Newb wants to do it right the first time - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 4 Old 10-18-2015, 08:20 AM - Thread Starter
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Newb wants to do it right the first time

You have quite a forum here. I've spent the last 72hrs digging in and I feel like I've learned a ton, yet still have lots to learn. I'm here to ask for your assistance.

I'm in the market for a new sub or 2, and thought I knew exactly what I wanted until I read a thread about how much more value there is in a DIY sub which quickly opened pandoras box. I then realized I had a Crown Drivecore XLS2000 laying around, which made the DIY decision even easier.

There is a lot of information out there and I've made some assumptions based on what I've read. Please don't hesitate to tell me my assumptions are wrong, that's why I'm here. That's why I'm asking.

Assumption #1
The only reason to choose sealed over ported is if space/size of enclosure is of concern. If you've got the space, go big and go ported.

Assumption #2
When talking about woofers from the same line, a 15 is going to be superior to a 12. The surface area is going to allow it to push more are and create more sound. The idea that a 12 is faster or punchier is false. The 15 will be just as fast, just as punchy, and be both louder and able to dip down into lower frequencies. Unless size is an issue, there is no reason to go with a 12. Keep in mind that this assumption is also assuming that they are properly powered in the same type of enclosure.

Assumption #3
If both assumption #1 and assumption #2 are correct, the best option is going to be a 15" sub in a ported enclosure.

Now would be a good time to tell me that my assumptions don't hold water.

Other questions...
Should I sell the crown in favor of a plate amp? If yes, what do you recommend?
Do I need some kind of DSP device? The crown has a crossover, but it doesn't do much more than cross the signal over. If so, what do you recommend?

Woofers: I'm torn between the Dayton Reference and the Eminence LAB. Is one superior? Should I be looking at something else because it's clearly better?

Additional information...
My home theater is in my basement. It's an L shaped room with 8' ceilings. The leg of the L with the home theater is about a 17x30. I spend equal time listening to music and watching movies. It's my favorite room in the house. I'm not concerned with how the bass sounds in the other leg of the room, but because it's there, you should also know that the other leg is 15x20.

Thanks in advance for your help.
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post #2 of 4 Old 10-18-2015, 08:57 AM
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Quote:
Originally Posted by Mike Schacht View Post
Assumption #1
The only reason to choose sealed over ported is if space/size of enclosure is of concern. If you've got the space, go big and go ported.
The other side of the tradeoff is extension. Output from a ported enclosure at frequencies below tuning will be very low, in general. So if you want ultra low extension, sealed is usually a better choice.

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Originally Posted by Mike Schacht View Post
Assumption #2
When talking about woofers from the same line, a 15 is going to be superior to a 12. The surface area is going to allow it to push more air and create more sound. The idea that a 12 is faster or punchier is false. The 15 will be just as fast, just as punchy, and be both louder and able to dip down into lower frequencies. Unless size is an issue, there is no reason to go with a 12. Keep in mind that this assumption is also assuming that they are properly powered in the same type of enclosure.
The logic is right - but why stop at 15? 18s are probably the most popular choice for DIY. That said, mine are 15.

Quote:
Originally Posted by Mike Schacht View Post
Assumption #3
If both assumption #1 and assumption #2 are correct, the best option is going to be a 15" sub in a ported enclosure.
The easiest option is the 18 in DIYSG ported flatpacks, and will be more output than an equivalent 15.

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Originally Posted by Mike Schacht View Post
Should I sell the crown in favor of a plate amp?
Usually, $/watt you're better with rackmount. Of course, gear you own is generally cheaper than gear you have to buy. The other thing you might consider is cabling. If you have a long distance between where you place the sub at the gear that drives it, you might find signal cables more prone to interference over long distances than amplified speaker cable. (Minor consideration in most cases.)

Generally, you will want DSP for subs. The specifics are not something I can direct you on.
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post #3 of 4 Old 10-18-2015, 09:13 AM - Thread Starter
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Fred, thanks for the input.

You mention that on a ported enclosure frequencies below tuning will be very low. Does the same go for above tuning? Does that mean that you tune to the lowest possible level?

If you were to start over would you choose 18 over 15 and why?
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post #4 of 4 Old 10-18-2015, 10:48 AM
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A properly sized and ported enclosure can (when desired) have flat response down to approximately the tuning frequency. Below that, output falls at 12 dB per octave - 2nd order rolloff. Sealed enclosures roll off first order - 6db per octave.

I say "when desired" because it is common in commercial designs (particularly in mains, less in subs) for the output to have a hump or peak to give the impression of more bass. Less fidelity, but more bass...

In my case, I have a medium to small sized room. I knew I wanted multiple sealed subs, so I asked around and determined that 15s would give me the output I wanted when used in the multiples I intended. 18s were needlessly large and expensive for my expectations and would have encroached on aisles and seating spaces. https://www.avsforum.com/forum/155-di...ce-system.html
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