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post #1 of 81 Old 02-13-2019, 03:09 PM - Thread Starter
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Help with DIY behind the couch subwoofer box

I have a space behind my couch which is really just a void. I’d like a room filling, responsive woofer. I wonder what frequencies I’m missing and wondering if I can get some tactile feel and chest thump with a large woofer and more powerful amp.

Currently: 10” Onkyo HTIB type SKF 540, ported, “130” watt wamp. Two Infinity Crescendo’s 3006, cheapo Sony surrounds (5.25”/tweeter) and a BIC FH6 Center channel above TV, powered by Yamaha RX-V675 AVR.

The subwoofer does it’s job, I guess. But my issue with it is that it feels underpowered and far from “responsive”. It really does seem to be all that active to me, either because of an early drop (maybe around 35+hz or below)

Box size exterior could be 6x17x60” (WxHxL). I get roughly a 3.5 cu. Ft box from that, if I calculated right, more if I length to box to 72".

I could go a little longer 60+, a tiny bit wider 6+ and a tiny bit higher 17+. Wider or higher would require me to move my couch further out. I see that a Dayton Classic 12” is 5.5 inches from the inside of the frame to the edge of the magnet. I assume I’d need at least an inch behind it? This would mean the interior would have to 6.5 inches and with two ¾ mdf I’m looking at 8 inches total width .

The room is 17.5x9.5x9 so about 1500 cubic feet, the room is entirely enclosed, one door in, one door out. Windows on three sides, brick wall on other. Concrete floor with thin vinyl plank flooring.

I don’t want to spend more than $400, the cheaper the better honestly. I have woodworking skills and all the tools that this job would require (well my father in law does at least). I do not care what the box will look like as it will be hidden.

I don’t now, but may eventually get an AVR with Sub EQ. For now I’d like to avoid a DSP/miniDSP/iNuke sub. I strictly want to stay with a plate amp.

Any ideas? Port could go out either side or up, whatever is best. Sub, presumably would have to fire at the couch. I guess the real question is, how much clearance from the magnet to the rear of the box is needed first and any major downsides to having the couch close to the excursion point of the woofer?

Other spitballs:
-Maybe a crazy idea, but what about two of these guys? Or start with one, see how it does and if it's lacking get another? Monoprice SSW-10 (~$150.00)
-Scrape all of this and go with an SVS PB-1000?? My wife will hate me and I may be forced to sleep on the couch.
-Build a sonotube with either a 12/15" to put in the corner in place of an existing speaker stand (would have to be 36" max height).
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post #2 of 81 Old 02-13-2019, 04:03 PM
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Check out the "12" BestBuy $29" thread. The only rub is that those drivers are 6.5" deep. If you could swing a couple extra inches deeper then I'd go that route. Check out the thread anyway for some good ideas.
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post #3 of 81 Old 02-13-2019, 04:08 PM
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I bought two of the JBL cs1214s when they were on sale for $29 ea. So if you can find one of them you can build a ported 3.5 ft3 box with 250w amp and hit about 22 hz for about $300.

search here for @Zarkoff500 and @EndersShadow as they have tons of experience with these and were both very kind to help me with mine.

Last edited by eriksells916; 02-13-2019 at 04:22 PM.
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post #4 of 81 Old 02-13-2019, 04:10 PM
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Sounds like an ideal spot for a Sonotube type cylinder sub. I have an old HSU TN1220 and it's got tremendous output. I bet there are a LOT of drivers out there that would do well in that kind of environment.
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post #5 of 81 Old 02-13-2019, 05:37 PM
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Quote:
Originally Posted by eriksells916 View Post
I bought two of the JBL cs1214s when they were on sale for $29 ea. So if you can find one of them you can build a ported 3.5 ft3 box with 250w amp and hit about 22 hz for about $300.

search here for @Zarkoff500 and @EndersShadow as they have tons of experience with these and were both very kind to help me with mine.
I wouldn't say tons of experience but a little Thank you for the kindness either way. My CS1214 turned out a little lower than 20 hz and to my ears sounds pretty good. The tactile from down firing is a bonus.
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post #6 of 81 Old 02-13-2019, 06:35 PM
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Does the back of your couch angle in towards the wall? Meaning, is it more than 6" from the wall at the base? And then at 17" tall, the couch is 6" away from the wall?
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post #7 of 81 Old 02-13-2019, 06:38 PM - Thread Starter
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Quote:
Originally Posted by jcmccorm View Post
Check out the "12" BestBuy $29" thread. The only rub is that those drivers are 6.5" deep. If you could swing a couple extra inches deeper then I'd go that route. Check out the thread anyway for some good ideas.
Found one on ebay for $49.00. Is that good price? Is running two of them off a 300 watt bash amp a terrible idea? Are these better than the Dayton Classic's?
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post #8 of 81 Old 02-13-2019, 07:05 PM
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Help with DIY behind the couch subwoofer box

Double check me here on the mounting depth but I think the box needs to be a min of 8 3/4” deep (that number is inclusive of the front and back pieces of 3/4” MDF) to accommodate them properly. That allows for 1/2” of internal space for driver venting. This assumes you surface mount them. If flush mounting add another 3/4” to that.

Then you have to add in some space for the woofers to move forward without hitting the couch, so add about another 1/2” just to be safe.

So I’m not sure you have enough space without moving your stuff forward.

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post #9 of 81 Old 02-13-2019, 07:57 PM - Thread Starter
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Quote:
Originally Posted by EndersShadow View Post
Double check me here on the mounting depth but I think the box needs to be a min of 8 3/4” deep (that number is inclusive of the front and back pieces of 3/4” MDF) to accommodate them properly. That allows for 1/2” of internal space for driver venting. This assumes you surface mount them. If flush mounting add another 3/4” to that.

Then you have to add in some space for the woofers to move forward without hitting the couch, so add about another 1/2” just to be safe.

So I’m not sure you have enough space without moving your stuff forward.

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Hmmm, so if I could do the 9.25 out from wall, this would accommodate width of the box, excursion of the sub and the 1/2 inch. So 5.5 depth of Dayton Classic 12" Subwoofer, plus 1.5 inchs of MDF, .5 breathing room. It's listed as needing 3.42 cubic feet in a ported box at a 26hz tune. Do I need to hit that cubic amount on the nose, what if I go a little larger? Maybe that's better if I install bracing and a plate amp? Say shoot for 4 cubic feet?

Is this a good idea? I'd really like to knock the socks off my 10" Onkyo. Think the Dayton classic 12" and a 300 watt bash amp would do that?
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post #10 of 81 Old 02-14-2019, 06:55 AM
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a very effective near field sub, especially for midbass, would be the behringer subwoofer. check out their little powered sub. I tried it behind my couch for a while to prove the effectiveness of midbass drivers before ordering midbass modules from DIYSG and built them myself.

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post #11 of 81 Old 02-14-2019, 12:16 PM - Thread Starter
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Quote:
Originally Posted by blazar View Post
a very effective near field sub, especially for midbass, would be the behringer subwoofer. check out their little powered sub. I tried it behind my couch for a while to prove the effectiveness of midbass drivers before ordering midbass modules from DIYSG and built them myself.
Thanks, I'd need to change over the signal from my AVR to that larger PA style plug.

Regarding box behind couch vs. corner sonotube. If I went the sonotube it would truly be in the corner ("no one puts sonotube in corner"), not near it or in that quadrant, directly in the 90 degree part of the corner. Does that change anything? Would the subwoofers with enough excursion coverage be better behind the couch than a sonotube shoved in a corner?

Anyone seen any kinda odd shaped boxes like what I'm describing? Specifically, I think I can figure out the dimensions I need to get the cubic feet right, but length/diameter of the port is totally over my head. Is 20hz achievable with a 12" Dayton Classic Woofer or similarly priced one?
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post #12 of 81 Old 02-14-2019, 07:36 PM
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Quote:
Originally Posted by CheapSpeakerGuy View Post
Thanks, I'd need to change over the signal from my AVR to that larger PA style plug.

Regarding box behind couch vs. corner sonotube. If I went the sonotube it would truly be in the corner ("no one puts sonotube in corner"), not near it or in that quadrant, directly in the 90 degree part of the corner. Does that change anything? Would the subwoofers with enough excursion coverage be better behind the couch than a sonotube shoved in a corner?

Anyone seen any kinda odd shaped boxes like what I'm describing? Specifically, I think I can figure out the dimensions I need to get the cubic feet right, but length/diameter of the port is totally over my head. Is 20hz achievable with a 12" Dayton Classic Woofer or similarly priced one?
a driver facing your back would give you really nice tactile response vs doing a sonotube. I think it depends on whether you want the great tactile response of a near-field subwoofer.

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post #13 of 81 Old 02-15-2019, 12:36 AM
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I use Peerless SDF-250F75PR01-06 10-inch woofer in a 1.25 cubic feet. It's responsive, very low distortion, tactile, and easy to integrate. In my setup it becomes invisible. It does bottom out easily, so I suggest keep Xmax under 10 mm. I used miniDSP to set a 2nd-order highpass Butterworth filter at 35 hertz. The amplifier that I'm using is BASH 300S. It may fit in your room, but it will overshoot your budget.

If putting Peerless SDF-250F75PR01-06 in a vented box, a 3.0 cubic feet and tuned around 23.6 Hertz. It will need a 26 hertz high-pass filter. The wattage that it can handle is 500 watts, but I suggest 300 watts. The F3 is 23 hertz.

The Dayton Audio DCS305-4 in a 3.47 cubic feet and tuned at 26 hertz will be louder than the Peerless, but its F3 is not quite as good at around 26 hertz. The DCS305-4 requires a high-pass filter at around 30 hertz. 300 watts is it's maximum.

The F3 is based on anechoic chamber room. It's not in-room response. In room response may go lower and be louder.

The amount of room that is required for the woofer is half the diameter. If you don't, the air between the couch and the woofer will act like additional mass to the cone and this will change the parameters of the woofer thereby change the vented alignment.

I haven't heard Dayton Audio Classic woofers, but I have heard Dayton Audio Ultimax and Peerless SDF-250F75PR01-06. I prefer the sound of Peerless SDF-250F75PR01-06. The Dayton Audio DCS305-4 has good SPL/frequency response to price ratio, but I don't know its audio accuracy. To me Peerless SDF-250F75PR01-06 audio accuracy is superb. The choice been $150 for superb audio accuracy versus $77 for questionable audio accuracy.
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post #14 of 81 Old 02-15-2019, 05:46 AM - Thread Starter
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Quote:
Originally Posted by Craig S King View Post
Does the back of your couch angle in towards the wall? Meaning, is it more than 6" from the wall at the base? And then at 17" tall, the couch is 6" away from the wall?
Yes you are exactly right. So with an angled box I could go bigger with only 6 inches at the top. Although it would make calculating volume way over my head.

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post #15 of 81 Old 02-15-2019, 05:53 AM - Thread Starter
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Originally Posted by Zarkoff500 View Post
I wouldn't say tons of experience but a little Thank you for the kindness either way. My CS1214 turned out a little lower than 20 hz and to my ears sounds pretty good. The tactile from down firing is a bonus.
I found that driver in WiniSD. If the numbers are accurate it appears better than the Dayton Classic 12" and a little below the Dayton Reference 12". All while being cheaper than both. What size box got you to 20hz? Also, how do I begin to figure out the port size and length? Nothing seems to change the curve when I change though numbers in the program.

@Zarkoff500

Edit: Added some photos of where I'd like to put this. So 6 inches at the top wouldn't be bad, then at the bottom I could go to almost 10" out.
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post #16 of 81 Old 02-15-2019, 07:44 AM
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I have a void just like that, but with a lot more room. I made a smaller box first with 4 12's and then a much bigger set with 4 18's. Links to the build thread below for some inspiration for you!

Version 1:
https://www.avsforum.com/forum/155-d...eld-setup.html

Version 2:
https://www.avsforum.com/forum/155-d...ld-thread.html
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post #17 of 81 Old 02-15-2019, 08:11 AM
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Adjusting port size and length does nothing to the SPL graph.... however it does TONS to the Rear Port - Air Velocity graph.

You want that number to NOT go above 20, and the lower you can get it the better.


PS the parts to look at are "Max SPL", "SPL", "Cone Excursion", and "Rear Port - Air Velocity".
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post #18 of 81 Old 02-15-2019, 08:12 AM
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Quote:
Originally Posted by CheapSpeakerGuy View Post
I found that driver in WiniSD. If the numbers are accurate it appears better than the Dayton Classic 12" and a little below the Dayton Reference 12". All while being cheaper than both. What size box got you to 20hz? Also, how do I begin to figure out the port size and length? Nothing seems to change the curve when I change though numbers in the program.

@Zarkoff500

Edit: Added some photos of where I'd like to put this. So 6 inches at the top wouldn't be bad, then at the bottom I could go to almost 10" out.
Don’t forget your base molding will eat up some of that 10” at the bottom...
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post #19 of 81 Old 02-15-2019, 08:42 AM
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Quote:
Originally Posted by CheapSpeakerGuy View Post
I found that driver in WiniSD. If the numbers are accurate it appears better than the Dayton Classic 12" and a little below the Dayton Reference 12". All while being cheaper than both. What size box got you to 20hz? Also, how do I begin to figure out the port size and length? Nothing seems to change the curve when I change though numbers in the program.

@Zarkoff500

Edit: Added some photos of where I'd like to put this. So 6 inches at the top wouldn't be bad, then at the bottom I could go to almost 10" out.
My cab was approximately 3.5 cft and about 22x20. I started with a full sized 4" Precision Port and cut about 1.5" of the length off to give the end about 2" from the back baffle. @LTD02 gave guidance on figuring out the length.

Last edited by Zarkoff500; 02-15-2019 at 11:33 AM.
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post #20 of 81 Old 02-15-2019, 11:22 AM - Thread Starter
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Originally Posted by Zarkoff500 View Post
My cap was approximately 3.5 cft and about 22x20. I started with a full sized 4" Precision Port and cut about 1.5" of the length off to give the end about 2" from the back baffle. @LTD02 gave guidance on figuring out the length.
Maybe a stupid question, but is the length of the port based on the total cubic feet regardless of the design or is the port length based on the dimensions of the box? i.e. a 4.0 cubic foot box that's a square vs. a rectangle, same length and size port?
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post #21 of 81 Old 02-15-2019, 11:30 AM - Thread Starter
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Quote:
Originally Posted by Raylon View Post
I have a void just like that, but with a lot more room. I made a smaller box first with 4 12's and then a much bigger set with 4 18's. Links to the build thread below for some inspiration for you!

Version 1:
https://www.avsforum.com/forum/155-d...eld-setup.html

Version 2:
https://www.avsforum.com/forum/155-d...ld-thread.html
Now this is what I'm talking about. Those 18's.................man they bring a tear to my eye.

So.....take what you did and divide by about 10, haha.

Anyway, something I pondered was, if I see that I need 4.0 cu feet lets say for a 12" woofer. If I put in 2 - 12"s do I need 8.0 cu ft? To my eye, your first build did not have quadruple the cubic feet but it had 4 woofers. Does having multiple woofers in one box change the required cubic feet? I ask because maybe having 2 or 3 12's behind all of the seats of the couch would ROCK.
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post #22 of 81 Old 02-15-2019, 11:43 AM
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Help with DIY behind the couch subwoofer box

Raylons box is built to provide each driver around 1.4cf for a combined 6cf....

It works well with the JBLs..... how do I know?


......because I bought it from him and the switched drivers .

I’ve been using it for a few years now and love it.


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post #23 of 81 Old 02-15-2019, 11:43 AM
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Port length will be determined by driver and box size, shape isn't as important unless the port end is close to baffle/side as this may effectively change the port length (like the VBSS where the end of the port is close to the back of the cabinet and the functional length of the port is increased).

And you are correct that every increase in driver number should increase box volume assuming the box is approximately the correct size for one driver at the required tuning/performance parameters.

You can play around with this in Winisd to get an idea.
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post #24 of 81 Old 02-15-2019, 06:39 PM
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I'm considering a behind-the-couch sub build as well.
I've got 24 cu.ft. to play with though.
Am considering four entry-level 12" subs for my current budget.
Right now, I have a single TC Sounds 12" in 3.5 cu.ft. tuned to 26hz.
I love the feel and fact that it doesn't really seem like it's behind my back unless I pay focus on it.
Actually, the feel won me over. I've had four high end 15's in vented enclosures at the rear of my room.
THT and Danley DTS-20 in the front of the room.

On a budget build though, you just can't beat that tactile behind-the-couch feel.

Tactical Sub

"The boom is dead, long live the bass"
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post #25 of 81 Old 02-15-2019, 09:53 PM - Thread Starter
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Would trying to make this a two driver box really improve things, if I put the woofers at opposite ends of the box? Would this really help distribute the sound in the room? I understand the concept of two woofers blending the sounds and keeping it consistent across the room, I believe that is for two woofers on opposite ends of the room as opposed to two in the same box.

Can someone lie to me and tell me a 300 watt amp, tuned to 20 hz, ported, with one 12" JBL 1214, will be better than the PS-1000?

@EndersShadow - is your box sealed? Is that how you get away with 1.4 cu ft per driver?

Messing with the port on winisd doesn't seem to do anything to the curve?

I should restate this is a 1500 cubic foot room.

70% Movies/Shows 30% Music, is tuning to 20 hz smart, assuming I can fit it?

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post #26 of 81 Old 02-16-2019, 07:10 AM - Thread Starter
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Here is a better visual of what I was thinking. I am now toying with the idea of possibly making this a trapizod however, which would allow me to go narrower on top and long on box. Top depth ~7 inches, bottom depth 9ish.

@EndersShadow When I look at the Rear Port Velocity Graph the 20 is on the y axis and therefore no matter what something goes past it. Is it the "bump" that I don't want to go past the 20? Picture attached.




If I knew in my car audio days that I'd be using excel/calculators/rear port velocity measures I would have called myself OLD!
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post #27 of 81 Old 02-16-2019, 07:26 AM
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Help with DIY behind the couch subwoofer box

20 on the vertical axis. The horizontal is showing frequencies so it will always hit 20.

You want the graph to show from 100hz to maybe 10 (so it covers all they way below port tune).

My box is sealed which is how I get away w a small box.

I’m slowly putting together a system that will have 12 of the JBLs so I went sealed to keep box sizes small.

I’d try that same box with say 4 drivers and see how the SPL look...


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post #28 of 81 Old 02-16-2019, 08:06 AM
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Help with DIY behind the couch subwoofer box

If you are dead set in the 300 watt plate amp, then stick w one JBL. It’s darn near a perfect match to that box. You need 2 ports, 4” in diameter, 35” long each. Max velocity is 14m/s at 18hz which means no port chuffing. 2nd order highpass at 20hz.

I just graphed out some other options and if you aren’t getting an external amp it’s not worth it.

If your looking at external amps, then I suggest one of the following:

Alternate ported option:

2 JBLs in that box, tuned to 25hz, 3 4” ports, 33” long each. Can handle up to 750 watts combined before problems. Max velocity is 15m/s at 22hz. 2nd order highpass is at 22hz.

If the box can be taller, increasing cubic footage, the port tune, and high pass filter can be lowered, increasing SPL. 6cf seems a pretty good compromise, but sealed still beats it.

Best option

4 JBLs in that box... SEALED.....Can handle up to 2k combined w ease. You can always start w a low powered external amp and go from there.

Here are the charts. I’m too lazy to upload them as screenshots so I’m gonna take pics in my phone as it’s 10x easier lol. You can build the WinISD models yourself to see it better anyway .

Black is the 4 sealed
Pink is the dual JBL
Red is the single JBL

SPL


Cone Excursion


Port velocity



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Quote: There exists, for everyone, a sentence - a series of words - that has the power to destroy you. Another sentence exists, another series of words, that could heal you. If you're lucky you will get the 2nd, but you can be certain of getting the 1st. - Philip K. Dick

Last edited by EndersShadow; 02-16-2019 at 08:14 AM.
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post #29 of 81 Old 02-16-2019, 06:12 PM - Thread Starter
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Quote:
Originally Posted by EndersShadow View Post
If you are dead set in the 300 watt plate amp, then stick w one JBL. It’s darn near a perfect match to that box. You need 2 ports, 4” in diameter, 35” long each. Max velocity is 14m/s at 18hz which means no port chuffing. 2nd order highpass at 20hz.

I just graphed out some other options and if you aren’t getting an external amp it’s not worth it.

If your looking at external amps, then I suggest one of the following:

Alternate ported option:

2 JBLs in that box, tuned to 25hz, 3 4” ports, 33” long each. Can handle up to 750 watts combined before problems. Max velocity is 15m/s at 22hz. 2nd order highpass is at 22hz.

If the box can be taller, increasing cubic footage, the port tune, and high pass filter can be lowered, increasing SPL. 6cf seems a pretty good compromise, but sealed still beats it.

Best option

4 JBLs in that box... SEALED.....Can handle up to 2k combined w ease. You can always start w a low powered external amp and go from there.

Here are the charts. I’m too lazy to upload them as screenshots so I’m gonna take pics in my phone as it’s 10x easier lol. You can build the WinISD models yourself to see it better anyway .

Black is the 4 sealed
Pink is the dual JBL
Red is the single JBL

SPL


Cone Excursion


Port velocity



Sent from my iPhone using Tapatalk

-Well say that I got a 500w plate amplifier, would you then suggest the 2 jbls with a port?
-That'll substantially increase the size of the box though correct, don't think that's an option. Past say 80 inches and the box is wider than the couch, the WAF goes out the window!
-What kind of wattage would you suggest for the 4 in a sealed box?
-Here is a photo with a template cut out of 6" top, 10" bottom, 17" high. It's close.
-Would one of the Dayton plate amps with DSP help things or is the Sub EQ in an AVR sufficient?

Looking at these:
https://www.parts-express.com/dayton...-dsp--300-8010
https://www.parts-express.com/bash-3...w-rms--300-750
https://www.parts-express.com/dayton...ifier--300-803
https://www.parts-express.com/yung-s...boost--301-508

I really appreciate all the help. I picked up a 3/4 MDF board today and ordered 1 JBL last night. Heavy.
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post #30 of 81 Old 02-16-2019, 06:36 PM
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Help with DIY behind the couch subwoofer box

1. A single sub as configured only can take 325 watts before having issues. Meaning....

500 watt amp = 2 drivers.

2. I was talking about the height. Seems like you have a couple more inches up too you could use. The larger the box for 2 drivers the better.

3. If going with 2 JBLs You will need something with DSP. The highpass should be 23 which is higher than what most plate amps do (20hz). If you stick with one, then no need as it will have a built in highpass right where you want it.

4. The sealed box will take up to 2k watts before having issues. Meaning buy what you can now power wise knowing you could do more later.

With sealed you also don’t need to worry about highpass filters, so DSP isn’t “needed” (though most of us are using a shelf filter to bring up the bottom end). But you could go without to see how you like it.


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Quote: There exists, for everyone, a sentence - a series of words - that has the power to destroy you. Another sentence exists, another series of words, that could heal you. If you're lucky you will get the 2nd, but you can be certain of getting the 1st. - Philip K. Dick
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