T60 Limit

Get the lowdown on the down low.
Message
Author
Rich4349
Posts: 647
Joined: Wed Jul 30, 2008 10:18 am
Location: Kankakee, IL

Re: T60 Limit

#31 Post by Rich4349 » Fri Aug 24, 2018 1:44 pm

I'd be curious to try playing a 25 hz sine wave, with the highpass set to 24 and the lowpass set to 26.
2 DR250s, 2 27" Lab15 T-60s, 2 30" Neo Titan 39s, 1 Autotuba...and looking for more!

User avatar
Bill Fitzmaurice
Site Admin
Posts: 26740
Joined: Tue May 02, 2006 5:59 pm

Re: T60 Limit

#32 Post by Bill Fitzmaurice » Fri Aug 24, 2018 2:19 pm

If you do you also have to do an RTA to see what's actually present. Unless the speaker has extremely low THD you'll see significant harmonic content. Assuming equal loudness curves are correct a 50Hz harmonic that's 20dB lower than a 25Hz fundamental will be heard at the same level. That's 10% THD. 10% is the benchmark for acceptable THD in speakers. I'm not convinced the curves are correct, since the playback systems required to have THD at a reasonably inaudible 1% below 30Hz are quite rare.

SethRocksYou
Posts: 264
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: T60 Limit

#33 Post by SethRocksYou » Fri Aug 24, 2018 5:32 pm

My mind got kind of side tracked on the SPL portion of the conversation. And, CoronaOperator, this post is certainly deserving of some attention.
CoronaOperator wrote:
Wed Aug 22, 2018 11:17 pm
We use dual T60's at our club because they only get moved to wax the dance floor. Hauling those beasts around for a mobile rig IMO is ridiculous even for EDM unless you have a warehouse, huge trailer, and lots of young helpers. 4 T45's will not only get you to 30hz, but have more sensitivity at 30hz than the T60's.

25 hz indoors is a lot of fun ... when it happens. Out of the 60 EDM shows we did at our club in the last year, I can count on 1 hand how many tracks the DJ's played that actually dropped that far (and on to 20hz) on a fundamental. Pretty neat experience having the entire club vibrate considering the walls are 18" thick brick but very rarely does anybody have tracks that can dig that deep. Also, I'm sure it was only me, the DJ's, and maybe some staff that went crazy over it. I doubt anyone else even cared, for most people these are social events. If you want that experience outdoors then set up within 100 yards of a train track, not even the pro's attempt 25 hz outdoors, it's just not going to get that visceral experience without a train going by, although a full gravel truck going down the right road (bumpy) can get close.

In the end if it isn't a permanent install and you want to rent out the system then logistics of storage, transportation, lifting it and room to set up the system outweigh that last 5hz. I am personally getting out of the night club business in 2 weeks (after 18 years), the T60's are staying put and I am building T45's to go mobile with. If you need lower for personal listening, then build a THT for home use.
What a great point of view and recommendation. I think you may have changed my future CO. :thumbsup:

Is the night club business like a boat? Where the best 2 days are the day you get in and the day you get out? If so... congratulations.

SethRocksYou
Posts: 264
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: T60 Limit

#34 Post by SethRocksYou » Fri Aug 24, 2018 5:53 pm

Grant Bunter wrote:
Wed Aug 22, 2018 3:11 pm
Seth,
Think it in reverse perhaps.
Just know that the voltage displacement limit is set by Bill without adding the horns impedance, but then having that horn impedance there actually increases driver safety.
The Labs are a bit pesky in that they don't have those lovely round figures like 8 or 4, what we get used to looking at when checking out amplifier specs.

The driver itself in a horn cab doesn't "know" about the extra horn impedance. It simply responds to voltage in line with it's design, and final, parameters, so it makes more sense to set limits based on that.
Here's the part I find confusing... in one portion of the plans it says add 2 ohms for the cab and that's what the amplifier sees (paraphrased). My logic says to me "if the amp is seeing 8 ohms (nominal) then it's not going to flow as much current and ultimately power, as opposed to a situation where the amplifier "sees" any lower impedance at the same voltage." Then later in the plans we're ignoring it. If it's for safety, my opinion is, it should state that as the case. Otherwise, my mind just gets stuck at V x V / Ohms = Watts... and how can the amp and speaker not be in 100% agreement on the matter. LOL

So, I'm following up on what Bill has said, trying to further understand. One of the more helpful links so far... https://www.electricaltechnology.org/20 ... tance.html
Remember also that any given driver has nominal impedance. Nominal impedance is determined at the design stage of the driver. Example: X driver will have an impedance of 8 ohms, be made with a pressed steel basket, have a paper cone blah blah blah.
When they finally built it, it turned out that the impedance wasn't the nominated 8 ohms, but it was meant to be.
Also remember impedance is frequency dependant, so varies.
Yeah, I get that nominal is nominal and impedance varies with frequency. Something's just not clicking upstairs yet. I'll figure it out sooner or later.

User avatar
Tom Smit
Posts: 6714
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: T60 Limit

#35 Post by Tom Smit » Fri Aug 24, 2018 10:28 pm

SethRocksYou wrote:
Fri Aug 24, 2018 5:53 pm
[
So, I'm following up on what Bill has said, trying to further understand. One of the more helpful links so far... https://www.electricaltechnology.org/20 ... tance.html
Well, how about that! I just learned AC resistance/impedance! That article clarified things for me. Thanks SethRocksYou.
TomS

SethRocksYou
Posts: 264
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: T60 Limit

#36 Post by SethRocksYou » Fri Aug 24, 2018 10:37 pm

Bill Fitzmaurice wrote:
Wed Aug 22, 2018 3:37 pm
SethRocksYou wrote:
Wed Aug 22, 2018 1:33 pm
I can hear 25hz just fine
What you're hearing is harmonics of 25Hz...
So, just a random thought on this subject... the harmonics you're talking about are overtones, right? 50hz, 75hz, 100hz, etc. If I'm hearing those frequencies and not the 25hz root frequency, I wonder why I cant hear a darn bit of 15hz? It occurs to me, if the logic is to hold true, I should be hearing 30, 45, and 60hz overtones.

It's not my intention to come off as challenging what you've said. I'd like to discuss it. And I also want to pay you your due respect. Obviously, I'm still trying to wrap my mind around it. Thank you for any schooling to this point and forward Bill.


More listening material for you guys https://youtu.be/vB0Ekcc8e8Y

CoronaOperator
Posts: 1571
Joined: Wed Mar 25, 2009 7:07 pm
Location: Medicine Hat, Alberta, Canada

Re: T60 Limit

#37 Post by CoronaOperator » Fri Aug 24, 2018 11:45 pm

SethRocksYou wrote:
Fri Aug 24, 2018 5:53 pm
Yeah, I get that nominal is nominal and impedance varies with frequency. Something's just not clicking upstairs yet. I'll figure it out sooner or later.
Maybe a picture will help, here is an impedance measurement of my dual Lab12 T60's wired parallel:

Ohms on the left vertical axis, frequency on the horizontal labeled on bottom, impedance plot in blue. You can see how impedance varies wildly with frequency, what you would say is "Nominal" is up to the designer I guess.

http://i769.photobucket.com/albums/xx3 ... g~original

Compare that to the free air impedance of the Lab12 in the chart here:

https://www.parts-express.com/pedocs/sp ... ations.pdf
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

SethRocksYou
Posts: 264
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: T60 Limit

#38 Post by SethRocksYou » Sat Aug 25, 2018 12:35 am

CoronaOperator wrote:
Fri Aug 24, 2018 11:45 pm
SethRocksYou wrote:
Fri Aug 24, 2018 5:53 pm
Yeah, I get that nominal is nominal and impedance varies with frequency. Something's just not clicking upstairs yet. I'll figure it out sooner or later.
Maybe a picture will help, here is an impedance measurement of my dual Lab12 T60's wired parallel:

Ohms on the left vertical axis, frequency on the horizontal labeled on bottom, impedance plot in blue. You can see how impedance varies wildly with frequency, what you would say is "Nominal" is up to the designer I guess.

http://i769.photobucket.com/albums/xx3 ... g~original

Compare that to the free air impedance of the Lab12 in the chart here:

https://www.parts-express.com/pedocs/sp ... ations.pdf
You're awesome! I bet that would help. You don't happen to have a larger, more legible version of your measurements available would you? I see the lines, but can't make out any of the numbers.

User avatar
Tom Smit
Posts: 6714
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: T60 Limit

#39 Post by Tom Smit » Sat Aug 25, 2018 8:10 am

SethRocksYou wrote:
Sat Aug 25, 2018 12:35 am
You're awesome! I bet that would help. You don't happen to have a larger, more legible version of your measurements available would you? I see the lines, but can't make out any of the numbers.
Hold down "control" while scrolling with your mouse, to zoom in or out.
TomS

CoronaOperator
Posts: 1571
Joined: Wed Mar 25, 2009 7:07 pm
Location: Medicine Hat, Alberta, Canada

Re: T60 Limit

#40 Post by CoronaOperator » Sat Aug 25, 2018 8:24 am

It worked on my end but I was logged in to image shack at the time, try this one:

You will have to hit the + sign in the magnifying glass mid top right to enlarge.

http://i769.photobucket.com/albums/xx3 ... ot%205.png

Edit , I tried it on my phone and no suck luck,

Try this one, lower resolution but still legible on my end:
Image
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

Ryan A
Posts: 865
Joined: Thu Mar 01, 2012 11:19 am
Location: Minneapolis, Minnesota

Re: T60 Limit

#41 Post by Ryan A » Sat Aug 25, 2018 11:08 am

Bill Fitzmaurice wrote:
Wed Aug 22, 2018 3:37 pm
SethRocksYou wrote:
Wed Aug 22, 2018 1:33 pm
I can hear 25hz just fine
If I had a dollar....
What you're hearing is harmonics of 25Hz. To know what you're capable of hearing you need a sine wave generator, a speaker with essentially no harmonic distortion, a Z weighted sound meter and an RTA to see what's present. It just so happens that I have all of those. I can play a 25Hz tone at 100Hz outdoors, with no audible harmonics, and not hear a thing. The meter tells me it's there, stuff within 50 feet vibrating like mad tells me it's there, my skin tingling and chest being pounded tell me it's there, but if not for that you wouldn't know there was any sound. Having below 30Hz capability is nice indoors for HT, where you literally feel the room pressurization, but where music is concerned it's a capability you don't need and can't use.
Is it possible you’ve lost some hearing in your age, Bill? I can also hear 20 hz just fine and I’m not talking about a “feeling” or a “vibration”, the actual fundamental with my eardrum, especially but not limited to with good earbuds.

Ryan A
Posts: 865
Joined: Thu Mar 01, 2012 11:19 am
Location: Minneapolis, Minnesota

Re: T60 Limit

#42 Post by Ryan A » Sat Aug 25, 2018 11:10 am

SethRocksYou wrote:
Fri Aug 24, 2018 10:37 pm
Bill Fitzmaurice wrote:
Wed Aug 22, 2018 3:37 pm
SethRocksYou wrote:
Wed Aug 22, 2018 1:33 pm
I can hear 25hz just fine
What you're hearing is harmonics of 25Hz...
So, just a random thought on this subject... the harmonics you're talking about are overtones, right? 50hz, 75hz, 100hz, etc. If I'm hearing those frequencies and not the 25hz root frequency, I wonder why I cant hear a darn bit of 15hz? It occurs to me, if the logic is to hold true, I should be hearing 30, 45, and 60hz overtones.

It's not my intention to come off as challenging what you've said. I'd like to discuss it. And I also want to pay you your due respect. Obviously, I'm still trying to wrap my mind around it. Thank you for any schooling to this point and forward Bill.


More listening material for you guys https://youtu.be/vB0Ekcc8e8Y
Good point you make here.

I agree with most of what was said in this thread. However regarding hearing of 20-25 hz, it’s completely normal (if you still have all your hearing left) to hear those frequencies. There is a big difference between 25 and 50 hz for sure. Good earbuds for example do work at 20 hz (and with very low distortion at that) regardless of the sonic wavelength even though they are but a few mm or cm from
your eardrums.

In fact to our detriment, try playing music that has sub 40 hz content with a T39 high passed at 45 and all you’ll hear is harmonics of course, because you’ve cut off the fundamental and it sounds like garbage.

Better to have the extension if you think you’ll need it and are willing to carry the cabs around in my opinion. EDM does not sound particularly good on T39’s but if you don’t know what is suppose to sound like, you might not know the difference. That being said, if I had to be mobile, I’d take t45’s over t60’s I think.

SethRocksYou
Posts: 264
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: T60 Limit

#43 Post by SethRocksYou » Sat Aug 25, 2018 11:31 am

Tom Smit wrote:
Fri Aug 24, 2018 10:28 pm
Well, how about that! I just learned AC resistance/impedance! That article clarified things for me. Thanks SethRocksYou.
Glad you got something out of that too Tom. I had no idea.

Also, thanks for the zoom tip. I have always used a different method and the one you mentioned is quite handy.

BTW, you can just call me Seth if ya like :thumbsup:

Bruce Weldy
Posts: 6644
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: T60 Limit

#44 Post by Bruce Weldy » Sat Aug 25, 2018 11:38 am

The DJ world is so much different than where I work. When I'm mixing a band on a system other than mine, the first thing I do is to dump everything below 40hz. Otherwise, there is just a lot of rumbling crap going on that muddies up the bottom end.

I just don't see (figure of speech) anything below that as being very musical..... does it create an effect on your body? Sure, but at the expense of a tight, punchy kick and bass......not a trade off I'd ever make in the live sound world. But, as I said - we live in different worlds.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

SethRocksYou
Posts: 264
Joined: Thu Sep 10, 2009 8:06 pm
Location: Sacramento, California, USA
Contact:

Re: T60 Limit

#45 Post by SethRocksYou » Sat Aug 25, 2018 11:42 am

CoronaOperator wrote:
Sat Aug 25, 2018 8:24 am
Try this one, lower resolution but still legible on my end:
Image
Yeah, later last night I looked at it again. I blew it up real big, squinted, turned my head from side to side, thought real hard, and deduced some figures with my questionable logic. Darnit if photo bucket isn't pushing themselves out of business. Hahaha

Anyway, I'm quite surprised to see the troughs within the bandpass right there at 3 Ohms. Not what I expected to see. Thanks for that bit of visual aid. It's much appreciated.

What did you use to get those measurements?

Locked