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698K views 6K replies 208 participants last post by  Red Five 
#1 · (Edited)
The number of Devastator versions and the number of documented Devastator builds is multiplying, it would be nice if some of this information were kept more neatly in one place. This thread is a work in progress. I will add new variants to this thread and also builds and link them below. :cool:

As always, in the pursuit of performance from the use of wood! Wood is still cheaper than amps and sub woofers.... Let's not forget the other part of the Devastator formula, simplicity! (remember we are dealing with a band pass here, they are more complicated). No diagonals, all panels are on right angles to simplify the building process.

Note: there are also some guides linked below in this post. If you have questions about how to assemble a Devastator, there is a lot of good information in the builds, do this and do not this. That is on top of the build guide. Basic assembly works its way from the top and front panels, towards the back and downwards. Top hatches, rear panel vents, high compression fronts and Stepped fronts have all be added as the Devastator has evolved. Items are listed for the most part in Chronological order. Several members have put a lot of time in documenting the build process. Please check out their build threads!

Want to design a Devastator all on your own? The Hornresp tutorial is posted below. If you have design questions feel free to post them in that thread! There are tools for helping design cabinets in Google Sheets posted in that thread too.

With the addition of the Stepped front Devastators, responses can be mostly flat natively. Knowing your room and what can fit in a space are going to be key factors for selection vs trying to leverage the response shape in spot the suites the box well.

Suggestions for box selection: Devastators have seen evolutionary progress as time has gone on. The biggest factor for selecting a Devastator is the space available. That is one of the main driving factors for the wide array of designs beyond achieving more performance from the use of building material. Room size is another big factor. (I grabbed this from Audioholics)

Room
Dimensional Volume
Small Room​
< 1,500 ft^3​
Medium Room​
1,500 ft^3 to 3,000 ft^3​
Large Room​
3,000 ft^3 to 5,000 ft^3​
Extreme Room​
> 5,000 ft^3​

Small room, you can probably get away with a couple Micro 15" Stepped V1s. Medium room, you will need a couple 18"s at least. Large room - 21"s. Extreme, how many Fat Boy V5s can your marriage take? Other factors, is the room open to other areas and is it an odd shape? That can mess with the equation especially if sub placement options are limited.

Why bass physics suck:

Below is the Fat Boy Version 5 with the native 22Hz tune in gray and I tweaked the vent area down so it is now tuned to 18Hz. As you can see from the graph output takes a huge 5db hit from the lower tuning. In room that 22Hz box will probably stick with all the other Index Devastators down to 17Hz or 18Hz. That is a bit room dependent, so your mileage may vary. Also, remember 6db is the equivalent of doubling your sub system, amps, boxes and sub woofers, 3db from cone area and box displacement and 3db from the input power doubling.

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Now I am going to push this further down to 15Hz tuning on the rear chamber. As you can see we are down a solid 10db on the left corner from the original 22Hz tuning and another 5db from the 18Hz tuning.

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The important thing to know? Each octave (dividing a given frequency by 2) you descend in frequency will require 4 times the displacement to achieve a given level of output. Let's say when tuned 20Hz a box can hit 88db on 1 watt of power with 1mm of excursion. If we tune the box to 10Hz it would take 4mm of excursion from the woofer to hit 88db. This is an important fact when selecting a Devastator. There are three factors that will come into play. Output, Extension and Cost, those factors will always have to be balanced. You can chose 2, but you cannot get all 3 unless you are in a very small space that gains very well. A 7000 cubic foot room on a concrete slab is not a good place to chase extension. It would be better to go with higher tuned cabinets and gain the wobble effect from a BOSS platform. Unless you have the luxury of unlimited budget.

High Pass Filter Orders:

Real quick rundown, 6db of slope is an order. For example a 2nd order Butterworth filter will knock the response down 12db per octave. If set to 20Hz the response will be down 12db at 10Hz, assuming it is applied to a flat line. 2nd order filters can make integration easier in certain circumstances. Especially if the cabinet tunes have a wider range than just a few Hertz. Integration with sealed cabinets can be more tiresome and require a lot of trial and error. An 8th order 48db per octave slope on the sealed cabinet and then using a 2nd order HPF a few Hertz over tune on the Devastator can be a good starting point. Once again YMMV. If you do plan on using a 2nd order filter, go a little over tune with the filter to control driver excursion below tune.

Order: (typically you will not see a Dev go over a 4th order, just keep multiplying by 6 to go up)
1st 6db per octave
2nd 12 db per octave
3rd 18db per octave
4th 24db per octave

Why do we need High Pass Filters on a Devastator?

Below the tuning frequency of the Low Frequency(LF) resonator cone excursion goes out of control(see example below). The cone is no longer seeing a load like it would above the tuning frequency of the LF resonator. The cone movement would be similar to the sub being given power in free air. A pro driver can take several hundred watts in most cases in free air when sent a low frequency waveform. Doing that to a woofer frequently could A. damage the woofer over time and B. if sent a more powerful signal could bottom the woofer out immediately. The High Frequency (HF) resonator does present some load to the woofer below the LF tuning frequency, but it is not enough to control the cone movement. DO NOT RUN your Devastator without a protective high pass filter.

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As you see in the graph above, the cone motion with the 2000 watt input on this NSW6021-6 has the driver well outside of the 21mm xmax below 20Hz. Once a Butterworth 18Hz 4th order high pass filter is actived the cone is peaking around 19mm below 20Hz(light gray line) and that is inside the NSW6021-6's rated xmax.

Slang/Terms:

HCR - High Compression Ratio. This front has a bell curve, but is not quite as peaky as a lower compression front and uses less space. Good for shallow cabinets.
TR - Tactile Response
Stepped - A front quarter wave resonator with 2 or 2+ cross sectional areas. The response is typically more flat and they gain more low end output.
BR - Bass Reflex
QW - Quarter Wave resonator. These are typically referred to as horns. On a Devastator they do the high frequency lifting.
FPR - First Port Resonance
BB - Baltic Birch plywood. (not the veneer box store stuff, call a lumberyard)
BBv1 - Big Boy Version 1
MLP - Main listening position.
REW - Room EQ Wizard.
HPF - High Pass Filter.
BW - Butterworth.
LF - Low Frequency
HF - High Frequency
HO/SHO - High Output or Stepped High Output. Usually these cabinets have 22Hz tuning.
BMD - Beast Mode Devastator. Typically they are closer to 60" height vs 48"
FV - Finalizer. This cabinet started as a 48"x25.5"x34" cabinet with lower tuning. FV can be used for the 16Hz tuned rear chamber or the form factor
Dev - Devastator. Generally cabinets that are around 48" in height.
Mini - Typically this cabinet type is around 40" in height.
Micro - Usually in the above or around 30" in height.
Nano - Usually used for 12" cabinets.
FB - Fat Boy. Typically as deep as they are wide.
BAMF - Bass Ascension Module Five. Home music or PA cabinet with higher tuning and a Stepped QW resonator.
NSW - Eminence NSW6021-6
SAN - Lavoce SAN214.50 or the SAN215.30 is another good choice, but not usually that is referring to the 214.50.
DS - That could be a B&C 21DS115 or a 18DS100-4, both are great choices.
TBW - B&C 18TBW100 is usually the reference, but the 15TBW100 is another good woofer.
SAF - Lavoce SAF184.03
WAF - Should be the Lavoce WAF154.00
D21V6 - This would be an example the Devastator 21" version 6
M18V6 - This would be an example of the Mini Devastator 21" version 6
FB21V5 or FBv5 - Fat Boy Version 5
FV1 - Finalizer Version 1

Devastator response evolution:

The Devastator has seen developments over time. The examples below are on 48" tall cabinets to show the three main fronts and how they affect the response.

The Devastator 21" Version 1 is the first Devastator designed by John. As you can see the front HF QW resonator adds SPL across the entire frequency range, peaking in the mid bass region. Light gray is ported cabinet with the same vent length, vent area and chamber volume as the D21V1.

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Next up we have the Devastator 21" Version 5 with an HCR front. The HCR front has a smaller cross section area vs the lower compression front, but still adds output across the range and takes up less space in the cabinet. Once again dark gray is the V5 and light is just a basic BR chamber with the same specs.

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Finally we have the Fat Boy Version 5 with its Stepped QW resonator that has multiple cross sectional areas. The higher tuning coupled with the design of the QW resonator makes the cabinet very flat and efficient. The higher tuning also allows the resonators to be spaced 1 octave apart in frequency without cutting our top end short, so this design can still crossover at 80Hz into a sound system.

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Other advantages to having the front QW resonator:

Cone protection from curious children, pets and sometimes friends that are tipsy. Less rear chabmer/motor noise, the panels dampen noise that would otherwise find its way through the cone and into the room. Obviously the QW resonator eats up more space vs having nothing in front of the woofer, but the QW resonator has a few things going for it.

Construction/material/tips:

The preferred building material is currently expensive. Baltic Birch plywood (not the veneer stuff at box store, call a local lumber yard) is the preferred building material. 18mm is close enough to 3/4" not to mess up the building process. MDF is heavy and makes a big dust mess and does not take screws well, tends to crack. ACX plywood is lightweight, but has voids and a tendency to warp. BB is lighter than MDF and does not make the dust mess and is less prone to warping and also voids. MDF also sucks for using Kregs.

If you have router with a flush trim bit, it is not a bad idea to add 1/8" inch on the side panels and then clean it up after assembly.

PL3X is the glue of choice due to how forgiving it is with voids and set time. When using PL, wear gloves, you do not want that stuff getting on your skin and it will mess up clothing. If you are a fluent wood worker, you do not have to say no to tight bond.

Marking panels before assembly is another pro tip. I would also suggest marking up the woofer cutout and drilling all the holes for fastening the woofer before assembly. Marking the panel alignments/positions on the side panel, front panel and baffle are all good ideas. Measure twice, cut once is another good rule to live by.

Air leaks around the access panel are usually the number one issue once the box is together. Especially if the measured response looks weak on the left corner. If you want to make sure you have a good seal, turn off the lights, put a flashlight in the rear chamber. Button the hatch up and look for light coming through the hatch seal. Weather stripping or the PE gasket tape will work.

If you have a question or are unsure of something when putting the cabinet together, feel free to post the question in the Index. This thread has large following that is happy to offer tips!

Bracing - here is a good example of a common bracing mistake. The wider dimension should be adjacent to the outside panel, like in the photo below.

Driver mounting - Chris made this write up for his technique for securing the sub to the baffle - link



Threaded Inserts (Sub woofer mounting solution)

Panel Names?


Below is a reference image
Rectangle Parallel Font Plan Diagram


Rear Chamber Resonance/dampening material

Chris when testing the JBL Quad Devastator did some measurements with different pillow configurations in the rear chamber. We also reached out to a few members for measurements they took. It would appear standing waves in the rear chamber start to encroach on the passband somewhere between 40" and 48" of rear chamber length. Boxes close to 48" on up need pillows tacked onto the side panels to alleviate near past band resonance. The goal is having a clear path from the back of the woofer to the vent inlet. Air restriction will hurt low end output. However, if there is minimal restriction in air movement, a minimal loss in low end output will take place. Here are the links to the Quad testing.

Resonance Testing Pt1
Resonance Testing Pt2

Does my UM18/IB/high Qts Sub work in a Devastator?

The short answer is no, it does not work in a Devastator. This is a UM18 in a Mini Devastator 18 Version 6.



As you can see the woofer gets a very sharp peak at the resonant point of the front horn of the cabinet. You might be thinking why not just EQ that peak? Here is the problem, the UM18 will ring when loaded in a Devastator, the cone stays in motion after a impulse. This is the UM18 vs the 18TBW100, pink is the UM18, green is the TBW. Notice how the cone on the TBW stops moving relatively quickly. Some subs are designed to work well in higher order band pass boxes, others are designed to work in lower order band pass boxes. There is a simple method for finding a good woofer using a specific metric. Efficiency Bandwidth Product (EBP), the woofers Fs value divided by its Qes value. The Devastator starts working once a value gets around 70 or so. Values closer to 100 are better, but not absolutely necessary. If you have a woofer with a value higher than 70 and are curios to see how it looks, just post a message in the thread :)



Any Devastators optimized for music?

Yes, the BAMFs are designed to handle music duty/PA use. There are currently three different versions available with different tuning depending on the needs of your system. If interested I have a smaller design meant for an 18" that will definitely make some loud noise that has not been released yet.

I bought a Crown amp that has a network card, how do I manage it???
Chris made a nice write up concerning this situation, you can find it right here. You will need the Harmon Audio Architect software installed on computer that is on the same network as the USP card.

Reference Port Plug Design - link

Performance data (HR Estimations GP1m):
The Big Boy Family 21"s
The Fat Boy Family 21"s
The Finalizer Family 21"s
The Alpha Family 21"s
The BAMF Family 18"s + 21"s
The BMD Family 21"s
The Mini Devastator Family 21"s
The Devastator Family 21"s
The Mini Devastator Family 18"s
The Devastator Family 18"s
The BMD Family 18"s
The Micro Devastator Family 18"s

Shallow + Narrow 21" + 18" Devastators

Common 21 Comparison Graphic (shoutout to Chris for his help with this)
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Common 18" Comparison Graphic
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Current (9-1-22) top picks!
Colorfulness Slope Purple Rectangle Font

Note: The Alpha III and IV have narrow clones. The FBv6 has a narrower clone and the 18BMDSV2 has a clone.

PLEASE SHARE BUILDS IN THIS THREAD!!! (including pictures)

Designs (Guide is near the bottom of this post and see build links, a lot of go information in there.)

Broken down by woofer size:

24"
21"
18"
15"
12"
Build threads/other
Guides
 

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18
#3,999 ·
I have 3 of the Minimix line mixers MX22s seen here for my 3 amps:


AVR sub trim is under 0db. Why only -3db on input gain now when you said -30db before? I will not be running the PEQ hot it stays at 0.
 
#4,000 ·
#4,007 · (Edited)
Shallow + Narrow 21" and 18" Devastators Comparison Data (Less than 24")
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Updated 2-8-22
 
#4,012 · (Edited)
Fat Boy 21" Version 6

Goals for this cabinet. Flatten the FBv5 mid band and extended the passband down slightly. 3db gain at 20Hz with a 1db loss from the mid 20s to around 40Hz vs the FBv5. I would say both goals were accomplished with only a 4" addition in height. The simulation is based on the NSW6021-6 with 1000 watts of power, a BW 17Hz 4th order high pass filter is active. Maximum SPL is 111 volts(3.24kw) and 27mm of excursion. Excursion control looks good, port velocity looks good, again the phase shift is near passband, so that could get tricky with ported subs and shorter HF Resonator Devastators come integration time.

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1000 watt simulations
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Max SPL (116v, 27mm)
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Font Material property Parallel Number Screenshot


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#4,050 ·
Looks like a FLH graph!
 
#4,019 ·
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Here is native on the DS100. The motor and suspension are a bit much for this and with HPF, you are already at xmax on 1000 watts.

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Here is the UM18, that does not look too bad on 1000 watts.

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The HST18MKIII, it has some motor, so the enclosure is big for it, but filters can pull that down.

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Next is the HT-18v3 SI, that does not look too bad from a response perspective. The are also pretty cheap.
 

Attachments

#4,023 · (Edited)
The Finalizer Version 5 is looking good and angry! The curve looks like it should handle movies very well, but really shine with EDM. BAMFv1 and v2 are right around 127db on 1000 watts through much of the response.

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21" HOs in the 46-48" height range and the BAMFv2. Did I mention EDM?

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#4,025 · (Edited)
The Mini 18"s have not gotten much love for quite a while. Seems like a good idea to use the form factor that gets build far more often than I realize. This will more than likely be the Mini Devastator 18 Stepped Version 1. The simulation is based on the 18DS100-4 cranking away with 1000 watts of power, BW 19Hz 4th order HPF active. Form factor is more conducive to WAF than some Devastators and right now $500 is not all that much for a solid sub. The response shape will be great for mixed listening, +40Hz output is very high.

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Edit: threw the M21V5 in for reference and a FMUM18

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#4,026 ·
Just a pedantic question for simplistic clarification... (I've fielded these questions myself, elsewhere, a few too many times and would appreciate a check, myself. ;) )
For just running straight (not boosting with a house curve), an Ultimax 18 in a Full Marty is meeting LFE requirements for dynamic peaks with a little headroom 2-3dB , correct? (And it can still take another 1000w of short term peak power.)

If this assessment is wrong, please help me understand what I am missing. :)
 
#4,028 ·
I wouldn't push that much power into a UM for very long. Impulse response is okay on the UM. They are best in sealed boxes. With room gain they should do well for low end headroom. An HST18 could get it done in a smaller box and take a lot more power too. Then you start eyeing the HS24 and it gets out of hand quick
 
#4,034 ·
Hey @Red Five, any chance you could post a performance comparison chart of the LFE v2 HCR, the Finalizer v1 HCR, and the BigBoy v2, along with a FM NSW? They're all posted on separate charts and I'm estimating the comparisons but its a bit tough and would be nice to see on one combined graph how the lower tuned designs stack up. Thanks!
 
#4,035 ·
I can do that when I am by my computer. Remember when you get below 67% of a subs Fs efficiency tanks fast. But low Fs subs are not that efficient.
 
#4,036 ·
I am thinking out loud here. An LLT in a Alpha or close to Alpha form factor. The HOs are full speed down to 22 or 23Hz. The LLT could be tuned around 10 or 12Hz with absolutely no care given to first port resonance, just so long as the resonance is over 40Hz. Huge vent surface area fixes compression and also gains efficiency.
 
#4,037 · (Edited)
This is what I am looking at for the LLT Companion sub. If HO extension does not scratch the itch, add these babies and crossover from the HO around 23 to 25Hz Just keep adding these until something breaks or desired output level is reached, whatever comes first! The simulation is 1000 watts with the HS24, vent velocity is 14.6m/s. Net volume is 19.41 cubic feet or 550 liters. Tune comes in at 12Hz. A BW 11Hz 4th order HPF is active. Excursion is around 19mm, so 50% of rated xmax. I might make some tweaks to it yet, but this should be pretty close. I could probably make the vent smaller, but I really hate vent velocity since compression comes in fast.

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Edit: The extension on the LLT is substantial. You can see physics at work here, quite the SPL hit, but these low frequencies have big energy requirements.
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#4,039 ·
If space is a concern, which I doubt if you are looking at the LLT the Mini 18 Stepped V1 could be a good match.

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#4,040 ·
Now if I could just get some HS24s so I can join the club. :)
 
#4,043 ·
Now if I could just get some HS24s so I can join the club. :)
Such a pipe dream, for me, in some ways. It would be easier if I had more juice available that I could run to my rig. I would love to have that and a mid-bass oriented Dev added to my 3 dual SQL-15s I'm tryin to build. ;)
It's a shame that for the price, it's still easier to run 6 SQL-15s than a single HS-24. Unless I'm doing the math wrong. But at that point, it's also the same for pushing an NSW to it's limits.

Fcuk it. I need a bigger room, my own audiophile grade power plant, and one helluva bigger paycheck. :p
 
#4,044 ·
One last sanity check. HS-24 Companion LLT vs 11 cubic foot sealed.

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#4,051 ·
Where's the 24" Devastator...with and without front fold???
 
#4,048 ·
^
Has anybody ever seen any good 3rd party measurements of PSA's Subs? I've been curious to know their efficacy. And highly skeptical. Last time I was on his site, he was still saying that measurements were coming soon... and that was something like over a year ago when I first saw that, and still there a few months ago. *shrugs
 
#4,066 ·
I know things are making a fast turn to extension once again. I am posting this video as a reminder as to why HOs exist, slam the chest in factor.

That JW1 gunshot will be an example in there.
 
#4,067 ·
I know things are making a fast turn to extension once again. I am posting this video as a reminder as to why HOs exist, slam the chest in factor.

That JW1 gunshot will be an example in there.
So he is considering mid bass 20 to 50 Hz. Guess I had a different frequency range in mind for mid bass.
When I got my system sorted-out it was night and day different, but my issue was at 85Hz.
Once I fixed that issue I went from liking my system to loving it.
So if 85Hz is not mid bass then I don't know what it is.
I don't care about sub 20Hz. One of my enclosures is tuned for 19Hz, but I have not spent any time to see what it actually does around that frequency and to improve it.
It is very strong to 30Hz though with my house curve. Pretty flat to 25Hz without the house curve.
 
#4,068 ·
yes i finally got a umik and rew over the last 2 weeks, have spent the last year eqing by ear, with an iphone spl app, and radio shack digital reader and youtube sine waves.

umik and rew were a GAME CHANGER. Ive been aware that anything boosted above 50hz over 10db above speaker levels just gets muddy and messy, but being able to create an accurate house curve has really allowed the subs to integrate with my speakers on a new level.

now the only remaining issues are from the room, not my eq.
 
#4,076 ·
Just putting the low tune marty out there,

After building the boss, my opinion has changed with trying to get low with large subwoofers,
The boss with BEQ provides all the shaking I need and my house or wife won't get angry ,
The chopper scene in lone survivor is 6hz and is just silky to feel

2nd
Cost , the boss is super budget compared to low tuned sub, also room plays a major role in spl/hz
 
#4,077 ·
Just putting the low tune marty out there,

After building the boss, my opinion has changed with trying to get low with large subwoofers,
The boss with BEQ provides all the shaking I need and my house or wife won't get angry ,
The chopper scene in lone survivor is 6hz and is just silky to feel

2nd
Cost , the boss is super budget compared to low tuned sub, also room plays a major role in spl/hz
Can you provide some info on your BOSS setup?
I plan on making one with the famous 12" JBL's. I picked-up 16 this year.
I have no one to worry about with SPL, the room is about 75ft, actually 100 feet from the closest point of my house.
I was going to put 2 per cushion (3 cushion couch). Remove the legs and make a plywood platform for the speakers and figure it would be close to the same seated height as it is now.
Doesn't really matter, 99% of the time I am the only one listening to it, besides my spider and stinkbug friends...... ;)
I only listen to music but I am interested in seeing how some of the movies I have will sound and feel in there.
 
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