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Discussion Starter · #1 ·
Ok...just some thoughts here. I'm have a couple of 12" subs I wanna build up for my new-used MX6. I don't wanna rip everything apart. So my plan is to just remove the back speakers and create two sound ports for the subs in the trunk. In addition I'll probably enclosure some 6x9 in a couple of boxes and point them to the openings.

I haven't setup a sound system in a trunked car b4...only hatchbacks. Would a setup like the one I describe above sound bad? I'm afraid coupling sound through the openings may make the subs sound like bandpass boxes (the trunk acting like the 2nd chamber) instead of my preferred sealed box sound.

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97 MX6 LS VS in Blackberry
 

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Discussion Starter · #3 ·
...and the bass comes from??

So where would the bass from the subs come into the cabin from? This means they would modulate the 6x9 with too much sound pressure and would probably kill the 6x9.

How do most people setup a subwoofer in a trunked car?
 

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Most people don't think about it and just mount them in the trunk and let them pressure the rear speakers. But since you've actually thought about it here is a good solution. Use the existing holes for the rear speakers but have a small enclosure made around them to seal the back side off from teh rest of the trunk. Don't worry about the sound from the subs getting in to the cabin. Bass sound waves are very long and powerful, they will go right through the rear seat with no problem. this is why boxes are constructed out of such thick wood, so that they can stop most of the reverse portion of the sound wave.:)
 

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Canadian Tire sells speaker covers that fit on the bottom of the speakers. Other stores probably have them too, like Walmart. They'll protect the speakers from the bass. If you use a sealed enclosure, don't worry about not hearing the bass. You'll hear it just fine!
 

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There are many people who get a little carried away when trying to put some bass in their car and are easily seduced by the wrong marketing ideas.

More is not always better or even louder.

6 by 9's are designed to do a certain job, that is to play a full range sound, if they are then asked to share the same magnet air space as some other speaker like a set of 12's the 6 by 9's will be over shadowed and the sum total of all those speakers will be less than desirable.

In an ideal world there would be no direct full range sounds coming from behind you, maybe some reflections, just sounds from in front of you.

You need to have the bass in the trunk as this is the easiest place to put it, but I would suggest that if you have 2 x 12's then lose the 6 by 9's. DO NOT try any fancy porting, IT WILL NOT WORK,there is a science to porting boxes, it can NEVER be done by guessing and sucking and see, just get a decent well designed box for those 12's and allow the bass to breathe into the car through the holes that were for the 6 by 9's.

Those speakers then need to be cut off at about 100Hz or less, my experience has shown me that in an acoustically well sound deaden MX6 then between 65-85hz is ideal, but this does require a reasonable amount of power and some good bass speakers to start with.

Although I do not advocate my personal preferences for everyone, of all the people in this group I am probably the one mad person who has spent about 300 or more working hours just trying to get audio perfection in a MX 6, for those who haven't read yet, check out http://www.efmax.co.uk/serv01.htm and see for yourself.

Bass in any car is easy if you have reasonably good speakers and a very good enclosure, in our car the bass capabilities is totally amazing when done right.

For those just starting out or working to a budget, the smart way forward in our cars is like this.

Change the xover points on the front tweeters or change the whole units completely for something better, then run them from your front channel output from your head set.

The front door speakers can be replaced by something better of the same size and can be run from the front channel of your head set but better would be to run them from two channels on a power amp.

The rear speakers can be left or removed, if left then run them from the rear channel from your head set, DO NOT use a power amp on these speakers if you have a sub bass unit in your trunk.

If you have got a sub bass unit in the trunk, then lose the 6 by 9's. and power it from a dedicated amp or from a bridged mono input from a 2/3/4 channel amp.

Start off your setup trials by first getting the front door speakers sounding just right, then balance the front tweeters, then if you still have them bring in the rear 6 by 9's and only then do you balance the sub bass with the rest of the system.

Try and see and email me if you need anymore help.
 

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Discussion Starter · #7 ·
Much to consider

EF MAX...thanks for the pointers...very nice setup on your 6 btw.

I'm pretty knowledgable with the audio stuff from hanging around on audiophile boards and being an EE major. I've also built up my own speakers for home. But the car cabin is a different story.

NO rear speakers:
I haven't really considered this. But I guess to achieve a true stereo soundstage I should only use 2 full range speakers. I must admit though, a proper 4 speaker setup does produce a nice soundstage. I guess if I rid of the rear speakers my rear passengers will just have to live due with only the pounding bass on their backs.

USING the rear speaker wholes to couple sound into the cabin:
As with you EF, I believe keeping the holes open will produces much better results than closing them off. I'm sure trying to couple bass through the rear seats gotta do some messed up stuff to the freq response. But still, I wonder how well coupling sound though the holes will sound. As I mention in my initial post this can be modelled as a bandpass system where the speaker box is the 1st enclosure and trunk with the holes is the ported 2nd enclosure....Maybe..maybe not? Any experiences with this method.

Cabin transfer functions:
I haven't read your website completely, but I'm sure you have some good info on cabin transfer characteristics and where cabin gain really kicks in. You mentioned below around 65-85Hz...that sounds like a reasonable point for cabin gain.

Good box design:
The other thing I was wondering was if you had any experiences to share in terms of box tuning. I noticed you choose a bass reflex system for yours. Was that just SPL motivited, b/c from what I've read, cabin gain is typically an 2nd order roll up, which matches perfectly with the 2nd order roll off of a sealed box. If you have experience with sealed box, what QTC would you recommend building the box to?

regards,
Doug
 

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Hi Doug

Thanks for the kind words.

For me soundstage is everything, as I compete in car audio competitions, the perceived wisdom is that rear speakers are out. It is only when you hear a well set-up car that you start to realise why.

In our car having a box in the back and breathing through those rear speaker holes is just ideal. As for how it sounds, if the box and speaker combintion is a good match then the sound will sound good if the holes are filled and better if they are not.

It is all about coupling the air from the bass speakers to the same air space that your ears are in. When the air is blocked it is harder to get that just right effect, but when there is no resriction it is amazing.

My current car hits about 150dB and this box was design for SQ not SPL.

As for Band Pass Boxes, these have always been my favorite but I have come up with designs that are equally as efficient and just as lethal in the low bass department whilst still remaining good in the Sound Quality department.

I have my own design which I call a Triple Chamber Dual Reflex Bass Design, it is what my current box is based on and the design is efficient like a bandpass box, loud like a vented box but also smooth like a sealed box. It took me many working hours to perfect but it works very well with a modest powered amp and it KICKS with a serious amp.

With what you are referring to, you would not get a bandpass effect because you would need a totally sealed construction for the ports to do their job correctly, though I can see where you are coming from.

As for transfer function, boy that is one animal that takes some real brain power to work out and I am still learning on that one but in our cars if you want SQ you have to build this into the box design, so to if want out and out SPL.

As for box tuning, go back to my website and look at the page for designing a bass box http://www.efmax.co.uk/box.htm and also http://www.efmax.co.uk/db1218.htm both of these will explain a few things, there is also a link to JL Audio tutorials, on their website which has info, some of which I have, with their permission, reproduced.

Different boxes sound different in different cars and each car owner has different needs, so no one box is perfect for everyone, it is all about compromises, hence my box the dB128, but it is a box that is big and not to everyone tastes, that said I have design scaled down versions of which Car Hi FI, UK, tested one with a single 10" and it still remains the loudest 10" box that they have ever tested, even out performing an MTX box with three 10's in it.

When it comes to QTC, if you want sonic perfection, then go for about 0.7, if you want extended bass but at the expense of boom then go between 0.7 - 1.2. More than 1.2 is often very one note type of bass and doesn't sound good at all. Less than 0.7 will often sound too flat and lifeless.
 

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Discussion Starter · #9 ·
EF MAX....QTC....isobaric

I've always known that QTC of 1/sqrt(2) = 0.7071 was ideal from the audiophile world. But things change in the autosound world, with cabin gain and all the other good stuff that comes with putting a bass box in a bigger box (your car). So I guess, you're saying to stay with the audiophile mentality here.

Too bad the woofers I pickup cheap ($30 for carbon fiber/paper cone, 400Wrms, cast frame basket) need 2cu ft for a QTC or 1.2...not worth mentioning the size for QTC of .7. For a dual 12" you can see my trunk dissappearing. Ah well, maybe I'll uses these woofers for my home theatre system instead.......or maybe I'll go for an isobaric configuration. Have you ever tried thoses?
 

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I have tried isbaric in many guises my fav was 2 x 15 in a 6th order tri-chamber jobbie... very loud and very deep in the back of a really small car... no back seats mind you but seriously impressive bass.

When you get most car RTA you will often find that sealed boxes made around a Qtc of 0.7 will actually behave in a car, when transfer function is taken into consideration, as if the Qtc was around 0.9-1.1, for those looking for absolute sonic perfection, at least as far as an RTA meter is concerned then a box and speaker combination of around a QTC of 0.5 will help the RTA in Sound Quality readings.

Most cars these days that are into serious competitions will have EQ units and other toys that will allow adjustments.

Certainly in my car the Caliber Bass EQ unit has a dial for changing the Q of the box and it is from 0.2 - 2 which is an amzing range, I tend to have mine quite low. I know on my last amp that also had a dial for adjust the Q factor.
 

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Discussion Starter · #11 ·
Yeah...that was what I was thinking...that the QTC in the car is actually higher the anechoic QTC.

btw, what is RTA?...Real-Time Analyser? I was thinking I would need an EQ to get the sound I am looking for. Do you have any suggestions that won't break the bank?

In anycase, I think I might just give the isobaric configuration a try. Hopefully, I'll have some time in a month to start on it.
 

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Hi again

Sorry, RTA, yes you were correct.
As for EQ's, for them to do their job well they need as much help as possible, the more bands the better.
The choice in the US is so much greater than that of the UK.

If you are in the UK, then Maplins Electronics do a niffty bit of kit which won't break the bank, looks the part and does the job, and most of all it does it very well.

As for Isobaric boxes, do you have appropiate software, by which I mean more than you free box calculator off the web, as these boxes are not friendly to the midly interested designer and require afair bit of practise to perfect.
 

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Discussion Starter · #13 ·
EF,

I'm in Canada...in Toronto now...and soon I'll be moving to Vancouver.

Thanks for the suggestions on EQ's.

As for iso, never done them. I assume a big challenge is get a good seal between the two drivers. Also I don't even remember, but I thought you use VAS/2 and something else x2. I'll have to read up on it again. The s/w I have is pretty good. It's boxmodel by robert bullock. the woofers I have have a high QTS of 0.86, but I haven't played with them in s/w yet to see what I can do in a sealed, vented, or iso. I just need some free time...
 

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Canada ahh, lucky guy, all of that niceness, nice culture, nice people, do you want to swap places.

If you have Boxmodel by Robert Bullock, unless it has been revised since I last saw a copy you will need something a LOT stonger. Robert's software was great in its day especially for sealed boxes but things have got a lot more sophisticated since I last tried his software and I say that with no disrespect to the guy because he really knows his stuff.

If you have never made an Isobaric box before then as a favour, email me the details of the drivers you are going to use and the size of the box you can handle in your car, the power you will be using and the type of music that you listen to but also the rest of the audio equipment that you have in your car, because this is not a road you can walk down without some decent help and making mistakes on this type of design is real easy.

If you look back to my web site, there is a review page which tells the story of my only reviewed band pass box in the UK car mag Max Power in 1997.

It was a single six inch speaker that out perform all of the other bigger,[1 x 12, 2 x 10 etc] speakers in that review, as the reviewer said " this box kicks arse and drops bass, and it is only a six incher".

Since those days I have design far more successive speakers box designs of which my Dual Chamber Twin Reflex boxes really do deliver. On the same review page you will see a box tested by the UK car audio mag Car HiFi in 1998. This box had a single 10" speaker that so far is still the loudest box with a ten inch speaker that they have ever tested and outperformed a MTX box with 3, yes three 10 speakers in it.. need I say more.. you have fun but stay in touch.
 
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Im also an IASCA competitor out in Canada and thought I would add a couple thoughts. As far as isobaric goes, I see it as the last resort in a car. All I have seen it do is save space. It is not nearly as loud as mounting the two subs in a well-designed ported- or nice sealed box. EQs... you got a ton of choices. Most high end companies make some excellent 30 band EQs and if you want to go really nuts you could get Raine or USD EQs that I believe are really overkill. My system gets equalized by a 13band EQL and Im sure it will be satisfying once I get my new car.

If you're curious what I will be running this season:

Eclipse 5303 HU
USD BC3 HLCDs off of a Butler Tube Driver 750
Canton 8 inch mids off of a Butler Tube Driver 1500
Nakamichi 12 inch sub off of a Butler Tube Driver 750
Audio Control 24XS and EQL for processing.
 
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this set up rocks

get a half fiberglass woob box sub tward the tail of the car rip out the back speakers and hook the rear to the front. the holes in the back deck help the sound
 
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