UM-18 and RSS460HO 18 Sensitivity Comparison? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 20 Old 07-20-2018, 06:55 PM - Thread Starter
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UM-18 and RSS460HO 18 Sensitivity Comparison?

Can someone explain how the UM-18 is so renowned for being "loud" despite its sensitivity being 5dB lower than the RSS460HO 18 with virtually the same power handling? It appears by the specs that the UM-18 take a boat load more power to create the same spl. Seems that could be quite an issue if you are shooting for Referrence (115dB) at 15'.

Maybe the better question is why the RSS460HO 18 is not renowned for being "loud" given its higher sensitivity.

Anybody try a build with either of these in one of EricH's dual 18 cabinets (sealed 8 cu ft)?
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post #2 of 20 Old 07-20-2018, 07:00 PM
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The UM digs deeper into the low frequency range. The RSS460HO does better in the mid bass region. Just depends on your needs
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post #3 of 20 Old 07-20-2018, 07:34 PM - Thread Starter
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Quote:
Originally Posted by johnson636 View Post
The UM digs deeper into the low frequency range. The RSS460HO does better in the mid bass region. Just depends on your needs
Thanks. One sure cannot deduce that from Dayton's spec sheets on the two.

I'm just thinking: Where is that single 18" sub that is linear to 20Hz, handles 1200 watts (3600 watts peak), with sensitivity of 97dB, and is 8 ohms? With sensitivity like that, even my room could reach Reference with one unit.
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post #4 of 20 Old 07-20-2018, 07:42 PM - Thread Starter
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Quote:
Originally Posted by Cam Man View Post
Where is that single 18" sub that is linear to 20Hz, handles 1200 watts (3600 watts peak), with sensitivity of 97dB, and is 8 ohms? With sensitivity like that, even my room could reach Reference with one unit.
It's a trick question. It was the JBL Synthesis S1S-EX.
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post #5 of 20 Old 07-20-2018, 07:56 PM
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No sub has 97 sens at 20hz, in a standard box anyhow. The problem with sub sensitivity is what frequency do you spec it at?

The UM has a higher max spl than the HO at all frequencies.

You have to pick what you want. Sensitivity, efficiency, or max spl.
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post #6 of 20 Old 07-20-2018, 08:07 PM - Thread Starter
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Quote:
Originally Posted by Samps View Post
No sub has 97 sens at 20hz, in a standard box anyhow. The problem with sub sensitivity is what frequency do you spec it at?

The UM has a higher max spl than the HO at all frequencies.

You have to pick what you want. Sensitivity, efficiency, or max spl.
Good point...but I can't tell what frequency either sub uses for that spec.

As you might expect if you look at the size of my room (photos), I have a lot of spl to deliver to reach Reference with smooth linear response to at least 25Hz.
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post #7 of 20 Old 07-20-2018, 08:12 PM
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Quote:
Originally Posted by Cam Man View Post
Can someone explain how the UM-18 is so renowned for being "loud" despite its sensitivity being 5dB lower than the RSS460HO 18 with virtually the same power handling? It appears by the specs that the UM-18 take a boat load more power to create the same spl. Seems that could be quite an issue if you are shooting for Referrence (115dB) at 15'.

Maybe the better question is why the RSS460HO 18 is not renowned for being "loud" given its higher sensitivity.

Anybody try a build with either of these in one of EricH's dual 18 cabinets (sealed 8 cu ft)?

Compared in 4 cubic feet, both driven to xmax at 20 hz.








Sound pressure level:



Ask your doctor if DIY is right for you. Side effects of DIY may include anxiety, elevated blood pressure, lightheadedness, rapid heartbeat, skeletal muscle flaccidity, euphoria, psychological dependence, insomnia, confusion, blurred vision, implusivity, uncontrolled or repeated movements.
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post #8 of 20 Old 07-20-2018, 08:20 PM
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Quote:
Originally Posted by Samps View Post
The problem with sub sensitivity is what frequency do you spec it at?
The convention for decades for specifying driver sensitivity has been to use its asymptotic value at high frequencies as predicted by Thiele-Small parameters under the assumption of radiation from an infinite baffle and zero voice coil inductance.

Last edited by andyc56; 07-20-2018 at 08:30 PM.
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post #9 of 20 Old 07-20-2018, 08:27 PM
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Quote:
Originally Posted by Cam Man View Post
Thanks. One sure cannot deduce that from Dayton's spec sheets on the two.

I'm just thinking: Where is that single 18" sub that is linear to 20Hz, handles 1200 watts (3600 watts peak), with sensitivity of 97dB, and is 8 ohms? With sensitivity like that, even my room could reach Reference with one unit.



1200 watt power handling... nope. 3600 watt peak... just reference Data Bass tests on the JBL 2242HPL.



https://data-bass.com/data?page=system&id=109


At 28.3 volts to the driver, it's THD is already 15% @ 30 hz.



28.3 volts into the actual 7.887 ohm measured in box impedance at 30 hz translates into just 101.545 watts.



Re-read that.... 15 percent distortion at 101.545 watts.



https://data-bass.com/data?page=system&id=109&mset=121



If you believe JBL's marketing hyperbole, I have a warehouse of sailboat fuel to sell.

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post #10 of 20 Old 07-20-2018, 08:48 PM - Thread Starter
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All very interesting and educational info. Thank you for posting it.
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post #11 of 20 Old 07-20-2018, 08:51 PM
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Take a look at the distortion at 30 hz of the Stereo Integrity HT18:


https://data-bass.com/data?page=system&id=90&mset=97


At 118 VOLTS input, it is 6.25 percent, almost 300% better result than the JBL 2242HPL high-karate woofer. This translates into about 406 watts into the 34.284 ohm in box impedance at that frequency. If you look at the same 118 volt sweep, the impedance at 60 hz is 6.341 ohms, and the power across the coil is 2195.86 watts for 6.27% distortion.



JBL 2242HPL at 60 hz has a 16.325 ohm in box impedance. If you look at the distortion of the 28.3 volt sweep at 60 hz for the JBL 2242HPL, you will see it is 5.12 %. That 28.3 volts into 16.325 ohms is approximately 49.059 watts across the coil.



Which one has a better motor?


If you kept things to a 'linear' stroke, you must also limit the top end output of the JBL, or risk over excursion and corresponding distortion approaching 100% in the < 40 hz region.
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post #12 of 20 Old 07-20-2018, 09:02 PM
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Quote:
Originally Posted by michael hurd View Post
Compared in 4 cubic feet, both driven to xmax at 20 hz.








Sound pressure level:



Whoops got the power level on the drivers backwards.... AVS forums removed my edit button, so I will post corrected information in this post.











SPL:







Now that I have noticed the error, note 119.5 dB at 80 hz for the UM18, and 116.8 dB at 80 hz for the RSS460HO. The difference at 20 hz is about 5 dB advantage for the UM 18, while comparing rated xmax.

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post #13 of 20 Old 07-20-2018, 09:18 PM
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cam man,

sensitivity is measured on the upper end because the lower end sensitivity is as much a function of the cab as the driver.

1w1m um in a 4 c.f. sealed and a 9 c.f. ported tuned to 17hz (mini-marty size cab)



1w1m 460ho in 4 c.f. sealed. has about a db more sensitivity. they are very similar in that way.



the um has about 28mm or so of usable excursion and the 460ho about 22mm, so the um will give more low end output. in that way, one might say it is louder.

the 460ho has less windings, lower normalized inductance, and a slightly cleaner upper end. in that way, one might say it is a hair cleaner.

both are good.
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post #14 of 20 Old 07-20-2018, 09:29 PM
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Just noticed that Data Bass tested both of these drivers.



RSS460HO



https://data-bass.com/data?page=system&id=89&mset=96


UM 18


https://data-bass.com/data?page=system&id=116&mset=128


Burst output comparison - the two middle lines on this graph... UM18 in purple.




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post #15 of 20 Old 07-21-2018, 02:54 AM
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Quote:
Originally Posted by michael hurd View Post
Just noticed that Data Bass tested both of these drivers.
the max burst is pretty much amp limited on the upper end. the 460ho was tested with the k10. um18 was tested later after josh upgraded to the k20. i think that explains some of the difference on the upper end. but really, 300-400v is way past where folks can reasonably run these drivers in either case. ~90v is more reasonable.

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post #16 of 20 Old 07-21-2018, 09:19 AM - Thread Starter
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@LTD02 @michael hurd ...

You are very kind to educate and inform. I hope others will benefit, too.

It is interesting to read the three "reviews" on the three drivers. What is very interesting to me is the relationship of these "modern" drivers, sensitivity, spl, cabinet type, and power to creating the ability to achieve linear response to lower frequencies. In my large room, it appears that a large (MiniMarty-like around 8 cubic feet) vented enclosure with the UM-18 would be a good way to go. Whether one or two would be necessary could be explored.
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post #17 of 20 Old 07-21-2018, 10:01 AM
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@LTD02 @michael hurd ...

Whether one or two would be necessary could be explored.
If you have the space and funds, two will be better than one for a couple of reasons. Each one will only have to work half as hard, which means distortion will be lower. More importantly, with two, room modes won't be as much of a problem.
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post #18 of 20 Old 07-21-2018, 10:12 AM
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Many times sensitivity is a derived figure (calculated), but sometimes it is measured over a specified frequency range under specific conditions. Like Sanz said, no sub has 97 dB sensitivity @ 20Hz because that is alignment specific. The low end output is strictly governed by the alignment. That's the whole point of T/S parameters- to predict this output based on user-defined enclosures and tuning.

If the sensitivity is calculated, one can use the equation to verify:



If the DCR of the driver is much lower than 6.8Ω, then the 2.83V sensitivity ends up a bit higher, that I've seen anyways.

BUT, this spec is not for any frequeny you are dreaming of. This specifies the Mid-band sensitivity, defined by EBP (which is also sometimes used to see how suitable a speaker is for closed ↔ vented type alignments.

EBP = Fs / Qes, where EBP is in units of Hz.

The midband region is: EBP to 2*EBP. ← This range is where the sensitivity manifests itself strongly. Above that, response has to be measured, below that it is completely governed by the alignment, and thus predictable by T/S analysis (aka: subwoofer enclosure software modeling).

This is a picture I had posted on another forum describing where the midband frequency range would be for a woofer with an EBP of about about ~100hz. It will generally extend for about 1 octave without much fluctuation, unless it is wayy into the bass region.


That particular woofer had a midband that extended about 1.5 octaves above the EBP frequency.
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post #19 of 20 Old 07-21-2018, 11:01 AM - Thread Starter
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Quote:
Originally Posted by dorri732 View Post
If you have the space and funds, two will be better than one for a couple of reasons. Each one will only have to work half as hard, which means distortion will be lower. More importantly, with two, room modes won't be as much of a problem.
True on the former. On the latter, I am blessed that both can fit in space that is acoustically friendly to LF response. In other words, no mode issues; easy for xt32 or the Sub Equalizer to EQ to very smooth response. I use OmniMic at the same MEQ mic positions to verify what MEQxt32 has done, then manipulate the LCR response mildly with the MEQ App and the sub trim to emulate the Harman target curve. Each tweak pass verified with another round of spatial averaged OmniMic measurements.

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post #20 of 20 Old 07-26-2018, 03:32 PM
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I am just now getting to respond to this but I am running two JBL S1S with the 2242HPL in them the second gen of the non EX. I am also running two 4647As and one 4648H-8. The S1S are on one channel at 4ohms and the other 2226 based boxes are on the other channel at about 2.7ohms. They are connected to one iNuke 3000dsp Maybe I can help answer some questions?

Here is my sweep with dsp off and all my amps set at 50% volume(my mains are on NU4-6000s I have 3) and the preamp at -17.5db. Measured from my listening position.

Here is a link to my rew file. Download Rew File

I'll answer any questions or run tests if it helps?
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