BillFitzmaurice.info

Raining now in Northern California, so no chips flying, yet.

Previously built Bill's plywood cutting table and some cutting guides before the rain. Am building outside, no garage or basement. I have 4 SLA Pro's to build by March 1.

Most parts here, some on backorder. 2 sheets of Latvian Birch ready.
Used the time to do a lot of reading on the boards, run through the tweeters for loudness using capacitance function on my multimeter. (http://www.billfitzmaurice.info/forum/v ... 18&t=17047), and check polarity (my vid here: https://www.youtube.com/watch?v=NcgieJ5IWFQ) I used the wood clamp to hold the tweets, driver on right was middle loudness of the 30, ~136 uF. Used Audacity to push white noise and ProTools meters to read.

Out of 30 goldwoods, 2 were hot and 5 were low. At 50 I have some hearing loss, especially higher, and would not trust my ears, yet when checking polarity, could really hear/see the low ones. One of the first things I did was switch the polarity to see/hear the effect. The sound changed, not sure if it was quieter or not, but on ProTools it showed fully canceled! But when I made the video afterwards, the cancellation wouldn't repeat, the volume just did not go up and remained like only the one tweet was connected. So my initial finding is unverified! sigh.
Busy tomorrow, but should make chips Monday!

Good technique. I'm always interested in the SLA Pros, it's one of the designs I'd really like to hear.

The differences are readily apparent on 1016's. I've tested so many now I do it all by ear. There are 3 versions, low, avg, and high. The ones with lows emphasized are best for arrays, but they're fairly rare. Too infrequent for complete arrays. I do a mix of the avg and lows. The high ones fall into two categories, most are perfectly fine, just a shade higher, and a little more spl than any others, and some just suck, all top end. Those go in the scrap. Although sometimes if you pull them apart you'll find a blob of solder or something else causing it.

Reading through the plans again, I'm thinking about using 3/4 inch Appleply for the front baffles, just to stiffen them up a bit. The rest of the cabs will be 1/2 birch.

Any thoughts or insights?

Thanks!

David

If you want to add the additional weight, that's entirely your option but it is really unnecessary.

Adding additional weight to the baffle will shift the centre of gravity forward for the top hat, so you would probably have to add 18mm to the back as well. Honestly, you don't need it!

If you want to add the additional weight, that's entirely your option but it is really unnecessary.

Adding additional weight to the baffle will shift the centre of gravity forward for the top hat, so you would probably have to add 18mm to the back as well. Honestly, you don't need it!

Thanks Chris, you are right. Stick to the plans! Okay, chips ahead!

David

The plans are the plans for a reason! At least that is what I always tell contractors in my day gig.

lowsound

iamlowsound wrote:The plans are the plans for a reason! At least that is what I always tell contractors in my day gig.

lowsound

I am concerned on another note, though. The latvian birch I have is scant, 15/32, not a true 1/2 inch. I am planning on putting top hat stands for pole mounting the speakers and I would like to recess mount them. That means removing another 3/32 inch of stock and now I am just wondering if 3/4 on the bottom plate makes sense? I am open to suggestions, but would appreciate freedback from those who have recessed mounted top-hats in 15/32 and if they have had any issues.

thanks! David

1/2 ply is almost always 15/32

Rather than making the entire bottom panel 3/4, most people here who recess top hats simply add a slightly larger than needed square reinforcing plate in the appropriate place. This allows for the recess, but still provides ample "meat" for screw bite...

As a side question, what is the deepest hat you can get? I always feel that the deeper they are, the more stability there is with the speaker is on the pole.

Chris_Allen wrote:As a side question, what is the deepest hat you can get? I always feel that the deeper they are, the more stability there is with the speaker is on the pole.

3 inches Chris, already purchased.

Grant Bunter wrote:Rather than making the entire bottom panel 3/4, most people here who recess top hats simply add a slightly larger than needed square reinforcing plate in the appropriate place. This allows for the recess, but still provides ample "meat" for screw bite...

Grant, I thought about that, but it just seems easier to me to use the 3/4 in the first place and be done with it. I see the PL Premium is good for both wood and metal, so am thinking the PL will be at work along with the screws. But two 1/2 pieces is more "meat" than 3/4 inch.

Thank you for the quick responses, great community...

David

From an aesthetic perspective, you should consider how the SLA will look from the front. It will have a 12mm 'border' top and sides and an 18mm 'border' at the bottom. That's the kind of thing that would irritate me every time I looked at my cabs!

Grant Bunter wrote:Rather than making the entire bottom panel 3/4, most people here who recess top hats simply add a slightly larger than needed square reinforcing plate in the appropriate place. This allows for the recess, but still provides ample "meat" for screw bite...

See 3rd pic in this post, that's what I did.
http://billfitzmaurice.info/forum/viewt ... 69#p233369
Hardly any extra work, and I'm with Chris: it is so much cleaner looking than having one panel thicker in an otherwise neat cab.

Thanks for bringing up the plaster lath idea, David. I will have to see if I can find that locally.

Nothing big, just glued and nailed the back braces to the center braces...

The PL is a trip, just keeps oozing out.

Will cut tops and bottoms tomorrow if the sun shines, drill and cut out tweets and alpha drivers. Larger assembly Monday?

Chris, the aesthetics don't bother me, but the I will think I will go with that solution. Anton, nice job of the router work. I'm going to have a friend help with that--don't own one and they scare me to death. I've been lurking on your build... looks sharp!

Sine143, the lumberyard didn't say scant, I'm going to ask more questions next time. It was the first time dealing with that high end place, but what gorgeous lumber!

Time to go scrape glue...

david