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05 Monte Carlo LT Build

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#1 ·
Intro! If you just want pretty pictures, keep scrolling, there’s a ton. If you have 3 minutes to spare, read on.

Finally starting a build log for my 05 Monte Carlo LT. A little bit about the car: I decided to go with the red/black/chrome theme, and began adding little accents soon after I got the car.



Red stripe:



Seat/steering wheel covers:



Carbon fiber Di-Noc /vent trim:





Brake calipers. While working on painting the front two calipers, I did a stupid thing and jacked up both wheels. The tire jacks caved as I was taking off one of the front wheels and the weight of the car was resting on one corner of the jacks and the tire. See here :eek: :D:





But it all turned out alright:

 
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#449 ·
Right. The Beyma is more on the side of a pro audio speaker so its higher rated efficiency comes more from higher in the frequency spectrum. In the midbass region, it's no more sensitive than most others, and may actually be less depending on some things.
 
#452 ·
There is not difference as long as they are both rated at 1w/1m and not 2.83v/1m for one or the other.

As Grayson said the Beyma are not 90db in the range they are being used, they roll off a bit fast below 100hz. This is something many miss when selecting driver based on the sensitivity to match each other; the range in which the driver will be used and the sensitivity in that range.

But I agree the entire system sensitivity will drop more then likely after eqing, not just the midrange.
 
#454 ·
Regarding midbass - true. The point I was trying to make got carried away. I simply do not want to stretch too far one way or the other with each pair of drivers.

Forget about the mids. They are a whole different story. Not relevant if future plans pan out which will include swapping out a few things, all I'm saying regarding that. Just speculation at the moment. Perhaps I was vague. I'm at the point now where I can focus on tweaking the little things, and it's not much to ask for a system that is all similarly efficient in the end. Everybody needs to stop overanalyzing everything I say, or let me know if I need to be more clear. The rate at which this thread goes from one topic to a debate is astounding.

tl;dr looking for a wider range of potential midbass and weighing potential pros and cons; experience, suggestions and input is welcomed. Slightly redesigning enclosures is not entirely out of the question.
 
#456 ·
Don't get hung up on efficiency for midbass. Consider the effect of cabin gain here.

If power is hard to achieve then maybe it's a concern. Otherwise, efficiency isn't a serious issue outside of compression. Which, if the driver is designed well, won't be an issue.


Outside of that, I'd ask why you want to change and what you expect to get. Of the beyma's work for you, keep on rockin 'em.
 
#462 ·
Somewhere, a while ago, Gray and I had mentioned that we were going to take my leftover sheet of 1" plexiglas that I used for my sub baffle and test how bulletproof it was, if at all. Yesterday we did just that, and wound up with some pretty surprising results.

We used a .22-caliber revolver, I used my Smith & Wesson M&P 9 Compact and Gray used his Glock 19. We shot them all from both 30ft and 15ft. Here's what we found. :D

 
#467 ·
sheet of 1" plexiglas that I used for my sub baffle and test how bulletproof it was, if at all. Yesterday we did just that, and wound up with some pretty surprising results.

We used a .22-caliber revolver, I used my Smith & Wesson M&P 9 Compact and Gray used his Glock 19. We shot them all from both 30ft and 15ft. Here's what we found. :D
I see why the plexi cracked. It wasn't press fit into the target stand. ;) :cool:
 
#465 ·
I must say, I was surprised by the results. I fully expected the .22 to at least crack the plexi. It is thick and dense, but plexi has a reputation for being fairly brittle and easy to crack. I know acrylics are used to make bullet proof glass, but these are specially treated sheets and often have several layers of other laminated compounds as well. The sheet Ally had was just your basic run of the mill plexi.

But apparently in the 1" thick range, impact resistance skyrockets. With a quick wipe of the finger, you literally could not tell anything had ever touched it where the .22 rounds impacted.

With the 9mm, the importance of having a solid backstop became very important. With nothing behind the sheet to back it up, the 9mm round cracked the narrow sheet in half. With another piece of plexi or the wood blocks behind it, the one inch sheet was able to completely stop the round. I never would have guessed it was that strong.

For reference, here is a somewhat similar test of 1.25" thick polycast acrylic that's actually designed to be bullet resistant.

The Box O' Truth #6 - Ballistic Resistant Glass Gets Tested - Page 1
 
#474 ·
Hi Ally, just stopping by your build thread to say hi. good work on the vehicle.

I did want to comment regarding the discussion of efficiency above, the ratings of both 1w/1m efficiency and 2.83V sensitivity are actually calculated numbers based on driver parameters. They are basically accurate over any area where the response of the driver is not affected by the enclosure or baffle. It is the job of the system designer to then design the system to get the desired efficiency over the needed range. There are some limitations the designer has to work with though.

In sealed enclosures, down at lower frequencies the system is controlled by the enclosure and the efficiency of the woofer has almost no affect on the output of the system. We can use the SBP15 in 10cf sealed (basic trunk IB) as a means of comparison. The following shows the woofer with efficiency adjusted from 85-93dB by just altering the moving mass of the driver. You can see that once you get to 30hz, there is essentially no difference in output as it is completely controlled by the woofer.



No matter what woofer you put in, or how efficient it is at first, the limitation is the enclosure. This becomes more apparent in midrange/midbass drivers where you have smaller volumes to work with. The dominance of the enclosure is pushed up higher in frequency. Often times I see people making tiny sealed midbass enclosures and expecting miracles from the driver. At this point the only way to compensate for this is with EQ and added power. There is nothing wrong with using EQ to help bring up the low end in a sealed system. It is used in subwoofers all the time in everything from pro, hifi, recording and car markets and can be very effective. The Evolution Acoustics MM7 uses this approach with 4 sealed SBP15's and it is very successful. Just be aware that the efficiency of the driver alone doesn't control the low end output.

MMSeven | Evolution Acoustics

The other way to gain back efficiency is with a vented enclosure. Many people think of vented enclosures as boomy, slow, or not as tight as sealed enclosures, especially for midbass. In reality a properly designed vented enclosure can often be much lower distortion at any given SPL than a sealed enclosure. With low Q drivers that roll off very high, using a vented box will allow you to get the same input with as much as 1/6 the power around the tuning frequency. This keeps thermal distortions down, eddy currents low, and leads to much lower overall distortion at any given SPL. Vented enclosures also keep driver excursion way down at and around the tuning frequency. This keeps the driver operating in a more linear range, again lowering distortion.

The only issue you should be aware of is group delay, which is the derivative of phase. In a subwoofer application, tuning at 30hz and under there is not much to worry about. The wavelength of the frequencies is long enough that any group delay isn't a real audible factor. In midbass/midrange boxes it can become more of an issue. The best idea then is to tune lower. If you look at the group delay curve, by 1/2 octave above the tuning frequency the group delay comes down to a much more reasonable level, almost the same as a sealed enclosure. The mistake people often make is tuning a midbass enclosure right at the bottom of the range where they want to cross over. Ideally you want to tune 1/3 to 1/2 octave below your crossover point. You give up a slight amount of efficiency by doing this, but pushing the peak in group delay lower is IMO worth this slight loss. In this case you can see the difference between using the TD6M in a sealed enclosure of .5cf and a vented enclosure of .5cf.



If someone was to use a sealed enclosure, the efficiency is down by 9dB at 80hz. In comparison with the vented enclosure the response is less than 3dB down at the same point. You can see how much it is the design of the system and not the driver itself that determines the end efficiency. Also this 6dB difference means 4x less amplifier power to get the same SPL level. The difference between 1W and 4W may not seem significant, but the difference between 50W and 200W, and the difference in distortion and compression definitely is. There is some increase in group delay but crossing over at 80hz there will be little effect as the 5ms group delay is far shorter than the wavelength at 80hz.

That all said, there are some woofers that do not use realistic numbers for efficiency ratings at all. Many car companies used to give ratings WITH cabin gain included. Others will give an efficiency rating but not state whether it is a 1w/1m or 2.83V rating. I have seen dual 1ohm coil drivers with claimed efficiency of 98dB but in reality that is a 2.83V rating at 1/2ohm and the driver is more realistically 83dB 1w/1m. It is best to always put the parameters into a modelling program and let it calculate the efficiency for you. Others still will give efficiency based on measured curves, typically at the highest point of a breakup. Eminence does this for example measuring at a given frequency where the cone directivity is increasing the on axis output. This does not give a comparable number though because at other frequencies there is no way to get this actual efficiency no matter how the system is designed. In general though, the parameters of the driver will give you a very close estimate of real world efficiency for any point where the enclosure is not altering this efficiency.
 
#477 ·
So to start off this year's mods and changes, I finally got around to changing the gauge lights from light green to red. The whole job looked scarier than it actually was.

Stock cluster:



So of course I had to take the dash apart for the millionth time, pulled the cluster and started to take it apart. For once Chevy actually made the job easy with simple clips holding the thing together! :pepper:



Pried off the needles



Removed the plastic gauge





Applied some styrene plastic with adhesive to the white sections



Put it back together, and voila. My digital camera was out of battery so I used my inferior phone to take this. It's much brighter in person.









Overall a fun and easy project.


Next up, I modify the kickpanels to eliminate tactile feedback and resonance. :)
 
#479 ·
I still might drop in some LED bulbs, but this was so much easier and works well. I also do not have a proper soldering kit just yet. Perhaps sometime in the near future if the styrene burns out.

Now I am on to getting enough fiberglass supplies and then I'm off to do my very first glassing job all by my big self :D
 
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