straighten me out on rms, or what sub can handle

[axeshredder 10+ year member]

I know rms is based on continuous listening, but what is peak? I mean, is a "peak" when a particular bass note in song hits extra hard? If you have an amp running 750 into and 800 watt sub, how does the "sub level" on head unit factor in? If gain on said amp is 2/3, and you have a sub level value of 0-15, does that mean sub can be run at 15? The various factors are confusing at best.

Click to read more...

 

[JL Audio 5,000+ posts]

gain is not a volume knob, 2/3 is not a correct reading for setting one, I don't like where this is going. have you tried looking up a general amp setting guide on this site? I think it's in the general or amplifier section at the top in stickies.

 

[axeshredder 10+ year member]

gain is not a volume knob, 2/3 is not a correct reading for setting one, I don't like where this is going. have you tried looking up a general amp setting guide on this site? I think it's in the general or amplifier section at the top in stickies.

I know gain is not volume knob. I'm not a total noob. lol. I know setting gain is ideally done with o scope, but gain IS amount a power being sent to sub or subs. just don't get how head unit, or sub level on head unit factors in, and what is "peak"? really hard part of song? or.............?

 

[keep_hope_alive Premium Member]

depends on the HU.

Alpine, for example, has a sub level adjustment from 0-15. but it's actually just attenuation below 15. so to get the full possible pre-out signal to the amp, you have the level at 15. when setting gains, 10 is a useful place so you have some head room depending on the recording.

gain on an amp is just input sensitivity. you tell the amp what the incoming voltage is. it boosts the incoming voltage then applies a fixed amount of amplification.

the old "2/3 hu volume" rule of thumb was mostly to prevent any clipping out of the head unit preouts. some head units are clean to full volume, some are not. Alpine, for another example, has a clean output to full volume on some of it's head units, but not all. you won't konw if your HU is or is not clean at full volume without a trained ear or an o-scope.

your head unit volume adjust the voltage level being sent to the amp. by adjusting gain, you adjust what incoming voltage is required for the amp to make rated power output. peak is not a useful metric in any way. when we set gains, we use test tones that are at a maximum recorded level (-0dB) so we ensure we will not clip at musical peaks.

 

[Julian 10+ year member]

Peak is a useless spec to look at, it's usually boasted to make the product look better. Most people don't realize there are many determining factors to how much power a subwoofer can take. You have mechanical and thermal.. it all depends on your goals and enclosure.

Edit: Just noticed you were from OP, I'm from KCMO myself.

 

[quackhead 10+ year member]

I know rms is based on continuous listening, but what is peak? I mean, is a "peak" when a particular bass note in song hits extra hard? If you have an amp running 750 into and 800 watt sub, how does the "sub level" on head unit factor in? If gain on said amp is 2/3, and you have a sub level value of 0-15, does that mean sub can be run at 15? The various factors are confusing at best.

this is referred to as "Peak Transient".

Peak Power to some means nothing and is ridiculed....due to the fact that some less reputable manufacturers have derived this measurement from a matter of milliseconds exposure...lol. To someone knowledgeable of a manufacturer who uses a more realistic measurement of peak power, it is very telling..almost a necessity.

When I buy a sub from a reputable Mfg., I want to know the rms and the peak ratings. When choosing an amp from a reputable Mfg, I look to match the RMS output to an estimation between the sub's rms rating and peak power rating....some of the more reputable mfg call this a "Continuous", or "Program" rating:

Example: 1000w rms/2000w Program/3000w Peak

say I run a 2000w rms amp on the sub i just spec'd....the 1000w over rms is referred to as Headroom...Headroom to allow for the slap of a low B on a bass guitar in time with the pound of a double bass drum that overshadows the rhythm guitarist....I will have enough power on tap to reproduce this sound without distortion or clipping.

Some amps have this headroom ability built in and is usually desired due to the "does more than rated" factor.

some amp mfg show this in their specs and some don't

 

[keep_hope_alive Premium Member]

also note that amplifier ratings are taken at a certain amont of THD. the "underrated" amps just rate at a lower THD than is tolerable. with any amp, THD increase exponentially with power output. at some point, it becomes audible and undesireable.

here is a good example:

here is a 4 channel, 49W per channel rated amplifier - the size of your thumbnail. granted, you need some other connectors, caps, resistors, etc. to interface with this, but this is what does amplification in some OEM "premium" amplifiers.

TB2946HQ datasheet, Pinout ,application circuits 49 W × 4-ch BTL Audio Power IC

TB2946HQ datasheet, Pinout ,application circuits 49 W × 4-ch BTL Audio Power IC

Specs:

• POUT MAX (1) = 49 W (typ.)

(VCC = 15.2 V, f = 1 kHz, JEITA max, RL = 4 Ω)

• POUT MAX (2) = 43 W (typ.)

(VCC = 14.4 V, f = 1 kHz, JEITA max, RL = 4 Ω)

• : POUT MAX (3) = 70 W (typ.)

(VCC = 14.4 V, f = 1 kHz, JEITA max, RL = 2 Ω)

• POUT (1) = 26 W (typ.)

(VCC = 14.4 V, f = 1 kHz, THD = 10%, RL = 4 Ω)

• POUT (2) = 23 W (typ.)

(VCC = 13.2 V, f = 1 kHz, THD = 10%, RL = 4 Ω)

• Low THD: 0.007% (typ.) (VCC = 13.2 V, f = 1 kHz, POUT = 5 W, RL = 4 Ω)

You can see they rate THD at 5W and 4ohm (to get a low number). But they publish 13.2VDC RMS power at 23W at 10% THD.

this is VERY common with amplifiers. Publish THD and RMS power using two completely different tests. A good amp will state THD at each power rating, adn their rated power will have THD less than 1%. Amplifiers with RMS power rated at .1% THD or less are what we call "underrated" amps. Because they make more power at higher THD, while still being listenable.

 

[hispls 5,000+ posts]

Various brands rate their equipment differently, some honestly, some are full of ****. I'll leave out explaining what RMS means here, sufficed to say we don't call a wall outlet 115V RMS 160 PEAK.

Really if you have to ask you should deal only with continuous power ratings, and ideally with reputable companies.

 

[keep_hope_alive Premium Member]

I'll leave out explaining what RMS means here, sufficed to say we don't call a wall outlet 115V RMS 160 PEAK.

EE's refer to them as 120V, not 115V or 110V. While NEC allows for 5% drop at any outlet, proper design, wire size, and transformer taps can get you a solid ~120V anywhere regardless of the building size.

RMS * SQRT(2) = Peak

 

[hispls 5,000+ posts]

RMS * SQRT(2) = Peak

Please explain what this means and how it is relevent to the question.

 

[quackhead 10+ year member]

lol

 

[keep_hope_alive Premium Member]

Please explain what this means and how it is relevent to the question.

it's relevant, not relevent.

the first question asked was:

I know rms is based on continuous listening, but what is peak?

the relationship between peak and RMS is purely mathematical.

 

[hispls 5,000+ posts]

it's relevant, not relevent.
the first question asked was:

the relationship between peak and RMS is purely mathematical.

So you feel that manufacturers "peak" power ratings have something to do with the actual peaks of the sine wave or that their continuous power rating is some mathematical function of that?

 

[keep_hope_alive Premium Member]

Nope. We know that mfr's use tricks. I don't consider those useful numbers. Thereis no equation for RMS power and Peak power ratings for amplifiers.

that formula applies to voltage. Which we digressed on when discussing residential voltages.

I apologize for any confusion.

 

[quackhead 10+ year member]

Nope. We know that mfr's use tricks. I don't consider those useful numbers. Thereis no equation for RMS power and Peak power ratings for amplifiers.
that formula applies to voltage. Which we digressed on when discussing residential voltages.

I apologize for any confusion.

yeah, nowdays, it is not as easy to discern who is "reputable" and who is not...it seems like in the last decade or so, the manufacturers have leaned more to the love of money than the love of sound.