Simple Amp question.. 101

[Chromatic]

Hey guys.. I've basically figured out my semi-budget $900 build,.. and I'm running two 6.5" Mids and 3/4 component tweeters that run at 100rms.

I am running off a AVH-P4100DVD Head unit.

Will be running a Custom box to fit where the factory sub does (.66 Cubic Ft, sealed).

In this Custom Box, I will be running a JL Audio 10" W0 (maybe W1)

And the Amp is 4 Channel,.. Two channels run at 120Watts RMS a piece,.. and I will be bridging the last two channels for 400 Watts RMS (Stable at 4 OHM) for the Sub.

Simple setup, but effective.

The question is,... Is it safe and "ok",.. to run 120watts RMS to a 100watt RMS rated Front Stage Mid + Tweet speaker?

On the same token -- Depending on sub.. The rated RMS may be 350watts, or it may be 400watts (400 to 400 I know is fine). So technically the sub, if picked, could be obtaining 50 more watts RMS than it's rating.

I've heard a few things .. but the two black and whites here are:

1) No! That will ruin your speakers.. it's too much power, do NOT exceed the RMS spec.

2) Yes, it's fine. That gives the amp headroom , it doesn't have to work AS hard,.. and the speakers will be fine.

First, which is it? And no matter which line you take, do you mind briefly explaining why that is the case?

Appreciate your help!

Click to read more...

 

[juanmgarza26 10+ year member]

set your amp with a dmm, set your amp to give the rms of the speakers, youll be fine, your amp is 120 rms but 120 rms will only be seen when you're playing full tilt...

 

[garychurch84 10+ year member]

2 Just because an amnp is rated at X amount of power doesn't mean you have to apply it all

 

[bbeljefe]

Answer two is correct. There are a number of reasons why but to keep it simple, a speaker's impedance is not static. i.e. it rises above it's nominal impedance when in use and thus, will not draw the full power from the amplifier very often. And when it does, that will be for only a few seconds at a time.

In car audio, it's pretty common to run mids and highs at ~25% over rated subs 50-100% over rated.

 

[VWBobby 10+ year member]

2.....and then.....1 //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

I usually buy an amp that has more RMS output than your speakers require. You will have more headroom, and your amp will be below its output when the THD starts to rise. In other words, your amp will have cleaner sound if you are running it at 50% power than running it at 90-100% power all the time.

Back in the day, a lot of people would run DOUBLE RMS power and turn up their amp no more than half way. Especially in home audio.

Adjust your gain until you are not putting out much more power than RMS. If the speakers can handle more than RMS, than you can set gain to that level. This is still "playing it safe".....

 

[Chromatic]

Thank you guys for not "roasting" me on this question. It's the answer I was hoping for. I have a setup I'm about to buy (been shopping each part out for a while now..) and the amp runs 120watts RMS for each channel.. The front mid and high stage only take 100 RMS,... I'm running the single 10Inch sub in custom box sized for this car and sub, and this sub takes "Max" 300watt (Whether I get the w0 or w1 version, the power is the same). The amp I'm buying runs 400watts at stable 4 ohms when bridging two channels to 1 (ie: for the sub) -- Which is a clear 100 watts excess.

So, this is a good thing!

I'll have 20% headroom on Fronts, and 25% headroom on the single sub.

So I'll set the amp at 80 percent for channels 1 and 2 respectively, and set it to 75% for channels 3 and 4 respectively.. and each speaker will receive it's proper load RMS when called upon,.. and the amp will never be worked harder than 80% (theoretically) of it's max capacity of *continuous* power... I'm not going to muddy this up with the "Peak power" figures.

Last question then.

Do most amps have ways to turn them "down" on wattage per channel? Or perhaps per 2 channels at least? Or will I be setting the amp at ONE percentage, and that is that.

If the amp can only be set on one adjustment power wise for ALL channels output.. Would it be in my better interest to drive the amp at 85% and give the Sub 340watts.. and the Fronts 102 watts or drive it a bit higher to give the sub more, but simultaneously pushing more to the Fronts?

Maybe that is a moot question if the typical 4 channel modern mid-range amp has ability to attenuate power per channel.

Thanks for the answers!

 

[So Low iT Hz]

Such a small percentage extra power is nothing to worry about. Thermal power handling is an approximation to begin with, simply based on voice coil wire type, former material, and diameter. Given that more than 99% of power that you apply to a speaker is dissipated as heat, thermal power handling (or cooling) is a very important figure to consider, thermal "over powering" is usually the least of your concerns because, as mentioned earlier with impedance rise on a common setup (**which can be leveled**) you won't be seeing rated rms power like ever.

The way people more commonly blow speakers is because of distortion. The more distortion you introduce, the more unwanted heat dissipation you will have and the less control you have over the movement of the speaker. If you get an amplifier with triple the rated rms power of your speakers, and set the gain to a level that introduces less than .1% distortion, you won't blow the speakers. If you get an amplifier rated half the rated rms of the speaker and you set the gains at 10% THD you are going to blow your speakers. And it'll sound like crap.

Moral of the story, overhead power will not only make your speakers sound better they will be mechanically happy and thermally not worse off than most clipped signals. THD is your enemy. The higher the note, the worse it sounds distorted. On the other side of distortion, the lower the frequency played, the more power is wasted into heat dissipation due to the waveform spending a longer duration at clip. It's hard to explain but you can actually be louder on lower ohm loads with less power but less distortion than on higher ohm loads with more "power" but more distortion. For example, Since sound pressure is logarithmic, for a 10db increase in sound at 10% THD, you have half your volume increase distorted, which means you will inevitably listen to it at a lower volume. Whereas at half the power, you sacrifice 3dB of maximum volume level but with say 3% THD you would end up with several dB more volume before arriving at noticeable distortion levels.

Well anyway don't worry about having extra power. Nuff said //content.invisioncic.com/y282845/emoticons/respekt.gif.b162d148236010609fe523122efe3729.gif

**a zobel impedance correction should be standard in all installations in my opinion, but only seems to be a standard in HT setups. It's too bad I would sacrifice theoretical power handling for linear impedance curves anyday...

 

[So Low iT Hz]

Welcome to 500 level btw //content.invisioncic.com/y282845/emoticons/graduate.gif.d982460be9f153bb54e5d4cb744f6ae8.gif

 

[Chromatic]

Welcome to 500 level btw //content.invisioncic.com/y282845/emoticons/graduate.gif.d982460be9f153bb54e5d4cb744f6ae8.gif

lol.. I followed most of it.. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

But specifically with the setup I'm going to run.. I can leave the gain at 100 percent given the minimal 15-20 percent increase in RMS on the speakers?

My question was do amps have gain adjustments for each channel? Or is it just ONE gain adjustment for all channels.

If for all channels.. Then would I do the math, and equal out the RMS to the max rated RMS for the speakers on the amps gain per channel? Or , would I leave a 15-20% greater RMS gain going to the speakers?

I know 5watts over isn't going to cause issue.. but, on the mids we're talking about 20 watts over on a 100watt rms setup.. and the Sub between 60-100 watts over RMS on a 300-340 watt "max" RMS.

Thanks

 

[Chromatic]

Welcome to 500 level btw //content.invisioncic.com/y282845/emoticons/graduate.gif.d982460be9f153bb54e5d4cb744f6ae8.gif

lol.. I followed most of it.. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

But specifically with the setup I'm going to run.. I can leave the gain at 100 percent given the minimal 15-20 percent increase in RMS on the speakers?

My question was do amps have gain adjustments for each channel? Or is it just ONE gain adjustment for all channels.

If for all channels.. Then would I do the math, and equal out the RMS to the max rated RMS for the speakers on the amps gain per channel? Or , would I leave a 15-20% greater RMS gain going to the speakers?

I know 5watts over isn't going to cause issue.. but, on the mids we're talking about 20 watts over on a 100watt rms setup.. and the Sub between 60-100 watts over RMS on a 300-340 watt "max" RMS.

Thanks

 

[So Low iT Hz]

lol.. I followed most of it.. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
But specifically with the setup I'm going to run.. I can leave the gain at 100 percent given the minimal 15-20 percent increase in RMS on the speakers?

My question was do amps have gain adjustments for each channel? Or is it just ONE gain adjustment for all channels.

If for all channels.. Then would I do the math, and equal out the RMS to the max rated RMS for the speakers on the amps gain per channel? Or , would I leave a 15-20% greater RMS gain going to the speakers?

I know 5watts over isn't going to cause issue.. but, on the mids we're talking about 20 watts over on a 100watt rms setup.. and the Sub between 60-100 watts over RMS on a 300-340 watt "max" RMS.

Thanks

One gain per stereo input. And you NEVER want the gain at 100%. You need to be able to set your gains to less than 1% THD to maximize sound and volume. Don't worry about power levels. Each amplifier will only make so much power with a given supply, so you just want to make sure that no matter what amplifier you choose you set it up properly. O scopes or something like the DD-1 comes in very handy for that.

You can do it with a DMM measuring the voltage rails but you can't tell if you've reached maximum voltage with wicked ugly peak shapes.

 

[Chromatic]

One gain per stereo input. And you NEVER want the gain at 100%. You need to be able to set your gains to less than 1% THD to maximize sound and volume. Don't worry about power levels. Each amplifier will only make so much power with a given supply, so you just want to make sure that no matter what amplifier you choose you set it up properly. O scopes or something like the DD-1 comes in very handy for that.
You can do it with a DMM measuring the voltage rails but you can't tell if you've reached maximum voltage with wicked ugly peak shapes.

Sounds like I need something to measure amplitude as I increase "volume" .. or gain, etc. That's way more than most installers will ever do.. people use the ear test lol.

Hrmm.. anyhow,.. the amp I am going to get shows the gain for channel 1 and 2, then a gain for channel 3 and 4. I was going to use channel 1 and 2 for the fronts, and channel 3 and 4 bridged to rear. So looks like those two gains would effectively be for the fronts and the sub as I need.

So never throw the gain at 100 percent eh? Just barely under sound right? Or do I want to buy WAY more head room than the speakers need and set at some half value or some such?

This amp is priced in the $250 range.. and thus in my price range. I think If I run the amp at about 90% on each channel it would be a good 'compromise' between both equations here.

At 90% it would still run 108watts RMS for the 100w rated fronts, and 360watts RMS for the 350watt rated rears. Sounds good to me. (Man, so many puns on this forum).

I'm pretty close to 'Good to GO' .. for ordering.. just wanted to work out installation.. cause if I'm going to actually tackle running wires through impossibly small spaces , then I'll need to buy a good single 4 chan amp , front components, and sub setup kit.

I little off topic,.. but wiring wise -- You know my setup.. I'll post it in case you don't:

Doors/Front Speaker/Stage = CDT CL-61-CV 6.5" Mids with the .75" Tweeters going in the Window Sail panels (Both are factory size, and will replace factory speakers directly.) -- The high mounted tweeters should bring up the sound stage well. Speakers are 100 Watts RMS a piece. $180

Cl-61cv - CDT Audio 6.5" Convertible Coaxial Component Speaker System | WoofersEtc

Head Unit = Pioneer AVH-P4100DVD AVH-P4100DVD - In-Dash Double-DIN DVD Multimedia AV Receiver with 7" Widescreen Display | Pioneer Electronics USA (Already installed).

Sub box = Custom Built box that fits exactly in the Factory slot where the Factory sub would go.

$100

Nissan 350z Vehicle Specific Sub Enclosure 1-10"

Sub = JL Audio 10w0 (75-300 Watts RMS) JL's "optimal" range on their website is around 220-250 watts RMS. $110

The alternative here is an 8 Inch Sub.

This brings back the 8 or 10" argument. Money is going to be $100-$130 on sub regardless of which size. So if that budget on sub helps you give me a reason to go with one size over the other.. please do.

JL Audio 10W0v3-4 W0v3 Series 10" 4-ohm subwoofer at Crutchfield.com

Amp: CT Sounds - 4 Channel, 125watt RMS x 2 (for 100watt fronts).. and 380watts RMS (Bridged and stable at 4 ohms) for Sub. $225

Ct Sounds 125 4 Amp Amplifier 125W RMS 250W Max Class A B 4 Channel 2 Ohm | eBay

Given I have Headunit already -- that's the whole deal.

There it is,.. simple, 2 3/4" tweeters, two 6.5" mids, one 10inch JLw0 sub (In custom 350z enclosure).. one amp, one Pioneer headunit.

If I go about this on my own,.. first time complete system install and tearing interior of car apart -- What's a good wiring setup, with a good fuse kit and essentially everything I'd need to wire the aforementioned up and have it running?

I like large gauge wire, but I've thought about it,.. and I don't want to go any larger than I *should* for the amperage/speaker SQ to make the install any more difficult than is necessary. I'd imagine running 8 gauge wire is ALOT easier than 0 gauge.. maybe there is no difference, I dunno.

Thanks

 

[Frenchy906]

If it were me, I'd run 4 gauge wire.

I'm in the same boat right now, my amp calls for 8 gauge so thats what I ran, then when I checked out current draw / etc on the12volt.com I realized that my amp is going to draw more current than 8 gauge can handle.

 

[Chromatic]

Frenchy,.. Yeah .. I was thinking 4 Gauge as well.. at least from the Battery to Amp. From head unit to amp -- Do we use RCA outputs (I thought maybe so due to the 4v pre-outs) ? Or speaker wire? I know from amp to speakers it's speaker wire. What gauge is good but not overly hard to install speaker wire wise running from amp to speakers?

 

[So Low iT Hz]

Sounds like I need something to measure amplitude as I increase "volume" .. or gain, etc. That's way more than most installers will ever do.. people use the ear test lol.Yea unfortunately there are no pre requisites to become an "installer" in this industry. These DIY heroes turned "pros" give the rest of the talented installers out there a bad name.

Hrmm.. anyhow,.. the amp I am going to get shows the gain for channel 1 and 2, then a gain for channel 3 and 4. I was going to use channel 1 and 2 for the fronts, and channel 3 and 4 bridged to rear. So looks like those two gains would effectively be for the fronts and the sub as I need.

Yep. Two gains for a four channel amp.

So never throw the gain at 100 percent eh? Just barely under sound right? Or do I want to buy WAY more head room than the speakers need and set at some half value or some such?

The gain is only supposed to be set to one position. That is where the output rails line up with the input voltage rails. You can test it with a DMM if you read AC voltage out while playing a 0 or -3db sine wave and increase the gain until the voltage doesn't increase anymore. Then you know you're in the ballpark.

this video should help