iwillwalk Posted October 26, 2008 Share Posted October 26, 2008 i have a jbl 18' sub speaker & want to build the correct size & shape box where can i find dimensions ? here is the info on the speaker jbl jbl-1800 GTi model # J342-103797 serial # Quote Link to comment Share on other sites More sharing options...
iwillwalk Posted November 19, 2008 Author Share Posted November 19, 2008 anyone? any ideas where tto get the correct box size Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted November 19, 2008 Share Posted November 19, 2008 Well,,,,,,, it turns out there is great deal more to it than that. It is best to start by getting over to the DIYAUDIO forums. First, You will need to find the T/S parameters for the driver. Second, you will need to figure out the alignment (style) you will be using, and this in turn will be dictated by the T/S parameters. It is do-able and ultimately you will find some of the shareware programs to be very useful (modelling the various "what if" possibilities). Unless it is a proven design, don't build it until you have modelled it first. Good Luck, -Tom Quote Link to comment Share on other sites More sharing options...
Guest " " Posted November 19, 2008 Share Posted November 19, 2008 It's designed for a vented enclosure. The Fs number will help size port tuning. JBL - 1800 GTI TSP Parameter des Lautsprechers: JBL - 1800 GTIHauptdaten:Qts: 0,43Fs (Hz): 30Vas (l): 363Erweiterte Hauptdaten:Qms: Qes: Sonstige Daten:Preis: 615SPL (dB): Bemerkung:Elektrische, Mechanische Parameter:RMS (P): Re (Ohm): 4Mms (g): Cms (vm/N): BL : Dd (cm): Le (mH): Quote Link to comment Share on other sites More sharing options...
Guest " " Posted November 19, 2008 Share Posted November 19, 2008 step 2. Thinking something like a KP-480, except with a port instead of a radiator. so if you plug in 24X24X24 into a sub woofer calculator we get 6.5918 after wall thickness. tuning a 6.5918 volume cab to 30hz (the Fs frequency) using a 4" tube would require a tube lenth of 2.7824. if you want to get technical, which I am sure many will, you could place the sub woofer in a plastic bag and put in a tube of water to see how much water it displace's and then adjust the cabinet volume accordingly. The adjustment will either increase the cabinet size by a flea's higher, or change the numbers of the port about as much as a coat of paint will. now if you wait a few hours...this thread will be pounded on with corrections....it's the fourm way. enjoy Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 19, 2008 Share Posted November 19, 2008 A single 4" port is good for about a 12" driver, and not a very long throw driver at that. With an 18, I would suggest a slot port that has equal to or larger area than a single 8" vent. Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 19, 2008 Share Posted November 19, 2008 JBL is real good about providing documentation for all their products.http://www.jbl.com/car/product_support/default.aspx?Language=ENG&Country=US&Region=USA(the 1800 GTi is near the top in the drop down list) Here's the enclosure guide for your driver that also contains T/S params:http://manuals.harman.com/JBL/CAR/Boxes%20and%20Parameters/1800GTI.pdf Looks like they recommend a little over 11cu ft tuned to 28Hz(three 4" ports that are 5.5" long). The driver will do 5mm ofexcursion, so you'll need to feed it less than 300W to avoid bottomingit out in the passband. You should also put a 12dB high pass filterright around 30Hz to offset the cone-excursion below the tuningfrequency to make sure the driver is protected. However, thereseems to be some inconsistencies in the datasheet. It's claiming an SPLof 95dB with 2.83V at 1m, but later on the graphs are showing 100dBwith 2.83V for the various cabinet alignements. Also, the postedimpedance plot shows an impedance peak at 70Hz, but the Fs of thedriver is listed at 30Hz. Generally, the max impedance is whatdetermines the Fs so something isn't right there either. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted November 19, 2008 Share Posted November 19, 2008 It's a car woofer, and I am sure they are getting the 100 db/ 2.83 v in a car interior. Quote Link to comment Share on other sites More sharing options...
iwillwalk Posted November 21, 2008 Author Share Posted November 21, 2008 thanks for the input, but its to much data.....can someone just tell me the sizeof the box & port size thNKS I NEED TO GIVE THE DIMINTIONSTO SOMEONE TO BUILD IT sorry for the CAPS Quote Link to comment Share on other sites More sharing options...
DrWho Posted November 21, 2008 Share Posted November 21, 2008 Looks like they recommend a little over 11cu ft tuned to 28Hz (three 4" ports that are 5.5" long). Quote Link to comment Share on other sites More sharing options...
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