BillFitzmaurice.info

Target curve. The easiest way to get a target curve is something called mirror imaging. Use this SPL chart. The first one at the top of this page: https://billfitzmaurice.info/forum/viewtopic.php?f=12&t=8778 Copy it, paste it into word, print it out. Get a pencil and draw a ruler line across the cha...

Yes. Other than behind the driver, anywhere you can see plywood Is the 30mm thickness of the foam too much? 25mm is enough. Did you use the "target" in the tutorial? If yes, that is a mistake. You need to set your target based on the SPL charts for the J12, and you will get different results. If yo...

Hi. Nice first build :) Is the beta 12 listed in your plans as a suitable driver? It's not listed in my old J12 plans. What size phase plug did you use? OK even if they sound really good to my ears I made some mistakes I know and mybe some I dont know. So I have couple of questions about my build if...

Go back to the SPL charts for the Otop 8. You'll notice, in some spots, the response from the Otop 8 is around +10dB compared to the JBL product. Across a large chunk of the chart it's +10 to +5dB. That's, depending on frequency, twice as loud, to (almost) a doubling of cabs. 2 a side would still be...

No my phase plugs are correct. But when I was building the 4th Otop I read the plans through again and almost had a heart attack because I thought I had installed the incorrect size. After researching ways to remove the phase plugs (to no avail) I decided the read the plans again and realized I was...

Are you specifically asking about the phase plug in Otops? Or those snazzy looking dodads you see poking out the front on some drivers? Doesn't much matter, the purpose of phase plugs is to modify response, increasing mids and/or higher frequencies (depending on the driver being a woofer or a HF dri...

Take Bruce's advice :) You are missing a couple of little things. Firstly, it's not volts DC, amplifier output is AC. Please remember that. Secondly, it's a matter of wiring. Two cabs a side daisy chained (ie parallel wired), sees both cabs getting the same voltage eg 35V, and impedance goes down, y...

Hey welcome back! Both home, and to the forum. Nice builds. Just a couple of tiny little things you might like to address. Take a little more of your damping material away from the vicinity of the crossovers. They might get hot, you don't want fire. Also, take the damping material away from immediat...

Don't get too excited about the SPL charts, and looking for differences. There's slightly different scales in the 2 charts you mention (number 4 goes to about 110dB, number 10 goes to 120dB), but mostly, the response at various frequencies is pretty much the same. This is because it's not the driver...

I guess the real bonus if utilizing this is that you don't have to build a new set of cabs if you do your homework and discover some content below 40Hz with some recorded material, but remain a bit vigilant about what you're doing. With a 24db/octave LR slope on a HP of 40Hz, you're around -6db at 3...

Thanks Bill,
I wasn't asking for me.
I do think this will generate some interest though, and I'm going to sit back with the popcorn and see how many blown driver reports now turn up.

Seriously though, it was better than I was expecting, I was thinking you might have said 35V for 35Hz HP...

In this thread: https://billfitzmaurice.info/forum/viewtopic.php?f=1&t=25123 Which is discussing T39's with 3012lf drivers, Bill makes the following point: Sorry, but No, there's no further reduction in HP by going from 4 to 8 cabs. You could, but the response corner frequency isn't going down, so y...

Although I've really enjoyed my T39's, I was just thinking about the Tuba 45 for the extra extension at the lower range (below ~40Hz.) I thought that might suit the many more DJ gigs I seem to be getting these days. I was thinking 4 24" wide T45's would probably get me much more output than 4 20" w...

A 12" driver.
The minimum cab width for a 12" driver is 15".
Once the cab width gets to 18" and over, a 15" driver is preferred.
As is usual, drivers are listed in the plans...

If you're worried about weight, forget the lab 12. It will add 14 lbs roughly. As Tom said, basically the same, with it's lower nominal impedance, but the same voltage limit, it has a 1-2dB (at most) improvement in output vs 3012lf. While the lab12 might look to go lower on paper as well, the same h...