2 SI HT18 18″'s vs. 1 UM18-22 18" Ultimax - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 57 Old 01-07-2015, 12:30 PM - Thread Starter
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2 SI HT18 18″'s vs. 1 UM18-22 18" Ultimax

My sub situation right now is a Minimarty with 1 UM18-22 18" Ultimax powered by an Inuke 3000dsp (bridged mono @ 4ohms). It sounds great and I can't complain...of course more output is always appreciated since the room is large [around 4000 sq. ft.]

Since Stereo Integrity is offering free shipping on the HT18's now I'm wondering if I'd be doing myself a favor by building a 2nd minimarty (or marycube) and running 2 HT18's in stereo @ 2 ohms.

I imagine I could sell my one month old Ultimax for around $200, taking my cost of the HT18's from $318 to $118. Add about $100 for the cost of building a new enclosure and I'm out about $218.

So is going from 1 Ultimax to 2 HT18's worth it for $218? Specifically, will the output and quality be improved by adding either a 2nd minimarty or a martycube and going to the different speaker?
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post #2 of 57 Old 01-07-2015, 12:42 PM
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I'd expect to gain about 3db and a smoother response (assuming you don't place the subs right next to each other)
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post #3 of 57 Old 01-07-2015, 01:32 PM
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There is a forum member that has a UXL18 and an Si18 marty sub and he said he could not tell the difference between the two of them. He also, said that he does not blast them at max spl though. Why not just get the SI and make another sub and keep the um18? That will save you the most.

Doesn't SI normally ship out drivers for 5 dollars?

I think it was @chalugadp

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post #4 of 57 Old 01-07-2015, 02:10 PM - Thread Starter
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Quote:
Originally Posted by niktak11 View Post
I'd expect to gain about 3db and a smoother response (assuming you don't place the subs right next to each other)
Thanks! I have a lot of room, so I can space them out pretty easily.
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post #5 of 57 Old 01-07-2015, 02:24 PM - Thread Starter
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Quote:
Originally Posted by Pain Infliction View Post
There is a forum member that has a UXL18 and an Si18 marty sub and he said he could not tell the difference between the two of them. He also, said that he does not blast them at max spl though. Why not just get the SI and make another sub and keep the um18? That will save you the most.

Doesn't SI normally ship out drivers for 5 dollars?

I think it was @chalugadp
If I went with the one SI (with my one Ultimax) I would have to match the 4 ohms of the Ultimax in stereo so I'd only get 680 watts RMS per channel which is probably less than what I'm now getting bridged mono. If I got two SI's I can then run them @ 2 ohms with the potential of 1040 watts RMS per channel.

Shipping used to be two for $60 for me so that's a decent savings.
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post #6 of 57 Old 01-07-2015, 02:59 PM
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First of all 2 equivalent subs will always be better than one. The SI 18 and the UM 18 are pretty close based on the charts I have seen.

Your last question has me curious. Could you run the UM18 off one channel in 4 ohm mode & run the SI 18 off the other channel in 2 ohm mode? If this is even possible I think you would have to set the INUKE to dual mono mode so each sub could be controlled separately.
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post #7 of 57 Old 01-07-2015, 03:27 PM
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The right answer is to get the two SI HT18s and another amp, and have three subwoofers.
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post #8 of 57 Old 01-07-2015, 04:35 PM
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Quote:
Originally Posted by DaleNixon View Post
If I went with the one SI (with my one Ultimax) I would have to match the 4 ohms of the Ultimax in stereo so I'd only get 680 watts RMS per channel which is probably less than what I'm now getting bridged mono. If I got two SI's I can then run them @ 2 ohms with the potential of 1040 watts RMS per channel.

Shipping used to be two for $60 for me so that's a decent savings.
Ah yes, I wasn't even thinking about the amp part. Your post makes perfect sense.


Since reading your post, you just cost me $318.00! I had to pick up two of them.

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post #9 of 57 Old 01-07-2015, 05:31 PM
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Originally Posted by rhodesj View Post
The right answer is to get the two SI HT18s and another amp, and have three subwoofers.
what he said
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post #10 of 57 Old 01-07-2015, 05:38 PM
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And part two of that answer is, make the second amp an NU6000 so you can add another UM18 later for four subs. Two HT18 D4s on the existing NU3000, use the 6K for the Daytons.

Budget? What's that?
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post #11 of 57 Old 01-07-2015, 07:20 PM
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The si18 and um18 are not close at all. The um18 can handle 700 more watts and has greater xmax. I gained 3 to 4 dbs upgrading to um18. Add two martycubes Near field if you can. Ideally a second mini.
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post #12 of 57 Old 01-07-2015, 08:01 PM - Thread Starter
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Quote:
Originally Posted by rhodesj View Post
And part two of that answer is, make the second amp an NU6000 so you can add another UM18 later for four subs. Two HT18 D4s on the existing NU3000, use the 6K for the Daytons.

Budget? What's that?
I have already thought about holding onto the Ultimax for a later amp purchase. But I have to draw the line on the amp purchase due to too many other large purchases lately. I may just get the two SI's...still haven't decided. I've got a few more weeks to decide.
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post #13 of 57 Old 01-07-2015, 08:18 PM - Thread Starter
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Quote:
Originally Posted by chalugadp View Post
The si18 and um18 are not close at all. The um18 can handle 700 more watts and has greater xmax. I gained 3 to 4 dbs upgrading to um18. Add two martycubes Near field if you can. Ideally a second mini.
Wait...isn't the um18's xmas 22mm vs. the si18's 22.5?
And isn't the RMS handling just 1000w to 600w favoring the um18?
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post #14 of 57 Old 01-07-2015, 08:37 PM
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Quote:
Originally Posted by DaleNixon View Post
Wait...isn't the um18's xmas 22mm vs. the si18's 22.5?
And isn't the RMS handling just 1000w to 600w favoring the um18?
No . xmax is closer to 26 and um18 can handle 1800 watts and si is 1100.

Last edited by chalugadp; 01-07-2015 at 09:04 PM.
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post #15 of 57 Old 01-07-2015, 08:37 PM
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there really needs to be some sort of red flag on xmax specs.


there are at least four ways to specify it.


xmax on the um18 is about 27-28mm. 22mm is the overhang of the coil outside the magnetic gap. that is a very old and outdated way to spec xmax.

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post #16 of 57 Old 01-07-2015, 09:03 PM
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there really needs to be some sort of red flag on xmax specs.


there are at least four ways to specify it.


xmax on the um18 is about 27-28mm. 22mm is the overhang of the coil outside the magnetic gap. that is a very old and outdated way to spec xmax.
Thanks for straightening that out John
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post #17 of 57 Old 01-08-2015, 06:05 AM
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Quote:
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Thanks for straightening that out John
Donny, weren't you running UXL's at some point?
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post #18 of 57 Old 01-08-2015, 07:43 AM
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that is a very old and outdated way to spec xmax.
Why do you think Dayton is using that method?
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post #19 of 57 Old 01-08-2015, 08:50 AM
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Two 18's with 22mm xmax is equal to a single driver with 44mm xmax. I would take two SI mini marty subs that can be placed for frequency smoothing over a single um18 any day. Both excellent drivers!
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post #20 of 57 Old 01-08-2015, 09:06 AM - Thread Starter
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Quote:
Originally Posted by chalugadp View Post
No . xmax is closer to 26 and um18 can handle 1800 watts and si is 1100.
OK, I can't move up to 3 or 4 subs at this time, though I may just hold onto the Ultimax for later...these are my two present choices:

1 UM18 mono [1800w rms] or
2 SI HT18 stereo [2x1100 = 2200w rms]

I'm still new to WinISD and am showing a 6db improvement with the 2 SI's, niktak11 says there should be a 3db improvement

Should I just stick with the single Ultimax I have or will there be clear and noticeable improvement by adding a 2nd box and going with the 2 SI HT's? Thanks!
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post #21 of 57 Old 01-08-2015, 09:10 AM
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Quote:
Originally Posted by DaleNixon View Post
OK, I can't move up to 3 or 4 subs at this time, though I may just hold onto the Ultimax for later...these are my two present choices:

1 UM18 mono [1800w rms] or
2 SI HT18 stereo [2x1100 = 2200w rms]

I'm still new to WinISD and am showing a 6db improvement with the 2 SI's, niktak11 says there should be a 3db improvement

Should I just stick with the single Ultimax I have or will there be clear and noticeable improvement by adding a 2nd box and going with the 2 SI HT's? Thanks!
I'd be surprised if you gained more than 3-4dB. A 6dB gain is what you'd get if you added another UM18 and another inuke
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post #22 of 57 Old 01-08-2015, 09:19 AM - Thread Starter
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Originally Posted by niktak11 View Post
I'd be surprised if you gained more than 3-4dB. A 6dB gain is what you'd get if you added another UM18 and another inuke
I'll accept your numbers over mine. If the improvement is only 3db's it would probably not even be noticeable and not worth the effort. Like I said I am happy with just the single Ultimax at this time. I just thought if there was a simple low-cost upgrade I'd go for it. This doesn't seem to be much of an upgrade.
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post #23 of 57 Old 01-08-2015, 09:48 AM
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I have a question for you guys on sensitivity.

Per parts express
The RSS460HO is rated 89.2 dB 1W/1m
The UM18 is rated 88 dB 2.83V/1m

With an 8ohm speaker, 1w/1m is the same as 2.83v/1m. With a 4 ohm speaker 2w/1m is the same as 2.83v/1m. I guess I am asking how comparable are these sensitivity ratings without more info?
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post #24 of 57 Old 01-08-2015, 10:39 AM
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Quote:
Originally Posted by niktak11 View Post
I'd be surprised if you gained more than 3-4dB. A 6dB gain is what you'd get if you added another UM18 and another inuke
You would only gain 6db's if the boxes were mutually coupled. If not, you would only get around 3db in theory.


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Originally Posted by DaleNixon View Post
I'll accept your numbers over mine. If the improvement is only 3db's it would probably not even be noticeable and not worth the effort. Like I said I am happy with just the single Ultimax at this time. I just thought if there was a simple low-cost upgrade I'd go for it. This doesn't seem to be much of an upgrade.
A 3db gain is definitely noticeable. But the advantage of having multiple subs is for smoothing and is in fact a nice upgrade.

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post #25 of 57 Old 01-08-2015, 10:44 AM
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2 SI's are better than one UM. Hell, two would equal a LMS 5400 as spl is concerned.
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post #26 of 57 Old 01-08-2015, 01:23 PM - Thread Starter
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A 3db gain is definitely noticeable. But the advantage of having multiple subs is for smoothing and is in fact a nice upgrade.
Thanks for the info. I'm still on the fence and part of it depends upon whether I'm ready to take the time to do the 2nd box. Anyone else please feel free to chime in with opinions and advice.
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post #27 of 57 Old 01-08-2015, 01:27 PM - Thread Starter
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2 SI's are better than one UM. Hell, two would equal a LMS 5400 as spl is concerned.
Leaning more and more towards the two. What if I just add a MartyCube to go with my MiniMarty instead of having two mini's?
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post #28 of 57 Old 01-08-2015, 01:30 PM
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Quote:
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Thanks for the info. I'm still on the fence and part of it depends upon whether I'm ready to take the time to do the 2nd box. Anyone else please feel free to chime in with opinions and advice.
Building the box is always the worst part IMO.
I am an electrical guy and not a carpenter.


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Leaning more and more towards the two. What if I just add a MartyCube to go with my MiniMarty instead of having two mini's?
If you know how to tune, no problem. You will have two different port tunes so you need to know how to integrate them with each other. Setting delays will be the key.

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post #29 of 57 Old 01-08-2015, 03:15 PM
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Frist, I hope the OP room is 4000 cu ft and not sq ft as mentioned. From my experience one Ultimax need one I Nuke 3000 DSP amp and the I Nuke 6000 DSP is ideal for two of the Ultimax drivers. It is good to hear the Ultimax Xmax is closer to the 27mm which I suspected and not the 22mm figure.
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post #30 of 57 Old 01-08-2015, 04:38 PM
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Quote:
Originally Posted by Luke Kamp View Post
I have a question for you guys on sensitivity.

Per parts express
The RSS460HO is rated 89.2 dB 1W/1m
The UM18 is rated 88 dB 2.83V/1m

With an 8ohm speaker, 1w/1m is the same as 2.83v/1m. With a 4 ohm speaker 2w/1m is the same as 2.83v/1m. I guess I am asking how comparable are these sensitivity ratings without more info?
The 4ohm speaker's comparative sensitivity is 3db lower than what's given for 2.83v, which would be 2w at 4ohms.
4ohms 1w is 2.0v.

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