Need help designing Sub - Need to go down to 17Hz for 'Earthquake' Project

[s162216]

How could I make a volume control for that? This may sound really stupid, but most amplifier circuits I have seen tend to put a 10K log pot in parallel (I think, it may be series) with the input and that acts as the volume control.

I could get an ABS box, mount the amp inside on some PCB pillars so it does not heat the plastic and overheat and then cut a hole in the side of it to let the heatsink poke out and put some mesh or something over it to stop stuff getting in and then bolt/screw it on top of the sub with some little pillars so it is easy to remove if needed.

Why do I need a phasing circuit for this, most amplifier designs I have seen make no mention of one?


By the way that active SCART to S-Video adaptor is going to get built when I have some time in my 6 week school summer holiday in a month, shouldn't cost more than £20.

 

[TLS Guy]

How could I make a volume control for that? This may sound really stupid, but most amplifier circuits I have seen tend to put a 10K log pot in parallel (I think, it may be series) with the input and that acts as the volume control.

I could get an ABS box, mount the amp inside on some PCB pillars so it does not heat the plastic and overheat and then cut a hole in the side of it to let the heatsink poke out and put some mesh or something over it to stop stuff getting in and then bolt/screw it on top of the sub with some little pillars so it is easy to remove if needed.

Why do I need a phasing circuit for this, most amplifier designs I have seen make no mention of one?


By the way that active SCART to S-Video adaptor is going to get built when I have some time in my 6 week school summer holiday in a month, shouldn't cost more than £20.

First of all the case must be correct and substantial. There is 240 volts inside and you have to do it right and safe. If you are using mains power you can't cobble it.

You will need to use a box like this. You will need the 3U.

I would find a welding shop and have them cut out a rectangular hole on the back panel, with a plasma cutter, which the amp will go though, and the top and bottom lips of the heat sink can bolt to the chassis. Use heat sink compound between the lips and the case.

The case needs grounding. You need a stress relieving grommet where the mains lead goes through the case. Drill a whole for the pot n the front.

If you do that you will be safe. That heat sink has to have good thermal contact to the chassis.

Now the volume control. This is a variable L-pad.

The output from the LFE goes across the outer connections (fixed). Make the lower one ground. The input to the amp goes across the sweeper (center) and ground (variable).

Now a lot subwoofer amps have a 180 degree variable phase shift circuit. while not essential it is a very good idea. The reason is that good phasing with your mains at crossover is a good idea. Subs are at different places in the room, the crossover has 180 degree phase shift, and at sub frequencies there are lot of phase shifts and time delays related to the port tuning. So it is really handy to have a circuit that can be varied to get maximum output at crossover. If you don't have one you can only vary phase 180 degrees by reversing the speaker leads, and use the connection that gives the best output.

You can make a phase shifter from an op amp and a variable resistor. (you use a pot, but just use ground and the sweeper connection.)

phase shift at:

FREQ = 1/(2*PI*R3*C)


At low frequencies it has 0 degrees of phase shift and at high frequencies it has 180 degrees of phase shift. By making R3 a pot, you can vary the phase at a given frequency from nearly 0 to nearly 180 degrees.

R1=R2 |---\/\/\/\/\\/\--|
| R2 |
| |
R1 | |\ |
| INV | \ |
INPUT --------\/\/\/\/\/\/----------| \ |
| | \ |
| | \-------- OUTPUT
| R3 | /
| NON-INV | /
|---\/\/\/\/\/\/----------| /
| | /
| |/
|
|
------- C
-------
|
|
|
|

I bet you won't build all this for the cost of buying the Dayton plate amp, and a transformer, even if you dispense with the phase control circuit.. The Dayton has he volume control, but only a phase reversal switch. The unit that Wilmslow have has a a variable phase control

 

[s162216]

I do have some experience working with mains voltages as I did a bit of it in my electronic products GCSE and my dad also has a lot of experience working with the mains. One thing I hate though are grommets as they are so difficult to insert so I usually use a cable gland.

At school we have several pieces of welding equipment and I am on good terms with my old electronics teacher, should be able to cut a suitable hole in one of them cases or similar. Could also do it using CNC drilling machine.

These extruded cases with removable end panels are slightly cheaper and won't require cutting, are they any good?

http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/Cases/Metal-Cases/Extruded-aluminium-enclosures-with-metal-end-panels/74372

 

[TLS Guy]

I do have some experience working with mains voltages as I did a bit of it in my electronic products GCSE and my dad also has a lot of experience working with the mains. One thing I hate though are grommets as they are so difficult to insert so I usually use a cable gland.

At school we have several pieces of welding equipment and I am on good terms with my old electronics teacher, should be able to cut a suitable hole in one of them cases or similar. Could also do it using CNC drilling machine.

These extruded cases with removable end panels are slightly cheaper and won't require cutting, are they any good?

http://www.rapidonline.com/Tools-Fasteners-Production-Equipment/Cases/Metal-Cases/Extruded-aluminium-enclosures-with-metal-end-panels/74372

I'm worried those cases are not substantial enough for a power amp. The hear sinks of power amps are predicted on being bolted to a reasonably substantial piece of metal. The cooler it runs the better. Those cases look fine for low current processing circuits, but not a power amp.

The gland will be fine. The trick to using grommets is getting the whole size just right and using a special bit for drilling in metal cases without snarling the edges.

The best solution would be to cut a whole for an IEC socket. The would look and be the best, but cost a little more.

 

[s162216]

Could an alternative be fan cooling? I could then put it in a suitable plastic case with ventillation slots and with a folded piece of thick sheet aluminium attached to the heatsink, and put a small 60/70mm fan with a 12v regulator across the DC of the amp. The only problem is finding a case big enough.

http://www.rapidonline.com/productinfo.aspx?tier1=Tools%2c+Fasteners+%26+Production+Equipment&tier2=Cases&tier3=ABS+Boxes&tier4=ABS+Boxes&moduleno=81325#techspec

Thats the only affordable case I have found so far that it will fit in apart from the rack cases

Those rack cases are just too expensive to justify the extra cost.

That amp in America and the step down transformer, I think that the postage for the amp will end up being just as expensive as the case to be honest as I have brought some stuff from the US before and the postage is very expensive - that weighs quite a bit as well.

Just one thought - could I make a case similar to a 3U case out of 1.2mm aluminium sheet? We have an aluminium folder at schoola and plenty of sheet, I am sure I could make a suitable case that I could pop rivit together and add a small fan if needed.

 

[TLS Guy]

Could an alternative be fan cooling? I could then put it in a suitable plastic case with ventillation slots and with a folded piece of thick sheet aluminium attached to the heatsink, and put a small 60/70mm fan with a 12v regulator across the DC of the amp. The only problem is finding a case big enough.

http://www.rapidonline.com/productinfo.aspx?tier1=Tools%2c+Fasteners+%26+Production+Equipment&tier2=Cases&tier3=ABS+Boxes&tier4=ABS+Boxes&moduleno=81325#techspec

Thats the only affordable case I have found so far that it will fit in apart from the rack cases

Those rack cases are just too expensive to justify the extra cost.

That amp in America and the step down transformer, I think that the postage for the amp will end up being just as expensive as the case to be honest as I have brought some stuff from the US before and the postage is very expensive - that weighs quite a bit as well.

Just one thought - could I make a case similar to a 3U case out of 1.2mm aluminium sheet? We have an aluminium folder at schoola and plenty of sheet, I am sure I could make a suitable case that I could pop rivit together and add a small fan if needed.

I would not use a plastic case. Plastic will provide no shielding, and invite hum.

If you want to build a case, that should be fine. I would make the panel the amp mounts to 4 mm at least, and over size it so there is at least a 30 mm margin round the heat sink. The rest of the case can be thinner gauge. I do not think you will need a fan then. I would avoid a fan, on grounds of noise.

 

[s162216]

Found this- about £10 cheaper than the 3U mount rack case and perfct size .
Also has two spaces for a cable gland to mount and I could cut some slots in it with a jigsaw for ventillation.

http://www.fwb.co.uk/mall/productpage.cfm/FWBGroup/EAQ702

Heres a link to a data sheet http://www.tempapano.com/katalog/e11-SSETS.PDF

The walls are a bit thin but I could bolt a piece of aluminium sheet onto the wall the heatsink touches and put some thermal compund behind it to ensure good contact.

Bit over my £200 budget now:

• Driver (including P&P £99.00
• Amp (including P&P) £85
• Wood ~ £30 - £40
• Enclosure (including P7P) £30

So about £250, think thats all worth it, I originally only planned to spend about £150?

By the way, whats the link for that plate amp wimslow audio sell? I have not been able to find it.

 

[TLS Guy]

Found this- about £10 cheaper than the 3U mount rack case and perfct size .
Also has two spaces for a cable gland to mount and I could cut some slots in it with a jigsaw for ventillation.

http://www.fwb.co.uk/mall/productpage.cfm/FWBGroup/EAQ702

Heres a link to a data sheet http://www.tempapano.com/katalog/e11-SSETS.PDF

The walls are a bit thin but I could bolt a piece of aluminium sheet onto the wall the heatsink touches and put some thermal compund behind it to ensure good contact.

Bit over my £200 budget now:

• Driver (including P&P £99.00
• Amp (including P&P) £85
• Wood ~ £30 - £40
• Enclosure (including P7P) £30

So about £250, think thats all worth it, I originally only planned to spend about £150?

By the way, whats the link for that plate amp wimslow audio sell? I have not been able to find it.

Those cases are for holding fuse panels, switches etc. They have a locked door. It would work, but won't be elegant. Do not use a jig saw, it will make a terrible mess. Have someone cut the holes with a Plasma cutter. Personally I think you should build your case from scratch.

Here is the Wilmslow amp link.

Honestly, that amp is your best and safest solution. I would save up some money and use that. The case is a big part of the cost of any unit as you are finding out. The case is not just cosmetic either.

 

[s162216]

BK Elec do one that is exactly the same (200W RMS) for £149.99 and looks practically identical almost.

http://www.bkelec.com/Modules/bsbp200.htm

Do you think the 100W RMS version would be good enough as I am thinking of cost now, and since I originally was thinking of about 100W RMS anyway. Its only £117.00.

http://www.bkelec.com/Modules/bsbp100.htm

 

[s162216]

O.K, any USA power amps are out, that Dayton one draws 400W, the only transformer I have found that supports that sort of load costs £99, way, way, way too much.

I now have a bit of a dilemma, should I pay more for the 200W version or less for the 100W version. Being mindful that most of the time this sub will only be on half or less power to not make too much noise, I think I should get the 100W version.

Edit: Just noticed that a lot of DJ equipment is in my price range, such as this one here which gives 150W rms at 4 ohm over one channel, I don't really mind leaving a free channel. £95.00

http://www.getinthemix.co.uk/DA300-Warrior-Amp-By-W-Audio.htm

And this one, http://www.djstore.com/item/amplifiers/sky171102.htm practically the same for £90. I know the outputs are 6.3mm, but I can easily adapt them.

This one heres slightly more expensive but does 200W rms

http://www.djkit.co.uk/product.php?id=85&cat=42

Edit: Heres it for slightly less:

http://www.swsoundandlighting.co.uk/Adobe%20folder/pages/W%20Audio%20DA-500%20Amplifier.htm

 

[TLS Guy]

BK Elec do one that is exactly the same (200W RMS) for £149.99 and looks practically identical almost.

http://www.bkelec.com/Modules/bsbp200.htm



Do you think the 100W RMS version would be good enough as I am thinking of cost now, and since I originally was thinking of about 100W RMS anyway. Its only £117.00.

http://www.bkelec.com/Modules/bsbp100.htm

The 200 watt plate amp is what you need. That will be absolutely perfect. It has everything you need. The 100 watt job will not be powerful enough. You always have to slightly oversize those plate amps. That is exactly what I have been looking for. The Wilmslow unit is over sized for your needs.

Look no further, with that amp, the selected driver and a well built box, that sub will do everything you want. The 100 watt amp is too small.

 

[TLS Guy]

O.K, any USA power amps are out, that Dayton one draws 400W, the only transformer I have found that supports that sort of load costs £99, way, way, way too much.

I now have a bit of a dilemma, should I pay more for the 200W version or less for the 100W version. Being mindful that most of the time this sub will only be on half or less power to not make too much noise, I think I should get the 100W version.

Edit: Just noticed that a lot of DJ equipment is in my price range, such as this one here which gives 150W rms at 4 ohm over one channel, I don't really mind leaving a free channel. £95.00

http://www.getinthemix.co.uk/DA300-Warrior-Amp-By-W-Audio.htm

And this one, http://www.djstore.com/item/amplifiers/sky171102.htm practically the same for £90. I know the outputs are 6.3mm, but I can easily adapt them.

This one heres slightly more expensive but does 200W rms

http://www.djkit.co.uk/product.php?id=85&cat=42

Edit: Heres it for slightly less:

http://www.swsoundandlighting.co.uk/Adobe%20folder/pages/W%20Audio%20DA-500%20Amplifier.htm

Any of those should work fine also. You will have two units, but that is not a big draw back. Pro amps usually have pretty loud fans, but you may be able to change it for a quieter one.

 

[s162216]

I think I will get this one, here: http://www.swsoundandlighting.co.uk/Adobe%20folder/pages/W%20Audio%20DA-500%20Amplifier.htm

It is way cheaper than buying one of those plate amps and I am getting two for the price of one effectively as it is two 250W RMS channels. If I ever build for some reason in the furture a second sub, I could run it off that.
It does not have a phaser circuit but I can build one.

I emailed the shop selling the driver as to whether they would still be selling it in January and they told me that they may not as that driver is being discontinued soon possibly by JL audio and the W0 range has been released, which has crap specs compared for the 10" version, Fs = 32Hz.

So heres my plan:

At the moment I get about £60 a month and I am getting a part time job soon hopefully, so I will buy the driver as soon as I can and then save to buy the amp and wood. Those amps seem very popular so I don't think they will be going anywhere soon. I just hope I can find the wood somewhere cheap, at B&Q and Wickes at the moment it is £14 for 18mm MDF sheet, 2440mm x 1220.

Do amps normally use standard fan sizes? I could get a quieter fan then as suggested.

With the port, when I bend it around 45 degrees to go up the back, do I put a 45 degree angle on both the inside and outside (touching wall) angle and how would I keep the width constant?

 

[TLS Guy]

I think I will get this one, here: http://www.swsoundandlighting.co.uk/Adobe%20folder/pages/W%20Audio%20DA-500%20Amplifier.htm

It is way cheaper than buying one of those plate amps and I am getting two for the price of one effectively as it is two 250W RMS channels. If I ever build for some reason in the furture a second sub, I could run it off that.
It does not have a phaser circuit but I can build one.

I emailed the shop selling the driver as to whether they would still be selling it in January and they told me that they may not as that driver is being discontinued soon possibly by JL audio and the W0 range has been released, which has crap specs compared for the 10" version, Fs = 32Hz.

So heres my plan:

At the moment I get about £60 a month and I am getting a part time job soon hopefully, so I will buy the driver as soon as I can and then save to buy the amp and wood. Those amps seem very popular so I don't think they will be going anywhere soon. I just hope I can find the wood somewhere cheap, at B&Q and Wickes at the moment it is £14 for 18mm MDF sheet, 2440mm x 1220.

Do amps normally use standard fan sizes? I could get a quieter fan then as suggested.

With the port, when I bend it around 45 degrees to go up the back, do I put a 45 degree angle on both the inside and outside (touching wall) angle and how would I keep the width constant?

Sounds like a plan. I would pick the driver up ASAP, if you plan on building a second sub, then two.

You only need a 45 on the back, between bottom and back. I designed the slot 2.5" high I think. So the distance between the inside corner and the center of the 45 angle piece needs to be 2.5", on the 135 degree line from the corner.

As to fan sizes it all depends, some standard, some not.

 

[walter duque]

Change Active to Passive Sub

Sorry wrong thread.

 

[TLS Guy]

I have a 400 watt downfiring sub. So that's 400 watts 4 ohm. I have an extra channel off my power amp which is 350 watts 8 ohms. Is it worth changing it over, would the driver still be save and what would I need doing this. I realy don't have any idea where to start.

What is powering the sub now, and how many watts does your amp deliver into a four ohm load?

 

[walter duque]

What is powering the sub now, and how many watts does your amp deliver into a four ohm load?

Sorry for ending up in this thread. Actual output of the plate amp is 380 watts into 4 ohms. It's a 12" driver.

 

[TLS Guy]

Sorry for ending up in this thread. Actual output of the plate amp is 380 watts into 4 ohms. It's a 12" driver.

Well we need to know the power the driver can handle, and how much power the amp you propose to use will deliver. Unless the driver can handle 700 watts and your amp push 700 watts into a four ohm load, it is not worth the trouble.

 

[walter duque]

Well we need to know the power the driver can handle, and how much power the amp you propose to use will deliver. Unless the driver can handle 700 watts and your amp push 700 watts into a four ohm load, it is not worth the trouble.

That I would have to find out. What would I need just to check it out. If it's too costly I leave it the way it is. Thanks

 

[TLS Guy]

That I would have to find out. What would I need just to check it out. If it's too costly I leave it the way it is. Thanks

The amp specs should be in the owners manual. You will have to check with the speaker manufacturer about the power handling of the driver in the sub.