Tom 400 CFI

This is going to be long winded, and unfortunately, strewn with subjective, and vague descriptions, but hopefully, I can get some help amidst all my vague "expectations".

I installed a sub system in my "Winter 'Vette" ('92 Dodge Stealth RT/TT) to augment the factory system, which is better than the factory system in my C6...except that it lacked bass badly. I bought a 3/4" piece of plywood and cut it to fit snugly in the back of the car, over the spare tire area. I removed the spare tire, jack, etc and the board I made basically replaces a fiber board that originally covered the spare tire area. The area is approximately 3' x 2.5' x 8". I used 3/4" adheasive weather stripping around the entire perimiter of the board to seal it as best I could to the rear interior plastic.

*Subs used are JL Audio 12IB4, Two of them
*Amp is a Soundstream 500 SX
*Signal to the amp comes from the rear channels of the factory (Mitsubishi) head unit, via a "Directed" brand, Line Output Converter.

That's pretty much the system. First the expectation then the results. Here's where it gets really subjective.

The expectation comes from a Trans Am I had years ago. I did pretty much the same thing; removed the rear storage lid, and replaced it w/a carpeted, 1" plywood board with:
*two JL 12WO4 subs
*powered by a Sounds stream 300SX amp
*Signal was direct from an Alpine 7534s head unit.
Now this system IMO, pounded. When cranked up, it felt like you were going to damage something; either your body, or the car. Friends all agreed that the power and quality of the sound was awesome (so it wasn't just my opinion). If you opened the rear hatch and played the system, lot's of bass was apparent, even from a distance. The system seemed to perform effortlessly too. That's what my expectation for the new system is. Adjectives I'd use to describe the performance of the Trans Am's system are:
POWER
Depth
"3D" sound (yes, the bass sounded/felt 3D)
Effortless

The problem: The current system doesn't sound like the system in the TA...at all. The bass is fairly tight, but not strong at all. This is hard to describe, but it's WAY better than it was before I installed the subs and amp, but it just seems like something is missing....because something must be "wrong". Arguments about my hardware selection and implementation asside, the thing should impress the average person and it won't, currently.

Settings: I have the LOC turned up about 1/2 way, and I have the line level input selector switch on the amp set to "high" or 0-5v. I have the crossover switch set to "low pass" and the speakers are sired in parallel, for 2 phm load. I have the gain on the amp turned all the way up, as high as it will go, and the crossover turned all the way down to "45" (hz?). If I raise the crossover at all, the midbass get overwhelming real quick, and it's annoying sounding. Overall, adjectives I'd use to describe the performance are:
Weak
Colored sound
unimpressive
strained
Not DEEP/no depth

How do you know what voltage is coming from the LOC based on the settings of the pots?
Are the 12IB4's comparable to the 12WO4's?
How do I know what to set the input voltage at on the amp?
Power from a 500sx should KILL. Why do I have to have the gain cranked, just to get bass that is notably better than stock?
How would I know if something is out of phase (either the LOC wires or speaker wires)? -I know the speakers wires aren't out of phase, BTW.
Something is out of whack. Any input please?

87 formy

I think the problem is your box, if you can call a sheet of plywood a box that is. The subs really need to be in a box, so that the sub is completely sealed off from the rest of the car; also the box needs to be the right size for the subs to perform at their best. They are normally made of MDF board or fiberglass.

I don't know what the voltage is from your line output, check the manual or something, they vary. Then set the input on your amp to match it.

Your gains shouldn't be all the way up, turn them down.

Tom 400 CFI

I didn't use a box in my Trans Am. Or my Camaro after that. Just a board, and it ripped, as described above. Both the JL speakers I used in my TA and the JL 12IB4 subs I'm now using are infinite Baffle subs; they're meant to be used in a baffle board situation, which is what I had in my TA/Camaro, and what I'm using here. The difference in sound between my TA and the Stealth is not a small one; it's HUGE. It's more than just an "improper box".

That's the problem; the "Directed" brand LOC I bought came with no directions, other than which wire to hook up where, and HOW to adjust the gain (physically). No indicator of how much turning the pot would equal what voltage.

I know, but if I turn it down at all, there just isn't nearly enough sound/bass. Then it's down right pathetic.

The more I think about this whole thing, the more I think something is out of phase.

87 formy

Well, I can't say I've ever tried a sub without a box, but from what I've heard, if it isn't completely sealed off from the cabin, the waves from the speaker will cancel each other out and sound like crap.

As for something being out of phase, as long as your subs are in phase together you should be getting decent bass (assuming that everything was working well that is), you could try switching the positive and negative speaker wire on one of the subs and see if it sounds better/worse.

cdoyle

Your subs have specs for they type of enclosure they are suited for, if they aren't designed for a baffle environment they are not going to sound right, and could damage the speakers too.

kanmudhog

iTrader: (4)

Use an ohm meter to confirm you have 2 ohms across the voice coil , I know an enclosure is important but I would think with that much power it would still be loud even if it sounded like crap .

Tom 400 CFI

Exactly!! SOMEONE "gets it". I'll check the ohms tonight.

No one knows how to check or know the voltage coming from the Line Output converter?

-Tom

lukn4trbl

Some q's and observations:

- Are you able to post a diagram of how you wired the speakers to the
amp?

You may have the speakers out of phase with each other and the pressure
waves may be cancelling out, instead of adding.

In addition, you may not have a correct 2 ohm setup. An ohm meter will
not give you a correct reading as it's a DC current, whereas the speaker
impedence is measured at 1Khz using a sine wave.

You say you have the signal coming from the rear channel of the head unit
going into a low level converter.

What is the output of the converter? Is it line level RCA/coax output, or low
voltage copper wire signal?

From what I understand you have the voltage set incorrectly on the input
of the amplifier. If the converter is reducing the signal level, you want to
have "line level" input selected ~ 250 mV.

Please clarify this setup. Pictures, or wired diagrams will help.

45 Hz is a very low cut off. The lower the frequency cut off, the more power
you'll need to 'hear' the bass, or feel it. Back in College, our physics teacher
did an experiment with about 30 of us. Our lower listening level dropped off
at about 35 Hz on average. That means the sub is producing about 10 Hz of
audio that the average human can detect (minus harmonics).

What is the model number of the LOC?

Based on the inputs used, and the voltage level into the amplifier.
Can't say without more info abuot the converter.

Sub woofers are out of phase, or not wired for proper load to the amplifier.
If you have access to a pulse generator, you can feed about 1-5 Hz into
the speakers and watch the cones move. If they are both pushing at the
same time, they are wired properly.

You can also tell quite easily by the +/- tags on the speaker terminals if you
can view them.

If it's a parallel connection, you want the positive leads coupled , and the
negative leads coupled.

If it's a series connection, you'll want positive connected to negative to be
in phase.

Tom 400 CFI

Thanks for replying.

I don't know how to draw a diagram and post it on here, but I've got a good quality speaker wire, w/clear insulation, with "+" signs stamped on on side (wire) of it. So, starting at the AMP, I connected that speaker wire to the amp w/the "+" wire into the Right "+" recepticle, and the negative wire (not labeled) in the Left channel negative as the diagram on the amp instructs for Bridged mode operation.

On the other end of that same wire, I've got the wire w/the "+" stamped on it, attached to the terminal on the speaker labeled "+" and painted red. The other wire goes to the terminal labeled "-".

Each speaker has four terminals on it; two "+"'s and two "-"'s. I hooked more of the same type of wire "+" to the "+" term on the speaker, and unlabeled to the "-" term on the speaker. I ran that to the next speaker, and connected the same way; Wire w/the "+" to the red term marked "+" and non marked wire to the "-" terminal. I know that this part is right, but I may be out of phase at the LOC to head connections.

Copy. Good to know.


I don't know what the output of the converter is. It DOES convert from speaker level to an RCA out put, but I have no idea what setting of the pots, equal what voltage. There were literally NO directions w/the thing, other than which wire to hook where on the head unit, and then, "Adjust gains to suit you desire".

Interesting to know about the input setting. That makes a huge difference, I just thought I might damage the amp if the signal coming from the LOC was too high a voltage, and I had it set on "low".

I agree. IIRC, in my Trans Am w/a similar set up (described above in my first post), I thing I set the crossover at around 65 Hz, and it sounded great. If I go that high w/this set up, there is just WAY too much midbass. Too much drone and not enough "thump".


It is a Directed Electronics 55020. You can see a pic here:
http://caraudiosecurity.com/shop/pro...s_id/3794.html



Yeah, I don't have a pulse generator. I think you can tell from my description above that I do know how to wire them.

lukn4trbl

Alright, I just searched all of your components and I have more questions
( I think we're onto something):

1. Are your subs in any sort of box, enclosure? If so, what is the volume of
the box in cubic feet?

2. My search turns up JL Audio 12IB4 speakers as 8 ohm, single coil, free air
design. You say there are four terminals on the speakers, correct?
Are you able to take a picture of the terminals? I'm not able to find a photo
on the 'Net because these speakers are discontinued.

3. The LOC has a sensitivity adjust. Has this been set to the proper level?

4. Your amplifier has a 0.2 to 2.0V Input level setting. This is were the
selector switch should be positioned. Before you turn on the stereo to
set the levels, make sure the head unit volume is low. Also turn the
input senstivity down on the amplifier.

Now turn on the head unit , and set the level to about 75%. Then
begin to adjust the input level on the amplifier as much as you can
until the overload LED's light up (or it starts to distort). Once either
condition occurs, back of the input level slightly.

Here is a link to the manual

http://www.soundstream.com/manuals/A...s/r5_7_10s.pdf

5. The Balance switches must be set to "UNBAL" (unbalanced).

6. I'm still a little confused on how you have the speakers wired (4 terminals)?
It almost seems as though you have dual voice coils from the description.

This is very important to figure out as it will dictate how the speakers
are wired for impedence to match the amplifier.

There is a diagram on page 1 of the manual which shows correct parallel
wiring for two 4 ohm speakers (single voice coil).

Once we determine what you have (JL 12IB4?), then we can lay down
the correct wiring.

Tom 400 CFI

Fisrt off, lukn4trbl, I want to say THANK YOU for taking the time to think about/ask/and post to help me out. I feel like you know your stuff, and that I'm getting somewhere here. Answers and pic below...

Yes. The dimensions are ROUGHLY 50" x 27" x 5". I say roughly because it isn't symetrically shaped, and the floor isn't totally flat. Additionally, even though it's well sealed against the interior plastic trim, the plastic trim itself isn't sealed to anything else (floor pan, rear wall, etc -just like in an F-body)...so that would allow some leakage. I don't know how that affects the "real volume" of the space though... There is a chunk "missing" from the area that is an Isosceles, 90* triangle; 11" x 11" -or 60.5" sq. Knowing this, I calculate the volume as such:
50 x 27 = 1350" sq
1350 - 60 = 1290" sq
1290 x 5 = 6450" Cubed
6450/1728= 3.73 cubic feet, or 1.87 cubic feet per sub. Roughly.








I THOUGHT that they were 4 ohms, due to the 12IB4. But the rest of the info is correct. I got the "IB" because I was using a Baffleboard, and thoguht that since it's not REALLY totally sealed, that was the correct thing to do. Here is a pretty good shot of how I have them hooked up at the moment. PLEASE NOTE! I don't have spade connectors on the wires yet, because it's still in "construction". You can also see the speaker wiring in the pics above, wthe board lifted...


Second speaker


I don't know what the proper level is, as the directions said nothing more than "set to desired level" -or something to that effect. I have them set at about 70% or so on their dials/pots.


Here is how everything was set BEFORE I started making adjustments last night:





Based on your suggestion above, I made the change last night (from "High" to "Low" input sensativity). That made a HUGE difference, allowing me to lower my input sensativity to about 1/2 and still have the same (or more) volume.

Done. I also turned UP the cross over point from 45Hz previously, to 65Hz on the dial. This also made a huge improvement. MUCH more volume, and a very minimal increas in boominess. If you go above 80Hz though, boominess gets ridiculous.

They are.

See pics above... They aren't dual voice coils...they just have four TABS (two for pos, two for neg) on each speaker. Probably for doing exactly what I'm doing; wiring in parallel.

I'm sure that they are 12IB4's, That's what the box says. I'll have to double check the back of the speaker when the car gets back (GF has it at the moment).

Again, the adjust ments made last night:
*Swithing input level switch
*Changing cross point
*changing input sensetivity
...all made a very noticable difference, both in volume and in quality. Still it doesn't compare w/the system in my Trans Am...yet. Thank you again for taking the time to read, and think about my situation. I really appreciate it.

P.S. As a "Winter beater", I need as much usable space in the rear as possible. That's why I pursued the "baffle board" in the first place; it didn't sacrifice ANY hatch area volume at all...other than where the spare tire used to be. I can still throw skis boots, poles, gear, etc in the back no problem, and not have to worry about moving/removing a sub box all the time.


-Tom

lukn4trbl

Thanks for the pics Tom, those really help.

Your speakers are actually two terminals with dual spade connectors. This
is simply used for ease of connecting multiple speakers in a circuit. So
we've confirmed they are single voice coil, now just double check the back
of the speaker. Everything I found on the 'Net shows 8 ohms for your IB4's.

Part of the reason for the nasty bass tones is because those speakers need
much more volume behind them to perform well. They are not meant for
enclosures that small. You might want to pad the trunk/spare tire area
with some sort of foam, or fabric to absorb the overtones. Those speakers
are pounding into metal and getting large amounts of reflections. You will
notice the bass will get smoother and 'warmer' if you install something over
the metal.

The speaker wiring looks correct from the photo. The amp should see a
4 ohm load if the speakers are 8 ohms each. Perfect.

Another huge reason for loss of sound quality is the LOC. It's a cheap one,
and produces a bad signal. Converters in general are a bad idea for sound
quality.

In essence, the signal from the music source is getting picked up and
amplified by a pre-amp. It then goes to a really poor amplifier circuit
in the head unit to boost the signal to listening levels.

Then...you take that amplified signal and attenuate it with the LOC back
to pre-amp levels. Another source for distortion.

Lastly, the amp takes that low level signal and amplifies it once again to
listening levels (but much higher gain).

I bet your last stereo had line level RCA outputs from the head unit directly
to the amp. So it would be:

Music source > pre-amp > amplifier > speakers

as opposed to:

Music source > pre-amp > low gain amplifier > LOC > pre-amp levels > amplifier > speakers

My last suggestion will be the cross over settings. That amplifier seems to
have a "Band Stop' filter , and should be used for mid tones, not bass tones.

A bass sub-woofer amplifier will have what's call a "Low pass" filter with
one cut-off frequency.

I'll read up the manual again and let you know what I find.

At least you're improving the setup!

lukn4trbl

OK, your amp has a selector switch for High Pass, Full Range, and Low Pass.

You want to make sure this switch is set to Low Pass (which looks correct in the photo).

Tom 400 CFI

Yep, You're right; they're 8 Ohm. I thought they were 4 when I bought them, but you're right, 4 ohm total for the two is fine.

The idea of using speaker foam is an awesome suggestion! I can't believe that I didn't think of that, and no one else suggested that either! I'm definitely going to give that a try -for starters. Ultimately though, it sounds like I need different woofers. Do you have any suggestions for what I've got going on? (~2 cu ft/sub)

You're right that the system I'm comparing this one to (the one in my Trans Am, DID in fact use RCA outs for 4 channels. And I know that is better method for sure. I knew I was going to lose SOME sound quality using an LOC, but I didn't think that it would be "huge", as you put it. That's good to know. Ultimately, I'd like to replace the factory head unit, and usse proper RCA-outs, but frankly, I can't stand what is available these days, so I'm waiting for a change in trends, I guess.

You are correct. The photo of the bottom of the amp was to show that the switch is (and has been) set to "Low Pass". The pic isn't very clear though, due to the reflection.

You're right, it IS getting better. I can't wait to try something soft under the board.

lukn4trbl

I've been so far removed from the audio business since College, I'm
probably not the best to ask about current trends.

Anything name brand is going to be decent. Anything other than "free air"
will sound better as well.

Let me know if the padding sounds any better.

Tom 400 CFI

Well, I finally got around to adding stuffing. I chopped up two pillows I had and put all the stuffing from them into the "enclosure".

I DID take some of the edge off the "boominess", but didn't change anything else about the sound, to my ear. So, it IS a bit better.

Current Verdict: It sounds pretty good now. Much better than when I started this thread, but still at least equally far from where I think it OUGHT to be. At this point, I'm pretty convinced that I need different sub woofers, and I just need to do a little leg work to find out which ones will work in a ~2' cube enclosure.

I want to thank lukn4trbl again for the thoughtful responses, and taking the time to offer real, useful advice. Thanks!

-Tom

lukn4trbl

Thanks for the update Tom. Good to see it's working out for you.

terrorhertz

Tom,
I wrote a rather lenthing post last week for you but somewhere in time I got logged out(probably
Anti-Spam related) and it got lost. I have a forum for supporting a charity for the soldiers
and I made some changes that allowed me to stop the time limits. maybey I can help the admin here if they want.
Luk gave some really good advice on your system. I modeled the subs you have and they need
REALLY big boxes. Infinite baffle speakers mean infinitely LARGE inclosures. such as useing your
whole trunk as a box. not an infinitely small box such as a kickpanel or tirewell.
You could put a sealed square of 2x4s, 2x6s or 2x8s under the baffle board to raise it and in
crease the internal volume behind the subs. It is cheaper than new subs but it is still
now where near the internal volume that you will need but it is a cheap fix.
New subs is better but remember that if you get 2 subs then the total volume for both has
to be within your spec. If a single sub needs 2 cubic feet then 2 of the same subs will need 4 cubis feet.
I don't want to waste more time on the subs since LUK seems to have that under control.
What I want to help with is your gain settings. You asked early in the thread what voltage
they should be set at. You also asked how to measure it.
I use 3 methods to measure output voltage of a device. the 1st uses an ac meter and
this method is only accurate if the device isn't driven into clipping. And you can't tell
with an ac meter if it is clipping. The 2nd uses an osciliscope and is the most accurate
and the most expensive($200+). the 3rd uses a $13 mini amp available at Radio Shack and a
test CD($17). That is my perferred and most used method.

1st I want to explain what the gain adjustments are and how they are used then I'll get to how to
set them. Understanding this concept is important in actually doing it. The gains are used
to match the output of one device to the input of the next device that it is connected to.
not all devices can handle the same input/output voltages. There is no standard here like
in the voltages that computer equipment use. So different manufactures make devices that
handle different voltages while takeing care that their own equipment works well with
their other devices but they don't optimize them for other companies devices. So they put
gains on so that they can be matched to other devices.
A gain is nothing more than a potentiometer like a volume control. It raises or lowers the
voltage. Lets say that a device outputs 4 volts into a component that can only handle 2V
input. Then the 2nd component will be overdriven if it doesn't have a gain adjustment to
cut down the input voltage. When overdriven the device will produce more distortion because of
of it. It drives the 2nd device into clipping at a low volume level. Clipping happens when a
device trys to produce a voltage level that it can't, and it cuts off some of the signal.
This causes distortion of the signal because the output is not the same as the input.
In an ideal system the input signal will be the same as the output
(in shape...Voltage difference doesn't matter) anything different is measured as distortion.
OK summer class is over. You asked how to measure the voltage output.
I've said this time and again in other forums: the actual voltage doesn't matter as much
as the maximum UNDISTORTED voltage when setting gains on your system. That is if sound
quality is the concern and maximum udistorted volume is a concern.
I've already explained that an ac meter even a true ac meter will not work in this situation.
The best way is to use an osciliscope but it is expensive unless you do this a lot. With
the o-scope you use a 1:1 transformer between the scope probes and the RCA jacks with a
test CD made for these settings. then you watch the waveform while you raise the volume or
gain setting until you see the sinewave begin to flatten out on the top/bottom of the arc.
then you turn the volume/gain back until there isn't any flats on it.
The cheapest way to do this is with the Radio Shack Mini-amp and a test cd and I
recommend headphones.
Price list:
RS mini-amp: http://www.radioshack.com/product/in...entPage=search
The test cd: http://www.davidnavone.com/cart.asp?14&pid=118
Get headphones and rca y adaptors and rca to 1/8 mono phono adaptors at Radio Shack.
Also while at Radio shack pick up a 10Kohm and a 1Kohm resisters 1/4 watt or 1/2 watt.
they come in packs of 5. The resistors are for setting the amp gains.

Turn all gains down and disconnect your speakers from the amp output.
Attach the RCA y-adapter to the output of your LOC. connect 1 end of
the y-adapter to the rca going to the amp and the other to the RCA-1/8 mono phono jack
to the mini amp. set the mini amp to a low volume( you don't want the volume level
of the mini-amp to be so high as to distort the signal). Put CD 101 in on track #1 and listen
to it. It will gain in volume until it distorts so that you can hear what distortion sounds
like then it backs off and holds that constant signal. while it is holding the constant
signal you raise the gains till you hear that distortion again then turn it down till you
don't. Set the other channel of the LOC the same way. Your LOC is now set to the max.
undistorted output.
I don't remember you mentioning a sound processor such as an eq or x-over.
You set them in the same way. I'll explain more on this if anyone asks. I
understand that the signal then runs to an amp from the LOC. The amp also has a x-over.
Set the x-over to full pass for this test. We are useing a 1kHz signal so full pass is
manditory for now so that it doesn't filter the signal. when done set the x-over back to
the setting you prefer. I suggest higher than 45Hz. Luk mentioned this also. there is
very little musical content below 45 Hz.
Now the amps putting out way too much power to be fed into the mini-amp. so we have to reduce
it. That is why I said to buy the 1Kohm and the 10Kohm resisters. We will use them as a
voltage divider to cut down the power going into the mini-amp from the amp's output. These
resistors will work on amps up to 1000Watts.
twist 1 end of each resistor together. connect the other end of the 10Kohm resister to the
amp +. connect the other end of the 1Kohm resister to the amp -. then connect the probes
from the mini-amp to the middle where the 2 resisters are twaisted together and the other
probe to the amp-. then play the cd and wait then turn up the gain until you hear the
distortion again. then back it off and leave it. Remove the resistors and the min-amp
then reconnect the speakers and set the amp x-over back to the x-over setting that your
perfered and give the system a try with your favorite music. All
components will be set to the max undistorted voltage. The head unit may add distortion
at this point since most aftermarket head units have distorion at max. volume.With most
aftermarkeet head units I suggest not going full volume because of this but it is great
when haveing friends in the car as long as they don't know what distortion is.
When if you change subs you shouldn't have to go back through this. These are electrical
settings and not accoustical settings. Use your volume/bass/treble/eq settings to tame any
distortion from there. I also want to add that EQs and bass/treble can NEVER compensate for
acoustic anomolities.
I also have speaker box modeling software. Some I wrote and some I bought. I can model
any sub in the box volume that you have. If this forum allows me to post pics then I may be
able to help with your choice of subs. But it is just as easy to go by the manufacturer's
recommend volumes. but please note that speakers other than infinite baffle are seal box
or ported box speakers. If you don't won't to have to add a port(s) to your box then you
want sealed box speakers. you only want infinite baffle in large spaces.
Also If you cant find speakers that fit that size then you can combine speakers in a
compisite configuration and put 2 subs in the space of half of one sub. just a thought.

terrorhertz