Time to upgrade my subs - Where to start? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 10 Old 08-12-2019, 09:44 AM - Thread Starter
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Time to upgrade my subs - Where to start?

After having an opportunity to demo two local theaters in SE Michigan this weekend, it convinced me that it is time to upgrade the subs in my theater. With that said, I need some guidance on designing the sub that will best fit both my needs and space and also how to pick the best components for the build.

A little background - my theater was finished almost 6 years ago (wow, time really flies when you are having fun). I currently have a 7.2 surround system in a dedicated, sound controlled theater. I currently am running two 15" sealed subs - one in the front behind the AT screen and one in the rear of the theater behind the second row. I am also running transducers in each seat. While I like the system I am currently running, I really would like to increase the low frequency output. I have several questions, but I will start with the basics:

Number of Subs? Options I am considering:
  • 1 sub in the front, 1 in the rear (current setup)
  • 2 subs in the front, 1 in the rear
  • 2 subs in the front and 2 in the rear

Size of the subs?
At the front of my theater, my speakers and sub are all behind the screen. I plan to put the new sub(s) in the same location. I really like the idea of the Full Marty sub or even a Devastator, but space is an issue - mostly when it comes to depth. Because of the frame that supports my AT screen, I only have 20" for depth. This is touching wall to touching frame. I could possibly notch the frame and gain three more inches (but still touching front and back). With that said, I could have two subs that are 35" wide and up to ~70" high and have an inch or two to spare. I am hoping to be able to build something that will perform the same as the Full Marty or Devastator, but with slightly modified dimensions. I really don't know where to begin to calculate the cabinet size and cut sheet.

At the rear of the theater, I want to go a bit smaller because I don't want them sticking above the chairs and don't want to prevent the chairs from reclining. Width isn't a major issue, but height and depth need to be around 20" or less.

Ultimately, I would love to buy a flat pack kit or have a woodworking shop CNC cut the parts, but I also have the equipment to make the cuts myself.

I guess I need to start with these questions first and go from there. Any input would be greatly appreciated.

Nick
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post #2 of 10 Old 08-12-2019, 10:21 AM
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If you really want the lows I would look at the HST 18s loaded in something the size of a Full Marty at a minimum. Loading them in an LLT would be more ideal, but LLTs require loads of displacement. Then go with MBMs to handle somewhere north of 30Hz. You could put the MBMs up front then put the HSTs in large boxes in the back.



With the shallow depth requirement Devastators are a tricky preposition, you could try building one really wide, around 36" it would be a little on the experimental side. The front chamber rails would have to be redesigned so that the driver diaphragm sees the load from the full width of the chamber. The ported boxes are very flexible for getting the desired form factor. Napkin math with a Devastator 48"x36"x20" would be a little small on the rear chamber, it is 9.98cuft feet without any deductions for the port, driver, or bracing, the tune would come out higher than desired. If you start pushing the height you might find the needed displacement for the rear chamber. The response would look more like a BMD when you add additional height to the front chamber, it picks up SPL sooner, but has less on the top end.

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post #3 of 10 Old 08-12-2019, 10:32 AM
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It looks like you could do a Full Marty equivalent at 18" x 34" x 40" for about 12 cft which would get you close to 11 cft with driver and bracing. Two of those tuned to ~15 - 17 hz should provide lots of the bass. You can also use the UM18 and save some money over the HST. Four total subs if positioned well would even out the seat to seat bass.

If you search, I believe there is a Modify My Marty spreadsheet that will help get the sizes and port lengths you need.
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post #4 of 10 Old 08-14-2019, 05:00 PM - Thread Starter
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Thanks - found the spreadsheet. I will play around with the numbers and see what I come up with. At this point, I'm not sure that there is any way to make the Devastator work.

Another question, if I start with two Full Martys behind the screen, could I put my two existing subs behind the back row, or would I need to have something closer to the specs of the Full Marty to make it work?

Also, with the space I have, is it worth trying to design a modified Full Marty that will fit, or is there something else I should consider?
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post #5 of 10 Old 08-14-2019, 06:04 PM
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Time to upgrade my subs - Where to start?

Quote:
Originally Posted by NGiovas View Post
Thanks - found the spreadsheet. I will play around with the numbers and see what I come up with. At this point, I'm not sure that there is any way to make the Devastator work.



Another question, if I start with two Full Martys behind the screen, could I put my two existing subs behind the back row, or would I need to have something closer to the specs of the Full Marty to make it work?



Also, with the space I have, is it worth trying to design a modified Full Marty that will fit, or is there something else I should consider?


If you put two full Martys behind your screen, then I would put your two 15” drivers in a couple ported cabs behind your seats. Did you see my nearfield cabs? They are 6cf net, tuned to 18. Because they are nearfield, they produce plenty spl. I forget the dimensions exactly, but they are something like 18 deep, 20 tall, 40 wide. Would that fit?

Also, you have lots of room upfront for 2 great subs. My subs could probably touch my screen under max excursion, but it’s not a problem. I can’t ever see the screen material move. Unless the rooms lights are on. I’d try and modify the Marty sub dimensions and see if you can make them fit.
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post #6 of 10 Old 08-14-2019, 06:17 PM - Thread Starter
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Quote:
Originally Posted by Jk7.2 View Post
If you put two full Martys behind your screen, then I would put your two 15” drivers in a couple ported cabs behind your seats. Did you see my nearfield cabs? They are 6cf net, tuned to 18. Because they are nearfield, they produce plenty spl. I forget the dimensions exactly, but they are something like 18 deep, 20 tall, 40 wide. Would that fit?

Also, you have lots of room upfront for 2 great subs. My subs could probably touch my screen under max excursion, but it’s not a problem. I can’t ever see the screen material move. Unless the rooms lights are on. I’d try and modify the Marty sub dimensions and see if you can make them fit.
Thanks Jared, I did see your nearfield cabs, but didn't pay close attention to the details at the time. Are they in your build thread? I'm not in a hurry, so I may play around with the dimensions on the Full Marty to try to make it work so I can fit two of them behind the screen. Then I can decide what I want to put in the back of the theater.

By the way, I am going to China in a few weeks, so I was thinking of trying to pick up a couple of clone amps while I am there if I can get them cheap enough. Then I wouldn't need to worry about shipping costs either. I emailed Sanway to see if they would offer a local price on two FP14000's. We will see what they say. Any thoughts on the Sanway vs the other clones? They are all made in the same town (same factory?).
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post #7 of 10 Old 08-15-2019, 09:42 AM
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Quote:
Originally Posted by NGiovas View Post
Thanks Jared, I did see your nearfield cabs, but didn't pay close attention to the details at the time. Are they in your build thread? I'm not in a hurry, so I may play around with the dimensions on the Full Marty to try to make it work so I can fit two of them behind the screen. Then I can decide what I want to put in the back of the theater.



By the way, I am going to China in a few weeks, so I was thinking of trying to pick up a couple of clone amps while I am there if I can get them cheap enough. Then I wouldn't need to worry about shipping costs either. I emailed Sanway to see if they would offer a local price on two FP14000's. We will see what they say. Any thoughts on the Sanway vs the other clones? They are all made in the same town (same factory?).


Yes my nearfield cabs are documented in my “sub changes Hst’s nearfield ds4’s’’ thread.

China eh? I have all xbs sinbosen amps. I don’t know who the other companies are or what not. I do love my amps though. Sounds sweet to omit the shipping charges. Because it’s a lot to ship these. Will you bring me home another amp?
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post #8 of 10 Old 08-15-2019, 10:47 AM - Thread Starter
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Quote:
Originally Posted by Jk7.2 View Post
Yes my nearfield cabs are documented in my “sub changes Hst’s nearfield ds4’s’’ thread.

China eh? I have all xbs sinbosen amps. I don’t know who the other companies are or what not. I do love my amps though. Sounds sweet to omit the shipping charges. Because it’s a lot to ship these. Will you bring me home another amp?
Thanks. I will check out your build thread for more detail. There are so many threads I am trying to catch up on between the Full Marty and the FP clone threads as well as others.
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post #9 of 10 Old 08-15-2019, 03:45 PM - Thread Starter
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How many subs can I run off of one FP14000? If I end up with 4 subs in my room, can I run them off of one FP14000, or do you recommend 2 amps for this application?

Ideally, I would redesign the Full Marty to fit in the front of the theater (2 of them) and then build 2 subs for the rear of the theater.
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post #10 of 10 Old 08-17-2019, 09:29 AM
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Quote:
Originally Posted by NGiovas View Post
How many subs can I run off of one FP14000? If I end up with 4 subs in my room, can I run them off of one FP14000, or do you recommend 2 amps for this application?

Ideally, I would redesign the Full Marty to fit in the front of the theater (2 of them) and then build 2 subs for the rear of the theater.
The FP20k is a bit better at powering 2 8ohm subs or 4 4ohm subs or 8 4ohm subs than the FP14k.
The 14k is better at powering 1 or 2 subs at 2-4 ohms.

Will it work?
It should.
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