Porting trunk

[GNandTTA]

I'm not saying sealed enclosures are BAD, but rather not nearly as efficient as a ported enclosure. No matter what application, a sealed enclosure is not as efficient as a ported enclosure. Why? That port is another source of sound waves. This can effectively give a 3 dB of gain. This is quite noticeable. Not to mention, you have a MUCH better frequency response with a ported enclosure over a sealed. AND, because you have full power handling down to the tuned frequency, this gives you cone control into the lower frequencies. This will allow you to put more power to lower bass and keep the cone controlled, unlike a sealed, where the cone excursion just inceases as the frequency decreases.

The only bad thing about ported enclosures is that they unload the woofer below the tuned frequency. This can have profound and damaging effects to the woofer. This can happen even though you are well below the woofers power rating. Which brings up another side of the story. There are really 2 kinds of power ratings for a woofer. The one stamped on the bottom of the magnet is the thermal power rating. This simply means how many watts the coil can handle before it melts. The other is far more critical, IMO. It is known as displacement power handling. It is 99% controled by the enclosure. Enclosures such as a poorly tuned ported enclosure will have a much smaller displacement power handeling than thermal. About the best for displacement power is a properly designed bandpass. Typically a 4th order, or single reflex. These IMO are the best enclosures for true sub bass. Excellent displacement power handeling and typically a 3 to 6 db gain (even better than ported) in the sub bass region.

 

[zam70]

GNandTTA, gotts disagree on this one.

In my experience, band pass are excellent for efficiency gain but terrible in every other way. Mono tone bass, lower power handling, peaky..etc, etc...

There was one particular car I built for a customer with 4 band pass 12s, it physically destroyed the woofers in no time but did play LOUD when complete (voice coils were fine, kinda weird just watching the dust cap move in an open basket)...just not very musical IMO.

I do agree on the BIG lie of power handling ratings...I personally think they should be rated both ways. Sure would save alot of disappointment in the end.

 

[Joe Tiano]

well...there ya go!..a trade off!...IMO the charts and graphs are wonderful tools...the rest is luck...and mother nature! joe

 

[mcss383]

GNandTTA: Thats exactly the reason why you HAVE to run a sub-sonic filter with a ported box so you don't unload the sub and destroy it. With the filter in place, you then have a box with a better efficiency than a sealed box and CAN play just as cleanly as a sealed if tuned for it.

 

[PPI Typhoon]

Originally posted by Joe Tiano
85% of your sound?????....lets see here... 100hz-20...yep thats all you need to win a local spl show!....i'm not flaming here, as i used to show up at my local SPL shows..0-100 watt class...with 1, XTR 15 dvc in a bandpass box...and it WAS a BOX indeed!..powerd by a bridged 250hcca orion...100hz up was handeld by a junk clarion cd player with maybe 10w on a pair of morel integra 6.5" coax...yep 3 speekers.. NO EQ...139dB..and a response curve(RTA) of 34-38..(based on the iasca 40 point RTA system)...depending on where the mike was placed!...it was loud...looked good to the RTA!....looked good to the RTA!..looked good to the RTA..and to think...it all only took 30 min to install!..that was back in 93' tho.and the car had better sound quality than most of the cars competing in sound quality...with NO! emphasis on install ..just a magic box....just make the machine happy!...(RTA) joe

When I said for 85% of the sound, I'm strictly talking bass. You can sit a bare subwoofer in your trunk, and it'll make noise. Maybe not what you wanted, but it'll make noise. But a majority of your sound for bass response depends on your enclosure, not the modifications to your vehicle.

But seeing how this direction has taken us, I'm gonna refrain from posting here anymore. It just seems to be going against the grain of too many people and their habits. I was just offering some advice from a name in the industry and a fellow boosted vehicle owner. If you all want to cut up your cars, go right ahead. This isn't worth the arguments. But I suppose it's the non-believers and the unwilling that keep me in a job.

If any of you guys need questions answered, feel free to email me at work. dhanisch@directed.com

Best regards,

 

[Audiowizard]

Originally posted by PPI Typhoon
But seeing how this direction has taken us, I'm gonna refrain from posting here anymore. It just seems to be going against the grain of too many people and their habits. I was just offering some advice from a name in the industry and a fellow boosted vehicle owner. If you all want to cut up your cars, go right ahead. This isn't worth the arguments. But I suppose it's the non-believers and the unwilling that keep me in a job.

You hit the nail right on the head! I am with you on this one! This is ONE subject that you are NOT going to get everyone to agree on evenly. There has been ALOT of opinions and experiences that have been shared on this post that has been valuable information for the person asking the post. Now I am not a big fan of cutting up a car but to acheive the bottom end sound that is well deserving to an audiophiles ears, cutting 2 small holes in the rear deck of my '86 GN will not hurt the structural integrity or value of my car and was well worth the modification in my honest opinion!

I vote to kill this thread for for reasons stated above but feel free to add more comments and experiences that will be helpful to this thread without the "dissaggreements" posts!

What works for "Joe-blow" (NO pun intended Mr. Tiano ) isn't always the gospel, but if it works for you then that is all that matters! Thank you..............................

 

[GNandTTA]

There was one particular car I built for a customer with 4 band pass 12s, it physically destroyed the woofers in no time but did play LOUD when complete (voice coils were fine, kinda weird just watching the dust cap move in an open basket)...just not very musical IMO.

It probably was not designed right. First one I did performed poorly as well. But if you get the design right, IMO they are the best. Get it wrong and they can be the worst. That being said, get the best plans possible. The one I have in my GN uses 2 Orion XTR 10's. It's all mathematics and physics. And I don't pretend to understand all of it but from what I've read because of the multiple chambers, getting the exact volumes of each chamber are absolutly critical. I bought the woofers and got the plans from Orion in 92'. Still have the same box and same woofers. Box hits VERY VERY hard and sounds just like a ported box, only louder. Plus it looks pretty cool, all you see is one big rectangular port in the trunk.

Thats exactly the reason why you HAVE to run a sub-sonic filter with a ported box so you don't unload the sub and destroy it. With the filter in place, you then have a box with a better efficiency than a sealed box and CAN play just as cleanly as a sealed if tuned for it.

Very true, ported boxes are my second favorite. Easier to design than a bandpass but better sub bass than a sealed.