ohm to aim for?

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Member - Posts: 37

Joined: February 19, 2004

Location: United States

Posted: October 10, 2004 at 9:17 PM / IP Logged

When buying a new system is it better to aim for a low ohm like 2 or a high ohm like 8?

ravenndude

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Joined: March 07, 2004

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Posted: October 10, 2004 at 9:24 PM / IP Logged

well the lower the resistance of the subs, NORMALLY: Lower SQ and you can get more watts into it with less money

Higher the resistance, NORMALLY: better SQ and its harder to power properly on a strict budget.

If you want to put 350 watts into a sub wired at 8ohms, you'll need an amp with a power rating of 700watts @ 4ohms. on the other had, if you want to put 350watts in a sub wired at 2ohms, you'll need an amp with a power ratting of 175watts @ 4ohms, but the amp has to be stable at 2 ohms.

So it all depends on how you want your system to sound. As all of the mods here will tell you, try to find some place that will let you listen to a couple setups before you buy it and buy what ounds better to YOU!

Ravendarat

Platinum - Posts: 2,806

Joined: February 23, 2004

Location: Canada

Posted: October 10, 2004 at 9:27 PM / IP Logged

Car audio is generally based around 4 ohms, meaning that most products are aimed to operate at this impedence. When you drop your impedence your THD rises and that translates to more distortion. You can run at 8 ohms but that requires spending a lot more money on amps because as soon as you raise your impedence from 4 ohms to 8 ohms your amp is going to put out half as much power which means if you have a sub with DVC 4 ohms and you wire it to 8 ohms and that driver has a rms ratting of 400 watts then you need an amp that will produce 800 watts rms at 4 ohms. Can add up real quick. If I was aiming for an sq system I would be using A/B class amps and running them at 4 ohms

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

kfr01

Gold - Posts: 2,121

Joined: April 30, 2003

Posted: October 10, 2004 at 9:51 PM / IP Logged

First, click on "Ohms Law" on this page http://www.bcae1.com/ and read it.

The higher the resistence the lower the current (power). The lower the resistence the higher the power. So why not always shoot for 1ohm? Some amplifiers simply aren't built for that kind of current. Even ones that are stable this low usually are pushed harder to convert the low voltage from the battery into higher current levels. They will get hot and the distortion levels will raise. (The pros will also probably say something about damping here, which I think relates to the ability of the amplifier to control the speaker. I'm not to the point where I can speak about it yet though.)

Having said that, you need to pick speaker Impedence based on your amplifier and your goals. As I understand it, 2-ohm mono is usually a good compromise between available power and sound quality (distortion) for subs. 4-ohm is usually the accepted power/quality minimum for main speakers. Sound quality fans might tell you to run everything at 4-Ohms, even the subwoofer.

SPL people, on the other hand, win competitions by earning the highest possible SPL for their total number of 4-ohm watts. So, they'll usually run everything at as low an Impedence level as possible to extract maximum power from their system. They usually own very tough amplifiers that are built for this purpose. SPLers value volume over quality and don't usually care about the added distortion and lack of control over the driver.

If you're an average joe looking to put together a decent system I think a good mono class d amp for the subwoofer running at 2-ohms and keeping to 4-ohm to the mains is a safe bet.

Hope this helps. Pros, as always, please correct me if I'm wrong.

New Project: 2003 Pathfinder

Ravendarat

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Joined: February 23, 2004

Location: Canada

Posted: October 10, 2004 at 10:13 PM / IP Logged

I didnt bother going into damping factor because I thought it wasnt nessasary. I pretty much agree with everything you said and I think you need to give yourself a little more credit for what you know. The average Joe will do pretty much exactly what you recomended, if they are gonna run 2 subs or a single DVC sub, however if you are gonna run a single sub with a single voice coil and you want the best sound quality avalible you are gonna want to use a a/b/ class 2 channel amp and bridge the thing. Reason why you dont use a mono block is because the majority are d class and wont produce as much power at 4 ohms as what a similar priced 2 channel amp will. Thats obviously a generalization. And before anyone asks, I am not even going to include options on a A class amp because most people cant afford them and quite frankly arent using speakers that will benifit from that.

double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

jeffchilcott

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Joined: April 11, 2002

Location: United States

Posted: October 11, 2004 at 7:33 PM / IP Logged

also if you are looking for any type of sq at all, d class amps are not they way to go, look at the Thd on most d class amps and you will see normally see .08 or higher. where a/b amps can go to .05 and lower typically

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ohm to aim for?

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