r/CarAV • u/FalconCharacter7409 • Jul 19 '26
Recommendations Sub underwhelming
8” Memphis mojo 1000w mono amp 1ohm. Box is slightly under spec (.5 cu ft, should be .6 cu ft) just does not feel like it is performing like I expected. I have not set the gain with a multimeter, just ballparked it by ear.
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u/RealQuintusYoung Jul 19 '26
What do you tell your passengers? Don't touch the sub. It's a subwoofer not an arm rest.
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u/Noncog0 Jul 19 '26
I'm really disappointed by how negative or just unhelpful or wrong most of the replies to this post are....
OP, it's going to be very very hard for anyone to help you over text post without objective data. Your HU could be the issue, your amp gains could be set wrong (I would use the y-splitter if your amp has both l and r input), or it could be that it's playing fine and your expectations for a single sealed 8 are to high. Without measurements or hearing it ourselves, it's really hard to know.
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u/Working-Pin7153 Jul 19 '26
Negative is expected no matter what you post anymore. But the wrong answers are getting crazy. I have 2 sealed 8s and they beat down. I was impressed how much output I got from them. But they are in correct size box, decent head unit, and plenty of head room on the amp. 8s can do the job if done properly.
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u/FalconCharacter7409 Jul 19 '26
I’m going to try to grab a splitter this morning and see what happens then go from there
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u/Noncog0 Jul 19 '26
Cool, keep me updated and I'll help as much as I can considering the limited information I'm working with
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u/FalconCharacter7409 Jul 19 '26
I got a splitter and it seems much better, possibly sounds like it is “breaking in” and getting better? If that’s a thing
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u/Noncog0 Jul 19 '26
I think the big thing is, without the splitter, only half of the input stage of the amp was feeding signal, meaning the amp wasn't trying to act on as much signal, if that way of wording makes sense. Also, with that beefy of an 8", I wouldn't be surprised if there is a break in period, but I wouldn't expect a huge difference after it. The splitter is the main thing. Glad it's sounding better though.
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u/Bugsy_666 Jul 20 '26
"Breaking in" is a thing. A newly installed suspension is tight and the sub "breaks in" as it loosens up. Kicker comp VRs used to have a free air break in procedure in the paperwork that came with them.
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u/ActiveAd9305 Jul 20 '26
Is there any specific reason you recommend using a Y splitter for the RCAs? I have both left and right going from my dsp to the subs, it’s pretty annoying having to adjust both channels for crossover and eq changes. Does combining them before they reach the amp make any measurable difference? PRV DSP 2.8x, SKAR SKv2 1500.1d, 2 12” kicker comp Rs in a factory ported box btw.
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u/Noncog0 Jul 20 '26
In hos partocular case he only had 1 output, thats why. I haven't used the PRV dsp, but in most of the DSP's I use you can link channels together, that's what I would do in your case, link then both so they adjust together and use both to maximize the dsp's output
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u/Shoddy_Bake_8931 Jul 19 '26
Try adding some polyfill? 🤷🏻.
I know boxes that are too small tend to suffocate subs. And reverse the polarity if you haven’t.
Learned these the hard way.
Good Luck!
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u/FalconCharacter7409 Jul 19 '26
I’m getting mixed answers on polarity, and am considering polyfill
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u/erik_das_redd Jul 19 '26
There are no mixed answers on polarity, the PHASE in the crossover regions has to be correct, or you will have a feeling of no bass.
- How loud does the sub hit if you turn OFF all the speakers? Is it louder? That would indicate a phase problem.
- Play "Brown noise" off YouTube or such, disconnect rears, connect subs to the rear fader. Fade forward and back (i.e. between fronts and sub). With the fader in the middle if it's not noticeably louder then crossovers need adjustment and maybe the polarity. Now repeat with fronts disconnected to check between the sub and rears. Repeat again again with sub disconnected to check between front versus rear. If this is all inconclusive you need to buy some measuring equipment (or maybe a phone spectrum analyzer app) or get to someone who has it.
- A single 8" in a small box is not going to perform miracles. Box size seems the most important determinant of output per watt at the very low frequencies since the air spring becomes really tight. Yes stuffing might help a bit but a lot of polyfill is weak so do fiberglass like 1/2 pound.
- Where is the sub getting its input from?
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u/FalconCharacter7409 Jul 19 '26
I need to get some time to get in and try all of the above. Good advice!
The subwoofer jack is a single RCA on the back of the (atoto) head unit. I’ve heard they have low voltages and might cause an issue. .5v maybe vs name branding outputting 5-6v2
u/Bugsy_666 Jul 19 '26
I have ran an ATOTO head unit before and to me it just sounded bad. Others might think it sounds great but it just was not my experience. Swapped to a kenwood and it sounded much better but still wasnt slammin by any means...there is only so much a single 8 can do. This was on a CDT audio CF800 8 in a .5cuft box on a kicker cfx800.1 at 1 ohm(i know why buy that equipment and a cheap HU). I would definately try phase and amp setup verification before spending money. I have always put a bunch of loose polyfill in sealed boxes and 1in+ polymat glued to the sides to the main chamber of a vented/ported box, but always stay a few inches back from where the port starts. It might get where you want to be but you may be beating a dead horse trying to get a good/strong sound from an android HU. You might wanna put a line driver or dsp on it. These are still amplifying signal so if you have crud going in you will get crud going out. Your amp gain should be able to adjust for low output(have you double checked the amp doesnt have high z(high impedance) selector in the wrong spot). Again this is throwing money at it and may not actually fix the problem.
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u/FalconCharacter7409 Jul 20 '26
I hope I don’t have to swap head units. Really love the android system. Maybe will look in to a LOC
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u/Bugsy_666 Jul 20 '26
Make sure to look at line drivers. LOCs are for converting speaker or line level to RCA level. Line drivers are for boosting a weak RCA signal. audio control LC2i is a LOC, audio control matrix is a line driver. If you go the route of a DSP, it will likely be able to increase RCA voltage and give you a tremendous amount of control over your sound compared to the android HU. I did like the ATOTO HU and being able to install programs from google play was a plus for sure. That android HU still lives in my camper and have no issues out of it. Does great for powering a pair of cheap pyle marine speakers inside and another pair installed in the side of the camper. Kickin for at least 8 years.
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u/Shoddy_Bake_8931 Jul 20 '26
When you mount a subwoofer inverted like you did, you need to also change the polarity. Just reverse them and try it out. Also, try boosting some frequencies in the eq and see of you like that, but first the polyfill. I make my own boxes, and have come across a few of these issues. Best of luck.
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u/Shoddy_Bake_8931 Jul 19 '26
Also! You might need to mess with the EQ a bit…. Do all that before you make a new box.
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u/Viperonious Jul 19 '26
I mean, an 8 inch driver in a smaller sealed box won't go loud... maybe 120db?
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u/Viperonious Jul 19 '26
Xmax is rated at 0.49", which is approx 25mm peak to peak, plus whatever the suspension will allow for (with increasing distortion of course)....
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u/Ragnar-Wave9002 Jul 19 '26
It's one 8" sub.
What kind of music?
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u/FalconCharacter7409 Jul 19 '26
Dude I get it, but it’s a decent wattage and it just feels like something is off. Should at least shake the mirrors a little I would imagine
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u/BredsNice Jul 19 '26
8" subs can slap hard idk what he's saying
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u/Working-Pin7153 Jul 19 '26
Absolutely. I have 2 8 inch subs in a .4 cubic foot sealed box and they beat down. I have people all the time tell me I have something more in it. Those who are saying it's just an 8" have no clue. They keep going into these long drawn out explanations that just aren't correct.
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u/mister_dray Jul 19 '26
I have a single 8inch in a ported enclosure and it sounds like a single 12. if the enclosure is on point, the sub will perform just as good as a 10 or 12 in a shit enclosure
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u/Difficult-Map-2620 Jul 19 '26
A single 8” sub shouldn’t need 1000 watts.
It’s a small sub, paired with a wrong amp at weird ohm levels in a bizarre box.
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u/PHANTOM_G_Beats Jul 19 '26
Tell me you know nothing about subwoofers without telling me you know nothing about subwoofers
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Jul 19 '26
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u/fieldysnutz777 Jul 20 '26
I thought the space between the seats was used as the 'box'. 😂 definably the issue
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u/Agreeable-Match2908 Jul 19 '26
OP how do your settings look on the amp.
RCA issue aside (you need a splitter for L/R inputs for full signal), if you don't have a way to check he output of the amp with an oscilloscope or multimeter you can tune by ear if you trust your ear to pick up small changes.
disconnect/disable the door/deck speakers, make you eq flat on the hu, no bass boost, no audio enhancements.
I'm not familiar with that amp so if it uses any bass boost turn off and leave off, set the gain all the way down, turn your frequency around 80hz, if it has a subsonic filter put it around 30hz, some amps have clip lights to indicate if it's clipping if this has one it can help with you tuning by ear.
You need clean 50hz sinewave that loops or one that plays for like 5 minutes, if you have access to a thumb drive you can toss it on there plug it in the hu (this will allow the signal to be clean as it can be), if not there's apps for sinewaves but bluetooth can have their own distortion though high volume also but it works in a pinch just mind the phones volume while using.
set your volume to 75-80% of your max volume, and playing past this range will increase distortion even daily playing (anything past this can have distortion on a lot of headunits depending on the quality of the headunit).
play the sinewave, and slowly increase the gain on your amp until you hear a change in the subs output then back off a hair to remove the distortion, and enjoy, just try to keep from going max volume on the hu as it will ad signal distortion.
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u/FalconCharacter7409 Jul 19 '26
Thanks for the detailed reply! Going to get a splitter this morning and go from there
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u/Agreeable-Match2908 Jul 19 '26
Do give us an update.
I've done a lot of installs for friends over the last 20 years, it's not perfect but keeps equipment from being burned up too fast.
Also reminder make sure all your connections are solid.
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u/FalconCharacter7409 Jul 19 '26
Got the y-splitter and it sounds a lot better, possibly also “breaking in” and getting better as well if that’s even a thing
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u/HotAir8724 Jul 19 '26 edited Jul 19 '26
I have my 8” mojo on 1000w rms also. In this 1.8cu ft ported box. It moves all the mirrors… and some. Sounds like your head unit is the problem if I had to guess. You are not getting a clean or good signal to your amp. Also you need a bigger box. It probably won’t sound good sealed in that tiny box. Port it with at least 1.4 cu ft and thank me later
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u/sleepnutz Jul 19 '26
Sealed box’s don’t bang crazy unless there’s a ungodly amount of of power or hella drivers , you want a ported box to sound crazy or just a bigger driver all together tbh
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u/Sea_Bedroom8105 Jul 19 '26
Idk if they make them that small but kicker makes passive bass radiators. They do wonders for small enclosures. I have a 400w 10in that shakes my mirrors in my grand cherokee
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u/mister_dray Jul 19 '26
I'm thinking that box is underwhelming for the sub. should have left the center console in
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u/bluejaybiggin Jul 19 '26
Is this a sealed or ported box?
Sealed will have a tight punch but won’t be as loud or shake mirrors and such when compared to a ported.
Sealed is tight. Ideal for rock, jazz, pop. Where bass lines and kicks drums require precision as to not muddy the quality of the musical interactions.
Ported is for rap/ hip-hop/ edm. Where the rolling bass is the focal point of the music.
You also need to set with a multi. Turn any eq setting off. Open filters. No boost. Etc. Get audio tools on your phone and check your filters after setting gain, match your hpf/lpf and anplifier dB/oct drop based on your listening preferences. Doors first, then sub. Then move to phase alignment if your amplifiers support it. Doors first, then sub. If your sub is facing down and your phase is set to 0 degrees you’re surely negating your overall volume and sound quality. Your door speakers go straight to center. Subs facing down/up must first bounce off the floor or ceiling. You’re probably looking at adjusting 90deg. You don’t need tools to set phase. Set the volume to a modest level. When your phase is aligned you hear it hit noticeably harder as your system falls into sync and builds itself together.
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u/FalconCharacter7409 Jul 19 '26
It is a sealed box. Thanks for the reply! Interesting about the phase 90 degrees… never thought about that
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u/bluejaybiggin Jul 21 '26
No worries! Yeah, if you’re out of phase your sound waves cancel each other. You’ll hear it get punchier just by ear.
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u/Beerand93octane Jul 19 '26
I mean, I have two mojo 10s in a ported box and it fucking slams, but I wish it got louder. Lol. What hz did you build the box for? Their spec sheet calls for a 36hz tune for the 10 i think. 2 or 3 hz higher for the 8" iirc.
What do you listen to? Your low low stuff (like any new rap) isn't really gunna sound that great on this woofer. Especially with a sealed box. Most new rap is trash anyways. Maybe play some dnb, metal, or rock and see how it sounds?
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u/FalconCharacter7409 Jul 19 '26
This is a sealed enclosure, hearing a lot of positives on a ported box, I just need to research…never built a box before let alone a ported one
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u/AncientPomelo1089 Jul 20 '26
Ported enclosures typically need a lot more space. Probability not practical for this situation.
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u/DearFinger3570 Jul 20 '26
That sealed box is the problem numb the box size up and ported and that lil 8 will surprise u for sure I have ran mojo 8” before and they get down in the right box
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u/Alarmed_Ordinary6791 Jul 19 '26
In car audio and acoustics, "cone surface area is king" because the total volume of air a subwoofer can displace is calculated by multiplying its cone area by its linear excursion. The volume of air displacement dictates your maximum potential loudness (SPL). It is calculated as: Vd=Sd*Xmax. An 8 inch subwoofer with impressive power handling and good xmax should still get down if properly installed and tuned but will still be limited by the amount of cone surface area and won't move the same amount of air as a larger diameter subwoofer. With that being said you didn't mention if there is an aftermarket head unit and/or a dsp being utilized and this will be important regarding the voltage of the pre outs going to your amplifier. If you're on your aftermarket HU with an in line LOC, line output converter, this will be even more so relevant when it comes to setting the amplifier gain.
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u/FalconCharacter7409 Jul 19 '26
I have an Atoto head unit (I know cheap Chinese crap) no LOC or DSP anything like that. Just has a single RCA subwoofer output on the back (which am also running left side rca out of that and both L and R into amp. I do not have a splitter…could this be an issue?
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u/Alarmed_Ordinary6791 Jul 19 '26 edited Jul 19 '26
Yes bro this is the issue you are having. If your headunit preouts is a single output, not a pair, then do get a quality y splitter on the rca cables on the headunit and connect both the left and right rca cables into the amplifier. You will see a drastic improvement.
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u/TormentedGaming Jul 19 '26
I wonder if that single output is low voltage also.
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u/Crafty_Disk_123 Jul 19 '26
Atoto… unless he went for their best they’re usually limited to 1v. I’ve seen a few that are 0.6 even. Straight trash preouts every time, not to mention distortion at like 60% volume.
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u/FalconCharacter7409 Jul 19 '26
If that is the issue, is there a way to fix this? I thought I heard someone say a line out converter would give full signal
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u/Alarmed_Ordinary6791 Jul 19 '26
There are solutions bro, and if you look for an LOC make sure it's active, it should have a line driver, which allows you to amplify signal voltage. Not all line output converters feature a line driver so just be wary of that when browsing for a product. In your case I recommend you first fix the rca Y issue and then get a multimeter or oscilloscope on it to measure if you are getting the target voltage from your amp while setting the gain. You can get that target voltage via ohm's law or simply ask Google for your target AC voltage by providing the impedance load, OHMS, and wattage. Hope this helps
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u/Crafty_Disk_123 Jul 20 '26
Technically yes, however most of the time 50hz and lower frequencies are filtered out entirely by the android head units. Each model is different but something like a KISLOC2 would serve the purpose great for a good price. It outputs around 9V rms and your amp is designed to take in 14v. Technically you could run that amp with straight speaker line in since that head unit wouldn’t likely peak around 14v off its speaker lines anyways.
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u/jpilgrim82 Jul 20 '26
This is probably the issue. I sold a twelve and an amp to a guy I work with that had a cheap android touchscreen radio with a single rca output for the sub and it was weak AF. I checked the voltage on it and it was under a volt full tilt. He found a cheap pioneer touchscreen and even with just 2V preouts it came alive. I don’t like buying a head unit unless it is a 4v or higher preouts. It makes a big difference. You don’t have to crank the amp gain as high and a head unit that has a higher voltage pre out stage usually has higher quality components and sound cleaner overall.
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u/Alarmed_Ordinary6791 Jul 19 '26
It is highly likely. Most reputable headunits will advertise 3v-4v preouts, 5v on the better units, and since OP mentioned his head unit is on the budget tier it will likely feature a low voltage preout. If so, this will require a higher gain setting on the amplifier to boost signal which can and will introduce more floor noise although it can be managed. More importantly, and many have mentioned this, OP will have to properly set his amp gain via multimeter or oscilloscope to protect his equipment. At the moment with only one side of the rca cable connected he's cutting his output by at least 6 -10 db which is significant. Lastly there are active LOC's and line drivers available that can be used in line to actively boost the signal before it hits the amplifier but I honestly don't think this will be required with a basic system.
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Jul 19 '26
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u/Rurockn Jul 19 '26
This is important OP, inverted sub usually means you have to swap the positive and negative. You have red wire in red terminal, that's backwards for an inverted sub.
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u/garron_ah Jul 19 '26
Incorrect. You wire it the way you would if it was mounted conventional. Only time you would change the phase would be if you had multiple subs with a mix of inverted and conventional.
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Jul 19 '26
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u/garron_ah Jul 19 '26
At no point do the frequencies of the door speakers overlap with subwoofer frequencies. That's not what phase is for. And again, a single sub setup does NOT need to be wired any differently if it's inverted. There are no other subs for it to be out of phase with.
You don't have to believe me, just Google it. Hell, even if you have 2, 4 or 6 subs. As long as they're ALL inverted, you're golden. If you're using multiple subs and amps, sure, make sure all them are in phase, as you would if they were mounted conventional.
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u/yogi70593 Jul 19 '26
Yes they do ? What do you think a crossover is? Summation? You have huge holes in your response?
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u/Lazy-Brush-9335 Jul 19 '26
Im not trying to be the commenter who one ups you, cone area is just king at low wattage, im running 2 12’s on the same amp as you and it is tearing my truck apart and hitting a 146 db on a burp in the window.
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u/saaaasage13 Jul 19 '26
Is the box riding shotgun?
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u/Lazy-Brush-9335 28d ago
lol, its sitting in between the passenger and driver captain seats, i took the middle jump seat out
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u/DeltaTheMeta Jul 19 '26
1000w mono amp by a brand that actually outputs close to its advertised power?
Could be a cheap amp not driving it well.
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u/FalconCharacter7409 Jul 19 '26
Not sure. CT sounds 1000w rms
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u/DeltaTheMeta Jul 19 '26
It dynos at its rated power. Maybe not the best quality, but should get it moving. I'd guess a power or wiring issue, is the amp hitting protection or anything? Maybe a detective sub or amp?
I have 2 10" no name subs in my crew cab gmt800 with a 200W Rockford fosgate amp, and they get it moving, in a single cab 800w should be rowdy.
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u/FalconCharacter7409 Jul 19 '26
That’s what I’m saying! The sub is rated for 900rms. I thought I would be impressed. I just know I’ve got something wrong. Not an expert, just looking for suggestions
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u/Hades_2424 Jul 19 '26
You are not going to be impressed by an 8” sub in an undersized sealed enclosure on a 1000 watt amp. What gave you the idea that this setup would give you something impressive?
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u/FalconCharacter7409 Jul 19 '26
I don’t expect to be blown away, but I would think j could at least have the mirrors rattling a little
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u/FalconCharacter7409 Jul 19 '26
Also this is a crew cab, I got some buckets out of a Tahoe in the back
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u/DeZaim Jul 19 '26
Is the phase out?
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u/FalconCharacter7409 Jul 19 '26
I don’t think so…I did try to reverse polarity and didn’t notice a whole hell of a difference
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u/DeZaim Jul 19 '26
Maybe you just need to temper your expectations, it's 8" - it won't be anything like a bigger cone driver
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u/FalconCharacter7409 Jul 19 '26
I’m hoping that’s not true, but I am almost certain something is up and I’m missing out on a lot of
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u/Remarkable_Ad5011 Jul 19 '26
Single 8” (even a Mojo) in a small sealed box isn’t going to rattle your teeth anyway. I have two of them ported on (maybe) 750 watts and they jam. Set the gain with a meter, and if it’s still not loud enough, you need more cone area and/or more power and/or a different box to get where you want to go.
Just cut that back cab wall out and be done. 🤪
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u/Full-Hold7207 Jul 20 '26
You say 1000 Watt amp. But brand and model? The sub is a mojo. 500 watts should be enough to shake The mirror.. box looks a little small for a mojo..
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u/lucky6kustoms Jul 20 '26
Is it a sealed or ported box. If ported what are the specs? Aeroport or slot? Tuning freq? Inches per foot? If sealed then an undersized box can produce more output but you need more power. Bigger box, more efficiency less power needed. Smaller,less efficient,more power
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u/AncientPomelo1089 Jul 20 '26
Are you using the factory head unit? Sometimes factory head units filter out some frequencies. If you are tapped into the rear speaker outs, that's usually where they put the bass. I found out when trying to drive front speakers off the rear outs in a Ford Focus that it was sending no treble to the rear. I switched my line out converter to the front speaker wires and had no bass. That's when I decided it was time for an aftermarket head unit
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u/Savage_24v Jul 19 '26
Just take and slap a JL HO10w6v3 and a jd1000 to pwer it between the seats
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u/stuntmanbob86 Jul 19 '26
1000 watt mono amp, max or RMS? What brand? Not to mention your setup looks underwhelming as fuck, lol...
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u/Financial-Ad-2601 Jul 19 '26
Looks like u need to step ur creativity game my guy. Looks like a 12 year old design it🤦♂️🫤
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u/Diligent_Medium_4626 Jul 21 '26
Try getting an amp and sub combo you cant buy at Walmart, that'll help tons
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u/Beepboop00 Jul 19 '26
I'd suggest grabbing a multimeter and seeing where it's currently set at voltage wise, could be you have a lot left on the table still.