12v bicycle trailer sound system details

yeah... the amp got warm even playing at a VERY low level. the speakers just can't dig down much below their 70Hz rating, BUT they can sound reasonably full range with a boost.

i just don't have the money for the sub at the moment. i'm still trying to figure out why i'm about $200 short of where i should be. bills have to come first.

the weather's really turning cold here too. it's looking like i got it together too late, but i'll have all winter to finish everything. right now, i'm trying to figure out how to lay everything out. this trailer frame is really proving to be a pain with both it's thicker in the middle than the corners wheel mounts, the frame droop in both the front and back, the REALLY annoying rollbar mounts inside the frame that make dropping a flatbed inside the frame impossible unless i narrow it too much to even fit my mains, the lack of any convenient way to solidly mount a flatbed, and the less than 1/8" per side play i have to drop side rails inside the wheels which just might be too close tolerance to buy pre-cut wood a pain. it's like the frame was DESIGNED to keep anyone from converting it on purpose. it was so easy to get a few pieces of wood cut and bolt them to my former instep trailer. aside from bus travel to acquire the wood & screws, it only took a couple hours to build on top of a pair of "2x2"s bolted to the frame.

it's too late now. i'm not just past warranty, but i've had to void it to get that freakin' shell off. i originally planned on dropping the sub below the frame, but the wonky way i'd have to section, level and crossbraces to make it all work. oh well. i've got to go. i'm falling asleep here.

If you want decent sounding bass more that 3 feet away outdoors you're going ot have to step up to killowatts from watts for your low end power.

whatever bass i get will be more than enough. "loud bike" gets by on 2 x 92dB 12s at 100w each (i STILL say the opposing ports cause bass cancellations) and is more than enough for a street party. i'm not trying to hit 150dB here, just get some real bass out of my trailer. WAY BACK in the 80s, before megawatt amps, someone brought a single woofer 12v hand truck system to the ticket line for a pink floyd concert, and that thing did an amazing job of filling the 50 foot plus alley between buildings at a distance of 100 feet. i don't even think he was using a 15" sub and doubt he had much over 200 watts.

either way, it doesn't matter. the system will make ME happy and that's the only person i really have to impress. if i can get a sunbather dancing nearly 100 feet away with a pair of 5 1/2" 65Hz-20kHz, ±3dB. Sensitivity: 88dB/W/m mission M71s, with their ports plugged, driven by 10wpc, if that, from an original sonic impact amp,

i think i'll be OK with this +20dB system where sounding GOOD is more important than how loud or deep it goes, and that JBL should be anything BUT shabby and i already know my proel mains will be up to the task of playing loud without distorting. i'll be OK.

if someone else wants to build a bigger, louder system, let 'em. i'll still have a crowd pulling lightshow with mine with mains that can be pulled and separated for stereo imaging. THAT, and freedom from sloppy distorted boom will be my system's signatures. light weight? ehhhhh not so much. more battery, amp & magnet? no thanks.

BTW... the sealed .7Q for the JBL in a nearly 4x4 box is SICK...
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if the sub can make most of the people who've bought one happy for their car system, it'll make me even happier with a bike system that doesn't boom, but that thumps like no boombox possibly could. we used to dance to those back in the day, and no-one complained.

it's not just the power of your system, it's the beats you play too...


"Superman had come to town to see who he could rock
He blew away every crew he faced until he reached our block
His speakers were three stories high with woofers made of steel
And when we brought our set outside, he said "Ha! You for real?"
He said, I'm faster than a speedin' bullet when I'm on the set
I don't need no flash to cool my ash, I just use my super breath
I can fly three times around the world without missin' a beat
I socialize with X-ray eyes, and ladies think it's sweet
And then he turned his power on and the ground began to move
And all the buildings for miles around were swayin' to the groove
And just when he had pulled the crowd and swore he won the fight
We rocked his butt with a 12 inch cut called Disco Kryptonite"

one of the FEW raps i actually like

PROBABLY a reference to cool herc's infamous herculords speakers...


hmmm... disco kryptonite... that's a potential system name too and i also considered beatmobile, but comics have never really been my thing. atomic boom's a name for a ported system.

i WANT to get my system SMD measured for 1% distortion which i shouldn't hit because i don't listen to 100% volume tracks as most are reduced to 50% volume so as not to overpower vinyl tracks or pre-loudness wars ones like blondie's the tide is high. if i hit 1% distortion, it'll only be a few peaks and nothing continuous.

The cabin of a car focusses the bass towards you up front so the bass is much stronger than speakers that are outdoors that radiate the bass all around.
The website of https://www.subwoofer-builder.com/vents.htm shows that a ported enclosure produces more bass than a sealed enclosure (when its enclosure is larger) and also lists the small delay that a ported enclosure has.

yes... i've been very aware of the efficiency benefit of ported speakers since the mid 80s when i learned why i preferred small sealed minis to ported towers and the pros and cons of each alignment. the bottom line is i DESPISE the distorted "marshmallow bass" sound of ports and will never go that route, unless there's foam plugs included. (some day, i'd like a pair of KEF LS50s... ports plugged)

i swear people don't listen to me. YES, i AM trying to get the loudest system REASONABLY possible, but NEVER at the expense of distorted bass. i hate it! i hate it! i hate it! i hate it! i hate boom and will only accept THUMP. i've already compromised transient response by going with a 15" sub. that's as compromised as i'm willing to get. BEFORE i started this system, i actually wanted to build a 4 x 8" sealed trailer for maximum thump. i have no use for sloppy distorted bass no matter how loud it gets. if everyone ELSE wants that, that's their biz, but not in my system EVER.

whatever bass i get, IF i can even finish the system as planned as JBL just discontinued the GT5-15 and sonicelectronix is already out. i might have to end up using a single 12 before this is over, but even then, whatever bass i can get out of it in a sealed box will be adequate. that's the point of my system... sounding DIFFERENT than boomers whose systems won't be able to thump this as tightly as i can...


i just guess that i'm extra sensitive to bass slop. i just can't stand when kick drums get bloated. heck, if i could afford it, i'd build a system out of a pair of maggies, which roll the bass off even more, but OMG! the bass they DO put out is lightning fast with zero overhang or box resonance. THAT's my idea of bass. ported subs? over my cold dead body! i've plugged the ports on any bass reflex speakers i've owned, even if the otherwise AWESOME sounding energy RC10s i owned that had terrible box resonances when the ports were plugged because of their flimsy 5/8" cabinets. at least the bass was tight and uncolored even if they sounded boxy compared to my superzeros with their inferior drivers, but superior cabinets.

i SWEAR there's a conspiracy against making sealed minis with both quality drivers and 3/4" MDF at reasonable prices because they would destroy the overpriced towers market. it's very possible to build $500 minis that walk all over much more expensive speakers, especially when they're paired with a sub.

i'll never forgive boston & infinity for selling out. they USED TO make the best sounding entry level speakers. it was little infinity bookshelf speakers that were the FIRST to blow me away despite having visited 4 different stereo shops half a dozen times each before listening to a friend's 4 1/2" x 3/4" styrofoam tweetered infinity reference minis, very similar to these, but with only the tweeter dome & not surround showing, the tweeter at least was flush mounted and the woofer baskets were "semi-square" & very cheap looking. but the sound blew me away

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after reading up on phase & timing errors, resonance, air springs, diffraction, and driver mass... i decided acoustic sub/sat was the best way to go for transient speed, freedom from distortion and superior imaging (lower diffraction small cabinets, preferably with radiused edges) though i really did like boston's 8 inch mini towers with 3 inch cone mids and 3/4" soft domes playing planet drum. they had the bass balls the infinitys didn't, but imaged and handled percussion just as well.

a few years later, THESE were the speakers i lusted after



even if they had "big dumb 5 1/4" woofers" and $1000 was out of my price range. they solved just about every possible distortion issue for cone woofered speakers including time alignment, and i kind of thought they looked sexy too. that super fast EMIT tweeter with it's tiny (not radiused though) baffle screamed "imaging monsters" (except for maybe diffraction off the woofer's top and so far in front of the tweeter) that don't soften cowbells like silk domes do. i dreamed of mating them to an 8 inch sub.

back to the JBL, i ran the numbers on dayton woofers, and it destroyed both the reference HF & HOs in output as well as matching the ultimax curve within 1 or 2dB without factoring its higher efficiency, though i imagine the daytons would beat it in SQ. i gained more respect for it when it showed it can go toe to toe with woofers twice its price, at least as far as output is concerned.

i THINK that dubstep bass might be another place where sealed subs can shine over ported by not blurring the sterile sounding digital "buzz" into something warmer and fuzzier and with less texture.

A properly designed ported speaker has very low distortion and a flat frequency response to prevent a sloppy boomy sound. A boom box with a cheap high-Q woofer is not properly designed and produces one note bass (its resonance).
The second speaker I ever made still works 53 years later. It uses a 5" woofer and 1" dome tweeter in a sealed enclosure and it is flat down to about 80Hz but 40Hz can easily be heard. My first speaker was a disaster with a 12" cheap woofer and a horn tweeter . A guitar and a vocal sounded like a trumpet.

i just don't like ported speakers. period. they create MULTIPLE forms of distortion that can only be minimized but never eliminated, and the very RESONANT bass boost they give IS a form of distortion adding harmonics that don't exist in a recording, and i don't like that.

i've been thinking about the bass gain comment regarding cars too. i DESPISE that sound. it's marshmallow bass at its worst and it gives me a headache.

whatever bass i can squeeze out of my system, which still has bass boost as well as EQ most likely down the road to give the system a little more bottom, but i'm more concerned about how free from distortion it is.

i REALLY wish someone who has the gear would post both waterfall and distortion plots for the same woofer in both sealed and vented boxes for even MORE evidence of why i refuse to EVER go bass reflex because i get so sick and tired of arguing the point. i like the tight and undistorted sound of sealed woofers and have no problem trading extension for it, and probably prefer a little rolloff anyways so my head doesn't 30 hurts. (pun intended)

the ONLY form of "distortion" from acoustic suspension is reduced output in the lowest octaves. that's 1000 times better than ACTUAL distortions, and i don't see why nearly EVERYONE accepts bass reflex distortions, even, idiotically claiming they don't even exist sometimes eg. "ported boxes actually have MORE control over the cone".

the bottom line is ported woofers muddy the bass and it's NOT open to debate. it's a well established scientific FACT even if i don't have the waterfall plots i know would prove the point visually.
- time delay
- overhang
- transient blurring (or as i like to call it... marshmallow bass)
- port chuffing
- loss of pitch definition... one note bass at the extreme
- phase distortion
- lack of woofer control, especially below resonance
- resonant distortion (the 30Hz, or WHATEVER [resonant] tuning frequency of ANY bass reflex speaker = ARTIFICIALLY ADDED harmonics that don't belong there, i'll NEVER get how anyone can think that's "a good thing", ever)

NONE of these forms of distortion are acceptable. again, the idea behind hifi is SUPPOSED to be reducing distortion, just like sealed speakers do. SLIGHT kudos to raidho $peaker$ who've FINALLY learned the err of their ways and FINALLY offer foam plugs to tame their flagship models NOTORIOUS overly boomy bass that shouldn't be an issue with $200,000+ speakers.

I like the audio website of Rod Elliot in his business called Elliot Sound Products but the site is gone. He replied on diyaudio.com forum that he closed it because he was angry with his web host provider but his new site does not work.
He is an audio expert and would probably agree with other experts that an old ported enclosure was simply a guess full of errors but a modern computer-aided design works fine.

Years ago I bought a pair of Radio Shack speakers on sale that had a 6.5" woofer with a big magnet and a real rubber surround in a sealed enclosure. The cone tweeter was garbage which I replaced with a dome tweeter and a new passive crossover network. My mods worked well but the speakers had limited bass. I ported the enclosures and got one full octave more bass and they sound great.

My main speakers were Acoustic Research AR-4x with 8" woofers in sealed enclosures. After many years the flexy wires on one woofer broke, probably because a sealed enclosure causes the woofer to flex the most at resonance. If the enclosure was ported then the speaker would still be alive because the flex at resonance of a woofer in a ported enclosure is minimal (the port does the work).

yes... a properly designed ported speaker with a properly matched woofer will sound better than a random combo, but even the BEST OF THE BEST bass reflex system is BASED of distortion. that's what resonance is... hello! it's like when you blow on the lip of a bottle. you excite the air volume's RESONANT FREQUENCY and DISTORT the sound of your breath. ported speakers do THE EXACT SAME THING.

they resonate
resonance = distortion

i tell you, port lovers take it really personal that the FACT is they like distortion, but no amount of denial will ever change the well established science. (that many knee jerk port trolls CHOSE to remain ignorant of much like religious zealots... when the facts contradict the belief... just ignore them, is their problem)

i knew what i prefer BEFORE learning WHY, but now i know the science too, and agree with it.

or, as i ALWAYS am fond of saying...

If it's ported, it's distorted.

my ears INSTANTLY knew this fact the first time i heard snappy RESONANCE FREE bass that brought me one step closer to live sound.

"ahh... so THAT'S what a kick drum & bass guitar REALLY sound like! ohhhhhhhh! THAT's why most speakers are so "meh"... they deliberately ruin the sound. ohhhhhh! amazing! this little 4 1/2" woofer sounds BETTER than big sloppy 12" ones. huh. why is that?"

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to this very day, THESE are STILL the best (least distorted) speakers i've ever owned

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i've owned JBLs, missions, celestions, 12" refits with titanium tweeters, and even energys that had MUCH better drivers especially the faster aluminum tweeter, but like all the others, distorted the sound with EITHER port or box resonances. superzeros REALLY could use quality woofers and better tweeters, but their cabinets are brick solid and they image like crazy. it's just that like my bass drums have to THUMP, my cowbells gotta click, and soft dome inability to do that always drove me crazy.

actually, the 12" boxes i re-loaded with new drivers doesn't have box resonances, the titanium tweeter is beautifully balanced between aluminum spit and soft dome softness, but the woofer overwhelms the tweeter's 93dB efficiency making the system midrange forward, especially at low volumes and, again, at low volumes, there's an odd "zipper" distortion from the woofer i can only guess is related to either the accordion surrounds or voice coils making the woofer move in barely detectable stuttering stair steps. it's at a much lower level than the other speakers' box & port resonances, and disappears at volume making it the second best speaker i've ever owned. a port lover would rate it first for both being full range and the ability to really crank up and sound effortless.

if only the drivers were mounted in a REAL cabinet, energy RC10s would be the best speakers i've ever owned by a mile, but the choice between either port OR box resonance is unacceptable. BOTH forms of resonant distortion SUCK!

Guess what? All speakers and all enclosures have resonances. If the Qt of the speaker is too high then at resonance it will ring like a bell and smear low frequencies. If the Qt is too high then the speaker will also have a level peak at resonance.
A properly designed ported enclosure sounds fine with higher sensitivity and extewnded low frequencies than a sealed enclosure.

yes, drivers have self resonance, and high Qtc. sealed boxes not only exacerbate the problem, but RAISE the resonant frequency too, BUT that sort of resonance is less audible AND ported speakers have THAT form of resonance too on top of the box resonance they add, so that's a false equivalency unless someone is cramming a woofer in too small of a box which i wouldn't do. that's why i won't buy a woofer that doesn't give its parameters no matter how great reviews say it is. (eg. hifonics brutus)

you can attack the issue from any angle you chose, but can never change the fact that TUNED PORTS are DESIGNED to distort the signal. that's their purpose, and an unholy one at that as far as i'm concerned and i've had this same argument literally dozens of times and i'm never budging. no matter WHAT words you try to use, it will NEVER change what my ears hear.

before they become totally extinct, i ordered a JBL GT5-15 afor about $75 shipped from jet.com. i was expecting i'd have to pay over $80 now, so i'm happy to be close to what i was planning on paying sonicelectronix who sold out about 2 weeks ago. tonight i did some research on using polyfill. apparently, using it to convert soundwaves into heat tricks small sealed boxes into thinking they're up to 40% larger as long as you don't use more than 1.5 pounds per cubic foot, or 1 pound per cubic foot in larger boxes. i figure i'll err on the safe side, and use 2 pounds for the roughly 2 cubic foot box i intend to use, though, at this point, i'm not ruling out going the fiberglass route to lower weight and get closer to a .7 QTC which would not only tame the resonance above 50Hz, but greatly extend the LFs for a flatter response, but when i ran the numbers, i found i could get these "free dB" by acoustuffing as well as save about $10 by not using egg crate mattress liner as acoustic foam.

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the difference isn't huge, but it's a win win win for cost, extension and taming resonance. at this point though, going the fiberglass is more of a possibility as it's too late in the season to get rolling now and i have about 4 months to tinker until it starts getting warm again where i was aiming to get rolling asap a couple months back while my finances were still catching up to the storage unit fines.

i'm also likely to drop the AGM battery plan and invest in lithium ion to save weight too as well as possibly improve charging. i've been trying to charge just ONE 18Ah battery allegedly at an 80%+ charge with my battery tender charger for the better part of 12+ hours now over 3 days and it still hasn't fully charged. at that rate, it'd take more than a week to charge 3-4 way too heavy batteries.

OH YEAH! just stumbled on this hifi update of a classic...
THAT is the very kind of hard thumping track ported subs just can't right, especially from an uncompressed CD. i don't hear ANY boom in that track, and hopefully, won't hear any on my system either, though i do expect a slight thickening from that big old heavy 15... but no boom. it sounds pretty darn good on just the proels streaming whatever fidelity already.

Many years ago I opened a pair of sealed speaker enclosures from identical-sounding speakers and removed the acoustical absorbent material from one of them. Then it sounded hollow and echoey but the bass was not improved. I measured a very small difference in the resonant frequency (acoustical material inside reduced it a little).

Your JBL 15" speaker will sound pretty good if the -3dB output is about 32Hz as you show but I don't think it will be that low.

like i said... it will be GOOD ENOUGH for me. i've done MOST of my listening to music on minimonitors with no sub at all. a 92dB 15" with MAYBE 300w (actual) should do more than enough of a good job informing dancers that there really is a bassline for every beat, and i want said bass to sound realistic, not loud and deep. i want bass drums, like in the track above or in new order's blue monday to thump without blurring. as "impressive" as ported speakers are in the bass department, they just don't sound realistic with dynamic fast transients. the rhythm section is MOST IMPORTANT to me. that's why soft domes that take the edge off cowbells etc. annoy me too, and why i consider maggies to be far more realistic sounding than even $20k B&Ws which just can't snap a bass drum with anything close to the speed and definition of a virtually weightless planar driver. to my ears, that effortless speed sounds the most realistic (by the driver's mass, the "box" and any resonance sources simply getting out of the way) and unlike any other speaker i've ever heard, maggie MG12s really made it sound like i might be listening to singers in another room when i gave a pair a quick audition. BIG maggies sound like shrill tinfoil crap though. i had to stop listening to a hifi japanese import of dark side of the moon on megabuck maggies which were stabbing my ears with a screwdriver so to speak.

i've been looking for uncompressed tracks that have challenging bass dynamics to show off with like tracks that thump or that have extremely textured bass like dubstep. one of the tracks i bought last night was


which has TONS of texture & low level detail, even more than can be heard here. that's why i like acoustic suspension. ports just can't do that. that's not their thing... sloppy booming is. how anyone can even tolerate that crap will always elude me.

OK... here's a higher res version.


it makes a good analogy between bass reflex and acoustic suspension which has the speed & clarity of the higher res version where ports sound muddy like the lofi version. listen to just how DRY that bass sounds! you need 8s to really get that right. i bet maggies could bite your head off with THAT track. LOL

it might slow my progress down and even possibly cost more money trying to get a custom cut woofer ring, but i'm starting to really think fiberglass is the way to go. i was already going to have to use fiberglass, if not carbon fiber, to make the "light shields" for all of the edges to prevent light spillage, but if i also apply the tech to a sub cabinet, and probably custom mains too (which will also save weight), i can be free of the 1.9 cubic foot limitation of my sub box and fill the available space up much more efficiently as well as hug the frame better, again, saving weight on wood framing and if i built a 23" x 25" x 28" sub box, that would give me about 9.3 cubic feet and THIS curve improvement with a .794 QTC even if it's larger than JBL recommends...

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while the bass would probably be looser without as tight an air spring, a "free" 5-6dB increase at 20Hz (with a not at all shabby -8dB @ 20Hz with a single driver) is nothing to sneeze at, and that was calculated without factoring polyfill into the equation which would get another hair closer to the .707 QTC ideal. seeing that i have several free months to work this out, it might be worth the effort to both lower my system weight and increase output too. a wood sub box, the AGM batteries i was planning to start with and wood framing too would all easily add 100 pounds to my system weight.

in rethinking the design too... i've thought about building sealed mains with the air motion tweeters i intended, and putting them on top of the subs pointing up so that it would be easier to pull them out for true stereo use. those "little" proels are heavy buggers despite their plastic cabinets. i bet a lot of that is compression driver/magnet weight that would be greatly reduced too with air motion tweeters.

the final design is still fluid and in motion and always looking for improvements with the materials i have to work with.

if i go the fiberglass route though, i might just go all out with up to 8 x 12" subs for higher efficiency and to tighten the bass up as well as upgrade to 4 vs 2 mains, and as originally planned, just use the proels/sub setup as a quick fix. this is all based on whether or not i get my income improved though. 4 air motion tweeters alone would cost about $280 and i haven't even tried to figure out how much a lithium ion battery upgrade would cost, but i can tell you now, it's NOT $100!

the more serious i get about the design, the faster the dollars add up exponentially.

got the sub today. it's BEEFY! it weighs a ton, has a cool rubber coating on the magnet, and both the cone and surround are extra thick. so, the cone is not only large, it's massive too, but apparently, it uses brute force (magnet) to make it move. i doubt the cone will be flexing much.

i have two pounds of polyfill on order, and after i pay my bills & get paid next week, i'll get the box, and probably a drill & soldering iron to start putting the sub and trailer frame together. between the amp, mains, sub/box and battery(ies), this is going to be one freakin' heavy trailer to pull. redoing everything in fiberglass & li-ion for summer is almost mandatory considering how far i have to ride to get into town.

got the sub yesterday and have it hooked up free air. FORTUNATELY, the amp DOES work in bi-amp mode which the owners manual chooses to gloss over in favor of using the amp with passive subs in line with the mains for some weird reason when bi-amping makes much more sense.

unfortunately, either my PC's soundcard, or more likely the amp, is infrasonic filtered. i'm trying to loosen the surround before i box it up, and even 10Hz tones were audible. just like with the hifonics 12" subs i used to have, it takes an 8hz tone to move the sub more or less silently, but unlike my panasonic 100wpc class D receiver being driven by a media player, i can't get the sub to really wobble like i could with the hifonics which seemed to move a good half inch where it feels like the JBL is moving closer to 1/8".

while i'm updating, this is just how much bass the JBL will be adding to my proels which i've decided i'll likely cross over at 100Hz, but am doing it at 120Hz now because it's clearly marked on the amp.

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There's no logical reason for this extreme annoyance of an idea. My bike trailer speakers are only 7W per side, and only active when I'm off the road.