Hi Myles,
Question for you. Is your goal to drive a given woofer to Xmax or beyond, or is it to reproduce very low bass with a minimum of power required?
Too often people buy a speaker on power handling capacity alone, when that very goal misses the entire point. To my mind, if you can push the same volume of air with - say 35 watts of power as you can with 250 watts of power, which direction would you go? It seems to me that doing the same job with a smaller amount of power required is the only way to go. All that extra power to drive the less efficient driver / box combination only results in heat and higher electrical bills. Keep in mind that an efficient driver put in a situation that decreases the efficiency will do the same thing as a inefficient driver in a correct box (more efficient). Higher heat and power bills.
All that heat I'm talking about? That can rob you of 2 dB sensitivity in your woofer, and the heat will throw off the T/S parameters that were used to design the enclosure. That means the tuning will be off by some degree as well. If the box is the optimal size, then the changes won't be too serious. If the box was made to be smaller (accepting a higher system Q), then those parameter shifts become more serious. I don't know ... if it were me making this choice, I would probably opt for the woofer that reproduced the lowest frequencies in the largest size box I could tolerate with the least amount of power required. Having a woofer that can dissipate 500 watts (say) isn't something to be proud of if you need that power to create the sound pressures that lower powered systems can reach. I guess society and salespeople became all caught up in the power race so deeply that the goal became obscured. Lost in the fog of power handling capacity (which is often wishful thinking). Most of the power you send to a speaker is converted into heat. Therefore, a woofer claimed to handle 200 watts (say) will probably be dissipating 190 watts of heat. Have a long hard look at the voice coil and tell me it can dissipate that much heat without melting / burning. A high temperature 1" voice coil made from aluminum and high temperature epoxy can safely dissipate about 35 watts (in real life). Remember too, that the paper or composite cone material is glued to the voice coil former. It has some distinctly rigid temperature restrictions. That should be a sobering thought for some.
-Chris
Question for you. Is your goal to drive a given woofer to Xmax or beyond, or is it to reproduce very low bass with a minimum of power required?
Too often people buy a speaker on power handling capacity alone, when that very goal misses the entire point. To my mind, if you can push the same volume of air with - say 35 watts of power as you can with 250 watts of power, which direction would you go? It seems to me that doing the same job with a smaller amount of power required is the only way to go. All that extra power to drive the less efficient driver / box combination only results in heat and higher electrical bills. Keep in mind that an efficient driver put in a situation that decreases the efficiency will do the same thing as a inefficient driver in a correct box (more efficient). Higher heat and power bills.
All that heat I'm talking about? That can rob you of 2 dB sensitivity in your woofer, and the heat will throw off the T/S parameters that were used to design the enclosure. That means the tuning will be off by some degree as well. If the box is the optimal size, then the changes won't be too serious. If the box was made to be smaller (accepting a higher system Q), then those parameter shifts become more serious. I don't know ... if it were me making this choice, I would probably opt for the woofer that reproduced the lowest frequencies in the largest size box I could tolerate with the least amount of power required. Having a woofer that can dissipate 500 watts (say) isn't something to be proud of if you need that power to create the sound pressures that lower powered systems can reach. I guess society and salespeople became all caught up in the power race so deeply that the goal became obscured. Lost in the fog of power handling capacity (which is often wishful thinking). Most of the power you send to a speaker is converted into heat. Therefore, a woofer claimed to handle 200 watts (say) will probably be dissipating 190 watts of heat. Have a long hard look at the voice coil and tell me it can dissipate that much heat without melting / burning. A high temperature 1" voice coil made from aluminum and high temperature epoxy can safely dissipate about 35 watts (in real life). Remember too, that the paper or composite cone material is glued to the voice coil former. It has some distinctly rigid temperature restrictions. That should be a sobering thought for some.
-Chris
Thanks Neil, Ill have a look tonight. Even a basic understanding would help a lot 🙂
Anatech, I think you miss understood my intentions. I'm not looking for the highest power rated sub I can afford thinking ill low my legs off with bass. If you can suggest an affordable, quality 10'' subwoofer with a lower power rating I would be stoked. I just want quality bass in a smallish subwoofer for an affordable price. the Dayton Audio RSS265HF-4 10" Reference HF was the closest thing available in Aus that I could find. I guess I know a little more about what to look for in a driver now though. Maybe Ill see if I can find something with a little more sensitivity and less RMS?
My question about the Xmax being exceeded was more concern whether I would damage the driver in a 1.5 ft^3 box playing at 150W? Is exceeding the Xmax bad? I feel like it is for some reason.
Cheers 🙂
Anatech, I think you miss understood my intentions. I'm not looking for the highest power rated sub I can afford thinking ill low my legs off with bass. If you can suggest an affordable, quality 10'' subwoofer with a lower power rating I would be stoked. I just want quality bass in a smallish subwoofer for an affordable price. the Dayton Audio RSS265HF-4 10" Reference HF was the closest thing available in Aus that I could find. I guess I know a little more about what to look for in a driver now though. Maybe Ill see if I can find something with a little more sensitivity and less RMS?
My question about the Xmax being exceeded was more concern whether I would damage the driver in a 1.5 ft^3 box playing at 150W? Is exceeding the Xmax bad? I feel like it is for some reason.
Cheers 🙂
Using the box air spring to prevent mechanical damage from overexcursion is a bad plan. In a small box the air spring is strong and it requires a ton of power to overcome that spring to get the driver to the excursion limits. As you have been told a bunch of times now excessive power is a driver's enemy.
From the power perspective, IB is the best size for a sealed box. The problem is IB is either a HUGE box or it requires cutting into your walls (or ceiling or floor). If you can reach your excursion limits with well under the driver's rated power handling that is a good thing, not a bad thing.
A speaker will produce a great deal of distortion when pushed to the excursion limit and that's when you turn it down. When you turn it up and it kind of sounds a bit louder but sounds like it loses impact and sounds mushy, that's when you dial it down a notch. This is far more effective and much safer for the driver than relying on the box air spring to prevent overexcursion damage.
As long as you can use up all your excursion with relatively small amount of power (compared to driver's power rating) the box doesn't have to be infinitely large, there's a point of diminishing returns.
And of course if small size is a priority and you don't need absolute maximum performance it's ok to trade off size for performance.
And at some point, assuming you don't need single digit frequencies, it makes sense to leave the sealed box altogether and get into resonant box types.
Ideally you should simulate everything. Assuming you don't want to do that just sim a few different sealed box sizes in a range from very small (high qtc) to infinitely large (the lowest possible qtc attainable from any given driver). Find your point of diminishing returns, line that up against your size goals and pick a box size.
As far as which graphs to look at, look at them all. Some are very important, like frequency response and excursion. Make sure you look at driver power graph and simulate with and without the filters you will be using.
All this depends a lot on your situation too. What kind of music? Classical with it's huge dynamic range or EDM with clipped bass with sustained notes? Is the sub going to be outside or in a very small room? How far from the listening position?
If the sub is oversized for your application, you don't listen too loud and you listen to very dynamic material you don't have much to worry about, just stick it in the easy button 1.3 cu ft box.
But if you are going to stress the system very hard like most people you might want to consider the thermal issues, which are probably the biggest killer of consumer level speakers.
It will certainly sound bad. And if you push it too far there's a good chance you will damage the driver unless it was specifically made so that the suspension limits travel before the parts smash into each other and destroy the voice coil.
But again, use your ears and turn it down when it sounds bad. Don't rely on the box air spring to save the driver or you will probably blow it by overpowering. This is possible even if the amp puts out less power than the driver is rated to handle.
Ahhh okay, so I was thinking about this the wrong way. A larger box just means more efficient? Does that imply that with a 1.5 ft^3 box I don't need an amp rated at 350W? Would 200W be fine? according to WINisd, 150W would push the driver past xmaxin a 1.5 ft^3 box anywa. If not, I might just look for another driver with higher sensitivity and lower RMS.
Also, what is IB?
IB is Infinite Baffle, and I don't agree with Just a guy's phrasing concerning that.
~1 cubic foot is the sweet spot for that driver.
A larger box means less spring effect from the box and it allows the driver to move more below resonance but gives less output near resonance. Conversely a smaller box allows it to move less and gives less output below, but more at resonance 😉. That is why I said if you plan to pound on this driver with rated power all the time you should put it in a 0.5 cubic foot box.
~1 cubic foot is the sweet spot for that driver.
A larger box means less spring effect from the box and it allows the driver to move more below resonance but gives less output near resonance. Conversely a smaller box allows it to move less and gives less output below, but more at resonance 😉. That is why I said if you plan to pound on this driver with rated power all the time you should put it in a 0.5 cubic foot box.
Hi Myles,
What I'm trying to get across to you is what the others are saying. Ignore the power rating for first round selections. Concentrate on the resonance frequency, efficiency and Qt (which will determine what kind of enclosure the speaker is happiest in). If you find a woofer that has enough reasonable travel and is rated for some lower power level in your box preference, then you should give that woofer a closer look by simulating it. There is zero wrong with using a 60 watt woofer in a ported box with the f-3 of 30 Hz or lower. Also remember that your room also has a cut-off frequency, so going far below that is kind of a waste. If you look at the real specs of most "subwoofers", without EQ many do not go much below 50 Hz. A Peerless 10" woofer can bring you below 30 Hz (-3 dB point!) neglecting room gain. That is extremely low and will move air in your chest. The Peerless woofers are generally not the most efficient, but the distortion is lower.
Once you experience the output from a properly designed subwoofer running at moderate power levels, I suspect that you will wonder why the market pushes extreme power in small boxes. Besides, you do not have to generate bass in excess of the levels of your main speakers, or it becomes annoying after a while. The system should be balanced. When bass is called for it just rolls out, then disappears when that program material disappears. If it doesn't sound good playing normal music, the bass is probably turned up too high. Moderation and you will have a killer system.
-Chris
What I'm trying to get across to you is what the others are saying. Ignore the power rating for first round selections. Concentrate on the resonance frequency, efficiency and Qt (which will determine what kind of enclosure the speaker is happiest in). If you find a woofer that has enough reasonable travel and is rated for some lower power level in your box preference, then you should give that woofer a closer look by simulating it. There is zero wrong with using a 60 watt woofer in a ported box with the f-3 of 30 Hz or lower. Also remember that your room also has a cut-off frequency, so going far below that is kind of a waste. If you look at the real specs of most "subwoofers", without EQ many do not go much below 50 Hz. A Peerless 10" woofer can bring you below 30 Hz (-3 dB point!) neglecting room gain. That is extremely low and will move air in your chest. The Peerless woofers are generally not the most efficient, but the distortion is lower.
Once you experience the output from a properly designed subwoofer running at moderate power levels, I suspect that you will wonder why the market pushes extreme power in small boxes. Besides, you do not have to generate bass in excess of the levels of your main speakers, or it becomes annoying after a while. The system should be balanced. When bass is called for it just rolls out, then disappears when that program material disappears. If it doesn't sound good playing normal music, the bass is probably turned up too high. Moderation and you will have a killer system.
-Chris
Okay, I am going to simulate a few different drivers with different specs to give myself a better idea of which parameters affect what. Do you recommend peerless? Peerless by Tymphany 830452 10" XLS Subwoofer looks good.
Maybe I didn't phrase it correctly but does the simulation in a 1.5 ft^3 suggest I wouldn't need/want an amp rated at the drivers full RMS (350W) if it would reach Xmax at near 150W anyway?
Thanks again for all your time, very much apreciated
-Myles
Maybe I didn't phrase it correctly but does the simulation in a 1.5 ft^3 suggest I wouldn't need/want an amp rated at the drivers full RMS (350W) if it would reach Xmax at near 150W anyway?
Thanks again for all your time, very much apreciated
-Myles
Hi Myles,
That's what I use for drivers most often. But I am designing full range speaker systems that do not require a subwoofer. A good commercial example would be PSB's Stratus Gold speakers (the original ones). Note: I had zero to do with those, they are all Paul Barton. Excellent design.
You have a good plan, so do exactly that and you will learn what parameters are important, and also which ones are best for sealed, ported, transmission line and infinit baffle. It's interesting stuff.
-Chris
That's what I use for drivers most often. But I am designing full range speaker systems that do not require a subwoofer. A good commercial example would be PSB's Stratus Gold speakers (the original ones). Note: I had zero to do with those, they are all Paul Barton. Excellent design.
You have a good plan, so do exactly that and you will learn what parameters are important, and also which ones are best for sealed, ported, transmission line and infinit baffle. It's interesting stuff.
-Chris
Hi Myleso,
Take a look at Hornresp: Hornresp it's free, and-while it may look a little difficult at first-it's pretty easy to get started in. I'll attach a file you can Import into Hornresp w/ the RSS265HF-4 in a sealed (or closed) box (as I already had that loaded). Import the file, and click on Calculate, that should take you to a graph window, here you can select different Windows... There also is an extensive Help file.
For loudspeaker parameters try Elliott Sound Products: Measuring Loudspeaker Driver Parameters also, Wikipedia, Thiele/Small: https://en.wikipedia.org/wiki/Thiele/Small
Regards,
Take a look at Hornresp: Hornresp it's free, and-while it may look a little difficult at first-it's pretty easy to get started in. I'll attach a file you can Import into Hornresp w/ the RSS265HF-4 in a sealed (or closed) box (as I already had that loaded). Import the file, and click on Calculate, that should take you to a graph window, here you can select different Windows... There also is an extensive Help file.
For loudspeaker parameters try Elliott Sound Products: Measuring Loudspeaker Driver Parameters also, Wikipedia, Thiele/Small: https://en.wikipedia.org/wiki/Thiele/Small
Regards,
While I don't disagree that ~1 cu ft is a nice compromise between size and power performance the things I've said are still true. In the sims below you see that a small box needs 400 watts to achieve max spl while an IB needs only 20 watts. The "sweet spot" 40 liter box needs a 120 watt amp. This is a good compromise, won't lead to too much power compression and very little chance of thermal failure unless abused. But the IB is better yet, leaving no chance of thermal failure and unlikely to see any trace of power compression under any circumstances.
OP, the thing about sealed boxes is that at the very lowest frequencies you can only get so much spl (note that all 3 of the sims are limited to ~80 db at 10 hz). This is limited by how much the cone moves. If you can get the cone to reach it's excursion limits with no power compression that is the best you can do, so if you can do that with 1.3 cu ft there's no reason to go larger. Depending on what type of music you listen to and how loud you may or may not get thermal compression issues with 1.3 cu ft.
All examples shown at power required to reach 12 mm excursion.
Each example shows hornresp inputs screen, frequency response, excursion and driver power applied.
Example 1 - 14 liters (close enough to 1/2 cu ft)
Example 2 - 40 liters (close enough to 1.3 cu ft)
Example 3 - IB
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Without a doubt one of the strangest things I have ever read. I won't even bother trying to convince you otherwise because I don't have time to read your reply.
Pehaps it should be more interesting if his phrases were ponctuated by some "perhaps" or "i'm not sure" or "i'm still learning" 🙄
All you have to do is look at the driver power graphs.
I have a track that's basically equivalent to a 30 hz sine wave for the duration of the track. This is not uncommon anymore.
In the 1/2 cubic foot sealed box this track would cause the driver to consume 250 watts continuously for the duration of the track. If the driver survived to the end of the track (which is not a given) it would be exhibiting severe power compression, the power compression results in less spl and a different frequency response.
In the IB this track would cause the driver to consume 5 watts continuous, no risk of thermal failure, no chance of any power compression.
It would be interesting to see how you could explain how this is not only not fact but strange.
If you think I'm still learning these basics then please point out my mistakes.
I've got just one question.
The watt is the product of the energy by the time, your 250 number should specify a duration... could you tell me this duration ?
I input volts into Hornresp. The calculations for conversion to watts are available online if you want them.
But another way to look at it is volts referenced to the driver Re. In the case of the 1/2 cu ft box I applied 36.8 V in reference to the driver's 3.5 ohm Re.
The duration of the track is let's just say 4 minutes. I'm not going to check right now. The track has the equivalent of a 30 hz sine wave (same crest factor) for most of the duration of the track.
So you have a 30 hz signal with a crest factor of 3 db amplified to 36.8 V into a 3.5 ohm load for a duration of ~ 4 minutes. Do the math if you like, it's clear enough to me.
The problem is that I can't show you a graph of that vs frequency because the load is not 3.5 ohms at all frequencies. What I can show you a graph of is the power (in watts) consumed by the driver vs frequency, Hornresp has a graph for that as I showed.
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Lets say you are rocking out, playing some music (not test tones) at 20dB greater than 1W. Then you play your drone track at the same volume. In the small box all is well. In the IB, you will have 'no power compression' until you rip the coil loose from the spider due to overexcursion.
This design problem is more complex than modeling how much power it takes to reach xmax at some frequency well below resonance and calling that evidence that IB is better 'from a power perspective'.
That is very strange phrasing - and a very strange philosophy, seemingly that wrecking a driver mechanically is better than suffering "power compression".
There is no power compresion with an IB load.... ?
I remember a formla with joule inside.
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In the small box all is not well, you get massive power compression and possibly thermal failure if you play demanding media with low crest factor and high duty cycle at the frequencies where it draws a lot of power.
Why would you ever turn it up past the point that it sounds bad, much less to the point of mechanical failure? This is improper usage, extreme negligence and shouldn't ever happen.
If you absolutely need a limiter because you aren't wise enough to lower the volume knob when it sounds really bad, you could limit by voltage instead of box air spring. Either use a small amp (only 30 watts is required with the IB) or use a bigger amp and set your limiters or the volume knob appropriately.
Ultimate proof would lie in the measurements and the IB would win. At even moderate spl the small box would be exhibiting symptoms of power compression if pushed with enough power to near it's excursion limits, the symptoms being less spl and changing frequency response. The IB would have none of that and the main cause of distortion would be the excursion limits. When you hear this excursion limiting distortion you turn it down.
The potential to be able to wreck a driver mechanically is in no way a guarantee that it WILL be wrecked mechanically. In fact there's some pretty compelling reasons (high distortion and extremely mushy bad sound) to not ever get to that point.
On the other hand power compression ultimately limits your spl output and changes your frequency response and carries the strong risk of causing thermal failure.
I know exactly which end of the spectrum I chose to be on. I know how to properly limit a system, I turn it down when it sounds bad and I'm cautious with new media to avoid unexpected and potentially damaging surprises.
Your whole theory seems to be based on relying on the box air spring to mechanically limit excursion to avoid damage which in turn requires a lot of power to overcome that air spring and STILL won't work if you have an amp capable of exceeding the safe excursion limit.
My whole theory is that the box air spring is not necessary and the system can perform better without it due to extremely low power requirements. Of course this requires that the user is not a complete idiot and will turn it down when it sounds bad.
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