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Discussion Starter #1 (Edited)
don't make fun of the following

I have a history with subs...

1st real sub was a sunfire, it shook things but was muddy and not too fun. Also had to have it repaired twice. Before repairing it the third time I went DIY with a Bill Fitzmaurice Tuba HT LP folded horn. It was very efficient, huge but lacked super low frequency. Next attempt was two Dayton UM18's in a "full marty" ported box (tuned to 18hz I believe). These are powered with an inuke 3000 to each giving them about 2,000 watts each. these shake the entire house with test tones. Literally 5000 sq feet vibrating and begging for mercy. The down side is there is no pop or oomph in the bass. No defined chest thump. In my car I have a single sealed 10" with a 500 watt amp, it is very tight and thumping. I want this in my theater room.

I'm thinking moving to sealed will help. The two choices im thinking about are taking my existing UM18's and putting them in 4 cubic foot sealed boxes and powering them with the same iNukes or 2 SVS SB16's. The price difference would be a couple grand not prohibitive but I don't want to throw money away either. The finish and/or WAF is not important to me, I have 2 refrigerators in my room 4 if you count the mains.

Room/equipment specifics

16ft w/ 21.5ft deep / 8 ft suspended ceiling
2 of the 4 wall and floor are poured concrete, the other two walls are 2x6 "soundproof" walls.

equipment
Mains Polk SDA SRS2.3 powered with Adcom GFA 555 crossed at 60 hz
Center and surrounds Klipsch something or another powered with Adcoms crossed at 80hz
4 Atmos in ceiling also Adcom powered crossed at 80hz
main listening position is about center of the room 9ft from front wall. This isn't really movable due to installed riser.


the system gets plenty loud and is nice and clear but lacks the punch I get in my car with a single 10" sub

Thoughts? Sealed 18 DIY's, SVS, or shut up and quit whining? The latter really isn't an option
 

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For what it's worth... I believe a lot of people seek the deep register down to 20hz and lower. This isn't where thumpy music bass is. The music in your car is punchy because it's mostly 40hz/50hz and higher. That's where the punch lives in music.

For movies with explosions I like 20hz for the rumble and shake. However, for music I use a low cut, high pass filter at 40 hz. That's right, I cut out the lowest frequency and redirect the energy to be focused on the mid bass area (40 to 120hz). Now all the power is focused on producing the frequencies available in music. It gets tighter, cleaner and more punch. It eliminates that annoying over bloated boom sound and you can add more power to the bass you're looking for. (the subs are still crossed over to the main speakers at 80hz. Don't let the mains try to reproduce the low frequency no matter how good they are.)

Try not digging so deep for the holy grail.
 

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Discussion Starter #4
I understand that the punch is upper bass but I seem to miss it playing the same tracks. When measured it says the output is there but I don't feel it the same. Furniture moves, walls vibrate but my chest doesn't thump. Is that ported vs sealed? And would I get the same response with DIY as SVS, or close?
 

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Discussion Starter #5
Do you run the subs in stereo or do run them 'summed' in mono?
Not sure to be honest. The Yamaha RXA3050 has dual LFE outs each is run to a separate sub and the menu has both as active. I'm not sure if the unit is summing them or not.
 

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main listening position is about center of the room 9ft from front wall. This isn't really movable due to installed riser.
This sitting location is probably less than ideal. Sitting at any of the 1/3 or 1/5 points in the room would be better. That rule includes side to side AND front to back. Have you tried sitting in a chair in different locations? Have you tried moving the subs around? Near field? Diagonal cross corner?

If there is a null in the middle you must relocate or else live with what you have no matter how much power you give it.

The main polk speakers should be crossed at 80hz.

IMHO if you aren't getting excellent bass from 2 UM 18's with 2000 watts each in a room that size I question if there would be any improvement going with sealed boxes. There must be another problem.
 

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Discussion Starter #8
One problem with these monsters is there is no place for them but the front corners of the room. They are simply too big. I would have more options with smaller sealed boxes. I changed the crossovers on the mains to 80 hz this afternoon with no noticeable change. moving the seat really doesn't work either. Its a 12 foot long sofa that backs up to a riser with a row of recliners on it. I have tried the recliners, bass is no better and I hate sitting in recliners.

I'm pretty sold on the idea of trying a pair of sealed subs. Do you think that SVS SB16's would be much better than sealed UM18's with 2000 watts each? Or is that a crazy question?

Using a calibrated mic and room EQ Wizard the listening position measures ok. No big dips. I'll measure again tomorrow and see if I can post the measurement.
 

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Discussion Starter #9
Using a calibrated mic and room EQ Wizard the listening position measures ok. No big dips. I'll measure again tomorrow and see if I can post the measurement.
 

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Full Marty's are ported subwoofers and that alignment is known for the bass range you're looking at (40-70Hz is frequently what gives the most "kick in the chest" sensation). You likely have the correct ammunition, but maybe not the right aim; it could very well be a room null that's taking away that range. It also might be a phase issue in the crossover region. If you can, post the REW sweeps from the main listening position. Either way, the SB16 will not solve the problem. If anything, it would make it worse. Not because the subwoofer is bad, far from it, but because the issue is probably not the subs.
 

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Discussion Starter #13
maybe if I was smart enough to use REW these wouldn't look so bad. I also have miniDSP2x4 HD in line these are after EQ applied

Also both subs are against the side walls. Don't know if that matters but they are too tall to move 1/4 wall in.
 

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A dip? That's like saying the Grand Canyon is a hole in the ground... :eek: :)

The right sub is about 25dB down on the left @ 20Hz, yet the summed output doesn't reflect it at all. That seems off to me. There may be something about the measurement technique which is creating an anomaly. Also, can you run a full range sweep with detail on the speakers/subwoofer integration at the crossover frequency? There might be a phase issue contributing to the problem.
 

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Discussion Starter #15
I ask this in the seeking help sense.
If it were a phase issue, would the individuals look good and the both be low? The fact that the right has lower output alone wouldn't indicate phase, right? If it were a phase issue reversing the polarity on the right would invert the line, right? Boost below 38 and cut above it. I think the above 38 is what I want. I'll try reversing polarity tomorrow on the Right and see what happens, maybe I'll take tonight to study up on the Mini DSP and REW.

Also contributing might be distance the right is 3-4 feet further from listening than the left. Not that big of a difference but a contributing factor?
 

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A phase issue generally appears as a pronounced dip in the crossover region, which is why I'm looking for a measurement that includes everything. It's hard to miss when viewed on a graph. You have one sub that gradually decreases in output and stays well below the other for an extended period of time, and it starts at a relatively low 40Hz. That pattern is not indicative of a phase issue. The slight inverse bump around 70Hz is more typical of a phase problem, but that particular dip is unlikely to be audible as it isn't all that bad really.

Reversing polarity would invert phase 180 degrees, but that is only advantageous under certain conditions. For the most part phase is not an either/or adjustment, it's variable, which is why an amp with a toggle switch that has but 0 or 180 degrees is only beneficial for subs that directly oppose each other (when they're positioned on opposite sides of the room and facing one another for example). A rotary dial that allows for minute adjustments is better. In that manner you can set it for something like 20 degrees or 120 degrees, depending upon the need. That level of adjustment is almost mandatory when multiple subwoofers are placed on a similar, but not identical, physical plane relative to the listeners.

Distance from the seating position will alter measured output, but definitely not by 25dB. That's an extraordinary difference, and I don't mean that in a good way. Co-located subwoofers increase output about 6dB for the first pair, but as you add more the increase is no longer linear and won't grow in even multiples of 6. Assuming it did however, you're looking at the equivalent 1 subwoofer versus 4 in regards to the output variation between your left and right units @ 20Hz. That's huge. Can you measure SPL from a spot equidistant from both subwoofers? I'm wondering what that might yield.
 

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I think the first thing would be to focus on the SDA SRS2.3's. Some have said they have less bass than some of the other SDA speakers. This is where the kick in the chest starts. Is really hard to believe that speakers of that size alone aren't creating significant midbass impact with the subs off. Yet, two 18" monsters with power behind them and still no kick? You have a serious problem in your room. I think getting the mains to kick in your room without subs would be the first priority. Many don't want or think of room correction for mains or playing with the placement, etc.....but some rooms may require it to get a desired response.

Then only then integrate the subs. IMO, I think it would be crazy to spend $4000 on SB16's when you already have a system that should be killing it in the midbass and subbass department. I think you have to figure out the response challenges first then try to contour it with whatever tools, ajustments you can make. At some point, maybe as a trial, build the 4 cu ft box or buy a $120 flatpack and see how you like the driver sealed. if you like it, convert the other.
 

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Discussion Starter #18
At some point, maybe as a trial, build the 4 cu ft box or buy a $120 flatpack and see how you like the driver sealed. if you like it, convert the other.
That's kinda what I was asking to start with. Now I'm wondering about all kinds of stuff. I went to measure the subs nearfield as the jman asked and my projector died. Got a new one ordered and will post measurements once its here.

as far as the polks go, the punch is why I bought them. haven't tried them full range in this room, never occurred to me.
 

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Yeah, I would turn the subs off and unleash the Polks in 2 channel mode to see what you have in your room. If they sound underwelming in the low end then right there you know its not the subs but your room. Listen with room correction on and off.

Get the mains to the point of making you smile, then figure out a way to integrate the subs to totally knock your socks off! Play with placement, x-over points, phase, EQ, time alignment, etc.

Also, if you have not done so, and do plan to go sealed at some point, maybe read up on the Earl Geddis method of three subs to get even coverage in a room. Here's a great post from Mark Seaton on how he had a serious cancellation problem with three subs in an ubber expensive installation. What needed to be done was just some time delay on the rear sub to remove a major cancellation.

http://www.whatsbestforum.com/showthread.php?7501-Seaton-Submersives-amp-Rockport-Arrakis-amp-Mira-Grands/page3&

Subs can be a major pain in the butt in some rooms to get right. It sounds like you have work on your hands. Not all rooms are created equal. I know as i can only think of all of the rooms I've played my drum set in over the years. My, My, My does it sound different depending on the room and where I place the kit. Subs are the same and maybe worst in some ways.
 

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If you have attic above your listening room , do some looking at IB manifold setup ... I have just 1 IB 24 in my media room now but planning on the manifold setup in my attic when I can afford the 2nd sub.... FWIW just 1 mounted in a rear doorway to my media room is putting out a rediculous amount of LFE especially below 20hz.... I realize your discussion is for 70-90 or so.... I only run mine from 50hz down but wanted to put this IB bug in your ear .... My 2 Ultimax 15's are now being dwarfed by one 24in IB....driven by a XLS 1502....I do Home Theater install and I dont know of any retail sub that will put out as much uncolored massive sub energy as this bad boy.. 2 of them in a manifold may ruin your foundation..... and the SQ is unreal....

http://stereointegrity.com/product/ib-24-24-subwoofer/
 
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