New subwoofer Stack

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Grant Bunter
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Re: New subwoofer Stack

#16 Post by Grant Bunter »

If you want a different method:
Take the average response based on cab width from the SPL charts graph (let's stick with Seth's 102dB), and since you're using the 3015LF add 26dB for max power (which happens to be 450W/8ohms). So max power 1 cab = 128dB
Add 3dB if you use a V plate.
Add 6dB for each doubling of cabs (1 to 2, 2 to 4 etc).
All that gives yo theoretical max SPL.

Now subtract 6 dB for each doubling of distance. 1 to 2, 2 to 4, 4 to 8, 8 to 16, 16 to 32 etc.
Since we start with charts that are 1W/1 meter, I always set up so I'm at some doubling of distance metric. (1 meter is 3'3") so 10 metres is not a doubling. I measure at 16 or 32 meters.

Why have I written this?
Well, you don't run cabs to max power from the get go all the time. If you do, you haven't got enough subs.
All you really know now is max output/SPL of your subs.

So, the super fast way to work out actual SPL at 1 meter is, measure SPL, ideally at some metric doubling of distance and add 6dB for each doubling...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

jakkle21
Posts: 28
Joined: Sat Oct 30, 2021 1:47 pm
Location: Flagstaff AZ

Re: New subwoofer Stack

#17 Post by jakkle21 »

Thank you for the all the math.
*Pop quiz answers
So I'm assuming the 24" cab, at 40hz has 97db of sensitivity, if I'm reading the graph right. Plus 26db for the 100w and the 2x doubling to 400w, or 123db total with the last 50w being fairly negligable.
the 36" hitting 122db with the first 100w and 125db at 200.
With the second "pop quiz" question. If I did my math correct, 8 24"s would be 1db louder than 4x36"s
I will play with Grants numbers some as well

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Seth
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Re: New subwoofer Stack

#18 Post by Seth »

Perfect!
So I'm assuming the 24" cab, at 40hz has 97db of sensitivity, if I'm reading the graph right. Plus 26db for the 100w and the 2x doubling to 400w, or 123db total with the last 50w being fairly negligable.
the 36" hitting 122db with the first 100w and 125db at 200.
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8 24"s would be 1db louder than 4x36"s
Screenshot (205).png
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I will play with Grants numbers some as well
Grant's figures and methodology is solid too. It's good to have a couple different perspectives, a couple different ways to approach a thought process, so I'm glad he took the time to share his. One may speak to you or relate better to the way your mind works more than the other. They're essentially the same thing, though. Use whichever :thumbsup:


So, now you have the tools to compare any cab that has a 1w/1M sensitivity trace. With an inexpensive dB meter or even a free cell phone app (close enough for this simple stuff. Make sure it's dBC and not dBA, some apps offer the choice of either), you can also measure what you're currently using and get an idea what you may gain with a Tuba or Titan. Play a 40Hz sinewave through your system with the speaker disconnected, measure with a digital multimeter, and adjust the volume until the amplifier output voltage reads as close to 2.83v as possible. Plug the speaker in and use the dB meter, laying on the ground at 39" from your sub (use just one sub), and measure the output. Add 3 dB to whatever the reading is (dBC is down 3dB from dBZ at 40Hz) and that's your subs 40Hz sensitivity (assuming they're 8Ω drivers. If they're 4Ω drivers, set the voltage to 2.0v). Now turn up the volume until the meter reads 99. That will be how loud to expect a single 36" T48 to be on 2.83v. I'm gonna take a wild guess and say you're probably gonna get somewhere around 85dB with what you have now. Could be wrong though. It's been known to happen from time to time. :)


Here's the different decibel scales/weightings...
Image
A meter that reads dBZ would be ideal for audio work. However, for some reason unknown to me, they're rare and expensive. A meter that reads in dBC is close enough for amateur level stuff.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bill Fitzmaurice
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Re: New subwoofer Stack

#19 Post by Bill Fitzmaurice »

Z meters cost more due to the need for a mic that goes to 10Hz.

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Seth
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Re: New subwoofer Stack

#20 Post by Seth »

I can see that being the case for laboratory grade equipment. But, it seems like it would be fairly simple and inexpensive to electronically calibrate a dBZ curve (no curve) into a unit, like they already do with dBA and dBC meters. Even if it didn't go all the way down to 10Hz. Maybe I should call China and have some made. It would be the only one available without a sticker shock for the whole of the audio community.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

Grant Bunter
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Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
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Re: New subwoofer Stack

#21 Post by Grant Bunter »

Seth wrote: Tue Aug 23, 2022 9:31 am I can see that being the case for laboratory grade equipment. But, it seems like it would be fairly simple and inexpensive to electronically calibrate a dBZ curve (no curve) into a unit, like they already do with dBA and dBC meters. Even if it didn't go all the way down to 10Hz. Maybe I should call China and have some made. It would be the only one available without a sticker shock for the whole of the audio community.
And, tada, such a unit already exists.
The DEQ 2496 has the option to turn off weighting when using it IIRC.
It was so long ago I found it, I can't actually recall if it was the DEQ (I think so because you need to use the DEQ to RTA), but I'm pretty sure that's it. Delve deep in to the manual and menus to find it if you have one.
I set mine to off because I wanted to know actual SPL at the measuring point, not the reading I got with weighting and then tying to calculate on the fly. Already enough useless junk in my memory...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Seth
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Re: New subwoofer Stack

#22 Post by Seth »

Grant Bunter wrote: Tue Aug 23, 2022 4:53 pm And, tada, such a unit already exists.
The DEQ 2496 has the option to turn off weighting when using it IIRC.
It was so long ago I found it, I can't actually recall if it was the DEQ (I think so because you need to use the DEQ to RTA), but I'm pretty sure that's it. Delve deep in to the manual and menus to find it if you have one.
I set mine to off because I wanted to know actual SPL at the measuring point, not the reading I got with weighting and then tying to calculate on the fly. Already enough useless junk in my memory...
I do recall the setting you're talking about. But, I don't recall ever seeing the SPL Meter function. A quick search of the manual indicates you are absolutely right, bottom left of page 14. :thumbsup:

Due to the supply shortage, I recently sold both, my DEQ2496 and DCX2496 on ebay for $350 each. (silly people) All my amps have integrated DSP with appropriate brick wall limiting, so I had very little need for them anymore. The feature I'll miss most is the feedback destroyer, which is just about the only thing my amps DSP won't do. I'll just have to be ultra diligent in thoroughly ringing everything out.

Still it would be nice to have a handy little standalone handheld unit that measures in dBZ. The one I have (same one I posted a link to) reads in dBC and is fine for what I use it for, mostly level matching subs and tops. So, it doesn't really matter what it reads in. Still though...

I'd buy one
1279227758_SCOSCHE.jpg
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Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

jakkle21
Posts: 28
Joined: Sat Oct 30, 2021 1:47 pm
Location: Flagstaff AZ

Re: New subwoofer Stack

#23 Post by jakkle21 »

A couple of weeks ago, I got to run my current setup for our groups largest annual event.
I was able to run one of the Macro-tech 2400s full blast into my Walmart subs and had almost enough bass, but I was definitely hitting the limit of what they could do. I had plenty of mains though, sounded nice and even all throughout the dancefloor and party area.
After the event I decided I would start building 2 of the T48s while saving up for the speakers, then I saw NookPooch's posting, selling his old speakers and couldn't pass them up, so they are in the mail right now and I'm saving up for the plywood to build 4 boxes! That's much quicker than I was anticipating having that many.
For my weekly event, I only have to haul exipment about 50 feet, would it make sense to run all 4 T48s off one amp, even if I'm not coming anywhere close to their limits? A little extra extension for the extra work of moving them?
Most weeks I'm not going to want or need more than one amps worth of bass, but with the extra cabs just sitting there...

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Seth
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Re: New subwoofer Stack

#24 Post by Seth »

jakkle21 wrote: Mon Sep 26, 2022 7:46 pm For my weekly event, I only have to haul equipment about 50 feet, would it make sense to run all 4 T48s off one amp, even if I'm not coming anywhere close to their limits? A little extra extension for the extra work of moving them?
Most weeks I'm not going to want or need more than one amps worth of bass, but with the extra cabs just sitting there...
Will it be required? Not likely. Is it worth doing anyway? Yes, absolutely. It's also worth stacking and v-plating them... Especially if you're running off generator power. Plus, every time you stack and v-plate them is experience gained. Way better, IMO, to start off with good, intentional, and purposeful habits.

With 4 cabs, each individual cab will run at ¼ power, per cab, compared to using only 2 cabs for any given SPL. Doubling your cab count cuts the total power needed in half. So, while you're amp will be loaded down to 4Ω per channel, it will ultimately be running half as hard for 4 subs to create the same SPL as 2.

Although, a six foot tall, eight and a half foot wide stack of subs might look like clown shoes at a small event. Or, it could look like the most awesome thing anyone's ever seen, depending on perspective.

You may consider wearing a diaper for initial setup and testing.

Please keep us posted with your progress.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

jakkle21
Posts: 28
Joined: Sat Oct 30, 2021 1:47 pm
Location: Flagstaff AZ

Re: New subwoofer Stack

#25 Post by jakkle21 »

I haven't had much time to work on this for a while, other than trying to figuring out how much plywood I need to buy.
As I get into building, should I update this thread or start a new one in the build section?
Thank you everyone for your knowledge and input.

ACUA
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Location: Tucson Arizona

Re: New subwoofer Stack

#26 Post by ACUA »

Plywood prices have come back down in my area which is nice to see. If I could do my tuba45 cabs over again I would rather titan48s. Three inches taller but way more output same low extension. What part of Arizona you located in? I’m in Tucson.
Advanced Concepts Underground Audio

jakkle21
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Joined: Sat Oct 30, 2021 1:47 pm
Location: Flagstaff AZ

Re: New subwoofer Stack

#27 Post by jakkle21 »

Hi ACUA,
Thank you for your input in the tube vs titan. Plywood is getting more affordable here as well, I'm in Flagstaff.
I'm finalizing my panel layout sheets, and will easily be able to get the first 2 cabs out of 5 sheets. Now I just have to call around and get prices.

Grant Bunter
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Re: New subwoofer Stack

#28 Post by Grant Bunter »

jakkle21 wrote: Sat Nov 05, 2022 2:03 pm As I get into building, should I update this thread or start a new one in the build section?
Make a new build thread.
That way, you can ask questions (preferably before you may make a mistake) and document your progress with pics.
Also, most people here will tend to only give answers and encouragement in build threads, other threads tend to wander more at times...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" KL3010LF , 2 x 28" 3012LF.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Seth
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Location: Sacramento, California, USA
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Re: New subwoofer Stack

#29 Post by Seth »

Have any of you guys ever eaten squirrel?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

User avatar
Bill Fitzmaurice
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Posts: 28619
Joined: Tue May 02, 2006 5:59 pm

Re: New subwoofer Stack

#30 Post by Bill Fitzmaurice »

Road kill stew? Pass the salt, Jethro.

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