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Triticum Agricolam

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Triticum Agricolam last won the day on June 18

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About Triticum Agricolam

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    170db

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  • Gender
    Male
  • Location
    Eastern Washington State
  • Interests
    Speaker enclosure design & construction

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  1. My experience with both T-nuts and hurricane nuts has been poor. It seems like they cross-thread really easily and when that happens you are going to have a bad day. I won't touch either of them any more. I've gone to using #10 pan head sheet metal screws for most stuff and the SMD Blackjack screws for really big subs. The key to getting screws to bite well is to make sure they aren't just going into MDF. Plywood holds screws REALLY well while MDF never seems to hold screws worth a darn in the long run. I avoid MDF altogether, but if you want to use it you can make just the baffle out of plywood. If you don't want to do that or if the box is already built you can just glue some blocks of 3/4" plywood to the back side of the baffle where the screws go through, then just make sure you are using long enough screws to reach all the way into the plywood blocks. If you wanted to be fancy you could make a plywood ring in two pieces and glue that inside. One thing I really try to avoid is any drywall screws or deck screws. They are plenty strong enough for the job, but the back side of the head where it is tapered really isn't the best thing to be putting through the hole in a basket, you want something with a flat contact area. This is why I prefer pan head screws or cap head screws, even better if you can find them in square drive.
  2. If you are looking for wider bandwidth, and it sounds like you are, the parallel-tuned 6th order is most likely going to do that better. You are certainly correct about being concerned with the peak the 4th order has. You can ROUGHLY approximate what cabin gain is going to do by adding a filter into WinISD like this: See how it looks with the filter. Keep in mind that peaks can be reduced very effectively though EQ. If you are concerned about frequency response a DSP is the best $100 you can spend on your system.
  3. You can use MDF if you want, though I would argue that a quality plywood has its benefits. What I was mainly referring to is that you wanted to use 1" thick material. A sheet of 1" MDF weighs about 120 lbs. It absolutely sucks to work with. All the extra weight isn't gaining you much either. You would be much better off with 3/4" MDF and using the weight you saved vs 1" material to add bracing and doubling up on certain panels that would actually benefit from being two layers thick.
  4. Unless you already have a pile of 1" MDF you want to use up, there is no good reason to use 1" MDF. Zero. None. What are the max dimensions of your space?
  5. There is no single "correct" curve. It depends entirely on what your goals are and how you want your system to sound.
  6. Do you have a specific question? What kind of help are you looking for?
  7. Power handling doesn't make a sub louder by itself. More cone area usually DOES make a sub louder. The four 18"s will almost certainly be louder. The real question is if they will handle 8k a piece and for how long. I can't help you much with that.
  8. No, that's still not enough. You need three 4" ports, or a slot port of about 40 sq in of port area. You are basically in the same spot as ehall8702 was a few days ago. 1500 watts doesn't sound like a ton of power, but into a box for four 8"s it is and it takes a fair amount of port area to let that sound energy out. Here is his thread for more info: FYI, if you think you are going to run more power later, you should plan for that now with your port area. With that being said, you will NEVER hear the difference between 1500 and 2000 watts.
  9. You should have enough space for those subs based on the dimensions you gave. How much power are you going to be running? A single 4" port is unlikely to be enough port area.
  10. That's awesome man. Glad to hear it worked out well for ya!
  11. OK, I crunched some numbers. I assume you have a pair of these so each sub will be getting 500-600 watts? On that amount of power you will want to use a 6" port, a 4" port will be significantly undersized and you will almost certainly get a lot of port noise. Port noise is really noticable in home audio applications so it something you will want to avoid. A 6" port will need to be 11" long to tune it to 35 Hz. If it were me, I'd tune a bit lower since you don't get all the cabin gain you would normally get if this sub was used in a car, 30 Hz would probably be a good spot, the 6" port will need to be 16.5" long. I would be very careful with the power on these subs. These older drivers don't have much Xmax (only 6.2 mm). Modeling software shows you exceeding that significantly (almost double) on 600 watts. It would be easy to damage these subs. Be sure to set your subsonic filter 1/2 octave below tuning.
  12. How much power are you going to be running? How big of a port you will need is very dependant on input power. Here is something else to think about, that 5" port is going to tune you to about 35 Hz. Depending on what you intend to use those subs for you may want to tune a bit lower for in home use.
  13. I've been in the mountains all weekend, didn't see this thread until I just got home. First off, my port area calculator is not meant to be the final, definitive word when it comes to how much port area you need. Its intended for people who don't have access to box simulation software (like WinISD, BassBoxPro, etc) or for people who don't want to spend the time to use that kind software. That being said, my calculator will usually get you a pretty good number and if anything it errors a bit on the side of caution (which mean more port area), but simulation software will always be better. Some people here may disagree with me on this, but high port velocities are bad, ALWAYS and EVERY TIME. This is simple physics. Wind resistance through the port takes energy out of a system and turns it into heat, energy that would otherwise be output. Wind resistance quadruples every time you double air velocity. This is why port compression is no big deal when you go from 5 m/sec of port velocity to 10 m/sec, the numbers are still small. When you get above 20 m/sec it becomes pretty noticeable and above 30 m/sec it absolutely eats your lunch. I have measure this exact situation myself and have posted the results of that testing on this forum for everyone to see it. In your case ehall8702, you are wanting to put a LOT of power into a relatively small enclosure, once you get over around 1,000 watts per cubic foot, getting enough port area to effectively avoid port noise and high port velocities becomes almost impossible. Its just the nature of the physics and you do the best you can. There is good news though, you are only going to have issues related to not having enough port area when you are playing at maximum output, and right around the tuning frequency. As long as you aren't competing with the system that's going to be a VERY small amount of the time (for most people, it also depends a bit on the type of music you listen to). Because of this, you make your best effort to get as much port area as you can, and you accept that it won't be perfect all the time, and chances are you will still be very happy with the system.
  14. I hate to bring you bad news, but putting 3k watts into a 2 cu ft enclosure is a LOT of power for that size of box. To get three thousand watts of sound energy out of a box requires a significant amount of port area. There is absolutely no way you are going to be able to make a port work that is only 10.5" long unless you want to tune your box to about 50 Hz. These small, high powered, low tuned boxes are VERY difficult to design a well-functioning port for. With the amount of power you are running you would ideally have around 50 sq in of port area to keep port velocity reasonable, however a port that size would have to be way, way too long to be feasible and would eat up all your net volume. In this situation compromises will have to be made. Probably the best you are going to be able to do would be something around 35 - 40 sq in of port area, it will still have to be around 40+" long to tune to the low 30s and you will almost certainly still have an undesirable amount of port noise and compression, but that may just be the best you can do. If you only have space for a 10.5 long port you will be better off leaving it sealed.
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