BiggerIsBetter Posted October 8, 2006 Share Posted October 8, 2006 I am looking for 18" woofers for my new bass horn scoops, looks like I am get shafted on the JBL 2240s that were part of the deal. My understanding is that I need a woofer with a high Fs and low Qts. I have seen good deals on the Omega Pro 18, but there seems to be 2 sets of specs that are stated. The Eminence website has a Fs as 24 and .31 for Qts and no reference to an older (or newer) model with different spec. Several sites that sell the same model number woofer (including parts express) state specs of 28Fs and .24 Qts (which would be seemly better in this application. I have seen reference to "new" spec Omegas, but again no info on their website. Any ideas on on whether there was a change and any way to tell the difference between the 2? Other woofer suggetions also appreciated. Quote Link to comment Share on other sites More sharing options...
BEC Posted October 8, 2006 Share Posted October 8, 2006 There are actually 3 Omega Pro 18s. Omega Pro 18A Omega Pro 18C Omega Pro A-2 All are different. I can send you PDFs on them from my Eminence dealer catalog if you want. Bob Crites Quote Link to comment Share on other sites More sharing options...
BiggerIsBetter Posted October 8, 2006 Author Share Posted October 8, 2006 Thanks Bob. I would guess that the one I am looking for is the A-2. The 18A and C are the ones currently listed on the website with the higher Qts and lower Fs. I have not seen anyone refer to an A-2, but that must be it. Does the A-2 spec sheet have an Fs of 28 and Qts of .24? Jim Quote Link to comment Share on other sites More sharing options...
djk Posted October 8, 2006 Share Posted October 8, 2006 What frequency are you going to cross these at? You only want a low Qts driver if you intend to run it up high. Just like the Klipschorn, a lower mass corner driver will have better low end, a higher mass corner driver will have better high end. Quote Link to comment Share on other sites More sharing options...
Duke Spinner Posted October 8, 2006 Share Posted October 8, 2006 where's the Corner ....inna Scoop ......[] my scoop cab's like to be crossed no higher than 800 hz .... Quote Link to comment Share on other sites More sharing options...
BEC Posted October 8, 2006 Share Posted October 8, 2006 I read the catalog wrong, the 18A-2 is a Sigma Pro. Here is its specs as a PDF. Bob sigmapro-18-2.pdf Quote Link to comment Share on other sites More sharing options...
BiggerIsBetter Posted October 8, 2006 Author Share Posted October 8, 2006 The 18A-2 has a Fs of 28 and a Qts of .29. Now I'm really not sure what several places are advertising as an Omega Pro 18 with a Qts of .24, it's not the 18A or A or the 18A-2. As an example, here parts express lisitng (they call it an 18A) http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=290-428 I doubt it is a typo since most places list the spec as 28 Fs and .24 Qts Right now I am using a 400 hz round tractrix, crossed over at around 700hz. If/when I get a bigger horn I would like to try to go as low as 225hz on the crossover with the BMS 4592. Everyone is telling me the compression driver will sound like crap that low, but I think these drivers will do it with no problem so I need to hear it to believe it. Quote Link to comment Share on other sites More sharing options...
BEC Posted October 8, 2006 Share Posted October 8, 2006 Here is the 18A set of specs from my Eminence dealers CD. Bob omegapro-18a.pdf Quote Link to comment Share on other sites More sharing options...
BEC Posted October 8, 2006 Share Posted October 8, 2006 I will go ahead and post the 18C specs. By the way, I can probably save you a little on any of the Eminence woofers compared to what Parts Express charges. Bob Crites omegapro-18c.pdf Quote Link to comment Share on other sites More sharing options...
djk Posted October 9, 2006 Share Posted October 9, 2006 "where's the Corner ....inna Scoop ......" The curve marked 2220 is a speaker mounted in an infinite wall (flush in a 200' X 200' roof) with a 10 cu ft box behind it. Note the roll-off below the mass corner of about 400hz (EBP X 2). Note the bottom curve marked 2235, and how it rolls off below about 160hz (EBP of about 80). The scoop adds horn loading below about 80hz, dropping to zero gain above about 150hz. The maximum output of the system is inversely proportional to the EBP, the lower the EBP, the more maximum output. Above 150hz the response will follow the curves in fig.5, so we see that the lower the mass corner, the better the maximum output in the bass. A lot of bands and DJs cross scoops below 160hz, so it makes no sense to use a high mass corner driver in that application. Quote Link to comment Share on other sites More sharing options...
BiggerIsBetter Posted October 9, 2006 Author Share Posted October 9, 2006 djk, thanks for the info. Not sure I completely get it, but did have a specific question on the formula's under Fig. 6. If you take a 2240 with a Qts of .24 and a fs of 28 hz for example, we would get: flc = .24 x 28/2 = 3.36 fhm = 2 x 28 / .24 = 233 That seems right for the high cutoff, what wrong with the calc for the low (i.e. 3.36). I would have expect a low cut of around 40hz. Quote Link to comment Share on other sites More sharing options...
djk Posted October 9, 2006 Share Posted October 9, 2006 The low cut-off is what would be possible if the horn was big enough. A driver with an Fs of 100hz will be able to drive a 10hz horn if its Q is correct, and the horn is big enough. In practice the horn is never big enough, so the equation for low cut-off is kind of moot. Quote Link to comment Share on other sites More sharing options...
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