So I'm looking to build a sound system to use in my home, something pretty much custom and too my own design but iv been told that it is not possible using car speakers and amps. Basically I'm looking at making a sub box housing a 12 inch sub (250w) with its own amplifier and two separate satellites each housing an 8 inch speaker (225w each), 2 x 4 inch speakers (100w each) and a wide dispersion tweeter (150w each). The main problem here may be that some of the components (the speakers and amps) will be designed for car (4ohm) Whereas the tweeters will be ones designed for home/dj use and are (8ohm.) This would be run from standard 240v home electrics using an inverter to drop it to required voltage and to DC if needed. Even better is it possible to run car speakers from a home amp without the amp overheating or the speakers blowing. I would rather avoid home amps because they are a lot more expensive and this may eventually end up in my van anyway.

I am also of course going to need something capable of controlling and distributing the input, namely controlling volume, bass, treble and possibly balance. Thinking of using a standard DJ mixer here, again is this possible or is there something possibly better suited to my needs such as a standard crossover which may even possibly be better/cheaper?

I cant pretend to know a huge amount about electrics but if anyone could point out any flaws or point me in the right direction to any resources which might help me design this then it would be greatly.

It's perfectly safe to run 8 ohm speakers with an amp designed for 4 ohms, but not the other way around. The easiest way to run 4 ohm speakers from an 8 ohm amp is to add a 4 ohm resistor in series with the speaker, though I'm not sure what kind of sound quality you'll get from this.

It's also fine to run a 12v car amp off household AC with the proper adaptor, but finding one with enough amperage will likely be costly.

The easiest way to run 4 ohm speakers from an 8 ohm amp is to add a 4 ohm resistor in series with the speaker, though I'm not sure what kind of sound quality you'll get from this.

It's also fine to run a 12v car amp off household AC with the proper adaptor, but finding one with enough amperage will likely be costly.
Make that 4 ohm resistor another 4 ohm speaker.

And you'd probably have to spend upwards of $50 for a sufficient power supply and it'll probably be bigger than an average home stereo receiver; I've looked into it before.
I thought about making one using a modded microwave oven transformer and, IIRC, I was told that it would require massive (read:expensive) smoothing capacitors to get a steady enough power supply that wouldn't produce a 60hz hum through the speakers.

How much are you looking to spend on all of this?


Wait for MunkeyQ to get here, he's &T's resident expert on home-brewed home audio.

Probably prepared to spend up to about £150-200 with most of the kit being second hand from friends or ebay. Boxing is a piece of piss with my best mate being an amazing chippy but its more the electrical side of things where I'm stuck for guidance. The way I see it building a custom system should eventually get you much better sound quality for your money compared to buying a system as well as being able to have exactly what I want. Being someone who listens mostly to drum and bass I want this to give me as much bass as possible.

Even better if I had this:

http://en.wikipedia.org/wiki/Valve_Sound_System

I think probably the most important factor in making a good sounding home system is designing & building suitable enclosures for the speakers & the room. It's more than just building a box and cutting a hole in it. Home speakers come in enclosures designed specifically for the speakers in it so that they will performance at their max; that's part of why you can get so much bass from a speaker that's barely moving. I bet if you put a sub that has around 1.5" total excursion in a proper enclosure that shit would fucking slam.

:D

First of all - why exactly do you want to use car stuff? Sound quality is nowhere near as good as home hi-fi speaker components as a lot of compromises have to be made; for example, car speakers have to withstand a large range of temperatures and humidity, so sacrifices are made to sound.

Car speakers (not subs) are designed to work in an infinite baffle situation, i.e. no backpressure or backwave from a cabinet. There is no speaker enclosure in a car's door, so the speaker is basically designed to work in free air. The Q, or damping factor, is therefore very high, and the Vas, or free air resistance, is also high. Designing a conventional box enclosure therefore brings no benefits to the speaker as it would have to be impossibly huge.

There is no point having an 8 inch and two 4 inch midranges in a three way system. An 8 inch driver will happily go up to 3-4khz, so a midrange driver is pointless and will result in a LOT of nasty comb filtering. It'll also sound very shouty and harsh... You'd need a midrange if you had a 12 inch woofer (NOT subwoofer) for example, as that will start to hit breakup modes at about 1.5khz. As far as I know, there is no such thing as a 12 inch car woofer. Also, what tweeter are you using? Is it a piezo horn or dynamic? If it's piezo, make sure it's a Motorola. If not, bin it. Your ears will thank you. Also, you need to do some careful trickery to prevent Class D harmonics from the amps deafening you without realising. It happens.

Lulz at a 4 inch speaker claiming to hold up to 100w too...if you fed it that much power, you'd get a lot of smoke. Power ratings can be exceeded if you filter off part of the range where the speaker drops off, but that just takes the piss. For example, if you have a 4 inch speaker rated at 50w, you could probably feed it 150w happily if you cut off anything below 150hz and above 3khz. Note that most listening is done at well under 2w of power. Very efficient speakers (think Klipsch La Scala, K-horns, Altec A5's) will literally provide nightclub sound levels with under 10 watts. Power ratings are VERY misunderstood.

The best thing to do if you really, really want to use car speakers is make an open-baffle line array, and couple it with an efficient tweeter for the top end and a pair of stereo subs to supplement the lows. Something like 8 6" speakers in a single baffle, along with a good dynamic horn would be nice. A quick 12" sub should take care of anything below 100hz, and a high-pass filter on the line arrays will allow you to feed 'em a lot more power.

Open-baffle means that there is no cabinet, and the driver is effectively working in free air. Baffle size is calculated to prevent reflections of the backwave at resonant frequency.

As for power...yes, you will need a huge power supply capable of supplying massive peak current. It's not very practical to be honest. Most good home amps will happily drive a 4 ohm load, and sound one hell of a lot better than a mid-priced car amp. If you were to buy a suitable high current 12v power supply, you're looking at the best part of £200-300, and only a bit less to build a good one yourself.

Oh, and one more note - building a custom system yourself will not give you better quality than buying decent used stuff...it's a very good learning curve if you're just starting off in speaker building, but don't expect outstanding quality with such a small budget and if it's your first set of speakers.

I'm not bashing your taste in music here, but the synthesised bassline in drum and bass is very easy to reproduce well with cheap equipment. Building a sub should therefore be pretty straightforward; if you like rock or acoustic stuff, it's a lot harder to integrate a sub well.

Emag: you want to keep excursion down to a minimum to minimise distortion. Car audio seems to have a fascination with big floppy surrounds, large excursions and the shitloads of distortion that comes with it. It is near impossible to make a suspension which has a linear resistance through a 1.5" excursion. Real high-power stuff, like PA subs, use a very large surface area driver and low excursions to maximise accuracy. Think 20mm or so...

.. This would be run from standard 240v home electrics using an inverter to drop it to required voltage and to DC if needed....

HLC: Yes, DC will be needed... doh

You will not need an inverter.
You will need a convertor, which in the high amp range is costly.

A strong car battery (or two) would work for a few (or more) hours, and then you recharge them overnight.


I am also of course going to need something capable of controlling and distributing the input, namely controlling volume, bass, treble and possibly balance. Thinking of using a standard DJ mixer here, again is this possible or is there something possibly better suited to my needs such as a standard crossover which may even possibly be better/cheaper?

HLC: You need a pre-amp (possibly a head unit will do that for you.) ...

crossovers will not provide volume control , bass, treble etc.

Certain mixers might, not sure.
What's the source of your music?
MP3 player?
CD player?
Tape Deck?
Phono?




Edit: Tordec B ... please notice bold type above.

++++

Protecting tweeters is a trifling problem.
If your project is hanging up due to your fear of tweeters being 4 ohm ... ignore that issue.
The amount of current they draw is minimal.
oh wait, I see they're 8 ohm.
Like ST says, that's totally a non-issue.
Even more of a non-issue than I first thought.
A non-issue plus one, I guess.

Just wire in a capacitor that keeps them within their specs and you'll be fine.

a side note about wiring in resistors...
Speaker builders typically use L-Pads not straight resistors, to control output without affecting ohm requirements.

I have ran a 600w amp and sub on my stereo with only a little 12v 3A power supply with no dimming of the lights on the amp indicating underpowering, I never really crank it though.. When I used a computer PSU which apparently had 5A on the 12v line the lights on the amp dimmed on every beat and the PSU eventually broke. I imagine you would need a much more powerful one to run a whole system.

Warning : Do not use car subs with computer. I managed to destroy something like 3 hdd before realizing that it was due to the subs. I have a something like 1+ X 1+ X 3ft sub-box with 2 10" on it and I leave it something like 2+ft beside my my pc. The vibration destroyed the hdd I think.

On low volume, even the kitchen cabinet door would vibrate in resonance.

here's how I did it :

Get a decent 12v power supply with it's own cooling fan if possible, cos it's going to be pretty hot on full blast, or you can use a few psu and link them serially on 12v terminal, the more the better. You need something like 40+ ampere.(4 to 6 PSUs)

I assume you have a decent amp and subs to go with it...other than the subs, mids and twits are not worth having in your living room unless you really want to spend some time making wooden box for them...from my experience, they can sound really nice but the effort to construct few boxes for them is just too much, and a normal 6" or 6X9" won't be loud enough for a 15ft by 30ft living room, unless you use them in your own bedroom.

a normal 6" or 6X9" won't be loud enough for a 15ft by 30ft living room, unless you use them in your own bedroom.
A good line array of 6" car speakers will have efficiency in the mid 90s, and be easily loud enough for a large living room. I built a pair of line arrays using six 6" fullrangers, helped by a Motorola piezo up high. I have measured efficiency to be 94dB/1w/1m at 1khz. And they have been used with a decent sub (not a car sub) outside for PA usage for about 100 people, and they handled it with ease. Fed with about 400wpc of Adcom monobloc goodness.

The 12v line on a computer power supply can only supply 5a or so, as it is not used for much in a computer. You'd need a LOT of power supplies in parallel (not series, as you'd end up with something like 50v at 5a...). It's best to buy a hefty bench power supply.

Car tweeters are, in my experience, shit unless you spend a lot. Buy some decent soft-domes from Parts Express and you'll be happy.

And I'll only say this one more time. Did no fucking one read my big-ass post? CAR SPEAKERS NEED OPEN FUCKING BAFFLES!! No box. Nada. Nothing. Very high Q means a box does very little.

A good line array of 6" car speakers will have efficiency in the mid 90s, and be easily loud enough for a large living room. I built a pair of line arrays using six 6" fullrangers, helped by a Motorola piezo up high. I have measured efficiency to be 94dB/1w/1m at 1khz. And they have been used with a decent sub (not a car sub) outside for PA usage for about 100 people, and they handled it with ease. Fed with about 400wpc of Adcom monobloc goodness.

Stuff made in the 80s or early 90s were thick and heavy I think...I remember seeing one car amp from the 80s and that thing is fully chromed and solid as a brick.

The 12v line on a computer power supply can only supply 5a or so, as it is not used for much in a computer. You'd need a LOT of power supplies in parallel (not series, as you'd end up with something like 50v at 5a...). It's best to buy a hefty bench power supply.

Yeah, made a mistake there, should have been parallel, not serial. But most comp psu these day have something like 15a for 12 volts, link together 6 of them and you get 60a in theory.

And I'll only say this one more time. Did no fucking one read my big-ass post? CAR SPEAKERS NEED OPEN FUCKING BAFFLES!! No box. Nada. Nothing. Very high Q means a box does very little.

No, I disagree. They're just using the car body as baffles. The one in the door is using the door body itself as baffles, and those in the rear are using boot space as baffles. Which is why the sound from the read seemed "loss" when you left the boot open...and on some luxury cars/suvs, the speakers came with it's own plastic casing/baffles screwed to the body in the rear of the speaker ...

No, I disagree. They're just using the car body as baffles. The one in the door is using the door body itself as baffles, and those in the rear are using boot space as baffles. Which is why the sound from the read seemed "loss" when you left the boot open...and on some luxury cars/suvs, the speakers came with it's own plastic casing/baffles screwed to the body in the rear of the speaker ...
Sorry, I think we both have two different meaning of baffle. :D

The baffle is the front part of the speaker - the flat piece of something the driver is fixed to. This isn't the cabinet - just the front part, so hence an open baffle is just a bit of wood (with a calculated size to cancel woofer backwaves) with the driver screwed in it. An enclosure is not a baffle - it's an enclosure. The front part of an enclosure is referred to as the baffle, and its size plays a very big part in frontwave diffraction, comb filtering and imaging.

You may be able to coax some more low-end from a car speaker if it has a lower Q in a ported enclosure, but in my experience, this tends to make the midrange very peaky and nasty.

Edit: If you do opt for open-baffle line arrays, use an active crossover. Behringer's older stuff can be had for cheap on ebay. You need to tune 'em to the room more so than conventional box speakers, so it'll sound a lot better. You might also need bass traps for the corners of the room.

The door body is not sealed, so it provides no real acoustic properties; it is, in effect, acting as an infinite baffle as the backwave is assumed to be 100% absorbed. Of course, this is not the case as it will interact with the arse end of the cone in some ways, but for calculations you can safely assume it's infinite.

When you see a very small enclosure (called a subenclosure) screwed to the back of a speaker, it is there to prevent other drivers in the same plane/enclosure from interacting with its backwave and to act as a high pass filter. All three-way speaker systems have one on the back of the midrange, and I'm assuming it's done in cars for similar reasons; a sub or larger driver takes care of everything from 200hz down, allowing the midrange response to be flatter.

And yeah, 80's car audio is generally awesome. ;) Big power supplies, proper heatsinking and some even work in Class B. Nice stuff. Rainbow's stuff seems pretty decent nowadays - they have a shifting bias control circuit, allowing it to work in Class A for the first few watts, sliding to Class BC after that. Very few car amps can do that...

Sorry, I think we both have two different meaning of baffle. :D
The baffle is the front part of the speaker - the flat piece of something the driver is fixed to. This isn't the cabinet - just the front part, so hence an open baffle is just a bit of wood (with a calculated size to cancel woofer backwaves) with the driver screwed in it. An enclosure is not a baffle - it's an enclosure. The front part of an enclosure is referred
to as the baffle, and its size plays a very big part in frontwave diffraction, comb filtering and imaging.

Well, since you mentioned [no baffles] and [no box] I thought you meant the same thing...I didn't know much about the technical stuff or terms tho...

So to me, it's almost as if they work the same, while a woofer would need a big box as a baffle since it displaces a lot of air, a normal speaker would just need a tiny bowl since they didn't move much. So, naturally I came to the conclusion that they are one and the same. After all, they both were mounted at the back side of the speakers (magnet side) right ?


You may be able to coax some more low-end from a car speaker if it has a lower Q in a ported enclosure, but in my experience, this tends to make the midrange very peaky and nasty.

I've never try it on any speaker box below 10", but from my experiment with subs, porting makes them sound louder and "harder",


The door body is not sealed, so it provides no real acoustic properties; it is, in effect, acting as an infinite baffle as the backwave is assumed to be 100% absorbed. Of course, this is not the case as it will interact with the arse end of the cone in some ways, but for calculations you can safely assume it's infinite.

Not sure about the scientific aspect of this but there's some real difference in sound quality between when it's mounted to the door, and the when it's taken out and sitting on the floor...

Oh, btw, a speaker baffle looked something like this right ?

http://www.autotoys.com/pics/baffleplastic1.jpg

So to me, it's almost as if they work the same, while a woofer would need a big box as a baffle since it displaces a lot of air, a normal speaker would just need a tiny bowl since they didn't move much. So, naturally I came to the conclusion that they are one and the same.


[QUOTE]
After all, they both were mounted at the back side of the speakers (magnet side) right ?
The same sound comes from the back and front of the cone, but for higher frequencies the basket and magnet structure diffracts and reflects the sound wave a lot. Note that subwoofers can be mounted either way round - as in an isobaric design.


Not sure about the scientific aspect of this but there's some real difference in sound quality between when it's mounted to the door, and the when it's taken out and sitting on the floor...
You are quite right. A driver in free air will sound different from a driver in an infinite baffle (the door). As I said, in the door it is assumed that the backwave (sound coming from the basket side of the cone) cannot be heard. When you have a speaker just sat on the floor, the backwave cancels with the frontwave (sound coming from the front of the cone), resulting in a completely different frequency response. Since the backwave is 180 degrees out of phase with the frontwave, combining the two theoretically results in no sound. Due to time-alignment differences, this isn't true, but you do get some cancellation going on.

Not to mention if it's on a hard floor, the backwave is reflected up and interacts with the cone again. :p



I've never try it on any speaker box below 10", but from my experiment with subs, porting makes them sound louder and "harder"
Porting an enclosure typically gives a 3dB efficiency boost at Fs (system resonant frequency) compared to an acoustic suspension (sealed) design. The energy from the backwave of the woofer is used rather than absorbed, hence why it is louder for a given power input. However, you must calculate port size carefully and use the correct driver. A lightly damped driver (low Q) will flop about in a ported box, giving loose, boomy bass and making the bass sound "muddy". Typical drivers suitable for a ported enclosure have a moderate Q. It's not a matter of simply cutting a hole in the box; the mass and resonant frequency of the air in the port must be calculated and matched to that of the driver. A typical trick (HLC, I'm looking at you!) is to tune the port for a few Hz lower than the Fs of the driver, resulting in a little bit more bass from it.



Oh, btw, a speaker baffle looked something like this right ?

http://www.autotoys.com/pics/baffleplastic1.jpg
That's a subenclosure. Not be confused with a subwoofer.

A baffle is this:
http://diyaudioprojects.com/Speakers/Fostex-FX120-Bass-Reflex/Fostex-FX120-Baffle.jpg
The bit of wood the drivers are mounted to.

There appears to be a bit of confusion about infinite baffles
Here's pic of infinite baffle:

http://www.sitewiz.co.uk/v2/sites/linx/images/ceiling_speaker2.jpg

ceilings and walls make the best infinite baffles.
Just be sure to give the drivers some breathing room.
The most hellacious subwoofer set-up I've seen to date had the drivers floor mounted with the rear of the woofers venting into the basement.

You don't need to employ math when you use infinite baffles.
An enclosure , on the other hand, is no longer infinite, and thus, the tricks of math to make them act properly comes into play.
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