Team-BHP - Not happy with thump effect need help

Naughty you can actually read my mind :D That's exactly what I meant by "tricky". In short every sub can perform different in an given ported enclosure. To determine the ported enclosure size one needs to keep certain parameters in mind like the Fs, qes, qts, Vas and xmax. A wrong size enclosure will give out a port freq which might not work with the sub. The most common issue in designing an ported enclosure is with the enclosure size and port tuning where both are equally most important. If either of them or both are not right than the sound will not
exactly like what the sub can produce.

Looking just at pic posted we cant determine whats the enclosure internal volume and port size/length. Best way would be to get an sealed enclosure with 1.25cu.ft which is modelled keeping the parameters in mind. JBL subs have higher sensitivity in which case output should not be much of an issue.

Please do not trust the manufacturers polarity markings especially since fake chinese and malaysian units abound in the Indian market which look too good to be true. To find out the right phase all you need is a 1.5 volt pencil battery along with a length of wire to find out the phase of your speakers excluding your tweeters. To find out; out of phase tweeters; you would need to find a friend who is extremely sensitive to phase changes.

On a personnel note I get a severe head ache and ear ache along with nausea when listening to out of phase drive units so much so that going to theater halls has become a royal pain as more often than not at least one of the speakers in an array are connected out of phase

Getting to the point:
Connect the positive of the battery to the positive of the speaker and then for short durations connect the negative of the battery to the negative marked lead of the speaker. Every single speaker cone in your set up should then move out in one direction. If any of the units move in then you have got yourself a fake or mistakenly marked speaker lead outs.

Only after the above is established do you need to check for out of tune bass reflex ports. I suggest that you opt for a sealed enclosure(not acoustic suspension) box for automobiles.

As for the five way drive unit I seriously suggest you give that one a miss and get yourself a good two way unit like the ones mentioned in another thread. It will be costlier than your five way unit but rest assured the sound that comes out of them will be revelation.
http://www.team-bhp.com/forum/ask-gu...ml#post1697739

Quote:

Originally Posted by Sam Kapasi (Post 1743437)

if you disconnect the battery, the only thing you need to re-adjust is the head unit.

Long time no see Sam! :-)

which is why I employ atleast 1st order XOs on the amp. If the car goes for servicing and I drive it a few weeks later atleast the speakers have some protection before my ears realise that all the settings are awry.

See I dont drive regularly. Sometimes not for weeks so if my car comes back from servicing I might never realise that the settings on the HU are set to default until I drive the car many weeks later.

Quote:

Originally Posted by Invinsible (Post 1742723)

To determine the ported enclosure size one needs to keep certain parameters in mind like the Fs, qes, qts, Vas and xmax. A wrong size enclosure will give out a port freq which might not work with the sub.

Looking just at pic posted we cant determine whats the enclosure internal volume and port size/length. Best way would be to get an sealed enclosure with 1.25cu.ft which is modelled keeping the parameters in mind. JBL subs have higher sensitivity in which case output should not be much of an issue.

1. Most manufacturers have about a 10% variation in their specs. This means that if teh Qts is +10% and the Fs is -10% you might get a box that is not suited to your subwoofer unless you measured the T/S parameters of your sub before making the box.

2. Sealed boxes however are more tolerant of incorrect TS parameters so using a sealed box as well as a sub designed to perfrom in one (Qts > 0.3 is one clue) is often the best option for DIYers. The other option (for home audio) is no box at all!

Quote:

Originally Posted by navin (Post 1743606)

1. Yes there could be some variation in specs. Which is why some manufacturer mentions the enclosure details along with their other spec which can be on safer side keeping certain parameters in mind like the xmax.

2. Well incorrect sealed enclosure design could result in sub damage as well. Sealed enclosures demand greater excursion limit. On long run if the sub is not able to handle the low end response and reaches or goes beyond it excursion limit could have adverse effect. Some softwares gives an idea what the sub will perform like in an given enclosure with the help of the parameters put up the manufacturer. For inexperienced users its better to go with manufacturer's recommendation.

Quote:

Originally Posted by Invinsible (Post 1743682)

1.
2. Well incorrect sealed enclosure design could result in sub damage as well. Sealed enclosures demand greater excursion limit.

Are you talking about Acoustic suspension units or sealed enclosures. Drive units meant for acoustic suspension loading are extremely sensitive to the boxes internal volume. Units meant for sealed enclosures are extremely tolerant to internal volume because they rely on the spiders and diaphragm rubber or neoprene surrounds rigidity to keep the in/out motions in control. Enlighten me I could be wrong; its been years since I meddled with enclosure designs for acoustic suspension boxes.

Quote:

Originally Posted by Invinsible (Post 1743682)

2. Well incorrect sealed enclosure design could result in sub damage as well. Sealed enclosures demand greater excursion limit. On long run if the sub is not able to handle the low end response and reaches or goes beyond it excursion limit could have adverse effect.

???

Quote:

Originally Posted by drpullockaran (Post 1743966)

Dear Dr., nearly all of the subwoofers used in cars end up in acoustic suspension with the exception of free air subs, which even if put in a tiny enclosure still have stiffer and more rigid suspensions than what is offered by the enclosure.

Invinsible - There is no 2 ways about it. ANY subwoofer driver is relatively safer in a sealed enclosure than a ported one. Mainly due to the unloading that takes place below tuning frequency.

Quote:

Originally Posted by naughty001 (Post 1742453)

As for the concept of thump, that is not really music. when you listen to a set of drums unamplified or even a bass guitar or double bass or a Cello you will never ever hear a thump. So why it is that people like to hear an unrealistic thump is a mystery to me since that is not entirely musical. The subwoofer was originally designed to provide the lowest reaches of frequencies that these instruments can provide and when tuned properly will just add a "feeling" of warm richness to the sound instead of huge thumping sounds that can blast you into orbit ..... but then again that is probably a subject for another thread and not this one

Interesting point, naughty. Maybe it DOES deserve a new thread after all! :) So you mean that all that music we hear in rock fests and concerts has basically added artificial thump?

Quote:

Originally Posted by Invinsible (Post 1743682)

2. Well incorrect sealed enclosure design could result in sub damage.

I never discussed or refered to damage. WHat I was trying to say was tehat ginve that most od us do not have Clio, MLSSA, LMS, etc.. and cannot measure the woofer we are working with it always preferable to get a woofer that is desifned to work in a sealed box. THis way even if there is a deviation from the published specs (manufacter's recommened box size is based on published specs) the variation of the frequency response will not be as much if the woofer in question was one that was designed for a ported box and put in a ported box.

1. Hypothetical Sealed box woofer
published
Fs 30hz
Qts 0.4
Vas 50 liters

measured
Fs 33
Qts 0.45
Vas 45 ltiers

Stuff it in a 25 liter box and the variation in response will be much less than if we used

2. Hypotetical ported box woofer
published
Fs 25
Qts 0.25
Vas 80 liters

measured
Fs 28
Qts 0.23
Vas 75 liters

Manufactuers base their published specs on a weighted average of the measurements of a sample lot.

Any variations from this will affect ported box woofers (Qts <0.3 for example) more than sealed box woofers (Qts > 0.4). Besides most often the varitions with sealed box woofers leads to a Qts that is HIGHER than published specs (there are many exceptions but we are talking in large general terms).

Also if the Qts is much higher (leading to a high Qtc) than published (a woofer system where the Qtc is high will have a peaky one note bass) one can compensate for this in a sealed box by going aperiodic and tuning by ear. The same can be done for bass reflex but it is much more diffcult to change port length that just to change the denisty of the damping in the aperiodic vent.

Quote:

Originally Posted by Bass&Trouble (Post 1744208)

Invinsible - There is no 2 ways about it. ANY subwoofer driver is relatively safer in a sealed enclosure than a ported one. Mainly due to the unloading that takes place below tuning frequency.

Exactly. Somehow I cam to this conclusion some 30+ years ago jsut from emperical testing and fooling around with Philips, Bolton, Arphi, drivers.

I started "fooling around" with audio in 1972 and I can remember the eureka moment (1976) very clearly. Nestorovic and Aperodic loading were also results of this eureka moment. I did not even know that the terms already existed (no internet access and few magazines available in India).

Quote:

Originally Posted by jsmonu (Post 1762122)

So, if you could just summarize.. what actually did solve the problem ? Was it just the new HU or was there tuning to the amp ? etc etc? :)

J.

I think it was the wiring. I made the guy pull everything out and re-install it and the problem was solved.

Afterward when I got my demo with HU the sound quality was improved a little bit, as Sony x-plode HU was outdated wanted to upgrade so ended up buying Pioneer HU

By the way I also got JBL 200W front speaker's and got rid of pioneer 160W

Now the sound effect is perfect.