Competition Newbie build help

[Loud(ish)_Geo]

Meca clamps actual power and combines that with the cone area in sq inches to determine pressure class. A 15 on a 1200w amp should be in the lowest possible pressure class. If its a true 1500 class, you will be seriously outgunned because the impedance rise puts you at roughly half of the amps rated power which is about 600 +176 sq in of cone area so that puts you at 767 which is half of what is allowable. It would be like bringing a safety box cutter to an AR15 shooting match.

Ohh, ok I've heard of "box"/ impedance rise before, but never really had it explained or known how drastically it effected power. How big of an amp should I need then. A 2k, 3k, or more? Or would it be a better idea to build the box see how far under tested power my amp does and buy an amp using that number

 

[THATpurpleKUSH 5,000+ posts]

Generally you will clamp half power your amp is rated for at its lowest impedance level. Impedance rise at burp frequency is usually 2-4x the original load ( figure 1 ohm load rising to 3 ohms) Coil spec and box design are some of the variables that will affect that but it's always to be expected.

Is there any way to switch to 2 10s? You could get by with a smaller box and maybe get into Street 1 which is 0-750. That would allow you to clamp up to 592w which is near the most you would see out of that amp.

If you want to be competitive in that 1500 class then you need to increase cone area (multiple smaller subs that require less airspace) or double the power. The latter might get you a Phat 15 award at a show but I wouldn't expect it to be top of the class unless there aren't many other competitors.

Low cone area on high power needs an efficient box design.

Higher cone area is always inherently more efficient so box design isn't as crucial if you want to be placing near the top.


Invest in a good clamp meter and dmm for your own clamp tests or a Term Lab Magnum which is the official measuring device that Meca uses.

 

[hispls 5,000+ posts]

I've heard of "box"/ impedance rise before, but never really had it explained or known how drastically it effected power.

IF you're planning to use this for music most of the time, it won't matter all that much, but if they use clamped power as you run you could very easily buy a 2K or 3K amp and just dial in your gain at a specific volume level so that you consistently measure just shy of the maximum allowable power when you're actually up on the meter. If they're not going by what's printed on the amp or in the owner's manual may as well go big, much easier to turn it down if you're clamping too high than getting more power once your amp is at maximum output.

You will not know what your impedance is at any given frequency until everything is installed, doors and windows open as allowed, glove box, visor, and seats adjusted, etc. etc. and you actually measure whichever frequency real world real time. NOBODY can accurately predict this and there's little you can do to change the impedance once you've dialed in a good peak.

 

[Loud(ish)_Geo]

Alright, well I've taken alot of everyone's suggestions into account and I'm now planning on an hcca 3k (I'm fully aware that it is more than overkill) as it would allow me a ton of room to grow, and I'd be able to run it at 2ohms to be more efficient and not have to worry as much about power supply. My only current questions are
1. What do I honestly need to power all this as basically all I know for sure is that I'm gonna atleast need a big three and secondary battery. I don't really know what size battery or if I should do a bigger/secondary alternator as well because my car only has an 80 amp alt rn
2. How big of a difference two tens rather than a single 15 would make. I'm currently between an american-bass XFL 15 or two Titan 10s and I don't really know which setup would have more output at the ~1200w clamp I need for the class

 

[Buck 5,000+ posts]

That would most likely be a colossal failure. If you're not going to do a proper flat wall you should consider staying in the trunk. What you have illustrated may well put you into a wall build class too which will have you in the lanes with guys who have you beat by 20dB.
First and foremost you should figure out which organization has shows local to you and read their rule book to figure out what class you're going to be in and consider the limitations. Next buy an SPL meter. You definitely will never be competitive if you do not own one or have easy access to one. Best yet would be to find a local team or crew who competes a lot that you could join and share ideas and resources.

@Loud(ish)_Geo , I would consider this man's advice^^^

 

[Loud(ish)_Geo]

@Loud(ish)_Geo , I would consider this man's advice^^^

I straight up, don't have the room to fit a competition system in the trunk

 

[metalheadjoe 10+ year member]

Alternators help

I straight up, don't have the room to fit a competition system in the trunk

You have several of the most hardcore guys on this site giving you advice. Take their advice or quit asking for advice, because anything else is not going to be ideal.

On the alternator vs battery question, alternators provide power when running, batteries provide power when not running. Does your vehicle make enough power to spin bigger/extra alternators?

 

[Buck 5,000+ posts]

I straight up, don't have the room to fit a competition system in the trunk

What are exactly your goals at this point? Like seriously asking, not poking fun or anything. There's been a lot of discussion now, what do you think you want to try to do at this point?

 

[Loud(ish)_Geo]

What are exactly your goals at this point? Like seriously asking, not poking fun or anything. There's been a lot of discussion now, what do you think you want to try to do at this point?

I honestly just want a semi-competitive MECA SPL M1 class system (no world beating, I'd be perfectly happy with finishing middle of the field) that still leaves me with usable storage for longer trips to events and shows (which is why I'm not super willing to do a trunk class system), and still gives me decent musicality when I'm not in competition.Also, I've definitely consider a flat wall more than a couple times. I just figured I'd start with the slightly more traditional box first to see where it falls in terms of dbs before really having to tear up my interior because even tho it's not worth much the car's more than a little rare nowadays which would make it really complicated to get it back to stock if I ever felt the need to.

And, honestly, I'm sorry if it's not coming off that way but I really am taking into account every bit of advice I'm getting. I mean absolutely zero disrespect. Trust me I'm more than aware of my lack of knowledge vs people who have been in this for many years.

 

[THATpurpleKUSH 5,000+ posts]

You need to do at least a 142 in that class to be competitive.

2 10s on a 1.5k is all you need. Subs dont matter as much as the box and amp.

 

[hispls 5,000+ posts]

You need to do at least a 142 in that class to be competitive.

2 10s on a 1.5k is all you need. Subs dont matter as much as the box and amp.

He is set on doing this out of the backseat somehow. Not sure if that even keeps him in non-wall non-extreme classes.

Also looks to me as though cone area (square inches) adds up to the same as watts when it comes to classing competitors so I'd imagine using more cone area than power would be optimum. 2 15s on 500W is the same class as a single 10" on 1000W. All things equal, which do you suppose would be louder?

 

[THATpurpleKUSH 5,000+ posts]

I read it as street 1 not modified 1.

You need to bring a high 40 to be mid pack in modified 1.