Yes, i'd prefer to do the piezo and 12" combination - the three way part on the diagram was to show that the design could be varied to incorporate more speakers.
Could anyone recommend me some good speakers that work together of the piezo, subwoofer combination that are cheap.
Also, is there much use in integrating an amplifier into the unit itself, and if so how would I do this?
Hi,
If you just want something that will make your course work work then looking at the Skyline drive units which seem to be about the cheapest I have seen. I think your best option for a 12inch and tweeter combination would be. (I have never used these so the following is all just theoretical and I can't guarantee the outcome)
The 902.382 12 inch full range driver as its the cheapest 12inch they do at about £17 pounds each. These are claimed to have a response to 18KHz but it will be a beam about a millimeter wide at that frequency - OK a bit of an exageration. Its not the most efficient drive unit but its good for 100W which is what a modist PA amp will do. (it would work OK with no tweeter if you run out of time to make the second box which could be a bonus. Ok is probably a bit of an exageration but you would get full range audio in a very small area)
If you want a really simple solution I would add a 900.298 tweeter to this. (it is incredibly cheap at about 70p, so don't expect it to be the last word in refine ment) This is a short horn and so has an efficiency of 94dB (Most horns are much higher than this) so will match passingly well with the bass driver. This system will be bright as there will be trebble comming off the bass driver and the tweeter. You should put a 47R 3W resistor across the tweeter (in parallel)as this will protect it from any HF comming from the amplifer. It will work without so long as you don't play it too loud.
However I would also recomend putting a 20R -33R resistor in series with the tweeter this will nock its level down a bit to match the bass better. If you still have too much trebble coming from the tweeter you can keep increasing the value of the series resistor as much as you like but more than about 150R and you probably might as well just disconect it. If you find this is the case then you are going to have to deal with the trebble comming off the woofer - see below. (use resistors of at least 1W rating any less and they could burn out 2 or 3W would be better - you should be able to get these at Maplins)
If you want to improve the system further an inductor of arround 330uH (0.33mH) of a suitable current rating (you need at least a couple of amps) will tame what will probably be a very tissy mid to high range. It needs to go in series with the woofer.
A further possible improvement would be to add about 4.7uF capacitor after the inductor to ground (ie in parrallel with the woofer). This will give you a very approximate 2nd order filter at arround 4KHz. Which will control the mid range a bit better. The cap needs to be at least 100V and it needs to be bipolar. Both of these are improtant as it will most likely burst if you use a lower voltage or a polarised device. (a polarised device is one with a + and -ve teminal these usually have a white stripe on the negative side). Don't add the capacitor without the inductor you could damage your amplifier.
Without measurments the best you can hope for is to limit the energy a bit its not going to crossover nicely.
I did a quick simulation with this drive unit and I would recomend a sealed box of arround 40 liters. This will give a mild peak of about 2dB at arround 80Hz which will make the speaker sound like it has lots of bass. Its -3dB point is 55Hz which is more than good enough for a PA speaker (Quite reasonable for a HiFi speaker in a small room). The reason for not porting it or using a larger box is that the max excursion of this drive unit is listed as 1mm which really isn't very much (guess thats why its cheap) and the small box helps to limit the excursion to absolute max of arround 5mm for a full 100W input. The drive unit can probably just about cope with this as there is normally a fairly large non linear region before damage occurs after Xmax. However if you are playing it loud listen out for any taping or cracking noises which could be the drive voice coil hitting the back of the drive unit. If this happens then obviously turn it down. Don't get hung up on making a box that has lots of bass extension - most music is mixed with the bass in the 50 - 100Hz region anyway and its better to not push the excursion of the drive unit that way what you do get will be cleaner. The slight peak will make it sound impressive anyway.
Since this is a mechnical project, I will leave you to work out the panel sizes for a 40 Liter box. Tweeter can be mounted in any size box you like. The little box on a pillar looks kind of interesting and with a bit of large dowling shouldn't be hard to do. You could even make it rotate so you can adjust the direction of the tweeter.
Too all those people reading this, that are just about to jump down my throught about this design. This is NOT intended to be a full design. Its just enough to get this chap moving forward on a speaker that will work and sound acceptable (especially if the full xover is implemented) so he can do his DT project and end up with something that is not completely unbalanced at the end of it. Appolagies for spelling errors - not my strong point.
I don't recoment adding an amplifer it will just add complexity and if this is a course work project you need to be able to complete it in a reasonable time.
Regards,
Andrew
If you just want something that will make your course work work then looking at the Skyline drive units which seem to be about the cheapest I have seen. I think your best option for a 12inch and tweeter combination would be. (I have never used these so the following is all just theoretical and I can't guarantee the outcome)
The 902.382 12 inch full range driver as its the cheapest 12inch they do at about £17 pounds each. These are claimed to have a response to 18KHz but it will be a beam about a millimeter wide at that frequency - OK a bit of an exageration. Its not the most efficient drive unit but its good for 100W which is what a modist PA amp will do. (it would work OK with no tweeter if you run out of time to make the second box which could be a bonus. Ok is probably a bit of an exageration but you would get full range audio in a very small area)
If you want a really simple solution I would add a 900.298 tweeter to this. (it is incredibly cheap at about 70p, so don't expect it to be the last word in refine ment) This is a short horn and so has an efficiency of 94dB (Most horns are much higher than this) so will match passingly well with the bass driver. This system will be bright as there will be trebble comming off the bass driver and the tweeter. You should put a 47R 3W resistor across the tweeter (in parallel)as this will protect it from any HF comming from the amplifer. It will work without so long as you don't play it too loud.
However I would also recomend putting a 20R -33R resistor in series with the tweeter this will nock its level down a bit to match the bass better. If you still have too much trebble coming from the tweeter you can keep increasing the value of the series resistor as much as you like but more than about 150R and you probably might as well just disconect it. If you find this is the case then you are going to have to deal with the trebble comming off the woofer - see below. (use resistors of at least 1W rating any less and they could burn out 2 or 3W would be better - you should be able to get these at Maplins)
If you want to improve the system further an inductor of arround 330uH (0.33mH) of a suitable current rating (you need at least a couple of amps) will tame what will probably be a very tissy mid to high range. It needs to go in series with the woofer.
A further possible improvement would be to add about 4.7uF capacitor after the inductor to ground (ie in parrallel with the woofer). This will give you a very approximate 2nd order filter at arround 4KHz. Which will control the mid range a bit better. The cap needs to be at least 100V and it needs to be bipolar. Both of these are improtant as it will most likely burst if you use a lower voltage or a polarised device. (a polarised device is one with a + and -ve teminal these usually have a white stripe on the negative side). Don't add the capacitor without the inductor you could damage your amplifier.
Without measurments the best you can hope for is to limit the energy a bit its not going to crossover nicely.
I did a quick simulation with this drive unit and I would recomend a sealed box of arround 40 liters. This will give a mild peak of about 2dB at arround 80Hz which will make the speaker sound like it has lots of bass. Its -3dB point is 55Hz which is more than good enough for a PA speaker (Quite reasonable for a HiFi speaker in a small room). The reason for not porting it or using a larger box is that the max excursion of this drive unit is listed as 1mm which really isn't very much (guess thats why its cheap) and the small box helps to limit the excursion to absolute max of arround 5mm for a full 100W input. The drive unit can probably just about cope with this as there is normally a fairly large non linear region before damage occurs after Xmax. However if you are playing it loud listen out for any taping or cracking noises which could be the drive voice coil hitting the back of the drive unit. If this happens then obviously turn it down. Don't get hung up on making a box that has lots of bass extension - most music is mixed with the bass in the 50 - 100Hz region anyway and its better to not push the excursion of the drive unit that way what you do get will be cleaner. The slight peak will make it sound impressive anyway.
Since this is a mechnical project, I will leave you to work out the panel sizes for a 40 Liter box. Tweeter can be mounted in any size box you like. The little box on a pillar looks kind of interesting and with a bit of large dowling shouldn't be hard to do. You could even make it rotate so you can adjust the direction of the tweeter.
Too all those people reading this, that are just about to jump down my throught about this design. This is NOT intended to be a full design. Its just enough to get this chap moving forward on a speaker that will work and sound acceptable (especially if the full xover is implemented) so he can do his DT project and end up with something that is not completely unbalanced at the end of it. Appolagies for spelling errors - not my strong point.
I don't recoment adding an amplifer it will just add complexity and if this is a course work project you need to be able to complete it in a reasonable time.
Regards,
Andrew
Hi,
FWIW I'd :
Buy these :
http://www.richersounds.com/showproduct.php?cda=showproduct&pid=BUSH-SPK2025
And use the drivers crossover etc for your mid and treble.
Assuming the above has no baffle step compensation (reasonable)
add a 12" unit into the mix. Skytronic units are the cheapest :
http://www.skytronic.co.uk/about/storefinder.php
The 902.382 dual cone has very low excursion.
http://www.wle-shop.co.uk/modules/shop/view.asp?catid=79&Prodcode=902.176
or
http://www.wle-shop.co.uk/modules/shop/view.asp?catid=79&Prodcode=902.222
I'd go for the last one. All 3 suit a well stuffed sealed box around 50L.
(according to the specs - but my money is the last one is most likely)
Now the technical bit :
You need a crossover between the bass unit and the midrange.
The only non-technical way to do this I'd say is to convert a
12dB/octave subwoofer crossover into a a 6dB/octave c/o
for the bass and midrange.
http://www.wle-shop.co.uk/modules/shop/view.asp?catid=79&Prodcode=900.582
You can experiment with capacitor values - they are cheap, and
unwind the inductor if needed, but generally put the inductor in
series with the bass unit and the capacitor the mid unit.
(A 1st order series may work better - but more technical.)
A complete lash-up - but years of experience go into suggesting it.
😉/sreten.
FWIW I'd :
Buy these :
http://www.richersounds.com/showproduct.php?cda=showproduct&pid=BUSH-SPK2025
An externally hosted image should be here but it was not working when we last tested it.
And use the drivers crossover etc for your mid and treble.
Assuming the above has no baffle step compensation (reasonable)
add a 12" unit into the mix. Skytronic units are the cheapest :
http://www.skytronic.co.uk/about/storefinder.php
The 902.382 dual cone has very low excursion.
An externally hosted image should be here but it was not working when we last tested it.
http://www.wle-shop.co.uk/modules/shop/view.asp?catid=79&Prodcode=902.176
An externally hosted image should be here but it was not working when we last tested it.
or
http://www.wle-shop.co.uk/modules/shop/view.asp?catid=79&Prodcode=902.222
An externally hosted image should be here but it was not working when we last tested it.
I'd go for the last one. All 3 suit a well stuffed sealed box around 50L.
(according to the specs - but my money is the last one is most likely)
Now the technical bit :
You need a crossover between the bass unit and the midrange.
The only non-technical way to do this I'd say is to convert a
12dB/octave subwoofer crossover into a a 6dB/octave c/o
for the bass and midrange.
http://www.wle-shop.co.uk/modules/shop/view.asp?catid=79&Prodcode=900.582
An externally hosted image should be here but it was not working when we last tested it.
You can experiment with capacitor values - they are cheap, and
unwind the inductor if needed, but generally put the inductor in
series with the bass unit and the capacitor the mid unit.
(A 1st order series may work better - but more technical.)
A complete lash-up - but years of experience go into suggesting it.
😉/sreten.
Thanky you very much gfiandy for the post
"especially if the full xover is implemented"
When you say this, are you implying that the extra components are in effect a crossover?
On the skytronic website, it doesn't appear that one is able to order online - do you know of anywhere that stocks a large amount of skytronic components or do I need to visit a shop?
40 litres works out to side dimensions of 342mm without taking into consideration internal bracing structures.
"especially if the full xover is implemented"
When you say this, are you implying that the extra components are in effect a crossover?
On the skytronic website, it doesn't appear that one is able to order online - do you know of anywhere that stocks a large amount of skytronic components or do I need to visit a shop?
40 litres works out to side dimensions of 342mm without taking into consideration internal bracing structures.
Hi,
The Skytronic parts can be found at the link given by one of the earlier posters for West London Electric who will deliver.
www.wle-shop.co.uk
Yes if the extra components mentioned are fitted you will get a very approximate crossover. You can then fiddle with this trying larger or smaller caps, resistors and inductors arround the same value to see if the sound gets better or worse or just live with what it gives you.
You will need internal bracing but I guess you had worked that out from your earlier post. You should also line the box with some foam to reduce mid range being reflected back into the driver this will improve the sound. You could also use some wadding (sort of fake wool) this absorbs high frequency sound in the box again to prevent it being reflected into the driver. It also has the effect of reducing the speed of sound in the box as it travels slower through the wadding than air. This slightly increases the effective volume of the box. Don't jam pack it is will make the bass sound worse.
Another technique is to attach some kind of damping material to the box walls to reduce vibration. Black Tar pads are often used (I can't use the right word as the profanity checker is picking up the start of it as a swearwoord!)(you can get them from car audio shops for damping car doors) or you could investigate other materials such as a different wood or metals as often disimilar materials reduce resonance in the box. Attach them with a compliant material such as mastic so you have a tri layer laminate with the mastic working as a lossy layer between two materials with different resonant characteristics.
Also when building it use a mind technique that an old KEF speaker designer told me he used with cabinet makers. He would tell them to make it water tight as it is much easier to visualise water escaping rather than air.
Just looked at sreten's post - he is right the 902.222 will probably give you a better speaker, its also cheaper 🙂. I didn't check all of skytronics drivers. It will still work with a slight bass boost in a 40L Box or if you want an almost flat bass response that plays a bit deeper then a 50L box will be OK as it has much more linear excursion 6mm vrs 1mm. You could even port with this one but I wouldn't bother as you would need a much larger box approx 260L with a 10cm diameter 9cm long port , which would be a real pain to make.
The 902.222 will not work as a full range so you need the tweeter with this one and you might even find it is a bit laid back in the mid range as it might be rolling off by 4KHz even on axis. Still this will probably make the speaker sound more HiFi and less PA. The same advice applies for a crossover and it will probably make it sound better but you have got more chance of not needing anything on the bass driver and just using the resistors to adjust the level of the tweeter.
Again this is not going to give you a perfectly balanced speaker but you will get something that isn't obviously broken and with the 902.222 you will be able to play it much louder even though the drive unit is about 0.5dB less sensitive, the extra excursion available will allow you to use a much more power without bass problems.
Regards,
Andrew
The Skytronic parts can be found at the link given by one of the earlier posters for West London Electric who will deliver.
www.wle-shop.co.uk
Yes if the extra components mentioned are fitted you will get a very approximate crossover. You can then fiddle with this trying larger or smaller caps, resistors and inductors arround the same value to see if the sound gets better or worse or just live with what it gives you.
You will need internal bracing but I guess you had worked that out from your earlier post. You should also line the box with some foam to reduce mid range being reflected back into the driver this will improve the sound. You could also use some wadding (sort of fake wool) this absorbs high frequency sound in the box again to prevent it being reflected into the driver. It also has the effect of reducing the speed of sound in the box as it travels slower through the wadding than air. This slightly increases the effective volume of the box. Don't jam pack it is will make the bass sound worse.
Another technique is to attach some kind of damping material to the box walls to reduce vibration. Black Tar pads are often used (I can't use the right word as the profanity checker is picking up the start of it as a swearwoord!)(you can get them from car audio shops for damping car doors) or you could investigate other materials such as a different wood or metals as often disimilar materials reduce resonance in the box. Attach them with a compliant material such as mastic so you have a tri layer laminate with the mastic working as a lossy layer between two materials with different resonant characteristics.
Also when building it use a mind technique that an old KEF speaker designer told me he used with cabinet makers. He would tell them to make it water tight as it is much easier to visualise water escaping rather than air.
Just looked at sreten's post - he is right the 902.222 will probably give you a better speaker, its also cheaper 🙂. I didn't check all of skytronics drivers. It will still work with a slight bass boost in a 40L Box or if you want an almost flat bass response that plays a bit deeper then a 50L box will be OK as it has much more linear excursion 6mm vrs 1mm. You could even port with this one but I wouldn't bother as you would need a much larger box approx 260L with a 10cm diameter 9cm long port , which would be a real pain to make.
The 902.222 will not work as a full range so you need the tweeter with this one and you might even find it is a bit laid back in the mid range as it might be rolling off by 4KHz even on axis. Still this will probably make the speaker sound more HiFi and less PA. The same advice applies for a crossover and it will probably make it sound better but you have got more chance of not needing anything on the bass driver and just using the resistors to adjust the level of the tweeter.
Again this is not going to give you a perfectly balanced speaker but you will get something that isn't obviously broken and with the 902.222 you will be able to play it much louder even though the drive unit is about 0.5dB less sensitive, the extra excursion available will allow you to use a much more power without bass problems.
Regards,
Andrew
Just one more thing, I wouldn't make the cabinet a perfect cube as it will have a massive resonance at the frequency corresponding to the wall dimensions. Besides I think you will need to make one of the faces larger than the other to get the 12inch driver in. 342/25.4 is about 13.5 inches which doesn't leave you much room for the speakers mounting.
Regards,
Andrew
Regards,
Andrew
http://www.skytronic.co.uk/about/storefinder.php
Use the WLE link to make sure your not being ripped off by the local DJ shop.
The 2 way and 3 way routes are very different and of course will
give very different results. Aesthetically the 3 way emphasises
the modular approach. The relative merits of the resultant sound
quality I''ll leave others to debate, but I will note for the 3 way
the mid/treble should be useable on its own.
However .... I dread to think what is actually inside that 70p lump of plastic ....
🙂/sreten.
Use the WLE link to make sure your not being ripped off by the local DJ shop.
The 2 way and 3 way routes are very different and of course will
give very different results. Aesthetically the 3 way emphasises
the modular approach. The relative merits of the resultant sound
quality I''ll leave others to debate, but I will note for the 3 way
the mid/treble should be useable on its own.
However .... I dread to think what is actually inside that 70p lump of plastic ....
🙂/sreten.
In your longer earlier post gfi, you mentioned adding resistors in series with the tweeter and the woofer.
You told me to place one in series with the tweeter and one in series with the woofer - Surely if its all one circuit, both resistors are technically in series with both speakers?
You told me to place one in series with the tweeter and one in series with the woofer - Surely if its all one circuit, both resistors are technically in series with both speakers?
I have modelled what I think you mean - can you tell me if this is correct:
An externally hosted image should be here but it was not working when we last tested it.
ok, thank you very much for the correction and all your help.
Just one final question - Will ordinary cheap resistors work fine for the job?
Just one final question - Will ordinary cheap resistors work fine for the job?
Depends on what you mean by ordinary resistors. If you mean the small wire ended types that are used in alot of equipment then unfortunately not. They will not be able to cope with the power disipation.
You need resistors rated at at least 2Watts - 3Watts would be preferable if you are going to play it very loud for long preriods of time.
This is the type you want at Maplins (They don't do a 25R but 22R or a 27R will be fine 22 - bit more trebble 27 bit less treble)
http://www.maplin.co.uk/module.aspx?ITAG=SPEC&ModuleNo=2173&doy=24m12#spec
Regards,
Andrew
You need resistors rated at at least 2Watts - 3Watts would be preferable if you are going to play it very loud for long preriods of time.
This is the type you want at Maplins (They don't do a 25R but 22R or a 27R will be fine 22 - bit more trebble 27 bit less treble)
http://www.maplin.co.uk/module.aspx?ITAG=SPEC&ModuleNo=2173&doy=24m12#spec
Regards,
Andrew
Also, i'm guessing that the capacitor and inductor need to be audiograde.
How would you recommend me placing the components in my speaker case - just loosely or mounted onto some wooden board/circuit board?
Also, is lead-tin solder ok to use?
How would you recommend me placing the components in my speaker case - just loosely or mounted onto some wooden board/circuit board?
Also, is lead-tin solder ok to use?
For the woofer enclosure, I hear many people refer to internal bracing which I think is known as a baffle? Is there a particular design which I should use that poses particular advantages over others - would a simple wooden beam nailed/screwed to the center of two opposite faces be sufficient?
The most inportant aspect of the capacitor is that it is high enough voltage - 100V for up to 100W and that it MUST be bipolar as it will be damaged and may even explode if you put a polarised capacitor in. Maplins range of non polar caps is below - they don't have a 4.7 but you could use a 3.3 and a 2.2 in parrallel which would be close enough and alow you some options if you want to try altering the crossover. i.e you could use just the 3.3 if you want more energy in the crossover region or even just the 2.2 if you want alot more energy in the crossover region.
http://www.maplin.co.uk/module.aspx?ModuleNo=12777&doy=27m12
For a design like this I wouldn't worry to much about it being an audio grade component it is unlikely to be the limiting factor in the sound quality.
The Cabinet can be braced by a peice of wood as you describe. However it would be better if it wasn't exactly in the center of the two panels as this will tend to creat a resonance a twice the frequency in the two smaller areas created by the bracing. If you offset it then the two areas will resonante a different frequencies as they will be different sizes so they will not tend to reinforce each other and the overall readiation from the cabinet will be less noticeable.
Regards,
Andrew
http://www.maplin.co.uk/module.aspx?ModuleNo=12777&doy=27m12
For a design like this I wouldn't worry to much about it being an audio grade component it is unlikely to be the limiting factor in the sound quality.
The Cabinet can be braced by a peice of wood as you describe. However it would be better if it wasn't exactly in the center of the two panels as this will tend to creat a resonance a twice the frequency in the two smaller areas created by the bracing. If you offset it then the two areas will resonante a different frequencies as they will be different sizes so they will not tend to reinforce each other and the overall readiation from the cabinet will be less noticeable.
Regards,
Andrew
With a crossover that is as simple as this one you could just solder the parts accross the speaker terminals or the binding posts where they come into the cabinet.
But if you want to mount them more securely a small peice of wood can be used then the parts hot melt glued to the bord and then wired together. This usually works quite well but I wouldn't do that untill you are happy with the sound from the crossover.
Lead tin solder will work fine, just don't eat it 🙂
Regards,
Andrew
But if you want to mount them more securely a small peice of wood can be used then the parts hot melt glued to the bord and then wired together. This usually works quite well but I wouldn't do that untill you are happy with the sound from the crossover.
Lead tin solder will work fine, just don't eat it 🙂
Regards,
Andrew
buy 63/37 tin/lead solder.
don't buy 60/40 solder.
savbit has a little copper in it to protect the copper tip of your iron, but most are plated and don't need the extra protection.
don't buy lead free.
Rapid are a good/cheap/reliable UK supplier.
orders over £25 are post free.
don't buy 60/40 solder.
savbit has a little copper in it to protect the copper tip of your iron, but most are plated and don't need the extra protection.
don't buy lead free.
Rapid are a good/cheap/reliable UK supplier.
orders over £25 are post free.
Would wire heat be a problem - do the wires need to be quite thick or of a special grade in order to prevent them from overheating/melting?
The 12" woofer is clearly quite a beast - what kind of stress will it place on its housing - I don't want to build the housing for it to explode with the air pressure. What kind of construction technique do I want in order for the pressure to be withstood?
The 12" woofer is clearly quite a beast - what kind of stress will it place on its housing - I don't want to build the housing for it to explode with the air pressure. What kind of construction technique do I want in order for the pressure to be withstood?
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