Wub Wub, time for something different.

[AlienALX]

Hifi related this time

So recently I changed my system. I added another set of speakers to the front array.

As well as another amp to run them. The speakers nearer to the floor are the ones I originally bought that were a little too much on the warm side of soft for my liking. That said they were £350 half price. The speakers I replaced them with? are £1800. I didn't pay that for them of course, I paid £750. Brand new also. They're phenomenal, but I then had the other ones and the original 60w Tag Mclaren amp I bought for them just sitting in my cupboard. Which is stupid. So I bought very small stands, added the amp into the rack and connected them up. Sounds super.

However, that left my subwoofer (8") feeling very much left out. Also, with the 70" TV upgrade came Dolby Digital surround mode through optical, which my old TV did not have. I either had Pro Logic, or pseudo.

The issue is that the new mode is far less "bassy". Meaning my subwoofer is getting utterly buried. Mostly because of position, but also in its lack of drop. I mean, it is a 8" subwoofer after all.

I wanted something larger, and something that goes at the back of the room aside the sofa. This way I will need less volume but feel it a lot more. I also wanted a larger sub capable of dropping down to around 30hz. Which the 8" doesn't do.

I started looking at purpose made cinema subs. Ouch ! £1000 for a 8". £1500 for a 10". OK this is silly. I know they have fantastic amplifiers in them but subwoofers to me are not something you could really class as "audiophile grade". They are, and always have been, a piston that moves air and not something you can truly really refine, given the depth of the frequency we are talking about here. There is no "clarity" at 30hz, it's sheer energy and shifting air.

So I wanted to build one. I looked at plate amplifiers (this type, that you cut in)

And soon realised that they are quite expensive. Not only are they quite expensive, but they are also really hard to get right now. I would imagine because of the 'rona.

I did notice that they seemed to cap off around 300w too. Then I realised that I already had one ffs. In the sub I have now.

It says 150W on but that is RMS at 8ohm. So I took out the woofer itself and measured the resistance and it seems the woofer is 4ohm, meaning the amp is 300w and thus pretty much the same thing I had been looking at already that cost more than I paid for that entire subwoofer.

So with the idea of just using the amp I had I started looking at subs. I ended up setting my mind on a 15" of some sort, and it came down to two. A JL Audio 15 and a Vibe Black Air 15. They both cost the same (£239). Then I started working out cabinet dimensions etc and soon realised that I would not only have to spend £43 for a sheet of 18mm MDF but I would also need to invest a couple of hundred quid in power tools with which to make said cabinet. And a lot of work.

So I left a couple of things in my watch list, and went to bed. When I got up and returned to Ebay the next morning I was shown this.

Which is obviously for a car, but is tuned to 30 odd hz. Which is perfect. It costs £289.99, so basically you are paying £50 for the cabinet and materials, on top of the sub.

Just one problem. Its utterly revolting. It looks like a chav's wet dream, and would have no place in a very nice system like mine. However, I then got to thinking about materials cost right now, tools, work and etc and started to think about it looking totally different. That was when I decided to throw a very cheeky offer of £250 over and see what happened. I mean, if it arrived and it was trash I had only paid £21 for it so I could use it as firewood.

Between the period of ordering it and getting it I had started to have ideas to make it look much nicer. I had numerous ideas. From peeling off that garbage carbon fibre look vinyl and carpet and putting acrylic on it (flat or gloss) to attempting to paint it* and finally veneer it with some exotic wood. Because veneer is pretty cheap, because it's so thin.

It came today. One thing I never knew was the dimensions of it (they don't tell you not even on their own website) and thus it was pointless buying anything until I knew that.

Well I got up around 10AM (not sleeping well ATM) and mum shouted "It's outside in the rain". So I got dressed and went down. The first thing that stuck out was it was on a wooden pallet. They had told me that, though. Secondly I noticed two boxes. Which was strange. So I figured they had packed the woofer separately to make it easier to move etc.

So after nearly giving myself a hernia (and now have pain in my groin) bringing in the cabinet I unpacked it.

Sure enough in the woofer box there was a woofer.

I still could not for the life of me figure out why the cabinet was so damn heavy. Then all of a sudden it dawned on me. Someone done F-ed up.

Sure enough when I finally strained myself getting all 40kg of it out I was confronted with this.

Whoops. I will now wait to see if they contact me. I am not telling them because TBH? it's so heavy (just the woofer) that I really couldn't carry it to the post office any way. So time will tell. If they realise? then by all means they will be welcome to have it collected, but I am not going to give myself another hernia (have had two before) buggering around.

OK. So the plan.

1. Remove all of the horrid vinyl.
2. Remove the horrid branding and tacky badge (I like the woofer itself).
3. Remove the carpet.
4. Veneer the front, two sides and top.
5. Paint any other areas and just leave the bottom.

So I decided on a veneer. I chose Ebony.

However I did not know how far it would stretch. So once I had the cabinet dimensions I knocked this up.

Loads. Loads and loads, more than enough. So I bought it, along with the correct contact adhesive needed to put it on.

I also bought a trim router, trim router bits and a roller (to get it down hard)

I did think about T moulding the outer lip, but soon decided that I will bevel it off with a router bit (curved) and then sand and paint after sealing. It's only that outer lip that needs doing paint wise.

So I set about stripping it. I yanked off all of the vinyl. It isn't like, 3M it's really thick tough stuff. Still nasty though. So that is gone. Turns out the cabinet is contstructed of 12mm (so 1/2" MDF) but the whole internal structure is doubled to 1".


After having a look at it I realised that the amplifier can not go in the back. I will explain this better tomorrow when I get more pics, but those ducts wrap around into the back of the box. Meaning if I cut the amp in there I would block them. Poop.

So I got hold of my mate and had him design me some legs. I will be using three of these. Two at the front and one in the middle at the back. These will be solid alu from the lathe, and threaded at each end. One end to bolt onto the box, and the other to take a spike.

Now the reason I need these legs? is because the only place the amp can go is in the bottom. Meaning it needs to be raised from the ground so I can connect the power and RCA cables to it.

OK. So aside from yanking off all of the vinyl and the nasty SPL badge and what not I have been working on the port ducts. See, I like those. A lot. They're a really clever design and look good. Without the stupid writing all the way down them and the fact they are silver.

So, I took them out. Which annoyed me. Every single screw hole is cracked. That said, at £21 I really can't complain at all. 5 corners were actually snapped off, so after sanding out the writing I reset them all with epoxy and epoxied all of the cracks. I will sand this out when it has fully hardened, and if needs be reinforce them from behind with JB weld.

And yeah, the stupid badge plates are going too. They will be painted in satin black.

 

[robbiec]

Cool log. Will be watching closely.

 

[AlienALX]

Cheers Robbie. It's something different. Which makes a nice change. Heavier to lug around to work on, but yeah something I haven't done in 20 years or more.

When I looked at the cabinet earlier I realised that I would also need to block off and fill the hole that the speaker terminals were in. Obviously I won't need those with a plate amp in there, as it's all done internally.

Must say, even the speaker wire Vibe use on the inside is nice stuff. I was expecting it to be terrible inside there.

One thing I do want to do is stiffen it even more. Well, deaden it even more. The port walls are only 1/2". 12mm. I mean, they are suspended in a 1" overall thick cabinet but yeah. Still prone to vibration. So I have ordered a 10 pack of these.

And will literally go over the entire interior.

 

[NeverBackDown]

You sure you can use a car subwoofer in a home environment? Cars are running at 12-14 volts but the UK electric panels are rated at 230/240v? You would need to do major electrical work on top of everything else you planned in order to match voltage

Or am I missing something here and completely misunderstanding what's going on?

 

[grec]

You sure you can use a car subwoofer in a home environment? Cars are running at 12-14 volts but the UK electric panels are rated at 230/240v? You would need to do major electrical work on top of everything else you planned in order to match voltage

Or am I missing something here and completely misunderstanding what's going on?

Easiest way to get equivalent to a cars ~12V DC power output would be using a standard 12V DC power supply, with one of those you can use basically anything meant for a car. But all that is only relevant to the amplifier power input of course, so another option would be to just change the amp, as the only real difference between a cars speaker and any other power wise, is that cars usually use 4-ohm impedance.

The rough voltage inside the actual speaker coils is always the square root of (Input Power * Speaker Impedance)*, with speakers usually being designed around ~71V (RMS) / 100V (peak) being the reference voltage for full volume, this voltage is ofc a sine wave.

* From (Power = Voltage^2 / Resistance)

 

[AlienALX]

You sure you can use a car subwoofer in a home environment? Cars are running at 12-14 volts but the UK electric panels are rated at 230/240v? You would need to do major electrical work on top of everything else you planned in order to match voltage

Or am I missing something here and completely misunderstanding what's going on?

Sort of !

A car amplifier is made to run between 12 and 18v. Well, a good one with strong power circuitry. That part is totally correct. However, I'm not using a car amp. I'm using a 240v plate amp (this one in this sub here)

At first I was worried that it may be an 8 ohm amp (as many 240v amps are) but Earthquake also do a lot of car audio, so I guess it was easier for them to make a 4 ohm amp and just use one of their existing car subs.

As for the speakers? they are all the same as home gear. The major difference with car audio is that a lot of it is designed to run at crazy low ohm (1 or 0.5) in order to get more power out of the amps. Meaning you also need dual alternators, many batteries etc.

I measured the sub in the Earthquake unit with a MM and it is a 4 ohm driver. Meaning the amp is obviously stable at 4 ohm.

The sub itself? has dual 2 ohm coils. Meaning you either wire them in series for 4 ohm, or parallel for 1ohm. I will be running it at 4.

Dual voice coils became a thing in the 90s. Mostly to drive down the ohm loads to craziness. Some have dual 1 ohm coils, meaning they can be ran at 2 or 0.5 (mostly competition stuff).


Here is where I got to yesterday. Having a break today. It looks pretty awful but that's only because it has a thin film of glue over it.

Not worried about that at all. When I put on the new glue it will level any way.

Side/front shot.

The edge I have started to remove the carpet from will be rounded with the edge trimmer. So all I need to do is get as much of those strands of carpet off as I can (or it will bind the router bit) and then just route it off.

Here you can see how clever that duct is. It goes all the way down the sides and around the back, in order to tune the sub down very low (IE very long port ducts) in such a small cabinet. And also why I can't put the amp in there, as it would block them completely.

I continued work on the ducts last night. Got off the tacky badges too. Will sand them out later ready for primer can't do anything outside atm as it's peeing with rain.

 

[AlienALX]

"There's always one".

Last night I glued back on six snapped of corners, due to the set screws being done up with a power tool. There were five, but I found another one snap off when I was working on it.

They all set perfectly. Strong, too. All apart from one. One fell off again last night, so I set it again after pulling off the epoxy.

Went back to it about an hour back, its not set correctly. FFS.

So this time I decided to add one ply of tissue to make fookin sure it stayed there lol. If any fail again? I am just going to remould them with JB weld. Hoping not to do that, and most of them are great (just need some blend sanding) but yeah.

The badges are gone now.

 

[NeverBackDown]

Oh ok I see my confusion now. I misread which plate you were using. I was under the impression you were trying to use the car plate as it was what you wanted instead of just the cabinet itself.

Pretty neat idea!

 

[AlienALX]

Oh ok I see my confusion now. I misread which plate you were using. I was under the impression you were trying to use the car plate as it was what you wanted instead of just the cabinet itself.

Pretty neat idea!

Yeah running car amps at home is really tricky. You could probably get away with a low powered amp (maybe up to 500w) on a very high amperage PC PSU (like 80 amp) but to do it properly? you need something mental like a 15v 220 amp PSU. As that is what a 5000w or so amplifier will draw when running at full load

Which is extremely difficult to find and prohibitively expensive.

I see guides on the net where people are using OEM silver PSUs to run car amps. Without realising that it's incredibly dangerous. Like, even using the stock 16 AWG power cable. There is a reason why amps have 8 awg mininum and up to 0 awg. Because of the amperage they want to pull.

I used to have an amp that had been fiddled with by an expert. Back in the 90s they would do competitions where you were limited to a 40w amp. SPL competitions, like. So people would take a specific 20x20W amp that bridged to 40w RMS, then modify the internals so it could run at 0.25 ohm lmao.

I had one of these amps, and I fried two car batteries with it lol.

 

[AlienALX]

Just pulled off the carpet. It now looks like this.

Will need a sander lol.

 

[grec]

Yeah running car amps at home is really tricky. You could probably get away with a low powered amp (maybe up to 500w) on a very high amperage PC PSU (like 80 amp) but to do it properly? you need something mental like a 15v 220 amp PSU. As that is what a 5000w or so amplifier will draw when running at full load

That's some crazy setups, power draws on the levels of small UK houses/flats, didn't know most cars then could deliver that much through the alternator, afaik most 12V lead acid car batteries wouldn't last 10 minutes at beyond 15A, since they don't really like sustained high discharge rates, so it must be risky leaving one of those on with the engine off, not surprised a couple blew. Guessing at those power levels it can get risky in the ASBO sense too when cranked up aha. I guess at that point if you were committed to setting up an amp like that at full power at home, you may as well just recreate the alternator too by getting a small 12-14V diesel generator lol

 

[AlienALX]

Well in a high end install you would not use either a regular battery or just one. You would use about 8 batteries, and use bus bars to connect them together. Batteries are capable of much higher amps than the alternator of course, and if you are not careful you will indeed fry your alternator. That's why you would either use a huge alternator or more than one.

As long as the battery is providing the alternator is not put under any strain, hence why they use tons of batteries.

To give you an idea.

Right. I did a thing. I was beginning to worry about the hole in the back of the box. I don't have any wood sheet spare at all, and it needs stuffing.

I measured the depth of the outer hole where the terminals sit. It was just over 9mm. I thought about cutting three acrylic discs and then putting them together with epoxy. Then I realised I actually had some 8.2mm acrylic. So, what I did was cut out the OD circle with that, then cut the ID circle with 3mm. All this does is just add up to make it thicker, and stronger. I would imagine at 11mm it will be more than stiff enough. I counter sunk the holes so they sit flush, then I will skim over on the outside with bondo. I have also decided to veneer the whole back. I was going to just do the top past the curve then cover it with something else but I don't see any point in that.

So that's the slug that will blank off the hole.

 

[grec]

Very interesting solutions, thanks for the info

 

[AlienALX]

Put that in last night with epoxy. It's not going anywhere

Like I said though.

Thankfully because it was carpet the contact adhesive is rock hard. Meaning it's sand able. Sadly right now the weather is crap.

 

[AlienALX]

OK slight update. Last night I got fidgety and decided to start working on it inside.

I've scraped off pretty much everything from the outer edge and inside the edge. I was going to leave the bottom with carpet on around that part, but I think I will pull it off later and continue the procedure. The edge is as hard as a rock due to the grain, but the insides have peeled a tiny bit. I expected this, MDF is like a wafer. I will bondo those edges any way.

Will get some pics in a bit.

The router came, it's really cool. So did the sander.

 

[AlienALX]

When it all goes wrong.

So the sun was out. Freezing cold but a nice day. Took it out back and hit it with the sander. Took all of the carpet off very quickly and left it perfectly ready to be veneered.

Sadly that was when it all went wrong. Spurred on by this confidence I decided to bevel the edge. Only what I did not foresee was that -

1. The router I bought is not really capable of this and
2. The bits I bought were rubbish.

It started off OK. Then it seemed to be acting weird. Now at this point I should have stopped, but I was rushing. As it turns out the bearing had come off of the router bit and I was destroying the cabinet quickly.

And that is what I have done.

I tried to come up with a plan B, but when I fitted the port I realised it was game over.

So, that one will be going off to the dump in the sky.

At this point I felt really bummed. Not even angry, which is unusual for me. Did some phoning around and it seems that B&Q still offer a cutting service, so I will have to get down there some point next week and get a new box cut.

One lesson I was taught many, many years ago is that a subwoofer box's biggest dimension should always be the depth. Always. I also learned that cube shaped boxes are really bad, as they cause terrible standing waves. So I did some poking around and came up with that.

Which I then transformed into flat pieces and put them down one by one on a virtual sheet to get the cutting order etc. This will save me cuts, which will save me money.

 

[AlienALX]

Quick update. The veneer has arrived, god, it's beautiful.

A friend of mine said to get it made by CNC. I figured this would end up being ridiculously expensive. However, I spoke to a company much earlier today who are reasonably local to me (about 20 miles away) and they are happy to do it.

I was given lots of options, but because the CNC service is so reasonable I decided to go for hidrafugal MDF. It's a bit of a mouthful, but basically it is harder and more dense, water proof and fire proof. It's also a whole load smoother, and doesn't "go fluffy" when sanded etc.

Have sent over the dimensions already, will pay for that tomorrow. With any luck this weekend I can start building, which I am way more excited about.

Have ordered the screws.

And these.

Which are a life saver. Otherwise you spend the entire time changing out bits. Which when you are talking about 50+ holes gets really old really fast. I also want to order some 90' clamps, as with it being CNC cut it will fit precisely, so I want it to be perfect.

 

[AlienALX]

OK forgot VAT. Total was £110. TBH? I am pretty thrilled with that, given the material itself is £60 per sheet and the delivery was £25 plus VAT.

I'm really excited now. I haven't actually built a speaker box since 2003, and I haven't done a decent one since the late 90s.



Then I ordered....

I want the edges perfect. Plus, these can be used to pre drill the holes into the edges so I don't get any splits. They can also hold the pieces when I assemble, as I can not just go gung ho and build the entire thing. Mostly because the port area needs painting black, and it will be extremely difficult if I do that once it is built.

Then the obvious.

This is for said port area, just to make sure.

This is to paint the bottom of the cabinet and said port areas, as well as being used to put down the contact adhesive.

I managed to rescue this label. Will use it.

And decided to get a badge for the front.

Then I planned out the veneer.

I am not that bothered about the grain direction tbh.

 

[Bartacus]

Wow, you've been busy, LOL! That badge looks pretty neat! The rest of it is stuff I don't understand at all, but I'm sure it's awesome. :-D

 

[AlienALX]

Wow, you've been busy, LOL! That badge looks pretty neat! The rest of it is stuff I don't understand at all, but I'm sure it's awesome. :-D

It's all just design and tuning dude. The cabinet is pretty much what decides how deep the bass will drop. The first cabinet I wrecked was tuned to about 32hz. This one is tuned to 24hz. Which a lot of woofers would not be capable of producing, but a 15 can. Some 12" can go down that low also.

You'll see what the tools do once the material arrives and I can get to work. The sound deadening finally arrived today which is a relief as that needs to go onto certain parts before it gets built.

There are still a couple of things I need. A good polyurethane to finish the veneer and a couple of other small bits. The bottom will be painted black, as will the inside of the duct, so I ordered some satin paint today.