RMS capabilities

[sqcomp]

To clarify the most important point in RR's last post...

The one of two main culprits of dead speakers is raw Voltage. Both of RR's responses to my question say the same thing essentially. More "Wattage" (Voltage is what he means in this case) CAUSES the speaker to go past its physical limitations. A speaker can only move so much.

In my years of doing this, I have only killed one set of speakers by overpowering them and that was a pair of Diamond Audio Hex Aluminum tweeters. I fed them off of a Kicker ZR600 to the passive for the S600a set. If anyone knows that amplifier, you KNOW it is a bad a$$ piece.

I’d speculate at least 10 to 1 that most speakers are killed by UNDERPOWERING them.

When Johnny Boy Racer cranks up his badly planned system to impress Sally Mae Cameltoe…he’ll more often than not clip the signal by asking the amplifier to produce more of a signal than it can. The voice coil of a speaker moves it back and forth (hence the positive and negative points off the voice coil). Well, when junior turns that volume knob on the stereo (technically referred to as a potentiometer), he increases the signal Voltage going to that amplifier. The signal Voltage is then amplified into the positive and negative (go look for a definition of alternating current) outputs of the amplifier into the speaker’s positive and negative poles of its voice coil.

Keep tracking with me here…

An amplifier can only amplify Voltage to a certain point. When the amplifier is asked by Johnny to get louder than it can…it clips. The positive and negative Voltage signal wave wants to go beyond the amplifier’s limits. Well, the signal does, but the amplifier doesn’t put out anymore (output Voltage). It clips the wave. Unless the moron behind the volume turns the Voltage signal down, every time the CD signals the radio to play that information that clips the amplifier, it will keep clipping on that certain part. ANY part of the signal that goes past the amplifier’s ability to reproduce the output Voltage will stay at the amplifier’s maximum output. Imagine a bass line that keeps repeating on your favorite show-off CD track. The amplifier will keep trying to put out as much as it can. Well guess what people, the speaker will follow suit. The cone will move whatever way that Voltage wave is going and stay there until the Voltage wave comes back to where the amplifier can play into normal limits.

Oh, we’re not finished yet…

That speaker trying to reproduce the output Voltage signal (clipped signal) comes back to the opposite side of the wave. Basically, when you clip your amplifier, you’re heating up the voice coil. Why you ask? The voice coil isn’t moving when it’s stuck at the top and the bottom of the signal wave! You’re burning the hell out of the voice coil. Why am I burning the coil? Because genius, the cone has to move to cool itself! Why do you think speaker manufacturers have made such a selling point on the “cooling technologies” of their products? Does anybody remember the first time they smelled ferrofluid or the metallic burning smell? I certainly do. There are two main ways to work past clipping a signal. The first and smartest way is to turn down your $hit! The second way is to have enough output on the amplifier as to not need all its output Voltage. You do run the risk with the second choice of physically overpowering the speaker though. With this being said, the REAL cure to clipping is level matching your system. It’s also called gain matching. I think I put a little ditty on the board a while back about that.

In my case, my worry for my system is using the Exile Audio Xi 800.4 on a pair of VERY NICE Hybrid Audio L1 Pro tweeters. That translates to a potential output of around 400 Watts per channel bridged given 14.4 Volts. That will be watched VERY closely and mitigated with containing the speaker's signal within certain frequencies and the signal Voltage being controlled by both the processor and the gain on the amplifier itself.

There’s also the part about frequency I didn’t talk about in my rant here. I can cover that if you want but it should be obvious why you use certain speakers for certain frequencies…

If I’ve made a mistake in any of this little rant, PLEASE correct me. It’s LATE here in Baghdad. I’m a little tired from working 7 days a week.

[sqcomp]

Just for our enjoyment...A clipped signal:



Oh what I wouldn't give for that piece right now!

[sqcomp]

…Also, while the vented/ported enclosure is more efficient in terms of sensitivity, you MUST give something to get something. The sealed enclosure helps the woofer play at a more even and stable frequency range AND you take up much less room.

…I’m also biased towards the sealed enclosure. I have never had a vented enclosure (sort of). I do like playing with variovents (aperiodic vents) on my sealed enclosures. I’m a sealed pervert!

We're going to be experimenting with them to see how they affect the sound of the impossibly small sealed enclosure with my two ID 15"s in my Yaris when I get back.

[RedRide]

Originally Posted by sqcomp

…Also, while the vented/ported enclosure is more efficient in terms of sensitivity, you MUST give something to get something. The sealed enclosure helps the woofer play at a more even and stable frequency range AND you take up much less room.

…I’m also biased towards the sealed enclosure. I have never had a vented enclosure (sort of). I do like playing with variovents (aperiodic vents) on my sealed enclosures. I’m a sealed pervert!

We're going to be experimenting with them to see how they affect the sound of the impossibly small sealed enclosure with my two ID 15"s in my Yaris when I get back.

Yes, I agree that a sealed encloseure give a tighter, more refined bass response due to due to the increase damping factor of the speaker.

[sqcomp]

You mentioned another characteristic of amplifier performance...Damping factor. Generally that phrase will tell one that an amplifier can "control" it's transducer load. That being said, I'm about to come down like I did on the sensitivity issue...Remember the give something to get something issue? It's the same here as well.

There are SO many variables to "calculate" it'd be a bitch to talk about. Needless to say, in this matter its very much like speaker sensitivity...there's much more to overall sound than just one or two measurements.

Here's a quote from a fellow music enthusiast, "There are an awful lot of people out there spending money on specs they will never be able to hear as differences in the music in a million years. Just don't expect them to ever admit it. I have to really work not to laugh my head off when someone tells me they spent several hundred dollars - or even over a thousand - on speaker cables and they "sound better" than a nice heavy gauge twisted pair of stranded copper wires they could have had for about five bucks..." -B.B. 2001

The same works for my philosophy for the most part. With the equipment I'm using on my Yaris, the amplifiers and the source are upper "midline" (being Exile and JVC) however the specs and construction on the pieces are very solid. I'm not worried about induced noise at all. The processing piece and the speakers are "high end" however. I'm taking into account that the install is the best I can make it (I know it is with all the little installer tricks, experience, and shop support that I have). I have NO reservations about the equipment choices that I've made.

[talnlnky]

Originally Posted by RedRide

Yes, I agree that a sealed encloseure give a tighter, more refined bass response due to due to the increase damping factor of the speaker.

Depending on how you tune a ported box, you can actually get ported boxes to have a better transient response time (aka group delay). Its really easy to do in home theater subs where you aim to tune at 20hz or lower... The group delay spike doesn't really start to kick in until 30hz... thus giving you a slightly better group delay in the 30hz and up region compared to sealed setups. And honestly, once you get below 30hz.... you really can't hear the difference in group delay.

[sqcomp]

Aside from the vented/ported space requirements and powerhandling/sensitivity changes of a speaker in a ported enclosure...the group delay idea is fairly new to me.

I'm wondering...in reality...are we going to hear a difference between a two properly constructed enclosures (ported and sealed), everything being equal, in the realm of response time?

If the amplifiers have good control...wouldn't the added "sensetivity" of the ported enclosure make it inherently more loose when dealing with equal sized woofers?

Then again, we have to wonder to what specifications the ported enclosure is built...I know darnwell I've heard some tight ported enclosures. *sigh* And then on the other hand, that "tightness" may have been from the added output amplitude rather than physical control.

The problem is that you MUST give something to get something. For the quick response of the ported enclosure, what do you have to have? A bigger, more elaborate enclosure (which is a given versus a sealed enclosure), or do we loose power handling and/or frequency response? What do we give up here?

That in itself is enough for me to stick with a sealed enclosure's benefits of space savings. Mind you, that's MY preference. A 15" woofer in one cube with plenty of power sounds just sexy to me...

Let us talk more on this specific subject though, its interesting.

[talnlnky]

Originally Posted by sqcomp

Aside from the vented/ported space requirements and powerhandling/sensitivity changes of a speaker in a ported enclosure...the group delay idea is fairly new to me.

I'm wondering...in reality...are we going to hear a difference between a two properly constructed enclosures (ported and sealed), everything being equal, in the realm of response time?

If the amplifiers have good control...wouldn't the added "sensetivity" of the ported enclosure make it inherently more loose when dealing with equal sized woofers?

You are close... the "loose/boomy/sloppy" sound is usually due to an over-accented low end, Usually due to a ported or bandpass box being tuned to high which results in a huge 6-10dB spike somewhere in the 40-60hz range. If you make the frequency response flat, slightly rolled off, or even with a small dB bump you will not get that bad "sloppy" sound.... unless the group delay is really slow.

Group delay is basically the time that the coil takes to get saturated and reverse its directions.... so... how long it takes for it to stop, and start. The quicker it can do that, the cleaner the sound. The T/S spec that you can check to guesstimate if the GD will be good or bad is the (Le). Also... tuning a sub low will also help keep GD spikes down.

Originally Posted by sqcomp

Then again, we have to wonder to what specifications the ported enclosure is built...I know darnwell I've heard some tight ported enclosures. *sigh* And then on the other hand, that "tightness" may have been from the added output amplitude rather than physical control.

It is about the design of the box... a properly designed ported box (for sq) will be indistiguisable from a sealed box in terms of transient response (tightness)... but it will have slightly more low end.... even if you do design the box to roll off and mimic a sealed box (Makes for a darn good sq box in cars). Once again, the naturally dB gain from a ported box doesn't make it sloppy, just louder... an exaggerated bump will make it sound sloppy (mostly due to a high tuning)[/QUOTE]

Originally Posted by sqcomp

The problem is that you MUST give something to get something. For the quick response of the ported enclosure, what do you have to have? A bigger, more elaborate enclosure (which is a given versus a sealed enclosure), or do we loose power handling and/or frequency response? What do we give up here?

True, there is no perfect enclosure... size, response, efficiency, all kinds of enclosures suck at at least one of the three.... kinda like Hoffman's Iron law for speakers. The main thing for keeping a tight response on a ported box is a tuning at or below 30hz & a sub with a relatively low Le. You can do it with a huge box, or with a very small box.... If you want to mimic the frequency response/ roll off of a sealed box you just make the box undersized. Like the box in my avatar. Its 2 Tangband 8" 740C Drivers... a normal box would be .75-1cuft per driver @ 30-35hz for car use... I changed it to .6cuft @ 28hz for each driver... rolls it off nicely starting at mid 30's due to the small box size, but the tuning is still low so it tries to play low still.... I might have some picks on my laptop of the response somewhere.

Originally Posted by sqcomp

That in itself is enough for me to stick with a sealed enclosure's benefits of space savings. Mind you, that's MY preference. A 15" woofer in one cube with plenty of power sounds just sexy to me...

Let us talk more on this specific subject though, its interesting.

I NEED to show you the joys of the software I have for box modeling... Box modeling is where it's at when it comes to designing a good sub stage. You'd shit bricks if you saw what you could do with the right software. I've found that many times, a big sub in a sealed box is no better than a smaller sub in a well designed ported box, and that the smaller sub will actually play louder down low.

I forget exactly what it is... but physics states that a speaker will need an ever increasing box size the bigger the speaker gets.... It has to do with the Surface area (SD) of the speaker & the Vas I believe. If you double the cone area, I think the speaker would require 4 times the box size....all other variables staying the same of course. I might be a bit off on that tho....

Regardless... in the space that you could fit a single 15" sealed woofer... I could probably fit 4-6 similarly spec'd 8" subs.... would have less cone movement, & probably higher efficiency... meaning... louder & less distortion.


Like I said... I really want to spend 30mins to an hour showing you the joys of box modeling and what crazy shit you can do with a driver. I've got a copy of a really nice program.

[sqcomp]

No no man...we need to do this over a beer or seven after hours at the shop in Vancouver. I'm one of the old school types who LOVE big woofers. I'd like to see what could happen with two ID 15"s given the space requirements I'm working with.

...you know...

there's a "cavern" of space under the rear seat of the Yaris sedan...

[talnlnky]

Originally Posted by sqcomp

No no man...we need to do this over a beer or seven after hours at the shop in Vancouver. I'm one of the old school types who LOVE big woofers. I'd like to see what could happen with two ID 15"s given the space requirements I'm working with.

...you know...

there's a "cavern" of space under the rear seat of the Yaris sedan...

no problem... you give me the TS specs for each sub, or even just a link that shows the TS specs and I'll make sure the drivers are loaded up into the database before I drive up.... Bring the laptop.

found some pics of the TB8 box... Top pic is a frequency response graph of the box using an older program that was decent, but not quite as good as what I currently use.

http://www.cardomain.com/ride/208374/3

[talnlnky]

ok sqcomp... started its own thread... so we don't jack this one anymore...
http://www.yarisworld.com/forums/sho...567#post372567

[Slick]

I still dont think my last question was ever answered :( Its otay though. I've already redesigned the substage :) Happy to provide a high-jackable thread :)

[talnlnky]

Originally Posted by Slick

Well, I plan to run 2 of these at 4 ohm http://www.onlinecarstereo.com/CarAu...roductID=15441
However, I am questioning the power capabilities of my current amp http://www.sonicelectronix.com/item_...ar+MXA282.html

Its true output at 4 ohms is roughly 750 ish, all things taken into consideration.

Actually... looking at the specs for that amp... it states is uses dual 35amp fuses... meaning a realistic expectation would be for that amp to produce a MAX of 500watts rms (at its lowest ohm rating with both channels hooked up).... so if I had to guess... I'd say the amp was really a 125x2 @ 4ohm, 250x2 @ 2ohm or 500x1 @ 1ohm. Basically, for an A/B amp you take the total fuse rating, times it by .5-.6 and then multiply that by 13 to get a realistic idea of power output. Reason is .5-.6 = 50-60% efficiency of the amp. 13 is the voltage. Total power = voltage times amperage.... but the amp wastes about half that power.

Originally Posted by Slick

The amp is 1000 rms at 4 ohms each channel. However, if I'm not mistaken, you cannot wire a single DVC 4 ohm sub to 4 ohm, either 2 or 8. Correct me if i'm wrong. The problem i'm having is that the amp is rated at 1600 rms at 2 ohm. The subs are only rated 900. Even if the amp is capable of only producing even 1000 rms at 2 ohm per channel, wont that severely injure my subs?

Correct a single 4ohm DVC sub can do 2 or 8 ohm on a single channel. To get full power from this amp you'd want a sub with DVC 2ohm coils, DVC 8ohm, or SVC 4ohm, or even QUAD 1ohm (yes quad coils do exist). Like I said above... I highly doubt this amp actually puts out more than 500rms, so I think the sub will be fine. even if it did put out 1000rms or more... it would really depend on what box you put the sub in (mechanical movement) and how you beat on your sub (how you play it)... Often times subs can take more power than they are rated for if setup properly.

Originally Posted by Slick

Now, I know you can wire 2 4 ohm DVC subs to 4 ohm together in parallel but in order for the amp to see 4 ohm I would have to bridge the + of the left output on the amp with the - or the right output. And again, please correct me if I'm wrong. I only half-ass know what I'm talking about :) If i wire the subs up like that then that means it will be trying to push the full 4000 watts. Obviously not going to be that much but you can sort of see where I'm going with this.

take a look at the JL tutorials.. .they are pretty good, and even though JL uses wierd voice coils (3ohm,1.5ohm, 6ohm) you get the idea... If you do parallel you half the ohm load, if you do series, you double the ohm load.

http://mobile.jlaudio.com/support_pages.php?page_id=145

Originally Posted by Slick

I have been trying to figure this out for about a week now, asking ppl different stuff tying to get a fix on what to do.

Can anyone please give me a REALITY CHECK and explain this stuff to a freakin noob, I will be forever grateful. Thank you in advance.

We be back on topic now... so any other questions you have i'll be able to address now.


On a side note... I generally would try to urge steer people away from audiobahn equipment... and to a lesser extent the lanzar amp. You can usually find products better designed, and more durable for the same price as bahn.

[talnlnky]

Take a look at this... just one idea... there's tons of options out there.. Comes in DVC & SVC 4ohm
http://www.soundsplinter.com/rli10_s...formation.html