is running three subs ok?

technobass

this is gonna be my first system and i was wondering: is there any kind of problem if i want to run exactly 3 GNX 12" subs? what kind of amp do i need to buy and what kind of wiring/bridging do i need to do to make this happen? thanx for the help.

CPHILHOWER

I would use a Mono bass amp that is 1 ohm stable. Like the Sony 300 watt mono class "D". That would make about 840 watts (I cant remember exactly) at 1.4 ohm load. Just Parallel the speakers. JBL also makes mono 1 ohm stable amps.
Chris

technobass

alright, thanx a ton...i just wanted to make sure that running three subs wouldn't give me any weird ohm-age problems...

technobass

another question...what makes a class D amp a class D amp and also someone told me i should get an amp that is at least 500 watts to power these speakers...is that necessary?

sntnsupermen131

what type pf gnx speakers?
i know theyre 12s
but theres like 3 different types
theyre all rated at 175 watts
chris was on the right track about saying getting an amp that is 1ohm stable
the more subs you have...the lower the ohms...the more power you can pull out of an amp
the one thing you shouldnt do
REALLY SHOULDNT DO
is get a sony amp
they are probably some of the worst amps on the market
i use rockford fosgate
some ppl use mtx
ive heard a few good things about us acoustics but ive never seen them in person...only on paper and i didnt know the people who used them
but theyre pretty cheap
-Cody

Jstas

Originally posted by technobass
another question...what makes a class D amp a class D amp and also someone told me i should get an amp that is at least 500 watts to power these speakers...is that necessary?

The biggest difference between a Class D amp and other amps is the power supply. A Class D amp tends to have a "dirtier" power than an A/B which is why Class D amps are recommended most for subwoofer applications. Class D amps will put out alot of power but don't necessarily put out the cleanest power. In a sub though, It doesn't matter as much. Most subs rarly play above 120 Hz and most cycle noise caused by RF and EM interference is well above 120 Hz. Hence you don't get as muddled a sound. However, the power in a Class D isn't always conditioned so well. It can be peaky and inconsistient. That is probably the only valid reason for a capacitor. It provides a fair bit of line conditioning in a 12vDC system which is pretty impossible to condition correctly.

As far as what amp to get, you need to remember 2 things, number one, you are powering 3 speakers. Number two, when you wire the 3 together, you are going to have a low impedance like what is already mentioned. Most subs are 4 ohms. Wiring 3 together will drop that 4 ohm rating down to about 1.32 ohms or so. You will need a 1 ohm stable amp.

As far as power goes, a powerful amp is in order. However, arbitraily naming a power rating is not the way to do it. You need to look at the specs of the amp and it's power rating at what voltage and what impedance. Most amps will give you ratings for 13.3v and 14.4v at 4, 2 and 1 ohm impedance levels. Since you are powering 3 subs, you will need to look at amplifiers that have a 1 ohm impedance level. If you want to run only one amp. As far as the voltage goes, most cars will not run at 14.4 or 13.3. They run in between the two voltages usually so going with the idea that the lower rating is what you are going to see may not be ideal to you but it is realistic. This is part of that "fine print" everyone tells you to read but nobody can seem to tell you what to look for. Well, now you know and knowing is half the battle, yada yada yada...

Now, that info above is only if you want to run 1 amp. If you run 1 amp, you need to consider power because eventhough in reality, it's not this way, you need to think of it this way. If I have 3 subs and I want to run at least 200 watts per sub, I'm going to have to have about 600 watts. This is not the case because each sub will see 600 watts. However, if the electronics are not up to snuff like what was discussed before, that 600 watts on each speaker will fall short because there will be no support behind that 600 watts. That's why you need to think about high power, low impedance capable amps. Since you are running 3 speakers, you need to consider enough power so that each speaker will be adequatly supplied. When you wire the speakers together, you basically turn them into one giant speaker. Since that is teh case, you need to think giant for the power you are putting behind it too. Fortunatly, many amplifiers have that equipment built in so it's easy to think and shop giant. The nice thing about it too is that most class D amps are overbuilt for running at more normal and sane levels. Hence, even the cheapest Class D amps running at 4 ohms will run forever. Then again, if you go cheap, you get what you pay for.

You other option is to have multiple amplifiers. You can run a small stereo amp bridged to maybe 100-150 watts or so per amplifier. You will end up with the 500 watts that someone told you about but it will be spread out, just like we were thinking with the single high power amp. The issue here is that your little stereo amps are most likely A/B class amps. This isn't bad. They won't have as muc power and in most cases are not 1 ohm stable but that doesn't matter in this configuration. In additin, a 500 watt class D can top 600 bucks. The 3 smaller stereo, bridgable amps can cost 100 bucks a piece and end up being about 300 bucks. So you get roughly the same power level for half teh price. You lose some low end oomph because teh Class D is capable of supporting a higher power and impedance load but, what you lose in power, you pick up in accuracy. Because Class A/B amps tend to be cleaner they are tight and more controlled. You end up with accurate bass that has a pretty wide range. You can also compensate for the lost oomph from the Class D by using a good enclosure.

I hope that helped some and gave you a clue to some other options you might be able to consider. In the end though, all this is is advice and you don't have to take it. It's your stereo and you go with what you think sounds the best.

PoweredByDodge

Jstas .... u should teach classes... (not a rip, just a joke).


... far as what amp and whatever...

I'd get the singel 4 ohm version GNX's... either 10's or 12's... and I'd then get an amp that as Jstas said is about 600 rms or so into that 1.33 ohm load.

While all of these are not rated safe for 1.33 ohms, they in fact are.

- JBL 600.1
- Mtx 6500D / 801D
- Orion 600D


or you can try and slightly overdrive a 2 ohm stable bridgeable amp like the...

- Autotek XS550.2 (550 x 1 at 2 ohms).

but you're better off tyring the class D's -- they tend to be able to take "abuse" better.

technobass

ok, so i saw this amp today....an mtx 4500D i believe? it was a mono amp that was rated at like 300 watts @ 2 ohms i think... would that be a good choice for my application?

CPHILHOWER

Careful, It may not be 1 ohm stable. You could damage the amp if not. Or it may just cut out at high volume. PBD seems to know more about these amps than I.
Chris

ntculenuff

ntculenuff thanks

technobass

naaa....not good enough to throw anything onto a cd yet...but when i deem myself ready i'll let you know...it'd definately be sweet to spin for some parties or sumthin...i'll be sure to keep that email handy....


and the dude who worked at the store told me that any mono amp would be one ohm stable...and that mtx was a mono amp

Jstas

The dude at the store was full of crap. Maybe all teh mono amps they carried were 1 ohm stable but not ALL mono amps are 1 ohm stable.

The only way to really know is to look at the published specs. If the peopel at the stores won't tell you, goto the company's websites and look at the specs of find a place that will tell you what you want to know rather than what they think you should buy.

As far as the MTX amplifier you are talking about, you need to provide more info. Since you are running 3 subs, a 2 ohm rating is not going to be correct and you should not base your decisions on it. You need to look at the 1 ohm rating of the amp, if it has one. If it doesn't have a rating for that impedance then I would not use it for that impedance. It may play at that level but like what was said, you will most likely damage the amp.

technobass

so do y'all have any amp reccomendations that won't break the bank? maybe a place to buy amps for cheap? any kind of info that'll help me out would be appreciated

Jstas

http://www.carstereotime.com

http://www.carmedia1.com

Both sites sell at whole sale prices. Someone here said they could get stuff at cheaper distributor prices. Anyway, check those sites out. They probably have what you are looking for at about a 30-50% discount off of retail.

As far as recommendations go, look around, see what interests you and then come back with your ideas. We can give you better help then. Find a few that you woul be interested in so we having something to compare.

ntculenuff

pleasee do keep the email would like to hear sumthn' when you feel ready...Xtant makes one hell of a mono amp for a grand

Systems

www.onlinecarstereo.com is cheap too
-Cody

PoweredByDodge

hey technobass ---

there was another guy in this forum doing the same thing u are....

the mtx 4250D / 250D will work fine.

you're going to run 3 4ohm 12's = 1.33 ohms.

while the 4250D / 250D is only rated at 2 ohms and is not "technically" 1 ohm stable, it is... read the other post in car subwoofer talk regarding it, but basically through a lot of experience with the mtx class D amp line and through many a many conversation with the Mitek guys regarding such, you can surely run the 4250D / 6500D / 81000D (250D/500D/1000D) at 1.33 ohms all day with no problems as long as you provide proper gauge power and ground wires, a sufficient electrical system, and are not completely stupid and run the thing with the gain all the way up to full throw, far beyond the point of distortion, and purposely drive it into distort (which i hope to god would not be done to any amp unless you were doing SPL comps).

the 4250D/250D will do something like 350 - 370 (estimate) at 12.5 volts and 1.33 ohms. your birth sheet will be something like 300 x 1 at 12.5 V with less than 1% distortion... but keep in mind thats the 2ohm rating -- while your wattate goes up a hair, you're also going to get a little more distortion, but you'll still be well well well within the limits of what is "clean" for this subwoofer application (note - i stress for THIS application).

you're other amp option (on the really cheap) would be the JBL BP300.1 -- 300 x 1 at 2 or 1 ohm (same power at both impedances)... but I still would take the mtx product over it...

Ideally if you're on the cheap and want power I'd get that JBL BP600.1 or something compareable -- a 1 ohm stable 600 watt mono amp... that way you get plenty of power to each subwoofer instead of trying to STARVE the poor speakers and stretch the limits of an amp.

you can find a 600w 1 ohm stable amp if you really hunt ebay, hunt online stores... do some nitty gritty.



(and someday I think me and Jstas need to throw the wood down on these friggin Circuit City / Best Buy 17 yr old - dont know there ear from a hole in the ground - people... "all mono amps are 1 ohm stable" -- ya and caps are filled with sand too....) ...

sntnsupermen131

lightening audio caps arent pbd
just all the other ones...
man get it right...lmao
-Cody

technobass

was that estimated 350-370 per sub or divided between the three...and was that rms?

PoweredByDodge

techno -- thats TOTAL RMS ... so divide that by 3 = 120 - 125 watts per subwoofer rms... the gnx are rated 175 --- personally i like to to have a good healthy few extra watts... like me i'd get an amp that was 600 watts so i had 200 watts per sub, even if i didn't use all of that power.

sntnsupermen131

it is not recommended to power your subs less than 75% of their rms power
175x0.75=130
130 is the least per sub
10 watts really wont matter though
but im with dodge
get a 600w amp
remember this
speakers are blown more frequently when they dont have enough power than when they have more power
if they dont have enough power the amp will try to push out more power than its capable of thus and it will cause the amp to "clip"
another words it will send really bad things to your speakers that they cant handle
-Cody

technobass

yeah...i had that problem with my home stereo a while back...i was blowing tweeters cuz the amp was pushin too hard and causing distortion at tweeter-toxic levels....

technobass

hmmm....i'm startin to get a grasp but i'm gettin lost in numbers a li'l bit...can someone tell me in simple math terms how you figured what the wattage the amp was putting out after being bridged was and how you came to how many watts an amp would give to each of three subs? (i suppose i'm asking for the math formulae to figure this junk out on my own...)

and maybe gimme a whole list of amp reccomendations for me to look at so i can compare them once i know this formula and choose what's right for me.....

(that was really wordy, but i don't think it should be too hard....PLEASE GIMME A HAND.....thanx)

Jstas

You don't need to worry about the math. It doesn't have to be an exact science. The amp manufacturers have already figure it out for you anyway. Most of the numbers used in teh above examples were arbitrary, meant only to get a point across, do not take them as gospel.

You should always read the specs and make sure that the specs for the amp do not exceed the specs for the speaker. While some drivers may be able to be over powered and some amps may be able to be over driven beyond thier published numbers, the only way to ensure proper and trouble free operation is to stay within the published specs.

As far as figuring out what the wattage and such is like asked about above. I did no calculations. I merely gave you an educated guesstimate. I know I am in the ballpark because I have had a good deal of instruction on electrical circuits. I'm not about to go over 3 terms of Physics and electrical theory on an internet message board. For that you will just have to pick up a book. But again, the consumer end of this is not an exact science unless you are constructing your own equipment, which I doubt you will be doing.

Just look at everything you can and soak in as much as you can. You will get the hang of it eventually and then you will be able to understand the specs and make determinations on equipment from that.

sntnsupermen131

jstas is right
look at the specs
theyll tell you everything you need to know
as for a list of amps
go to www.crutchfield.com
click on amps
and they have a small summary of all the amps they carry including basic specs and price
they fit like 20 on a page
i would be looking for an amp that has 600 watts x 1
or 500x1
so look for that
and there you go
-Cody

technobass

y'all have any box ideas for me? (98 mustang aka small trunk/hard to get stuff through the oddly shaped/positioned opening)

PoweredByDodge

Originally posted by technobass
(98 mustang aka small trunk/hard to get stuff through the oddly shaped/positioned opening)

this box will supposedly fit the spare tire well of a 99+ mustang... dunno if the 98 is close enough to make it work... u'd have to ask the retailer but check it out...

http://www.sounddomain.com/sku/SOUTWBK6

houses two 10's... which i know you want 12's... so if this box would really work for u and u dig it then hopefully u haven't made the purchase yet or haven't opened hte box and can return htem... but anywho.. you could build another enclosure for the third one directly "in front" of it... would look pretty damn pimp.

other than that.. if that doesnt' fit i'd say doing SOMETHING in the tire well is proly the way to go, at least get one of them down there. save you SOME space.