The Dually Mammoth - D.O. HT-18v2 - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 31 Old 09-30-2017, 09:09 PM - Thread Starter
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Cool The Dually Mammoth - D.O. HT-18v2

I have been into home theater for many years and have gone through a plethora of consumer products from cheap $25 Sony bookshelves to decent Polk mains. The most expensive consumer subwoofer I owned and still use in a different setup is a Rythmik LV12R. For almost 600 bucks I was never really impressed with the output, dynamics or quality of sound even after tedious tweaking. We sealed it, bypassed the silly servo technology, EQ'd the heck out of it and it still never gave me what I was looking for out of a subwoofer. Especially after experiencing @bossobass subs in person...

Thanks to this forum and @Shreds I decided to go the DIY route as it is cheaper and more efficient. Man, did that prove to be true with the monster we have built here. From this day forth I will probably never buy consumer products again. DIY is certainly the way to go for me. It took some time and elbow grease but I now have a subwoofer that trumps any consumer sub even close to what I paid for the materials, drivers and amp. This dual 18" setup was discussed and debated for years before I finally decided to pull the trigger. The trigger was when the new HT-18v2's from Stereo Integrity were released at $149 each! I immediately bought 2 and got the ball rolling. I have to give a huge thanks to Nick at Stereo Integrity for the incredible deal and awesome customer service. The quality of these drivers are top notch and as he told me, nowhere on the market can you find this much displacement for the dollar. @Electrodynamic

Now that the project is complete I can say I am finally satisfied with my subwoofer setup. In my small living room I couldn't ask for more. The output, dynamics and response is incredible. It has made me re-watch most of my collection of music and movies in a whole new light. This new setup has given me a much more immersive experience with everything I play. I now know what ULF truly means and how important it is for immersing yourself in whatever material I am watching/listening to. I have to give a huge shout out to @Shreds for helping me build the enclose and @bossobass for the design.

More pictures of the completed project and videos of excursion measurements will be coming soon.

Breakdown of the cost of the entire system including the amp.


The cabinet uses 1-1/2 pieces of MDF with minimal cuts due to leaving the 4 foot side alone for all of the sides of the box. The internal volume comes to 13.72 cubic feet and after drivers and braces comes to about 12 cubic feet.


WinISD model of both HT-18's sharing 12 cubic feet:


Excursion graph using iNuke 6000DSP as the amp:


Close mic average of top and bottom drivers in the middle of the room:


Cabinet was assembled with no fasteners:




Listening position response with mains (mic used was the UMM-6 so measurement isn't too accurate much below 20Hz):
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post #2 of 31 Old 09-30-2017, 09:27 PM
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If you posted WINISD graphs they are not showing. Edit I see now "More pictures of the completed project and videos of excursion measurements will be coming soon."

HTPC, Sony 40es, 120" Silver Ticket, 7702mkii, Sunfire Amp 225w, JBL 590, JBL 520

PSA XS30, Seaton Submersive, 2 Um-18 8cf sealed, Outlaw Ultra x 12, Kappa Pro 18LF, BFM Tuba 60 horn, B&C 18TBW100 6cf 41hz, 34hz, 28hz tune

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post #3 of 31 Old 10-01-2017, 12:13 AM - Thread Starter
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If you posted WINISD graphs they are not showing. Edit I see now "More pictures of the completed project and videos of excursion measurements will be coming soon."
Thanks @bscool for the heads up my mistake, check them now.
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post #4 of 31 Old 10-01-2017, 05:12 AM
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Nope. No completed pics showing yet though.
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post #5 of 31 Old 10-03-2017, 04:54 PM - Thread Starter
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Final Build Pics







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post #6 of 31 Old 10-04-2017, 01:09 PM
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Nice build, and nice setup! Are you happy with the sound? Any description (beyond the measurements above)?
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post #7 of 31 Old 10-04-2017, 01:31 PM - Thread Starter
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Quote:
Originally Posted by OJ Bartley View Post
Nice build, and nice setup! Are you happy with the sound? Any description (beyond the measurements above)?
Thanks! im a stickler about hiding wires and clean setups. Coming from ported consumer subs my entire life - yes I am definately happy with the sound. Movies are much more immersive now that I can actually go below 20hz... Everything just seems tighter and the dynamic range is what impresses me the most. My HT subwoofer is no longer a one note boomer in the corner. I can hear and feel a huge difference in light and hard rumbles/booms in movies. Before this setup all rumbles, bangs and even dialog were the same volume from the sub. I attribute these vast improvements mostly to the D.O. sealed setup. Plus the fact that I went from a single 300w ported 12 to two 18s powered by an iNuke 6k. I am quite aware of the huge controversy between ported and sealed for HT but @Shreds has made me a firm believer in sealed speakers overall - as long as you know how to build a proper enclosure and have the power plus dsp abilities to get it flat. The only downside to this new experience for me is that it really points out a crappy mix. There are some things I just can't watch anymore and a ton of movies that no longer impress me like they used to.
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post #8 of 31 Old 10-04-2017, 02:06 PM - Thread Starter
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I figured some of you may be interested in what other gear I am using for my HT setup. Most of my gear is budget stuff but it sounds incredible in my tiny living room.

Mains - BIC Venturi DV84's
Center - BIC Venturi DV62CLR-S
Surrounds - Polk Audio FXI A4's
Sub - Dually Mammoth! Refer to this thread...
Sub amp - iNuke 6k DSP
Separate amps for the mains, center and surrounds - Crown X1000's
DSP - Behringer 1124p's
Receiver - Denon AVR 3100w (primarily just for decoding and hdmi switching)

90% of the content played in my HT is from my main gaming/productivity/htpc computer through Jriver. If you want to know more about the PC, let me know. I may make a separate thread about that.

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post #9 of 31 Old 10-04-2017, 04:25 PM
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Looking at doing something just like this, where did you get the standoffs?

Sent from my VS990 using Tapatalk
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post #10 of 31 Old 10-04-2017, 06:58 PM - Thread Starter
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Looking at doing something just like this, where did you get the standoffs?

Sent from my VS990 using Tapatalk
Amazon

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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post #11 of 31 Old 10-04-2017, 06:59 PM
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I appreciate that, thank you.

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post #12 of 31 Old 10-04-2017, 07:02 PM - Thread Starter
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I appreciate that, thank you.

Sent from my VS990 using Tapatalk
No problem. Good luck! I'd love to see your build.
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post #13 of 31 Old 10-05-2017, 10:30 AM
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Nicely done!
Very clean look to it...
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post #14 of 31 Old 10-05-2017, 03:56 PM
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Cool looking rack..

definitely made me miss my old Behringer feedback destroyer.
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post #15 of 31 Old 10-05-2017, 07:16 PM - Thread Starter
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Cool looking rack..

definitely made me miss my old Behringer feedback destroyer.
Thanks, im loving the rack for sure. Cleans up a bit of the wires. The behringers definitely get the job done. They have a little noise but it's not that noticeable. I primarily use my computer in the HT as an input through HDMI so I'm thinking of getting the nanoAVR HD from miniDSP for more control. Plus, it's completely digital so I don't have to worry about as much a/d conversion.
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post #16 of 31 Old 10-11-2017, 10:46 AM
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Really nice build. How tall are those legs? 4"? Thinking about something like this for my build.

Thanks!

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post #17 of 31 Old 10-11-2017, 09:54 PM
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Arrow HT-18v2 Excursion Test...

iNuke 6k hooked to a dedicated 20A line powering 2 HT-18's sharing 12 cubes...

Will the amp clip before the driver hits xmax with a demanding movie scene with ULF? Who will tap first, the amp or driver?




Rated Xmax on the HT is 22.5mm. I rigged up some 10 gauge solid core romex just above the dust cap of the driver measured precisely to 23mm. Only the sub was run so we could listen for signs of driver distress as we looped the scene and eased the volume up. Test scene is in TIH where Hulk punches Abomination into the pavement:


The main hit is centered at 9Hz with strong signal spread from 5-18Hz.





As you can see, the driver never hits 23mm but it comes darned close! As near as I could figure, we're talking under a mm of clearance in the video.

At the end of the hit you can hear what sounds like the former knocking against the backplate but this is actually the amp just starting to clip by .5dB. The sound of the clipping gets more intense as volume is increased and for those who don't know, can easily be confused with bottoming out the driver.

Conclusion: it would seem that 2 HT-18's in 6 cubes each and an iNuke 6k on a 20A line are well matched to each other. Note: this was with perfectly dialed in gain stages that don't clip the signal before the amp and the amp had a low shelf boost of +4dB for the sealed enclosure. So YMMV, don't go nuts and crank just any scene up to reference with a low shelf boost of +12dB and think that you're safe just because you have this combo.

Performing this test after you measure, EQ and calibrate is easy and it will show you where the limits of your system are. Use a worst case scenario scene with ULF (sealed) on a reasonably hot output soundtrack.
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post #18 of 31 Old 10-12-2017, 05:42 AM
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Quote:
Originally Posted by Shreds View Post
iNuke 6k hooked to a dedicated 20A line powering 2 HT-18's sharing 12 cubes...

Will the amp clip before the driver hits xmax with a demanding movie scene with ULF? Who will tap first, the amp or driver?




Rated Xmax on the HT is 22.5mm. I rigged up some 10 gauge solid core romex just above the dust cap of the driver measured precisely to 23mm. Only the sub was run so we could listen for signs of driver distress as we looped the scene and eased the volume up. Test scene is in TIH where Hulk punches Abomination into the pavement:


The main hit is centered at 9Hz with strong signal spread from 5-18Hz.





As you can see, the driver never hits 23mm but it comes darned close! As near as I could figure, we're talking under a mm of clearance in the video.

At the end of the hit you can hear what sounds like the former knocking against the backplate but this is actually the amp just starting to clip by .5dB. The sound of the clipping gets more intense as volume is increased and for those who don't know, can easily be confused with bottoming out the driver.

Conclusion: it would seem that 2 HT-18's in 6 cubes each and an iNuke 6k on a 20A line are well matched to each other. Note: this was with perfectly dialed in gain stages that don't clip the signal before the amp and the amp had a low shelf boost of +4dB for the sealed enclosure. So YMMV, don't go nuts and crank just any scene up to reference with a low shelf boost of +12dB and think that you're safe just because you have this combo.

Performing this test after you measure, EQ and calibrate is easy and it will show you where the limits of your system are. Use a worst case scenario scene with ULF (sealed) on a reasonably hot output soundtrack.
A lot of dual opposed SI18's in here nowadays : Nice job on these

Cool test, Shreds. Any idea how it would go with 9.2 ft3 volume instead of 12 ?

Dual Atmos Receivers - Atmos 13.1.8/DTS X 9.1.8/Auro 3D 13.1 - Denon AVCX8500H+AVRX7200WA - Klipsch+KEF - 6xSI18" - 8xJBL 12" BOSS - 4xJBL 12" w/SLAPS M12" VNF - 3x2 stacked Crowson MA - 4xBK-LFE - 6xNU6K(fan&trig mod) - Minidsp 10x10HD - Oppo UDP203 - XBox OneX - Apple TV4K - JVC RS600 Dreamscreen V2 120"- Philips 65OLED873.
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post #19 of 31 Old 10-12-2017, 08:53 PM
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Quote:
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A lot of dual opposed SI18's in here nowadays : Nice job on these

Cool test, Shreds. Any idea how it would go with 9.2 ft3 volume instead of 12 ?
You'll have a sharper peak at ~45Hz and lose a bit of output down low. You won't be able to hit the xmax of the driver without sending the coil too much power but you're only talking a few mm less than with a larger cab, not that big of a deal SPL wise.

The main thing to consider is you're sharing 1 inuke 6k with 4 drivers if I'm not mistaken? You would have to wire the subs up so that you run the nuke stereo into 8 ohms right? Well I wouldn't be surprised if you were getting less than 400W to each driver when the amp is maxed at low frequency scenes. Yeah, yeah, I know the guy on youtube with the dyno @1kHz shows bla bla... Look at this test. With a bigger box and two drivers, it soaked everything a 6k nuke had on a 20A dedicated line and still didn't hit xmax with real world content.

Hey maybe your room is small enough or you listen at low enough levels that it doesn't matter and you'll be happy with how it is but if you're pushing the amp near it's limit for ULF transients, I'd say double the power to the drivers.

Again though, nice job on your build.
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post #20 of 31 Old 10-21-2017, 01:14 PM
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I absolutely love this build! It has me thinking I might need to give this a try sometime soon! I have seen a couple of the sono tube threads and was considering trying to build one, but this looks like a winner. I have just enough woodworking skills to pull something like this off!

I have a couple of questions. I notice that you don't have much in the way of internal bracing. Does that cabinet vibrate? That has been a concern when considering the sono tube.

Another question: How did you determine the length of the feet you used? Is there a formula for determining this?

How do you wire the 2 subwoofers?

Do you have to run one subwoofer out of phase with the other?

Please excuse these these questions if the answers are already out there.

Thank you,

Tom
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post #21 of 31 Old 10-21-2017, 02:23 PM
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Quote:
Originally Posted by 4anaudionut View Post
I have a couple of questions. I notice that you don't have much in the way of internal bracing. Does that cabinet vibrate? That has been a concern when considering the sono tube.

Another question: How did you determine the length of the feet you used? Is there a formula for determining this?

Do you have to run one subwoofer out of phase with the other?
The cabinet's resonance is somewhere around 400-500Hz, which isn't a problem for sub duty. The bracing is minimal and only single baffles used but as you can see in the excursion video, the wire used to measure excursion didn't move when the drivers were almost at full stroke and it was attached to one of the feet of the cab. That being said, a cylinder is hard to beat for strength but either way you go, you won't be able to measure a difference in SPL, distortion or response once your sub is calibrated. If very high excursion drivers with a lot more power were being used, we would have used more bracing.

No formula to the feet, just keep the bottom driver off the ground enough so the surround doesn't touch the floor (especially on carpet) and the driver has room to breath.

Wire the 2 drivers the exact same so that they "oppose" each other.
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post #22 of 31 Old 10-21-2017, 03:58 PM
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I asked almost the same question when I built my DO w/ the HST18's, Shreds suggested I look up the Xmax of the driver which I did and I also looked at what type of feet to use on Amazon and E-Bay. Theses feet are stainless 2"dia. and 5" tall even with spirited playing I still have room to spare. I am not implying that I blast the heck out of but depending on the material ( Hacksaw Ridge in my case during some of the battle scenes ) my subs will move almost 2". I think they can take a little more but at that level its nuts so why bother. Another thing with those feet they will take the weight w/ 2 HST18's plus the box my guess it must be close to 250 300lbs. Plus for 20.00 figured why not?

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post #23 of 31 Old 10-21-2017, 03:58 PM
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Shreds,

Thank you for the information! I have to finish a couple of other projects before I try these!

Thanks again,

Tom
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post #24 of 31 Old 10-21-2017, 04:17 PM
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Cichlid109,

If/when I build a couple of these, I am going to use black pipe for the legs. They will match the homemade speaker stands that I am in the process of building right now. I think I'll make the legs at least 5 inches tall.

I agree, I don't want the sub to smack the top or bottom boards when hitting xmax. That would be a bad thing.

Currently, I am building two 4 cubic ft sealed enclosures for a pair of HT-18v2's. They will be used for the stereo set up in the family room. It's taking me forever to finish them. I am a bit of a hack when it comes to woodworking projects. I keep telling myself its fun. The subwoofer drivers are sitting on the work bench right now. Looking forward to testing these soon. If they sound good, I think I'll start on one or two of these dual opposed boxes for the man cave home theater.

Thx,

tom
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post #25 of 31 Old 10-23-2017, 11:31 AM
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Quote:
Originally Posted by Shreds View Post
No formula to the feet, just keep the bottom driver off the ground enough so the surround doesn't touch the floor (especially on carpet) and the driver has room to breath.
.
Two things i remember when searching this subject (formula for feets) before i started my project was a couple of post from your dad discussing this, and he mentioned that everything from 0.5 to 1.0 X Sd regarding free opening between the driver and endplates/floor. I believe he said he used 1.0x Sd.

Also someone in some other thread mentioned that the free opening made it behave like a bandpass.

Can't remember or find these threads again, but does any of this ring a bell?

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post #26 of 31 Old 10-23-2017, 01:21 PM
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I have been reading this thread since I have a similar build using the HST 18's why would you need a formula for figuring out how long the feet have to be? I am not trying to be ignorant just this makes no sense if you know the max excursion of the driver or if you do not you can rig up some wire and run some bass heavy material watching how far the driver moves. My HST's will move approx. 2" and I am not comfortable when they are doing that but the feet I use are approx.4" from the base of the leg to to the end plate. I have never had any problems really just wondering why you would need a formula unless your trying to get max. effect?? Really just curious.

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post #27 of 31 Old 10-23-2017, 04:27 PM
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My experience with subwoofers is limited. Any and all subwoofers that I have just have the driver pointed straight ahead, with nothing interfering with the signal. I don't have any experience with a subwoofer with a board stuck in front of the driver. I didn't know if there is some magical formula for calculating the distance. Obviously, you want the board to be far enough so the woofer doesn't smack it when reaching xmax. I just figured I would ask instead of wasting my time building a piece crap that didn't work.

Unfortunately, I have a pattern of doing everything twice. I aways manage to screw something up the first time. Eventually it always works out in the end. Just trying to cut down on the things that I can screw up.
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post #28 of 31 Old 10-23-2017, 04:32 PM
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Nalleh,

Thank you for the reply. I think your dual opposed subwoofers are gorgeous.


thanks,

tom
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post #29 of 31 Old 10-23-2017, 04:35 PM
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Quote:
Originally Posted by Cichlid109 View Post
I have been reading this thread since I have a similar build using the HST 18's why would you need a formula for figuring out how long the feet have to be? I am not trying to be ignorant just this makes no sense if you know the max excursion of the driver or if you do not you can rig up some wire and run some bass heavy material watching how far the driver moves. My HST's will move approx. 2" and I am not comfortable when they are doing that but the feet I use are approx.4" from the base of the leg to to the end plate. I have never had any problems really just wondering why you would need a formula unless your trying to get max. effect?? Really just curious.
I found the thread i was talking about. «Air spring distortion» is the subject her. Read @bossobass comments a bit down in this thread :

http://data-bass.ipbhost.com/topic/1...quad-si-ht18s/

If i am not mistaking, you @Shreds did the test with and without the top endplate, and measured ~ 1dB more WITH the plate than without. With 2.. 4...8 drivers, that ads up.

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Last edited by Nalleh; 10-23-2017 at 05:19 PM.
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post #30 of 31 Old 10-23-2017, 05:16 PM
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Nalleh,

Thank you for the link. I'll check it out.

- tom
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