[chargedmr2]

Hi guys,

Quite some time ago I asked Jim if he would build me a custom subwoofer.  It had to meet my wife's approval which meant that it would double as an end table (no dedicated listening room for me).  At first I wasn't sure exactly what I wanted, but I settled on a design to accommodate the LMS Ultra 5400.  Jim was very helpful and built the sub just as I needed for our space (I think we exchanged more than 100 emails!).  I have not been able to get the sub fully integrated yet, but so far, I am very impressed.  This thing puts out very very CLEAN bass.  I will be applying EQ to flatten the response in the near future, but even as it is, the difference is quite noticeable with music and especially movies (in fact, I am now on the hunt for room rattles that need to be eliminated).  After I get it well integrated with my SongTowers, I will post back with some more detailed impressions.  For now, I figured I'd post a few pictures and mention some of the details about the sub design:

Dimensions: 21x21x25 (including spikes)
Weight: 209lbs (I actually weighed this beast on our scale)
Volume: 3.3 cu ft
Finish: Ziricote with Ziricote hardwood inserts on all four vertical edges
Base: 3/8" steel plate powder coated black (thanks to Oregondv who did the metal work)
Binding posts: Jim's Cardas premium posts (bottom mounted for discrete look)

And the pictures from arrival to getting it into place...

I was at work, but the driver agreed to leave the delivery in front of the garage.


I dragged the pallet into the garage for unpacking.


Almost there!


And the fist glimpse (all Salk owners know that Jim's work must been seen in person for full appreciation).


I placed some styrofoam back on for protection and rolled it in with a dolly.


And here it is on its side awaiting spike installation (notice the binding posts).


And finally, here it is in its final place.

[Nuance]

That's one of the nicest subwoofers I've ever seen!  You have a beautiful home as well, by the way.

What will you be using to apply PEQ to the subwoofer?  Do let us know if we can help out.

[chargedmr2]

Thanks Nuance.  Jim really does very nice work! 

I'm not sure what to use for EQ.  I was thinking about a balanced miniDSP but I'm not sure if that's the best option.  I read (on another forum) that it may clip the input signal if you're dealing with a hot sub out, though I think my AVR will be OK with it.  What do you use/recommend?  I'm hoping to creat a flat response that goes pretty low. 

[coke]

I noticed you mentioned room rattles in your post. In my exprience, when room rattles are easily heard over the bass, it can sometimes be a sign of cancellation issues.  Try a few different placement options........ if you're allowed 

[jackman]

I would pick up one of these to power your sub.  You can also get a pro amp with built in EQ and Xover from Crown or several others.  Pro amps work great for sub applications, lots of power and low cost.  Fan noise is a problem for some but the PE amp does not have a fan.  I'd get the PE amp.  There are more expensive options but I think they might be overkill.

http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-811

[chargedmr2]

I noticed you mentioned room rattles in your post. In my exprience, when room rattles are easily heard over the bass, it can sometimes be a sign of cancellation issues.  Try a few different placement options........ if you're allowed 

Well, as you might imagine, the bad news is that placement alternatives are not an option.   But the good news is that the rattles are not heard from the LP, but when I get up and walk around the room.  Even better, I've determined that the rattle is coming from one of the HVAC vents in the ceiling.

[chargedmr2]

I would pick up one of these to power your sub.  You can also get a pro amp with built in EQ and Xover from Crown or several others.  Pro amps work great for sub applications, lots of power and low cost.  Fan noise is a problem for some but the PE amp does not have a fan.  I'd get the PE amp.  There are more expensive options but I think they might be overkill.

http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-811

I've already got the amplification taken care of (a true 2.4Kw RMS), but I don't have an amp with DSP built in (which may have been a nice option).  And I agree with you that it's overkill for average use, but its definitely not overkill for the sub, which can easily take everything this amp has.  I really wanted to be sure that there was plenty of headroom (at reasonable movie watching levels) for EQ to remedy the below 30Hz roll-off.  For music, there is plenty of bass and after getting this sub, I'm reminded of how well the SongTowers do all on their own in the low frequency region.  So far, I still prefer the SongTowers without sub for two-channel listening.  Once I get the sub properly integrated (within my limits), I'll reevaluate. 

[Nuance]

Thanks Nuance.  Jim really does very nice work! 

I'm not sure what to use for EQ.  I was thinking about a balanced miniDSP but I'm not sure if that's the best option.  I read (on another forum) that it may clip the input signal if you're dealing with a hot sub out, though I think my AVR will be OK with it.  What do you use/recommend?  I'm hoping to creat a flat response that goes pretty low. 

Based on what you said about clipping the input signal I have an option for you but it'll require having the necessary tools to measure your room.  If you're cool with that I highly recommend the Behringer DSP1124p.  It's ugly as can be, but if you hide the thing it's probably the best option for the money IMO.  You can even use it to set the input level on your receiver so you never clip the signal.  Again, though, you'll need to have a mic and soundcard paired with software (like REW) to measure your room first.  If that's something you're not willing to venture then the miniDSP is a great option.  I don't know that you'll be able to use it to adjust the input level on your receiver, though.  The reason you can use the Behringer to adjust the input level of the receiver is because it has the meters on the front, and before you apply EQ you put it into a bypass type mode in order to display the receiver's input signal. 

Regarding integrating the subwoofer, taking in-room measurements will be a great asset.  I used my ears and REW to integrate my subs and couldn't be happier.  With that said, being placement limited is definitely your Achilles Heal.

[chargedmr2]

Based on what you said about clipping the input signal I have an option for you but it'll require having the necessary tools to measure your room.  If you're cool with that I highly recommend the Behringer DSP1124p.  It's ugly as can be, but if you hide the thing it's probably the best option for the money IMO.  You can even use it to set the input level on your receiver so you never clip the signal.  Again, though, you'll need to have a mic and soundcard paired with software (like REW) to measure your room first.  If that's something you're not willing to venture then the miniDSP is a great option.  I don't know that you'll be able to use it to adjust the input level on your receiver, though.  The reason you can use the Behringer to adjust the input level of the receiver is because it has the meters on the front, and before you apply EQ you put it into a bypass type mode in order to display the receiver's input signal. 

Regarding integrating the subwoofer, taking in-room measurements will be a great asset.  I used my ears and REW to integrate my subs and couldn't be happier.  With that said, being placement limited is definitely your Achilles Heal.

Thanks for the advice Nuance.  I will look into the DSP1124p and get back with questions (which I'm sure I'll have).  I have measurement gear (Tascam 144, mic calibrated to 5Hz, REW, SPL meter), so I'm good to go there.  Yeah, in my situation, the best I can do with placement is move the sub a few inches forward or backward, or rotate it in any direction (sad, I know).  And just maybe I can work in some room treatments. 

[Nuance]

Thanks for the advice Nuance.  I will look into the DSP1124p and get back with questions (which I'm sure I'll have).  I have measurement gear (Tascam 144, mic calibrated to 5Hz, REW, SPL meter), so I'm good to go there.  Yeah, in my situation, the best I can do with placement is move the sub a few inches forward or backward, or rotate it in any direction (sad, I know).  And just maybe I can work in some room treatments. 

If you already have REW set up and ready to go then using something like the 1124p to apply PEQ and set the input level of your receiver will be a piece of cake.  I am here to help if you have any questions.

[chargedmr2]

Hey Nuance,

Can the 1124p be used to adjust below 20Hz?  I'm sure this is not a huge issue, but I'd like to get everything I can out of this sub for HT use.  Now that I think about it, I'm not sure if the miniDSP can do this either?

[Nuance]

Hey Nuance,

Can the 1124p be used to adjust below 20Hz?  I'm sure this is not a huge issue, but I'd like to get everything I can out of this sub for HT use.  Now that I think about it, I'm not sure if the miniDSP can do this either?

Neither can, no.  Room gain should easily get you flat to 15Hz, though, if not lower.  Have you measured the room/sub yet?  If so, do you have issues getting below 20Hz?

[TJHUB]

I have a pair of 18" LMS Ultra subs, and they tend to roll off a little above 20Hz.  I use an 1124P to EQ them, and I use a wide 20Hz filter to boost them.  I'm flat to about 14Hz.

[chargedmr2]

Nuance, TJHUB -

Thanks for the replies.  I have to take some new measurements since I wasn't clear on how the "direct" mode works with Denon AVRs.  I believe I had "double" bass going on (Denon seems to ignore all base management for the mains in this mode).  The initial measurements were certainly not flat under 20Hz (or anywhere else for that matter!).  There seems to be some roll-off that starts at about 30Hz in my room. 

However, if I can get flat to 15Hz or so with the 1124P, then that should probably do it.  I don't think I can expect anymore than that without going to dual (or more) subs. 

Do you guys have any noise issues with the 1124P?  Does it produce a pretty clean signal?

[Austin08]

From your pictures, look like the sub is right next to you. You should have a very nice measurement curve. Hum,  did you try to move your sofa a bit and see if thing get smoother.

[Nuance]

The 1124p is nice and quiet in both my and TJ's system. Post up some measurements when you have a chance.

[chargedmr2]

Austin -

I can't move the couch too much, maybe about 6" further back.  I'll try to measure around the LP to see what I get and then decide if it's worth moving.  Or were you suggesting to get some more space between sub and couch? 

Nuance -

Great to hear that noise isn't an issue.  I'll try to get some measuring done tomorrow and will post up the findings for advice. 

[Nuance]

Austin -

I can't move the couch too much, maybe about 6" further back.  I'll try to measure around the LP to see what I get and then decide if it's worth moving.  Or were you suggesting to get some more space between sub and couch? 

Nuance -

Great to hear that noise isn't an issue.  I'll try to get some measuring done tomorrow and will post up the findings for advice. 

6 inches can make or break a response in some cases.  Have fun experimenting, and I look forward to seeing your measurements. 

[Austin08]

Look like EQ is your best option since sub placement and moving furniture is limited. Be careful, EQ is a great tool in your case but too much EQ do more harm than good. I just ran across a thread from Brian of Rythmik and though it is a very interesting find.

Dynamic EQ

I have another customer, Jack, has a FV15HP-550 and he cannot even play his past -30db without the sub generating sound like it is bottoming out. He traced the problem to DynamicEQ and his AVR is Denon2310.

Here is the problem of DynamicEQ. DynamicEQ is implemented in DSP (digital domain processing). It has a fixed number of digits in the digital domain (whether it is crude 16bit, or more advanced 24bit, or the ultra high resolution 32bit), the objective is to make best use of the more significant bits. If we say don't use the top 3 bits in a 16bit digital system, we literally degenerate the system into a 16-3=13bit digital sytem which is not good. So we need to know the fact that the more significant bits are already being used. Next, dynamicEQ is implemented in digital domain processing, not analog domain. If we boost the signal in digital domain, we need to increase the digital representation of the signal. In another words, we multiply the signal by a factor. If we multiply by a factor of say 4x (which is 12db), that shifts the number upward towards the MSB by 2 bits. The risk of such operation is "over-flow". Over-flow is the MSB are truccated. Signal reversal is common in this case. That is different from analog clipping which is saturation (not signal reversal). So in short, it is not a wise thing to do. Increasing the sub channel level is far less problematic because it is done by a digital potentiometer and it almost achieves the same result.

So in short, if you don't have to turn on DynamicEQ, please don't. Why, one may ask, the problem was not a problem on El cheapo subs? Because those subs have limited resolution, it sounded broken already. Any additional anomaly will be masked (vastly).

After Jack fixed the problem (along with other problems he also uncovered in this process), he is now able to play THX Life test at reference level and the entire room feels like the epic center of the earthquake when the mushrooms is on the screen.

[underdawg]

very nice, looks like high end furniture