DevilDriver
-
Content Count
2,429 -
Joined
-
Last visited
-
Days Won
1
Posts posted by DevilDriver
-
-
The W7 is not always the best value but is always one of the top performers, surviving a decade filled with subwoofers designed to knock it off its perch. I've never used an Xcon but I'd never turn down a W7 at a price I could afford.
Just because a product is mainstream doesn't mean it is any less deserving. Buy the best product that fits your budget.
2 -
Bottom line is that the prohibition of something so physiologically harmless would just add to the business of the violent black market that prohibition has already created. It's also a question of liberty.
0 -
Don't pay $400 for it. You can find Brahma's for less on caraudio.com, or you can buy similar products from Exodus Audio or Creative Sound Solutions.
0 -
having a very large permenant magnet AND lots of metal, and a tight gap means more power, more efficiency, and more power HANDLING as well... but cooling becomes an issue.Having less metal, larger pole vent, decreases efficiency, decreases BL, but increaes cooling... so less overall power handling, but handles things better for longer periods of time.
The burper handles lots more power but short term, the SQ takes less but for longer periods?
Having a large magnet means you have a lot of potential flux in the system. You must have enough steel to carry the flux while still making sure the steel is saturated (ie. can't carry any more flux). Air has greater reluctance (resistance to carrying flux) than steel, so keeping the gap tight ensures you have the most flux possible in the gap (since the coil is closer to the steel). Any time you're able to increase BL, you're able to increase efficiency.
There is no strong correlation between the amount of magnetic material in the motor and the power handling of the driver (note that talking about power handling and cooling is essentially the same thing). The steel in the motor does play a role, but the dominant factor is always the coil. The goal is to get the heat off the coil; in the past, the idea has been to get as much air moving in the motor as possible, which is, in part, one of the reasons the pole vent has been used. In reality, we just need to get the heat off the coil, so moving it anywhere else will be useful. So instead, you have a lot of steel in the motor, add some copper or aluminum shorting rings, and design the motor such that air is drawn down into the top plate, over the windings, and then passing the heat into the shorting rings below the gap or into the steel above the gap. The pole vent is still useful for relieving pressure under the dustcap, but it is best to keep as much steel as possible, in my opinion.
Keep in mind that another dominant factor in efficiency is the mass that is being moved (Mms).
So now to bandwidth/inductance/Le (same thing?)The SPL beast has longer coil, raising inductance, decreasing high end extention/bandwidth... more peaky responce.
The SQ has shorter coil, less inductance, smoother/flatter responce, higher extention, wider bandwidth???
The longer the coil, the greater the inductance. Since the inductance and resistance of the coil acts as a first-order (6 dB/octave) low-pass filter, it is preferable to have inductance that pushes the corner frequency (at which response begins to roll-off) above the bandwidth in which you'll be using the subwoofer. For SPL, you typically want a lot of windings in the gap (for both power handling and BL), so inductance is often higher.
0 -
x = x0 + vt
x = 4"
x0 = 0"
t = 1 second/30 cycles = 1s/60
Solve for v. I divide the time by 60 as there are two 4" movements per cycle; as an alternative, you could set x to 8" and leave t as 1s/30 cycles.
As I've mentioned several times, Le is the dominant aspect of transient response, while Mms (and other factors) play a lesser role. Note that there is a relationship between the time domain and the frequency domain.
0 -
Can I ask you guys why you bought DD buds and not someone else?
0 -
I think the point is mostly that the number of slugs is irrelevant. We can take about how tall the stack is or how wide, but using the number of slugs stacked tells us nothing at all.
The most important thing about the magnets is that they saturate the steel with flux. You can use stacked magnets to gain more clearance (which is easier from a production standpoint), but all that really matters is that the magnets saturate the steel that your project requires.
0 -
Board color and heatsink shape are the diffrences as far as I can tell from the pictures. 90% sure they share the same components.Id like you to buy the AQ2200 and do an actual comparison with the BXI 2607.
Someone needs to do this atleast.
What about a drop in comparison between 9500s and BTLs. I say that needs to be done before anything can be said.
And which one of DD's fart cannons are you going to compare with the Fi Q since the thread is comparing the two companies?
Has DD ever made a SQ orientated sub?
9100's are supposed to be (underhung), but there is no evidence to confirm that they are.
0 -
Basically, his point was this:
Speakers are highly inefficient.
A moving speaker generates back EMF.
The counter-voltage that is induced (back EMF) subtracts from the voltage supplied to the windings.
Now because of how inefficient a speaker is, the suggestion is that the counter-EMF is especially problematic with low current inputs. This is, to an extent, true, but you must remember that at high-outputs we also lose output from non-linearity and thermal power compression. To be clear, I don't believe in this fallacy of "it requires X amount of power to get moving", and will not until someone shows evidence to the contrary. I have seen several measurements of a particular speaker's response vs frequency vs amplitude where output doubled with every doubling of power up to about 400 watts, after which the increase became increasingly small. If your theory were to be true, I would expect to gain maybe 1-2 dB for the first few doublings, then closer to 3 dB, then falling off again after that, which I simply have not seen.
Further, it is an inductance-related problem (though not necessarily solvable with what we're doing now). More on this a bit later.
0 -
Are the mids the newer ones with Split Coil topology, or the older XBL^2 drivers?
Either way, you'll be limited to the 1.7-2.0 kHz region on the mids. Where you cross the tweeters over will depend on where you position them and level differences. You will likely have to scale back the power on the tweeters a bit, both for safety and a smooth crossover. You'll probably have to underlap a bit.
0 -
The "sound" argument is greatly confused by our rather imperfect ears or, more specifically, our rather imperfect brains. :So you are saying that folks who hear differences in various amplifier topologies, have either bad hearing or not very smart?
What I'm saying is that ACTUAL differences between amplifiers are completely quantifiable...there is no magic pixie dust.
Now, in terms of interpreted differences, I am saying that our ears and brain are not very smart. We have very poor memory for sound, and are unable to distinguish what is actually driving a difference between a variety of physical properties. We don't hear what happens with each component in the chain separately...we hear their summation. Even then, we are often unable to determine when a change is favourable or unfavourable (if the goal is accurate reproduction): instead, we hear how it relates to a personal preference.
This is, of course, ignoring the whole philosophical argument of perception. We can only understand and compare against what we already know...what we've already perceived. No person here has ever heard a system that was a perfect reproduction of a song, and it is doubtful that we were there for the original production of our recordings; as such, it is impossible to state with a high degree of certainty using only our ears what level of accurate reproduction the system is achieving.
0 -
And you think CEA compliance means something? That requirement is a huge joke as well.Tell me more. I haven't met anyone with a complaint about them...
Well for starters, the RF T15k gained CEA compliance even though it doesn't do near the continuous power it is rated for.
0 -
The Havoc does it all! Lots of output, razor sharp SQ, looks good, doesn't cost 4 figures, and is very reliable. But I've always felt that the 2 cu ft ported box was a little big and put a little too much emphasis on the low end. The sub will get low, the question you should ask is how much do I need from 65hz+.Just wondering what you meant by this statement. I have been finding a ton of drivers I have been using lately sealed, will not get above 63hz. I need something that will get to around 72hz. Is this possible with the Havoc? Also, I think I have asked this before, but do you know the Le?
Keep in mind....the enclosure behaves as a highpass filter; with both sealed and bass reflex (ported) systems, the enclosure only has an effect on low frequency performance. If you are having a perceived problem with upper frequency performance, you need to address the vehicle acoustics by eq'ing down the bottom end or by selecting a driver with less inductance and inductance variation.
0 -
I'm not completely sure I understand what the guy you spoke with is talking about. Can you get him to expand on it a bit?
No, not all amps sound the same. Mind you, all amps that measure the same (whether that is by default or as a result of modification) will amplify the signal in the same way, and thus will often sound the same. The "sound" argument is greatly confused by our rather imperfect ears or, more specifically, our rather imperfect brains.
Note also that there is no such thing as "RMS" watts. RMS current, yes....RMS voltage, sure. But what we're really talking about is average power....average watts.
0 -
i think we should get a fantasy football league goin on here with the main hop visitorsNow that is a good idea.
0 -
I would venture a guess that Dan doesn't care that much. The Adire split was bad....if I were him, I wouldn't waste my time making a legal case....just more mess. RU has the parts now and at least they're staying (relatively) true to their purpose.
0 -
CA.com isn't that bad. This forum vs. forum stuff is junk, in my opinion.
SSA is a whole different world, and I suppose that's something to be proud of. For me, there are less opportunities for educating here as of late (whether that be audio related or something else...say...maybe US politics) and that is just the nature of each site's traffic. I read maybe 2% of the threads there, but they usually leave an opportunity to help another person.
It is hard to keep telling people to read the enclosure and power recommendations on Fi drivers somedays.
0 -
Can I make any guesses on what that piece of paper is covering in the gap? From the rear of the driver, I think I like the direction your cooling approach is heading.
0 -
I remember reading this before but it was a different post and bl was buzz lightyear but i cant remember ssd or btlI could care less about what means what, but I think the source for the BL's name is hilarious. Mind you, I've heard there is something interesting about all the names Scott has had for Fi and when he was with RE as well.
0 -
Sorry, I think I've been missing a key part of your question: does Audioque offer the HDC3 with either copper or aluminum coils? If that is the case, I would probably just get the aluminum coil since the copper coil will likely add significant mass to a driver that will already have enough low frequency extension for most. For your purposes, the aluminum coil is probably preferable.
0 -
The setup you have listed should be manageable. I was mostly speaking from an engineering standpoint. For most consumers, looking at individual aspects (like voice coil material) is a pretty fruitless adventure.
0 -
Aluminum tends to dissipate heat faster.Nope. Copper is 1st, then Aluminum, then Stainless Steel.
Yes, this is something that is a bit misunderstood. Forgive me, as I have hardly studied thermodynamics, but....
Thermal conductivity refers to how well an item conducts heat. On the other hand, we also have Newton's law of cooling. I will save you the math, but the general premise is that the greater the difference between the body and its environment, the greater the rate of heat loss for that body.
Simple conclusion:
1) Copper is a better conductor of heat than aluminum. As such, copper can get hotter, quicker than aluminum.
2) Because copper can get hotter, quicker, it also presents a larger difference between the temperature of the body (the copper) and the temperature of the environment. As such, copper cools more quickly. This is the "dissipating heat" part that was referred to.
With a speaker, the material chosen will vary depending on what you (as an engineer) seek and the geometry of what you end up using. In some cases, copper will be more preferable....in others, it will be aluminum. Or, for those who prefer, you could do Copper Clad Aluminum or any one of the less popular alternatives.
0 -
It would be sweet to have a HT sub as a 21 inch. But there are no recommendations for enclosures. Would anyone have any idea how big of a sealed box this 21" would need?0 -
Pole vents are useless..I see the BL has vent holes at the sides all around. But how do other subs do their cooling since they do not have side vents but only pole vent? i believe that is the conventional way of cooling the voice coil
First, let's just think about how a pole vent would help cool the driver. It would have to either draw cool air up or push hot air down. This will work in either of two ways:
1) The heat from the coil is absorbed by the pole, then air traveling over the inner wall of the pole piece carries that heat out of the pole.
2) The heat from the coil must manage to get off the coil, through the former, and down into the pole piece, at which time you count on convection to take the air out of the pole.
If you think about this logically, I think it should be very obvious that either approach is not going to do a whole lot. In fact, if #1 is the preferred method, then a smaller pole vent is often preferable because you can achieve higher air velocity and there is more steel to absorb the heat (steel absorbs heat a lot better than air does).
So what is a better approach? Firstly, I think there are a few things that we should target.
1) Get the heat off the coil - It should be easier to move heat off the coil and into another region with increased air velocity. What you really need to find is the balance between air mass and air velocity, at which the most heat can be removed from the coil. The pole vent is generally a low velocity, high mass method of moving air and is not particularly effective. The method we will review is more of a high velocity, medium mass approach.
2) A short path to move the heat along - Obviously the shortest path will be the most effective.
3) A place to put the heat - Once we have moved the heat off the coil, we want to move it to a place that will be absorbed.
The approach for many is to try and move this into the surrounding atmosphere (ie. the air in the enclosure), but as I already mentioned, the air is not very thermally conductive. Some clever engineers use deposits of aluminum or copper in the motor to absorb some of the heat; for the sake of comparison, the aluminum is about 10,000x more thermally conductive than air, while copper is about 16,000x more thermally conductive than air. How thermally conductive the steel is in the motor will depend a lot on the grade, but it is always much more thermally conductive than the air around it.
Anyways....
The pole vent approach is just dumb. First, you remove steel from the pole: the pole is just a short jump from the coil, and is also a good place to put heat. Not only that, but removing steel means you have less steel to carry flux and, potentially, lower flux density, lower BL, lower efficiency, lower SPL, etc. Second, you have to move a large mass of air quite a distance (from the top of the pole out the vent). Ask yourself: if the goal is to move the heat into the surrounding atmosphere, isn't there a shorter path we can do this with?
Hopefully the answer is obvious: yes! Hell, the coil (which is where the heat is coming from) sits just a few cm from the surrounding atmosphere if we go up through the top plate instead. We can also avoid taking steel out of the motor (which is good for all of the above reasons), and the steel top plate and basket (of whatever material) are right there to absorb heat as well. So we've found narrowed down a more effective path and an equally (or more) effective place to put the heat.
In order to get the heat off the coil, we are going to want to draw air at a high velocity across the top plate and down into the gap (where the coil resides). Via convection, we can now pass heat into the steel pole piece, the surrounding magnets, the steel top plate, or draw it back out of the gap and into the basket (or, to a lesser extent, the surrounding atmosphere). We can also add aluminum or copper inside the motor to provide even more mass to absorb the heat (a thick copper or aluminum ring on the ID of the magnets might be quite effective). To make the drawing of air into the gap most effective, we can add a spacer between the basket and the top plate; we can also machine channels through which air is drawn down into the motor. The size and shape of the channels will vary for the application, but this is a very effective method.
What I have described is, in essence, exactly what Fi is doing. There are a number of small tweaks you can make (adjusting the geometry of the pole or the top plate), but this is way more effective than the traditional pole vent method. In fact, if moving heat out of the rear of the motor is your goal, it is often better to utilize a series of holes drilled into the back plate that allow you to vent heat out of the rear of the gap (rather than out of the pole).
Other companies are starting to figure this out (very slowly), but the vast majority do not do this (or even understand it). Part of the problem is that consumers don't really understand it either, so we have the blind asking for the blind to give them something neither of them can see (metaphorically speaking). That's why it is so important to share what we know with others.
0
MP3s, how and why they affect our systems, and system choices
in Technical Info & How To's
Posted
CD vs mp3
Here's a comparison of the various LAME settings. I use v0 or v2 for anything lossy (the majority of my collection is in FLAC). You see that v0 is quite a bit smaller than 320kbps CBR but about as good.