Rudy81 Posted December 27, 2010 Author Share Posted December 27, 2010 Yes, you have to wire the drivers out of phase, or else they will fight each other. Quote Link to comment Share on other sites More sharing options...
psg Posted December 27, 2010 Share Posted December 27, 2010 Fantastic build! Congratulations! How loud will it go? Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 27, 2010 Author Share Posted December 27, 2010 Fantastic build! Congratulations! How loud will it go? Don't know that yet. I am finishing the paint and then I'll have to lug them up to my media room. I can then hook them up to the Behringer ep4000. I'm sure they will be louder than I will ever listen to them. Quote Link to comment Share on other sites More sharing options...
Chris A Posted December 27, 2010 Share Posted December 27, 2010 I am pleased with the performance, but can't figure out the dip near 120Hz. I beleive the sub will work well for my LFE channel, from 15Hz to 125Hz.Let's see - 120 Hz has a wavelength of about 9.4 feet (in air at ground level and close to room temperature), or a half-wavelength of 4.7 feet. Is that about the height of your microphone off the floor, ceiling or wall?The crossover frequency of 120 Hz sounds high - is there a reason why you are crossing at that point? Chris Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 27, 2010 Author Share Posted December 27, 2010 Chris: The mic was about 3.5 feet off the ground. So that is about right. I am not crossing anything over at 120Hz per se. My pre/pro can send any LFE information to the dedicated sub circuit from 125Hz on down. That is, purely the LFE channel, so we are talking movie soundtracks almost exclusively. I will not be using these subs for music at all. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 28, 2010 Author Share Posted December 28, 2010 Here is the free air impedance curve of a single Tang Band W8-740P driver. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 28, 2010 Author Share Posted December 28, 2010 Here is the plot for two drivers wired in series with one driver out of phase as it will sit in the enclosure. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted December 29, 2010 Share Posted December 29, 2010 That's the same driver I put in my TUBA18. It's a pretty stout little bugger. I imagine 4 of them will make considerable noise. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 29, 2010 Author Share Posted December 29, 2010 That's the same driver I put in my TUBA18. It's a pretty stout little bugger. I imagine 4 of them will make considerable noise. I certainly hope so. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 29, 2010 Author Share Posted December 29, 2010 Managed to lug the unit up to the listening room today. Completed one and here is the impedance sweep of the completed tapped horn. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted December 30, 2010 Share Posted December 30, 2010 Rudy, allow me to show my ignorance if you will. Exactly what does the chart show and how do the graphs relate to performance? It looks like it shows system resistance over the sound spectrum. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 30, 2010 Author Share Posted December 30, 2010 I am the wrong person to explain all this to you. I got the measurement tools when I was working on the DBB bass bins. I used it to mesure the Fs of that enclosure as well as get some data on the Kappalite drivers. I did the same for the Tang Band drivers just to establish some parameters. I do know that if there is a problem with the enclosure, like air leaks or other issues, it will show up here. I can compare my results with others published of similar DIY projects and see how close the builds ended up. If there are any problems with the drivers, it will show up in the impedance plot as well. The guys that know a lot about this stuff can tell a lot about the driver and the enclosure from the various plot results. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted December 30, 2010 Share Posted December 30, 2010 Actually that makes sense, thanks. Does the graph give you the Fs of the enclosure? I can't read it well enough to tell. I know the Fs of the driver is pretty high for a subwoofer (28? I think) but I'm used to working with bigger drivers. I wonder if you measure a horn cabinet the same as a ported cabinet? There's a heck of a lot that I don't know on this subject, but it's fascinating to me. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 30, 2010 Author Share Posted December 30, 2010 I have been trying to learn as much as possible on the subject as well. The TB driver supposedly has an Fs of 28Hz, but my free air measurement came up with 36Hz, and in all honesty I don't know the reason or relation to those numbers. I learned how to tell the enclosure tune from my runs on the DBB and what guys taught me. However, I have no idea how to properly read this sub's chart. For now, I am mainly comparing the results with other published results to see if I'm in the ballpark. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted December 30, 2010 Share Posted December 30, 2010 The Fs (free air resonance) should lower as the driver breaks in. The suspension and surround are brand new and tight, once it loosens up, I would think that it would measure closer to the published spec. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 30, 2010 Author Share Posted December 30, 2010 Just finished putting together the second unit and the good news is that the impedance curve is pretty much identical to the first cabinet. The cabs are complete. I will have to wait until I get a chance to set up the amp and hook the subs up to the crossover. Then, it will be the tedious task of setting everything to play well together. Quote Link to comment Share on other sites More sharing options...
Chris A Posted December 30, 2010 Share Posted December 30, 2010 The TB driver supposedly has an Fs of 28Hz, but my free air measurement came up with 36Hz, and in all honesty I don't know the reason or relation to those numbers All dynamic drivers must "break in"...and I think that your measurements will change after you exercise them for about 1/2 hour at very low frequency/high amplitude.Or you can just put on the first depth charge scenes from U571 a couple of times... [] Chris [] Quote Link to comment Share on other sites More sharing options...
Chris A Posted December 30, 2010 Share Posted December 30, 2010 However, I have no idea how to properly read this sub's chart. For subs, I would think that the FR curve and the phase (or group delay) curve, as assembled, are pretty good indicators that they are performing without major issues. The one FR curve that you published looks good, especially since the drivers haven't been broken in yet. Chris Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted December 30, 2010 Author Share Posted December 30, 2010 Thanks Chris. I am assuming all is well since those plots resemble others I have seen in various TH posts. I like the U571 idea. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted December 31, 2010 Share Posted December 31, 2010 I could suggest playing the danley fireworks recording a few times (I think it has some 10 hertz in there) http://www.danleysoundlabs.com/knowledge%20baSE.htm Quote Link to comment Share on other sites More sharing options...
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