Just another question for myself lol
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Gold Member Username: SubfanaticWalton, Ky Post Number: 3795 Registered: Dec-04 | im wondering, can u mix different subs with different ohms??? cause i know when a sub says its dvc 4 ohm, its can be like 4.2 or 3.8 or somen and not exactly 4 or whatever. But im wondering that, then this as well. IF you can do that, can u mix like a DVC 4 ohm sub and a DVC 2 ohm Sub, or a SVC 4 ohm and a DVC 4 ohm, or a SVC and SVC 2 ohm, or does everything HAVE TO BE THE SAME, if u can mix these, can someone please give me a quick little list of how these examples i said would end up in ohms |
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Gold Member Username: FishyTamarac Ft.Laud, FL USA Post Number: 1364 Registered: Sep-04 | You can, but it may sound like @$$. Even two subs with the same diameter and nominal impedance but different TS parameters won't sound good together. Heck even even two of the same subs isn't as good as just one for SQ. No two drivers are identical. Now whether the average Pyramid/Rockwood/Boss/Pyle of poopoo lover would notice a difference or even care if he did is another story. -Fishy |
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Gold Member Username: SubfanaticWalton, Ky Post Number: 3803 Registered: Dec-04 | ok well fishy lol, the reason i ask is because i have A TON of ideas, and if you have noticed i have a ton of subs and amps and stuff and im thinking about buying this van down the street and wiring like all my low rms subs to a big amp so i can use 1 amp for all the subs instead of 1 for each pair or single sub |
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Gold Member Username: FishyTamarac Ft.Laud, FL USA Post Number: 1365 Registered: Sep-04 | Ok while searching for an explanation(for me as well as you) of why two "same size" subs with different parameters make for a poor listening experience I came a cross a good passage that helps explain things some. Don't worry about trying to fully understand the concepts. I'm having a difficult time myself and I've had the benefit of a number of wave mechanics as well as 3 acoustics courses(lotsa sonar stuff) while studying Ocean Engineering. Anyways this is from the simplest and smost straightforward article I've found which doesn't involve pushing a Brand X Speaker. Most of the stuff I found while googling was simply full of a bunch of pseudoscience babble aimed at promoting a specific product. Well anyways the article deals with much more than just the subject at hand, but here's a quote that demonstrates how the relative phase diffrences between unlike drivers playing at the same frequencies COULD result in poor SQ. The important stuff is in bold. Phase Audibility The audibility of absolute phase is nil. I must explain this further, as this is a somewhat contentious issue. It can be proven in ABX tests that there are some signals where the difference between a non-inverted and inverted signal is audible. Certain waveforms and instruments are highly asymmetrical, and if listened to in isolation will sound different if the phase is reversed. The difference is not subtle, either - it can be very pronounced. This is much more likely to be a result of loudspeaker driver behaviour than anything else, and the "correct" phase is anyone's guess - should it be inverted or not? We don't know the answer, since we will be unsure of what the instrument sounded like "live" - it is possible that neither the inverted or non-inverted recorded signal will sound like the original, so the point is moot. The key issue here is that if we listen to a saxophone (a good example of an asymmetrical waveform) with the phase normal then reversed, all we hear is a difference - there is not necessarily a "right" or "wrong" phase, since it depends on the way the instrument was miked in the first place. If the period between listenings is extended to a few minutes, the chance of us hearing the difference will be minimal, and we still won't know which is "right" and which is "wrong" - all that this proves is that there is a difference, and it only becomes audible with some instruments. This is probably the only case where an ABX test proves something that is not relevant in the general sense - so yes, absolute phase can be audible, but it is (generally) irrelevant. [Update added 30 Jul 2002] The net result is that our ears do not care if there is a slight misalignment between the fundamental and harmonics of any instrument known. This is likely to cause howls of protest from people who won't actually bother to read this article in its entirety (if at all), but it has been demonstrated a great many times, and by various techniques. Example: Let's examine this from another perspective, using live sound as the source (for example, a string quartet). Regardless where you stand or sit, you will most likely be a different distance from each instrument. One could insinuate oneself into the very centre of the performers' space, but this is more likely to lead to your eviction from the venue than to improve your listening enjoyment. If one is a different distance from different sound sources, then the absolute phase of those sources will all be different too. Not only that, but the phase variation changes with frequency. At 40Hz, a two metre difference in the relative path lengths amounts to only about 42° phase shift, but the second harmonic is shifted by almost 84° while the 5th harmonic (200Hz) suffers 208° phase shift. Move a little, and it all changes. Do we hear a huge variation in the sound (assuming a reasonable listening environment)? No, of course we don't. No-one will ever convince anyone who has been to a live performance that there is one (and only one) specific location from the musicians where the sound is somehow "right" (ignoring major auditorium problems, of course). The fact is that phase varies with distance and frequency, and this will not change. The complex nature of music using real (as opposed to synthesised) instruments guarantees that things will drift in and out of phase as a matter of course. Yes, the loudspeaker should be able to reproduce this as accurately as possible, but there is only science in the design of a loudspeaker system - no magic. A simple all pass filter will shift the phase of an audio signal by 180° over a frequency range determined by the component selection, and it is completely inaudible - provided the source is music, and provided the phase sweep is performed slowly enough for our ears and brain to make the necessary adjustments. In fact, I have demonstrated this as the filter is adjusted (very slowly), and the sound quality remains the same. Nearly every (Ok, not nearly - every) recording ever made has been recorded using a microphone, had some equalisation applied, and/ or has had some additional treatment in the recording process. All of these introduce some degree of phase shift, but does it ruin a good recording? No. As the signal emerges from the vast majority of crossover networks, there are huge shifts of phase, as has been described above. A square wave subjected to phase shift still has all of its harmonics present, they are just slightly misplaced in time. The sort of delay we will experience is dependent on the frequency, but it doesn't matter. Vented speaker boxes do "awful" things to phase, as do many highly regarded "feedback free" single ended triode (SET) amps. Any equaliser, be it a constant Q graphic, parametric, or just a simple tone control, will introduce phase shift as well as equalisation. The phase of a waveform changes as you move about - but your best friend sounds like your best friend regardless of your relative positions in a room, even though there are massive changes in phase as we walk around. If we believe the "absolute phase" lunatics, this would not be the case, so your wife may sound like your wife in one part of the room, but sound like the milkman in another. We all know that this doesn't happen - the tonal structure of a sound does not rely on the phase integrity of the received sound, only the relative amplitudes of the fundamental and harmonics. So a speaker that has perfectly flat frequency response but is not 100% phase coherent will sound the same as one that is also flat, but totally phase coherent. This does not include colouration caused by the cabinet or drivers - of course these are important. Assume the same enclosure, same drivers, but a phase shift applied to one, and not the other. In isolation, they will sound the same. Put them together, and you will hear strange reinforcements and cancellations as you move about. This is relative phase, and is very audible indeed. What we need to concern ourselves with is relative phase only. Two amplifiers with different phase responses used as a stereo pair will sound terrible if the shift is sufficient. Use two of the same amplifier, and there is no problem. Absolute phase is inaudible within reason - a 3,600° phase shift represents a time delay that is significant, but a 360° phase shift will not be heard. Inverting a signal (e.g. reversing the connections to a loudspeaker driver) creates a 180° phase inversion, but this is not the same thing as a 180° phase shift! This is a point missed by many. Relative phase is audible, depending on the amount, the frequency and the context. Two speakers side by side with 90° phase shift between them will sound dreadful - and the sound will change as you move about. The relative phase of two musical instruments playing in harmony makes the sound you hear - take away the phase shifts, and it will sound flat and lifeless. There have been many tests and experiments to look at phase shifts within the audio band, and whether they are audible. Under controlled laboratory conditions (or using headphones), there is strong evidence that with single (complex) tones, there is an audible change. However, in a listening room with speakers reproducing music, there is little evidence that phase shifts are audible with the vast majority of recorded material. from here: http://sound.westhost.com/ptd.htm So it appears since two different speakers with different TS parameters will play out of phase just as two drivers do while hooked in series SQ should suffer. Makes sense, but we're forgetting something: the nasty listening enviroment found inside a noisy, highly reflective, moving vehicle, lol. If anyone had the stamina to read this guy's article through to the end would find this in the summary: Human hearing is very adept at picking the original sound from the reverberant field, provided the early reflections are not so early that they influence the direct sound. Given the highly reverberant listening rooms of some people, I have difficulty understanding how they can even tell what anything really sounds like - yet they will happily espouse their theories on what makes the sound better, ignoring the fact that their room will destroy the sound of any loudspeaker. So what does this mean in a nutshell? All these wonderful theories about the best way to hook up drivers may not mean much in the horrid mobile audio enviroment, even to self-proclaimed "audiophiles", much less your average Sony fan. Nope actual experimentation would serve us better. You got the stuff Sub. Get Sean to send you some of his enclosure rejects(preferably the sealed ones), or better yet go pick em up to save shipping. Drop in some crazy, different impedance, size and TS parameter combos(with "good" subs of course, in "correct" enclosures) powered by a good amp and see if you can make em sound substantially worse than a single "awesome" driver like that Ti of yours. It may be harder than you think.  -Fishy [note] I apologize for the treatise and congratulate anyone that managed to read the whole thing and stand in amazement of anyone that understood half of what I was trying to say. I'm still not too sure myself, hehe. |
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Gold Member Username: SubfanaticWalton, Ky Post Number: 3823 Registered: Dec-04 | well im pretty lostm, but i DID get the major jist of it after paraphrasing it lol. But see i DID NOT get this out of it, is it saying that the subs will not get loud, or just not sound good, cause basically i would take a wall or some 28 or so subs, i already have them all lol with amps for them all lol. wire them together and make just a moving mass that will just put out HUGE SPL numbers hopefully, after concreting the vans walls, or would i get better spl from just 2 15 tis that i have or all 28 subs sounding like complete crap, i dont want sq, i want STRAIGHT SPL. But iwill do alot of expierimentations lol |
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Gold Member Username: FishyTamarac Ft.Laud, FL USA Post Number: 1366 Registered: Sep-04 | They'll get loud, but with enough cancellation from reflections and inherent driver phase differences may be fairly "quiet" at certain frequencies. The only way you'll find out for sure is to try it. However, that'll be a helluva lot of work if you have to build your own enclosures. :P Lol, and don't tell me you want STRAIGHT SPL. You got to have something that is at least remotely musical or you'll get tired of the noise purty quick........ or maybe not. You'd surely get some laughs at any SPL competition regardless. -Fishy |
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Gold Member Username: FishyTamarac Ft.Laud, FL USA Post Number: 1367 Registered: Sep-04 | Oh and don't forget to add a couple gigawatts worth of alternator, or maybe half a ton of battery bank...... and concrete as sound deadening too. :P You're a nutcase, hehe. -Fishy |
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Gold Member Username: SubfanaticWalton, Ky Post Number: 3840 Registered: Dec-04 | hah i know, ive got everything planned out lol, that is IF i do this, i habve alot ofthings i want to do |
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