# Sensitivity and Watt's Question

## Recommended Posts

I am thinking I am going to get a new HU and speakers and wait on the amp. Would I want to get as high of a sensitivity as possible if the HU only puts out 22 watts rms and not care about the watts as long as it is in the operating range of the speaker since sensitivity is the dB's at 1 watt and 1 meter and goes up by 3 dB every time the watts are doubled. Wouldn't that mean the highest sensitivity speaker would be the loudest at 22 watts rms even if one speaker 90 dB and 45 watts rms and another is 93 dB 100 watts rms the 100 watt speaker would be louder. Am I right or do have this all confused?

Edited by Joel114
Changed 1 dB every time the watts are doubled to 3

##### Share on other sites

Hi! Actually, output goes up by 3dB for every doubling of power.

Sensitivity is one factor that you can use to evaluate speaker choices, but it's not the only factor.  Some aspects of speaker design that improve sensitivity may sound worse.  One difference between a dust cap and a phase plug is that the dust cap adds output (increases the sensitivity rating) but usually does so at the sacrifice of frequency response in the upper octaves.

In general, your thinking is correct that having a speaker system with higher sensitivity will be louder on a head unit.  You can only plan on 5W being usable out of a head unit, all channels driven.  Beyond that distortion becomes audible, and quickly.  You should still be able to achieve a 93-95dBA output level which is plenty for HU power.

So, assume you find a speaker system with 90dB 1W & 1M and you give it 4 clean watts of power - you can expect 96dB 4W @ 1M.  In a car, you sit about 1 meter away from a speaker and about 2 meters from the rest.  Overall output would be the logarithmic sum of all four speakers, getting you close to 100dBA of possible output - theoretically assuming no cancellation occurring.

My recommendation for piecing a system together is to buy what you want at the end, in steps.  Sacrificing now and getting something cheaper isn't saving money if you plan on buying the better version later.  Saving up for the good item is worth the wait (or finding it used for a fraction of the cost).

• 1

2014 Accord Sport build log:

My 1966 MGB Restoration: http://www.mgexp.com/journal/keephopealive

##### Share on other sites
1 minute ago, keep_hope_alive said:

Hi! Actually, output goes up by 3dB for every doubling of power.

Sensitivity is one factor that you can use to evaluate speaker choices, but it's not the only factor.  Some aspects of speaker design that improve sensitivity may sound worse.  One difference between a dust cap and a phase plug is that the dust cap adds output (increases the sensitivity rating) but usually does so at the sacrifice of frequency response in the upper octaves.

In general, your thinking is correct that having a speaker system with higher sensitivity will be louder on a head unit.  You can only plan on 5W being usable out of a head unit, all channels driven.  Beyond that distortion becomes audible, and quickly.  You should still be able to achieve a 93-95dBA output level which is plenty for HU power.

So, assume you find a speaker system with 90dB 1W & 1M and you give it 4 clean watts of power - you can expect 96dB 4W @ 1M.  In a car, you sit about 1 meter away from a speaker and about 2 meters from the rest.  Overall output would be the logarithmic sum of all four speakers, getting you close to 100dBA of possible output - theoretically assuming no cancellation occurring.

My recommendation for piecing a system together is to buy what you want at the end, in steps.  Sacrificing now and getting something cheaper isn't saving money if you plan on buying the better version later.  Saving up for the good item is worth the wait (or finding it used for a fraction of the cost).

Ya I ment 3dB. Also the HU is 4x 22 rms, I should have specified that sorry. Ya I plan on just getting the speakers and head unit I want and waiting on a sub and amp. Thank you

##### Share on other sites
7 minutes ago, keep_hope_alive said:

Hi! Actually, output goes up by 3dB for every doubling of power.

Sensitivity is one factor that you can use to evaluate speaker choices, but it's not the only factor.  Some aspects of speaker design that improve sensitivity may sound worse.  One difference between a dust cap and a phase plug is that the dust cap adds output (increases the sensitivity rating) but usually does so at the sacrifice of frequency response in the upper octaves.

In general, your thinking is correct that having a speaker system with higher sensitivity will be louder on a head unit.  You can only plan on 5W being usable out of a head unit, all channels driven.  Beyond that distortion becomes audible, and quickly.  You should still be able to achieve a 93-95dBA output level which is plenty for HU power.

So, assume you find a speaker system with 90dB 1W & 1M and you give it 4 clean watts of power - you can expect 96dB 4W @ 1M.  In a car, you sit about 1 meter away from a speaker and about 2 meters from the rest.  Overall output would be the logarithmic sum of all four speakers, getting you close to 100dBA of possible output - theoretically assuming no cancellation occurring.

My recommendation for piecing a system together is to buy what you want at the end, in steps.  Sacrificing now and getting something cheaper isn't saving money if you plan on buying the better version later.  Saving up for the good item is worth the wait (or finding it used for a fraction of the cost).

Also what speaker brand would you recommend for a 6.5" and 6x9? What do you think about polk they seem nice and have a high sensitivity.

Edited by Joel114

##### Share on other sites

Hi, I know you said 22W but i should have clarified that you can expect the first 5W to be usable, listenable.  Beyond 5W distortion becomes audible and at 10W it will sound poor and at 22W it will be un-listenable and likely not possible.   This relates to how these amplifier IC's are rated.  Note that the amplifier IC itself is contained on a single chip the size of a quarter and it does all of the amplification for all 4 channels.  This amplification is the result of the outputs being bridged (so think of it as an 8 channel amp bridged to 4 channels).  But the IC has power leads the size of a thin lead which could in no way handle 88W of output power (since input power is output power + efficiency losses (heat).  Instead, a manufacturer can rate an amp 22Wx4 if only one channel can produce 22W for one second.  It is misleading, I know, but that's how the industry has been for years (home receivers are notorious for this - note the UL Listed max power draw of a receiver - such as 100Wx7 with a max draw of only 325W).    Typically, you can assume about 25% of an IC amplifier chip being usable.

Long story short, expect you'll only want to listen to 5W per channel of a head unit.

JBL, Polk, Hertz, JL Audio, Alpine - all have viable options in those sizes - even if they are entry-level models.   My personal favorite for coaxial 6.5 and 6x9 combos is the Hertz High Energy (now the Mille Pro).  But those come at a steep price.   Keep in mind you'll want to consider wiring up front components so the tweeters are pointed at your face - that will greatly improve sensitivity since door speakers are pointed at your ankles.

Edited by keep_hope_alive
• 1

2014 Accord Sport build log:

My 1966 MGB Restoration: http://www.mgexp.com/journal/keephopealive

##### Share on other sites
3 hours ago, Joel114 said:

I am thinking I am going to get a new HU and speakers and wait on the amp. Would I want to get as high of a sensitivity as possible if the HU only puts out 22 watts rms and not care about the watts as long as it is in the operating range of the speaker since sensitivity is the dB's at 1 watt and 1 meter and goes up by 3 dB every time the watts are doubled. Wouldn't that mean the highest sensitivity speaker would be the loudest at 22 watts rms even if one speaker 90 dB and 45 watts rms and another is 93 dB 100 watts rms the 100 watt speaker would be louder. Am I right or do have this all confused?

another thing to consider is the headunit make sure it has a hp xover that will make speakers sound much better and have less to no distortion.. i run my speakers off hu and sounds pretty good with xover set at 100hz so they make no bass of course i have a sub.. if u don't have a sub at least u can set xover at like 70hz to keep speakers cleaner and make them last longer.. kenwood x302 i think is new model like mine it has time alignment, 13 band eq 4v preouts, bt, usb and 24 bit da convertor (which helps alot making speakers louder) and it's cheap.. i have sound qubed coax and with a xover they pretty good but i would say look at the infinitys, jbl (basically the same speaker) and polk even pioneer like u said look for db rating 91 or higher https://www.amazon.com/Infinity-PR6500CS-Primus-Component-Speaker/dp/B00IFAX38S/ref=sr_1_4?ie=UTF8&amp;qid=1538982017&amp;sr=8-4&amp;keywords=ALPINE+SXE-1750S  https://www.amazon.com/Polk-Audio-DB651-Certified-Speakers/dp/B000P0PF9G/ref=sr_1_3?ie=UTF8&amp;qid=1539326269&amp;sr=8-3&amp;keywords=polk+6.5"

KENWOOD X301 HU, PRECISION POWER Phantom 1000, FU 750 12, 2.1cfad ported, soundqubed 6.5" coax/doors, hp & lp xover on hu, AGM starting batt...

Boomin_tahoe said:
2 ohms rule

##### Share on other sites

KENWOOD X301 HU, PRECISION POWER Phantom 1000, FU 750 12, 2.1cfad ported, soundqubed 6.5" coax/doors, hp & lp xover on hu, AGM starting batt...

Boomin_tahoe said:
2 ohms rule

##### Share on other sites
12 hours ago, Joel114 said:

Wouldn't that mean the highest sensitiv﻿ity speaker would be the loudest at 22 watts rms even if one speaker 90 dB and 45 watts rms and another is 93 dB 100 watts rms the 100 watt speaker would be louder.

Sort of, keep in mind that "sensitivity" is calculated and not measured though and this may or may not be honest.  The other side of that coin from a design standpoint is the very efficient speakers are always limited in power handling.  Everything we do to make them handle more power robs efficiency.   It's always a compromise.

For what it's worth I have always liked the JBL/Infininty product line on lower power.   JBL has some beefier options for higher power, not so sure about Infinity.   Polk sold out manufacturing very early 90s and I haven't liked them much since.   They may be decent but it's one of those where they just became a shadow of their former greatness in my mind.

Really if you stay out of the gutter brands you should be OK but component/coaxial speaker sound is very subjective.  You'd do best to try to go to some brick and mortar stores to audition them in person.

## Create an account

Sign up for a new account in our community. It's free & easy!

Register a new account