Ultimax UM15 vs PA 18 inch or 21 inch - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Old 02-11-2020, 05:10 PM - Thread Starter
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Ultimax UM15 vs PA 18 inch or 21 inch

Hi,

How does an Ultimax 15" in a sealed 6cu.ft. compares to a bigger PA driver like the RCF L18P300 or a Eighteen Sound 21NLW9001 in the same enclosure (could be vented)??

I have modeled them in WinISD and the Ultimax wins below 20hz whereas the bigger PA drivers have a ton more output over 30hz (much more efficient).

The thing is that use my drivers for movie watching, so performance below 20hz is desired. One thing in favor of the PA drivers is that I can get them locally and It would be possible to eventually upgrade to 4 drivers (now I own 2x Ultimax 15" but importing 2x more will cost me the same or more than buying two 18Sound 21NLW9001, and i would be paying half in shipping and duties).

I am not looking for 110+db performance, just good ol' bass and some chest kick at moderate levels. So, am I missing something that WinISD is not telling me? I am not accounting to room gain an alike.

Looking forward to you enlightenment, as it seems PA 21" drivers are very popular here.

Cheers!

Last edited by marto2009; 02-11-2020 at 05:14 PM.
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post #2 of 7 Old 02-11-2020, 09:01 PM
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I would solve the >30hz range first with the local PA woofers (21's etc)
Power it with a nx3000d or 6kD

Because 90% of bass is 30hz and above.
It's where all the explosions and dance/pop/rock/country/metal/dubstep/rap music is at.

<30hz is for earthquakes, pipe organs, BassILoveU, and other such extreme basshead music.

It's much more rare to find 1-19hz content, and much more infrequent when it occurs. For 3 hour movie, you might not get any, or it might be only once or twice etc etc.

It also takes a lot of power, cone-area, box space, and amplification/breakers. Every octave deeper gets 4x more expensive.
1hz is 4x more expensive than 2hz
2hz is 4x more expensive than 4hz
4hz is 4x more expensive than 8hz
8hz is 4x more expensive than 16hz
16hz is 4x more expensive than 32hz.

Then save up for a pair of sealed SI-24's and a FP14k + miniDSP to solve the infrasonics (or not really solve it but... vastly improve it.)

I would not bother with subwoofers smaller than 18's, unless there is an extreme space or budget constraint; they just don't have enough displacement.

I can barely hear the 6 UM-15's in my fronts, even when powered with 12kW
they simply can't keep up with the other 23 18's/21's/24's in my system (powered with even-more watts)

You wanna hear a GoPro compressing and struggling to comprehend the bass it is being subjected to? Here ya go!
Like 20hz, at full dynamic range. LOL!
Heck, more like full swings of 10-300hz or whatever...

My average playback is roughly ~15db above THX (with peaks into whatever...)
No audible clipping or distortion in-person.
The amps are still at 5-10% output here. The cone excursion is about the same.
Barely even idling, yet still scalping your face. (As it should be! )

Heck, even this vid, which is 1hz. That's only 0-25% excursion still. (It goes louder... )
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Last edited by BassThatHz; 02-15-2020 at 09:30 AM.
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post #3 of 7 Old 02-12-2020, 06:39 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
I would solve the >30hz range first with the local PA woofers (21's etc)
Power it with a nx3000d or 6kD

Because 90% of bass is 30hz and above.
It's where all the explosions and dance/pop/rock/country/metal/dubstep/rap music is at.

<30hz is for earthquakes, pipe organs, BassILoveU, and other such extreme basshead music.

It's much more rare to find 1-19hz content, and much more infrequent when it occurs. For 3 hour movie, you might not get any, or it might be only once or twice etc etc.

It also takes a lot power cone-area, box space, and amplification/breakers. Every octave deeper gets 4x more expensive.
1hz is 4x more expensive than 2hz
2hz is 4x more expensive than 4hz
4hz is 4x more expensive than 8hz
8hz is 4x more expensive than 16hz
16hz is 4x more expensive than 32hz.

Then save up for a pair of sealed SI-24's and a FP14k + miniDSP to solve the infrasonics (or not really solve it but... vastly improve it.)

I would not bother with subwoofers smaller than 18's, unless there is an extreme space or budget constraint; they just don't have enough displacement.

I can barely hear the 6 UM-15's in my fronts, even when powered with 12kW
they simply can't keep up with the other 23 18's/21's/24's in my system (powered with even-more watts)

You wanna hear a GoPro compressing and struggling to comprehend the bass it is being subjected to? Here ya go!
Like 20hz, at full dynamic range. LOL!
https://www.youtube.com/watch?v=0nxMhsEExW0
Heck, more like full swings of 10-300hz or whatever...

My average playback is roughly ~15db above THX (with peaks into whatever...)
No audible clipping or distortion in-person.
The amps are still at 5-10% output here. The cone excursion is about the same.
Barely even idling, yet still scalping your face. (As it should be! )

https://www.youtube.com/watch?v=9gEINAR_emQ
Heck, even this vid, which is 1hz. That's only 0-25% excursion still. (It goes louder... )
Thanks for your reply!

With all due respect, it seems that your opinion on big subwoofers is biased hehehe.

Jokes aside, awesome equipment!!

If i understand correctly, you would recommend to jump on the big PA drivers to get a good performance at 30hz and over and eventually solve the infrasonics. But i have questions...

-. why not leave the UM15 for <30hz with a LPF and above that the big PA drivers take over up to 80hz. Integration with all sealed enclosures should not be that "impossible".
-. 4x+ 18" PA drivers with performance down to 30hz, should offer some good output below that when considering room gain? Again, I am not aiming to 110+db.-

Also... money and space is always constrained, so "best bang for your buck" is what I am looking for.

Thanks again!

Cheers
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post #4 of 7 Old 02-13-2020, 12:24 AM
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Ported or horned undergoes a 180degree phase shift at tuning (or some other degree LOL!), which makes them a lot more difficult to integrate without a 2-way crossover at that tuning frequency.

Sealed and IB doesn't have this massive phase shift, and by the time you hit 30hz you are almost at the null-free zone for small and medium sized rooms. Bass can't null much if the quarter wave is larger than the room, so that helps...

Best bang depends on where you live, how much space and budget you got, WAF etc.
Too many variables to quantify without us being you.

I wouldn't "depend" on room-gain too much. Maybe you luck-out, and maybe not.

I can say though, that the larger the bandwidth of the subwoofers, the more power it will consume, and the distortion and heat will be generated. Stretch the bandwidth too much and you can even suffer mid-bass SPL drops and such.

Basically: a 1hz ported sub is the same thing as a sealed sub. (That's just way too much bandwidth.)
There are practical limits.

On the other extreme, adding unnecessary LPF's will cause the woofer's potential to go unused. (Try it, you'll see.)

Dual 21's at 10ft away with a few hundred watts going to each, should be able to reach 110db. (Box-model it.)

Quote:
Originally Posted by marto2009 View Post
I am not aiming to 110+db
I've heard many smokers say "this will be be their last cigarette" too, and the proceed to smoke 9000 packs a day.
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post #5 of 7 Old 02-13-2020, 10:07 PM
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Quote:
Originally Posted by marto2009 View Post
[snip]......
Again, I am not aiming to 110+db.-
Clearly... you are not familiar with this bunch of bassheads.... 110Db is the volume @ 10Hz around these parts....
"Reasonable" systems are down the hall..... 2nd door on the left.....


Juju
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post #6 of 7 Old 02-14-2020, 11:32 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
Ported or horned undergoes a 180degree phase shift at tuning (or some other degree LOL!), which makes them a lot more difficult to integrate without a 2-way crossover at that tuning frequency.

Sealed and IB doesn't have this massive phase shift, and by the time you hit 30hz you are almost at the null-free zone for small and medium sized rooms. Bass can't null much if the quarter wave is larger than the room, so that helps...

Best bang depends on where you live, how much space and budget you got, WAF etc.
Too many variables to quantify without us being you.

I wouldn't "depend" on room-gain too much. Maybe you luck-out, and maybe not.

I can say though, that the larger the bandwidth of the subwoofers, the more power it will consumed, and the distortion and heat will be generated. Stretch the bandwidth too much and you can even suffer mid-bass SPL drops and such.

Basically: a 1hz ported sub is the same thing as a sealed sub. (That's just way too much bandwidth.)
There are practical limits.

On the other extreme, adding unnecessary LPF's will cause the woofer's potential to go unused. (Try it, you'll see.)

Dual 21's at 10ft away with a few hundred watts going to each, should be able to reach 110db. (Box model it.)


I've heard many smokers say this will be be their last cigarette!
What do I need to understand for "bandwidth of the subwoofers"? The freq. range it works?

What about keeping the UM15" (maybe making them a little bigger) and add two 18" PA SW's? all working up to around 80hz where the mains take over.


Quote:
Originally Posted by jujuman200 View Post
Clearly... you are not familiar with this bunch of bassheads.... 110Db is the volume @ 10Hz around these parts....
"Reasonable" systems are down the hall..... 2nd door on the left.....


Juju
This forum is way beyond bass heads! I don't know if this "condition" has a name! hehehe
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post #7 of 7 Old 02-15-2020, 10:19 AM
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Quote:
Originally Posted by marto2009 View Post
The freq. range it works?
Yes. Basically: the -3db point on each side (that is plays/operates).
Sometimes expressed in octaves (mostly for musical instruments).

Generally for a subwoofer that would be 20-80hz, but could be 1hz to 300hz.

Quote:
Originally Posted by marto2009 View Post
What about keeping the UM15" (maybe making them a little bigger) and add two 18" PA SW's? all working up to around 80hz where the mains take over.
The more bass, the better.

But as mentioned, forcing high excursion woofers to play above 40hz will cause them to drink more power and eventually heat up.
High frequencies don't have much excursion, so the coil is parking and baking essentially.
(Compared to a PA woofer they will even sound boomy and weak, due to inductance and magnetic losses / low efficiency.)

If you have small mains, you might even want that figure to be 200-300hz to protect them from over-excursion and THD.
Larger mains could be 50-120hz.
I run my mid-vocals to 70hz, with a good 50hz LFE overlap (YMMV).

Mid-bass turns into mid-vocals somewhere around there, but there is a LOT of mid-bass punch between 80 to 300hz that you'd be missing out on (drums, guitars etc etc, which is basically in every song and movie ever-made!)

My MBM arrays are DC to 300hz. ~16kW burst-rated. ~8kW on-tap.
My beds are DC to 30khz. ~13.2kW burst-rated. ~52kW on-tap.
My LFE subs are DC to 130hz (the only exception is the HzHorn, which is 15hz HPF'ed.) ~60kW burst-rated. ~37kW on-tap.

The average applied-power is however, much lower.
Give or take...
In those vids for example, that's only about ~3kW RMS combined total power (real-world figure), and ~4.5kW RMS consumed from the wall. About ~19A rms and ~35A burst. Measured. (Most of my amps are %90's efficient, so that helps.)

Last edited by BassThatHz; 02-15-2020 at 10:23 AM.
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