Gday people

Im a new member

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i got a big issue startin to get on my nerves

lookin at buying a sub and an amp to match

me personally im a apprentice refrigeration mechanic,

at trade school done a couple electricity modules,

ive learnt that when talkin wattage RMS is exactly half of max wattage,

a completely different story when talkin voltage or amps,

BUT when talkin in a store to sales people i literally got in an arguement

with a salesman who was tryin to convince me that RMS is not half max wattage,

he tried tellin me its different in car audio no reason why it just is and knew that for a fact because of his 18 years experience in... RETAIL.



what should i be lookin at for the right pick of matching sub to amp?

Is wattage the biggest factor when picking a sub?

Do i need to match the powers?



Please help!!!!!!!

The sales man who had 18 years of experience couldnt explain why RMS figures are not always half of the max wattage he is not wrong, but he is just 'parroting' what he knows (assumes).

He was actually right though, not basing this off what packaging or advertising says as a claim, but in relation to a sub the RMS value is the amount of power it can handle thermally, so a sub can handle 300rms and it stays cool enough not to fry, but can handle 1000watts of peak power and still stay cool enough not to cook the Voice coil, the 1000watts is only sent to the sub for a minimal amount of time not causing damage.
Now if we send 500wrms half of the sub rated peak, I would suggest you are going to have some problems. Just an example.

With amps it all depends on components, the guts of an amp will dictate its RMS and peak power rating, however with an amp it is fair to say peak watts is close to double the RMS value, not always true though, It can sway either way.

Matching the power is not necessary when picking out subs and amps, however it helps so you dont over drive the sub or amp(clipping) if either is not matched properly.

How much power where you thinking of running? and what amps and speakers?

Hey thanks that helps lots



at the moment im almost certain on the soundstream tarantula 12" 900WRMS

on sale at motorquipe $350 ATM.

So i was gonna try and match that with a 900wrms amp.

but a good amp at that wattage seems real pricy.



any suggestions?

Yeah not a bad choice the Soundstream subs, quite a few run them on this forum. As for power for it, It can be expensive to get good power, with that sub I would be looking at an amp that can put out 1000+ rms.
The second hand section here you might be able to get something really good at a good price, worth considering. For new cheap and decent qaulity amp check jaycar amps -
http://www.jaycar.com.au/productResults.asp?FORM=CAT

they are great subs, some guy on here is running em off a XXX6500D and they will take it. However its all up to your budget, a 2000D would suffice however if you get an opportunity to get your hands on a 3500D you won't be disappointed. i currently have 1x T4-10 running off a 1500D and it loves it.

This is not completely accurate. There are two ways in which a sub can be pushed to far. The first as outlined is the coils themal powerhandling which relates to gauge and resistance of wire, wire type, how its wound (layers) length of the VC, how its cooled by the motor etc.

The second is the X-mech, this is the mechanical limits of the driver, excede this and either the suspension (spider or surround) will be subject to massive stress and most likley tear, or the bottom of the coil will hit the back plate thus damaging the coil and the former.

Thats true, most subs however will be thermally prone to damage before the X-mech, a culperate for the X-mech being destroyed due to over excursion with the coil hitting the top plate is the ID-MAX, a brilliant sub when not pushed to hard, but it is likely to over excurt before it fails thermally off clean power, clipped power will have a different outcome.

Most subs I see thermally damaged are done so by clipping. You don't see many people who can cleanly overpower their woofers. Most of the time they will probably cause mechanical damage first due to a crapty enclosure.

Remember that when MAX watts are used in car audio the marketing department decides them more often than not, so they aren;t numbers you can rely upon in any meaningful fashion.

My best advice is to ignore them completely.

Buy as much power as you can afford - simple as that.

MAX power is an example of what charger did to a Rampage sub

Relating to an amp to suit, if you're after daily clean power, you don't need to feed it to it's full potential or feed it 1000w+. Instead, go for "quality over quantity" power. An example would be the MRD-M605, which puts out 600wrms @ 2 ohms (spend about $1 a watt).
Ensuring reliability, sound fantastic, and still go bloody loud for daily. If you're planning on SPL comps etc, then buy cheap watts.

Hello all,

the RMS value of a signal is 0.707 of the peak signal.

Hope this helps.
Bye!

That value is true.
Except with car audio some brands use peak figures as marketing gimmicks that are not actually the products peak figures.

i remember a big debate about how 0.707 isnt really a reliable way to calculate

BEST ADVICE EVER!!



I'll add, buy an amp that can run reliably at 1 ohm.

A great example of an amplifier that can not run reliably at 1ohm is the Clarion DPX11500 As i have learnt the hard way . . .

1 ohm is an arbitrary number. not too many 1-ohm subs out there which are really 1 ohm, usually 2, 4 or more ohms due to impedance rise and box volume, etc.

if you don't clip it, it'll run fine. (unless its a poo amp to begin with).

If you get a good 1000W amp, it'll be fine at lower powers.

/thread mine