bmwuk
Well-Known Member
Wow, I love the look. I'm sure I can understand the parallel vs in line has bitriometry eventually but the cabinets look cool
What happens when Flint makes a Line Array?
- Thread starter Flint
- Start date
D
Deleted member 133
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Not sure what that word means but perhaps I can help with respect to understanding the differences between parallel and series connections...
Being a mechanical engineer (rather than electrical) I like to think in terms of mechanical analogs.
Instead of voltage, current and resistance of a simple circuit consisting of current flowing through a resistor because of the push provided by a voltage difference, one can think of pressure, flow and ... well resistance through a pipe, where a valve is analogous to a resistor.
All else being equal if I increase the line pressure more water will flow through the valve. I can also open and close the valve to varying amounts, thus changing the resistance, and hence the flow. If I add another valve just downstream of the first one (a series connection) the flow must go through both and the pressure drop across the two is now higher than just across the one, and the flow decreases. The pressure drop across each valve equals the pressure drop across the two together. That's how a series connection works.
But I can also get more pipe and connect the second valve around the first one. Now the flow has a choice of going through either one and as a result there is more total flow through the system. The total pressure drop across the system is less than the sum of the drops across each valve. The flow resistance has decreased in the case of such a parallel connection.
Unlike just about every other piece of math that I faced in university, I found that doing the actual calculations for the mechanical analog much harder than the electrical. Pipe diameters (as opposed to wire thickness) and bends / corners, junctions etc. must be taken into account - and have a much larger effect on the outcome than in the electrical case. Regardless, in the simplified case the mechanical analog does help to explain why a series connection of resistors results in an increase in overall resistance, whereas a parallel connection results in an overall reduction in overall resistance.
Jeff
D
Deleted member 133
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ps. I also think that something like speaker design and construction is a perfect (and rather elegant) blend of both the mechanical (vibration / sound / structural strength) and electrical (wiring / speaker impedance), and hats off to Flint for being able to master the intricacies of both!
In my brain everything that makes up a speaker is a resonating entity with it's own properties and excitations. So, every single component and part of a component needs to be considered to either enhance or reduce fidelity in how it resonates and interacts with everything else. It is all interconnected and inseparable.
And, thanks. That is one of the most meaningful compliments I've ever gotten over my interest in this hobby.
It is now official. As of this morning's sanding session, I have spent more man-hours finishing the woofer cabinets than I spent building them. This is the worst part about making speakers, for me. I like a good looking speaker, but I'd rather listen to an amazing sounding and crappy looking speaker than listen to a crappy sounding and amazing looking speaker.
Hence the delay in finishing my woofer cabinets..............
It's all in the prep work and I know that I will want them to be damn near perfect.
That's why I am procrastinating.
What sucks is that I am cutting corners to save time and/or money. These will not be gorgeous cabinets, but they will look way better than if I just sprayed them black with Krylon paint. Ugh.
I wish I had a friend in the wood finishing world who would just do this for me at very good rates.
I wish I had a friend in the wood finishing world who would just do this for me at very good rates.
Got tired of working on these enclosures, so I balked on coloring the back surface, including the black sunburst on the rear edge. So, I am going with the look in the photo below. Currently applying a couple of coats of clear gloss polyurethane to complete the finishing. The rear will be plain MDF with Shellac finish.
I declared the period of trying to make the subwoofer cabinets look attractive completed yesterday and allowed the final coats of Polyurethane to dry overnight. This morning I moved the cabinets into my front room and started the wiring process. I happened to have a bag of small red silicon rubber washers which are perfect to use on the terminal bolts I am installing to wire up the amp. The silicon will seal the hole without needing to resort to glue, caulk, or some other means to seal those holes. It is important the boxes are completely airtight if I want to get the benefits of my carefully engineered acoustic suspension design.
Here's the bolts with the speaker leads connected and the silicon washers:
Notice I used some cheap nail polish to paint the tips of the bolts so I can easily see which is connected to a red (positive) wire and which his connected to a black (negative) wire.
Here's the bolts with the speaker leads connected and the silicon washers:
Notice I used some cheap nail polish to paint the tips of the bolts so I can easily see which is connected to a red (positive) wire and which his connected to a black (negative) wire.
I then simply inserted the bolts through the holes I drilled in the sandwich of two 1/8" Plywood sheets and secured with a washer and nut.
Image from the inside:
I painted a 3/4" washers with bright red enamel and oven dried to make it as hard as possible and used the washer on the positive terminals:
The bolts do not protrude past the end of the hole I countersunk for them. This way I can lay the cabinets on the backs and not scrape the floor or break the makeshift terminal cup:
Image from the inside:
I painted a 3/4" washers with bright red enamel and oven dried to make it as hard as possible and used the washer on the positive terminals:
The bolts do not protrude past the end of the hole I countersunk for them. This way I can lay the cabinets on the backs and not scrape the floor or break the makeshift terminal cup:
Once the wiring was complete, I placed the cabinets on the floor facing up and started filling with acoustic stuffing.
I used a few yoga mats to protect the floor and cabinets:
Then I opened the bags of cotton based down-replacement stuffing intended for pillows and quilts - a total of 10lbs, or 2.5lbs per enclosure, and yes, I did weight the stuffing to ensure I equally divided it between the four enclosures:
Next, to reduce the chances of the loose filling from dropping into the voicecoil and mechanical structure of the woofers, I used some bonded cotton sheet intended for quilts and blankets to hold the loose down-replacement back from the woofers:
Finally, I connected the speaker leads to the subwoofer drivers and set them into the speaker holes. I won't mount them until I can put some neoprene closed cell foam tape on the rear of the woofer frame to ensure a good seal in the enclosure:
You may have also noticed the felt feet on the cabinets. After looking them over to see which had the best top or bottom panels in terms of my painting skills, I decided which two I want on the top of the stacks.
I used a few yoga mats to protect the floor and cabinets:
Then I opened the bags of cotton based down-replacement stuffing intended for pillows and quilts - a total of 10lbs, or 2.5lbs per enclosure, and yes, I did weight the stuffing to ensure I equally divided it between the four enclosures:
Next, to reduce the chances of the loose filling from dropping into the voicecoil and mechanical structure of the woofers, I used some bonded cotton sheet intended for quilts and blankets to hold the loose down-replacement back from the woofers:
Finally, I connected the speaker leads to the subwoofer drivers and set them into the speaker holes. I won't mount them until I can put some neoprene closed cell foam tape on the rear of the woofer frame to ensure a good seal in the enclosure:
You may have also noticed the felt feet on the cabinets. After looking them over to see which had the best top or bottom panels in terms of my painting skills, I decided which two I want on the top of the stacks.
Next up (including receiving the neoprene tape for the woofers) I need to build some basic wood mounts for the amplifiers. I intend to mount an amp on the rear of each of the bottom woofer cabinets. These won't be fancy projects, I just need them to be secure with some ventilation and not rattle or vibrate.
Now that I've been able to observe the finishing job I did with the MDF in my living space, I am pretty pleased. As long as one doesn't look closely at the surface, it looks like a nice sunburst wood finish. However, it doesn't take much inspection at all to realize the woodgrain was painted on and finish has some runs and isn't half as smooth as it should be. So, for a low budget speaker, it looks very decent. As long as I don't take the value of my time into account, these are stupid inexpensive speakers.