BillFitzmaurice.info

I began wiring up the flat tweeter array last night in the series/parallel form outlined in the plans. I'm using 24ga wire that I had on hand. I tried gluing them together with super glue, but that didn't hold. I then found some airplane glue, but that didn't hold either. I will be using some epoxy this evening. I have also been breaking in the driver with a 30Hz sine wave at about 8 volts. I let it run for about 20 hours.

How should I mount the crossover inside the cab? Since it is already on the metal board, is it okay to just glue to the inside? Or should I mount it to a piece of 1/4" plywood first?

I'm surprised that airplane glue didn't work. Ideally, you want to use ABS Cement, but airplane glue should work. Are you using a glue-up jig? Check my OTop build thread (link in sig) for pics of array glue up jigs.

The jig I'm using, since it is a simple flat array, is just aligning the edges of the tweeters using a 2' level. I'd say I need to sand/scrape off the old glue (super glue, and now airplane glue) better.

miramadar wrote: I tried gluing them together with super glue, but that didn't hold. I then found some airplane glue, but that didn't hold either. I will be using some epoxy this evening.

Follow the plans: Glue the first pair together with model airplane glue, using the jig to align them, holding them for a few minutes until the glue sets. Then add tweeters to the array one at a time. Be sure to use the tweeters trimmed one side only at the top and bottom of the array, leaving the full original mounting flange in place at the top and bottom of the array. After the initial glue-up seal the joints in the back of the array with a few coats of PVC pipe cement, applying enough to insure a solid array.

Trust the plans; you NEED to use the jig to properly glue up the tweets. Laying them flat on a piece of paper and lining them up w/a ruler will not work. AND, plan on multiple coats of adhesive on both sides. The stuff dries so fast that you can put a few layers of glue on both sides over a typical 8-hour work day. That was my experience with 2 full melded and 2 full straight arrays for my OTops, anyway.

Trust the plans; you NEED to use the jig to properly glue up the tweets. Laying them flat on a piece of paper and lining them up w/a ruler will not work. AND, plan on multiple coats of adhesive on both sides. The stuff dries so fast that you can put a few layers of glue on both sides over a typical 8-hour work day. That was my experience with 2 full melded and 2 full straight arrays for my OTops, anyway.

OK...I guess I'm confused. For the 6-tweeter flat array (which is the one I'm building), the plans simply say to "Glue them together, edge to edge...". The 8-tweeter array (which I am NOT building) says to cut the upper and lower frames except for the uppermost and lowermost frames and then glue. My interpretation of this is that, for the 6-tweeter flat array, that I don't cut away any of the frames and just glue them edge to edge. From there, I assumed I would just screw them to the 1" plywood mounts through the existing screw holes in the 4 corners of each tweeter.

As far as a "jig" goes, the only reference in the plan is for the melded array, which I'm not making at this time. Am I not understanding the plans correctly here?

I don't have the Jack plans, so I can't help with interpreting the instructions for the arrays. Others will chime in though.

Sorry I wasn't clearer on the jig comment. What I meant was to build a jig like this, so that the tweets lay perfectly flat and you can securely butt them up against each other. This is just 4 strips of wood nailed together.



Another shot of the straight array gluing jig along with the jig for the melded arrays.

Question...exactly how should the woofer be attached to the woofer spacer? The plans use the term "attachment screws" and say that "lock washers are a must". If you look closely at the pic I uploaded of the driver spacer installed, you'll see that I have it screwed into the baffle with plain 1.25" drywall screws. These screws are located as to line up exactly with the mounting holes in the driver frame. My plan was to just use these same drywall screws to attach the driver to the spacer. But I'm not sure that's how it's supposed to be done.

miramadar wrote:Question...exactly how should the woofer be attached to the woofer spacer? The plans use the term "attachment screws" and say that "lock washers are a must". If you look closely at the pic I uploaded of the driver spacer installed, you'll see that I have it screwed into the baffle with plain 1.25" drywall screws. These screws are located as to line up exactly with the mounting holes in the driver frame. My plan was to just use these same drywall screws to attach the driver to the spacer. But I'm not sure that's how it's supposed to be done.

The spacer must be glued to the baffle, then the driver is mounted to the spacer. Use recex screws for the driver instead of drywall screws. They have a flat bottom on the head and work better with lock washers.

http://www.speakerhardware.com/recex-he ... 1-12x8.php

I put the finishing touches on this cabinet last night. I've already played 1 show with it as a bass cabinet and did a couple of outdoor DJ gigs with it. Here are a few pics...
All told, I've got less than $500 in it. I ended up priming the entire outside of the cabinet. I coated the top, bottom, sides and back with roll-on bed liner and just spray painted the front of the speaker with flat black spray paint. The bed liner is some tough stuff, but not the easiest stuff in the world to apply. Nonetheless, I got a usable, durable finish.

As you'll see from the 3rd image, I have parallel speakon input jacks and a DPDT switch for turning off/turning down the tweeters. I'm really glad I put that on there as I can turn the tweets off when used as a bass cabinet and turn them on when used as PA. Very handy.

I went through a process for tweaking the EQ of the cabinet last night, but I'm not sure I did it correctly. On my iPhone, I downloaded a decibel meter app. Probably not the best tool for measuring dB's, but it's all I have. Anyway, I placed the phone about 3 feet in front of the speaker and used a sine wave tone generator, run through my 31-band EQ and power amp, to generate the tones through the cabinet. I set the frequency on the generator to the frequency of the different sliders on my EQ. Below 200Hz, the cabinet was putting out something around 75 dB. Above 200Hz, it went up to 103 dB and remained around that level, so I made that my target dB. I couldn't turn up the frequencies below 200Hz enough to get to 103 dB, but that's to be expected, I guess. I ended up having to cut frequencies between 315Hz and 800Hz and boost frequencies at 1.6KHz and 6.3KHz to get to 103 dB. Here's a picture of what my EQ ended up looking like:
Did I do this EQ test correctly?

Before I did the test, I ran some music through the speaker to test the newly-installed DPDT switch. The switch works by the way. Anyway, the music sounded like EQing was needed badly, which made me decide to do this test. Once I set the EQ, I played some music through it, with which I was very familiar, and it sounded great...though I did have to pull back a little on the frequencies between 40Hz and 80Hz (they were dimed).

Another observation...when I was testing the effectiveness of the DPDT switch, I ran a 5kHz tone through the cabinet. The switch was in the "off" position and I could hear the tone. I immediately thought that I had wired something up wrong. I flipped the switch to "full on" and the tone became much louder and piercing. I was a little puzzled. So I cracked the cabinet open and unhooked the woofer. I did the test again and with the switch in the "off" position, no tone. So, some 5kHz tone was being generated by the woofer, albeit a relatively small amount. Is this normal?

miramadar wrote: I couldn't turn up the frequencies below 200Hz enough to get to 103 dB, but that's to be expected, I guess. I ended up having to cut frequencies between 315Hz and 800Hz and boost frequencies at 1.6KHz and 6.3KHz to get to 103 dB.

You don't boost to the maximum SPL, you boost and cut to the average SPL. None should be dimed, in either direction.

So, some 5kHz tone was being generated by the woofer, albeit a relatively small amount. Is this normal?

Filters are not brickwall. The woofer filter is second order at 2kHz, so at 5kHz the signal will be down roughly 15dB.

You don't boost to the maximum SPL, you boost and cut to the average SPL. None should be dimed, in either direction.

Thanks for the advice. So, I should reset my EQ to flat, take SPL readings at each frequency, and the average of those readings will be my target SPL for each frequency? Also, how loud should my amp be when doing a test like this? I was in the 100dB range last night (at 3 ft. away), and my amp was on about 30%. I was inside, so frequencies were bouncing off walls like crazy. Should this test be done outside?