Blown sub - very odd circumstances (update II: It's the sub channel on the HU)

[VexXx Dogg]

Guys,

I have a small setup in my truck (sportero), it's tuned to be a little bass heavy, but I also properly dialled in the input sensitivity and don't drive to (audible) distortion. I've blown quite a couple subs in my time.

Today, I played music to work, sub was fine. music was about 40% vol, I normally play at 75%.
Left work early about 1:00 PM. Inside the van was STINK hot. Music came on with ignition, volume at about 30%. No bass.

I rebooted the deck, thought the heat caused an operating glitch. The sub came on kinda scratchy. Thought it was the deck acting out, and I even reset the HU in the hope that it was a snafu. I should have figured it out

WHen I got home I pulled the back seat and the sub was stuck all the way down. It's not that the box shifted, it's locked pretty tightly in there and I've had this setup for close to 4 years with no problem.

Can excessive internal heat cause this kind of problem? Bear in mind the internal temps can reach well over 70C at midday.

Odd.

[racedriverpro]

Nah simply a slow burn on the coil...and that location seems to be poorly ventilated which can cause heat buildup and coil deterioration over time. Coil unraveled and possibly not burnt.

[X_Factor]

coils are coated with an epoxy like glue.....that probably broke down over time and heat and finaly caused part to un ravel and stick in the coil gap..
that's why most local wrapped coils fail...
what kinda sub tho?

[VexXx Dogg]

RF P3 shallow 10".

HU is a Alpine 149BT
Amp is a JL XD700/5

[Brian Steele]

Perhaps it's your amp that's failed and it was passing DC to the subwoofer. That would cook a coil pretty quickly and silently. If I was you, I'd check the output of the amp before connecting it to any other subwoofers.

[VexXx Dogg]

lovely advice. Thanks Brian.

What should I do, pop in a sub test tone, disconnect front and rear channels and check for DC voltage? I have a meter, but not sure how to check.

[kavaninho]

The heat from the car shouldn't affect the sub so adversely to break down the epoxy/glues. Put the amplifier under some tests to see if its outputting DC. This can be done with an average multi meter.

[SR]

Low voltage on that amp will cause it to clip especially on the sub channel. Mids will sound ok but you wont be able to tell if the sub is clipping till its too late

[nervewrecker]

Before you take it out, crank the volume to be sure.
Sometimes it's the back of the former been hitting the motor and bent. Now its just stuck.

[VexXx Dogg]

it's playing like a rubbing coil, so it's intermittently stuck. Eh get that burned smell tho...go figure
i'll check for Dc on the sub out.

side note, I will upgrade to two 8" drivers.
small sealed enc ~0.3 cuft, 200rms ea 4ohm and about 3.5" deep.

thinking a pair of JL audio w1v3's.
any other recommendations? similar or close to that budget and spec

[VexXx Dogg]

@SR, voltage good, but I'll double check. With the diesels, the first sign of low voltage is a slow crank. The XS power I have still healthy

[X_Factor]

it's playing like a rubbing coil, so it's intermittently stuck. Eh get that burned smell tho...go figure
i'll check for Dc on the sub out.

side note, I will upgrade to two 8" drivers.
small sealed enc ~0.3 cuft, 200rms ea 4ohm and about 3.5" deep.

thinking a pair of JL audio w1v3's.
any other recommendations? similar or close to that budget and spec

try and get it tested on another amp, if it still makes noise and u give up on it, scrap it and see exactly what happened with the coil

RE 8 inch sub fs of 23 and xmax 12mm and probably a couple hundred cheaper than the jl
4.5 inches mounting depth though

http://reaudio.com/documents/rex_manual[2011].pdf

[nervewrecker]

Did you take a dmm to the coil to see if it read abnormal?
Or poke the cone with your finger to see if it's coil rub / former distorted / coil unravel?

[Ted_v2]

RE 8s are nice, but i really like the Image dynamics, the ctx i believe? or was it the IDQ?

[VexXx Dogg]

So it may not be the sub after all. Pulled the sub this afternoon. Check resistance, 3.8-3.9 ohms per coil, no mechanical damage, coil not rubbing. I guess I forgot how stiff this sub was.
I played a track and realised the sub is getting a scratchy signal. I'll have to check amp and hu preouts.

Didn't have a test tone to check output voltage

Who can troubleshoot this further for me

[kavaninho]

Anybody with an oscilloscope and DMM. Look at the output from the HU pre-out and output of the amp on the oscilloscope. Use a few sinusoids of varying frequency (30/45/60hz) and look to see if you get a nice smooth trace. This will help you find which equipment introduces the noise.

[TK!]

Who can troubleshoot this further for me

text me reminder to walk with the deck removal tool.

[VexXx Dogg]

Got some test tones
1 khz @ 0db
50 hz @ 0db
digital silence.

According to JL's website, I should be aiming for 24.5 V on the sub out using 3/4 vol
According to ALpine's documentation/the interweb, the sub volume is actually a defeat, not a boost, so will be checking at +15(which would actually be 0db), not level 0.

Point of clarification: To test for DC offset/output on the sub channel:

1. Should I leave speakers loaded on the amp outputs and just check for DC millivolt output, or should I disconnect all load?
2. Should I play digital silence track at 0 volume or 3/4 when reading for dc offset?

[VexXx Dogg]

Thanks to TK for his help today.

Tested sub in a different car and it worked fine.
Checked the sub out on the amp using a different channel, amp is fine.
It appears as though the sub channels on the HU is wonky. Sometimes I'll get zero output, power cycle the HU and it'll come on, but terribly scratchy and distorted.

The plan is to either get the HU repaired, or use it as a deadhead (no processing) with the 4 working channels and utilize the crossovers on the amp. Right now the amp is unfiltered and all xovers are done on the deck.

The good thing is that the XD700/5 amp can handle that situation with ease with the input channel options. (2/4/6 in). I'll probably need to redo the input sens settings on the am since the input voltage will now be reduced.

Who can repair the deck and what do you think would have caused this. This setup was set and forget ages ago, so no variables have changed with recently added equipment or settings.

[X_Factor]

doesnt the term " deadhead" means when you use the deck without its internal amp called POWER IC in alpine?....therefore doesnt really affect processing?

even though the sub channel is stereo,its internally bridged in the amp
have you tried running each sub out rca singly from the deck into a y splitter (1f--2m) to rule out if its just one rca pre out from the deck gone bad but when both are used it causes the issue?
if its one, you could probably rally with with working one only

[nervewrecker]

Time for an 80 prs

[VexXx Dogg]

Time for an 80 prs

Is it really better than the 149bt? I've been spoiled by Alpine's quality.

[nervewrecker]

Truth be told, I can't hear a difference in sound between the two and I doubt you can.
80prs more user friendly and offers more options.

Dual USB, sd card, aux, custom colors for illumination, eq is 16 bands iirc. didn't see anything for xovers wrt the alpine, the pioneer xovers nice with slope, phase and level adjustments. It's a whole different world imo

[X_Factor]

pretty much the 80prs will be about the only replacement option
sucks they dont have a double din option

[kavaninho]

There are some double din pioneers that are almost as capable as the 80prs (network mode and all). It still ain't as versatile as 80prs however, but they work fine.

[X_Factor]

yeah i got one but they hav a very limited eq..50hz to 12k

[TK!]

Pioneer AVH-X2800BS
13-band graphic equalizer with 7 preset EQ curves
high- and low-pass filters
Time alignment
Auto-EQ
US$ 207.00 on amazon