Sub/Amp selection and placement
 

Hey guys....I'd like to install a new sub(s) and amp in my boat. I basically know nothing when it comes to pairing the up with a correct amp. I also need some help selecting sub placement. Would you suggest 2 10"s or 1 12" and the most important question is what amp to run with them.

For placement...I have a few options (I think). First and foremost, can I just utilize the existing space under these seats to basically turn it into a box or do I physically need to build a box and then place it in the correct spot? I'm not really interested in a free air sub so sealed or ported box will need to work.

First....in between the 6x9 under the back seat.

http://i999.photobucket.com/albums/a...psfd265f6c.jpg

Second...under the drivers seat. I can face it forward toward the bow, to the middle, or to the rear. I'm assuming I just use the base of the seat as the actual box??

http://i999.photobucket.com/albums/a...ps9e67cf12.jpg

Third...pretty much the same as the last one but a larger box space because of the back to back seats??

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For equipment, I'm not looking for top of the line like a JL W7 or anything but I don't want cheap either. I know the amp is the most important part so that's really where I need the best suggestions.

Thanks!!

Boat stereo = Big amps if you want to be able to hear it. I have my amps mounted up in my cuddy. I have 1 1200 watt amp to run two 12 inch subs that are also up in the cuddy an I have a 500 watt that runs 4x6.5 inch speakers along the bottom of the back seat like where yours are.

Right...but 2 ohm, 4 ohm? Just look for total wattage?

Since your sig is incomplete. Where/what kind of water do you boat? fresh or salt?
Primary listening - in the boat while crusing? in boat party? behind boat party? sand bar?

If you were to use a 12" where do you have the height to install?

Sorry...it's a 24 Ultra Stealth. Used on freshwater lakes in Texas. Music will be mostly listened to while cruising and floating. I'm leaning towards 2 10"s and putting them under the seat facing the isle (third pic) if people think its possible. If I stay away from free air subs, I assume I need to find volume of storage area under that seat to size properly??? From there, I really need help finding the right power to go with them. Are marine grade subs a definite requirement?

Im still picking out subs, but Im putting together a system with 4 mtx 7.7 tm7702 coax's and a directed electronics 1200/5 amp. when 'sizing' you will pick up volume/power with lower ohms (good amps should be 2 ohm stable with a good sub amp 1 ohm stable) . with a stable amp general rule of thumb if that you have an amp that puts out 45 watts at 4 ohms it should be about double at 2 ohms. Now at first you may go woohooo and drop your ohms as low as possible, realize that at lower ohms your amp will be working harder and getting hotter. And it will suck more juice.

Think of it like your boat. You want to cruise at 70. you can put a motor in it that will push it 70 (say a 7.4 330) but is screaming its brains out. Its not going to be very trouble free or live long being maxed out all the time. So you can put a bigger motor in it that will push your boat 90 wot, (say a 525 eti) but at 70 its purring along happy and non stressed and will live a long happy life. At the same token you don't want to go to overboard. If you only have a bravo drive sticking a 1000 hp blower motor in it will let the motor live a nice life as it isn't coming close to breaking a sweat however your bravo is now in 1000 pieces.

So I have good (not excellent) components. My amp is a class a/b-d hybrid. a/b on the four channel rated at 2 ohm stable and I will be running 4 ohms fairly well matched to the speakers and my class d sub channel will be pushing 2 ohms even though its 1 ohm stable. I should be able to set the gains at a respectable level for good headroom while getting decent volume in my little resin bucket.

So running 4 ohm will pull less juice and keep the amps cooler?

Depending on the amp. if its 2 ohm stable yes. if its a 4 ohm amp you are maxing it. it you drop below the ohm rating of the amp you will cook it quickly.


Ohms are resitance, think about a prop. a 21 pitch prop has less resistance against the water than a 24. so your boat comes out of the hole easier with a 21 and the engine revs higher but if you stick a 14 pitch prop on it that's even less resistance but your going to spin the motor 10.000 rpm and grenade it. put a 30pitch prop on and even though your motor can push your boat 70 with the right prop, it is struggling against so much resitance that you actually loose speed.

He could also run the 6x9s in low pass!! I bought a box, modified it, cut the hole in my 25ol under bench then decided to set amp to low pass on 6x9s under bench.. then,.said...$hi$!!! Could have done that., I can tell you that 8" bazooka full range marine sound great!! Had 4 in my Larson.. holy crap!! Sounded good, but I had the room already!!

So how should I match ohm rating between amps and speakers? Do most good amps have multiple ohm outputs? So could I get an amp with 4 and 2 ohm outputs and put a couple 2ohm speakers on it?

The amp has an ohm stability. say a particular amp is 2 ohm stable. now your speakers and how you wire them determines the actual ohm load on the amp. So you are using an amp with a 2 ohm stable channel. your speaker is rated at 4 ohms. So you are running 4 ohms. Now you decide to hook that channel up to 2 speakers. both speakers are 4 ohm speakers. you have two choices in how you wire them. you can "daisy chain" them running the + from the + of the amp to the + of the speaker then from the - of the speaker to the + of the second speaker then the negative of that speaker to the - of the amp. This will maintain the 4 ohm load. However if you run a wire from the + of the channel to the + of each speaker and the - of the speakers to the - on the amp you will load the amp at 2 ohms. So when shopping for speakers pay attention to their ratings.

For what its worth.. my system sounds good inside and out.. I have a 12 in the berth and it will not shake any panties off, but sounds good cruising and while in boat or out. Someone always has a system that will blow mine away. ( have friend with huge peavy he throws on the hatch.. can't compete) so I do have a Bose portable sound dock that I can play on the beach for 4 hrs per battery that sounds awesome.. (Bose!!) So that's what I do!! No need to worry about draining engine batteries or house battery.

Ok if it were me I would get 4 10" subs under the seats. two under the bench (remove the 6x9") one under captains chair and then one under the other front seat. Then get four 6.5" (or 7 o 8" if you want) coaxials or component up high on the sides.

For the amplifiers you get the RMS rating of the drivers and then get an amp that is 125% of that rating for the mid/hi speakers and 150% or more for the subs.

Ok makes sense...thanks. Any suggestions on actual equipment?

Sounds good but a little excessive for what i need haha

Speakers, avoid the duel, lanzar, boss, pyle cheap junk. If money is not an object, jl is good chit. Amp's...Im not up to date on, I prefer old school underated stuff. I have an old Hifonics zues that has been thru hell and back and still works great. The old fosgate punchs (punch 45 etc) put out some power but the fosgate stuff didn't take a beating without crapping out. As odd as it may seem, one of the best sub amps I ever had was a Craig 500 watter. it survived 10 years of desert pounding in my old prerunner, a fire and subsequent douching by the fire dept and that thing still pushed a pair of 12's with ease.

Some are going to disagree with me, but on a boat in open air, less then ideal speaker placement for staging etc real fidelity goes out the window. A midlevel speaker like mtx is fine, unfortunately they don't make the 7.7's anymore. I don't care what your wife says, size matters, cone area moves air. the bigger the better for the most part, but after 6.5 's your choices get limited. Sub's, I don't really think you need 6 10's. If you build the correct sized boxes 2 or 4 will do it. I have heard a single 12 in the CORRECT box with correct power out do a bank of 10's.

You best improvement is going to come from matching your stuff, having enough headroom, then taking the time to tune it, the gains, cross overs, box size and sealing.

Good info. As far as the box goes...will I have to build one and put it under the seat or could I just use the enclosed area under the seat as the "box"

Little bit of clarification.....
 

Impedance = resistance

The lower the number, the higher the resistance. If you have ever been to a concert, those amps and speakers are 16 ohm or higher.....your home is 8 minimum (just look on your receiver)

The higher the impedance....the more "headroom" (clear sonic reproduction) you achieve.

Some high impedance systems exist in car. Tsunami by gm, delco/Bose in early/mid 80's vette.....1/2 ohm. Sounded like azz, but LOUD!

Now to wiring.....two 4ohm speakers wired in PARALLEL ( +'s together as well as -'s and back to amp to same terminals) is a 2 ohm load.

Two 4 ohm speakers wired in SERIES ( + of amp to + of spkr 1, - of spkr 1 to + of spkr 2, - of spkr 2 to - of amp) creates a 2 ohm load on one channel. So, if it is a mono (bridged/bring able) amp, you are using the combined power of both channels.

This brings us to the next conundrum.....

Is your intended use sonic quality, or max out put? Headroom (sonic quality) goes down as the impedance drops.

Bass is mushy....muddy....meaning sound quality is really a non factor. I recommend finding a good class d amp that is mono and 2 ohm capable. I am not demeaning bass in the equation, as it represents 1/3 of the audio spectrum AND lifts the remaining 2/3 of the audible spectrum.

DEI and MMATS are two very affordable brands that can perform well for any budget....as well as MTX. Outside of these three, you are compromising quality, or hitting your wallet.....

For mids and highs, it is an entirely different process of thought. 2ohm and below is simply foolish. Stick with a 4ohm STEREO amp (non-class d) and use quality component speakers. Co-axial speaker are rubbish if there is no external passive crossover. Also, stay away from out of round speakers. 4x6, 5x7, 6x8, 6x9, 4x10

Do yourself a favor:

Put your amps in the cabin. Does not matter if they are ipx rated.....they are in the cabin....however....

Buy speakers that have a rating of ipx 13 of higher for marine use. Forget water....the sun will kill a speaker cone fast without a designation for marine use.

Ok....there are many more variables.....but u have the basics....

Buy what you think is going to suit your needs....not brand specific....but use the info above to guide you.

I personally have a clarion head, wired remotes, MMATS amps on jl 12's, and jl amps on jl 7.5's

Commander, what do you say on subs? Im running a DEI 1200/5 so my sub channel is class D 1 ohm stable So I have 300~600 watts, Just looking for 2 10's. I can glass in boxes if needed, but would rather not spend 2 days hanging upside down and severly contorted to do it.

Nahh

209 watts 15 year old Autotek amplifiers G&S Crossover four sets of 6.5" component speakers in the cockpit 1 set of 6.5" components in the swim deck 3 12 subs

http://i1087.photobucket.com/albums/...ed_640x480.jpg

http://i1087.photobucket.com/albums/...rs_640x480.jpg

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Phragle....

Two 4 ohm 10's in parallel will give you 2ohms terminal load. You will net roughly 120 watts each. That's not a lot so bass and box is everything. Look at the fs number on your sub. It is on the sheet in the box they came in under thiele small parameters. This number will tell you the "resonant frequency" of the sub, and you can design you box around this. Many free online programs will assist you with this. I use term lab, but that's an expensive way to get it right.

A good custom audio shop will have term pro, bass box designer, pro box......

I also recommend no two parallel sides in your box. Parallel sided boxes allow the rear frequencies to cancel eachother out reducing your output.

Because subs play lower, the wavelength takes longer to develop. To help facilitate "loading", it is best to build a box that is vented to the rear and combines with the front in the loading chamber....then vented beyond the box to the listener. This reduces band width, but amplified output within that bandwidth.

This is called band pass. Higher output in a narrow field with less power needed. Plus, you cannot hear distortion from the sub. Bad news is you have to control the sub within the intended range or it will eat itself.

You can find several different designs on line (2nd, 3rd, 4th order)

You could also buy one from a car audio shop prebuilt based on their recommendations knowing which combos they have had success with.

Then, you can go home, rip the carpet off it and glass the outside and inside. Just resin is fine. Then....to tha boat!

I remember band pass boxes... We used to call them cheater boxes... it does make the percieved volume louder but at the expense of tightness. My ears like sealed boxes better for what I listen too. I do agree that building the box to the speaker makes a world of difference. In my younger days I had a ford ranger with 2 hi excursion 12's x'd at 60hz, 2 8s for mid bass running 60-120, then 2 sets of components...Today I have hearing aids.

Bandpass boxes don't work well in a boat. They need the cabin of a car to really acheive what they were designed for. With the open cockpit of a boat they just don't work as well, and with the small gain in output, I would rather have the much smoother sound of a large sealed box. I used a 1.25 cu.ft sealed box on my subs. This was only a 2db decreas in output from a ported box at 40 hz. But I had a 4 db increase at 80hz and the same output at 60 hz.

Sealed box is much easier to design and build for a boat. Ask anyone I have done a system for, or been on my boat. Sealed just works better.

Can anyone answer this?

the box ideally needs to be sized to the sub. and made air tight. So if you go boxed you will either have to build boxes and mount them or build the box around the existing seat. The other plus to a box is that on excursion the sub pulls a vacume. the sealed air pressure helps control the cone. Theoretically this allows you to have less power in the system. The enclosed area under the seat is to big. a 12" sub generally will be spec'd somewhere between 1 to 1.5 cubic foot. you need to figure the area the sub sticks into the box and factor that in. Of course we are talking perfection here, just get it close .

As far as using the seat as a box, I think it is doable. Sealed Boxes are not as picky as ported so if your box volume is a little off, no big deal. Box built to speaker spec is best but hey its a boat. I would put 4 10's under the rear seat and seal off the underside of the seat using some Marine Grade wood or such. That would actually make a box but you will loose the storage space.

Chris