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adding one more sub, noticeable difference?


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stevdart 
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Joined: January 24, 2004
Location: Pennsylvania, United States
Posted: April 03, 2007 at 4:26 AM / IP Logged  

sedate wrote:
And doubling it in the end, I think, would *then* give us +9db.

custom audio ny wrote:
The reason I say "in theory" as discussed earlier there are other factors..well many factors that effect output such as car environment, accuracies of ratings, performance of products and a host of others.

This is truly just a theory question, so answers are rightly subjective.

The added part about "doubling the power AGAIN" confuses the issue and shouldn't be included in discussion.  We should presume a maximumly powered subwoofer to begin with, as the question posed is about how to get more SPL.

So yes, doubling of cone area (when you are starting with one woofer you need only add one identical woofer) nets +3 db due to increase in sensitivity.  Given another identical amp, the power to the sub system is doubled so the sub's output is 3 db higher than it was before.  Net gain of +6 db.  Then there is added cabin gain...  The overall output could actually well exceed +6 db gain as long as  ALL NECESSARY IMPROVEMENTS AND ADDITIONS to the car (that are necessarily required by the upgrade in equipment) are added.  This may mean that alternator, battery and system wiring needs to be upgraded, for example.  And that the sheet metal damping is multiplied in critical areas.  As long as you don't begin to experience a higher loss ratio because of excessive sheet metal vibration, or that the amplifiers are now starving because of the power-hungry addition, you can look at achieving a very noticeable SPL improvement by doubling your subwoofer system.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
haemphyst 
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Posted: April 03, 2007 at 8:15 AM / IP Logged  
In an anechoic chamber, doubling the cone area, while at the same time maintaining the same amount of power to the system, will net NOTHING
i.e. 100 watts to one speaker vs. 50 watts to EACH of two speakers = no net increase or decrease in output, or ±0dB
In an anechoic chamber, maintaining the cone area, while at the same time doubling the amount of power to the cone, will net a +3dB increase in output
i.e. 100 watts to one speaker vs. 200 watts to the same speaker = +3dB
In an anechoic chamber, doubling the cone area, while at the same time doubling the power to the system will net a +3dB increase in output
i.e. 100 watts to one speaker vs. 100 watts to EACH of two speakers = +3dB
(This, if I read correctly, is the situation our poster is in. To realize a 6dB gain, he would have to double this scenario... Meaning 4 woofers total, WITH 2 amplifiers.)
In an anechoic chamber, doubling the cone area, while at the same time doubling the power to each cone will net a +6dB increase in output
i.e. 100 watts to one speaker vs. 200 watts to EACH of two speakers = +6dB
So, using these formulae, adding one more 12", with an identical amplifier, he will realize an expensive +3dB increase in output. It sounds to me like he is interested in SPL, not SQ, so if this is the case, and if the amp can handle the load, just add ONE WOOFER, parallel them, and load the amp to it's maximum. This will give you (roughly - possibly SLIGHTLY less, but CERTAINLY not enough to notice by ear.) the same output increase, without the additional cost of an amplifier.
Unless he is doubling the load on each respective amplifier to double the power output of each respective amplifier (which he isn't), he will realize a 3dB gain, either way he goes. NOT adding the additional amplifier will be the less expensive way to go, though... Am I right?
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
sedate 
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Posted: April 03, 2007 at 10:16 AM / IP Logged  

heamphyst wrote:
Am I right?

Strangely enough, no, you do not appear to be.

As I believe I correctly stated in my second post here, if he adds one more 12 and another amplifier of equivalent output, he will net +6db.

Yellow = 1x12" @ 1w/1m

Red = 2x12" @ 1w/1m

Blue = 2x12" @ 2w/1m <-- +6db Gain

Green = 2x12" @ 4w/1m

adding one more sub, noticeable difference? - Page 2 -- posted image.

"I'm finished!" - Daniel Plainview
haemphyst 
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Posted: April 03, 2007 at 1:08 PM / IP Logged  
The blue curve indicates a TOTAL POWER of 4 watts - TWICE the power, AND twice the cone area. It says so, right there:
sedate wrote:

Blue = 2x12" @ 2w/1m <-- +6db Gain

2X2=4, reference output X 4 = +6dB. It is showing a total dissipation of 4 watts. 2 watts PER WOOFER, at one meter. The red line is what you need to be looking at, if adding one more identical subwoofer system. IF adding another subwoofer (i.e. 2 times the cone area, which is +3dB) AND doubling the power (another +3dB) into both subs, THEN you can add 6.
1watt/1woofer = 1 watt dissipated = reference
2watts/1woofer = 2 watts dissipated = reference +3
2 watts/2 woofers = 4 watts dissipated = reference +6
4 watts/2 woofers = 8 watts dissipated = reference +9
Do you see the progression? Twice the power (per woofer) affords twice the output (+3dB) The next step would be:
8 watts/2 woofers = 16 watts dissipated = reference +12
So, I still stand on my calculations of earlier. (Nice try though... ROFL ...and PLEASE take that in the intended spirit!!!)
(BTW, I like the title of your graphic... "gaindebate" adding one more sub, noticeable difference? - Page 2 -- posted image. adding one more sub, noticeable difference? - Page 2 -- posted image. adding one more sub, noticeable difference? - Page 2 -- posted image. adding one more sub, noticeable difference? - Page 2 -- posted image. adding one more sub, noticeable difference? - Page 2 -- posted image. 5 Stars!)
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
stevdart 
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Posted: April 03, 2007 at 3:54 PM / IP Logged  

haemphyst, Unibox confirms what sedate is demonstrating.  The nominal power as shown in Unibox is power to an individual driver.  The circled area on the right of the screen shows number of drivers.  SPL is shown circled in the center.

A single sub with 150 watts, yielding 111 db:

single_sub_150w_total.jpg

Now, two subs but each only have 75 watts for a total of 150 watts, yielding an increase of 3 db:

double_sub_150w_total_75w_each.jpg

This is the single sub with double the power, yielding a 3 db increase:

single_sub_300w_total.jpg

Unibox demonstrates that either doubling cone area or doubling power yields +3db.  This last pic shows both, for an increase of +6 db, which is what the OP said he wants to do by doubling cone area and doubling total power:

double_sub_300w_total_150w_each.jpg

And so I shall stand as well (although I must admit, tenuously, as DYohn also has told me what you have stated ;)

(Expand the images and flip back and forth through them.  It looks like a decisive conclusion to me.)

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
custom audio ny 
Copper - Posts: 176
Copper spacespace
Joined: March 11, 2007
Location: United States
Posted: April 03, 2007 at 4:23 PM / IP Logged  

So....aside from the predictibility of an anechoic chamber and the unpredictibility of a mobile environment lets look back at the original posted question and possible scenerios.

The author is basically asking if he will gain an improvement in bass output if he adds an identical sub/amp to the existing. Well with twice the cone area and twice the "total" power alone of course there will be a noticible gain assuming all is installed/wired properly (we can't really predict how body panel flex and resonance will effect anything until it is operating, then fixing that if it is causing a negative result is another issue).

Now as far as any other way to approach this we would need to know the voice coil impedance..if the subs are DVC or SCV(to determine final ohms load) ,max power handling and what ohm load the amplifiers are stable down to as well as thier max power output. Since I personally am not familiar with the specific equipment, if the specs are posted we can possibly suggest alternate ways to increase output without damaging any equipment.

If in the case as haemphyst stated the amp he already has can handle the additional sub wired in parallel, and the amp is capable of putting out twice the power if wired that way...he then will have twice the cone area and twice the power as well..surly a more economical way to go. If (and this is all conjecture for now) he gets the other amp and the woofers are DVC there may be a way to achieve 4 times the power.............."in theory"  lol 

BTW, I must say I am very impressed with some of the infomative people on this site. You guys really know your stuff..good going and thanks for sharing. I will be contributing as much as I can when I have the time and hope to learn plenty as well. Also a donation from us will be coming soon. Thanks

Custom Audio
Lynbrook NY
ASE/MECP master certified
sedate 
Silver - Posts: 1,173
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Posted: April 03, 2007 at 4:40 PM / IP Logged  

Okay first of all, can we do something about this 30k image limit?

Anywho, uhh...  well heamph I still believe I'm correcct.

The blue line does not represent 4 watts, it represents 2.  

It says so right in the little box I used to make WinISD make the graph.  Each of these lines represents a 12w6 with 1 cft of air space assigned to it, with the wattage I listed.  I believe this is for the input power for the box, not the individual drivers.

http://linearteam.proboards12.com/index.cgi?board=winisd&action=display&thread=1154421440

Here is the graph before I cropped it for upload earlier. 

adding one more sub, noticeable difference? - Page 2 -- posted image.

"I'm finished!" - Daniel Plainview
haemphyst 
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Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: April 03, 2007 at 4:42 PM / IP Logged  
stevdart wrote:

haemphyst, Unibox confirms what sedate is demonstrating.

A single sub with 150 watts, yielding 111 db:

single_sub_150w_total.jpg

Sure... OK. I'll buy that. No conflict or issues with that so far.
stevdart wrote:

Now, two subs but each only have 75 watts for a total of 150 watts, yielding an increase of 3 db:

double_sub_150w_total_75w_each.jpg

HERE'S where the problem arises, and I think this is where we are not seeing eye-to-eye. Let's just imagine for one second, that you DIDN'T have two woofers, but only fed 75 watts to ONE woofer, rather than two drivers with 75 watts. Are you telling me that cutting the power (75 watts, vs. 150 watts) delivered to one woofer will give you the same output? No. With half the power, delivered to ONE woofer, that ONE woofer will have a net LOSS of 3dB, by virtue of having HALF the power provided to it. Adding a second woofer, with 75 watts delivered to it, will bring your net output back up to what ONE woofer can deliver with twice the power.
stevdart wrote:

This is the single sub with double the power, yielding a 3 db increase:

single_sub_300w_total.jpg

True dat...
stevdart wrote:

Unibox demonstrates that either doubling cone area or doubling power yields +3db. This last pic shows both, for an increase of +6 db, which is what the OP said he wants to do by doubling cone area and doubling total power:

double_sub_300w_total_150w_each.jpg

Yep... See my above statement. This is INDEED where the misunderstanding is occuring. He is NOT doubling the power, delivered to EACH WOOFER. He is doubling the SYSTEM. If what you say is true, then AUTOMATICALLY, and ipso facto, the FIRST setup must magically start producing +3dB, JUST BECAUSE there is a second identical setup NEXT TO IT, and the second system will magically be 3dB louder for the same reason! This cannot happen, can it? You are correct, that doubling cone area will add 3dB, AND doubling power PER WOOFER will add 3dB, but this is not what he is doing. He is ONLY effectively doubling the cone area. Look at it this way: Setup one will produce 100dB. Setup two (identical in every way to setup one, and completely independent) will produce 100dB. 100dB + 100dB = 103dB, a 3dB gain, and not 106dB, a 6dB gain.
stevdart wrote:

And so I shall stand as well (although I must admit, tenuously, as DYohn also has told me what you have stated ;)

Hopefully, my explanation above will help you see the error of your ways. You shold probably listen to DYohn, even if you DON'T listen to me... adding one more sub, noticeable difference? - Page 2 -- posted image. He knows what he's talking about.
"I find your lack of faith disturbing." --Darth Vader BWAHAHAHA (Again, please take that in the spirit intended...)
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
sedate 
Silver - Posts: 1,173
Silver spacespace
Joined: July 03, 2004
Location: Colorado, United States
Posted: April 03, 2007 at 5:12 PM / IP Logged  

Hmm.  It seems as though Grand Moff heamphysts' verbal tap dancing isn't doing the force justice.  Darth Yohn will not save you.

Doubling the SYSTEM increases the output by 6db, not 3db.  All this individual woofer talk is running us in circles. 

Again, our yellow line is 1x12 @ 1w/1m and our red line is 2x12 @ 2w/1m... or a mirrored system.  A 6db increase.

100db+100db = 106db.

adding one more sub, noticeable difference? - Page 2 -- posted image.

"I'm finished!" - Daniel Plainview
custom audio ny 
Copper - Posts: 176
Copper spacespace
Joined: March 11, 2007
Location: United States
Posted: April 03, 2007 at 5:17 PM / IP Logged  

Ok, so in effect what is being stated is that you would need to double the power to EACH sub as well to net the overall theoretical 6db gain?

Hmm..does make sense when you look at it that way. The same holds true in reverse I suppose....if you added the 2nd sub..but cut the power of each in half....nothing gained...so it makes sense that doubling the power to each would net the 3db gain.

Custom Audio
Lynbrook NY
ASE/MECP master certified
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