67 replies to this topic

[br85]

~thematt~, on Apr 13 2009, 12:19 PM, said:

The Glass is there. Get over it.

Instead of fighting it, try using it instead.

[orthanc]

Got to use several tweeters like the AirCirc, R2904/700000 Revs and lately Hertz ML280. Each has its pros and cons but I fell in love with the Mille tweetz. Hertz tweeters are definitely not harsh in my opinion (probably the lower models like the HSKs is a bit dynamic but certainly not bright). Now, I don't dwell too much on technicalities but on my listening experience, sometimes, reflections are good. It just really depends how well you know your drivers and your acoustic environment.

Edited by orthanc, 14 April 2009 - 10:31 PM.

[muzzy66]

br85, on Apr 13 2009, 04:20 AM, said:

And that's exactly what I meant when I said that "without a deep knowledge of acoustics, expensive tweeters are useless". "design carefully" would require that, so you don't actually disagree with me here

It all depends what you define as 'deep knowledge' I guess.

From that term, I was given the impression that you were suggesting a level of knowledge outsie that of the typical audio enthusiast (someone such as a master of physics, a sound engineer or similar).

I don't have that level of knowledge - however I have enough knowledge that I can design an install with enough thought that the benefits of a $600 pair of AirCirc's can be heard over a $150 pair of Seas tweeters.

Perhaps this was a misunderstanding on my part. I interpreted your words as suggesting that you need to be a rocket scientist (metaphorically speaking) to make these benefits useful in a car, which I don't believe to be the case.

Using a completely thoughtless approach to installation (such as throwing both tweeters into the kicks 90 degrees off axis) would probabably kill any audible benefits because both tweeters would sound so terrible that you are wasting your time spending the extra. If this is what you mean, then I agree.

Quote

You need to understand what a waveguide can do before making a claim like that. It's like saying the front baffle of a speaker box can't help you, whether it's made of glass, wood, of anything else. Fact is, it can, and so can a windscreen in a car.

I've been doing a little research on baffle / cabinet design myself lately (since I've started working on custom hi-fi designs) and while a baffle does benefit you in a way, they can have some nasty effects as well. Use of a baffle tends to help with lower frequency performance as opposed to running free-air, however in the midrange frequencies they can actually add a lot of issues. I still need to do more research to become completely clear on how this works, but something along the lines of the dimensions of the baffles (or distance of a speaker to the end of the baffle) actually causing creation of harmonics and various frequencies (dependant on the dimensions / shape). Quite a complex topic to grasp in it's entirety but a large explaination as to why a perfect frequency response on paper rarely translates to a perfect response once mounted on a baffle (and the reason for use of baffle step compensation in speaker crossover circuits, etc).

In this case however, it's a bit of a different story. We use a baffle and/or enclosure more or less because we have to in order to achieve the lower frequencies we desire out of a speaker. Without the baffle an any typical day-to-day environment, the speaker will sound worse.

Glass is different however, because we dont need it to make a speaker perform better. In a typical day-to-day environment (such as in a house or a car) a speaker will sound better if the glass were to be eliminated from the equation, and that's the difference.

Take my car - it differs to most cars because being a convertible, almost every glass (or similar) panel in the vehicle is retractable (only exceptions being the windscreen and very small quarter windows). When I open my windows I lose some bottom end due to reduction in cabin gain effects, however reflections are also minimised and the sound immediately becomes clearer. Pull down the rear window and once again, the sound improves in clarity and focus (while also thinning out do to cabin gain reductions). The more glass is removed from the system, the better the system sounds. I've mounted the tweeters in a specific angle and position such that the windscreen (the one significant non-removable piece of glass in the vehicle) is mostly outside of the dispersion area of the tweeters thus greatly reducing (if not completely eliminating) glass reflections. Once the other windows in the car go down, reflections are barely (if at al) audible. It lacks the 'balls' to be run this way in a frequent basis (with the 4" mids naturally lacking bottom end with all the windows down) but once the woofers go in this shoould become far less a factor and the system should sound far better with the windows down (how I usually drive anyway) then with them up.

As for speaker reflections being used to advantage...given the dispersion characteristics of speakers, even a driver that is 90 degress off axis should have have some of it's output signal find it's way directly to your ear. If you intentionally reflect the rest of the signal off the glass and towards yourself, then it will take a finite amount of time for that signal to make contact with the glass, be reflected, and come back to your ear. Extra time spent travelling through the air (along with the reaction caused by the impact with the glass) would assumingly also cause some (possibly significant) extra degree of attenuation of the signal due to energy loss before it reaches your ear.

Now I can only assume (I'm no physicist) but I would assume that:
1. Due to dispersion characteristics, only certain frequencies would initially make it to your ear
2. Also due to dispersion characteristics, those same frequencies would also hit the windscreen and reflect off, causing them to reach your ear not only in the initial 'version' of the signal, but also in the reflected 'version' of the signal
3. Full reflected signal would theoretically arrive at your ear some time after the partial original signal arrives at your ear, and at a reduced level of intensity
4. The portion of the wave with the greatest area of dispersion (the portion that reaches your ear naturally) would also hit the glass, and be reflected along with the rest of the signal. As such, that specific part (frequency range) of the signal would then be recieved twice - once as an original form, and once as the reflected form which is different in both timing and intensity (and possibly phase depending on how it's effected by the glass).
5. The above in theory, would then result in that specific duplicated part of the original signal seeming to be either blurry, more intense then the rest of the signal (due to variation in timing and/or summation of the signals).

In theory this could possibly be avoided by crossing the tweeter closer to the point of beaming, such that the frequency ranges that have a dispersion wide enough to readh your ear are not produced by the tweeter, hence ensuring that the reflected signal is the only one reaching your ear. However, even this may not work in the real world because:
* Even if the sound dispersion isn't wide enough of an angle to reach your ear, there will still be a relatively wide angle of dispersion as long as the speaker is producing frequencies below below the point at which 'beaming' occurs. This angle of dispersion means that sound waves will hit the glass not in one single location, but in an infinite number of locations scattered across the glass's surface (within that angle of dispersion), with the result being that rather then having a single reflected signal, there will actually be an infinite number of potential refelcted signals.
* Due to the very non-uniform shape of windscreen glass, these multiple reflected signals would hit the glass on different angles, and at different times (due to distance) casuing an infinite amount of refleced waves, each containing different ranges of frequencies (depending on where abouts they lie within the speakers' angle of dispersion), each arriving at different times (based upon the impact point's distance from the speaker and from yourself), and each arriving at different levels of intensity (also based on the impact points distance from your speaker, as well as from yourself).

Out of genuine interest, how could you possibly have a scenario such as this, and yet somehow manage to have all of those infinite number of signal variants arrive at your ear in a way such that your mind percieves them to be one single signal of a uniform intensity?

By trying to avoid the glass as much as possible, you will still get reflections but there will be less. If you are VERY careful you can almost (emphasis on the word 'almost') avoid the glass entirely. Achieve this, and you have one singal pure signal reaching your ears. The glass would be at the absolute furthest angles from the speakers dispersion pattern meaning that in theory, that the lower frequencies would be reflected, but the higher frequencies wouldn't be because they closer to the point of beaming and outside of the widest ranges of the dispersion angle (too narrow an angle for them to reach the glass). Crossover over higher may then potentially eliminate those frequencies that would be reflected allowing you to almost entirely avoid reflections.

Another pure theoretical idea I've been toying with lately..what if you ran one tweeter in the kicks where reflections are far lower, and ran this tweeter crossover just below the point of beaming (all high dispersion frequencies will come from this tweeter) and then run a second identical tweeter up in the A-pillars pointed away from the glass and at the listener, and high passed at around the point of beaming (such that only the low dispersion frequencies will come from this tweeter). In pure theory (if you could get the two playing in time and at the same intensity) you would have the following effets:
1. Reflections off glass practically completely eliminated
2. High frequencies in the kicks no effected by off axis mounting, by being blocked by legs, etc

The best of both worlds.

Now I've been throwing this idea around in my head for the last week or two and I'm seriously considering trying it, but I'm not sure how this theory would translate into the real world, assuming you could get distance as close as possble to not be a factor, and output (easy enough if you use the same tweeter, and give it the same power), timing and phase relatively consistent between the two tweeters.

Any thoughts?

Edited by muzzy66, 16 April 2009 - 05:47 PM.

[_Anthony_]

muzzy66, on Apr 15 2009, 12:56 PM, said:

Any thoughts?

Yep, if you spent the time that you'd been typing that up, you might be finished uni already

Are you assosciated with NifTiTek?

[raddeal]

muzzy66, on Apr 12 2009, 09:03 PM, said:

It depends on the tweeters.

Most tweeters above $200/each are a waste of money, because usually you can buy a tweeter for $200/pair that has better performance.

There are some rare exceptions out there however, that are the step up in price and legitimately do offer a step up in performance to go with it.

As for the acoustic problems in a car, I think that's just an excuse people use to justify sub-par sound. Just as a car environment is not perfect, neither is a house environment, and neither is a concert all acoustically. As many issues as a car environment may have, it's not the 'instant death of sound quality' that people like to belive it is.

If the individulal is creative enough, and willing to try different things, then good sound CAN be achieved in a car. The car environment isn't that bad that you can't tell the difference between a $120 Seas tweeter and a $600 AirCirc. I know this, because I use both drivers (Seas in my bookshelves, AirCirc in my car) and despite the AirCirc being in a worse environment (and the fact that the Seas is a world class tweeter), the benifits of the AirCirc are still audible. You can still hear the improved top end extension (especially off axis), and you can still hear the lower harmonic distortion above 2khz.

I think people underestimate the level of sonic performance that can be achieved in a car if you really put your mind to it. People think "forget it, it will never sound good because it's a car" and so the second they achieve 'good' performance they say "hey, this is as good as I'm going to get" and they settle - not even trying to go that little step further to achieve 'excellent'.

I assure you, that when you plan enough, prepare enough, and design carefully enough, 'excellent' sound can be achieved in a car. You won't get perfect (you can't get that anywhere) but you can get excellent.



The idea of using glass to your advantage is something I've never agreed on.

When designing a system my priority as far as glass goes is to do try as hard as possible to avoid it at all costs. The way i look at it, you will never truly get the glass within a car interior to actually help you. You can try all you want to reflect waves off glass constructively, but at the end of the day you will always have the signal out of the speaker and the signal off the glass, and the two of those aren't necessarilly going to complement each others. The reflected wave will most likely have it's phase, timing and intensity alter after being reflected, and once this wave combines with the new wave beign released by the speaker you're going to get all kinda of unpretty results.

You can pretty much never avoid glass entirely (although having the windows down, a removable rear window, and retractable roof helps) but you can reduce the effects of them by carefully selecting the position and firing angles of your speakers.

If you're throwing your tweeters straight in the pillars, firing straight across the dash, only cm from largest piece of glass in the car, then of couse you're going to get killed by reflections. In fact, you're going to get mush.

That's my 2 cents anyway



I feel like an a$$ right now, but I have to disagree with this one as well.

A lot of people out there really don't know how to get the absolute most out there components. I'm not trying to be a bastard here and pick on others either - system tuning is seriously a complex task and can require a lot of though. It's not as simple as "turn everything up and then increase the gain until the sub and fronts sound even", there is so much more to it.

For starters, in an active system the crossover point of all drivers is absolutely critical to system performance. Setting those crossovers correctly requires a strong knowledge of the actual drivers being used. You need to have an idea of the frequency response of your drivers, where they roll off, whether there are any significant peaks and dips and where they may be. You need to know about the distortion characteristics of your drivers - the Aircirc has a flat response to 600hz, but cross youd have to be a moron to cross it that low. You need to know impedance characteristics - my old Vifa's that I used for a short time had a +/- 2dB response to 1khz,but at 1khz they also had a 16ohm impedance peak that meant in the real world you'd need at least a 2khz crossover in order to clear.

Then, there is time alignment - unless your drivers share a common baffle you absolutely MUST use some form of time alignment to synchonise them. Hell even if they ARE on the same baffle, a little T/A can sometimes still be worth using to account for their group delay at the crossover point. Without time delay, the frequencies of the tweeter and mid and midbass (etc) will all reach your ear at very different times, and even if you have a perfectly flat response the system will still sound harsh and muddled.

Even something as simple as tuning in a sub (which seems like the easiest task in a system) to blend with a front stage really does require some knowledge of the sub's frequency response, the midwoofer's frequency response, the group delay of both drivers at the crossover point, the distance of both drivers, etc before it can be set with any form of accuracy. Tuning purely by ear will lead people astray the vast majority of the time, simply because every time you adjust for one thing, other things change. For example, the output of the sub may vary by a vew dB at 60hz vs 80hz vs 120hz, so with ever change the sub level may seem as if it goes out of wack...then even if the crossover point is right, you'll think it's wrong.

*sigh*

Time to get back to my assignment! (and my glass of wine)

muzzy66, on Apr 15 2009, 12:56 PM, said:

I see, I'll apply your glorious approach to life as well.

Scenario 1:
I'm sick, instead of fighting your sickness by resting or taking medicince, I'm going to use it to your advantage!

"Hey, I feel absolutely HORRIBLE today....but wait, now I can use my sickness to convince others to feel sorry for me and do things for me - HORRAAYYYYYY - if only I felt this horrible more often!!!"

Scanario 2:
I'm a soldier in a war, and suddenly soldiers from the opposing army breaches our base.

But I'm not going to fight them!!! If they capture me, take me as a slave, and torture me then that's great - maybe they'll find me when i'm almost dead and I'll get my picture in the news and become famous!!!!!

Or wait a second....maybe I'll just try my best to avoid as many of them as I possibly can, and if I'm careful enough maybe I'll get out of it with only minor injuries instead of losing two arms, one leg, and both of my testicles.



It all depends what you define as 'deep knowledge' I guess.

From that term, I was given the impression that you were suggesting a level of knowledge outsie that of the typical audio enthusiast (someone such as a master of physics, a sound engineer or similar).

I don't have that level of knowledge - however I have enough knowledge that I can design an install with enough thought that the benefits of a $600 pair of AirCirc's can be heard over a $150 pair of Seas tweeters.

Perhaps this was a misunderstanding on my part. I interpreted your words as suggesting that you need to be a rocket scientist (metaphorically speaking) to make these benefits useful in a car, which I don't believe to be the case.

Using a completely thoughtless approach to installation (such as throwing both tweeters into the kicks 90 degrees off axis) would probabably kill any audible benefits because both tweeters would sound so terrible that you are wasting your time spending the extra. If this is what you mean, then I agree.



I've been doing a little research on baffle / cabinet design myself lately (since I've started working on custom hi-fi designs) and while a baffle does benefit you in a way, they can have some nasty effects as well. Use of a baffle tends to help with lower frequency performance as opposed to running free-air, however in the midrange frequencies they can actually add a lot of issues. I still need to do more research to become completely clear on how this works, but something along the lines of the dimensions of the baffles (or distance of a speaker to the end of the baffle) actually causing creation of harmonics and various frequencies (dependant on the dimensions / shape). Quite a complex topic to grasp in it's entirety but a large explaination as to why a perfect frequency response on paper rarely translates to a perfect response once mounted on a baffle (and the reason for use of baffle step compensation in speaker crossover circuits, etc).

In this case however, it's a bit of a different story. We use a baffle and/or enclosure more or less because we have to in order to achieve the lower frequencies we desire out of a speaker. Without the baffle an any typical day-to-day environment, the speaker will sound worse.

Glass is different however, because we dont need it to make a speaker perform better. In a typical day-to-day environment (such as in a house or a car) a speaker will sound better if the glass were to be eliminated from the equation, and that's the difference.

Take my car - it differs to most cars because being a convertible, almost every glass (or similar) panel in the vehicle is retractable (only exceptions being the windscreen and very small quarter windows). When I open my windows I lose some bottom end due to reduction in cabin gain effects, however reflections are also minimised and the sound immediately becomes clearer. Pull down the rear window and once again, the sound improves in clarity and focus (while also thinning out do to cabin gain reductions). The more glass is removed from the system, the better the system sounds. I've mounted the tweeters in a specific angle and position such that the windscreen (the one significant non-removable piece of glass in the vehicle) is mostly outside of the dispersion area of the tweeters thus greatly reducing (if not completely eliminating) glass reflections. Once the other windows in the car go down, reflections are barely (if at al) audible. It lacks the 'balls' to be run this way in a frequent basis (with the 4" mids naturally lacking bottom end with all the windows down) but once the woofers go in this shoould become far less a factor and the system should sound far better with the windows down (how I usually drive anyway) then with them up.

As for speaker reflections being used to advantage...given the dispersion characteristics of speakers, even a driver that is 90 degress off axis should have have some of it's output signal find it's way directly to your ear. If you intentionally reflect the rest of the signal off the glass and towards yourself, then it will take a finite amount of time for that signal to make contact with the glass, be reflected, and come back to your ear. Extra time spent travelling through the air (along with the reaction caused by the impact with the glass) would assumingly also cause some (possibly significant) extra degree of attenuation of the signal due to energy loss before it reaches your ear.

Now I can only assume (I'm no physicist) but I would assume that:
1. Due to dispersion characteristics, only certain frequencies would initially make it to your ear
2. Also due to dispersion characteristics, those same frequencies would also hit the windscreen and reflect off, causing them to reach your ear not only in the initial 'version' of the signal, but also in the reflected 'version' of the signal
3. Full reflected signal would theoretically arrive at your ear some time after the partial original signal arrives at your ear, and at a reduced level of intensity
4. The portion of the wave with the greatest area of dispersion (the portion that reaches your ear naturally) would also hit the glass, and be reflected along with the rest of the signal. As such, that specific part (frequency range) of the signal would then be recieved twice - once as an original form, and once as the reflected form which is different in both timing and intensity (and possibly phase depending on how it's effected by the glass).
5. The above in theory, would then result in that specific duplicated part of the original signal seeming to be either blurry, more intense then the rest of the signal (due to variation in timing and/or summation of the signals).

In theory this could possibly be avoided by crossing the tweeter closer to the point of beaming, such that the frequency ranges that have a dispersion wide enough to readh your ear are not produced by the tweeter, hence ensuring that the reflected signal is the only one reaching your ear. However, even this may not work in the real world because:
* Even if the sound dispersion isn't wide enough of an angle to reach your ear, there will still be a relatively wide angle of dispersion as long as the speaker is producing frequencies below below the point at which 'beaming' occurs. This angle of dispersion means that sound waves will hit the glass not in one single location, but in an infinite number of locations scattered across the glass's surface (within that angle of dispersion), with the result being that rather then having a single reflected signal, there will actually be an infinite number of potential refelcted signals.
* Due to the very non-uniform shape of windscreen glass, these multiple reflected signals would hit the glass on different angles, and at different times (due to distance) casuing an infinite amount of refleced waves, each containing different ranges of frequencies (depending on where abouts they lie within the speakers' angle of dispersion), each arriving at different times (based upon the impact point's distance from the speaker and from yourself), and each arriving at different levels of intensity (also based on the impact points distance from your speaker, as well as from yourself).

Out of genuine interest, how could you possibly have a scenario such as this, and yet somehow manage to have all of those infinite number of signal variants arrive at your ear in a way such that your mind percieves them to be one single signal of a uniform intensity?

By trying to avoid the glass as much as possible, you will still get reflections but there will be less. If you are VERY careful you can almost (emphasis on the word 'almost') avoid the glass entirely. Achieve this, and you have one singal pure signal reaching your ears. The glass would be at the absolute furthest angles from the speakers dispersion pattern meaning that in theory, that the lower frequencies would be reflected, but the higher frequencies wouldn't be because they closer to the point of beaming and outside of the widest ranges of the dispersion angle (too narrow an angle for them to reach the glass). Crossover over higher may then potentially eliminate those frequencies that would be reflected allowing you to almost entirely avoid reflections.

Another pure theoretical idea I've been toying with lately..what if you ran one tweeter in the kicks where reflections are far lower, and ran this tweeter crossover just below the point of beaming (all high dispersion frequencies will come from this tweeter) and then run a second identical tweeter up in the A-pillars pointed away from the glass and at the listener, and high passed at around the point of beaming (such that only the low dispersion frequencies will come from this tweeter). In pure theory (if you could get the two playing in time and at the same intensity) you would have the following effets:
1. Reflections off glass practically completely eliminated
2. High frequencies in the kicks no effected by off axis mounting, by being blocked by legs, etc

The best of both worlds.

Now I've been throwing this idea around in my head for the last week or two and I'm seriously considering trying it, but I'm not sure how this theory would translate into the real world, assuming you could get distance as close as possble to not be a factor, and output (easy enough if you use the same tweeter, and give it the same power), timing and phase relatively consistent between the two tweeters.

Any thoughts?

QFL

[br85]

My hat off to you for the length of that post. that was monumental even for you.

muzzy66, on Apr 15 2009, 12:56 PM, said:

Now I can only assume (I'm no physicist) but I would assume that:

Please don't misinterpret my pointing out the obvious as rudeness, I have no desire to hate or get any hate from someone I don't know, but if you had spent the time you took to write that post researching waveguides instead, you could have saved all the assumptions. Because this topic essentially involves turning something in your car into a waveguide.

Quote

1. Due to dispersion characteristics, only certain frequencies would initially make it to your ear

Not necessarily. You can have tweeters on axis AND still using the glass to your advantage.

Quote

2. Also due to dispersion characteristics, those same frequencies would also hit the windscreen and reflect off, causing them to reach your ear not only in the initial 'version' of the signal, but also in the reflected 'version' of the signal

This is true. Not quite a problem yet.

Quote

3. Full reflected signal would theoretically arrive at your ear some time after the partial original signal arrives at your ear, and at a reduced level of intensity

If "using the glass" is actually to be done properly, the phase difference will only be a couple of degrees at the higher frequencies (completely inaudible) and fractions of a degree at lower ones (almost immeasurable) the level of intensity bit matters not, this is why we spend time picking drivers and why we pay for the eq feature.

Quote

4. The portion of the wave with the greatest area of dispersion (the portion that reaches your ear naturally) would also hit the glass, and be reflected along with the rest of the signal. As such, that specific part (frequency range) of the signal would then be recieved twice - once as an original form, and once as the reflected form which is different in both timing and intensity (and possibly phase depending on how it's effected by the glass).

If done properly, this difference is insignificant, and in fact, can often be considered a major gain advantage with almost no phase and time disadvantage (none at least, that is audible)

Quote

5. The above in theory, would then result in that specific duplicated part of the original signal seeming to be either blurry, more intense then the rest of the signal (due to variation in timing and/or summation of the signals).

Only if the tweeter is more than, say, 5cm away from the glass, which most of us aren't going to go out of our way to do.

[Pulse-R]

The idea of the wave guide, is to 'guide' the 'wave' onto any useful surface nearby (glass, or dash) and away from things we don't want (too much glass, or glass too far away.

although, some side-reflection does help with stage width, it's better diffused a bit to 'de-localise' the reflection, hence creating more ambience...
in this regard, we can put some 'treatments' along the side edge of our wave guide to control the dispersion better.

[muzzy66]

br85:

I did actually begin reading the thread you posting regarding waveguides, however after the first few posts I had to put it aside and get back to my assignment (as hard as that must be to believe giving how long i spent writing that last post lol).

Just submitted the assignment, but now have to go over notes for an exam i have tomorrow morning so i still won't get a chance to read through it - it never ends!!

Alas my apologies also if my response to you soundedin any way rude or arrogant - It wasn't the intention, but some of the things i just straight out said because i was too lost in thought to concentrate on how to make it all sound polite

Apologies to theMatt as well, as the first part of my response was a little 'sarcastic' in tone. I was a little stressed about my assessmnts and was a little low on patience, but i've edited that out now anyways.

_Anthony_, on Apr 15 2009, 05:29 AM, said:

Are you assosciated with NifTiTek?

My brother created the business, so given that I live with and share his passion for sound, I more or less became associated by default

Edited by muzzy66, 16 April 2009 - 06:06 PM.