sub problem (i think)

[alpine]

good evening fellow tuners.

i'm currently having some problems i believe with my sub woofers. i seem to be getting a scratching sound when i play. this noise seems to happen sporadically, when this happens the bass sounds very low and soft like if you were to cut the signal your pre-amp or head unit, but when the volume is raised higher to around 20 out of 35 the bass seems to dip and peak in frequency like its being cut and then boosted. the subs in question are a pair of kenwood KFC-W3011 wired at 8ohms on a alpine mrp-m2000 mono. i have no idea whats causing the problem changed RCA and nothing changed even wired over the box and subs and same problem.

thanks for the help.

[nervewrecker]

At all frequencies or just the low notes?

[alpine]

At all frequencies or just the low notes?

just low notes..

[nervewrecker]

What's your box tuning frequency and is it a flapping sound?

[kurpal_v2]

Could be the sub bottoming out.



Box could be too big/ port tuned too high/ crossover set wrongyou have too much power going to the sub/it have a jumbie in yuh car

[alpine]

not a flapping sound, the scratching is only audible when its played at low volumes. when the volume goes up to around 20 the bass starts the peak and drop.

if i remember the correctly the box is tuned to 40hz if i'm not mistake.
LPF on the mono is set to 80hz
gain a little less than 1/4.

hoping is not a jumbie that would serious problems.

[kurpal_v2]

Oh, I misread your first post, thought you Said at low frequencies.

In any case IMO scraping from a sub usually relates to coil damage, my suggestion is to take both subs out from the box and determine if its one or both. If its one sub you have a faulty sub, it's its both subs you have a faulty amp.

And if the amp making noise, yuh have jumbie

[alpine]

thanks for the advice kurpal_v2. really hoping is not the amp..

when you say determine, should i connection each sub 1 at a time to the amp to determine which sub is making the noise?

[kurpal_v2]

Yes, that would be easiest.


I highly dout it's the amp.

[nervewrecker]

what size sub and how big is the port?

where you high pass filter set btw?

at low freq and a tuning freq of 40hz.

[alpine]

what size sub and how big is the port?

where you high pass filter set btw?

at low freq and a tuning freq of 40hz.

12" subs using PVC port 3"wide 7"long if i remember correctly (stone age technology).
i wasn't the one who got this box built thats why i was planning to get it rebuilt to around 35hz.
high pass, i can't remember correctly where it was at, if i remember correctly though it should be at around 120hz

[nervewrecker]

how much 12's and how much 3" port?
high pass at 120hz btw....wdmc kinda amp is that? a 4 channel? drop it to approx a 38hz and report back here.

[alpine]

how much 12's and how much 3" port?
high pass at 120hz btw....wdmc kinda amp is that? a 4 channel? drop it to approx a 38hz and report back here.

confused as to why would i drop the HPF on my mids amp to 38hz? i would try to drop it to 38hz on my mono LPF if that is what you mean cause my mono has no HPF only a subsonic filter. two 12" with two 3" ports 1 on each side. box is walled off in the center ports are located at each side of the wall.

[nervewrecker]

hpf is subsonic filter when we talk bass.

A 3" port kinda small for a box with a 12" though. Search for my thread titled "too small of a port" and you will get the drift.

But just for the heck of it, yank those 12's outa there, unplug the rca's to the mids amp (with the music off and make sure it not touching anywhere) and connect them. Yea, we gonna free air those muthafcukers butttttttttttttttttt....lets not damage them, we just want to eliminate that its not the subs fcuked. Start from volume 0 and gradually increase till you have some excusrion goin on there. If it makes the knocking noise (provided its not your coil bobbin hitting the back plate) we know its the box / port etc. You not looking for max excusrion eh.

[Firewall]

Recheck and re-torque ALL your connections.

Also verify the subs are wired to 8ohms.

Could possibly be something in the gap.

[kurpal_v2]

hpf is subsonic filter when we talk bass.

A 3" port kinda small for a box with a 12" though. Search for my thread titled "too small of a port" and you will get the drift.

But just for the heck of it, yank those 12's outa there, unplug the rca's to the mids amp (with the music off and make sure it not touching anywhere) and connect them. Yea, we gonna free air those muthafcukers butttttttttttttttttt....lets not damage them, we just want to eliminate that its not the subs fcuked. Start from volume 0 and gradually increase till you have some excusrion goin on there. If it makes the knocking noise (provided its not your coil bobbin hitting the back plate) we know its the box / port etc. You not looking for max excusrion eh.

I'd have to say its not a box/ port problem because he said it occurred at a low volume. If was a high volume and he was hearing chuffing or port noise.

Scratching is coil.

[alpine]

I'd have to say its not a box/ port problem because he said it occurred at a low volume. If was a high volume and he was hearing chuffing or port noise.

Scratching is coil.

it mostly happens at a low volume. at high volumes the bass would just trip from playing loud to soft and vise versa. checked to see if was the amp that was tripping on and off but it wasn't.

this scratching and peaks in loudness only happens on rear occasions and not always.
as kurpal_v2 said it might be a problem with the coils in my subs i will have to check them out tomorrow.

and nervewrecker the subsonic filter on my mono only goes from 0-30 (0-15-30) its a switch. currently its set to 30hz.

[rollingstock]

Pair of subs? Enclosure separated internally or one big enclosure for both speakers? Had this happen before, one sub was damaged, other one was pushing it around like a passive and unraveling coil made a racket (if both speakers are in one chamber) But definitely sounds like a sub problem.

[alpine]

Pair of subs? Enclosure separated internally or one big enclosure for both speakers? Had this happen before, one sub was damaged, other one was pushing it around like a passive and unraveling coil made a racket (if both speakers are in one chamber) But definitely sounds like a sub problem.

pair of subs. each sub is separated from each other within the enclosure and each sub has its own port.

[rollingstock]

Where yuh from? Could lend you a pair of PG Tantrums in a box, if same problem then amp/connection/tuning/jumbie

[alpine]

Where yuh from? Could lend you a pair of PG Tantrums in a box, if same problem then amp/connection/tuning/jumbie

down south barrackpore side. down in bush

tomorrow i going and do what kurpal_v2 suggested and test each sub 1 by one and see.

the thing i don't get is why it scratching sometimes and not right though all the time.

[rollingstock]

De phoq! I not in south anymore, hard luck dey.

Yeah do as kurps say, if nothing definitive, borrow a sub and box and run for a few days and see if the problem returns with that set up, would most likely point at something else.

[kurpal_v2]

Where yuh from? Could lend you a pair of PG Tantrums in a box, if same problem then amp/connection/tuning/jumbie

down south barrackpore side. down in bush

tomorrow i going and do what kurpal_v2 suggested and test each sub 1 by one and see.

the thing i don't get is why it scratching sometimes and not right though all the time.

Barrackpore ain't bush I from debe, same neck of the woods.


I don't get the scratching/ high low output thing either, maybe is a jumbie dj going ham

[alpine]

Barrackpore ain't bush I from debe, same neck of the woods.


I don't get the scratching/ high low output thing either, maybe is a jumbie dj going ham

doh make them joke they kurpal_v2 i feel i have to pass by you for you to run this jumbie away inno.. i feel is either the sub or some wire probably slack somewhere, cause i high doubting its the amp. Christmas time to make noise. and my sub looking to give me old noise during this kinda season.

[kurpal_v2]

Reason why I don't think it's a connection is because of the noises, that seems mechanical but the output thing is usually signal based, which is why this interested me. If you don't get through, weekend I could take a look for you.


Doesn't hurt to recheck your connections doh, grounds etc.

[rollingstock]

^ Was now about to post that, my answer to every car audio hiccup "Check yuh grounds dan"

[kurpal_v2]

I have to recheck ALL my grounds right now, I'm getting a slight dip in my headlights when I apply the brakes at night.


Them kinda electrical bugs does get me frighten after having my battery died quite down Mayaro, nothing like the drive back from Mayaro to debe knowing you have no battery

[alpine]

will re-check my grounds, recently re-did my grounds in the engine area upgraded from what seems to be 10 gauge to 4 gauge stinger hyper flex was opting for the shok but the price dam.

to-do-list
check grounds
check speaker

[Brian Steele]

Sounds to me like one of the tinsel leads for one or both of those subs is damaged. Either that or perhaps one of the connections from the tinsel leads into the voice coil is broken.

[alpine]

results from testing.

Free Air test
Sub 1 No Audible noise
Sub 2 No Audible noise
Wired Both back in series No noise from subs.

In Box Test
Sub 1 Noise present
Sub 2 Noise Present
Wired both back in series noise is present.

free air no scratching noise is heard, but when they are placed inside the box the noise can be heard.

it seems one sub is making the scratching noise slightly louder than other when I tested them individually in the boxes.