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-   -   Dual 18” ported Subwoofer design (https://www.avsforum.com/forum/155-diy-speakers-subs/3048560-dual-18a-ported-subwoofer-design.html)

superkyle 02-05-2019 03:49 PM

Dual 18” ported Subwoofer design
 
All,
I finished my second build and man have I caught the DIY bug. Next on my list I really want to try and build a dual 18” ported sub design. I downloaded winisd and played around but when it got into the order of boxes etc I go lost. Can someone let me know if it’s possible to build a dual 18” box with sufficient output over a single 18” box with the dimensions around say 23” depth 41.5” tall and 24” wide. It seems by my playing around that adding the second sub actually causes less output which may be true but would love someone else to verify if possible.


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aron7awol 02-05-2019 04:02 PM

Are you using the Maximum SPL chart? That's the best way to see excursion and power limited output across the whole range, without having the change power and HPF while settling on a volume and tuning. Then once you settle on that, you can enter power and a HPF to model whatever you're planning for amp and check excursion and port velocity, change HPF and/or port size as necessary.

smcmillan2 02-05-2019 04:04 PM

What drivers are you planning to use?

superkyle 02-05-2019 04:05 PM

Quote:

Originally Posted by aron7awol (Post 57556260)
Are you using the Maximum SPL chart? That's the best way to see excursion and power limited output across the whole range, without having the change power and HPF while settling on a volume and tuning. Then once you settle on that, you can enter power and a HPF to model whatever you're planning for amp and check excursion and port velocity, change HPF and/or port size as necessary.



Yes I am ask ally single sub output is showing properly but when I change to dual drivers the output at the low end Drops off the map even if I double the power output. Now take everything with a grain of salt bc i have been reading and teaching myself how to use it but for the most part seems straight forward except they 4th order etc box which I believe is a standard ported box no?


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superkyle 02-05-2019 04:07 PM

Dual 18” ported Subwoofer design
 
Quote:

Originally Posted by smcmillan2 (Post 57556276)
What drivers are you planning to use?



Depends really. If possible I would like to keep to the same driver as my other builds using the UXL-18. It if I can’t find them then I would is the UM18-22. Or maybe I’ll hold off for the new high excursion driver I hear is coming out lol



For my model I was using the uxl-18 though

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superkyle 02-05-2019 04:12 PM

I will say I don’t see many Marty designs using dual subs so like I said I may be doing it correctly and it just doesn’t work but I do have a free channel in my Amp that’s begging to be used so figured I would at least try. Plus in the end it’s more cones!


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aron7awol 02-05-2019 04:15 PM

Quote:

Originally Posted by superkyle (Post 57556280)
Yes I am ask ally single sub output is showing properly but when I change to dual drivers the output at the low end Drops off the map even if I double the power output. Now take everything with a grain of salt bc i have been reading and teaching myself how to use it but for the most part seems straight forward except they 4th order etc box which I believe is a standard ported box no?


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If you are using the Maximum SPL chart then changing power shouldn't change anything.

You are modeling a vented sub in WinISD, right?

4th order bandpass is different from a vented (ported) sub, in that the back wave of the driver is sealed and the front wave going into a ported enclosure, as opposed to the vented sub where the front wave goes into the room and the back wave goes into a ported enclosure.

superkyle 02-05-2019 04:19 PM

Quote:

Originally Posted by aron7awol (Post 57556362)
If you are using the Maximum SPL chart then changing power shouldn't change anything.



You are modeling a vented sub in WinISD, right?



4th order bandpass is different from a vented (ported) sub, in that the back wave of the driver is sealed and the front wave going into a ported enclosure, as opposed to the vented sub where the front wave goes into the room and the back wave goes into a ported enclosure.



Ok good to know I appreciate the help and explanations. I must be using SPL and not max spl bc I was able to adjust the levels based on input power. I’m actually away from the computer that I have it installed on but can post some screen grabs and post them up.


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aron7awol 02-05-2019 04:20 PM

Quote:

Originally Posted by superkyle (Post 57556338)
I will say I don’t see many Marty designs using dual subs so like I said I may be doing it correctly and it just doesn’t work but I do have a free channel in my Amp that’s begging to be used so figured I would at least try. Plus in the end it’s more cones!


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That is because the Marty is just big enough to have a really nice shape to the Max SPL with a single UM18 or similar. If you double the drivers, you need to double the volume of the box to maintain that shape. At that point, it's better to do two Martys IMO. In the single box, the second driver doesn't really gain you much down low where you need more output the most.

aron7awol 02-05-2019 04:22 PM

Quote:

Originally Posted by superkyle (Post 57556384)
Ok good to know I appreciate the help and explanations. I must be using SPL and not max spl bc I was able to adjust the levels based on input power. I’m actually away from the computer that I have it installed on but can post some screen grabs and post them up.


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Yeah, that's the nice thing about the Max SPL graph. You don't have to adjust power or check excursion as it maximizes both for you. Just note it uses the power handling from the driver parameters.

superkyle 02-05-2019 04:22 PM

Dual 18” ported Subwoofer design
 
Quote:

Originally Posted by aron7awol (Post 57556388)
That is because the Marty is just big enough to have a really nice shape to the Max SPL with a single UM18 or similar. If you double the drivers, you need to double the volume of the box to maintain that shape. At that point, it's better to do two Martys IMO. In the single box, the second driver doesn't really gain you much down low where you need more output the most.



Yeah that is my worry. Basically since this is not a dedicated theater room it was very quickly shot down at the thought of adding an additional woofer that is not in the same enclosure.


As you may remember since you were so helpful in my other thread my room is fairly large and open floor plan so takes quite the bass to fill. It sounds great now flat loud and rattles the walls but I want more!! But mainly I would like to reduce the effort of each of the subs and this was my idea lol

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aron7awol 02-05-2019 04:34 PM

Quote:

Originally Posted by superkyle (Post 57556400)
Yeah that is my worry. Basically since this is not a dedicated theater room it was very quickly shot down at the thought of adding an additional woofer that is not in the same enclosure.


As you may remember since you were so helpful in my other thread my room is fairly large and open floor plan so takes quite the bass to fill. It sounds great now flat loud and rattles the walls but I want more!! But mainly I would like to reduce the effort of each of the subs and this was my idea lol

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What are your current subs tune(s)?

superkyle 02-05-2019 04:36 PM

Quote:

Originally Posted by aron7awol (Post 57556448)
What are your current subs tune(s)?



Rythmik I think is 12.5
DIY UXL-18 is 18 or 17 can’t quite remember but somewhere right there.


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aron7awol 02-05-2019 04:44 PM

How did you go about integrating the two subs? Are they summing constructively at your seating?

superkyle 02-05-2019 04:52 PM

Quote:

Originally Posted by aron7awol (Post 57556492)
How did you go about integrating the two subs? Are they summing constructively at your seating?



Gain matched then ran sweep of one and sweep of the other. Ran sweep combined and looked for any portions of the graph below either of the single sweeps. Adjust the phasing of one of the subs until cancelations/valleys are as eliminated as possible. Once complete I then EQed it flat which took off about 10db total output due to a 8-10db null. Apply EQ and then reduce gain to allow Audyssey to run then use subwoofer distance tweak to allow smooth transition at crossover.

That’s the jist of it haha


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johnson636 02-05-2019 04:55 PM


superkyle 02-05-2019 05:04 PM

Quote:

Originally Posted by johnson636 (Post 57556550)



Wow that is one heck of a sub. Super impressive. I think that is quite a bit out of the range of size I could get away with haha but man that is a good thread to hang on to so when I buy my next house I have something to shoot for haha. Appreciate it!


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aron7awol 02-05-2019 05:44 PM

Quote:

Originally Posted by johnson636 (Post 57556550)

Quote:

Originally Posted by superkyle (Post 57556588)
Wow that is one heck of a sub. Super impressive. I think that is quite a bit out of the range of size I could get away with haha but man that is a good thread to hang on to so when I buy my next house I have something to shoot for haha. Appreciate it!

Well, that thing is bigger than 2 Martys!

My subs are pretty much the size of 3 Martys each, and I only have a single HT18 in them. But they are so efficient at that size that even in a HUGE room with only two of them they give me clean reference level output all the way down through the teens, and if I give each of them 1200W at 11/12Hz, they will produce enough output to chuff their huge 10-3/8" diameter round ports. If I added an additional driver to each sub AND doubled the power, I'd only gain 2dB @ 11-12.5Hz, while chuffing a whole lot more. Of course, the second driver will add a whole bunch of output higher up (where you generally don't need it), but once you're hitting the limits of the port the only thing that can help you is more size (and thus a bigger port for the same tuning). There's no free lunch, but a huge ported box is some damn cheap lunch.

aron7awol 02-05-2019 05:51 PM

Just to give another example of what size does for ULF with ported, it would take 8 sealed 18s (and 8x the power) in 4cf each (32cf total) to match one of my ported subs with a single 18 in it @ 11Hz.

asarose247 02-05-2019 09:44 PM

4 Attachment(s)
Dual 18's ported, 40 x 28 x 18, inuke6K, 1 channel, wired for limited 1K 4 ohm load, designed for MBM range
PA 460-8
sits behind the 88 CC

and another work in progress, dual um-18's 23+ ft^3,
ported top part, 8" sonotube,
tuned for 14 hz

awaiting mancave ( i00 ft^2) mods before moving in and assembling
NX3000dsp, i channel per driver . .

hope it works . .

superkyle 02-06-2019 02:28 AM

Quote:

Originally Posted by asarose247 (Post 57557516)
Dual 18's ported, 40 x 28 x 18, inuke6K, 1 channel, wired for limited 1K 4 ohm load, designed for MBM range

PA 460-8

sits behind the 88 CC



and another work in progress, dual um-18's 23+ ft^3,

ported top part, 8" sonotube,

tuned for 14 hz



awaiting mancave ( i00 ft^2) mods before moving in and assembling

NX3000dsp, i channel per driver . .



hope it works . .



Haha that is one tall sub! I like the red and black as that is very close to what I am after but I would like to build it such that it has full output of two subs if possible (or as much as it could have in size box)


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superkyle 02-06-2019 06:27 AM

5 Attachment(s)
All,
Below are some screenshots of the box I was playing around with. As you can see the bottom end falls off with the dual sub.

Attachment 2521006 Attachment 2521008Attachment 2521010Attachment 2521012Attachment 2521014




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aron7awol 02-06-2019 06:32 AM

Quote:

Originally Posted by superkyle (Post 57558496)
All,
Below are some screenshots of the box I was playing around with. As you can see the bottom end falls off with the dual sub.

Attachment 2521006 Attachment 2521008Attachment 2521010Attachment 2521012Attachment 2521014




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You're still using SPL instead of Max SPL?

superkyle 02-06-2019 06:49 AM

1 Attachment(s)
Quote:

Originally Posted by aron7awol (Post 57558522)
You're still using SPL instead of Max SPL?



Yeah :/ I played around with it trying to figure out why I do not get a graph but didn’t see the issue. Here is what I get with max spl. I meant to explain that but I actually posted that while on conference call and got distracted haha.

Attachment 2521032


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aron7awol 02-06-2019 06:59 AM

Quote:

Originally Posted by superkyle (Post 57558598)
Yeah :/ I played around with it trying to figure out why I do not get a graph but didn’t see the issue. Here is what I get with max spl. I meant to explain that but I actually posted that while on conference call and got distracted haha.

Attachment 2521032


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Looks like you have Pe set to 0W in the driver parameters, that's why.

Change that to 1200W and re-load the Max SPL graph.

superkyle 02-06-2019 08:34 AM

1 Attachment(s)
Quote:

Originally Posted by aron7awol (Post 57558660)
Looks like you have Pe set to 0W in the driver parameters, that's why.



Change that to 1200W and re-load the Max SPL graph.



Yup that was it. Must have missed that in the guide I was following. Using the same net internal volume and tuning frequency of the single 18 and making it a dual sub looks like it adds a decent amount of volume. Maybe not worth the cost of buying another woofer but with a little tweaking of volume and tuning frequency maybe I can make it work and be worth it!

Attachment 2521084


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aron7awol 02-06-2019 10:23 AM

Quote:

Originally Posted by superkyle (Post 57559108)
Yup that was it. Must have missed that in the guide I was following. Using the same net internal volume and tuning frequency of the single 18 and making it a dual sub looks like it adds a decent amount of volume. Maybe not worth the cost of buying another woofer but with a little tweaking of volume and tuning frequency maybe I can make it work and be worth it!

Yeah, I'm not saying it's useless, it's just that the majority of the additional output is at 20Hz+ where I'm sure you already have tons of headroom with your existing subs.

superkyle 02-06-2019 03:26 PM

Dual 18” ported Subwoofer design
 
Quote:

Originally Posted by aron7awol (Post 57559786)
Yeah, I'm not saying it's useless, it's just that the majority of the additional output is at 20Hz+ where I'm sure you already have tons of headroom with your existing subs.



Yeah it is less than I expected for sure. Question though. They say when you integrate multiple subs you end up with around a 6db gain for each sub added. Would this yield half the same gain by adding it since it seems that the gain would be close to that 3db just not sure what that equates to when it goes to integration.


Edit: corrected gain for dual subs

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aron7awol 02-06-2019 03:42 PM

Quote:

Originally Posted by superkyle (Post 57561582)
Yeah it is less than I expected for sure. Question though. They say when you integrate multiple subs you end up with around a 3db gain for each sub added. Would this yield the same gain by adding it since it seems that the gain would be close to that 3db just not sure what that equates to when it goes to integration.

When integrating multiple identical subs, you gain 6dB for every doubling of subs. So, 2 subs is 6dB more than 1, but it takes another 2 to gain another 6dB going from 2 to 4. And then continuing on, another 4 just to gain 6dB. But remember, this is doubling drivers, power, and enclosure volume.

As for your case of adding a second driver to an enclosure (and doubling the power), WinISD is showing you basically the whole difference. You'll notice the increase is similar in the higher range where you are limited by the drivers, whether that's by power or excursion, and that makes sense since you are doubling the drivers and power (although not enclosure volume). However, the gain where the port has taken over is much smaller, because with any good-sized ported box and a single driver, you're already pushing that port hard and into compression and probably on the verge of or already chuffing. This might seem like a bad thing about a ported box, but really, it's just showing you the massive efficiency of a port, and that efficiency increases with enclosure size.

aron7awol 02-06-2019 03:49 PM

Is it possible for you to lengthen the port on your DIY sub and bring the tune down to the same 12.5Hz your other sub is at?


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