TheOtherSide

Use the old Wayback machine to get the T/S's of the "old" BM's http://web.archive.org/web/20070619065205/...ity.com/BM.html

When these go on sale, I may have to replace the ported BM in my truck with a couple sealed Mags. I am a huge fan of the low end extension and accurate reproduction of everything from electronic to classical. I couldn't fit the old Mag (needed too much depth/box size). These new ones sound so promising.

Nice writeup. Always good to learn new info, I had never even pondered sealed excursion potential.

Hey guys. I have been a Car Audio nut for a while now but it has come time to build a sub for home use, theater not really music. I don't have a ton of room, maybe 6-8 ft^3 or a little more if I push hard for it. Looking to build an enclosure that'll really bring out the low end <20Hz and have an upper cutoff around 60-70 Hz. Been looking at drivers for a while and I think I have decided on a 15" as the optimum size for the room. No windows, 1 door, carpet, etc around 13'x22' so fairly good in room gain. Now I need a driver. Here is what I had in mind, but I will be getting the amp once I've picked a driver(s): SI Mag 15 CSS SDX15 SS RL-p 15 Dayton TIT400C-4 15 Yeah, the last is if I need to go to 2 drivers to get where I want. I was really kinda hoping to go with either the CSS or the RL-p since I have heard great things about them in big enclosures (>250L) and tuning around 15 hz. Help me out and let me know if I am going the wrong direction here. I am thinking a LLT enclosure is in order to achieve the results I am looking for. Thanks.

Sounds good to me. I'm actually about to build a sub for a HT application and was pondering 2 BM's for it. Our setup is almost identical: Denon Source - 3808ci 110" screen Panasonic 1000U projector B&W 600 series front/center/dual rears DVD-to be determined either denon upconvert or HD-DVD

^^^ ditto When I ship a sub, I make a crate for it that encases the motor, basket, and even goes over the top of the cone (with 3/8 plywood) to prevent something like this from happening. Well, then I pad the sh!te out of it with foam, packed paper, and anything else that will protect it from shocks like dropping. But still, that main packaging looks in decent enough shape. Are you sure it wasn't already broken when it got shipped?

And I thought I was a procrastinator...

Whoops, I missed the part about the HX's box. That's barely enough room to let two breathe, much less 3.

Um, one versus three, doesn't take much more than common sense to figure the outcome there. You have two 1500 pound cars, one with a 100HP engine, the other with a 300HP engine. Which one will be faster? That's easy...the one I'm driving. But really, you have 3 times the surface area and about 3 times the displacement. So..3 beats 1. Now it is all dependent on install, power, etc but everything equal, the HX's got it. Now 2 15" Mags will really make it an even battle. Or, should I say give you a big advantage.

To be quite honest, I may have confused myself. As long as the amp is unregulated, and it can handle the increased voltage, the current draw shouldn't change that much. For example, at 14.4V, an amp is making 3600W into a 2 ohm load will draw roughly 250A (lets assume it's 100% efficient to cut out some BS). At 17V, it makes 4000W into the same 2 ohm load. In this case, the current draw is about 236A. Because we are neglecting the changes in efficiency based on the load and voltage, the current is different but you get the idea hopefully. (BTW these are published numbers for an amp...maybe a little incorrect but published nonetheless...http://www.overstock.com/Electronics/Clif-Designs-4000W-Digital-Clas-X-Amplifier/1406009/product.html) I can see slight changes in the current occuring but nothing major...maybe 5 amps. Yes, I know the above numbers don't exactly work out but it gives you an idea. There is a lot more to determining these variables than just pluging and chugging the numbers into an equation. You have to understand heat loss, efficiency, work, electrical bleed off, etc. It's a lot to take into consideration. If you want to really think about it, why then do we use the same fuse for the amplifier at steady voltage (12V from the battery) and when the car is running (typically 14.4 V)? You have to assume the current isn't going to change thus resulting in the use of the one fuse rating. So to correct myself, the current shouldn't change between 12, 14.4, 16 volts as long as the amp is unregulated. The power, however, will.

And to think....you can get a BM 12 for $170 shipped right now. Why wouldn't you?

I wasn't trying to be too confusing but this is all "theoretical" Your basing on 100% efficiency which is not possible, ever. Also, you are basing your math on the WRONG numbers to get 0.06 ohm. The output V, I are not the same as the input. I am not trying to be rude, bashing, or confusing, but read further, I'll explain. Also, if you look at your calculations, 0.06 ohm is pretty good for the input stage of a device. Almost no resistance...that is a good thing. Your interpretation of resistance is a little askew though. Your output voltage is not 12V or 16V as you think. It is based on the load that is presented at the output of the amplifier stage. My #'s are based on input only and are not output dependent. If you are producing a theoretical 1800W at 1 ohm and you know the input voltage, you can assume the current draw. That is, you know the output power, you know the load (resistance), and you want to know the current draw or as you put it "intensity." Looking at it from the output stage, if you want 1800W at 1 ohm, you must set the voltage accordingly...thus the Gain Setting of the amplifier. You can vary the voltage of the amplifiers output, not the current. What does that tell you? The input is steady, if you draw 200A at 12V at full load, you will be outputting say, 47.4A at 47.4V [remember, you want 1800W output at 1 ohm thus P=V^2/R and P=I^2*R] (test the output of an amplifier and tell me if it ever reads 12V...typically, it isn't even close). That does not factor into Ohms law. You are thinking of both the output and input voltages as being identical...they aren't. Plus, the output current is not equal to the input current. There is loss, heat dissipation (efficiency), and other parts of the amp that use power that is not directly correlated to output power. In a situation like this, you must assume the load and power as being constant (non-factors) and the only variables are the input voltage and current. Increase either and the other will also increase as the amplifier produces more power. This is about the easiest way to explain it. If you are even more confused or think I am wrong, message me and I will try to explain it better.

Remember the old formula: P= VI? This means that disregarding load, which is constant, and assuming that you are using the same wattage (lets say 1800W @ 1 ohm) and the voltage is 12V, the current draw is 200A (assuming 75% efficiency, I know it's 86% at 4 ohm, but lets use 75% at 1 ohm). Now multiply that voltage to 16V, the same wattage, you get 150A load (assuming 75% efficiency). So what this means is that if the output is regulated to be 1800W at 1 ohm, then yes, your current draw would go down. But if you are assuming the output wattage will increase proportionally to the voltage, then the new output (at 16V) would be about 77% higher, or roughly 3200W. Using this with the increased voltage, the current draw would increase to about 267A. Hope this helps.

Well, I've been reading stuff over here for the last few months but never got around to getting involved. Well, now that's changed. I am familiar with a few of the folks on here from FSC and found this site to have a lot more info than I could ever use. I wish I had the time to take it all in. Anyways, I am from Atlanta, born raised and I'll die here. Live in the shadow of the world's largest relief carving staring every morning at Davis, Lee, and Jackson. Man, they sure look grey. Hope to enjoy it here and learn a lot from you folks. Ya'll don't hesitate to ask me anything.

I found SSA a few months ago but kinda forgot about it. I needed a place with more information than CA.com and something to complement FSC.com. I found SSA via Fi's website.