108 DB with a Single 10 sub?

Home / the12volt's Install Bay / Car Audio / 108 DB with a Single 10 sub? (

Topic Closed)

Welcome Guest :)

Members

Next Page > < Prev Topic Next Topic >

mrmsudawgs

Copper - Posts: 145

Joined: February 22, 2005

Location: United States

Posted: July 13, 2005 at 11:25 PM / IP Logged

I just used a hand held meter, a test tone CD, and an SPL VS HZ chart that I printed from Polk's sub performance page for my Polk MM2104 10 inch sub as seen here

in an attempt to see how my system would perform. When I built my sealed enclosure I assumed that my sub would perform as indicated in Polk's DB vs HZ chart. According to that chart, the sub should hit a max of 85 DB at 50 HZ. My test showed 105 DB at 50 HZ and a max of 108 DB at 60 HZ. My graph that I made looks nothing like the graph on Polk's page and their graph is for the same sub I am using as measured inside a car (actual performance data).

With all that said, here are my questions:

(1) Does 108 DB for a single 10" sub sound correct?

(2) Can I attribute this differnce to a better in car gain in my vehicle?

(3) I have no idea what volume level was used in the test performed by Polk. I just turned mine to about "14" which was loud without distortion and performed my test at that volume level. Is this the correct method?

Any advice will be appreciated.

Mike

2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

stevdart

Platinum - Posts: 5,816

This member has made a donation to the12volt.com. Click here for more info.

This member has been recognized as an authority in Mobile Audio and Video. Click here for more info.

This member consistently provides reliable information

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: July 13, 2005 at 11:49 PM / IP Logged

They used 1 volt for the measurement, as you can read at the bottom of the linked page. Their testing is done as a standard of measurement that they use for several drivers and the comparisons should be used amongst those drivers tested in that manner. Any test you perform will show different results.

Otherwise, a woofer with a reference efficiency of 87 db at 1 watt would reach 108 db with only 128 watts applied. And that doesn't consider the additional db's from cabin gain.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

mrmsudawgs

Copper - Posts: 145

Joined: February 22, 2005

Location: United States

Posted: July 14, 2005 at 8:27 AM / IP Logged

1 volt? So let me get this straight - the performance curve that they show is the results of a sub hooked to 1 volts with a sinusoidal tone? I wonder why they did not use 12 volts or even 14 volts? I took their data to be an actual in car performance in which I assumed that they are pusing the sub to its limits in order to get the highest SPL. Why would they publish data that seems "weak" in comparision to real world scenarios?

2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

jstruckman

Copper - Posts: 465

Joined: May 03, 2004

Posted: July 14, 2005 at 9:26 AM / IP Logged

Those specs they use are to show the effiiciency of the sub, not how much SPL it will produce. This is the standard for subwoofer efficiency ratings.

Jazzy

mrmsudawgs

Copper - Posts: 145

Joined: February 22, 2005

Location: United States

Posted: July 14, 2005 at 11:10 AM / IP Logged

Well, that makes since then.

Alright - then answer this, does 108 DB seem good/bad/great for a single 10" sub?

2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

stevdart

Platinum - Posts: 5,816

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: July 14, 2005 at 5:35 PM / IP Logged

stevdart wrote:

Otherwise, a woofer with a reference efficiency of 87 db at 1 watt would reach 108 db with only 128 watts applied. And that doesn't consider the additional db's from cabin gain.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

mrmsudawgs

Copper - Posts: 145

Joined: February 22, 2005

Location: United States

Posted: July 14, 2005 at 6:32 PM / IP Logged

Don't you mean 87 DB at 1 "Volt" instead of 1 Watt? The graph is in volts not watts. Am I missing the point?

2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

stevdart

Platinum - Posts: 5,816

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: July 14, 2005 at 8:58 PM / IP Logged

Yeah. You asked, "does 108 DB seem good/bad/great for a single 10" sub?" I said earlier, and then again quoted, that a sub with an (average) efficiency of 87 will only take 128 watts to reach 108 db's. That's anechoic...no additional db's from cabin gain included. That's just doubling power for each 3 db's.

Too answer you question more bluntly..."bad"...with it being at '14' and all.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

mrmsudawgs

Copper - Posts: 145

Joined: February 22, 2005

Location: United States

Posted: July 14, 2005 at 9:55 PM / IP Logged

I believe my volume goes up to 25 on my Alpine CDA-9831. I've had it up to "21" which was really loud. I used "14" because it just sounded about right.

Can you help me with the math >> How did you determine that 128 watts yields 108 DBs?

Thanks,

Mike

2000 F150 Supercab Lariat, Alpine CDA-9831, Polk MMC570 in Doors, One Polk MM2104 Sub, One Polk Carbon C400.4 Amp.

John 3:16

stevdart

Platinum - Posts: 5,816

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: July 14, 2005 at 10:32 PM / IP Logged

With a reference of 1 watt / meter, the sub's (in my example) rated efficient is 87 db. (Some references use 2.83 volts, and some use 1 watt. The reference you posted used 1 volt.) But to compare apples with apples we'll use the common watt. The sub will play 87 db loud with 1 watt of applied power.

The rule of adding 3 decibels for every doubling of the power is really a simplified form of a logarithmic equation (I quoted it in a post here) but I understand the simplified method much better. If you start with 87 db's with 1 watt, then 2 watts will yield 90...4 is 93...8 is 96...16 is 99...32 is 102...64 is 105...and 128 watts will yield 108 decibels.

(I used 87 db as the reference efficiency of this example because you asked about 108 decibels and the numbers come out right. If I'd used a sub rated 86 db, or 89, or any other number, I wouldn't have arrived on 108 db's for this illustration.)

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Next Page >

Printable version

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Search the12volt.com

Follow the12volt.com

Disclaimer: *All information on this site ( the12volt.com ) is provided "as is" without any warranty of any kind, either expressed or implied, including but not limited to fitness for a particular use. Any user assumes the entire risk as to the accuracy and use of this information. Please verify all wire colors and diagrams before applying any information.