amp/audio theory and other Q's

[fatass92]

I heard that if you excessivly underpower a sub, it loses all its sensitivity and sound quality, is this true? My reason is that I have an earthquake 12" magma sub (600W RMS 1200W max) and I am running it mono at 1.5ohms on an RF 150aII that is rated at like 200w mono @ 4 ohms. I was wondering what kind of difference a new amp would make, and if anyone had any amp suggestions or recomendations. My other question is in the setup. I plan to get a set of Focal 165k's (6.5 components) and a pair of MB quart DTC 169's for the rear. they are all going to be amped, my question is is it possible to set up the speakers so that the sub only puts out frequencies of about 60Hz or less. I know it is possible, but is it plausible? basically I just want bass that you feel, not the kind you hear, along with very good sound quality.

Thanks

-JOHN

[hdswanny]

i'm not familiar with ANY rf items so i'm not sure what your amp is capable of, but i do know that the (1)magmas can take well over 1000w(rms). Although earthquake states that for optimal results you should use 700wrms. also these things are notorious for their low bass. as for not wanting to hear bass just feel it, bass is suppose to be inaudible to the human ear at 20hz. and at 60hz you will definitely FEEL and HEAR it if powered right. to set the your frquencies you would have to use your x-over. i've heard GREAT things bout ur focal set, you could TRY and set the x-over for the midbass at 60hz if it can handle it. but check your specs on the focals and see what they recommend as far as the x-over point.

sounds like a good set up. r the focals in kicks? if they are you might not want any rearfill. but its up to ur ears.
btw my set up will be 3magmas and a D2 with M561s in kicks :)
sorry for the book

[Redsand187]

Well under powering a sub does reduce Sensitivity and Sound Quality, but that is like when you give a sub with a RMS of 1000watts like 100watts. Your sound quality is boosted however when running RMS power to a sub. As far as you other question I would like to first start out saying, 6x9's are trash! garbage, CACA. Stay away from 6x9 and all other unround speakers. I would go with a three way focal compenent system instead, those things sound amazing. I would then put your 7" or 8" speakers in the doors, with a custom lower door panel, and then put the 4" speaker in the dash,(I know it is hard but believe me it sounds so good. Then put the tweeters we ever work best for you. (IE experement) I would then use at least 2 amps(4 would be ideal) One for your compenents, and one for the sub. Or one 50x2 for tweets, 1 75x2/or 100x2 for the 4's and one 150x2 for the 7/8's or get a 5/600 watt amp to power the whole compenent system. Tri-amping would be ideal for sound adjustiblity. I would then get a 500-800 watt amp for the sub. As for crossing over at 60 hertz, it can be done, I would rather have 80 hertz but it's your stereo. To do it, I would adjust your sub amp's crossover to 60 Hz low pass, then I would adjust your front amp to 61hz High Pass. and then use the crossover provided with the compenent system to run the 4's at about 300hz and the tweets at about 1000hz. If you use 4 amps then your sound with be a lot clearer and the speakers will be right on how you adjust them ie: for the tweeters you crossover the amp as high as possible like probably 300 hertz highpass. Then for the 4's also crossover at 300hertz or as close as possible high pass, on the amp. And the midbass 7-8 at 61 hertz, then when the singal goes through the crossover a lot of the sound that needs to be blocked out already is, so the corssover, cleans it up even more. So instead of having a 32dB crossover you get 32dBcrossover plus, 12,18,or 24 even depending on the amp which means 56dB crossover, damn that is near perfect, the best sytems have thousands of dallors in crossovers and they get 64 to 72dB crossovers, and these guys are into their systems with 5 to 6 figures, and are the worlds best. Now wouldn't it be nice to listen to near perfect sound daily on your commute :) One thing is for the best sound quality I would suggest getting a different sub. Maybe 2 IDQ 12's. Also PPI, Pheniox Gold, and Zapco, are all nice amps to get. I love PPI though, but I gotta give Pheniox Gold a good plug too, plus their pretty close to me, and they let me in their factory :)

[90GSTforME]

fatass, what kind of box is the magma in? Sealed, ported, bandpass(lets hope not)? Whats the volume(of the box)?
I would say to get a better amp. A magma has the kind of excursion that plain hurts but the SQ isnt all that great.
Overall a magma probably deserves more than a 150aII can give out.
The focals will sound real nice.
Resand is right, 6 by 9's kinda suck.
In my car I built two custom plates the size of a 6by9 out of some thin wood and cut the holes needed to mount 5.25 components.
Only problem is, coupled with 5.25 components up front, I dont have very much midbass. Some 6.5 or 7's would help fill it in.
I use 80hz as my sub x-over but if you dont want any annoying loud lowmid bass then 60 hz will be ok. Just make sure the focals can handle 60 hz as well.

in any case, good luck.