8x 18" LMS Ultra 5400s in 4 sealed enclosures - Page 6 - AVS Forum
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post #151 of 518 Old 02-18-2011, 09:29 AM
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Originally Posted by dbldare View Post

This was a HUGE part of the papers that came with my Polk SRT system. It is definitely cleaner and more efficient than my previous systems. So much that I even had to pull out the 'ol Rat Shack meter to make sure. I thought it was hype, but the meter doesn't lie.

Bottom line, this is a fun hobby but be careful. With these systems it doesn't take too long before your hearing starts to suffer. The problem with this type of damage is best explained with the cooking a frog story. How do you boil a frog? Very slowly, turning up the heat gently so it doesn't "hop" out of the pot. It isn't an instant thing with audio either.

dbl

I still think those Polk SRT's are cool. Pretty much the only Polk product I'd like to own. I remember drolling over those years ago.

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Pioneer elite(RS2 clone)

Dude! Nice find.

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I was going to run some distortion numbers last night but ended up watching the Hurt Locker. My room pressurized much better than before with this movie. Notnyt, you should play the first scene at reference with the subs 5-10db's hot, it was awesome!!

Hell yeah! The explosion in the openning is awesome. Better yet is the .50cal machine gun mid way through the movie.

My Dual 18" LLT subs 120dB down to 10hz

 

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post #152 of 518 Old 02-18-2011, 09:44 AM
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Stdgz,
I agree I normally listen 20 below, 15 max, anything higher is just not comfortable,dialog wise, I do run the subs hot though.
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post #153 of 518 Old 02-18-2011, 11:12 AM
 
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Originally Posted by MKtheater View Post

Pioneer elite(RS2 clone)

Very nice. You now have an image that matches your sound. I looked at a couple of used RS1's, but decided to buy new. I am picky about my image and send them off for repair (under warranty) for things that others ignore. I am as bad with projectors as some of you guys are with speakers and subs. I now have and use three projectors in my house. Two in the dedicated room and one in the family room.

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You have subs that most of us can only dream about. Beautiful looking speakers and subs. Love the look of black uncovered drivers in black boxes. That is how my speakers and subs look.
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post #154 of 518 Old 02-18-2011, 01:49 PM
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I missed this. The Maelstroms were defective? What gives?

Evil is Good
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post #155 of 518 Old 02-18-2011, 02:04 PM
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It is interesting that both distortion and and perceived SQ were improved albeit slightly. I wonder if it is inherent to the difference in drivers or the fact that the the LMS's are in a lower Q alignment given the same size enclosure. By my calcs, the LMSs should be around .56 Q whereas the MX's were around .68 Q.

I know eq was applied to both and the end results should be similar. I'm just curious if there are other nuances at play.

Nyt, do you get any rocking of the enclosures when playing 125db at 10hz? That should be significant excursion.

All in all, that is very impressive in a room that size.
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post #156 of 518 Old 02-18-2011, 02:13 PM
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I missed this. The Maelstroms were defective? What gives?

Search is your friend.

I'll make it easy for you; as of right nowthe answer you seek is only 20 or so posts down from this one.
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post #157 of 518 Old 02-18-2011, 02:29 PM - Thread Starter
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Quote:
Originally Posted by coctostan View Post

It is interesting that both distortion and and perceived SQ were improved albeit slightly. I wonder if it is inherent to the difference in drivers or the fact that the the LMS's are in a lower Q alignment given the same size enclosure. By my calcs, the LMSs should be around .56 Q whereas the MX's were around .68 Q.

I know eq was applied to both and the end results should be similar. I'm just curious if there are other nuances at play.

Nyt, do you get any rocking of the enclosures when playing 125db at 10hz? That should be significant excursion.

All in all, that is very impressive in a room that size.

No rocking. Keep in mind they probably weigh a good 275lbs.
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post #158 of 518 Old 02-18-2011, 03:46 PM
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Originally Posted by mjg100 View Post
Very nice. You now have an image that matches your sound. I looked at a couple of used RS1's, but decided to buy new. I am picky about my image and send them off for repair (under warranty) for things that others ignore. I am as bad with projectors as some of you guys are with speakers and subs. I now have and use three projectors in my house. Two in the dedicated room and one in the family room.
Wow! Three PJs. Initially, when searching last year, I looked hard at the Pro8100 - but lots of guys were having banding issues and would exchange 3,4,5+ units til they got a good one. Did Viewsonic address the QC issues, more recently?

OP, sorry for the tangent. Love the subs - would like to do something similar next year, although for budgetary reasons I'd spec the LMS-R 15" driver instead in my build, and probably only 4 of 'em.
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post #159 of 518 Old 02-18-2011, 04:26 PM
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Was that thunder I just heard or just the sound from notnyt's subs making its way to me on the south shore? In all seriousness I bet it feels good to be done with the build saga and to just be able to enjoy working subs.
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post #160 of 518 Old 02-18-2011, 04:58 PM
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Search is your friend.

I'll make it easy for you; as of right nowthe answer you seek is only 20 or so posts down from this one.
Short rings gone.

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post #161 of 518 Old 02-18-2011, 05:00 PM - Thread Starter
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Originally Posted by kibe29 View Post
Was that thunder I just heard or just the sound from notnyt's subs making its way to me on the south shore? In all seriousness I bet it feels good to be done with the build saga and to just be able to enjoy working subs.
It's definitely thunder I'm on the south shore as well haha.

Where on LI are you?
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post #162 of 518 Old 02-19-2011, 10:37 AM
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This is great...

When the pre-post Audyssey FRs at the LP were posted, I used Ricci's GP FR and THD data to compose this approximation of how room gain reduces THD in-room.

I've been too busy to upload and post the graph and since then notnyt has posted the actual in-room 10 Hz THD data.

This is usually a very approximate exercise because room buzzing and rattling is an unknown, but it dispels the conventional wisdom that high GP THD below 20 Hz transfers to high THD in-room.

notnyt must have a very buzz/rattle free room. Nicely done.



I've done these calcs many times in my own room using Ilk's Tumult data and it never quite seemed to click with most folks, but it is simple physics and math and shows the value of the data from GP measurements exercises to real world expectations.

Now, if we had the 5-10 Hz GP data, we'd see same results or even lower in-room THD at 6-9 Hz, which is also what I've experienced with these calcs vs actual in-room measurements.

Again, awesome system. Over the years, I've gotten scads of comments like; "well, not everyone has 8-15s and tons of power", to which I reply, be patient, soon enough they will.

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post #163 of 518 Old 02-19-2011, 01:39 PM - Thread Starter
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Another THD reducing factor is he was running his driver much harder. I'm running 8 drivers at much less excursion. Here I'm power limited and not driver limited

Also, subs are closer to 4m from LP where I took those measurements
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post #164 of 518 Old 02-19-2011, 02:00 PM
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Quote:
Originally Posted by a/v HD fan View Post

Wow! Three PJs. Initially, when searching last year, I looked hard at the Pro8100 - but lots of guys were having banding issues and would exchange 3,4,5+ units til they got a good one. Did Viewsonic address the QC issues, more recently?

Sorry, OT. I've had my Pro 8100 about 6 months now. I had banding issues, but installed a timer to "disconnect" it for 4 hours every night. That solved the problem. For $1200 this is an incredible PJ. Great lens. And I only paid $1245 for my lightly used 4622's! MK was my inspiration and like James, I LOVE a bargain!
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post #165 of 518 Old 02-19-2011, 02:25 PM
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Originally Posted by notnyt View Post

Another THD reducing factor is he was running his driver much harder. I'm running 8 drivers at much less excursion. Here I'm power limited and not driver limited

Also, subs are closer to 4m from LP where I took those measurements

An opinion I've suggested for years; the Inverse Square Law becomes irrelevant at 10 Hz in most rooms. At 110 feet long, the wave has reached the boundary limits and returned (even in your 50' space) before the driver has completed the cycle of a single 10 Hz wave.

This makes it impossible to radiate as the ISL dictates.

Look at the bump in response below 10 Hz (it only rolls off below that because the input signal and amps response roll off). As you change distance from the subs to mic, you should find that the bump stays at the same level, regardless of distance.

Bosso
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post #166 of 518 Old 02-19-2011, 11:21 PM - Thread Starter
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I don't look at waterfalls too often, so I can't really compare this to anything. Is this fairly acceptable?

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post #167 of 518 Old 02-20-2011, 12:08 AM
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Looks much better than most waterfalls I've seen. You're doing great!

My Dual 18" LLT subs 120dB down to 10hz

 

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post #168 of 518 Old 02-20-2011, 02:16 AM
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Quote:
Originally Posted by notnyt View Post

I don't look at waterfalls too often, so I can't really compare this to anything. Is this fairly acceptable?


Look very good, but usually I think you set the scale to around 45db and not a high 70db on your Y scale.

But looking at the slopes I suspect that there isnt much ringing past 300ms at all, which is very good.

Must sound awesome
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post #169 of 518 Old 02-20-2011, 05:22 AM
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Looks much better than most waterfalls I've seen. You're doing great!

It does look nice but I still wonder what scales are standard for doing those? It seems every other waterfall plot has a different scale.

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post #170 of 518 Old 02-20-2011, 05:26 AM
 
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Originally Posted by a/v HD fan View Post

Wow! Three PJs. Initially, when searching last year, I looked hard at the Pro8100 - but lots of guys were having banding issues and would exchange 3,4,5+ units til they got a good one. Did Viewsonic address the QC issues, more recently?

OP, sorry for the tangent. Love the subs - would like to do something similar next year, although for budgetary reasons I'd spec the LMS-R 15" driver instead in my build, and probably only 4 of 'em.

Most of the banding problems are solved by removing power for a few hours every night by use of a timer. This projector has a great lens and throws a very nice image. I visited a guy that was using one in his room. Since I have a back up projector and could send in for repair or replacement, I decided to take a chance. I paid less than 1K for a new unit with 3yrs warranty. First year has express service. Viewsonic pays shipping both ways.

The measurements of notnyt's subs looks great. I think he is done with subs. I don't see anything that could be an improvement. Even power wise is not going to give him anything that he will be able to notice in real world use.
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post #171 of 518 Old 02-20-2011, 07:24 AM
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Originally Posted by Wrager View Post

Sorry, OT. I've had my Pro 8100 about 6 months now. I had banding issues, but installed a timer to "disconnect" it for 4 hours every night. That solved the problem. For $1200 this is an incredible PJ. Great lens. And I only paid $1245 for my lightly used 4622's! MK was my inspiration and like James, I LOVE a bargain!

i have a Pro8100. it is freakin AWESOME , for the money. i have seen $5000 projectors that could not touch this unit.

chasing rattles ......

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post #172 of 518 Old 02-20-2011, 07:35 AM
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Hey Notnyt,
How many cubic feet is that theater of yours ?

That is one impressive room. I can remember how odd the bass felt when i built my subs. I was so use to distortion. I was quite limited as far as my mains also, which you are NOT ! It caused a chain of events, like new mains, bass traps, sweeps,sweeps,sweeps galore....

They were set up and calibrated almost 8 years ago and i havent done a thing with them since....kinda sad when you build the best

Sealed subs rock !
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post #173 of 518 Old 02-20-2011, 08:11 PM - Thread Starter
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It's 25'x25' with 8' ceilings and open to another 25x25' at the back corner. You can follow the link from my sig to the construction pics.

I did some experimenting tonight with my amps, and I think I'm going to double up on them.

Two enclosures on one amp, each on a channel at 2 ohms clip the amp 3db sooner than one amp on one enclosure, running each channel at 4ohms per driver. Having one amp per enclosure also gets more power to each driver at the same signal level. I will gain the 3db headroom in clipping, then another 2-3 in extra output.

So these amps behave much better at 4ohms. I'll have to build another two relay boxes and get another pair of PDUs.
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post #174 of 518 Old 02-20-2011, 09:22 PM
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bosso...i can't follow your plot in #162. which measurements go with which colors?

"An opinion I've suggested for years; the Inverse Square Law becomes irrelevant at 10 Hz in most rooms."

as you move into pressure vessel gain the inverse square law becomes irrelevant.

this happens at about 1/2 wavelength. for a reasonably well sealed room, that will occur at 1130 f/s / (h^2 x w^2 x l^2)^0.5 all divided by 2 where h, w, and l are in feet, or more simply
565 / (h^2 x w^2 x l^2)^0.5.

for most home rooms this is usually somewhere in the 20-30 hz ballpark, but may be lower in a really big room.

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post #175 of 518 Old 02-20-2011, 09:33 PM
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"Two enclosures on one amp, each on a channel at 2 ohms clip the amp 3db sooner than one amp on one enclosure, running each channel at 4ohms per driver."

can you restate? i'm not completely following. also, what are your test conditions? pink noise, sine sweep, test tones, something else? and...watch your power. i forget how you are wired in, but a 20 amp circuit can't haul more than about 2400 watts for any duration.

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post #176 of 518 Old 02-20-2011, 09:46 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post
"Two enclosures on one amp, each on a channel at 2 ohms clip the amp 3db sooner than one amp on one enclosure, running each channel at 4ohms per driver."

can you restate? i'm not completely following. also, what are your test conditions? pink noise, sine sweep, test tones, something else? and...watch your power. i forget how you are wired in, but a 20 amp circuit can't haul more than about 2400 watts for any duration.
If I have two amps, each enclosure will be connected to each output on each amp with two drivers per amp output. Each output will be running at two ohms.

With four amps, each driver will be connected to each output directly. Each output will be running at four ohms. This gives an extra 3db of signal processing headroom as well as more output at that level.

I was testing with 10hz sine waves. These are dedicated 10 gauge circuits for these amps. I have them run through a PDU that trips at around 2800 watts.

The amps do much better at 4ohms than at 2ohms. They can deliver more overall power at 2ohms I'm sure, but at this point they're limited by the 120v outlet. Since I tried to set these to 240v and failed, I'm most likely going to just add two amps. I need to contact Marathon and find out wtf is up with the 240v setting.
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post #177 of 518 Old 02-21-2011, 06:16 AM
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Originally Posted by LTD02 View Post

bosso...i can't follow your plot in #162. which measurements go with which colors?

It's just Ricci's GP FR vs notnyt's in-room FR, from which you can use Ricci's THD data to anticipate the reduction of THD in-room and increase in dBSPL at 10 Hz.

The 3rd trace is just notnyt's FR after Audyssey.

When I first suggested the idea that the ISL ceased to apply in the PVG region, posters said I was confusing ISL with something else (I believe Seaton said something like that).

I posted this graph to illustrate:


1M vs 4M equals a drop of -12dB. My PVG begins in the low 20s Hz. This is back when I got comments that the low end was noise, HVAC, a truck passing by, etc.

Point is that every room will exhibit this phenomenon at some point going down in frequency. It's just that most measurement systems used are not accurate enough to show it.

Bosso
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post #178 of 518 Old 02-21-2011, 09:16 AM
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Originally Posted by bossobass View Post

An opinion I've suggested for years; the Inverse Square Law becomes irrelevant at 10 Hz in most rooms. At 110 feet long, the wave has reached the boundary limits and returned (even in your 50' space) before the driver has completed the cycle of a single 10 Hz wave.

This makes it impossible to radiate as the ISL dictates.

Look at the bump in response below 10 Hz (it only rolls off below that because the input signal and amps response roll off). As you change distance from the subs to mic, you should find that the bump stays at the same level, regardless of distance.

Bosso

Agreed with Bosso here. This is akin to critical distance at higher frequencies. When you are very close you still have more direct sound vs. reverberant. When you get back far enough, you have more reflected energy arriving than direct. In large rooms with very directional speakers this can be a longer distance. In a small, home listening environment this is typically 2-10', and only at higher frequencies. The same situation is in place at VLF, but you then also have the modal variations, so levels can still vary.

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post #179 of 518 Old 02-21-2011, 09:27 AM - Thread Starter
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Quote:
Originally Posted by bossobass View Post

It's just Ricci's GP FR vs notnyt's in-room FR, from which you can use Ricci's THD data to anticipate the reduction of THD in-room and increase in dBSPL at 10 Hz.

The 3rd trace is just notnyt's FR after Audyssey.

When I first suggested the idea that the ISL ceased to apply in the PVG region, posters said I was confusing ISL with something else (I believe Seaton said something like that).

I posted this graph to illustrate:


1M vs 4M equals a drop of -12dB. My PVG begins in the low 20s Hz. This is back when I got comments that the low end was noise, HVAC, a truck passing by, etc.

Point is that every room will exhibit this phenomenon at some point going down in frequency. It's just that most measurement systems used are not accurate enough to show it.

Bosso


This seems to contradict your earlier statement, as at 10hz, there is a definite difference between 1m and 4m.
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post #180 of 518 Old 02-22-2011, 01:25 PM - Thread Starter
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