perfect 12.1 (the kind with the white aluminum cone) in my truck (powered by 500w RMS) that is quite old and the surround is starting to separate... so it's about time to replace it. I am thinking the DC lvl2 is a nice replacement, but my enclosure is sealed and around 1.25ft^3. In order to use the same enclosure that fits behind the seat perfectly, I am thinking a port would bring it do DC's specs (.75ft^3 sealed, 1.25ft^3 ported.) ... I know it's not going to be perfect because the sub fills 0.15ft^3 and the port will take room also, but it will be close. 

So, my idea is basically to just cut a hole and bolt a round port in it. The port has to be short enough to not connect with the sub itself, obviously, and preferably round to make installation simple. The box is a crutchfield S/O trunk box... exact dimensions are 17-3/8"W x 14-1/2"H x 13-5/8"D1 x 10-1/2"D2. If I tuck the port into the rear corner I am hoping there could be enough room. 

After everything I have seen and read about DC speakers I want to give them a shot, but my finances are tight and I can only afford just the speaker at the moment, so I NEED to use the same amp and enclosure. Any help towards what port dimensions I should use would be SUPER appreciated. Thank you! 

 

(sorry if this has already been asked. I did a search and was a bit overwhelmed) Thanks again for any help! 

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Just to clarify I used a few online calculators and the mean outcome seems to be around 3" diameter and 10" long. .... However I know how these calculators tend to be 'one size fits all' which makes them hard to trust, so I am hoping you guys might have a little more insight when it comes to high excursion subs. Also just for a little more insight, I am very much about SQ, but I like volume A LOT. I was raised in an extremely musical family. Both my parents are orchestral musicians, and I am your typical band geek, to the level that I was carving oboe reeds at a young age. I can hear clipping and 'off sounds' more than I would like. 

Sorry I am getting off track. I think what I am trying to say is that I have a general idea of what to go with, but I am hoping someone on here that is WAY more experienced than me can give me some good insight and maybe help me avoid some common pitfalls and mistakes that might completely ruin my sound. 

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Here is a link to my port area calculator.  It takes things like box volume, tuning frequency, and input power and give you a suggestion for port area.  

https://goo.gl/STAv4p

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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Thanks for the response Triticum. I have another quick question for you if you have a moment. How are the DC lvl2 subs musically? The Kappas were extremely efficient (93db@1w),had an FS of 23.32Hz and a freq response of 18-200Hz. They sounded amazing in a sealed box. I am a little nervous going to DC's in a ported box. I don't want to lose the low end extension and I can't find numbers on the DC freq response. I know they're just stats and ultimately what matters is how they sound... any suggestions? (I am pairing it with Focal mids/highs FWIW) 

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The efficiency and frequency response of a subwoofer is going to be VERY box dependant.  Please keep in mind that efficiency ratings on subwoofers are completely meaningless because there isn't a standardized way to measure them and they are usually done in free air and at 1 kHz.  I don't know why manufacturers even bother.    The posted frequency range is equally useless because again, it doesn't take the enclosure into account. 

As far as your specific situation goes, you certainly can try putting the DC sub in your current box and running them sealed just to see how they sound.  If nothing else it will give you a good base from which to compare how they sound in a ported box.  The ported box should have a lot more output around the tuning frequency compared to the sealed enclosure.  

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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Thanks again for your reply! I've got so much to learn, lol.  I am very surprised that speaker efficiency ratings are not standardized, but what you said makes sense. Do you think the DC lvl 2 is the best choice for a musical sub with 500w RMS and a 1.25ft^3 enclosure in an extended cab truck? Or ios there another brand I should check out? 

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After doing a ton of reading on the subject I have decided to go with a B2 Reference series 12". I like the lower FS of 20Hz... From what I have been reading it seems like for comp quality subs, SQ versions have a low resonant frequency and SPL subs generally are closer to 35HZ. The B2 has a slightly lower xmax of 20mm than the 22mm that DC boasts , But that's still 6.5mm larger than the Kappa's at 13.5mm. Combine that with being able to run my amp at 2ohms, and I should see a huge bump in output, while keeping my SQ equal or better. Plus the B2 recommends my exact box size (after displacement) for a sealed enclosure, and the QTS of the B2 Ref 12 indicates it likes sealed enclosures best.... could be a match made in heaven for my particular setup :)  what do you think?

 

Thanks again for your help. If/when I do eventually decide to build a custom box and go dual ported 12's, your port calculator is going to be invaluable! I've been dying to build something massive like that, but obviously there is a lot more to building a system like that than just the box, speakers, and amp. 

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Hey sh!t man sorry one last technical question. If I DO decide to port my box, and according to your calculator I need, lets say, 6" diameter port size for 28^2" space, can I drill (4) 3" holes to equal the same total amount of space? Or is this going to cause port noise across all 4 ports? Is there more buffer against port loading with one big port, or is it equivalent to use a bunch of smaller ports as long as the overall port area is the same? 

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Either the B2 or the DC sub should work fine for what you want to do.  Sealed boxes are very forgiving and the difference in performance between the two will be very minimal.  

As far as your port question goes, using four 3" ports would give you the same port area as one 6" port, but its not going to perform the same.  The reason is four 3" port has a LOT more (twice as much) internal surface area than one 6" port does.  All the surface area translates into more air resistance.  The efficiency of round ports comes from the fact that they have the least amount of internal surface for a given amount of port area.  With round ports you want to use one or two larger ports, once you go past two ports you are going to be better off with something like a slot port.  

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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