

Thread Tools 
Newbie
Join Date: Aug 2014
Posts: 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
Do 2 4" = 1 8"
I have an 8" speaker amplifier I use for my guitar. It is a nice warm sound but compare to say a 10" amp it sounds very compressed.
I am trying to figure a way to open the sound without buying a new amp.
If I change the 8" to some type of multiple speaker baffle would that make it sound more open without losing the warmth?
I know Ampeg for instance has a bass amp that has 8 x 10" speakers that a lot of professional bands use but there are other bass players who prefer 15" speakers.
So is it possible to use multiple speakers to achieve the sound of a single speaker adding a more open sound without sacrificing warmth and all the low end?
Any help greatly appreciated.
I am trying to figure a way to open the sound without buying a new amp.
If I change the 8" to some type of multiple speaker baffle would that make it sound more open without losing the warmth?
I know Ampeg for instance has a bass amp that has 8 x 10" speakers that a lot of professional bands use but there are other bass players who prefer 15" speakers.
So is it possible to use multiple speakers to achieve the sound of a single speaker adding a more open sound without sacrificing warmth and all the low end?
Any help greatly appreciated.
Sponsored Links  
Advertisement


AVS Special Member
Join Date: Jun 2007
Posts: 7,160
Mentioned: 11 Post(s)
Tagged: 1 Thread(s)
Quoted: 1408 Post(s)
Liked: 1472
No it doesn't. Not even close. Also guitar speakers normally don't enough excursion to handle bass notes.
AVS Special Member
Join Date: Oct 2003
Location: Formerly Chicagoland, now Doylestown, PA
Posts: 3,118
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 268 Post(s)
Liked: 144
Quote:
I have an 8" speaker amplifier I use for my guitar. It is a nice warm sound but compare to say a 10" amp it sounds very compressed.
I am trying to figure a way to open the sound without buying a new amp.
If I change the 8" to some type of multiple speaker baffle would that make it sound more open without losing the warmth?
I know Ampeg for instance has a bass amp that has 8 x 10" speakers that a lot of professional bands use but there are other bass players who prefer 15" speakers.
So is it possible to use multiple speakers to achieve the sound of a single speaker adding a more open sound without sacrificing warmth and all the low end?
Any help greatly appreciated.
I am trying to figure a way to open the sound without buying a new amp.
If I change the 8" to some type of multiple speaker baffle would that make it sound more open without losing the warmth?
I know Ampeg for instance has a bass amp that has 8 x 10" speakers that a lot of professional bands use but there are other bass players who prefer 15" speakers.
So is it possible to use multiple speakers to achieve the sound of a single speaker adding a more open sound without sacrificing warmth and all the low end?
Any help greatly appreciated.
An extension cabinet will give you a bigger sound, but won't change your tone much. I occasionally used to use an extension cabinet with my JC120 depending on the venue back in the day. But that was primarily due to stage configuration, and not any specific tone I was looking for.
I'm guessing the 8" amp is a practice amp? Are you looking for better tone while practicing, but yet not wanting to disturb the rest of the house?
AVS Special Member
Join Date: Feb 2010
Location: Monument CO
Posts: 8,058
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1064 Post(s)
Liked: 702
Even if all parameters were exactly the same, the area of two 4" circles is about 25"sq and the area of a single 8" circle is about 50"sq.
As others have said there are so many variables that speaker size is a poor determination of most anything except in a very general way. Displacement, various speaker parameters, enclosure size and type, etc. play into the sound.
As others have said there are so many variables that speaker size is a poor determination of most anything except in a very general way. Displacement, various speaker parameters, enclosure size and type, etc. play into the sound.
"After silence, that which best expresses the inexpressible, is music"  Aldous Huxley
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
Find the Piston area of the speakers using the area of a circle. If you do this, you will get a chart that looks something like this 
4.5"  1
5.0  1.3
6.5  2.6
8.0  4.3
10  6.8
12  9.9
15  16.0
This was actually given to me when I asked a similar question in another forum.
Area of a Circle equals PI times the Radius Squared.
A = (PI) R²
So, let's work this out.
A = (pi) R² = (3.14159) x 2² = 3.14159 x 4 = 12.566 square inches
A = (pi) R² = (3.14159) x 4² = 3.14159 x 16 = 50.265 square inches
So, if we divide the two 50.265/12.566 = 4.00
So, one 8" speakers equal FOUR 4" speakers.
Here is another chart that I calculated myself 
4.00" = 12.57 sq.in. = 1.00
5.00" = 19.64 sq.in. = 1.56
5.25" = 21.65 sq.in. = 1.72
6.00" = 28.27 sq.in. = 2.49
6.50" = 33.18 sq.in. = 2.64
7.00" = 38.49 sq.in. = 3.06
8.00" = 50.27 sq.in. = 3.999 = 4.0
10.0" = 78.54 sq.in. = 6.25
12.0" = 113.1 sq.in. = 8.997 = 9.0
15.0" = 176.7 sq.in. = 14.06
Using this chart, we divide 4 (for an 8" speaker) by 1 (for a 4" speaker) and we get the same result; FOUR 4" speakers equals ONE 8" speaker.
Also notice that a 6.5" speaker using this last chart, is 70% larger than a 5" speaker. (2.64/1.56 = 1.70)
A 12" speaker is 125% larger than a 8" speaker. (9/4 =2.25)
And so on...
Steve/bluewizard
4.5"  1
5.0  1.3
6.5  2.6
8.0  4.3
10  6.8
12  9.9
15  16.0
This was actually given to me when I asked a similar question in another forum.
Area of a Circle equals PI times the Radius Squared.
A = (PI) R²
So, let's work this out.
A = (pi) R² = (3.14159) x 2² = 3.14159 x 4 = 12.566 square inches
A = (pi) R² = (3.14159) x 4² = 3.14159 x 16 = 50.265 square inches
So, if we divide the two 50.265/12.566 = 4.00
So, one 8" speakers equal FOUR 4" speakers.
Here is another chart that I calculated myself 
4.00" = 12.57 sq.in. = 1.00
5.00" = 19.64 sq.in. = 1.56
5.25" = 21.65 sq.in. = 1.72
6.00" = 28.27 sq.in. = 2.49
6.50" = 33.18 sq.in. = 2.64
7.00" = 38.49 sq.in. = 3.06
8.00" = 50.27 sq.in. = 3.999 = 4.0
10.0" = 78.54 sq.in. = 6.25
12.0" = 113.1 sq.in. = 8.997 = 9.0
15.0" = 176.7 sq.in. = 14.06
Using this chart, we divide 4 (for an 8" speaker) by 1 (for a 4" speaker) and we get the same result; FOUR 4" speakers equals ONE 8" speaker.
Also notice that a 6.5" speaker using this last chart, is 70% larger than a 5" speaker. (2.64/1.56 = 1.70)
A 12" speaker is 125% larger than a 8" speaker. (9/4 =2.25)
And so on...
Steve/bluewizard
Last edited by bluewizard; 08202014 at 03:37 PM.
Advanced Member
Join Date: Aug 2002
Location: USA
Posts: 763
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 87 Post(s)
Liked: 35
I think you meant to say "225% larger".
David Lynch Current Equipment: Marantz AV8801, Proceed HPA3, Parasound HCA1206, Aerial Acoustics LR5's (LCR), Aerial Acoustics LR3's (sides), RBH inwalls (rears), Seaton Submersive, Marantz VP15s1, 106" Carada BW screen, Oppo BDP103.
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
If you want the difference between two specific speakers rather than a generalization, look up the full specs on the speakers, and look at the Sd specification, which is the surface area of the actual cone.
Here is a chart I makes using the Sd of Dayton speakers. Keeping in mind that the cones could be very different. On could be shallow and flat, another very deep.
Using Dayton woofers as an example, and using their Sd spec, we determine the relative effective size of various speakers.
4.00" = 37.4 cm² = 1.00
5.00" = 52.8 cm² = 1.41
5.25" = 93.3 cm² = 2.49
6.00" = 84.9 cm² = 2.27
6.50" = 134.8cm² = 3.60
7.00" = 132.7cm² = 3.55 (more typical 125cm²)
8.00" = 211.2cm² = 5.65
10.0" = 343.1cm² = 9.17
12.0" = 498.8cm² = 13.3
15.0" = 843.7cm² = 22.6
Further because the surround is not part of the Pistonic action of the driver, we have to subtract the surrounds. Now a typical surround is about 0.75". But part, about half of the surround, does have some pistonic action; about half.
To allow for this, we subtract 0.75" from the rated dimension of the speakers.
So, an 8" speaker minus 0.75" is now 7.25". To find the area we still use the same formula (7.25/2 = 3.626) 
A = (pi) R² = 3.14159 x 3.625² = 41.28 square inches.
Now a 4" driver, which would now be 3.25" (3.25/2 = 1.625) 
A = (pi) R² = 3.14159 x 1.625² =8.296 square inches
So, we divide the value for the 8" by the value for the 4" and we have 
41.28 / 8.296 = 4.96
Using this method, it takes 4.96 FOUR inch drivers to equal ONE 8" driver.
This is probably the most accurate as a general estimation for all drivers, as it uses the actual cone diameter plus half the Surround, and assumes Pistonic action.
Sorry haven't worked this chart out yet.
The corrected formula, though more confusing, would be  where "D" is diameter 
A = (pi) ((D  0.75) / 2)²
A = (pi) ((8"  0.75) / 2)²
A = (pi) ((7.25) / 2)²
A = (pi) (3.625)² = 3.14159 (3.625)² = 41.28
Which is exactly what we had before
Steve/bluewizard
Here is a chart I makes using the Sd of Dayton speakers. Keeping in mind that the cones could be very different. On could be shallow and flat, another very deep.
Using Dayton woofers as an example, and using their Sd spec, we determine the relative effective size of various speakers.
4.00" = 37.4 cm² = 1.00
5.00" = 52.8 cm² = 1.41
5.25" = 93.3 cm² = 2.49
6.00" = 84.9 cm² = 2.27
6.50" = 134.8cm² = 3.60
7.00" = 132.7cm² = 3.55 (more typical 125cm²)
8.00" = 211.2cm² = 5.65
10.0" = 343.1cm² = 9.17
12.0" = 498.8cm² = 13.3
15.0" = 843.7cm² = 22.6
Further because the surround is not part of the Pistonic action of the driver, we have to subtract the surrounds. Now a typical surround is about 0.75". But part, about half of the surround, does have some pistonic action; about half.
To allow for this, we subtract 0.75" from the rated dimension of the speakers.
So, an 8" speaker minus 0.75" is now 7.25". To find the area we still use the same formula (7.25/2 = 3.626) 
A = (pi) R² = 3.14159 x 3.625² = 41.28 square inches.
Now a 4" driver, which would now be 3.25" (3.25/2 = 1.625) 
A = (pi) R² = 3.14159 x 1.625² =8.296 square inches
So, we divide the value for the 8" by the value for the 4" and we have 
41.28 / 8.296 = 4.96
Using this method, it takes 4.96 FOUR inch drivers to equal ONE 8" driver.
This is probably the most accurate as a general estimation for all drivers, as it uses the actual cone diameter plus half the Surround, and assumes Pistonic action.
Sorry haven't worked this chart out yet.
The corrected formula, though more confusing, would be  where "D" is diameter 
A = (pi) ((D  0.75) / 2)²
A = (pi) ((8"  0.75) / 2)²
A = (pi) ((7.25) / 2)²
A = (pi) (3.625)² = 3.14159 (3.625)² = 41.28
Which is exactly what we had before
Steve/bluewizard
Last edited by bluewizard; 08182014 at 03:53 PM.
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
I think you meant to say "225% larger".
Yeah, that is confusing. If you divide one by the other, the first 100% they are the same, it is only the addition 125% that it is larger.
For example, if the answer were 1.25, that would only be 25% larger.
Another example, we can clearly see that 625 is only 25% larger than 500.
But if you divide 625 / 500 you get 1.25. Clearly it is not 125% larger, just 25% LARGER.
Look at it this way, I think it is less confusing 
Also notice that a 6.5" speaker using this last chart, is 70% larger than a 5" speaker. (2.64/1.56 = 1.70)
A 12" speaker is 125% larger than a 8" speaker. (9/4 =2.25)
Restated, and the way we would commonly look at it 
It takes 1.7 FIVE inch divers to equal ONE 6.5" driver.
It takes 2.25 EIGHT inch drivers to equal ONE 12" driver.
What we functionally want to know is NOT how much bigger is this than that, but rather how many of these does it take to equal one of those.
Steve/bluewizard
Yeah, that is confusing. If you divide one by the other, the first 100% they are the same, it is only the addition 125% that it is larger.
For example, if the answer were 1.25, that would only be 25% larger.
Another example, we can clearly see that 625 is only 25% larger than 500.
But if you divide 625 / 500 you get 1.25. Clearly it is not 125% larger, just 25% LARGER.
Look at it this way, I think it is less confusing 
Also notice that a 6.5" speaker using this last chart, is 70% larger than a 5" speaker. (2.64/1.56 = 1.70)
A 12" speaker is 125% larger than a 8" speaker. (9/4 =2.25)
Restated, and the way we would commonly look at it 
It takes 1.7 FIVE inch divers to equal ONE 6.5" driver.
It takes 2.25 EIGHT inch drivers to equal ONE 12" driver.
What we functionally want to know is NOT how much bigger is this than that, but rather how many of these does it take to equal one of those.
Steve/bluewizard
Last edited by bluewizard; 08182014 at 03:48 PM.
Advanced Member
Join Date: Aug 2002
Location: USA
Posts: 763
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 87 Post(s)
Liked: 35
Quote:
I think you meant to say "225% larger".
Yeah, that is confusing. If you divide one by the other, the first 100% they are the same, it is only the addition 125% that it is larger.
For example, if the answer were 1.25, that would only be 25% larger.
Another example, we can clearly see that 625 is only 25% larger than 500.
But if you divide 625 / 500 you get 1.25. Clearly it is not 125% larger, just 25% LARGER.
Look at it this way, I think it is less confusing 
Also notice that a 6.5" speaker using this last chart, is 70% larger than a 5" speaker. (2.64/1.56 = 1.70)
A 12" speaker is 125% larger than a 8" speaker. (9/4 =2.25)
Restated, and the way we would commonly look at it 
It takes 1.7 FIVE inch divers to equal ONE 6.5" driver.
It takes 2.25 EIGHT inch drivers to equal ONE 12" driver.
What we functionally want to know is NOT how much bigger is this than that, but rather how many of these does it take to equal one of those.
Steve/bluewizard
Yeah, that is confusing. If you divide one by the other, the first 100% they are the same, it is only the addition 125% that it is larger.
For example, if the answer were 1.25, that would only be 25% larger.
Another example, we can clearly see that 625 is only 25% larger than 500.
But if you divide 625 / 500 you get 1.25. Clearly it is not 125% larger, just 25% LARGER.
Look at it this way, I think it is less confusing 
Also notice that a 6.5" speaker using this last chart, is 70% larger than a 5" speaker. (2.64/1.56 = 1.70)
A 12" speaker is 125% larger than a 8" speaker. (9/4 =2.25)
Restated, and the way we would commonly look at it 
It takes 1.7 FIVE inch divers to equal ONE 6.5" driver.
It takes 2.25 EIGHT inch drivers to equal ONE 12" driver.
What we functionally want to know is NOT how much bigger is this than that, but rather how many of these does it take to equal one of those.
Steve/bluewizard
I hope you didn't think I was criticizing.; Actually I appreciate that you took the time to show the calculations. There are a lot of people here who don't understand formulas for calculating areas, and, that goes along way when trying to determine relative driver size equivalents.
David Lynch Current Equipment: Marantz AV8801, Proceed HPA3, Parasound HCA1206, Aerial Acoustics LR5's (LCR), Aerial Acoustics LR3's (sides), RBH inwalls (rears), Seaton Submersive, Marantz VP15s1, 106" Carada BW screen, Oppo BDP103.
AVS Addicted Member
Join Date: Nov 2009
Location: New Hampshire
Posts: 11,978
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 2680
Sd accounts for the surround, there's no subtraction to be made.
Bill Fitzmaurice Loudspeaker Design
The Laws of Physics aren't swayed by opinion.
The Laws of Physics aren't swayed by opinion.
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
Quote:
Sd accounts for the surround, there's no subtraction to be made.
The subtractions only occurs relative to the Rated Size of a speaker. Even that is an estimate because the surround on my 5" desktop speakers are smaller than the surrounds on my 12" speakers. So, I make a best guess on what is typical.
From the outer edge of my 12" driver to the center of the surround is actually about 7/8". I guess I should actually use twice that amount because there is a Surround on both edges of the cone. So, subtract 1.75 for both edges of the surround.
On my 5" bookshelf speaker, it is about 0.5" from the edge to the center of the surround, so now that you have me thinking about it, I should subtract TWICE that or 1".
You can subtract 0.75" or 1.0" or 1.5" as you please, but you subtract this from the Rated Size of the speaker. Not the Sd. You are converting the Rated size (5", 5.25", 6.5", 8", etc...) to the functional Piston size.
The Sd is what the Sd is. No need for any conversions or adjustments. And in my calculations based on Sd, I didn't make any adjustments, I just used the Sd numbers.
For the purposes of this discussion, we are interested in the general size of a 4" relative to the general size of a 8".
If you have specific speakers you can measure them, and use the numbers you find in your own calculations.
Hopefully I haven't confused the issue more.
Steve/bluewizard
Last edited by bluewizard; 08192014 at 02:07 PM.
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
AVS Special Member
Join Date: Jan 2011
Location: Iowa City, Iowa
Posts: 3,642
Mentioned: 5 Post(s)
Tagged: 1 Thread(s)
Quoted: 585 Post(s)
Liked: 554
I assume the OP was talking more about SPL...which is more of a loaded question.
Set up #1: EMP e5ti, e5Ci, and EMP e5Bi surrounds, Outlaw LFM1 Plus sub, EMP 10i10i sub
Set up #2: Def Tech SM450, CLR2002, SLS Qline surrounds and Klipsch 12wD sub
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
I don't think it is so much about SPL as it is about the general tone of the speakers.
There are a lot of details missing from the original post. The 8" sound more compressed, but is it in a small closed cabinet? Is the 10" in a larger or possibly open cabinet?
The smaller and tighter a given cabinet is, the less output you get from it.
Generally you will get more output and more impact for more and larger speakers.
For bass, 12" and 15" are the most common. For Lead, 10" and 12" are the most common. Typically 8" are used in practice amps.
One has to now ask, how much money do you have to spend?
For example, you could build a Marshall halfstack using 10" speakers, but just the raw drivers alone in a common brand is going to cost roughly $65 each in brands like Celestion or Eminence. That means $260 on just drivers, then you have the additional cost of the cabinet.
Typically, the bigger the driver, and the more drivers you use, the bigger the cabinet. No way around that.
Then you have to consider Impedance; both the total for the number of speakers you have, and the capabilities of your amp.
There are two configurations that I know of where you can combine several speakers, and in the end have the same impedance as one single speaker. These are 4 speakers, and 9 speakers.
With 4 drivers, you combine 2 in parallel, the wire those two gangs in series. Or the alternative that will produce the same result. Place 2 drivers in series, the wire those 3 gangs in parallel. If you have 8 ohms speakers, the when the four are combine the total will still be 8 ohms.
The other with 9 drivers, you wire 3 drivers wired in series, that will give you 3 gangs, wire those gangs in parallel and the final impedance will be the same as that of one speaker.
Three 8 ohm in series is 24 ohms.
Three 24 ohm gangs in parallel is 8 ohms.
So, yes it is possible to do what you want to do, the question is, how much money are you willing spend and how much work are you willing to do, to make it happen?
It would also be helpful if you told us specifically what equipment you have. Also, it this a selfcontained amp; speaker and amp in one, or is it a separate head and bottom?
Steve/bluewizard
There are a lot of details missing from the original post. The 8" sound more compressed, but is it in a small closed cabinet? Is the 10" in a larger or possibly open cabinet?
The smaller and tighter a given cabinet is, the less output you get from it.
Generally you will get more output and more impact for more and larger speakers.
For bass, 12" and 15" are the most common. For Lead, 10" and 12" are the most common. Typically 8" are used in practice amps.
One has to now ask, how much money do you have to spend?
For example, you could build a Marshall halfstack using 10" speakers, but just the raw drivers alone in a common brand is going to cost roughly $65 each in brands like Celestion or Eminence. That means $260 on just drivers, then you have the additional cost of the cabinet.
Typically, the bigger the driver, and the more drivers you use, the bigger the cabinet. No way around that.
Then you have to consider Impedance; both the total for the number of speakers you have, and the capabilities of your amp.
There are two configurations that I know of where you can combine several speakers, and in the end have the same impedance as one single speaker. These are 4 speakers, and 9 speakers.
With 4 drivers, you combine 2 in parallel, the wire those two gangs in series. Or the alternative that will produce the same result. Place 2 drivers in series, the wire those 3 gangs in parallel. If you have 8 ohms speakers, the when the four are combine the total will still be 8 ohms.
The other with 9 drivers, you wire 3 drivers wired in series, that will give you 3 gangs, wire those gangs in parallel and the final impedance will be the same as that of one speaker.
Three 8 ohm in series is 24 ohms.
Three 24 ohm gangs in parallel is 8 ohms.
So, yes it is possible to do what you want to do, the question is, how much money are you willing spend and how much work are you willing to do, to make it happen?
It would also be helpful if you told us specifically what equipment you have. Also, it this a selfcontained amp; speaker and amp in one, or is it a separate head and bottom?
Steve/bluewizard
Last edited by bluewizard; 08192014 at 04:01 PM.
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
It really would help if we know the specific equipment you were talking about. We could look up specs and photos and get some sense of the possible differences.
A closed cabinet is going to be less efficient, meaning less output, than an fully or partly open back cabinet.
The common selfcontained pick it up and carry it amps like the Fender Twin Reverb, were most often Open back cabinets. Where as larger multidriver cabinets like a typical Marshal stack were  large and closed.
It could be the power of the respective amps.
It could be the quality of the respective amps and speakers.
A number of factor could come into play.
Steve/bluewizard
A closed cabinet is going to be less efficient, meaning less output, than an fully or partly open back cabinet.
The common selfcontained pick it up and carry it amps like the Fender Twin Reverb, were most often Open back cabinets. Where as larger multidriver cabinets like a typical Marshal stack were  large and closed.
It could be the power of the respective amps.
It could be the quality of the respective amps and speakers.
A number of factor could come into play.
Steve/bluewizard
Last edited by bluewizard; 08192014 at 06:20 PM.
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
Just following up on the Relative Size aspect.
OK, I recalculated using this formula 
A = (pi) ((D  1.5) / 2)²
OK, I recalculated using this formula 
A = (pi) ((D  1.5) / 2)²
I used 1.5 as the adjustment factor, based on the fact that my 5" speakers would be 1 and my 12" speaker would be 2, and this was halfway between. The only way to get more accurate, would be to measure actual specific drivers between the outer edge of the frame and the center of the surround, then double that number and use it in the calculations. Alternately simply measure from the center of the surround to the center of the surround to get the true piston diameter of the driver.
I also performed the calculations in an EXCEL spreadsheet, and verified the first calculations using a calculator to make sure I had entered the formula correctly in the spreadsheet.
Here are the results. This is a closer approximation of the true piston size of a range of drivers 
4.00" = 4.91 sq.in. = 1.00
5.00" = 9.62 sq.in. = 1.96
5.25" = 11.05 sq.in. = 2.25
6.00" = 15.90 sq.in. = 3.24
6.50" = 19.64 sq.in. = 4.00
7.00" = 23.76 sq.in. = 4.48
8.00" = 33.18 sq.in. = 6.76
10.0" = 56.75 sq.in. = 11.56
12.0" = 86.59 sq.in. = 17.64
15.0" = 143.14 sq.in. = 29.16
If we compare a 6.5" and a 5" using this new chart, we have 4/1.96 = 2.04. So, a 6.5" is 2.04 times bigger than a 5" driver.
If we use the previous chart that simply used the Rated Dimension and made no adjustment, then compare the two same two drivers, we have 2.64/1.56 = 1.69 or 1.7. Implying that a 6.5" is is 1.7 times bigger than a 5".
If we compare 3x6.5" against 2x8" we now have 
three 6.5" 
3 x 4 = 12
two 8" 
2 x 6.76 = 13.53
13.53 / 12 = 1.1275 = 1.13
So, using these new numbers, TWO 8" drivers are about 13% larger than THREE 6.5" drivers.
Using the original Rated Size unadjusted chart we have 8 / 7.92 = 1.01, or the 2x8" is 1% larger.
I think either way, you can get a rough idea of the relative difference between two different driver configurations.
Which you use is up to you.
Steve/bluewizard
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
Again, with no additional information, the best I can say is that a better 8" driver is going to be better than two 4" drivers.
Without being able to see the amps and speakers, there is not much anyone can really say.
Steve/bluewizard
Without being able to see the amps and speakers, there is not much anyone can really say.
Steve/bluewizard
AVS Special Member
Join Date: Feb 2010
Location: Monument CO
Posts: 8,058
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1064 Post(s)
Liked: 702
If you're going to all that trouble to calculate relative area (much more than I would have done for this thread, but nice job!) you might as well find the angle of the cone as it slopes to the middle and add that bit of area in, plus the extra area of the dust dome if present, since none of that is usually a simple flat (2D) circle...
Still think my original answer was close enough (post 4) since there are so many variables involved in figuring out actual output, let alone the tone of that output...
Still think my original answer was close enough (post 4) since there are so many variables involved in figuring out actual output, let alone the tone of that output...
"After silence, that which best expresses the inexpressible, is music"  Aldous Huxley
AVS Special Member
Join Date: Jul 2008
Posts: 2,147
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1048 Post(s)
Liked: 455
Using Dayton Drivers and the Sd specification, I came up with this, however, give the many variables, this falls short of a generalization. Meaning, it is not a generalization that can be applied to all driver, because its specific, it can only be applied to these drivers.
If you have two specific drivers and if you have their Sd specs, then you can compare them.
But what if you don't?
Using Dayton woofers as an example, and using their SD spec, we determine the relative effective size of various speakers.
4.00" = 37.4 cm² = 1.00
5.00" = 52.8 cm² = 1.41
5.25" = 93.3 cm² = 2.49
6.00" = 84.9 cm² = 2.27
6.50" = 134.8cm² = 3.60
7.00" = 132.7cm² = 3.55 (more typical 125cm²)
8.00" = 211.2cm² = 5.65
10.0" = 343.1cm² = 9.17
12.0" = 498.8cm² = 13.3
15.0" = 843.7cm² = 22.6
Using these numbers, if we compare 3x6.5" to 2x8", what do we come up with?
3x6.5" = 3 x 3.60 = 10.8
2x8" = 2 x 5.65 = 11.3
11.3 / 10.8 = 1.0463
Or 2x8" is about 5% larger. But that only applies to these specific drivers.
But regardless of the actual numbers, the result is the same, 3x6.5" are roughly equal to 2x8".
Steve/bluewizard
If you have two specific drivers and if you have their Sd specs, then you can compare them.
But what if you don't?
Using Dayton woofers as an example, and using their SD spec, we determine the relative effective size of various speakers.
4.00" = 37.4 cm² = 1.00
5.00" = 52.8 cm² = 1.41
5.25" = 93.3 cm² = 2.49
6.00" = 84.9 cm² = 2.27
6.50" = 134.8cm² = 3.60
7.00" = 132.7cm² = 3.55 (more typical 125cm²)
8.00" = 211.2cm² = 5.65
10.0" = 343.1cm² = 9.17
12.0" = 498.8cm² = 13.3
15.0" = 843.7cm² = 22.6
Using these numbers, if we compare 3x6.5" to 2x8", what do we come up with?
3x6.5" = 3 x 3.60 = 10.8
2x8" = 2 x 5.65 = 11.3
11.3 / 10.8 = 1.0463
Or 2x8" is about 5% larger. But that only applies to these specific drivers.
But regardless of the actual numbers, the result is the same, 3x6.5" are roughly equal to 2x8".
Steve/bluewizard
Last edited by bluewizard; 08242014 at 02:52 PM.
Newbie
Join Date: Aug 2014
Posts: 2
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
Thank you for all your help. One of the things I am taking away from all of this is the cabinet influence.
In any event the cabinet volume is .43cu/ft with 2 1" x 2" ports. So I am not sure of I should consider a bigger cab or maybe play with the ports.
I do appreciate all the help
In any event the cabinet volume is .43cu/ft with 2 1" x 2" ports. So I am not sure of I should consider a bigger cab or maybe play with the ports.
I do appreciate all the help
AVS Special Member
Join Date: Feb 2010
Location: Monument CO
Posts: 8,058
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1064 Post(s)
Liked: 702
PM Bill Fitzmaurice. He posted to you earlier and design speakers. He can suggest a program or two that would help you out.
"After silence, that which best expresses the inexpressible, is music"  Aldous Huxley
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,593
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 851 Post(s)
Liked: 1224
Quote:
Steve,
I hope you didn't think I was criticizing.; Actually I appreciate that you took the time to show the calculations. There are a lot of people here who don't understand formulas for calculating areas, and, that goes along way when trying to determine relative driver size equivalents.
I hope you didn't think I was criticizing.; Actually I appreciate that you took the time to show the calculations. There are a lot of people here who don't understand formulas for calculating areas, and, that goes along way when trying to determine relative driver size equivalents.
Maximum possible Xmax tends to go up with the diameter of the cone.
So a 12" driver has about 250% the cone area of an 8 inch, and can also have 150% as much Xmax, further increasing its potential bass dynamic range. These are of course rough approximations, but they make the point that just like "There is no substitute for cubic inches (in car engines)", "There is no substitute for cone diameter (in subwoofers)."
Member
Join Date: Aug 2014
Location: Los Angeles
Posts: 21
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Liked: 1
As a n00b to this place who has hung out on guitar forums for years, It's kind of funny to run into a thread like this on an AV forum.
I can't think of a guitar amp/cab with 4" speakers that sounds good. My old Fender Champ has an 8" speaker and it sounds wonderful, but some people mod them with 10 inch speakers to get more volume or low end. I think that would be a much better way to go than modding it for smaller speakers. Also, a larger speaker should be able to handle more signal without overloading or compressing the sound (ceteris paribus). As for "warmth", that is going to depend a lot on your choice of speaker, but it shouldn't be hard to retain warmth with the right larger speaker.
I can't think of a guitar amp/cab with 4" speakers that sounds good. My old Fender Champ has an 8" speaker and it sounds wonderful, but some people mod them with 10 inch speakers to get more volume or low end. I think that would be a much better way to go than modding it for smaller speakers. Also, a larger speaker should be able to handle more signal without overloading or compressing the sound (ceteris paribus). As for "warmth", that is going to depend a lot on your choice of speaker, but it shouldn't be hard to retain warmth with the right larger speaker.
Sponsored Links  
Advertisement


Thread Tools  
Show Printable Version Show Printable Version
Email this Page Email this Page


Posting Rules  