Surface area comparisons?

[DizRotus]

By my calculations, the surface area of the Exodus Anarchy 6.5" driver is 33.17 Sq in. By comparison, the area of a single 15.0" driver is 176.63 sq in, or 5.32 times the area of the Exodus Anarchy driver.

I understand that the differences of the surrounds makes surface area comparisons difficult, but how can my four 6.5" woofers in the four 25 Hz tapped horn enclosures produce the deep clean bass? To what degree does the dipole nature of a TH enclosure increase the "surface area?"

I also understand that the benefits of multiple smaller subs can offset. "No replacement for displacement."

Is there a simple formula? I suppose sophisticated programs like Horn Response or Akabak take all of the foregoing into consideration.

Edited January 26, 2015 by DizRotus

[Axz Hout]

u

 

[mustang guy]

I always thought of it this way, and I may be wrong. A smaller driver can indeed produce the same or flatter low frequency than a driver multiples of size larger if the driver has the T/S specs for low frequency extension and is in a well tuned enclosure. It can also produce it as loud or louder if the driver is built for power. Hoffman's Iron Law where you can't have all 3, efficient, small and deep bass. You can however have deep bass and small if you have enough power, and you can have deep bass if you have a small driver with a large enclosure end it would be efficient. All this depends on how the driver was manufactured.

 

Those new SVS subs are tiny, but they rock out some low frequency. In fact, they out-spec my THT's. The little Paradigm 8" subs are amazing. They are about 11" cubes, and I couldn't believe how freeking loud and low they go. I was looking around to see where it was coming from, and it was this itty bitty little black box. Amazing!

Edited January 25, 2015 by mustang guy

[derrickdj1]

This may be fun to play with: http://www.diyaudioandvideo.com/Calculator/DriverDisplacement/ or http://www.diyaudioandvideo.com/Calculator/DriverDisplacement/Help.aspx

 

Volume displacement is related to several things and surface are is one of them.

[derrickdj1]

Craig, here are some little guys with deep, loud bass.  Paradigm Sub 1 and 2.  They don't come cheap!

[DizRotus]

Thank you all for the informative replies.

[Scrappydue]

Craig, here are some little guys with deep, loud bass. Paradigm Sub 1 and 2. They don't come cheap!

i was so disappointed in these the first time I heard them. Not even close to the asking price in performance. And this was even before I went diy.

[Chris A]

but how can my four 6.5" woofers in the four 25 Hz tapped horn enclosures produce the deep clean bass? To what degree does the dipole nature of a TH enclosure increase the "surface area?"

 

If you understand the concept of a transformer (a physical example of which is found toward the later parts of this Bell Labs video: https://community.klipsch.com/index.php?/topic/154757-similarities-of-wave-behavior-by-bell-labs/) you'll understand the "impedance matching" effect of horns.  This is fundamental to Klipsch products and why they sound so different (i.e., better) than direct radiating drivers that are much, much less efficient at converting their axial mechanical motion into sound.

 

It's much closer comparing mouth size of horns to direct radiator driver surface area--than comparing driver surface areas in both types of loudspeakers.

 

Remember that a tapped horn (TH) is nothing more than a front horn-loaded driver with both sides of the driver connected to the horn, albeit in different locations along its path length, designed carefully by simulation to cancel out much of the frequency response irregularities due to the undersized horn mouth size and 1/4 wavelength path length (near the horn-driver cutoff frequency). See http://www.danleysoundlabs.com/danley/wp-content/uploads/2012/01/The-Tapped-Horn.pdf

 

Because the TH is using both sides of its driver to produce sound, it will produce about 3 dB, i.e., double sound power output, more sound power relative to a typical front-loaded horn with closed box driver that you see in Klipsch designs.  TH designs are good for what they do--mostly very low frequency subwoofer designs in very small packages--relative to a traditional front-loaded/closed box bass bin, like the La Scala, Belle or Klipschorn.  But TH designs also suffer from more limited output bandwidth than well-designed horn-closed box loudspeakers.  The Klipschorn bass bin, for instance, has about a decade of useful output (40-400 Hz), while a good TH design has about 2 octaves of usable output before significant nulls in the FR start showing up. 

 

TH designs also have a bit of a "precursor" pulse before the main pulse, when playing impulsive music sources - like reproducing kick drums and hammered electric bass recordings.  Depending on the frequencies reproduced (i.e., if the TH frequencies are high enough) these precursor pulses can become audible, leading to some of the criticisms of their sound of using TH horns at too high a crossover frequency.  I recommend using TH designs below 60 Hz, and it's better if you cross them over lower - like 40 Hz (as I do).

 

The clean sound that you mention is the absence of modulation distortion in horn-loaded loudspeakers.  Horns have about the same amount of harmonic distortion (i.e., integer multiples of the input frequency) as direct radiating loudspeakers, but much, much lower modulation distortion, which is much more objectionable to listen to due to its non-harmonic nature and the fact that the distortion frequencies show up at the highest frequencies played by the loudspeaker.  This is why horn-loaded bass sounds so much better: you can hear the much higher levels of modulation distortion in direct radiator bass bins because the modulation distortion shows up at frequencies that most people associate with midrange - middle C (261 Hz) and higher frequencies. 

 

The reason for the lower amounts of modulation distortion in horn-loaded loudspeakers is that the cone or diaphragm of the driver in a horn-loaded loudspeaker typically has to move about 1/5 the distance to product the same sound power output as that same driver used as a direct radiator.  When you think about it, it's actually odd that we have direct radiating loudspeakers, at least from an energy-efficiency standpoint and the dramatic difference in inherent modulation distortion of the two types of loudspeakers.

 

http://en.wikipedia.org/wiki/Horn_loudspeaker

 

Chris

Edited January 26, 2015 by Chris A

[MichaelandKlipsch]

I love this information this forum provides I learn something knew everyday

[DizRotus]

Thank you MichaelandKlipsch.

 

I've noticed that lower is better for the crossover point.

[Chris A]

To what degree does the dipole nature of a TH enclosure increase the "surface area?" I also understand that the benefits of multiple smaller subs can offset...Is there a simple formula? I suppose sophisticated programs like Horn Response or Akabak take all of the foregoing into consideration.

Also note that using a multiplicity subs, either scattered around the room or with mouths manifolded together all in one location in the room, generally obeys the 3 dB nearfield increase per doubling of driver total driven projected area (in the direction of the axial driver motion).  In general, one doesn't count the surround areas of the drivers in these calculations.

 

If you manifold multiple subs' mouths together, you will see a smoothing and deepening of the FR in-room at the locations where bass is not cancelled by room modes.  If you scatter the subs out in the room along the walls, corners, or floor, you will see less in-room cancellation response at your listening position but you won't get the beneficial effects of FR extension and smoothing from manifolding together.

 

If you have access to Hornresp or AkaBak, I'd think that you can generally answer your own questions without my diatribe above (...sorry that I used a scatter-gun approach to answer your questions, since I really don't know what you are doing...) simply by choosing several examples and modeling them, which will give more accurate predictions.  Hornresp does room corner, wall located, or half space (out on the floor) single loudspeaker (or subwoofer) calculations, but I haven't seen a direct capability to manifold multiple subwoofer mouths together. 

 

There are other programs available to estimate room response, the easiest of which I've found to use is Room EQ Wizard (REW), with its enhanced ability to place more than one sub in room at various locations and "walk around" the microphone positions to see the normalized FR/room null plot change immediately to the right of the interactive room geometry plot.  I assume that you want to cover an area of the room, usually at your listening positions, with low bass, i.e., well below the so-called transition frequency (Schroeder frequency) of the room.  Using REW's room simulator is the best and easiest way that I've seen to visualize that.

 

Chris

Edited January 26, 2015 by Chris A

[mustang guy]

 

Craig, here are some little guys with deep, loud bass. Paradigm Sub 1 and 2. They don't come cheap!

i was so disappointed in these the first time I heard them. Not even close to the asking price in performance. And this was even before I went diy.

 

As many of you know, there is a Paradigm store right next to my shop. They have never had a Sub1 or Sub2 to demo. Instead, they have the JL Fathom dual 12. Now that's a beast! I figure my price on one would be like 5 grand new. I have no idea, since that's out of my price range.

 

I did get prices on quad Sub 8's. Less than half the price of a single Fathom 212.

[Scrappydue]

Your tht's should spank that JL. I heard the single 13 and thought it was the same sound quality of my Svs ultra and less output being sealed.

[DaveWJr]

What you guys need to remember about multiple small drivers "equalling" one single larger one in subwoofer design is that air displacement (Xmax * Sd) is not the entire story. Let's use a ported enclosure as an example to keep it simplest. The most basic metric for the rolloff point, or -3dB point (the half-power frequency) is called F3 which I'm sure you know. For a ported enclosure:

 

F3 = [(Vas/Vb) ^0.44] * Fs

 

Vas is the equivalent air compliance of your enclosure (which is a factor of cone area squared), Vb is the net enclosure volume, and Fs is the free air resonance of the driver. Note that this has absolutely nothing to do with port tuning frequency nor should it. This is using simple lumped parameter modeling to determine where the system is at half power.

 

The most important thing to note here is the first part of the equation: no matter what, that part in brackets will always be smaller than Fs. For example, if you have 10000L (over 350 cubic feet ) of Vas and 10L of Vb, that means you've got 21*Fs. No driver and enclosure in the world would exist such as that for a number of reasons (least of which that it wouldn't even be considered a vented system), so it's irrelevant. The ideal Vb is a function of Vas, so you can't cheat the math to get super low extension for free.

 

The point I'm making here is this: the biggest thing then that is going to influence what the F3 is will be the Fs of the driver. Smaller drivers, just due to the fact that  they are small, almost always have lower moving masses and are going to have a higher Fs than a larger driver. Even when you can manage to get them to be the same and can put them in multiples to equal the air displacement of a larger driver, that multi driver system would be so inefficient in comparison AND there is no guarantee that the driver compliance, Cms, which also determines Vas and Fs directly, is going to offset the increase in mass. Chances are that it will not, otherwise the driver would be non-ideal in the system (think very high mass on a bouncy spring moving back and forth....cheap car suspension come to mind?).

 

Note that this is not to say that multiple small drivers cannot create great subwoofers compared to one large one. The point of this exercise was just to show that  volume of air displaced, even at the same input power, is not the whole story for the system response. Hope that helped a bit.

[CECAA850]

Yea but displacement is easier to figure

[mustang guy]

What you guys need to remember about multiple small drivers "equalling" one single larger one in subwoofer design is that air displacement (Xmax * Sd) is not the entire story. Let's use a ported enclosure as an example to keep it simplest. The most basic metric for the rolloff point, or -3dB point (the half-power frequency) is called F3 which I'm sure you know. For a ported enclosure:

 

F3 = [(Vas/Vb) ^0.44] * Fs

 

Vas is the equivalent air compliance of your enclosure (which is a factor of cone area squared), Vb is the net enclosure volume, and Fs is the free air resonance of the driver. Note that this has absolutely nothing to do with port tuning frequency nor should it. This is using simple lumped parameter modeling to determine where the system is at half power.

 

The most important thing to note here is the first part of the equation: no matter what, that part in brackets will always be smaller than Fs. For example, if you have 10000L (over 350 cubic feet ) of Vas and 10L of Vb, that means you've got 21*Fs. No driver and enclosure in the world would exist such as that for a number of reasons (least of which that it wouldn't even be considered a vented system), so it's irrelevant. The ideal Vb is a function of Vas, so you can't cheat the math to get super low extension for free.

 

The point I'm making here is this: the biggest thing then that is going to influence what the F3 is will be the Fs of the driver. Smaller drivers, just due to the fact that  they are small, almost always have lower moving masses and are going to have a higher Fs than a larger driver. Even when you can manage to get them to be the same and can put them in multiples to equal the air displacement of a larger driver, that multi driver system would be so inefficient in comparison AND there is no guarantee that the driver compliance, Cms, which also determines Vas and Fs directly, is going to offset the increase in mass. Chances are that it will not, otherwise the driver would be non-ideal in the system (think very high mass on a bouncy spring moving back and forth....cheap car suspension come to mind?).

 

Note that this is not to say that multiple small drivers cannot create great subwoofers compared to one large one. The point of this exercise was just to show that  volume of air displaced, even at the same input power, is not the whole story for the system response. Hope that helped a bit.

 

These little cube subs we are seeing from Paradigm and SVS must be using low FS drivers in small packages.

 

What is your position on room mode management? Are more small subs better than fewer large ones?

 

I am asking because it seems like a dream come true for men who are strongly influenced by the WAF.

[CECAA850]

What is your position on room mode management? Are more small subs better than fewer large ones?

 

I don't know about his position but Harmon thinks more is better.  4 works well either one centered on each wall or one in each corner.

[Scrappydue]

I say screw the WAF and have 4 big subs! Problem solved.

[DaveWJr]

 

What you guys need to remember about multiple small drivers "equalling" one single larger one in subwoofer design is that air displacement (Xmax * Sd) is not the entire story. Let's use a ported enclosure as an example to keep it simplest. The most basic metric for the rolloff point, or -3dB point (the half-power frequency) is called F3 which I'm sure you know. For a ported enclosure:

 

F3 = [(Vas/Vb) ^0.44] * Fs

 

Vas is the equivalent air compliance of your enclosure (which is a factor of cone area squared), Vb is the net enclosure volume, and Fs is the free air resonance of the driver. Note that this has absolutely nothing to do with port tuning frequency nor should it. This is using simple lumped parameter modeling to determine where the system is at half power.

 

The most important thing to note here is the first part of the equation: no matter what, that part in brackets will always be smaller than Fs. For example, if you have 10000L (over 350 cubic feet ) of Vas and 10L of Vb, that means you've got 21*Fs. No driver and enclosure in the world would exist such as that for a number of reasons (least of which that it wouldn't even be considered a vented system), so it's irrelevant. The ideal Vb is a function of Vas, so you can't cheat the math to get super low extension for free.

 

The point I'm making here is this: the biggest thing then that is going to influence what the F3 is will be the Fs of the driver. Smaller drivers, just due to the fact that  they are small, almost always have lower moving masses and are going to have a higher Fs than a larger driver. Even when you can manage to get them to be the same and can put them in multiples to equal the air displacement of a larger driver, that multi driver system would be so inefficient in comparison AND there is no guarantee that the driver compliance, Cms, which also determines Vas and Fs directly, is going to offset the increase in mass. Chances are that it will not, otherwise the driver would be non-ideal in the system (think very high mass on a bouncy spring moving back and forth....cheap car suspension come to mind?).

 

Note that this is not to say that multiple small drivers cannot create great subwoofers compared to one large one. The point of this exercise was just to show that  volume of air displaced, even at the same input power, is not the whole story for the system response. Hope that helped a bit.

 

These little cube subs we are seeing from Paradigm and SVS must be using low FS drivers in small packages.

 

What is your position on room mode management? Are more small subs better than fewer large ones?

 

I am asking because it seems like a dream come true for men who are strongly influenced by the WAF.

 

They are indeed low Fs, all ~20Hz from the ones I've measured myself.

 

As far as I'm concerned, if you can even consider "few" large subs, then that's answered the question. I would take 2 15s over 4 10s any day of the week, if that's what you're wondering. Reason being, you'll never have perfect modal control. With 2, you can smooth it out nicely, yet there is never a guarantee that you'll do better than that unless your room is spec built for HT and you have 100% control over placement.

[mustang guy]

 

 

What you guys need to remember about multiple small drivers "equalling" one single larger one in subwoofer design is that air displacement (Xmax * Sd) is not the entire story. Let's use a ported enclosure as an example to keep it simplest. The most basic metric for the rolloff point, or -3dB point (the half-power frequency) is called F3 which I'm sure you know. For a ported enclosure:

 

F3 = [(Vas/Vb) ^0.44] * Fs

 

Vas is the equivalent air compliance of your enclosure (which is a factor of cone area squared), Vb is the net enclosure volume, and Fs is the free air resonance of the driver. Note that this has absolutely nothing to do with port tuning frequency nor should it. This is using simple lumped parameter modeling to determine where the system is at half power.

 

The most important thing to note here is the first part of the equation: no matter what, that part in brackets will always be smaller than Fs. For example, if you have 10000L (over 350 cubic feet ) of Vas and 10L of Vb, that means you've got 21*Fs. No driver and enclosure in the world would exist such as that for a number of reasons (least of which that it wouldn't even be considered a vented system), so it's irrelevant. The ideal Vb is a function of Vas, so you can't cheat the math to get super low extension for free.

 

The point I'm making here is this: the biggest thing then that is going to influence what the F3 is will be the Fs of the driver. Smaller drivers, just due to the fact that  they are small, almost always have lower moving masses and are going to have a higher Fs than a larger driver. Even when you can manage to get them to be the same and can put them in multiples to equal the air displacement of a larger driver, that multi driver system would be so inefficient in comparison AND there is no guarantee that the driver compliance, Cms, which also determines Vas and Fs directly, is going to offset the increase in mass. Chances are that it will not, otherwise the driver would be non-ideal in the system (think very high mass on a bouncy spring moving back and forth....cheap car suspension come to mind?).

 

Note that this is not to say that multiple small drivers cannot create great subwoofers compared to one large one. The point of this exercise was just to show that  volume of air displaced, even at the same input power, is not the whole story for the system response. Hope that helped a bit.

 

These little cube subs we are seeing from Paradigm and SVS must be using low FS drivers in small packages.

 

What is your position on room mode management? Are more small subs better than fewer large ones?

 

I am asking because it seems like a dream come true for men who are strongly influenced by the WAF.

 

They are indeed low Fs, all ~20Hz from the ones I've measured myself.

 

As far as I'm concerned, if you can even consider "few" large subs, then that's answered the question. I would take 2 15s over 4 10s any day of the week, if that's what you're wondering. Reason being, you'll never have perfect modal control. With 2, you can smooth it out nicely, yet there is never a guarantee that you'll do better than that unless your room is spec built for HT and you have 100% control over placement.

 

Yes, that is exactly what I was asking. Thanks.

 

I like Scrappy's answer too.  

 

I remember you talking about the 4 subs Carl. That's what got me thinking about several small subs. As you know I've said before that I think a sub should sound as good with the speakers it accompanies at high volume as it does at low volume. The speakers should never be able to pull away from the sub at any volume. With the efficiency of LaScalas those little cubes could never keep up. With Heresy's, it might actually be quite clever.