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Monday, May 18, 06:58:30am [ Login ] [ Contact Forum Admin ] [ Main index ] [ Post a new message ] [ Search | Check update time | Archives: 1, [2] ]
Subject: Re: New system for me!


Author:
Sayar
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Date Posted: 21:52:46 05/20/06 Sat
In reply to: Sayar Kuchenski 's message, "New system for me!" on 14:29:08 03/28/06 Tue

Well I never got a very good look at the Escort but from what I remember the enclosure is very thin. If I remember right the face looked like it was only 3/4" thick and made out of particle board (correct me if I am wrong). Well enclosure flex kills SPL. It is absolutely inperetive that the enclosure is extremely stiff. I would not go with anything less then 2" thick MDF on tour enclosure and 3" for the face.

Also rounding the port sides can help big. Christifer from Cactus Sounds gained 1 dB. @ 163 dB. on the Term-Lab solely by rounding his port on the face of his enclosure. Also rounding the back side of the port is also useful.

I am stretching my memory on this one, but if I remember right you were using 2x4's for internal braces. Angle iron is a much better option. The wood that 2x4's are made out of is not the strongest wood in the world. Angle iron seems to work out much better from what I have seen. Not only is a piece of 1.5"X3/16" angle iron a lot stronger, it takes up like 1/10th the air space the 2x4's do. I usually take a piece of angle iron and weld a 6"x6" flat plate on each end and drill 6 holes in each plate. This allows me to screw or bolt it to the inside of the enclosure and the plate further increases straight of the enclosure because it spreads over an wider area then the 2x4's do.

Additionally because 2x4's displace a lot of airspace they cerate turbulence inside the enclosure especially if placed by the port. That further can reduce SPL. The angle iron is useful there too.

At the absolute minimal I would at least use a 3/4" or 1" threaded rod if you do not want the angle iron. It will still be a better option then the 2x4.

I suggest two braces for top to bottom and two for side to side. Now you may not want to run a brace from te front to back. I have been told by many SPL masters that running one from the front to back messes with something and reduces SPL. Usually you only gain SPL from going front to back if your enclosure flexes a lot.

A stiff enclosure is extremely important!!!! I cannot stress it enough. Your enclosure should be so strong that you should be able to knock on it and it feel like concrete. If it does not then you are loosing SPL due to flex. Never in my life have I ever heard of anyone loose SPL by strengthening an enclosure. In fact if you are really looking for some SPL I would reinforce the bottom of your enclosure with concrete. Many world champions do that and it works out very well.

I was talking with Randy form C&R Auto glass the other day about your Escort. He told me from what he remembers your box is not all the way forward to the B pillar. If so sliding it forward may be advantageous unless it changes the 1/4th wave frequency to your disadvantage.

Also I do not know how you sealed your wall off but using expanding foam and silicone is absolutely inparative. The wall must be completely sealed off from the back. Or else you can loose major SPL

I do not know how you built your trim panels to go around the enclosure to seal the wall off, but I found it is usually better to not build trim panels and build the face so that it is flush against all sides of the vehicle. That way you do not need trim panels. Trim panels are not as strong because they are not physically part of the face. Thus making the face big enough to completely seal everything off is preferable in my opinion.

I also found that it is a good idea to make the top of the baffle about 1/8" too big. This places pressure on the roof essentially bracing it which can increase SPL.

Here is a tip that Mark Barfield told me (3rd loudest vehicle in the world): No sound off organization, to the best of my knowledge, considers the undercarriage to be part of the cabin or part of any rule that pertains to in front of the B pillar. Therefor you can fiberglass or reinforce the undercarriage of the vehicle which will make the floor stiffer. This can greatly increase SPL by over 2 dB. in many cases (unfortunately not mine).

Then there is the fact of the enclosure itself. I do not know how big it is but if it was my vehicle the enclosure may be bigger. It appeared a bit small. But I do not know the exact volume of it so I am not 100% sure. But the port seemed too small. Port area is also very important in SPL. I think if you went with more port area you would greatly increase your score, assuming you re-tuned everything.

In my Jeep my port is 450 square inches. If I had the room it would be like 800. I know a guy that has the world record in his class that is running a single 18" RE MT in a bandpass enclosure and he has about 1,000 square inches of port area.

Did you actually tune your port with your SPL meter? Or did you just put in a port that you though would work and call it a day? I assumed you actually tuned the enclosure with your meter but if you didn’t then you may be loosing major SPL.

Also I noticed that you place pieces of MDF on the floor by the enclosure to cover up the holes in the floor for the back seat area. Well those covers would be a lot more useful if they were air tight. I found that any modification to the front of the B pillar that is designed to take up air space, works signifently if it is completely air tight. You do not have to necessarily glue it to the floor. Some weather strips on the wood and duct tape can do the trick.

I did notice you did slide your passenger seat forward and lean it forward. That is good. Many people don’t do that. But taking out your drivers side seat may help a lot too. It often helps because the seat blocks the natural movement of the rear wave coming out of the port. I gained about .6 dB. @ 155 dB. (Term-Lab) by removing mine.

I recently found a neat trick when I was at a comp in FL. I found that placing objects on your passenger seat can help increase your SPL score a lot. Just anything solid to take up air space. I believe that it helps because not only does it take up airspace it helps capture the waveform in the passenger side of the vehicle there for creating more of a standing wave my the sensor. There is no rule in any sound off organization that says you cannot have a messy car and there for have "stuff" on your seat. They may not allow a wooden box, but a big case of CD's or something like that should be legal.

And finally bracing of the body... I do not know if you gain or loose SPL my having people push on the vehicle. But it is definitely something to try. If you gain SPL by having people push on your vehicle then throw like 15 people on it. I have seen people gain 3 dB. by having a lot of people on their vehicle. Windshield, both doors, roof, side windows... all flex.

Also I would play around with your door pins. Move them in, move them out. Play with them and meter the system. I gained a few tenths by moving my passenger’s side door pin all the way out.

I would suggest you hook up your stock alternator to your 16 volt batteries. You could do this by taking two high current relays and wiring them in such way that when you flip a switch your vehicle runs of your battery up front and your alternator switches to power the back batteries for the run. And you can wire up a second switch that will bypass the alternator’s voltage regulator and full field the alternator. That will cause the alternator to put out maximum current as long as it is full fielded. You can run the wire to full field your alternator to a momentary push button switch. Then when you push the switch you will full field the alternator which will keep more voltage present at the terminals of your amplifiers and consequently make the amplifier produce more power.

There is a amplifier modification that can be done that is useful and legal in all sound off organizations as far as I know. I read an article about this mod awhile back and tried it myself. It does work. What you do is you open up all your amps and find the positive and negative voltage rails after the power supply. Then you run capacitors to them to give them reserve capacitance. So when you burp your system the caps discharge and you additional reserve power for the burp that the power supply cannot supply. This leads to more power to your subs. Think of it this way. The definition of clipping an amp is “when the output of the amplifier exceeded the output of it’s power supply”. So if you reduce the voltage drop at the rails when you burp the system you can get more power out of the amp. The caps do that.

If you want more info on how to do that I can hook you up. The guy that I learned how to do this from gained about 1 dB. @ 139 dB. with only a 100 watt amp! Plus he was only running a single 5.25” Bose woofer and he still did 139 dB. on the Term-Lab.

I have done everything I have explained here and found that it all works in my vehicle (accept the fiberglassing the undercarriage). I believe most of these trick will work for you too. I suggest trying all of them and metering after each change.

Please excuse any spelling errors. :P :)
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Replies:
Subject Author Date
Re: New system for me!randy at cr autoglass07:14:14 05/26/06 Fri
Re: New system for me!Lee Mocko21:34:54 05/28/06 Sun

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