"Design Phase - 2 Monster Front Loaded BR Subs"
I would like some input, lots of it in fact, to help me design a pair of monster front loaded bass reflex subs for filthy techno rumbles.
The only criteria so far is the drivers be 18inch, 4 ohm nominal impedence and somewhere in or around the region of 1600w RMS/AES each.
I have some ideas but ultimately, they will bee housed in 2 front loaded 25mm MDF cabinets with two huge huffing round ports "down below and out front".... as they say.
Well, that's about it really.... Everything else is open to discussion
So, we might as well go straight off the bat, this particular driver is wetting my whistle and most likely the model I would have chosen....
https://www.eighteensound.it/en/products/lf-driver/archive/18lw2500
https://loudspeakerdatabase.com/18Sound/18LW2500
This beast was also a contender but after much searching and reading it turned out to be out of stock everywhere.
https://leanaudio.co.uk/product/celestion-cf18vjd-4-ohm-18-1600w-loudspeaker/
https://loudspeakerdatabase.com/Celestion/CF18VJD
You know what's funny.....? There are no listing for the 4 ohm version on Celestion's website, nor the loudspeaker database.
And then I read in a thread on another forum somebody stated that there is no 4 ohm model of this driver.
But then I came across this ----->
https://www.gear4music.ie/PA-DJ-and...D-18-Low-Frequecy-Subwoofer-Driver-4-Ohm/2O08
https://www.gear4music.ie/PA-DJ-and...D-18-Low-Frequecy-Subwoofer-Driver-8-Ohm/2O0D
Has the 4 ohm driver been discontinued or did it ever exist at all.... Are the 4 ohm models just plain misquoted or misprinted....?
Can anybody confirm this for me....?
And then I found these ----->
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=201070141
https://loudspeakerdatabase.com/Faital/18XL1600_4Ω/Faital_18XL1600_4Ω.pdf
Very impressive.... But also very expensive !!!
It looks like my choice of drivers will more than likely be either number 1 or number 3
Has anyone got any experience or opinions to add, I sure would love to hear them if you have.
Next up, enclosure design and build.
Cabinets will be built with the intention to last 100 years in keeping with the "speaker from scratch" thread
https://www.diyaudio.com/community/...-design-your-own-speaker-from-scratch.332688/
I will be following this thread carefully and intend to remain true to it's principles to the best of my ability.
I found 2 sets of enclosure plans, one for the 18Sound 18LW2500 and one for the Celestion CF18VJD.
I will attach the pdfs to this post.
The 18Sound design has an effective volume of 177 litres yet I read somewhere in their literature that the recommended
enclosure size is just shy of 200 litres.
The plans from Celestion quote an effective volume of 167 litres so these two drivers of similar spec would appear to need
an almost identical sized enclosure.
This is where my questions begin.... Will it hurt if I go bigger....?
Size is not a problem here, volume and sound quality are far more important to me.
I am just about to model these drivers and a few different boxes in WinISD but I would really love to hear what some of you guys have to say.
Oh yeah, and one more question for now please.
What is the best crossover point for bass heavy, earth shaking techno....?
Once the build is complete I will begin my testing at the standard 80Hz
That will do for now, I will be back here regularly to check in, post my progress and share my journey with interested members.
/DATABASS
I would like some input, lots of it in fact, to help me design a pair of monster front loaded bass reflex subs for filthy techno rumbles.
The only criteria so far is the drivers be 18inch, 4 ohm nominal impedence and somewhere in or around the region of 1600w RMS/AES each.
I have some ideas but ultimately, they will bee housed in 2 front loaded 25mm MDF cabinets with two huge huffing round ports "down below and out front".... as they say.
Well, that's about it really.... Everything else is open to discussion
So, we might as well go straight off the bat, this particular driver is wetting my whistle and most likely the model I would have chosen....
https://www.eighteensound.it/en/products/lf-driver/archive/18lw2500
https://loudspeakerdatabase.com/18Sound/18LW2500
This beast was also a contender but after much searching and reading it turned out to be out of stock everywhere.
https://leanaudio.co.uk/product/celestion-cf18vjd-4-ohm-18-1600w-loudspeaker/
https://loudspeakerdatabase.com/Celestion/CF18VJD
You know what's funny.....? There are no listing for the 4 ohm version on Celestion's website, nor the loudspeaker database.
And then I read in a thread on another forum somebody stated that there is no 4 ohm model of this driver.
But then I came across this ----->
https://www.gear4music.ie/PA-DJ-and...D-18-Low-Frequecy-Subwoofer-Driver-4-Ohm/2O08
https://www.gear4music.ie/PA-DJ-and...D-18-Low-Frequecy-Subwoofer-Driver-8-Ohm/2O0D
Has the 4 ohm driver been discontinued or did it ever exist at all.... Are the 4 ohm models just plain misquoted or misprinted....?
Can anybody confirm this for me....?
And then I found these ----->
https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=201070141
https://loudspeakerdatabase.com/Faital/18XL1600_4Ω/Faital_18XL1600_4Ω.pdf
Very impressive.... But also very expensive !!!
It looks like my choice of drivers will more than likely be either number 1 or number 3
Has anyone got any experience or opinions to add, I sure would love to hear them if you have.
Next up, enclosure design and build.
Cabinets will be built with the intention to last 100 years in keeping with the "speaker from scratch" thread
https://www.diyaudio.com/community/...-design-your-own-speaker-from-scratch.332688/
I will be following this thread carefully and intend to remain true to it's principles to the best of my ability.
I found 2 sets of enclosure plans, one for the 18Sound 18LW2500 and one for the Celestion CF18VJD.
I will attach the pdfs to this post.
The 18Sound design has an effective volume of 177 litres yet I read somewhere in their literature that the recommended
enclosure size is just shy of 200 litres.
The plans from Celestion quote an effective volume of 167 litres so these two drivers of similar spec would appear to need
an almost identical sized enclosure.
This is where my questions begin.... Will it hurt if I go bigger....?
Size is not a problem here, volume and sound quality are far more important to me.
I am just about to model these drivers and a few different boxes in WinISD but I would really love to hear what some of you guys have to say.
Oh yeah, and one more question for now please.
What is the best crossover point for bass heavy, earth shaking techno....?
Once the build is complete I will begin my testing at the standard 80Hz
That will do for now, I will be back here regularly to check in, post my progress and share my journey with interested members.
/DATABASS
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Depending how low and loud you want the filthy rumble level, a pair of front loaded 18" may just be starting to get the party started.
You can achieve about 6dB more "rumble" with the same drivers and power using tapped horns in slightly larger enclosures, but you already made your choice, so no need to discuss that further 😉
Your idea of using MDF for the cabinets is at odds with wanting them to last 100 years, high grade plywood like Baltic Birch would be a far better choice for both longevity and stiffness to weight ratio. Well braced 19mm (3/4") plywood is thick enough for high powered single or dual 18" front loaded designs.
"Huffing round ports" waste power and "blow". Large laminar vents avoid port compression, chuffing and huffing.
L'Acoustics subwoofers are a good example of this style of porting, which lends itself to DIY easier than round laminar vents, and also provides cabinet bracing absent in a round port.
Bigger is better for efficiency, and the lower the Fb (box tuning) the more box volume needed to avoid a steep drop off in the bottom end. There is a huge size increase for each 1/3 octave lower you go- 40, 30, 25, 20Hz.
The lower the Fb, the longer the port required, occupying a good percent of the cabinet volume.
The best upper crossover point for bass heavy, earth shaking techno, or any other genre depends on the top cabinets used, the bass "haystack" desired, and level. A front loaded sub using decent drivers can cover
The Fb is the most important consideration, as the bottom can't be pushed more than a few Hz below a low Fb.
The Celestion plan you attached has an Fb above 40Hz, some techno has another octave of bass below that.
Once you decide "how low" and "how loud", "how big" will be next.
Art
You can achieve about 6dB more "rumble" with the same drivers and power using tapped horns in slightly larger enclosures, but you already made your choice, so no need to discuss that further 😉
Your idea of using MDF for the cabinets is at odds with wanting them to last 100 years, high grade plywood like Baltic Birch would be a far better choice for both longevity and stiffness to weight ratio. Well braced 19mm (3/4") plywood is thick enough for high powered single or dual 18" front loaded designs.
"Huffing round ports" waste power and "blow". Large laminar vents avoid port compression, chuffing and huffing.
L'Acoustics subwoofers are a good example of this style of porting, which lends itself to DIY easier than round laminar vents, and also provides cabinet bracing absent in a round port.
Bigger is better for efficiency, and the lower the Fb (box tuning) the more box volume needed to avoid a steep drop off in the bottom end. There is a huge size increase for each 1/3 octave lower you go- 40, 30, 25, 20Hz.
The lower the Fb, the longer the port required, occupying a good percent of the cabinet volume.
The best upper crossover point for bass heavy, earth shaking techno, or any other genre depends on the top cabinets used, the bass "haystack" desired, and level. A front loaded sub using decent drivers can cover
The Fb is the most important consideration, as the bottom can't be pushed more than a few Hz below a low Fb.
The Celestion plan you attached has an Fb above 40Hz, some techno has another octave of bass below that.
Once you decide "how low" and "how loud", "how big" will be next.
Art
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I suppose the honest answer to that is "as low and as loud as possible and as big as I can tolerate"
Thank you for your reply... It really got me thinking (thumbs up !!)
After much reading and a few WinISD binges I was slowly getting to grips with the calculator.
I loosely modelled many drivers of similar specs against a "guesstimate" box volume of 200 litres and it became quickly apparent that the
Eighteensound 18LW2500 in 4 ohm flavour was the clear winner.
But unfortunately, these rare beasts were out of stock every where and pretty much unobtainable.
So, in the end, I settled for the next best thing, and ordered a pair of Faital Pro 18XL1600 C, again in 4 ohm specification.
(Datasheet attached).
Having heard of this now famous "Hofmann's Iron Law", I was already resigned to the fact that I was going to give up size for low bass notes
and sensitivity.
That one's is just a no-brainer !!
The horse race between Low Bass Notes and Maximum SPL was neck a neck but in the end Max won, and I sold my soul to the devil down the
crossroads at midnight.... Yes people, I traded a couple of hertz for a few decibles.... Using the length of the port and it's tuning.
Final results -
128dB @ 37Hz (frequency range)
Freq. Range - 30-1500
Speaker Fs - 32Hz
292 litre Box tuned to 34Hz Resonance Frequency with 2 6" inch round ports running on the raggy edge of "chuff". 34 m/s
(This can bee slowed down to 18 with a pair of flares if I have to)
Everything else checks out, cone excursion was good, etc., etc.
Well, except Group Delay, but I will revisit that later.
F3 is now almost 32Hz
Transfer Magnitude and Maximum SPL graphs attached below.
I think I have pulled the best tune for what I want out of the software.
Which led me to think what exactly were the parameters I was shooting for, I didn't really knpw what I was doing.
And another thing.... How the hell does somebody model one of those L'Acoustics ports like you posted above....?
Thank you for your reply... It really got me thinking (thumbs up !!)
After much reading and a few WinISD binges I was slowly getting to grips with the calculator.
I loosely modelled many drivers of similar specs against a "guesstimate" box volume of 200 litres and it became quickly apparent that the
Eighteensound 18LW2500 in 4 ohm flavour was the clear winner.
But unfortunately, these rare beasts were out of stock every where and pretty much unobtainable.
So, in the end, I settled for the next best thing, and ordered a pair of Faital Pro 18XL1600 C, again in 4 ohm specification.
(Datasheet attached).
Having heard of this now famous "Hofmann's Iron Law", I was already resigned to the fact that I was going to give up size for low bass notes
and sensitivity.
That one's is just a no-brainer !!
The horse race between Low Bass Notes and Maximum SPL was neck a neck but in the end Max won, and I sold my soul to the devil down the
crossroads at midnight.... Yes people, I traded a couple of hertz for a few decibles.... Using the length of the port and it's tuning.
Final results -
128dB @ 37Hz (frequency range)
Freq. Range - 30-1500
Speaker Fs - 32Hz
292 litre Box tuned to 34Hz Resonance Frequency with 2 6" inch round ports running on the raggy edge of "chuff". 34 m/s
(This can bee slowed down to 18 with a pair of flares if I have to)
Everything else checks out, cone excursion was good, etc., etc.
Well, except Group Delay, but I will revisit that later.
F3 is now almost 32Hz
Transfer Magnitude and Maximum SPL graphs attached below.
I think I have pulled the best tune for what I want out of the software.
Which led me to think what exactly were the parameters I was shooting for, I didn't really knpw what I was doing.
And another thing.... How the hell does somebody model one of those L'Acoustics ports like you posted above....?
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FWIW, reference vented box design math, which of course you can rearrange for different 'target' specs:
T/S max flat alignment:
Vented net volume (Vb) (L) = 20*Vas*Qts'^3.3
(Ft^3 = (Vb)/~28.31685)
Vented box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96
F3 (Hz) = Fs*0.28*Qts'^-1.4
T/S max flat alignment:
Vented net volume (Vb) (L) = 20*Vas*Qts'^3.3
(Ft^3 = (Vb)/~28.31685)
Vented box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96
F3 (Hz) = Fs*0.28*Qts'^-1.4
Oh boy, am I glad to see you !!
Funny you should mention these, because they have been haunting me all day, repeatedly popping up in searches.... In your posts ironically enough.
Can I just clarify
The silly little * icon is multipy X......? Up top arrow ^ is "to the power of" and sqiggly line ~ is divided by,..... maaybee.....?
Funny you should mention these, because they have been haunting me all day, repeatedly popping up in searches.... In your posts ironically enough.
Can I just clarify
The silly little * icon is multipy X......? Up top arrow ^ is "to the power of" and sqiggly line ~ is divided by,..... maaybee.....?
It could be modeled in Akabak, and probably in Hornresp.
This model is lacking the proper parabolic/elliptic curve of the port, but gives hope that it could be done, though somebody familiar with the program could probably figure out how to do it.
This sim has Fb about 31.4 Hz, excursion about 12.5mm.
The 133dB peak would be less than the sim predicts, there is a "QL=7" setting that should be applied, but I missed where..
The Hornresp thread would be the place to get a better model suggestion.
Art
Argh !!!
You also quote another formula in another thread I have been reading, this one ----->
"With specs like this [and up to a ~0.403 Qts'], the pioneers determined that the optimal box/driver compliance with best transient response [least 'hangover./'boom'], max gain BW is [measured] Vas/1.44 tuned to Fs.
Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design
[Rs] = 0.5 ohm minimum for wiring, so may be higher if a super small gauge is used as a series resistor"
I plugged it in and it just didn't add up..... What gives.....?
Dammit..... He's gone !!!
(facepalm)
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I was reading something earlier and one member mentioned modelling it as a rear horn, I thought that sounded promising..
My WinISD thinks I'm in a rear chamber and I have to check the rear port velocity for my vent airspeed.
Actually, while we are on the subject, I found this design as a starting point to the KS28 single 18" "mini-scoop" or whatever it should bee called.
PLAN KS28 SINGLE 18" SUB
And comes with a claimed 137.5 dB...... Wow !!!
Yeah, really need the whole 'story', plus need to keep in mind that the pioneers ~sacrificed everything for max acoustic efficiency because they had so little electrical power to work with; oh! and BTW some dude named Les Paul liked how this tuning made his new invention sound so much that last I checked they were still being tuned this way, though admittedly it's been decades now, so YMMV, etc..
Pg. 76: https://archive.org/details/HowToBuildSpeakerEnclosuresByAlexixBadmaieffDonDavis/page/n75/mode/2up
“A nagging question in the design stage of any enclosure of this type is "How large shall it be?” It was pointed out earlier that the enclosure can be too large or too small for proper bass-reflex action. This implies that an optimum volume exists and indeed it does. This optimum volume does not depend upon the size of the speaker nor its resonant frequency per se but rather on the ratio of enclosure air stiffness to the speaker cone suspension stiffness. This optimum ratio is 1.44 or, looking at it another way, the speaker resonant frequency in the enclosure before porting should be 1.56 times the free-air resonance of the speaker. This size enclosure, when properly tuned, yields at the same time the most extended low-frequency response and a transient response with subjectively unnoticeable hangover, assuming sufficient damping exists. Compared to the entirely closed cabinet, the half-power point (3 db down) occurs at 0.7 times the closed cabinet speaker resonance for an extension of one-half octave."
Note too that Vb = Vas/1.44, Fb = 1.56x Fs was the default prosound alignment for ages and last I checked still in occasional use by 'those in the know', including at least one major manufacturer up to a few years ago, so might want to experiment beyond sims where ~continuous high power is the norm. Heck, might even come to realize it's a form of compression driver design. 😈
The KS28 bass reflex design (based on a Helmholtz resonator) is similar to L'Acoustics (and other's) use of laminar vents.
Laminar vents are not really horns, though can be modeled as such. A "scoop" design uses a small volume rear (band pass) chamber and a relatively large scoop shaped horn.
The video sim with 137.5dB SPL has no reference to Fb, driver, power, excursion or loading (1/2 space, 1/4 space, etc.) so is not very useful, other than showing a recent example of laminar venting.
BIC introduced their “Venturi Port” in 1973, various forms of low-turbulence port shapes to reduce noise and air velocity are nothing new, but the increasing displacement of drivers since then has required far larger port volume to be linear at high drive levels.
Rounded vent can be simulated using dual exponential horns profile, the results will be very close from real use case purpose.
https://freeloudspeakerplan.rf.gd/pages/moderndualvb2.htm
https://freeloudspeakerplan.rf.gd/pages/moderndualvb2.htm
I made a ported [ or maybe it went MLTL] with an 18 and even with only 30 or 40 watts it's unbearably loud. Also quite gut rumbling deep
Driver rated 120 W I ask why you need so much power handling ?
Isn't it only another 6dB?
Driver rated 120 W I ask why you need so much power handling ?
Isn't it only another 6dB?
The OP wants "earth shaking" levels, which are probably louder than what you consider "unbearably loud" 😉
160 watts is +6 dB over 40 watts.
1920 watts is +12 dB over 120 watts.
The drivers considered in this thread are rated for more peak power than that.
With compressed bass lines, voice coils heat up, impedance rises, easy to loose -3dB to thermal compression, 2000 "watts" (126.5 volts into 8 ohms) equivalent to 1000 when cool.
Maybe cheaper and safer to stand behind a 747 on take-off. Then a pair of tapped horns tuned to 16Hz seem to be what the OP would need perhaps
It would be about -6dB cheaper for "Databass" to use tapped horns, but he already stated his preference for "Front Loaded BR Subs" in the OP.
As far as jet engine noise, it rolls off in the bottom considerably, about -30 dB at 40Hz compared to 3kHz.
Jet noise at close range will tear your hearing up in a hurry- low bass takes much longer.
As far as jet engine noise, it rolls off in the bottom considerably, about -30 dB at 40Hz compared to 3kHz.
Jet noise at close range will tear your hearing up in a hurry- low bass takes much longer.