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Multi-Way Conventional loudspeakers with crossovers

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Old 8th September 2007, 03:01 PM   #1
morfius is offline morfius  United Kingdom
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Default Technology Student Building Speaker

Hi everyone, I have just joined due to the fact that I am planning on constructing a speaker system for my Technology project and there seem to be few places on the internet with the right answers.

I have a few questions which I would like to ask:

1. I would like to produce a single unit that has a subwoofer at the bottom, a mid range above, and a tweeter at the top. Is this a common configuration that would work with good sound quality?

2. When I select the speakers to use, would it be recommended to get all three from the same make? or does it not matter if the tweeter/subwoofer/mid range are all different makes?

3. What are the best ways for making the system as loud as possible?

4. How loud is it safe to turn up a system without damage?

5. Would my system need an integrated amp in order to work off an ipod?

6. Is there any free software that can be used to design a circuit, and are there any circuit plans available online?

7. How thick does the wood panelling need to be for the enclosure, and do I need to fill the enclosure with foam and other materials for dampening purposes?

8. We are not allowed to run the speaker off full mains voltage, and can only use a maximum of 12V transformer plugged into the mains. Is this enough power for a decent system? what does a typical system require in terms of voltage?

9. What type of jack is best, a small "headphone sized" one or the larger sized type.

10. Would the enclosure need a fan to cool it? or is overheating not an issue?

11. What are the best companies for cheap components? Bear in mind that I live in England, and don't really want to go too far over 60 or 70 ($120-$140). Is this a realistic budget? or is it too ambitious?

12. How long would something like this take to build?

Thank you for any replies, they are all very much appreciated and will help me loads.
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Old 8th September 2007, 03:45 PM   #2
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You might be better off with this in the main speaker part of the forum, as this one is more about full-range drivers. However, FWIW,

1) That's basically the classic 3 way, & it must've been used in a million speaker designs over the past 50 years or so. So yes, it's a very common configuration. As to whether it provides good sound quality, that depends on the quality of the drivers, XO, and cabinet design.

2) It's probably easier to source the drive units from the same company as they'll tyically have a company 'sound' & be voiced in a similar way. But just as important is how you select them Partnering a horn-loaded tweeter which is 110db efficient for 1w input at 1m with a big quacking plastic woofer that's about 82db efficient for the same power doth not a good idea make as you're going to have a big headache with the XO, balancing the levels out. A crossover should be as simple as necessary to provide good sound quality (but never simpler). That's just the start of course -there are many other factors involved.

3) Lots of efficient drivers, with a large cone area = loud. Remember that the ability to go loud does not mean it's going to sound good though.

4) Impossible to answer. Depends on the speaker and amplifier. Generally speaking, it's safer to over than under-drive speakers. Say you have speakers rated at 30w. You can run that cheerfully with a 1Kw amplifer, no worries, unless you do something very stupid, like crank the volume up to max and put Massive Attack on. You'd be more likely to damage the speaker by trying to power it with a 2w spud-amp that's having to run flat out, and clipping badly all the time.

5) Well, you could run it direct into power amps, but altering volume wouldn't be as convenient.

6) Lots. Do a search for free XO design software / speadsheets & use whatever you feel happiest with. There are thousands of XO designs on the internet, but they're worthless to you unless you happen to be using the exact same drivers. The exception is an active crossover, which you could buy & adjust the levels to whatever is required (so you still need to design an XO -the points, & levels of boost / attenuation, how many db per octave you bring drivers in or out etc.)

7) Depends on the cabinet design re the thickness, but bank on at least 3/4in, with lots of internal bracing. Damping material -what to use, how much, and where it needs to be again is completely dependant on what sort of cabinet you come up with. Some need lots, some very little.

8) That's nothing to do with the speakers per se -trust me, you don't want to know what would happen if you tried plugging 230v 13amp AC British mains directly into a drive unit. It's the amp that's plugged into the mains, not your speakers.

9) Not sure what the context is, but I always prefer larger jack-plugs. Those 3.5mm ones are far too weak for my liking. Are you wondering how to get the output from the iPod to the amp? Best is to either buy an adaptor lead that takes a female 3.5mm socket to two male phono plugs which then plug into the output of 99.9% of amplifiers.

10) Not unless they have amplifiers built into them, in which case heat-sinks are a better bet.

11) I have a feeling you're going to struggle mightily for that kind of money. Maplins, or your local independant electrical store are probably the best sources in the UK. Have a look at CPC too.

12) Another one of those 'depends on what your design is' questions I'm afraid. Anything from a Saturday afternoon to a couple of months depending on how complicated it is.

OK -question. What is it you need to do for your project, specifically? Obviously, build speakers, but what's the criteria? What do they have to do? Any specific goal in mind? Anything you're not allowed to do?

If I were in your shoes, and if it fitted what I were allowed to do, I'd be looking at buying a couple of decent quality full-range drivers (something like Monacor units) and putting them into an interesting cabinet. Nope, they're not going to blow a nightclub PA system out the window, but, and it's a big but, if this is your first project, you've made life a heck of a lot easier for yourself at a stroke because you've eliminated the biggest headache in speaker design: matching drive-units, and designing a crossover. It can be made to look as good as a multiway, and it's going to sound a heck of a lot better than anything you're likely to be able to build using lots of drive-units for that price (or any price, as you haven't designed or built a speaker before). It's not cheating, you have to spend a lot more thought over the cabinet, but that's OK -we can help, and it doesn't mean the box is automatically going to be complicated. Chances are you'll get Brownie points for a) thinking out of the box, & doing something different, b) good sound, and c) the effort you put in. Or you should. I was a teacher for a while, until I decided to go back to university and finish my PhD, and that's the sort of thing teachers should always be looking for.

Best wishes
Scott
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Old 8th September 2007, 03:57 PM   #3
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morfius,

Based on your first question, I would recommend posting in the Loudspeakers area rather than the Full Range area. Full range refers to using a single, full range driver in the speaker, rather than a 2 or 3 drivers per speaker.

If you don't want to spend a great deal of time studying speaker design theory, then you may want to look into either kits or DIY designs that are already optimized.

You will need an amp for your iPod to drive your speakers.

Based on your budget, I suggest you look into making a pair of modest single driver speakers and use a Sonic Impact T-amp. For theory of single driver speakers, check out Martin King's quarter-wave.com site. For designs, look over the many styles discussed in this forum.

You need to read, read, read, then read some more!

Cheers, Jim
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Old 8th September 2007, 04:47 PM   #4
morfius is offline morfius  United Kingdom
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Thank you very much for this reply, I really appreciate the time you spent.

I will try and get this topic moved soon.

So from what I have read, I will not bother with integrating an amp, as that is not required. I still want to try and stick with the tweeter, mid, sub, design, as Maplin seems to supply reasonably priced ones.

So, from what I have read, my speaker will not need a separate power feed, but instead, will get the power through the amp?

In terms of the budget, I could go up to 100+ if it were really necessary.

So from what I understand, my circuit will incorporate:

Tweeter
Subwoofer
Mid Range Speaker
Jack Input

Apart from the above, what other electrical components will be needed, and is there a particular circuit layout that you would recommend?

When you say crossover, is this a component that manages the sound balance between all three speakers?

I'm wouldn't really call myself much of an audiophile, so i'm sorry if I don't understand some of the more techincal words.

The design part of the speaker will gain me more marks than circuitry, due to marks awarded on originality etc. So I don't want to go too complicated on the electronics.

In terms of the actual materials for the speaker housing, what could I be expecting to spend on these?

Jim, thanks for the reply, I am still keen on the original idea, however, if it is not viable, then I will have a further look into your suggestion.

Thanks for the idea about the amp.
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Old 8th September 2007, 04:54 PM   #5
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Old 8th September 2007, 05:12 PM   #6
morfius is offline morfius  United Kingdom
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Thank you.

Update: I am willing to increase my budget to 100-150 ($200-300)

http://www.maplin.co.uk/Search.aspx?...rldid=&doy=8m9

There are some mid and bass speakers on the above link. Would any of you consider these ones good value, and are the brands any good?

Another question: How do you all make perfect round holes for the larger speakers? (It's not like there are any 15 inch drill attachments on the market today!)
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Old 8th September 2007, 05:12 PM   #7
morfius is offline morfius  United Kingdom
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NB: The brand for all of the speakers is "Eminence"
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Old 8th September 2007, 05:12 PM   #8
morfius is offline morfius  United Kingdom
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Sorry for the triple posting:

Do the subwoofer, mid range and tweeter have to be the same wattage as each other in order to work well together.

If I had a 500 watt subwoofer, 300 watt mid range and 250 watt tweeter, for example, would I need to have a 500+300+250=1050 watt crossover, or does the crossover only need to be as powerful as the most powerful speaker?

Also, with amplifiers, does the amplifier need to be rated for the wattage of all speakers added together or the wattage of the most powerful speaker?
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Old 8th September 2007, 06:30 PM   #9
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Before you go any further, I'd suggest it would be a good idea if you read up a little on the subject, and got a good grasp of the basics. You are attempting something that is extremely difficult to achieve, period, never mind as a first project. Don't attempt anything, and for your own sake, don't buy anything, until you have got hold of a copy of The Loudspeaker Design Cookbook, read it, and understood it. That is a good basic guide to most aspects of speaker design, and it's stuff that you need to know as you're so far off the mark currently it's worrying.

OK, the basics. Speakers aren't powered from the mains, but an amplifier (cheap computer speakers et al have amps built into them). Most do not have jack-plugs. That's an iPod / walkman etc thing. They have binding posts to take speaker cable from the amplifier to the speaker.

Yes, a crossover (XO) is the electrical circuit that divides the signal from the amplifier and sends it to the appropriate driver (bass to the woofer, mids to the midrange etc). They are the hardest thing to design in a speaker IMHO. They are not measured in wattage. They're not measured in anything particularly, but the components in them have to be able to handle the current & power you're planning on pumping through them. You don't get 1050 watt XO for example. A fourth order Linkwitz-Reily, yes. (XOs are of different types, first, seconed, third, fourth order etc).

Speakers do not have to be of the same rated wattage (by the way, wattage is fairly irrelevant -sensitivity is a better measure) to work together -with more components in the XO you can do things about that, but it gets very complicated. Worse, just because speakers are of the same rated wattage or same sensitivity, that doesn't mean they'll work well together either. Eminence are a good brand BTW.

Most people cut holes with a router with a circular jig attachment I suspect.

If you want me to be honest (I'd rather that now than you waste a load of time & money) I'd advise you to abandon your original plan. If you're going to get more marks for design than circuitry, again, I'd advise you to go with a single full-range driver per cabinet, and put your effort into designing an interesting enclosure.
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Old 8th September 2007, 06:52 PM   #10
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Hi morfius,

I must say I agree wholeheartedly with Scottmoose. He is a man with a lot of knowledge and wisdom concerning this and is being very generous with his time.

If there is no need for a multi unit speaker, then consider a fullrange system. They have their own rewards hard to achieve with a two or three way. They are also very adaptable. ie: if you find the high end lacking a bit, you can add a supertweeter with a simple capacitor for the crossover. If the bass is what needs a boost, you can add a powered woofer later. It comes with it's own crossover. As mentioned, crossovers can be quite a hassle to get right and it really helps if you've done it before, or have somone there who has.

This is a foolproof method of ensuring a quality system without spending a boatload of cash right off the bat.

If it needs to be a multi unit, then get Vance Dickason's book (mentioned earlier) and start reading. Investing the time in reading will be well spent.
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