mcamson

I just installed a system in my 2006 GS300. This is similar to the newest body style minus the extra horse power.

Installed MM6501 Polk Audio Components in the front
DB6501 Polk Audio Components in the rear
JL 12W3v3 subwoofer in the trunk

The shop installed the sub in a custom box with a flush panel and the port at the top of the box. They removed the stock woofer so the box is ported into the cabin.

Problem: The bass isn't hitting hard when the trunk is closed. I know it's not the sub because I can see the sub hitting really hard with the trunk door open. Has anyone else encountered this problem? I've definitely got enough juice going to the sub as I have 400watts coming from a Polk 1100.5 amp. The box is up against the back seats with the woofer facing the back of the car. I noticed when the box is in the middle of the car, that it sounds much better than when up against the seat. When it's up against the seat, I can hardly tell I have a woofer. The shop told me it had to do with the insulation of the Lexus blocking most of the bass.

I appreciate your advice. Thanks.

Robert_J

Your box is sealing off the trunk from the cabin. You should have gone with a different design or put the sub in a different orientation. Can you fire the drivers towards the front of the car?

Banda798

I have somewhat the same problem in my 250. I'm getting a custom ported bandpass box built with the port aiming through the pull down armrest/cup holder in the back seat

mcamson

I have mine ported through the stock subwoofer hole. They took out the speaker so the air can come thru. Banda, how is your setup going to be any different? Do you think if I took off the flush panel, and used the same box, that it would hit hard because there would be room for air?

Any other GS owners encounter this problem?

mitsuguy

iTrader: (2)

Firing backwards is the best way for sure and in the position you have yours is generally the best... if the port is firing in to a different airspace than the sub is in, or if the port is firing the opposite direction the sub is facing, it can cause the output to roll off - it detunes the port to an extent and can cause the port to even cancel the sub some... With ported subs, I've always had the best luck with the port facing at a 90 degree angle to the sub inside the box with the port sharing the airspace of the sub, with second best which is having the port on the same face as the sub itself....


In my old SC400, I had a 13W1 and output was quite good, even with the fuel tank between the trunk and back seats... sub was facing backwards, as was the port...

No matter what, it will never be as loud as the same setup in a hatchback...

If it were me, I would change the location of the port... Also make sure the port is correct for the sub - generally installers are pretty good at this, but not every time... How big is your box? the proper box for a 13w3 is either 2.25 or 2.5 cu ft plus the airspace used by the port and subwoofer... With just a rectangular box in my SC, it took up a good portion of the trunk...

http://mobile.jlaudio.com/products_s...p?series_id=26

You can see there that the port is forever long and huge, as is the box...

mcamson

When you say 90 degrees, are you saying that the port is on top of the box? If so, then that is how my box is set up. I don't think it has to do with how they constructed the box either because it hits really hard if I look at it when the trunk is open. I feel a lot of air coming out of the port too. I have a 12" W3 which calls for 1.75 cubic feet which is how they designed the box.

I wonder if it has to do with the port firing into a different air space or if it has to do with the flush panel blocking some of the bass that's created by the actual sub and not the port. Either could be true since moving the box towards the middle of the trunk (ie not porting it directly below the factory sub hole, but rather into the trunk of the car) makes the bass sound 5x louder and deeper.

The reason I ask is the shop is going to have to figure it out. I want to go with the most cost effective fix. Should I take out the flush panel from the box and use the same box or have them rebuild a box? I wonder if they can just move the port on the current box. Do shops typically guarantee against this problem of mine? Will they rebuild a box free of charge?

Or should I just use a completely different box wherein it's longer in depth and narrower in (left to right) width?

Thanks for your advice!

Robert_J

On a ported enclosure, the port only makes a sound near the enclosures Fb (port's tuning frequency). It doesn't help with any other part of the sub's frequency range.

Here's something I posted a few years ago at Home Theater Forum. The light blue line that peaks at 28hz is the sound coming from the port. As the frequencies increase, the port output decreases and the output from the driver increases. Here's the original thread - link

Big Mack

iTrader: (1)

Incorrect. The port helps with the entire range that the sub is playing - until it gets below the tuning frequency. Then it can unload the woofer and cause damage. Additionally, it hits it's peak at the resonance of the woofer, but it also unloads the woofer in the chart you posted. As you can see in there, it has it's maximum output below the Fb and right at the Fs of the speaker. Once it gets above the Fb, the output only decreases to match the woofer's output, thus the reason why the output of a vented enclosure is a net gain of about 3dB above that of sealed - you have the output of the sub and output of the vent combining. It's also why it's optimum to have the vent tuned to a frequency below the Fs to take advantage of the efficiency at Fs and not risk the woofer unloading. Obviously with woofers that have an extremely low Fs, this becomes impractical, and it is also dependent on the output desired by the user. Someone who listens to rap or hip hop might want a little higher tune to hit where the music does, whereas someone who listens mostly to rock or metal might want a lower one so the kick drum hits better. This is why it is so important to ask questions to clients when building a system!

As for the OP's issue, the physical dimensions of the box don't play as much into the it as the reflection off the back of the trunk directly into the woofer will. When you open the trunk, it allows the reflections to have somewhere else to go. It sounds like they built the box with a flat front instead of a slight angle. This can make a HUGE difference in the amount of output you hear due to the fact that the reflection is controlling the woofer to a certain extent. Unfortunately, that may mean having to build a new box. Try this - put a board on the back of the trunk (facing the box) at a slight angle and listen with the trunk closed. If this alleviates the problem, that's your most likely culprit/solution.

Mitsu - the optimum is actually to have the vent on the same face as the woofer in most cases, as it allows the direct control of the vent by the woofer - anytime you introduce a 90 degree angle into it, it can affect the woofer because of the wave interactions. Obviously with transmission line enclosures or obscenely long port sizes, this becomes less of an issue because of the time delay in getting the air out of the vent. And having a vent on the opposite side of the woofer can bring all kinds of challenges in, since you run the risk of front and back wave interaction and possibility of killing the base entirely at certain frequencies - but that's way OT for this problem.

Big Mack

mcamson

I'll try putting a board in the trunk to reflect the bass. If that works, I might just have to build a box with a sub angle slightly tilted upward. I wonder if they can just modify my old box or if they have to start from scratch.

Big Mack, what do you think about just taking off the flush panel to see if that helps allow the air/bass to move into the cabin. This would be the most cost effective since I've already spent a lot on my system.

Sffd103

iTrader: (16)

here is what they did to my system. I know that you don't want to redo your system again, but this is just an idea. It was ported and directed to have bass enter the cabin.https://www.clublexus.com/forums/lex...with-pics.html

mkorsu

Before you start rebuilding everything try a simple test. You stated that the bass was very loud with the trunk open but nonexistent with the trunk closed. Sounds like your sub is 180 degrees out of phase. Try switching the speaker leads on your enclosure (or switch the phasing on your head unit or amp if they offer that selection).

mcamson

Well, that statement is not entirely true. I mispoke. It's a little bit louder when the trunk is open, but a 5x louder if I put the box in the middle of the trunk (open or closed).

Shibumi1

ok time to chime in... what ur dealing with is a standing wave.. causing cancellation.. easiest most reliable way to solve the problem is to load the sub (and port if ur using a vented encl) thru a vent(or slot aka slot loaded enclosure) directly thru the oem sub opening (or armrest but if u have someone sitting the rear seat u'll lose output)an seal the opening to make sure the trunk an cabin are separate.

guaranteed to work 100% of the time

mkorsu

+1

lev00221

iTrader: (28)

Agreed. You are having severe cancellation issues. I would try sealing off the hole in your rear deck first before doing anything else. I bet that the improvement will be dramatic.