BKOLFO4

Man this is cool. I just talked to Chad for about 4-5 minutes yesterday. Going to be some good stuff coming our way I guess I'll be waiting before I make any changes to the suburban. . . . Brian

An easy explaination: Impedance rise is due to the fact that the input to the subwoofer coil is AC, and the subwoofer coil has a resistance and reactance (it is a coil). The speaker's impedance varies with frequency even in free-air with a peak at Fs. Put the speaker in a box, and you now have the Fs of the driver, the Fb of the box (impedance hump on each side of Fb) and the change in the driver reaction to input power due to the enclosure. All these contribute to the actual impedance the amp will see at a given frequency. An easy fairly acurate way to measure "impedance" is to wire a high power resistor in series with the driver. Input enough power to get some air flowing in the enclosure, and measure voltage output of the amp and across the resistor for single frequency tones. With these voltages you can find: Current = Votlage across the resistor / the value of the resistor Voltage across the driver = votlage at the amp's terminals - voltage across the resistor driver impedance = voltage across the driver / current This is a fairly accurate way to measure the impedance. You can get a better measurement if you have a variable resistor that can handle high power: For each frequency, measure the voltage at the amp's output and across the fixed resistor that is in series with the driver. Replace the driver with the variable resistor. Adjust the variable resistor until the voltage across the fixed resistor is the same as it was while the driver was connected (keep the same voltage on the amp's output). Once the variable resistor is set correctly, remove it from the circuit and measure the resistance. That is a close estimate of the impedance the amp sees when the driver is connected. These measurements are also handy for finding your true box tuning. If you plot the impedance vs. frequency, you will see two humps in the impedance with what should be near your lowest impedance between them. That low is the port tuning frequency. Brian

car: 2000 Chevy Suburban Electrical: 260 EA Alt, (9) yellow top optimas Amps: (8) US Amps MD3Ds Subs: (2) RE MT 18's w/ dual 1 ohm coils Box: 14 ft^3 tuned to 40 Hz Mic: New TL Tone: 42 or 43 Hz Score: (legal or outlaw) 156.9 Outlaw 155.3 playing music.

That makes no sense. You run your amps in pairs per one ohm coil, or in lamens terms .5 ohms per amp, than in the next sentence you say your impedance dips to 2.2 ohms per coil? Are you saying that each amp is running .5 ohms or 1.1 ohms? When you put a sub in an enclosure, you get an impedance rise. . . .in my case, the actual lowest impedance of each coil with the sub in the enclosure and power running through it is 2.2 ohms. So, while most people woudl look at my setup and think I am running each amp at .5 ohms, I am actually running each amp at 1.1 ohms. Brian

I run my amps in pairs strapped to 1 ohm coils without any problems. But, I have also tested my impedance, and it actually only dips to 2.2 ohms per coil with the system in the enclosure. If I change subs again, I am going to drop down to .7 ohms on each strapped pair and see what happens. Brian

Where are you guys in Texas??? I would love to hear a set of BTL's. If you need any install help, let me know. I am in Denton, just north of Dallas. Brian

Would (9) Optima D31T's and a 260 amp alternator be acceptable for (8) AX3200DE's? Brian

Greg told me they do not like .5 ohms (actual load). But with a .5 load (like a dual 1 ohm sub), they are ok with impedance rise. So just plan on rolling the volume vs. burping them if you are going to run them that low. Brian

We are now running the (8) MD3's. Nice amps. They were packaged poorly, so three were damaged during shipping. One of them overheats quickly, but I am guessing it was due to the shipping damage. We finally measured our actual impedance rise with the subs in the enclosure, and each amp is seeing 2.4 ohms. We still managed to pull a 155.8 @ 48 Hz with (2) 18's walled behind the C-Pillar in a suburban. We hope to have the subs reconed as dual 1's soon (they are dual 2's right now) and get some more power out of the amps! I have to say thanks to Greg for always being willing to talk on the phone and help out. . . . Brian

:D :D

We are a Texas dealer. Hardcore Customs 2700 K Ave Suite 100 Plano, Texas 75074 (469) 467-7400 The shop does professional installation, custom interior work (over $13k invested in interior tools and equipment and two VERY good interior specialists), and has a full paint and body shop. If you are in North Texas, come on by.

If you really need that much power, and it has to be strapped (you can't accomplish the same result with a pair of MD2's running stand alone), just get a pair of MD3's. . . .They are not that much more $$$ and they will be available soon! Brian

We were told as a dealer no internet sales. Also told there are no authorized internet sellers. Maybe they sell on the internet as long as they sell for full retail price. . .like RE direct is now. Would be interesting to call and see if they will sell below the price they have advertised on the website. Brian

Trying to skip the 150's and go straight for 160+ on the TL. Looks like that is what you need for TBP for high SPL now days. . .

That's me. . .I'll be out at TBP sometime next month with the new setup. . . Just out surfing when I ran into the "official" US Amps forum. Brian

Denton, TX Suburban, (4) AA Avalanche 15's ring a bell?

Just joined to check out the official US Amps forum. Found the site throgh the CarAudio forum. Starting a new install shortly and have on order (8) Merlin MD3's. Once the install is going, I'll post up some pictures. . . Brian