JM Labs SW900 sub review




Part I-about sub woofer
This subwoofer is JM Lab’s Electra SW900. The retail price is $1750. It is a bass reflex design. It is set in a downward firing configuration. The driver itself is 13.18 inches. A 400-class A/B amplifier powers this subwoofer. I know that their web site says 250 watts, but trust me this has 400 watts of power. I know because my audio representative indicated to me that they were conservative with this number (250 watts),the amplifier is also auto on. The sub has 2 ports. The ports are 2.75 inches in diameter and are 8.26 inches in length. The cabinet is 100 liters. It has a crossover range from 40Hz-140Hz. Also, it has a variable phase control from 0-180 degrees. In addition it also contains a second level boost of 3db at 35Hz. This does not affect power handling. The rear connections consist of two filtered line input (s) (RCA)Direct input (s) for 5.1 (RCA).

It has a weight of 44Kg or 97 pounds. Its dimensions are 19.21"tall 16.92"wide 24.21"deep. The driver is made of JM labs higher end material called a W cone. Other speaker designers like to emphasize that they do not use off the shelf parts and that their drivers cost hundreds of dollars. Well, JM labs is right up there with them. This is no $50 driver. It requires 2 hours to build by hand. . The following is a direct link to learn about the technologies used The SW900 has a frequency response that is listed at 25Hz-180Hz at -3db and 20Hz at -6db (at least, 32Hz at –3dB in free space). The fit and finish of this sub woofer is really fantastic. It seems as though only the finest woods were used. To use the term “furniture grade” for the cabinet is not an understatement. One thing I like about the sub is that it is made all in house. They make the drivers. They make the cabinets. They make the crossover and amp. So for them to integrate everything together is much easier that someone who does not do everything themselves.

Many other companies source out their drivers. Jm lab does not do this. Now, are there good, well know speaker companies who make good speakers but do not build their own drivers? Yes there are. But personally I like the fact that JM creates everything themselves. Because they make the driver and cross over they can blend the two together perfectly.

R&D is a part of speaker manufacturing. Each driver built by JM is designed to be in one particular speaker only. So, if a floor standing speaker and center channel both employ a 6-½ inch woofer they will not be the same. The design will be different for both applications. In addition the majority of speaker manufacturers fold the price of research and design into the final price of the speaker. JM lab doesn’t do this. They have a totally separate budget that is just for R&D. I happen to know that it is a substantial amount of money. What this means is that when you buy this subwoofer you are only paying for the materials and the cost of assembly. The cost for the design and development of the technologies used is not factored in to the price.

Part II about room and set up
My room dimensions are L-12.5 feet W-9.5 feet, and from floor to ceiling is 8 feet. In my processor, I have the LFE channel set to -4db. I used my Krell internal test tone and set the subs level to 87db. I also have the 3db boost on the sub flipped on. The cross over cannot be defeated so I set it to its maximum and let my preamp handle everything, which in affect took the sub’s cross over out of the equation. All speakers except for the center channel were set to small. Due to room constraints the subwoofer is not located in a corner. It is located along one of the long walls about one third from the front of the room.

My Equipment consists of the following
1. Krell Showcase preamp
2. 1 Bryston 4b-ST for L/R
3. 1 Bryston 5b-ST for Center and surround
4. 1 pair JM labs 927Be for L/R (Limited run of 500 pair with beryllium tweeter)
5. 1 JM Labs CC-901 Center channel
6. 2 Polk RT-3 surround speakers
7. 1 JM labs SW900 Subwoofer
8. 1 Monster power HTPS-7000
9. 1 Monster power AVS-2000
10. Cables by Transparent Audio
11. Pioneer DV-47ai DVD player
12. Sony 34XBR800

Part III Testing with movies
My previous subwoofer was an older definitive technology power field 15. As the name implies it had a 15-inch driver with a 200-watt amp. It was good at the time, but when I got the SW900 the difference in quality quickly showed it self. When listening to the Def tech, it could shake the room with no problem. But when I switched to the JM something happened. I heard and felt real bass for the first time. What I mean is with the def tech, what I thought was bass was just distortion. The overall sound is so tight. There must be very little distortion with this subwoofer. It took me a few days to get used to only hearing bass and not the other stuff as well. But also the total volume (SPL) and extension were enhanced also. I was getting more and better bass out of a smaller driver. When I watch dvd concerts the bass is so smooth, tight and balanced that I can not tell the subwoofer is on. The bass sounds like it is coming from the main speakers only. The volume has no problem filling my room. After the sub was broken in it was incredible. I was watching the animation scene in Kill Bill. This is after I had already beaten my room up with bass. In that scene, the bass was so loud at one point it caused my blinds to fall out of the ceiling. Wow! The overall sound of this sub is just fantastic. It has no “boom” at all. Bass is just tight. Also, I cannot detect any port chuffing. The bass just sounds mean and violent.

All measurements were done with a radio shack digital SPL meter. All readings were done at the main listening position, which is at the far wall. All SPL levels are C weighted with no extra compensation. My pre amp has a starting volume of 0 for no sound. All numbers of volume are relative from that point. Volume for movies and tests were at 14 on my Krell.

Below is a chart of my in room response. In a corner I am sure that the readings will be stronger. As hard as I tried I could not fix that dip at 63 Hz. I used the parametric EQ in my Krell showcase to try and get the flattest response.

Do not pay attention to numbers below 22Hz.. My Avia disk does not go below that level. Besides that one dip, at 63 Hz the response, 80-25 Hz looks pretty good.

For the movie measurements you could add 4-5db to get an accurate reading to compensate for the radio shack SPL meter. I think it is pretty impressive for having only the 13:18 inch driver and 400 watt amp. Now I don’t believe that these measurements represent the limit of the Sub. They just represent the limit of my room. This sub would have no problem filling a bigger room. My room is so small that this is all I and my room can handle. In a bigger room I have no doubt that it could be calibrated to handle more room volume. I have heard this in a much bigger room and it still was very powerfull.

All volume is at 14 on my Krell
movies and scenes to do
open battle 95-100 db
Sauron attacks 93-94 db
Sonic wave 102 db
ring drop 94 db
Bilbo ring drop 96 db
tree root 94-100 db
Gandolf speaks at Elron 100-107 db
Giant octopus 90-96 db
troll 102-106 db
bridge/balrog 102-111 db :D

Fiding Nemo
Daria taps 103-107 db
whale 98-110 db

Kill bill
Anime Sequence (36:54-42:23) 96-104 db

Star wars I
Engine start 96-99 db
Pod Race 98-103 db
Saber battle 94-102 db

Star wars II
Coruscant Ship Passing (0:02:02) 111-114-115 db :D
Coruscant Ship Exploding (0:03:23) 111 db
Speeder Chase 101-106 db
Asteroids 104-110 db
From 110min-118min peaks from 98-110 db

Jurassic Park III
Plane crash and attack 92-96 db
Dino fight 94-97 db

Master & Commander
Opening Salvo (0:09:03-0:09:09): 99-100 db
Salvo Exchange (0:10:48-0:11:32): 98-100 db
Double Blast (0:13:21): 101, 104 db
Last Round (0:13:31): 104 db

Open Range
Opening Thunderclap (0:02:41): 94 db
Shotgun Blast In Saloon (1:12:35): 94 db
Handgun Fire (1:42:57): 88-96 db
Shotgun Blast Through Wall (1:46:50): 95 db

Nazgul Flyover (0:43:26): 104 db
Battering Ram Hits Door (1:46:45): 104 db
Oliphant Stomping (2:04:20-2:04:23): 105 db
Oliphant Stomping (2:04:54-2:04:57):106 db
Nazgul Death Throes (2:09:37): 106 db
Witch King Spike Ball Hits Ground (2:10:10): 100, 104 db
Oliphant Howdah Sliding (2:13:21-2:13:24): 101 db
Sauron Spots The Ring (2:29:05-2:29:27): 105-107 db :D
Frodo's Beating Heart (2:40:33-2:40:57): 99-108 db :eek:

So as you can see I am very satisfied with this sub. I find it a very capable subwoofer. As I said before, it sounds so smooth and tight to me. I think it is another option people should be aware of.

P.S I double checked the compensated SPL readings on the chart and found they were a little off. 22Hz should be 89db, 25Hz should be 94, 28Hz should be 98db, 45Hz should be 98db, 50Hz should be 98, 56Hz should be 96.5db. I found this out when I did the caluclations my self. I just want to try and give an accurate account. The movie SPl's are the same

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