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Home Theater Powered Amplifiers


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#1 of 15 OFFLINE   ando

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Posted July 30 2011 - 11:42 PM

Hi, So I got a pair of BIC America F12 Front firing 12'' subs that have 475 watts running to each. Being the person I'am I was trying to find some home theater powered amps for a DIY project. Im getting a 15'' Rocker Fosgate subwoofer, nothing too big its only a 250 Watt RMS and 500 watt max, though the max watt really doesn't matter :D ...... This is also an 8 ohm sub cause I know some basics about home theater systems, like they run on 8 ohms i think :confused: ..... Im a big car audio guy so i know wiring and ohms and all that mumbo jumbo. Now for the second question, if i get a powered amplifier do i need to run the sub at 8 ohms cause thats probably what the amp runs at or do home theater amps run at 1, 2, 4 ohms not just 8? Or maby im just sounding stupid and this isn't a right way to go at this DIY project, I do know that car audio subs are way louder than home theater subs. Well thats my own opinion anyways. But any help picking out an amp that will work fine giving the sub a little over power won't hurt it. Thanks

#2 of 15 OFFLINE   Robert_J

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Posted July 31 2011 - 01:49 AM

Im getting a 15'' Rocker Fosgate subwoofer, nothing too big its only a 250 Watt RMS and 500 watt max, though the max watt really doesn't matter biggrin.gif

The RMS doesn't matter about 1/2 of the time as you reach the driver's mechanical limits well before the thermal limits.

This is also an 8 ohm sub cause I know some basics about home theater systems, like they run on 8 ohms i think

My home theater subs are quad 2 ohm voice coils wired for a final load of 2 ohms nominal (1.78 ohms Re). Subs don't matter because they have their own amp. My sub amp is capable of driving a 2 ohm load in stereo.

if i get a powered amplifier do i need to run the sub at 8 ohms

Depends entirely on the amp you get.

this isn't a right way to go at this DIY project

I agree. I can help you approach it in the correct way if you want.

I do know that car audio subs are way louder than home theater subs. Well thats my own opinion anyways.

Your opinion is wrong. First - There are no such things as car subs and home subs. That's just marketing mumbo-jumbo. You have to look at the Theile-Small parameters to determine how the sub will perform in your environment (home, car or both). Look at TC Sounds. They give both small (car) and large (home) recommended enclosure sizes. Even through Fi Car Audio markets exclusively to the car audio crowd, some of their drivers work great in the home. The old Adire Shiva and Tempest were marketed to the home theater crowd (usually in this forum) but the car audio guys started to use them and a local guy won the Tennessee SPL competition using four Tempests. Second - Ignore the power rating when using a sub in a home theater. You should be more concerned with xmax (excursion). Depending on your enclosure design, you will reach xmax well before you reach the thermal (where things start to melt) RMS rating of a sub. Finally - Impedance of your sub is not determined by what impedance your receiver is designed for. You have to look at the amp you will use for your sub. 99% of the sub plate amps work best at 4 ohms. Pro amps like I use work great at 2 ohms stereo or 4 ohms mono. There are a few exceptions to this rule. Your amp should be your last part of the puzzle after designing your sub. You have no idea how much power you need right now to get the maximum performance from your sub. You know nothing about the maximum performance of your sub because you haven't come up with any goals and designed an enclosure. You can't design an enclosure until you know your size limitations and the T/S parameters of the driver.

#3 of 15 OFFLINE   ando

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Posted July 31 2011 - 03:08 PM

Well i don't know about my opinion being wrong, i hooked up a crappy kicker comp in my house running 200 watts and it was far more bass than 2 475 watt home theater subs. Im sure if you get better home theater subs for more money but kicker comps are at the bottom of the barrel subwoofers. But also i know home theater subs are suppose to flow with the movie/game. you said i can't design the box until i know my size limitations. I don't know if it would change for a car box but i already know it needs a 2 ft cubic box minimum or a 4 ft cubic box cause im making it ported. I don't see why a home theater box would change cubic feet than a normal box thats put in a trunk, besides design to make it look a little more house worthy. The mounting depth has to be 7'' or more, i already know the xmax is 15.5 mm. I knew all this to begin with but I was just trying to find a powered amplifier i have been searching for them but they are all like DJ amps and i don't need that powerful of an amp. i also asked about the ohm capabilities since the other speakers are 8 ohm i just figured the powered amps would be also. now that i switch subs which don't get me wrong this is just suppose to be a little project that im just having fun with to see how much bass im going to get. This sub is no where near an awesome top grade sub just trying to find a week project to play with. But Robert_J if you want to try to lead me into a different direction ill be happy to take ur advice. you have always been helpful to me so give me your suggestions and anyone else who wants to throw a suggestion in i wasn't looking to spend a bunch of money but i spose if im going to do it might as well do it right :P .

#4 of 15 OFFLINE   Robert_J

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Posted August 01 2011 - 07:08 AM

i hooked up a crappy kicker comp in my house running 200 watts and it was far more bass than 2 475 watt home theater subs.

You need to look at the sensitivity of each driver as well as the enclosure it is in. If those home theater subs are designed to play low, then you are giving up sensitivity for extension. All of that is explained in Hoffman's Iron Law - http://www.salksound.com/wp/?p=56

Im sure if you get better home theater subs for more money but kicker comps are at the bottom of the barrel subwoofers.

Go to Ebay and you will find the bottom of the barrel. If they are old Kicker subs, they were built by build house Credence Speakers - http://www.credencespeakers.com/ . Currently Stillwater Designs has Deon Bearden working for them as the Acoustic Engineering Manager.

But also i know home theater subs are suppose to flow with the movie/game.

What do you mean by "flow"?

I don't see why a home theater box would change cubic feet than a normal box thats put in a trunk, besides design to make it look a little more house worthy.

Most, if not all sealed designs for cars have a final Qtc of 1.0 or higher. If you go sealed, you want a Qtc of .707 or lower. I'm partial to a Qtc of .5. For ported in a car, you tune it to 30 or 35 hz for normal listening. 40 to 50 hz for SPL burps. If you want to play this in a home theater, then you need an Fb of 25 hz or lower. Try to tune a 1.5 cubic foot box to 20hz and have enough port area. You will end up with a port that is 5 feet long. Ports that long have a resonance that is in the passband of the sub. To remedy that, make the sub enclosure larger. Not only is it easier to tune low, you also get more efficiency (see Hoffman above).

I was just trying to find a powered amplifier

Since you are going ported, you need an amp with a proper subsonic filter. If you tune your sub to 20hz, you want your SSF about 17 or 18 hz to keep the extreme low bass from destroying your sub. When playing signals below Fb, your driver is completely unloaded like it is playing free-air. A 10hz signal may only take 20 watts to push it to xmax. That said, look at the plate amps from Parts Express.

if you want to try to lead me into a different direction ill be happy to take ur advice

I want to teach you want you are doing. Show you where your ideas will go wrong and save you from wasting money. I've been blowing cash on subs since 1985. Back then it was mostly trial and error with a single book telling me about how a speaker works. If you decide to go a different route, I'll help you also.

i wasn't looking to spend a bunch of money but i spose if im going to do it might as well do it right tongue.gif .

What is a "bunch" to you? I'm sure our definitions are completely different. I paid a load for a 100% custom sub. http://static.hometh...um.com/imgrepo/

#5 of 15 OFFLINE   ando

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Posted August 01 2011 - 05:06 PM

i like that sub good magnet size what is that a 15? a bunch of money im saying now more than $1200. I want a 15, and im buiding my box and everything so the sub and amp are going to be the pricy bit but if its less than a $1000 then thats even better. Im trying to not spend a lot on this sub do to me buying a 1080p projector soon. Ive been buying subs since 08 and i was a professional installer in college so im able to figure things out on subs fairly quick, i just like a little guidance with this home theater stuff and u most def. know what ur doing with this so any ideas are great

#6 of 15 OFFLINE   Robert_J

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Posted August 02 2011 - 12:44 AM

i like that sub good magnet size what is that a 15?

Yes, it is a 15. It's a Konaki motor (Digital Designs clone) with an Eclipse Ti / TC Sounds basket. The soft parts are from fixmyspeaker.com . I wanted a low Qts sub that could handle about 1600w at 20hz in my home theater and David from FMS hit the target exactly.

a bunch of money im saying now more than $1200. I want a 15, and im buiding my box and everything so the sub and amp are going to be the pricy bit but if its less than a $1000 then thats even better.

What are your performance goals? Movies - what type? Music - what type? How much of each? How large is the room? How loud do you listen? What is the rest of your equipment?..........That's a great budget for the sub and we can definitely build something that is world class. Look at retail subs of that price and you can beat them easily.

Ive been buying subs since 08 and i was a professional installer in college so im able to figure things out on subs fairly quick, i just like a little guidance with this home theater stuff and u most def. know what ur doing with this so any ideas are great

A lot of people who come over from the car audio world have misconceptions about audio. The environment dictates a lot. To get the same performance in the home as you do in the car, you will need a room about the size of your average coat closet. As the room grows, environment gain (cabin gain in the car world) decreases. There is a point where in a large room, you can only rely on the performance of the sub without any help from the room.

#7 of 15 OFFLINE   ando

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Posted August 06 2011 - 03:43 PM

My goals, my goals are simple i listen to a lot of music and watch a lot of music, i don't video game very much but when i do i play loud. I play a lot of sports games so i drink beer and play games lol. I listen to my music loud i have 2 12'' F12 BIC America front firing subs, with 2 tall sony speakers which i have rocker fosgate car tweeters and 5'' round speakers. I have them wired to 8 ohms then i have some satellite speakers which i can't recall what brand they are due to me being at work but they sound great. My room is fairly big vaulted ceiling and it combines into our kitchen and dining room. I love bass and going overboard with bass is impossible in my point of view unless you can't hear any other sound besides the bass. But i still turn down the subs a bit when i watch movies so you don't have the constant humm from the subs at normal dialogue. But when i listen to music that bass is jacked up and i listen to music lol. There is nothing wrong with the 2 BIC's i have but i could always add more bass to it.

#8 of 15 OFFLINE   Robert_J

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Posted August 08 2011 - 01:45 AM

Are you replacing the BIC subs? (I'll bet you will after you build the sub) How large of an enclosure or enclosures can you live with?

#9 of 15 OFFLINE   ando

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Posted August 08 2011 - 03:50 PM

I don't know about replacing the BIC's they are great subs for their price and I'am for any size of an enclosure as long as it isn't as big as my couch lol. Unless I get 2 subs then its legit if its as big as a couch :D. But i don't know seriously the size of the enclosure really doesn't matter to me im not trying to hide it i was wanting to make it a front fire sub also

#10 of 15 OFFLINE   Robert_J

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Posted August 09 2011 - 07:59 AM

Can you live with an enclosure this large? http://www.danmarx.o...n/tcsounds.html Use this driver - http://www.parts-exp...tnumber=295-468 Use this amp - http://www.parts-exp...tnumber=300-750 If you want to use up your entire budget, build 2.

#11 of 15 OFFLINE   ando

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Posted August 09 2011 - 04:13 PM

That is PERFECT that enclosure is just fine, the driver and amp look pretty good also. Now is this sub going to out do the 2 BIC F12's i have?:D lol that enclosure is gonna take me some time to build, it will be perfect probably not as perfect looking as his but it will be dam close thanks for a good weekend project :D I was looking at it should i just use 3/4'' MDF wood? PS. I plan on having this hooked up with both the BIC F12's going too, hopefully i get some great bass

#12 of 15 OFFLINE   Robert_J

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Posted August 10 2011 - 05:56 AM

One of these will probably equal both of the BIC subs in output while sounding better. That is a great, low distortion driver. Yes, MDF is the standard material for building a sub enclosure. Too bad Soundsplinter isn't selling drivers because one of their 15's could easily double the output of the Dayton. Just to throw it out there. 4 enclosures - http://www.danmarx.o...ion/tc3000.html 4 drivers - http://www.parts-exp...tnumber=295-468 1 amp - http://www.bhphotovi...Ntt=ep-4000&N=0

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Posted August 15 2011 - 11:38 PM

Wow 4 of those 15'' drivers for only 172 or are they 172 each i don't know lol i might just be stupid but it is the last part of work shift for me so my brain is fried lol

#14 of 15 OFFLINE   Robert_J

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Posted August 16 2011 - 12:14 AM

They are 165 each since you get 4. There are no cheap drivers any more. If your favorite neo tweeters haven't gone up in price, they will. China recently raised the price of neodymium by 1,000% or some similar astronomical number. That's why neo based sub prices have gone through the roof - http://www.parts-exp...tnumber=293-674 http://www.incrimina...ge=2&product=22 Stick with the less expensive ferrite based subs like the rest of us. I got lucky and bought 4 neo based sub motors a few years ago for $25 each. They are selling used for around $300 now.

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Posted August 16 2011 - 01:44 PM

All i have to say is damn china