DevilDriver

Didn't do it on CSo, why ruin our expectations?

If amplifier A makes 1kW at 12.6V and amplifier B makes 1kW at 14.4V, amplifier A will likely provide more power at all system voltages.

It's true. Feelin' Springy

Go down to 2.0 cubes even and you'll be fine. Thermal power handling is not the issue here; it's keeping it within mechanical limits.

Poly with shorting ring and/or copper sleeve?

Well I guess its better to have a larger active core, than a huge inactive member base. Agree 100%. It's more valuable traffic. 10,000 members who hog server bandwidth and provide zero capital (whether that is of a knowledge or financial basis) are worth very little. I mean, digg.com is a perfect example of this: they are closing in on a million members and are a top 100 site on Alexa. However, their membership has high churn and the majority provide little value to the website; as such, they are still unable to get into the black. Their server bills are huge. For the Diggnation podcast, CacheFly streams 25TB per week for them.

Hopefully. For what it's worth, this is the most active forum I have seen for the number of registered members that are here.

I'd probably just leave him to his vices.

Dude.... Ava 15's.

Ok, let's think about this for a few moments. First, let's try to avoid telling someone that they're not welcome in any threads. Take the advice given or discard it: it's your choice. At the same time, we want to try and keep things friendly here, so if you have an issue with any member, it's probably better to hash that out in pm's, mmmkay? Now on to the fun part... First, let's define what we mean by "rear fill". In a traditional sense, this would be a set of speakers in the rear of the vehicle that cover all frequencies already predominantly handled by your front stage. A more current definition seems to be any set of speakers in the rear of the vehicle, whether this be handled by a highpass, lowpass, bandpass, or allpass filter. It's safe to say that everyone who has posted in the thread is relatively familiar with both sides of the coin, but I'll mention it for a moment anyways. I'll be very clear in saying that I never, ever, ever use rear fill. As an engineering student, everything I do is based on the laws of physics. The concept, if you're not familiar with it, is that of constructive and destructive interference. Constructive interference occurs when two interacting waves at a given frequency result in an increased amplitude at any point in the period we are analyzing. Destructive interference is just the opposite: the interaction of the two (or more; this can be an infinite number) of waves results in a decreased amplitude. These increases and decreases is a result of the phase of each wave. If the coinciding waves are in phase, we will experience an increase in amplitude. If the coinciding waves are out of phase, we will experience a decrease in amplitude. Perhaps a visual will help here. The example on the left shows two waves, in phase on the bottom, and their summation above. The example on the left shows two waves, out of phase on the bottom, and their summation above. So how is this relevant in a vehicle? Quite simple. Assume speaker A and speaker B are wired identically. From a relative phase standpoint, they are in phase. That's great. But what if these speakers are placed in areas that make them not equidistant to each other? Let's assume for a moment that speaker A is 2.5 feet away from your ear and speaker B is 3 feet away from your ear. Let's assume each speaker plays a 1000 Hz sinusoidal wave. To complete one period (or one full wavelength), the sound pressure from each speaker must travel approximately 1.2 feet. Speaker A will complete approximately 2 full periods (2.5/1.2=2.08). Speaker B will complete approximately 2.5 periods (3/1.2=2.5). At this point, the speakers are in fact, out of phase, in an absolute sense. Here, we're experiencing destructive interference. Simply put, we're seeing nulls in our frequency response that shouldn't be there. This just isn't a good thing. But it's much worse than that! Sound is directional and gives directional cues. A speaker in the rear sounds like a speaker in the rear, believe it or not. It will undoubtedly pull your sound stage rearward, which is never a good thing from a matter of accurately reproducing music. But... There are in fact logical and understandable reasons for using "rear fill", no matter what our definition of this is. When was the last time you could easily fit a large format midbass driver with considerable output in your kickpanels or doors? A little discussed fact is that high midbass output down to 40-50 Hz is one of the big differences between award winning sq vehicles and "also-rans". In fact, you'll find this fact to be demonstrated frequently throughout car audio history. Richard Clark's Buick Grand National had midbass in the rear. Harry Kimura's best sounding vehicles have had rear midbass; in fact, almost all of the best sounding Speaker Works vehicles have had midbass in the rear. There is in fact, empirical evidence that midbass in the rear works because the directional sacrifices that are made are overcome by the presence and output of the midbass. This is just one legitimate reason. Second, any rear passengers in a car will have a very hard time experiencing the front sound stage that you worked so hard to perfect. The vehicle is a horrible listening environment if you're trying to please multiple people: stuff gets in the way. Give your rear passengers a chance to experience the music in a relatively decent fashion: add some rear fill. Even if this is a considerably diminished presence in the rear, it does give something to the passenger. Heck, maybe you've been to a concert where you heard sound reverberate off the back wall and you're wanting to duplicate that. Lastly, rear fill can be an easy way to make some improvement with very little effort. There's no need to EQ, Time Align, or change positioning of your drivers if adding a couple speakers in the rear deck brings a little more height to you. Sure, this isn't a great solution, but it's easy and that's good enough for you. Or maybe you are one of those weird bass heads who packs 8 18" high excursion drivers on 10 kW in your vehicle: adding a couple of speakers may help add some SPL to your frequency response at certain frequencies. In general, it is safe to say that "rear fill" is not an absolute or technically correct solution when aiming for the most accurate reproduction. At the same time, some people do, in fact, prefer it for a reason. I think it is well worth educating someone on why you may or may not disagree on the use of rear fill, but perhaps there is a more appreciated way in which you can convey your opinion without telling someone their desires are wrong or why their advice is unwarranted.

947,xxx

Board Statistics Our members have made a total of 231,076 posts We have 2,124 registered members The newest member is Chad Kuypers Most users ever online was 239 on Feb 2 2005, 01:57 AM

Greetings.

Surprised that I haven't seen this before. If it's a subwoofer, something similar to the RE8 is a great idea. Was there anything special about them? Not at all, but they were extremely affordable. An 8" driver with a decent motor on it is almost always going to be very efficient and require a small enclosure. To me, put something together that you will sell for less than US$50 w/ a 2" diameter vc that can take around 200 watts. Get enough BL to drop Qts/Qes below 0.3, and you've got a winner. For a midbass, it's a bit of a different story. To me, an 8" midbass in a car must must must be able to play up to at least 400 Hz and down to at least 60 Hz; that allows me to use a 3" midrange with wide bandwidth and a very small tweeter with a very high frequency highpass filter. How is this achieved? It's mostly a balance to be found in coil length; it takes Xmax to get sufficient SPL at 60 Hz that will make your transition to sub-stage smooth. Thankfully, an 8" driver does not need excessive Xmax to be able to do this in most instance (Xmax on order of 8-10mm is certainly adequate). It's very critical that the coil is long enough compared to the top plate to achieve the linear excursion you are looking for, but also equally important that it is short enough that inductance (and inductance variation) does not become much of an issue until the second or third harmonic above the fundamental frequency that you wish to begin your lowpass filter at. Adding a shorting ring would really be something, maybe a full sleeve of copper... I think you have to look at the market looking for 8" midbass in a 3 way design: they are SQ oriented. I don't feel that making an "average" driver would be worth it here. Long and short: making an inexpensive 8" driver with minimal work can give you some very appreciable returns. If doing an 8" midbass, I think you have to do it right to really make it worthwhile. Just one guy on a soapbox.

:lickscreen: this is top secret intell at this point, Which is as much of an answer is needed, lol.

I've got wood. And clipped to that piece of wood, I have a sheet that says I'm excited.

Heh, knew it. Good addition Aaron.

Nah. 12" and 15" to start, then 18" if there's capital for it. My opinion, of course.

The speaker cone is one of those wonderful engineering challenges where hundreds of materials are tried in an effort to achieve the perfect result, which has been known for quite some time. For the most part, the ultimate goal is something light, stiff, and porous. Light is good for efficiency, stiff is good for keeping modes to a minimum, and porous is good for providing damping (again, keeps modes to a minimum). Any modes would ideally be absorbed by the cone's inherent damping it provides. It has been quite challenging to find a single material that is capable of meeting our desires, so this has lead to a large number of composite cones being designed. I'll try to mention the differences between some for just a moment. Paper - Paper can be a very good material. It's stiffness to mass ratio is very appealing and can provide adequate damping. Due to the nature of paper, it is very easy to adjust the number of fibers or strands to increase weight (good for lowing Fs) or decreasing mass (good for increasing efficiency). It can be a very flexible product. At the same time, paper that goes untreated is not particularly durable, which you likely noticed when you were 3 years old. Popular treatments include adding a layer of carbon fiber treatment over the paper cone or coating the paper cone with glass microspheres. The latter is known as "PolyGlass", which you have probably seen on some Focal drivers (I believe it is a Focal proprietary technology). Paper (and it's various treatments) also makes for a highly affordable cone. Polypropylene - PP is a good alternative to paper and is growing increasingly popular. PP has a natural stiffness to mass ratio that is often lower than desired, so it is not uncommon that it is reinforced with various fillers to raise this ratio; fillers include kevlar, carbon fiber, talc, mica, and acrylic. PP is also pretty affordable and has good internal damping. Aluminum - Decent stiffness to mass ratio (fairly light material with good efficiency), but the big issue with aluminum has already been mentioned: nasty resonance due to a lack of internal damping. This creates noticeable breakup modes in most midranges or tweeters. It's still a common material to use in subwoofers, as any resonance will come outside of the typical passband. An issue experienced by a certain OEM was that, like all metals, aluminum can fatigue, which will can cause big issues in high excursion where the cone meets the surround. Magnesium - Very similar to aluminum. Magnesium is even lighter and has even less internal damping, leading to the same issues with resonance and breakup modes. It's worth mentioning that both magnesium and aluminum can receive a thin rubber treatment to help increase damping. Kevlar - Kevlar is extremely stiff and common in body armor; it presents a very appreciable stiffness to mass ratio. However, it also lacks damping and can experience noticeable resonance. For these positive and negative aspects, kevlar is more common in composite cones rather than being the primary material used. Carbon Fiber - Much like kevlar, carbon fiber is more popular in composite cones or as a paper coating. It displays a good stiffness to mass ratio with better internal damping than kevlar. Carbon fiber is very flexible in how it can be applied, so it makes for a great material in a composite cone during the engineering process. It's use as a primary material in cones hasn't really taken off at this point. Hemp - Hemp is a relative new-comer to the cone material world. There isn't much experience to be had regarding hemp cones, although they are used exclusively by Hemp Acoustics and are growing increasingly popular. Hemp has a good stiffness to mass ratio and demonstrates good upper frequency and low frequency damping. It is also a versatile material and has been used in composite cones in the past. All other cones are usually based off of these primary materials. Some are a combination of the above, while others take the above and add treatments. There are a couple others I have never come across, but know exist, including diamond cones (yes, they're out there) and various pulp based materials (including banana). Hope that helps a bit.

Greetings Mike, The subwoofertools code has led to some rather inaccurate and unfortunate builds. I seem to recall a box that turned out quite terribly on caraudio.com and I personally would not recommend it. As to the port area conversation, it does, in part, relate to Xmax (which is noticeably different than xmax ). When creating a simulation, you should not be adjusting Xmax in anyway to compensate for any port length required for a given amount of port area. To the original poster, I'm just looking for clarification. Are you looking for a program that can produce a cutsheet? Looking for a CAD (or similar) rendering of the finished product? Or are you wanting a program to simulate speaker performance? For creating a cutsheet or cutlist, you can use the open-source program CutList. The executable is available here. For creating a visual rendering of sorts, I suggest SketchUp. You can grab the free version here. For enclosure simulations, there are a number of solutions available. Off the top of my head, I recommend UniBox or Brian Steele's spreadsheets. If you're looking at more complicated enclosure design (ie. horns or TL's), you can utilize the MathCAD sheets at MJK's site. Cheers.

I think in the next 2-3 months. That's the last thing I remember hearing a couple weeks ago.

It was a good movie, but I felt like I was watching it with idiots. Lots of people did not "get" some of the subtle jokes, ie. Kenny G, the Kennedy and Monroe relationship, or any of the subtleties. Good movie though.

Evergreen Terrace - Zero Good metal cover of the Smashing Pumpkins classic.

Trophy Scars - Jerry's the Name, Sociology's My Game

This is a great shot (yes, I realize it's from the first batch):