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Joe X

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Posts posted by Joe X

  1. Went for a 2.5:1 to save some space, 2 cubic feet per driver for the rear chamber:

     

    projected frequency response:

    FR.png

     

    Cone displacement:

    CD.png

     

    Vent airspeed:

    VS.png

     

    TOTAL BOX SPECS:  4, 10@45Hz  240 SQIn of port area.

     

    Bear in mind that this type of enclosure needs strong midbass drivers on your front stage, it is not like ported.

     

    Also the port must be removable so that you are able to re tune if necessary.

     

    Finally the sundown design is set for maximum output so if you are into sound quality you may not be impressed.

  2. Sundown X work bad in sealed so it is understandable that sundown gives a 3:1 so do it but enclosure will be huge. and the rear chamber at 2 per sub is fine, I just made you something that is not so peaky. My specs that I gave you are per sub bear in mind that.

     

    If you want to enter the volume of the full enclosure you need to define two subs or the model will predict all wrong.

     

    The tuning you must use is not what sundown have in their website, that tuning is for a ported box, as before, the tuning you use should be close to the sealed resonance (that number on the left you can't change), look at the arrow pointing at the said number:

     

    bandpass.png

     

     

  3. Also bear in mind that your box is too large and tuned too low, the tuning you need to set is close to the sealed resonance of the rear chamber which is the number on the left in WinIsd, in a 4th order bandpass tuning has a different role than in ported, it does not determine how low the box will play. check out the box specs I left you in my last post.

  4. Yes exactly, cabin gain is added to those curves, it is a generic form so do not expect exceptional accuracy, still, adding a generic cabin gain results in a better representation of what you will be getting than adding nothing. Anything below 20Hz in those plots you can ignore.

     

    6th order would be much larger than ported and 4th bandpass even if that happened to work out it would not be worth to build, modern subs work in so much lower airspace and yet you don't see everyday someone building a 6th order with 18 subs.

     

    Now you couldn't use as HT box a car audio box, you would need to re tune the box to the lower 20s to work as HT.

     

  5. These are the official params for your sub:

     

    TS.png

     

    From what you measured it looks like your sub is stiff either because of not getting broken in or due to possibly aging.

     

    I came with 2 specs, a 4th order bandpass ( in blue ) and a ported ( in orange )

     

    FR.png

     

    Specs for each are:

     

    BP4:      4, 6@47Hz 50 in2

     

    Ported:   6@30Hz 30 in2

     

    Ported would be the enclosure of choice delivering a nice relatively flat performance with low group delay, good for sound quality.

     

    The bandpass is just too big with just marginal gains in output.

     

    My impression: I wouldn't bother to build a big box for a 250W woofer, also it is an old sub and  might fail at any time due to that. You should keep power low to help it last more.

     

    The sub is highly efficient as is the case with old subs so you will get relatively loud on very low watts at the price of a giant enclosure.

     

    What I would do is build a ported enclosure but with a modern sub port area of about 90-100 square inches so that you can upgrade later to a high power sub that make it worth carrying around such large enclosure.

     

     

  6. Cut port area when you are looking for plain SPL does not sound right, do software modeling on the power you intend to run maximizing volume and port area as possible within the space you have to work with and very important keeping proper port clearance, single box not dual boxes, the type of box you show is right for SUVs. Just bear in mind that plain SPL boxes don't sound that nice, if you want to to sound nice, you can't go far above sundown specs. 

  7. After using modeling software for a while I can tell you that as long as the sub you use is made for car audio and is from a reputable manufacturer, following the recommended enclosure suggestions that the manufacturer provides will get you good results used in a car. The manufacturer has already figured what needs to be done and has tested in a number of vehicles their product to produce satisfactory results. That be a sub for sound quality or for high output.

     

    That said you are looking for general information? or you have a specific problem that you are trying to solve, if so you might want to tell us about it as you can get the answers you need faster.

  8. Yes inside a small chamber like a car cabin you get a significant boost in low frequencies compared to playing outdoors , this is known as the cabin transfer function or more commonly as cabin gain, it is roughly modeled as a 12dB/octave rise downwards in frequency starting at a frequency that depends on the size of the cabin mainly, for an average sedan that frequency is about 50Hz. That is a very rough description, if you need to know exactly how your transfer function really is you need to do some measuring tests for the vehicle in question as well as the listening position.

  9. You just need to make sure your subs do not go over Xmax at the operating power, but since your amplifier exceeds by far the RMS of your subs you will have to be very careful not going too far, generally oversized enclosures and sub overpowering in a hazardous mix with a very likely outcome of subs mechanical damage so you need to set the gain of the amp not to the clipping point but rather lesser that the subs can can tolerate.

     

    You can find maximum power in a similar way as before, in WinISD up power until Xmax is reached in the enclosure size you chose and you can clamp the amp to roughly reach that power and set gains accordingly so you can't go over the limit on normal use.

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  10. The new swr 12d4 will work on smaller boxes than previous versions, to determine the volume to use enter both the old and new models in winISD and change the volume of the new version to approximately match the curve the 2.1 cubes plot of the old one you have and use the same port area you had in your old box. Of course you need to check the excursion plot at the power you intend to use your new subs to be within Xmax, now you can build to the specs you just obtained.

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  11. No issue running your system like you do in fact may be safer for your hardware to run at low power, point is why pay for upgrading amp, subs and box and having a HO alternator to get similar results as before the upgrades? Anyways, you can post a video right here of your system or you can make a thread at the build logs section, describe your system and post pics and videos.

     

    https://www.stevemeadedesigns.com/board/forum/13-member-rides-builds-show-off-your-whip-show-off-your-system/

     

  12. Just use a voltage gauge connected to the amp power terminals to verify that you have a steady 13-14V, no other measurements. If your voltage is not steady and constantly dipping when the bass comes on you will very likely not be doing rated power.

     

    I would recommend not to buy Tramps or any other of those full bridge full range Brazilian amps, just get a Korean made half bridge amp about 2000W RMS and for wiring use 0AWG OFC wiring.

  13. Ok, try to pick an amp that has been tested with the amp dyno AD-1 to put the RMS power that is rated for. And try not to  go for full bridge amps unless you are willing to buy full electrical upgrades, go for half bridge amplifiers that will work on entry level electrical systems.

     

    Also using a voltage gauge connected to the amp power terminals lets you monitor the quality of your power, voltage shouldn't dip a lot when you are playing loudly and your voltage should stay preferably in the 13-14V range for optimal amp operation.

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