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Need design help and advice - Building sub enclosure


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#1 of 34 Firelime

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Posted November 27 2011 - 04:38 PM

So.. I am working on building my home theater right now (drywalling this week) and am looking at building a sub enclosure. I currently have 2 Polk PSW505's, while they sound good I would like more. Both in the feeling (impact of explosions type) and the richness of the sound. The Polk's leave me wanting, I feel they drop the ball down low. I have my theater wired for a sub at each of the 4 corners and was going to buy 2 more Polk's but I feel i'd be in the same position. I have thought about building an enclosure for awhile and then came across this topic that peaked my interest. (http://www.hometheat...t-yourself-subs) I have built several car audio sub boxes in my day but never a tuned home theater box nor have I ever bought any home audio amps, only receivers. The box would have to be incorporated into the raised seating platform. Approximate size will be 80" wide x 75'' deep x height can vary but probably not much over 12". It will have bracing in it to support the sofa. I would prefer a ported or horn enclosure. I wouldn't be opposed to pushing more power either than the amp in the original post. Anyways would anyone be willing to help me design a sub enclosure and offer some advice on the sub and amp to get? Room size is 24' x 12'. Also should I build the amp (not a plate amp) into the platform or keep it with the rest of the A/V equipment? If not built in, would 14 gage be enough to span the distance, about 20' of wire? Taken from advice given to others on here I put the subs on their own circuit, along with the receiver on its own and an extra 20 amp line in the A/V cubby just in case. Budget would likely be around $500-600 for the sub/s and amp. Thanks, Bryce

#2 of 34 Robert_J

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Posted November 28 2011 - 04:43 AM

I would prefer a ported or horn enclosure.

With a ported sub, you will have to factor in a subsonic filter into the cost. That will take about $100 of your budget. For a horn, there is no way to build one that size. Here's what a good home theater horn sub looks like - Why are you mentioning 4 corners are wired for subs but then wanting a design built into your riser? That really limits you on placement. Also, how are your 4 locations wired? Speaker wire or sub cable?

#3 of 34 Firelime

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Posted November 28 2011 - 04:50 PM

Well it looks as if the horn sub will be out. The subsonic filter would not be a problem. I guess a sealed enclosure would work as well. I am new to the home theater world and would like to learn. What would be the advantages and disadvantages of going with either enclosure? The locations are wired with sub cable. The riser will be placed at the rear-center of the room. If I were to build a enclosure I would perfer it built into the riser. Would this cause much of an issue with sound quality?

#4 of 34 Robert_J

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Posted November 28 2011 - 11:05 PM

I would perfer it built into the riser. Would this cause much of an issue with sound quality?

You are always taking a chance by building a sub that can't be moved. If your sub / seating location is in a null, there will be absolutely nothing you can do but add an additional sub to help it out. We always recommend being flexible with your sub location so that you can choose the one that sounds best. Once a sub is in a room, it interacts with it and the frequency response changes. Some places in the room will be louder (peaks) and some will be quieter (valleys). Some spots will be almost empty of bass (nulls). An EQ can pull down the peaks and sometimes boost the valleys but there is nothing that can be done to the nulls except move your seat, move your sub or move both. Building a sub or subs into the riser will be easy. You have more than enough space to do it. You will be limited to 12" drivers and smaller if you build the riser using standard building measurements of 16" on center. Plus, out of your $600 budget you are looking at spending $250 to $300 for a good amp. Add in a pair of 12's and you are right at your limit. Think it over and let me know. Riser sub or conventional sub?

#5 of 34 Firelime

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Posted November 29 2011 - 11:20 AM

Thinking it over I would like to go with the riser. Which amp and subs would you recommend? Before I put drywall up on that half of the room is there any other wires I should run besides the power and sub cable that I already have?

#6 of 34 Robert_J

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Posted November 29 2011 - 01:58 PM

A pair of either of these subs: http://www.parts-exp...tnumber=295-464 http://www.parts-exp...tnumber=295-185 An amp: http://www.parts-exp...tnumber=248-749 But based on the size of the enclosure you could huge. Eight 12's or four 15's. Just a wild idea. Eight 10s - http://credencespeak...ategory_Code=BO And an EP-4000 - http://www.guitarcen...706-i1448739.gc Once you decide on what you want, we can start a design. Remember if you want ported, you need a subsonic filter like one in the Reckhorn B2 or the Behringer mic2200. That will eat a little into the budget.

#7 of 34 Firelime

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Posted November 29 2011 - 04:21 PM

I did find the EP4000 at Parts Express for $309 thru tomorrow. So I am assuming to do the 8-12's or 4-15's it will have to be a sealed box. The 15's would have to fire upward behind the sofa and could run the risk of being stepped on. Looks like I have something to think about tonight.

#8 of 34 Robert_J

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Posted November 29 2011 - 11:20 PM

You can still do ported. Most 15's will work in 4 to 5 cubic feet tuned somewhere between 18 and 22hz. You will need some beefy 15's though. I've running my Behringer into a pair of TC Sounds TC-3000 15's. It's the predecessor to the Axis model. They each get about 800w at 20hz in a 3 cubic foot, sealed box. No subsonic filter but I did add an EQ to flatten the response to 17hz. I get usable output below 15hz while still having output that is completely insane. I mean shake my house's concrete foundation insane. You could do the same except for your budget.

#9 of 34 Firelime

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Posted November 30 2011 - 12:16 AM

Could you post up a link for the subs?

#10 of 34 Robert_J

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Posted November 30 2011 - 03:27 AM

I use an earlier version of these subs - http://www.parts-exp...tnumber=293-642 One on each channel of a Behringer EP-2500 (same as an EP-4000). I also use a BFD as an EQ - http://www.parts-exp...number=248-6678 This blows your budget through the roof. On the other hand, this is an awesome subwoofer that has more output than any retail sub under $10,000.

#11 of 34 Firelime

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Posted November 30 2011 - 12:32 PM

The wife just said I could do whatever I wanted as long as I don't blow her ear drums. So... lets build a sealed box for 2 15" Axis. Assuming the sub enclosures will be seperated, I'll buy 1 to start with and a second later. Besides we may not need more than 1 Axis if it satisfies.

#12 of 34 Robert_J

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Posted November 30 2011 - 02:13 PM

Your enclosure needs to be somewhere between 3.5 and 4 cubic feet. Stuff it with 3 cheap pillows from Wal-Mart and start playing. With an inductance of 9mh, you will need that EQ to tame the inductance peak at 54hz otherwise it will sound like a boom box.

#13 of 34 Firelime

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Posted November 30 2011 - 06:16 PM

With an inductance of 9mh, you will need that EQ to tame the inductance peak at 54hz otherwise it will sound like a boom box.

Please explain the first part.

#14 of 34 Robert_J

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Posted November 30 2011 - 10:58 PM

Look at the Theile/Small specifications of the driver at the link. Le: 9 mH is the spec I am referring to. The inductance is high due to the 3" diameter, 60+mm long voice coil. It is one big inductor - http://www.parts-exp...e-inductors.cfm . This high inductance causes a peak in the frequency response around 55hz. I had it on my subs but added a BFD to bring the peak down and flatten the rest of the response. Don't want to deal with a BFD, buy a sub with lower inductance like this one http://www.parts-exp...tnumber=295-468 . If you are still going with the Behringer amp, then buy 4. That amp can easily drive 4 without ever breaking a sweat. Put each sub in a 4 to 5 cubic foot enclosure and stand back. If 15's are too much, use 4 12's - http://www.parts-exp...tnumber=295-464 . Same motor (magnet/coil combination) so the inductance is low. Put each in a 3 to 4 cubic foot, sealed box.

#15 of 34 Firelime

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Posted December 01 2011 - 04:37 PM

I see. Thanks. Is there anything else I will need for tuning them besides the EQ in the receiver? And if I go with the less expensive 15's can I still get down below 20hz?

#16 of 34 Robert_J

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Posted December 01 2011 - 11:12 PM

The EQ in the receiver is not accurate enough to tweak a sub. The BFD is a 12 band, digital, parametric EQ that will go as low as 17hz. With four of the Dayton 15's you will definitely get down below 20hz. If I were you, I'd go with the four 15's and an EP-4000 amp. After installation, measure the frequency response. On then would you decide if you need to add a BFD. Those Daytons are very low inductance subs geared towards sound quality. The only peaks and valleys you will have in the response will be room related and you will only know about them after installation. It will be location dependent in the room. Do you have an equipment closet? The EP amps are notorious for loud fans. I bought a replacement fan for $10 and I can barely hear my amp now.

#17 of 34 Firelime

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Posted December 03 2011 - 03:57 PM

Cool. It will be a couple months, probably Feb. before the theater is up and running. Still a lot of work to do. I do have a closet but it will be full already. I'll probably just replace the fans when I get the amp. Thanks for all your help. I'm sure when I get the enclosure all put together i'll have more questions. :)

#18 of 34 Firelime

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Posted December 06 2011 - 04:21 PM

More questions

Don't want to deal with a BFD, buy a sub with lower inductance like this one http://www.parts-exp...tnumber=295-468 . If you are still going with the Behringer amp, then buy 4. That amp can easily drive 4 without ever breaking a sweat. Put each sub in a 4 to 5 cubic foot enclosure and stand back. If 15's are too much, use 4 12's - http://www.parts-exp...tnumber=295-464 . Same motor (magnet/coil combination) so the inductance is low. Put each in a 3 to 4 cubic foot, sealed box.

Is this including the volume in the box the sub will take up? Or will I need to add that to it? Also will I notice much of a difference if the fire the subs up instead of forward? I would like to go with the 15's, but they will have to be fired upward. The 12's would be fired forward.

#19 of 34 Robert_J

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Posted December 07 2011 - 12:35 AM

Subs take up about .1 cubic feet or less. In boxes this big, it makes no difference. No. The subs I linked to will fire up or down without any performance issues.

#20 of 34 Firelime

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Posted March 11 2012 - 06:33 PM

Well finally ordered the subs and amp. Well 2 subs anyway, the Dayton Audio RSS390HF-4 15" Reference. I'm still building the riser to hold 4, just starting with 2. We took a little break from the theater project. We finished up paint today and the carpet is on the way. Hopefully we'll be up and watching early April. Thanks Robert for all the help. I'll probably have a couple more questions for you shortly.