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Author Topic: Making speaker boxes HELP! (size)  (Read 4972 times)


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Making speaker boxes HELP! (size)
« on: July 11, 2001, 11:55:23 AM »
!!!! I havent got a clue about this whole "sound" thing.

Ok, im  making dodgy speaker boxes in my rear parcel shelf (f' all space) so that the speakers are angled up, facing about midway along the roof, instead of straight up into the rear window.  (cant hear them properly.)

Pansy little aftermarket 6" 3ways (1 JBL, 1 unnamed)
Ive made 1 box, but it just occured to me, do i have to make the volume of the box to a certain ratio respective to the speaker size?

box is shaped like a triangle from side on.

Should I run both No-name (but still OK sounding) speakers in the rear, or the remaining un-blown JBL?

Thanks a lot guys!


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« Reply #1 on: July 11, 2001, 02:05:10 PM »
I've got an 86 skyline with Kenwood 7*10 in the rear parcel shelf, they sound awsome, they do the job of a 10"sub nearly.
While there is sweet F*** All space in the back, it can be done pretty easily.  Making a parcel shelf that is.

Get some 18mm mdf 1800mm*600mm and trace your old parcel shelf on to it.

Take out your back seat, lotsa fun if its a split folding like mine.
Take out your shelf.

Trace the round 6" speaker holes as well, mark all holes where bolts go through so you can drill them out.
Remember to cut slots out for your seat belts. 5-7mm slot
Trace the line real close, cause when you put carpet on it's a tight squeeze.

Jigsaw Time

Cut out all your main shelf shape first, then you are going to taper the window edge about 45 deg.
Cut out the speaker holes.

Sit in the car and see how it fits, as you may have to trim more wood off, use a file/rasp to trim and mould till it fits perfect.
Allow a few millimeters for carpet.

Make sure when you trim wood, that you get speaker holes lined up perfect as the magnets sit very close.

With shelf sitting in sit speakers in and see how it all fits.
When your happy with it all carpet it up, go to autobarn for this, get the thin stuff they use on sub boxes. It's easily glued on and has a nice finish.

Bolt the bugger up with 3 bolts (big ones) and washers.
In the middle where kiddy seat bolts in. Other 2 holes near speaker, they may be filled in with tar, push it out with a screwdriver and put the bolt in.

Thats pretty much it.  I got quoted $300 to get this done, i laughed in his face so hard in the shop with everyone looking,
and said loud " thats a rip off i can do it for $50"
It cost me less.

Wood  $11
Carpet $ 15-20(depends on type)
bolts    $4.95
4hrs labour


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Making speaker boxes HELP! (size)
« Reply #2 on: July 11, 2001, 02:52:26 PM »
damn thats a good idea.

BUT dont you have to have some sort of box/enclosure for the backs of the speakers??

I have split fold (put them in from my wreck)....4 things to unscrew, and the entire rear seat setup is out :D


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« Reply #3 on: July 11, 2001, 05:27:47 PM »
nup dont need to be boxed, leave it so you can see bottom of speakers from the boot through the holes.

The boot of your car acts as the box.


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« Reply #4 on: July 11, 2001, 11:03:29 PM »
Firstly, 7*10's don't sound nearly as good as a 10" sub. not for $&%*! Secondly, use boxes for your rear speakers as they sound much better and give crisper more authoritative bass. Free-air enclosures are a bit of a wank, just for the people who cannot afford boxes or can't be bothered buying them. Speakers perform better when enclosed, laws of physics fellas. Have fun building your systems, if can't afford good gear save and then buy it. Bad speakers won't last long as you will want to pump the volume and then they wil clip and be dead as. Just spend $150 on a set of pioneer or kenwood 3'way 6.5" and a single cd unit for $250-300 with single rca's in case you want to use an amplifier later.


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« Reply #5 on: July 12, 2001, 01:46:29 AM »
I dont mean to sound offensive, but have you ever looked in the boot of an r31 sedan.

1. The metal shelf is uneven, so you would have a fun time trying  to bolt any form of enclosure. How would you get a perfect seal between wood and metal.

2. The springs/rod that lift your boot run directly under your speakers with a few millimeters to spare.
3. You would have to go to the trouble of calculating the volume etc.

4. The rear wheel strut only sits a few more cm below the speakers & metal shelf.

So in order to fit a box in for shelf speaker you would have to get rid of your boot springs and rear wheel struts, but hey you would have a great stereo.

Also i did not say that 7*10 are as good as a 10*sub I said nearly.  No 3way cabin speaker can outperform a dedicated bass driver.

I've had these speaker set up my old vc commdore, sounded good except the boot was too big, and the cabin area was too big. not enough bass, low boom.

Ive set them up in a VN,VP,VL GEMINI, sound good in all.

Now the skyline has a smaller boot smaller cabin & better acoustics, also better rubber seals all round.
They sound a sh*! load better, and pump, running off 3/4 the rms power they should be. Good tight bass.

Then you imply i have a sh*! setup, huh.
Have you seen or heard it.
That Clarion head unit with built in DSP, geez it's crap must throw it against a brick wall someday.


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Making speaker boxes HELP! (size)
« Reply #6 on: July 12, 2001, 01:57:48 AM »
Just while i'm still on my high horse.

I always get asked what type of sub have i got in there,
and i just say kenwood 7*10's no sub.
They then go on to comment i could swear you had sub,
i heard it all the way down the street.
Trust me they are damn loud with plenty of bass.


  • Guest
Bass Boxes
« Reply #7 on: July 12, 2001, 07:44:04 PM »
Just a couple of things I have picked up in my travels talking to Audio Installers, they say if you are into techno, dance with heaps of bass, do not put 7X10's in your back shelf, make a good sealed box to suit a 10", 12" or 15' Sub to sit in your boot and leave the holes were your old speakers where and cover them to let the sound out . I have seen some huge speakers put in the shelves and the Compresion from the speakers seperate the boot lid from the bracing ending up with a floppy boot from outside, Funny (not) and put a good set of splits in the front, as that is were you sit HMMMMM and you will get the bass comming from the back. And if your are into rock/Heavy metal then that is another story, then you head the 3 ways in the back and a good set of of splits in the front.  I hope this helps a little.
« Last Edit: July 13, 2001, 12:17:21 PM by R31Heaven »


  • Guest
« Reply #8 on: July 13, 2001, 01:50:44 AM »
Firstly, did I say you have sh%$ set up? huh? NO. Secondly, Clarion make perhaps the best single cd head unit ever built. Thirdly, it sems like you have no idea about sub bass and speaker bass. A sub produces different waves down to 50hz that a speaker cannot produce. That is what a sub is for. On the tracks you listen to, you will get bass on a sub that you won't get on a 7*10. My friend has Kenwood 7*10s and a 12" sub, so I think I now what I am talking about. I am not saying that your 7*10's don't produce bass. They produce a hell of a lot of bass but not sub bass and are totally incomparable to the bass a sub produces. Their purpose is as a coaxial driver, that is to produce high and mid frequencies with very small amounts of low frequency bass. They are an excellent speaker but a little too bright on the high frequencies. You also say they produce good tight bass using the free air enclosure - you obviously haven't heard good tight bass before. To make them perform at their best, like any speaker, each cone needs an individual enclosure. Without one they are still good, but no where near as effective as ones with boxes. Think kick panels with splits - heard of them?

When you talk about speaker enclosures, you really don't know what you are on about. If you don't go to the trouble of calculating the correct volume for the driver, why do you bother buying the equipment in the first place? Anyone who knows anything about audio knows speaker enclosure size is the most important factor in determining the effectiveness of the driver! Have you ever seen a 1969 Alfa Romeo GT-V parcel shelf? NO, try installing a set of 6*9's in that and then come complaining that your 1980's skyline has no room back there. Of course I know how much room there is back there, I looked at heaps of sedans before I bought my wagon. Build some boxes for the speakers, build a parcel shelf out of 18 or 24mm mdf and join the boxes to the shelf, then angle the boxes diagonally towards the roof so that 3/4 of the box is above the shelf and 1/4 below (or thereabouts). Cut a hole in the metal (yes very time consuming), and have the boxes just sitting above the springs so most of the box is actually inside the cabin and angled at the top of the windscreen. No matter what you say, until you have heard 7*10's in separate enclosures, you cannot comment on how good it sounds using the "sealed" boot in the skyline.

When you say they are running off 3/4 the rms power they should be, do you mean they are just running of the headunit? If you do, you have just stated you complete and utter ignorance as wrms cannot even be stated off a headunit. Sony, the most powerful headunits you can get at the moment at 4*65w are rated at 4*19.5wrms. Hope you understand that wrms and w are totally different things...if you are running an amp then i understand. If not, Kenwood 7*10's are rating at 280w or 300w, depending on the model, which is about 110-120wrms. That means you say you are giving each speaker 85-90wrms? Dreaming!!! Even when bridged into 2 channels, the headunit will only produce 2*25wrms as an absolute maximum. :dfinger: :dfinger:


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Making speaker boxes HELP! (size)
« Reply #9 on: July 13, 2001, 07:45:22 PM »
Isn't it great that we can all have an opinion on this car audio topic!

One of the comments stated that they got asked what sub they had in when the 7x10's were in the car.  I took my Skyline down to the audio installers that I have been dealing with and showed them my install in the rear for a set of Inifinity 6 inch two-ways.  They asked how I had got the subs in so quick.  There were no subs, just the two speakers in the parcel shelf.  This is a question from guys who have been installing for at least the last 20 - 25 years and who have built some awesome stereos!.

That parcel shelf was an 18mm custom job, sealed and fitted to the steel in the back of a R32 skyline.  My point is, good installation is the key to all things.  Key also is to make sure no sound "leaks" from the back of the speaker to the front.  This causes wicked distortion and other probs.

I tried to box things around these speakers, but they just didn't get that much improvement to be worth all the hassle.  Besides, I want all my bass to come from the boot and sound like it is in the bonnet (time alignment!!!) so why would I want more in the parcel shelf?  Ever go to a concert, turn your back on the band and then listen to them???

Make some good pods for either the kicks or the front doors, get some 6 inch splits in there, put some 6 inch 2-ways on the parcel shelf, a couple of 10 inch subs in the boot, an amp for the fronts (2x100w), amp for the rear (2x50) and an amp for the subs (as much as you want, I run 2x200 bridged)  and you are away laughing with a competition system.

Then comes the real work, installing it all to get the most from it.  One of the best systems I have heard recently was in an old Toyota Corolla station wagon using all medium range Kenwood gear (don't like Kenwood much).  This system rocked.  Time alignment brought the bass to the front, the singer to the middle of the dash, and the band out on the bonnet.  I was hooked.  I am saving madly for Alpines time alignment processor.

Thats enough of my raving guys, all I wanted to say is keep up the discussion, it helps us all to learn.



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« Reply #10 on: July 13, 2001, 08:40:39 PM »
ok folks heres how it works
and yes this will be quite technical

6x9" and 7x10"  speakers were designed for the person who wanted moderate to large amounts of bass without breaking the bank or reducing your boot space thats why they have a large cone area and are oval so they fit in almost all parcell shelves.

they are also designed not to require a box/enclosure, but can also be used with an enclosure to extend bass response .

they do not require a box because of the nature and design if the driver as ther are a high "Q" driver, the total "Q" of any speaker is derived from a number of properties that each speaker has, these being :
 1) Zn           = Nominal Impedence (in ohms)
 2) Zmin        =Minimum impedance at frequency
 3) ZOhm       = Maximum impedance
 4) Le            =Voice coil impedance
 5) fs             =resonant frequency
 6)Qms          =mechanical Q factor
 7)Qes           =electrical Q factor
 8)Qts            =total Q
 9)Cms           =suspension compliance
 10)vas          = equivalent volume

there are more propreties but these are the main ones use to calculate correct box volume

to calculate the correct volume of enclosure you first need to select what frequency responce you want to have and then usualy plot these figures into a box plotting program and it gives you the answer .

there is not 1 correct box for any 1 speaker but there are optimum enclosures that work exeptionaly well with the desired speaker.

different speakers work differently and to make a good box i suggest downloading some freeware box design software and experiment (theres nothing wrong with trial and error)

if you want to use 6x9" or 7x10" speaker and not use a sub by all means go out and do it

but on the other hand, if you want real BIG BASS theres no substitute for a properly built subwoofer

so i suppose the best thing is to say; to each their own. There is no best sound system, each person has their own likes and dislikes.

So just remember what sounds good to you, might sound bad to someone else.

Sub Boy

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Making speaker boxes HELP! (size)
« Reply #11 on: July 26, 2001, 09:12:40 PM »
Wow....Some of you fellas have some pretty crazy ideas on audio!
 No, do not box your rear speakers, They are designed to use the boot or the door as an enclosure, anything smaller (like a little box hanging under the tray!) will sound like crap, may do damage to the speakers themselves, and limit the freq that the speaker will play down to.
 Yes it is true that a well installed set of 7x10's can sound like the car has a sub in it, But a well set up 10" or 12" sub will always extend lower and sound less strained the the big ovals.
 Yes, Try to avoid having any air gaps between the front and the rear of the speakers as you will create cancelation (An in-phase sound mixing with an out of phase sound)
 P.S InfinityR32, There are a couple of PRA-H400 time/alignment processors for sale on the Canze site, I used to have two in my Pro Class Levin, They are the Go!:homer:
"You should never under estimate the predictivity of stupidity!"


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« Reply #12 on: July 27, 2001, 12:05:05 AM »
If you had read the entire posts - THERE IS NO ROOM IN THE TRAY OF AN R31 TO INSTALL SPEAKERS! This was the point of the original topic! Furthermore, have you ever heard boxed 7*10's? OBVIOUSLY NOT! My friend has his boxed and I don't think I have ever heard such crisp mid-bass, while another friend has his on the tray and the boxed speakers put his to shame.

Boxed speakers will not damage the speakers
If you know anything about car audio, you would realise i meant constructing a whole new parcel tray out of 18-24mm mdf and attaching the boxes to the tray so they don't vibrate

Neway, too many arguments so just let it be known that boxed speakers will sound better if the enclosure is the correct size


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Making speaker boxes HELP! (size)
« Reply #13 on: July 27, 2001, 04:40:56 PM »
Hey there Sub Boy, glad to see that someone who knows what they are talking about has joined the conversation.

For all the rest of you out there that don't know Sub boy, he has competed, with a great deal of success, in New Zealand for some years in car audio comps.  In the PRO class.  so he has some idea of what it takes to build a sweet sounding system.

Chris, found any of those GTR's you are looking for yet?  Would like to see how you go about installing a decent system in these suckers as they are damn small inside, a bit like the Levin I guess.

I have just bought the new Alpine 7878R headunit which has some time alignment built in from Pauls Car Audio so hopefully this will help a bit with the T/A.



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one idea
« Reply #14 on: July 27, 2001, 06:55:09 PM »
if u want to know how to  do it get the lastes
hot 4s mag as it tells u how and what u need to do as well as
giving u picutrs

maxium respict boea :zball: