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Discussion Starter #1 (Edited)
I'm thinking of building two 15" Ultimax subs in 3 cubic foot per sealed enclosures offered from Parts Express. These fit my space limitations. At 4 ohms I'll get 880 watts RMS per channel (sub rated at 800 RMS). The EPX4000 is a class H amp so efficiency is a bonus as well.

So, how is this setup going to sound in a 12'x20'x8' room with the sub up front 1/4" in from each wall? This is a dedicated home theater with two rows of theater seating. Priorities are sound quality, SPL and low end extension to a lessor extent.

I have the free version of winISD, but it doesn't seem I can add an amp with that version or account for 3 pounds of polyfill added to the 3 cubic foot sealed enclosure as suggested by PE.

Ideally, I'd like to get an idea of how this setup would stack up against dual SVS SB-13 Ultras. I realize the cost of the SVS will be much higher, but interested in getting thoughts on comparison. Both of these options fit my space requirements.

Final question, is it still a requirement to buy a Cleanboxpro with the miniDSP if I'm running a Denon AVR or will the miniDSP up-conver the output voltage?

Thanks for any advice you can give!
 

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Strangely, the FAQ seems to imply both the balanced and unbalanced models output the same, 2 volts: https://www.minidsp.com/support/30-faqs/minidspbasics

I'm I missing something? Also, anyone know the sub output voltage on the Denon 3312?
Oh who knows... Their documentation conflicts itself all over the place. The datasheet for output says "Maximum level, unbalanced: 0.9Vrms (2.5Vpp)". The Manual says the same thing.

I've measured a balanced 2x4 unit looking for clipping. I have a pretty good handle on how it works. I've never measured a unbalanced 2x4, so I can't say for sure.
 

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Discussion Starter #7
Oh who knows... Their documentation conflicts itself all over the place. The datasheet for output says "Maximum level, unbalanced: 0.9Vrms (2.5Vpp)". The Manual says the same thing.

I've measured a balanced 2x4 unit looking for clipping. I have a pretty good handle on how it works. I've never measured a unbalanced 2x4, so I can't say for sure.
Ok, yes, i see that in the specs too where is says .9 max unbalanced output. I sent an email for clarification, but I'm guessing I'll just go the unbalanced option.

Any thoughts on this particular setup in terms of sound quality, etc?
 

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Ok, yes, i see that in the specs too where is says .9 max unbalanced output. I sent an email for clarification, but I'm guessing I'll just go the unbalanced option.
If it's really .9Vrms, that's not enough voltage to drive a pro amp adequately.

Any thoughts on this particular setup in terms of sound quality, etc?
Sorry, no. I haven't heard either, but they're probably capable of similar output. How loudly do you listen?
 

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Discussion Starter #10
If it's really .9Vrms, that's not enough voltage to drive a pro amp adequately.


Sorry, no. I haven't heard either, but they're probably capable of similar output. How loudly do you listen?
Agreed. If found the manual for the unbalanced and it confirms .9v max. The input sensitivity on the EPX4000 amp is 2.5 dBu (1.03 volts) and the input impedance is 10 k-ohms for unbalanced and 20 k-ohms for balanced. Not sure how that plays in.

Regarding the sub setup, I was hoping someone could model the situation with:

- Quantity 2, Dayton Audio UM15-22 in a 3 cubic foot sealed enclosure, with 3 pounds polyfill
- Amp running at 4 ohms 880 watts RMS per channel (1220w peak) sub run on each channel

Data bass has the results with a single SB13 Ultra so I could at least compare to a single. I'm assuming people here have the capability to do this and sure would appreciate it.

One other thing, I could go a little more extreme and run the Stereo Integrity HST 15" and could get each channel down to 2 ohms, getting 1400 RMS / 2080 Peak to each sub. Same enclosure...it's tempting, but I want to model the situation and see what it looks like! :)
 

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Hi Mike,

Do you have a picture of the room you can show?

I have a similar plan in a similar sized dedicated theater room. My room is approximately 12’ x 19’ with 8’ ceilings, also with two rows of seats. My challenge with a relatively small sealed room with two rows of seats is limited placement options.

I plan on three subwoofers; One LMS-Ultra 5400 18” in a 4 cubic foot sealed enclosure and two ea. LMS-R 15” subs in 3 cubic foot sealed enclosures. I will connect the 18” to LFE preout 1 and connect the two 15” subs to LFE preout 2. The two 15’s will be placed side by side in my preferred front stage location and connected to the LFE output with a Y cable, looking like a single sub for calibration with Audyssey XT32 + SubEQ HT.

What Audyssey version does your pre-pro/AVR support and if Xt32 + SubEQ is supported, why do you think the mini DSP is needed?

SVS has an article on their website titled “Why go dual” and recommends placement options”
1. on the front stage in the corners
2. on the front stage at the 1/3 wall points (basically flanking the center channel near each main speaker)

Hopefully that works in my room since it is the only convenient location.
 

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Discussion Starter #12
Hi Mike,

Do you have a picture of the room you can show?

I have a similar plan in a similar sized dedicated theater room. My room is approximately 12’ x 19’ with 8’ ceilings, also with two rows of seats. My challenge with a relatively small sealed room with two rows of seats is limited placement options.

I plan on three subwoofers; One LMS-Ultra 5400 18” in a 4 cubic foot sealed enclosure and two ea. LMS-R 15” subs in 3 cubic foot sealed enclosures. I will connect the 18” to LFE preout 1 and connect the two 15” subs to LFE preout 2. The two 15’s will be placed side by side in my preferred front stage location and connected to the LFE output with a Y cable, looking like a single sub for calibration with Audyssey XT32 + SubEQ HT.

What Audyssey version does your pre-pro/AVR support and if Xt32 + SubEQ is supported, why do you think the mini DSP is needed?

SVS has an article on their website titled “Why go dual” and recommends placement options”
1. on the front stage in the corners
2. on the front stage at the 1/3 wall points (basically flanking the center channel near each main speaker)

Hopefully that works in my room since it is the only convenient location.
I will get some pics taken so you can take a look.

I have the Denon 3312ci which has the Audyssey MultEQ XT. I also have an X4000 downstairs with Audyssey MultEQ XT32, but can't move it because of the HDMI for zone2 there. I know the XT does not EQ the subs separately. It has two sub outputs but it essentially uses an internal Y cable to offer the multiple outputs. So, i guess my thought is I want an EQ. Maybe I don't need one, but with a sealed setup I definitely want to flatten out response. Thoughts?

If I can't make the miniDSP work I will probably do a NU6000DSP. It puts out way more than the UM-15s can handle, but I can set the limiter. I'm also considering the HST15s. The HST15s are $425 each shipped, run in a small enclosure, and if they are anywhere close to the HST18 data on data-bass.com they should be pretty nice....and I probably don't need the HSTs. :)

Please let me know if you have any other thoughts. Thanks.
 

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I dont see anything on an hst 15 , afaik si isnt making any 15", i had a sing 15" um in a 3cft and i did simulate do 15 um, i think it took at minimum 4.5 cft to do any good
 

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Discussion Starter #14 (Edited)
I emailed with Nick from SI on Tuesday and he said there was an HST-15. Sounds promising. Waiting for specs.

Another option for me could be the LMS-R 15". Here are the Ultimax and LMS-R with an 80 liter sealed enclosure. Any thoughts on the Ulitmax vs LMS-R for SQ?
 

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I have 3 EPX4000 amplifiers and have tested both balanced and unbalanced 2x4 MiniDSP.


The unbalanced Version is the one you want to use as it gives much more voltage than the balanced.
 

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