I have a little less space for the column this month, so I'll skip my comments and go straight to the questions. In the meantime, have a Merry Christmas!
Q:Hi! First, I would like to thank you for your awesome mag! I always enjoy reading Car Audio and Electronics! I'm having trouble with one of my Orion 6.2 XTR woofers. It doesn't play the bass. I can clearly hear the higher tones, but there's no travel at all on the speaker's cone: When I try pushing gently on the cone, nothing moves. It gives me the feeling that the coil is, in some way, stuck on the magnet at its lower position. I tried to search on the Internet for a solution to this problem, but I can't find any! Do you have an idea what could be the causes of my problem and how to fix it?Thanks a lot!Nicolas Girard
A There is a group of recurring problems that can affect loudspeakers, and it sounds like you have run into one often referred to as "frozen cone." The speaker seems to be locked in place either in the rest position or at some point towards either end of its travel. You can perform a couple of tests to see the source of the problem. If it smells burnt near the center of the speaker, you likely have toasted the voice coil. In the event that you get it hot enough for long enough, the varnish on the wire melts and finally swells until the voice coil is glued into place.
Another test is to look at the magnet structure on the back of the speaker. The magnet is a dark gray color, and if you look very closely at it, you may notice what looks like a very fine pencil line around the magnet's circumference. Scratch at the line with your fingernail and you will notice that it doesn't scrape off, but rather you feel a crack in the magnet. In this case, the voice coil has probably bottomed out, hitting the speaker's back plate and fracturing the fragile magnet. Half of the magnet shifts sideways, causing it to pinch the voice coil in the magnetic gap.
I have found you can take the cracked speaker and bump it with your hand on the high side, and it will re-center itself, allowing the speaker cone to move freely again. Unfortunately, this is not a fix - you still have a damaged speaker. And now for the bad news: In either case, the problem is caused by usage or unplanned damage, which is not generally covered under warranty.
Q Let me start by saying that I love the mag and that I hold you fully responsible for the thousands of dollars that I have happily spent on car audio products over the years! Now that the blame rests solely on you, I would like to ask for some help. I own a daily driven, two-door, 1996 GMC Jimmy. I am experiencing a problem with the temporary system I threw in to get me by until the truck is done. The system starts with a Pioneer Premier head unit. I have a new Stinger Expert Level battery terminal with built-in voltage display, new 4-gauge power and ground wire (150-amp fuse approximately 15" from the battery) and Stinger power wire going approximately 14' to a new Stinger 1.0-farad capacitor with a digital voltage display top that I removed from a new Power Acoustik 1.2-farad 24-volt DC Competition CK Series cap (that I gave a little body damage to). That goes 16" to a Logic 640-watt 2-channel amp. The ground wires for the amp and cap are each 3' long. This powers two 1st generation Alpine DVC S12's through 14-gauge, (I know, I know, 12-gauge would be better) Stinger speaker wire in a box with each speaker in a sealed, separate 1ft3 space. All connections are Stinger PRO.
The issue is with the cap, (I think). The battery displays between 14.25 and 14.96 volts with the truck running at idle. At the time of install, I charged the cap until the bulb went completely out. That left me with 14.0 volts at the cap and 14.25 at the battery. The goal (to my understanding) when installing a cap is to match its voltage to that of the battery. I saw the difference, but figured it was small enough to leave alone. I test drove the car at night with the system 3/4 of the way loud. I idled for 10 minutes, hit the road and simulated some city driving for another 10, and then hit the highway for a drive, which lasted about 30 minutes. When I returned, I noticed that the cap display was at 13.8 volts and the battery display was at 14.54 with the truck running, lights on and volume turned down. When I shut the truck off, the battery went back to 14.25 and the cap went down to 12.8. It was one o'clock in the morning, so I left it alone and went to sleep.
The next morning I started the truck. The battery was at 14.86 and the cap displayed 14.0 with the volume turned down. With the volume turned 3/4 of the way up, the voltage on the cap would go down to 13.8 on the bass hit and back up to 14.0 with no bass hitting. I guess my question(s) would be of a little ignorance. Why is there a variation? Is this normal? Is this harming anything? Does this fluctuation affect my bass quality? Do I need to discharge the cap and charge it again? I have a fixation on doing things right and would really like to get the cap to the same or at least near the same voltage of the battery. Any help would further reinforce the belief that you guys are the car audio GODS.Thank you in advance,Stelios Diacakis
A: We'll gladly take the blame for your addiction! I think the only problem you have is with what you believe rather than what your system is doing. You are not indicating any noticeable problem, so I would bet that if you hadn't seen a voltage reading, you would be a happy guy. So let's look at the readings and see how relevant they are.
Charging a cap serves only one purpose - it prevents the connector from arc welding itself to your terminal when you first connect the cap. By getting the capacitor's voltage reasonably close to the battery voltage, you limit the voltage difference to a small amount that leads to a little spark rather than a giant, searing flash when you make the connection. Other than that, there is no issue with pre-charging, so don't bother to re-charge it unless it is disconnected from the system long enough to drain off its charge.
I am not a fan of trusting a reading that comes from anything other than a piece of real professional-grade test equipment, so you can place a large error factor on any reading you see. One reason for my skepticism is that when you turned the vehicle off, the voltage at the cap was 12.8 volts and the voltage at the battery was 14.25 volts. This can't happen: The cap voltage was pretty well on the mark for a static battery level fresh after charging, but the actual battery was reading a voltage that can only occur while the alternator is operating. Occasionally a battery isolator will prevent a leveling of the voltage, but the difference is too wide.
Although I don't know what wire gauge you are using for your main power feed, the initial readings you report are pretty typical. A quarter volt loss between the front of the car and the trunk is reasonable. With a larger gauge power wire, you might see less loss, but the difference would not be a big deal. The next morning, the voltage differential was less than a volt, which seems a bit high, but not by the stories your readouts were telling.
Overall, a variation in voltage is normal and would not harm any piece of quality aftermarket gear. It would also have next to no effect on your bass performance, since you do have a capacitor to compensate for the slow response time of the battery. Without some computerized test and analysis equipment like we use here at the school, you will not be able to determine the response characteristics of the amplifier's internal power supply - if anything is going to choke your bass, it will be either your power distribution or the amplifier's internal characteristics.
I am a bit worried about your Power Acoustik 1.2-farad 24-volt DC Competition CK Series capacitor. If you have dented the can, there is a good possibility that it will short out internally. I can only hope your fusing system is correct!
Q: Hi, I've got a small problem. I'm not sure if you can help me out, but I can't get hold of Orion, so you're my best bet. I've got a 10" DVC Orion XTR subwoofer that is a few years old and I need to build a box for it. Unfortunately I don't have a clue what size of box I need or if it should be sealed or ported. I was wondering if you had any knowledge about this sub and could help me out a bit. I've tried box-building programs and they all give me different sizes. Any help you can give me is greatly appreciated.Thanks,Brad Ness
A:According to my friend Mark, who is a former Orion tech rep, the XTR series was manufactured over several years and kept the same model designation, so I can't tell which series you actually have. He recommends a sealed cabinet of about 1ft3 in volume for the older models with the foam surrounds, and if it has the rubber surround, a sealed cabinet of about 1.2ft3 is an option. On the newer drivers, ported cabinets are an option. He has had success with a 1.2ft3 to 1.3ft3 cabinet using a 3" port, between 8" to 9 1/2" long.
It is not usual that the sealed and ported volumes are similar - normally a ported cabinet is larger than a sealed version. That makes this situation unique. You can start with a sealed cabinet and check out the sound. Then you can cut a hole, install the port and see what changes occur. If you don't like it, solidly block the hole and you are back to sealed. This almost never works if the volumes are different, so you can have some fun doing a bit of experimentation.