Installing speakers

[45aken]

i know what you are saying, but this concept is more to do with subs, esp in ported boxes. you can 'tune' the ports to suit the resonance of your 'car'. a sealed box give a good linear sound, whereas a ported box will 'amplify' the resonate freq and give a non linear sound due to some freq's being lounder than another. since you will be using a full range speaker, you will want a linear sound, so a sealed box is the way to go. anothr good thing about sealed boxes is they dont really change the sound too much with different sizes, so you can just build a box that fits, and as long as it isnt too big, it shouldnt matter.

[ndgcpr]

Ok i currently have

2 x 6x9's in the back parcel try on those angled spacers so i didn't have to mod anything on the parcel tray (spacers not boxes)
2 x 10cm speakers in the front
1 x 10inch sub in the boot with an amp.

and its sound quality is awsome. if you spend the time to do the maths and tune everything properly then you would be amazed how good it can sound. I am not a fan of the myth that 6x9's are crap. if you actually spend the money on decent ones then the will sound good. I am running 6x9's with a sub and they work together (cause i have heard alot of people complaining that they will work against each other)

Anyway lets answer the question that was asked. I currently have a program that will do gain curves with respect to box design. yes it is mainly used to do subs but it is just as easy to design a box for any speaker providing you have the correct speaker parameters.

PM or email me and i will email it back to you if your after it. I custom do all my stereo designs and your in QLD so if your near me i can even give you a hand with everything.

[river]

Hi,

The size box required for a speaker is dependant upon the design of the speaker and its damping (Q factor), plus other attributes. All the maths was done by some guys called Thiele and Small (I think that's their names).

The best sound, as mentioned, occurs when you separate the sound pressure coming from the front of the speaker to the sound pressure coming from the rear of the speaker. That's why speakers are put into boxes 'cos a box separates the rear sound pressure from the front of the speaker. This is often called an "infiinite baffle" system.

But to get the optimum performance from your speaker you will need to know the Q-factor and the free air resonance of the speaker plus some other details. Using these figures you can then derive the required volume for the speaker box for that speaker. Making a box too small or too large will not provide you with the best sound performance for that speaker. It's sort of like Kellogs "Just Right" - too small or too big are no good, you need to get it just right.

If your speakers do not come with any information regarding coil resistance, Q-factor and free air resonance frequency, then you can derive these by doing some tests - but you'll need a multimeter, a small amp, a frequency generator and a known fixed volume to test the speaker against.

Some speakers are designed with a high Q-factor and others with a low Q-factor. A high Q-factor speaker is one that has good damping qualities, which means it works best without a lot of internal speaker box pressure to make it work. These speakers work best in a ported (or vented) enclosure - which is those boxes with a hole (well, actually its a pipe) beuilt into them. The box volume is still critical but so is the diameter of the pipe and its length to allow the speaker to operate down to its lowest range (which is at the -3db mark). If the box volume, pipe diameter or pipe length are incorrect for that speaker then you'll get muddy sounding bass, or poor bass, or worse that real bad doof-doof sort of bass that colours your music poorly.

A low-Q speaker is the opposite and needs some air resistance from the box to help with the damping, and therefore these speakers work best in a sealed box.Again, the volume of the box is critical or the speaker will have the same sound systems as mentioned above. A closed box needs to be airtight. So you need to run sealant around all the edges and rubber gaskets or something similar around the lip of the speaker. Any air leaks will reduce the sound quality of the speaker. Same with the ported speaker box design - you'll need to make sure it is air-tight except for the port/pipe.

Some mid-Q speakers can be placed into either a ported or closed speaker box. A good manufacturer will often supply the Q-factor and other details plus the recommended box volume. With mid-Q speakers they sometime give you the closed box volume, and the ported box volume along with the required pipe length & diameter.

When designing the speaker box you need to make sure you do not use exact ratios for the various dimensions 'cos this causes harmonics and resonance at certain frequencies and will also colour your music. You don't make the height of the box twice that of the width, etc. I cannot remember the ratios but I'm sure you'll find them on the net. In other words, you just don't bang togther any old box with the necessary volume. You need to be sensitive of the hieght, width and depth dimensions of the box.

It is always wise to at least put in some sound absorbing material on the rear internal wall of the speaker box. This deadens the reflected sound from the rear of the speaker and stops it bouncing back and affecting the cone/sound. You can also put sound absorbing material on the internal sides - but it is not often necessary to put it on the internal front wall (ie where the speaker is mounted). You can fill the box with sound absorbing fibreglass stuff, but make sure it doesn't push against the cone of the speaker. Filling your speaker box with this stuff has the effect of increasing the volume of the box, but can also deaden the sound. It's a touchy-feely thing. I prefer the absorbant stuff on the rear and sides only and avoid the loose fibreglass stuff.

MDF is excellent for making a speaker box. It has the natural density to avoid resonating with the speaker. However, you will need to use stuff that is at least 8mm thick. Anything thinner will flex with the sound and reduce the performance of your speakers. If you are running larger speakers or subs and want to pull some serious sound out of them, then you'll need to go for 12-15mm MDF. A serious home system would be better with 20-25mm - but remember MDF isn't light and the speaker box can get pretty heavy. You don't want 5 to 10 kg of speaker box slamming into the back of your head in an accident. Avoid plastic boxes - they're woefully inadequate.

At the end of the day, after all the maths and other stuff, the best way to judge speakers is to listen to them and if you like what you hear, then go for it.

Well, that's about all I can think of. Hope it helps in some way.

seeyuzz
river

[andy]

everyones an expert.
i always wanted to make boxes for my 7x10s, but nowhere to put them.

[45aken]

mate your system probably does sound good, but when you have a system that is worth $8K+, there is not too many 6x9's that will keep up if you know what i mean.

RAd28-> i'd just go with a sealed box for the 6x9's, shouldn't really matter too much about size etc. my bad on the comments before, was a misunderstanding.

[ndgcpr]

well done river, and for serious speaker stuff i don't go below 18mm MDF, but i guess if your building a box for a small speaker you could probably go lower, 8mm seems a bit low to me though.

45aken
Yeah i guess i know what you mean, hope mine post wasn't taken too bad, but for this cars setup i wouldn't hesitate on putting 6x9's in.

[faulksy]

thanks for all the responces guys...

basically what i really need to know is how to find what volume to make my boxes?
the reason i need boxes is simply 'cause i have nowhere to mount them... it's a RA28 after all... my plans were to make boxes, then mount them to the back of the rear seat so they sit just high enough to peer over the back, but not high enough to obstruct the rear view by much if at all...



i HATE when people say this (no offense to you)... you've obviously been spending considerable time listening to the guys from your local car sound shop? i have absolutly NO idea why these guys bother telling people this... because if that's the case answer me one simple question... why did they invent 5.1 surround if you get best sound with 2.1? forget a band stage senario, what about real life? do we have 2 speakers infront of us everywhere we go?
having said that, i understand exactly what your saying RE ditching 6x9's for the likes of 6.5" components and a sub.



ummmmmm sure...

maybe think before you flame. if you dont want constructive feedback and opinions many steer clear of forums. what type of music comes in 5.1??/ surround sound music??? i have failled to ever seen a concert where each singer stands in a 5.1 format to gives us the feeling of surround sound

5.1 is for movies etc. where sound is directional is put in place to improve the movie experience

and sorry i missed the bit where i said "no offense to you". i was trying to contribute my knowledge i have gained in having car audio SQ as a hobby. while i respect your opinion you believe 2.1 is worse for SQ then 5.1 i remain unswayed. 2 fronts, 2 rears, and a sub sont make it 5.1. thats still a stero setup. my opinon is common knowledge on CAA forums and might be an interesting read for you.

ill stay outta of your theard cos im not here to argue

[faulksy]

mate your system probably does sound good, but when you have a system that is worth $8K+, there is not too many 6x9's that will keep up if you know what i mean.

RAd28-> i'd just go with a sealed box for the 6x9's, shouldn't really matter too much about size etc. my bad on the comments before, was a misunderstanding.

agrees. my front stage amp has a RRP of $4k alone. i dont know of any SQ/SQL setups with 6x9's

[Lambolica]

agrees. my front stage amp has a RRP of $4k alone. i dont know of any SQ/SQL setups with 6x9's

They are out there but not very common anymore and generally used in minimal speaker/power setups. That being said i haven't seen any in the last few months.

[o_man_ra23]

For SQ ive always found full component systems with either passive or active crossover networks (not just a shitty capacitor to cut the LF outta ya 2/3 way high freq speakers) will crap all over full range speakers. My suggestion for a simple system for RAD28 would be an 8" or 10" sub in sealed enclosure, and a pair of component 2 way 4" speakers up front. The front speakers can happily be run off any reasonable/worthwhile head unit, and a very small 2 channel amp bridged will easily run an efficient (non-SPL) 8 or 10" sub. Having the speakers up front means there is less audio attenuation in the mid and high freq range, which will become an issue if you put the speakers in the rear, esp up against the tailgate(even when reflecting off the hatch glass). Low frequencies which are produced by subwoofers arent as prone to this attenuation, and will also penetrate your back seats without much trouble.

My advice is to spend the extra on a full component system, and integrate the front speakers into your door trim(make new trims if necessary), as 4" speakers wont require the cutting of RA28 door metal.

But hey, do what ya want.

Cheers, Owen

[o_man_ra23]

Oh yeah, i used to have a pair of $80 sansui 6" splits which ate almost any 6*9.

Cheers, Owen

[Dylo]

I used to have 6x9's in my RA28. Easiest place to mount was to make up new mdf plates to mount the speakers and mount them on each side of the back seat in those funny little holes that are there. Trimmed them like my interior and mounted the diagonally so no cutting was required.

Do you know what i mean?

[Squid]

maybe think before you flame. if you dont want constructive feedback and opinions many steer clear of forums. what type of music comes in 5.1??/ surround sound music??? i have failled to ever seen a concert where each singer stands in a 5.1 format to gives us the feeling of surround sound

Dave Grohl ran into the crowd at the foo fighters concert I was recently at! Just cos the mic and guitar pickup still drove the speakers on the stage doesn't matter. But to agree with faulksy, you never see a band set up rear speakers for their concerts do you?

But I agree, 5.1or 7.1 is to create the '3d' effect, which is not useful for CD's which are recorded in stereo.

I put the 3d in inverted commas because 5 speakers all at the same height will only give you a 2d effect, you would require speakers with elevation to generate a full 3d experience. *squid ponders why this hasn't been done for cinemas*

By the way I do have some speakers for rear fill, mostly because there is a large gap between my front 4" splits and my sub, the rear fill speakers I got overlap both, and I have found it hard to get it sounding just right, need to make a BP filter I think.

Anyway enough off topic rambling, river pretty much answered the question in more detail than I have ever seen it explained in one place. Wise the old man is +rep

[mic*]

The "myth about 6 X 9's" has strong basis for SQ ppl. They are the best example of a speaker which is designed for full range reproduction. Thus to the average listener there is huge appeal in that one speaker can do the lot. However the general viewpoint of an audiophile is that they produce the whole range well, and no particular bandwidth superbly.

Boxing them has limited point because as mentioned they are always coaxial (or they wouldn have any range) and thus you cannot seal them in an enclosure, nor can you design a port that compensates for air gap around the post.

I am sure you would still gain some benfit from boxing them as it will always improve the control of the speaker to a certain point - the small danger is that this allows a lilttle more amplitude to be pumped through and with a bad port design or a hole in a sealed box there will exist random frequencies at which your speaker will resonate strongly and could cause damage.

If you must box them for mounting purposes the best general rules for building a sealed box that i can give are;
- Volume equals roughly 3 x cone volume
- Avoid parallel walls particularily in the plane of the cone movement
- Seal as perfectly as possible
- Curves at the joins are great where possible (eg 1/4 secion of pipe stuck along a 90deg join.
- Use MDF i reccommend min 12mm


In response to some of the other comments;
- Sound from the back of a cone is NOT 180 out of phase. It is simply being propogated the other way. Think about it as i hope this is not the result of your 1/2 year study.
- Many music CD's are recorded in 5.1 these days and many people install DVD players and so forth in cars too so the desire for 5.1 is not unfounded.
- The sound being reproduced in the surround channels (RL & RR) of any 5.1 recording is exactly that "surrounding sounds" ie ambient noise like traffic or birds chirping. The focus or sound stage is still ALWAYS IN FRONT OF YOU. Thus surround speakers are smaller and *usually* have better high Hz response, so what is the need for equal or larger speakers for the rear in a 5.1 targeted setup???
- Bugger all source units available reproduce radio or CD in 5.1 regardless of how the source is recorded. The channel called CENTRE is split over the four standard outputs to give an equal amplitude sound in each channel at neutral balance & fader.

[GTtwin]

Boxing them has limited point because as mentioned they are always coaxial (or they wouldn have any range) and thus you cannot seal them in an enclosure, nor can you design a port that compensates for air gap around the post.

Not trying to be a prick but I beg to differ.