What's to chat about?

[jemo1234567890]

[...]

+21 for one cab, subtract 6 for doubling of cabs to two, subtract another 6 for doubling cab count to four, gives me 9dB to be made up with amplification.

Four cabs is 4 watts. 2.83volts/1 watt each. Double that to account for the first 3dB is 8 watts. Double that again for the next 3dB is 16 watts. And double it again for the last 3dB (of 9) is 32watts total Or, only 8 watts/8 volts to each cab to match the output of the 16" cab at full tilt, 378 watts.

That's pretty amazing.

[...]

Again... I find that amazing. It really brings to light the value of small herds of cabs and building as wide as you can transport.

What a GREAT calculation Seth what you could achieve if you go as big as you can. Like "quality instead of quantity" or "go big or go home"
Thats the reason for I plan to build my cabs as wide as possible instead of the previous plan to build many narrow cabs for a higher Vd number.

But I would speed up the calculations like this:
+21 dB (to reach the 122 dB mark) minus 12 dB (for 4 cabs) means you only need +9 dB.
So 10^(9/20) equals a faktor of 2,82.
Means 2,83 V * 2,82 = 7,98 V for each cab if you connect them in parallel (8 Ohm/4 = 2 Ohm) --> ((7,98 V)^2)/2 Ohm = 31,84 W are needed with four 30" wide cabs to reach the output of the 16" cab with 378 W.

... smart ass mode off

[Seth]

What a GREAT calculation Seth what you could achieve if you go as big as you can. Like "quality instead of quantity" or "go big or go home"
Thats the reason for I plan to build my cabs as wide as possible instead of the previous plan to build many narrow cabs for a higher Vd number.

But I would speed up the calculations like this:
+21 dB (to reach the 122 dB mark) minus 12 dB (for 4 cabs) means you only need +9 dB.
So 10^(9/20) equals a faktor of 2,82.
Means 2,83 V * 2,82 = 7,98 V for each cab if you connect them in parallel (8 Ohm/4 = 2 Ohm) --> ((7,98 V)^2)/2 Ohm = 31,84 W are needed with four 30" wide cabs to reach the output of the 16" cab with 378 W.

... smart ass mode off

LOL

I love numbers and math. I see you're a numbers guy too

I like to make things in forum posts as easy to understand as possible for non-numbers people whenever I can... Which is why I took the time to spell it out the way I did.

I appreciate the efficiency and eloquence of your calcs. Nice

And thanks for introducing me to the function of adding dB to the traces. I've been enjoying fiddling with them. Super cool.

[jemo1234567890]

Yeah, as a electrical engineer it's all about math

You're welcome. This way it's so simple to estimate the expected SPL. A pity the dB(max) of the SPL Tool is 140 dB

You gave me an idea to calculate this for all the different widths:


As you can see to reach the SPL(max) of one 16" wide T39 with his voltage limit of 55 V (or 378 W) you only need 42,3 V (or 224 W) for a 24" wide and only 31,75 V (or 126 W) for a 30" wide T39.
That's amazing!
So this way (as Bill always says) you can get the most out of one driver. BUT you have to pay the extra ply LOL

[Seth]

...one 16" wide T39 with his voltage limit of 55 V (or 378 W) you only need 42,3 V (or 224 W) for a 24" wide and only 31,75 V (or 126 W) for a 30" wide T39.

That's amazing!

So this way (as Bill always says) you can get the most out of one driver. BUT you have to pay the extra ply LOL

I like that perspective, Josh.

As long as I can transport it, my personal preference is to have the cab design do as much of the heavy lifting as possible. More wood and air, fewer drivers and less amplification to get to the same output level.

It's too big for me to transport, but to drive your point home, here's a wide 3015LF T48 added to that list.



22.45v (63 Watts) to match the 16" T39 at full boogie, 55v (376w)

Again, having experienced the performance of the single 16" T39 outdoors on the limiter at 55v, the thought of matching that performance, cab count for cab count, with 125 watts or less of amplifier each tickles me a little.

You built two 19" T39's, didn't you? Have you used them outdoors at all? Each, or pair?

[jemo1234567890]

Holy moly Seth,

the 36" wide T48 is really powerful (if you have a huge truck to transport the massive cab). But there shouldn't be any standard doors

Yes I've built two 19" wide T39 but didn't use them outdoors yet because it's winter time you know

Next I will build two Otops8 with melded arrays (cutted last weekend and started to glue them together) so my home setup will be finished.

And for summer my plan is to build four 25,5" wide T39 for outdoor usage and I will measure the effect of the v plate too. I'would like to choose the width for the most efficient sheet usage.

What are you going to build next during the boring corona time?

[Seth]

Holy moly Seth,

the 36" wide T48 is really powerful (if you have a huge truck to transport the massive cab). But there shouldn't be any standard doors

Yes I've built two 19" wide T39 but didn't use them outdoors yet because it's winter time you know

Next I will build two Otops8 with melded arrays (cutted last weekend and started to glue them together) so my home setup will be finished.

And for summer my plan is to build four 25,5" wide T39 for outdoor usage and I will measure the effect of the v plate too. I'would like to choose the width for the most efficient sheet usage.

What are you going to build next during the boring corona time?

Yeah, I'm guessing those that have built the 36" wide T48's have to go through doorways sideways. I don't plan to, but if I ever build any 36" T48's, I think I'd put casters on the side rather than the back, and a hand hold on the top/side with an angle backer in the driver chamber. Wouldn't bother me if it was off center. Just as long as it was functional. I can't wait to hear Ryno's impression of the 36"er he's finishing up.

Waiting for a little better weather, sore back to settle down, and I have a family thing to attend to. So, I'm on project pause for another week or so. However, I'm currently mid build on a pair of Wedgehorn 6 lite's. I also have all the lumber, drivers, and other components ready to go for a 4x Ultralight DR200 Build (actually have enough drivers to build 8, but am going to start with 4 first), and also have drivers and all the lumber already rough cut for 4x 30" T39's. If weather and body are cooperative, I'd like to progress on all 3 projects daily starting mid next week. It's essentially all there and ready to go, just needs assembly.

Beyond what's on the plate already, I'll probably build at least 2 more Wedgehorn 6's, so I have enough for a 4 piece band. Possibly more if they prove to be sufficient for small PA duty too. I'm also considering one or two Jack 12 lite's as well, just because I've started playing bass and have suitable drivers already on the shelf of spare parts.


Back to the sensitivity and cab width discussion, my original plan was to power the subs with 150 watt amp channels. Then my plan swayed and I started to look into powering them with amps capable of producing their 55 volt limit. After this little charts excercize, I'm starting to think 150 watts should be more than sufficient again. I have the amps to cover either solution. I'm kind of excited to test them out firsthand. I'd love to tell the people that ask "are those 18's?" or "how many thousand watts are you running?" that I have 4 12's at 150 watts each. The amps that I have that are 150 watt channels are 8 channel amps, so I'd be able to do 4 subs (2 parallel per channel), 4 tops (2 parallel per channel), and 4 separate monitor leads... a whole 4 piece band gig on one amp. That tickles me a little too.

And now that I think of it... I may wanna do the casters on the sides of the 30" T39's to better navigate doorways. Makes sense.

[Seth]

Good News/Bad News.

Story time.

I had an injury at work about 10 years ago that damaged one knee, which subsequently led to issues with the other knee and my back. Both knees have been replaced in that time with poor to medium results and I had a partial revision about a year ago which made an improvement, but still didn't bring it/them to an expectable level of functionality. I've been pushing and rowing myself through all the processes to get them addressed and satisfactorily fixed once and for all. The whole California workers compensation process is very slow. A month or so ago I was finally able to get approval for total knee revision surgeries on both sides and scheduled the surgery for my right side first. But, the hospitals stopped doing elective surgeries again and pushed the date back 2 weeks, then subsequently cancelled that date (was supposed to be last week). With no anticipated date when they may resume elective surgeries, they left it open ended and did not reschedule at that point. I figured it would be a couple months.

The good new is; I got a call today and they have me scheduled for next Tuesday for my right knee. We're planning to do the left 6 weeks after that, assuming elective surgeries continue. So, I'm excited to get these procedures finally done.

The Bad News is; I don't think I'll be up to any meaningful progress on the speaker projects for 2-3 months. Maybe longer. A little bummed about that. But, it is what it is. We'll see if I can't get all the cabs completed in May, perhaps early June. Might still be able to get some summer use out of them.

[Bruce Weldy]

Well, good luck on the procedures.....

[Tom Smit]

All the best to ya, Seth!

[Seth]

Thanks Bruce. Thanks Tom. It's appreciated. I'm pretty excited and looking forward to getting back to productive and active lifestyle again. Feeling optimistic about it.

[Bryan Cox]

Seth, sorry to hear that, man. I'll probably be in the same boat 10 or so years from now. Military life isn't easy on the joints. Add to that, a farm upbringing and constant manual labor (by choice) my body is all but doomed.

I hope you have a speedy recovery and can get back to status quo. But I imagine in the meantime your brain will have ample opportunity to come up with other ways to mess with Bill's science. Take care!

[jemo1234567890]

Hi Seth,

good luck for the process.
I think your speaker projects will wait until you're recovered

[Grant Bunter]

Get well soon Seth...

[Chris_Allen]

I know a coupe of people who have had their knees rebuilt and the before and after difference is incredible.

[Bryan Cox]

Good news...the AF sent my crew home early. We were able to complete our mission set way before the 12 month deadline and it would've cost the AF bookoo bucks to keep us there unnecessarily. Flew back into Minot on Friday and now trying to switch back to U.S. time.

When I left Turkey it was a bit rainy but the highs were 60s - 70s every day. Gorgeous winter. I get back here and BAM! Check out the picture.

We will be here until October when I retire and head to Albuquerque to take advantage of some lucrative job offers. During that time I'll probably go into full BFM cab production mode. We'll only be in Albuquerque for 5 years maximum and are then headed back to Central Missouri where a friend and I will have a small sound business...mostly for fun. I want to have all the cabs built prior to that so we can hit the ground running.

Anyways, good to be home and I can't wait until I can make some sawdust. Take care, fellas.

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