not very sharp with fine tunning

My set up is as follows HU:Alpine CDA-9827 Amp:Sony Xplod XM-zr604 Subs:Hifonics HFI HFI12D4 12" DVC 4 Ω 600 W MAXX 300 W RMS Well i pretty much got the set up as a gift and well i have 3 questions,any help or input will be appreciated. I would like to know if the amp can handle both subs? i have them wired up in series/parallel = 4 ohm load mode is that the correct way to do it? and finally do i tune the gains on the amp,HU or both? right now im bypassing the amp and just using the hu settings

That amp is 4 ohm stable bridged, yes that is the best wiring option you have. As for gain and crossovers read the How to set gains topic. Most of your questions will be answered there about HU and amp set up in the first post. As for Crossover setting those are usually done by ear and usually better on the amp then the one found on the head unit. In your case looks like the decks onboard crossovers may be better, lol. I usually start with a 80hz low pass to the subs and go from there to blend into the front stage.

Thank you so much for answering. So i dont need a bigger wattage amp right? and well so far i have them at 80 on the hu i will begin testing new combinations tomorrow thank you so much

That amp may put out 250rms if you are lucky at the config you have it at. Which is its best config for power output, 4ohm bridged. The subs are rated at 300rms each. So if you wanted more power you could go with a bit more powerful amp, but those subs are pretty overrated on specs. so i would not put anymore than 500rms for the pair on them. Even then the gain in output would not really be anything audible. If your wanting more loudness i would look at enclosure design first and make it the most optimal enclosure you can for any size limitations you may have. Are you running sealed or ported now?

yea i see there would be no point in a more powerfull one. right now im running ported,would sealed be better?

Ported with that sub would be your best bet for loudness, although enclosure size, tune placement will have a huge impact on the sound and even loudness.

well im really looking for a tight bass sound not loudness i wanna be able to listen to music loud and tight and not just make the trunk rattle.

In that case the sealed might just be what you are looking for. You will probably lose a bit of low end, but it could very well give you a tighter sound. Hard to say without knowing your current enclosure specs.

Thank you so much for the advice i appreciate it so much. will making a sealed enclosure be too much to be a DIY project?

If you have any wood working skills and the tools its not too bad to take on. This site has a nice enclosure calculator here. Sealed is actually the easiest enclosure type to build. Also it is my recommendation to do a sealed for a first time try at a enclosure build. Other enclosure types take more math and planing as well as harder to construct. Using the calculator I linked you can figure out your dimensions to fit the specs or the sub and to fit your vehicle. I am looking up some spec for you now, but it looks as though 1 cu.ft per sub would be about right. If you have any questions or need help designing or with the build, just ask. I have built a LOT of enclosures as well as many other here have. Any problems or questions you have about the construction should be very easy to answer. some basic TIPS for sealed enclosure: Use a minimum of 3/4 MDF for the enclosure. Also you will want to make sure it is as sealed as possible. Use some type of wood glue(gorrila glue, F-26, liquid nail,ect.) for the joints to insure they don't blow apart. There are many ways to secure the enclosure. I use brad nails with f-26 glue, but other may use sheet rock screws and some no fasteners just glue and claps. I prefer brad nails. No filling in screw hole gaps and I don't have to use a load of clamps and wait for the glue to set to go to the next panel. Just my personal preference. Use a tube of caulk to run a bead around the inside seams of the enclosure. this will ensure an air tight seal. Internal bracing is your friend. You can also use a bit of poly stuffing. It does a few things to the sound. some of which are. It can make the enclosure seem larger acoustically. generally 1/2 a pound per cubic foot, But you can use less or more to help tune to your tastes.