Lava LSP12 Subwoofer Review

Lava LSP12 Subwoofer Introduction

Lava Subs are a relative newcomer to the consumer audio industry whose products are already attracting attention in various online forums. Currently, they make subs, only subs and nothing but subs.

Aiming squarely at that portion of the market populated by budget-minded folks serious about their sound, the industry veterans who make up Lava have brewed up a product line that focuses entirely on what’s important; if its not essential to the function & purpose of a subwoofer, you won’t find it here.

I was curious to see how a no-frills sub that retailed for just a bit over $300 was managing to garner the positive attention that seemed to follow it online. When Gene offered me the chance to review one of Lava’s products, I jumped at the opportunity.

The Arrival

The Lava LSP12 arrived packed in a carton within a carton within a plastic sock, further isolated internally by styrofoam blocks. The value in the obvious care Lava Subs put into packaging their products was demonstrated by the fact that the exterior carton arrived damaged but the sub itself hadn’t a scratch on it.  Included with the sub was a power cord and the usual basic documentation (also available online).

Lava LSP12 Disassembled

It didn’t take long to get it unpacked and ready for action. At right is a photo of the LSP12 disassembled with all major components displayed.

Design Overview

The Lava LSP12 is a bass reflex design featuring a nominal 12” driver, two 3” diameter ducts, and powered by a built-in 250W class AB power amp.  The driver is recessed into the faceplate and the two ducts, located directly beneath the driver, are part of (as opposed to bolted into) the faceplate.  All, of course, are front firing.  The power amp/control panel is bolted into the back of the cabinet. The cover comprises grill cloth stretched across an MDF frame.

The LSP12’s cabinet is made of .75” thick MDF panels, well glued, with plenty of glue blocks in place, but no cross bracing.  The exterior of the cabinet is covered with a lightly textured black vinyl veneer. Its not a heavy -duty grade veneer, so care in handling once you’ve got the LSP12 out of its shipping cartons is in order. The interior of the cabinet is neither stuffed or lined, though the amp/driver leads and the exterior of the two ducts are wrapped. Overall, for a product in this price range, fit & finish are very good.

The Driver

This is where Lava Subs put their money when fitting out the LSP12. The sub comes equipped with a nominal 12” driver sporting a composite cellulose diaphragm, heavy-duty butyl rubber surround, stamped frame, woven tinsel leads affixed to the spider (to minimize noise during high excursion moments) and a substantial motor structure.  The excursion capabilities of the driver were such that, the LSP12 played clean up to its respectable limits, which were substantial for a product in this price range. (See max. spl measurements below).You could push the LSP12’s gain higher and higher and eventually it would simply stop getting louder, getting progressively more distorted and annoying only at the very edge of its performance envelope.

The Amp & Associated Electronics

         

The LSP12 features a 250W rms, (500W, peak) Class AB power amp, bolted (along with all system controls) into the back of the cabinet. Control-wise, you get the bare essentials:

• Speaker, low-level & LFE inputs;
• continuously variable volume (gain) control;
• continuously variable LP filter (40 – 200 Hz);
• 0˚ - 180˚ phase control, switchable
• Off/Auto/On control, switchable
• Power switch, power/signal indicator light

The amp can also be switched to run on 110 – 120 Vac or 220 -240 Vac.

Noteworthy here is the care that’s been taken to seal off any air leaks around those points where wind noise could occur when the sub’s being driven hard. Also, there’s a substantial heat sink that’s bolted to the interior side of the control panel and wraps underneath the entire main circuit board. There’s also at the amp end of the amp/driver leads a ferrite placed to keep RFI/EMI noise down.

Listening Tests

All listening tests were done with the LSP12 integrated into a 7.1 HT system, powered by a Denon AVR and EQ’d using the Denon’s built-in Audyssey system. On the sub itself, phase was set at 0˚, gain was at 50%, and signal was fed in via the bass managed LFE jack.

The Polar Express HD DVD

This is a great HD DVD for testing out a subwoofer. Several times within the movie you’re treated to the rumblings of an old-time steam locomotive at close range. There’s lots of sustained LF energy to test whatever device you’ve tasked with handling the LFE portion of your movie’s soundtrack.

Near the top of the movie, the Polar Express makes its first appearance,

shaking everything in the vicinity with all the mechanical mass a steam locomotive brings to the party. I kept replaying this portion of the soundtrack, each time jacking the gain upward to see how loud I could

get the LSP12 before hitting its limits. What I found was that the sub could be pushed pretty hard before it drew attention to itself in a negative,

unwanted noise kind of way.  It did a commendable job of producing the low tones, though not with as much depth and visceral feel as I've experienced with pricier subwoofers. 

I was also curious to see if I could get the thing to crank out any obvious mechanical or port noises (chuffing), a common enough occurrence when a sub with a single 12” driver is pushed especially hard. What I found was, the LSP12 could be pushed hard enough to generate port noises but said noises were at such a reasonably low level that you’d only notice it if you are in the habit of spending your spare time listening to pure LF sine-wave test tones. On the other hand, if you prefer music or movies LOUD when its HT time, you won’t likely notice  much in the way of mechanical/port noises, until you’ve flat out hit the sub’s limits, as they’ll be buried underneath (masked) by everything else that’s going on, acoustically speaking.

Yes Live At Montreux 2003 HD DVD

Here we have the classic Yes lineup (Anderson, Wakeman, Howe, Squire & White) playing their first gig at the Montreux Jazz festival. In terms of dynamics, the LF content of this concert HD DVD is all over the place, no surprise, given the playlist Yes happened to choose for this particular concert. No longer listening for LF effects, I was listening for music.

Noticeable from the get go, the LSP12 did not advertise its presence or intrude when it wasn’t needed, such as during the acoustic solo pieces Howe did mid-concert or some of the more acoustically oriented tunes sung by Jon Anderson. Not all credit goes to the LSP12 of course, as the Audyssey system did a fine job of EQ’ing the entire system.

Owing to its bare-bones complement of controls, you’ll need to spend some time tweaking/integrating/Eq’ing the sub with whatever upstream electronics you have at your disposal to get out of it the best performance it's capable of.

Favorite sub-friendly tracks here? Siberian Khatru, Heart of the Sunrise and Long Distance Runaround, all three tracks underpinned by Chris Squire’s ever-melodic bass lines and Alan White’s solid drumming. Especially interesting here was the jam between Howe, Squire & White in the middle of Long Distance Runaround, where the LSP12 handled all the heavy stuff expertly, yet had sufficient finesse to keep all the low-level detail in the quieter passages clean & focused. Very impressive for a sub retailing at just over $300!

Lava LSP12 Subwoofer Measurements and Analysis

 

Impedance / Phase Measurements of the LSP12 Driver/Cabinet & Driver

Parameter	Value
Revc (Ω)	3.620
Fo (Hz)	30.66
Qts	0.441
Vas (ltr)	55.21
Mmd	175.760
Efficiency (%)	0.321
Sensitivity (dB)	87.082

T/S Parameters  

Measuring both the driver (left) and driver/cabinet (right) native impedance produced the graphs showing above. Both curves provide useful information helpful in assessing a sub. From the driver’s curve comes the collection of T/S parameters, in the table shown above right as well other clues to construction along with indications of any pathologies or anomalies, such as unwanted, excessive mechanical vibration. (Judging from the curve, there wasn’t any). From the system’s impedance curve we see the native resonance frequency (~ 48 Hz) sits at the impedance minimum (4.63 Ohms) located between the two LF peaks. With a minimum of 4.63 Ohms this sub would be classified as a 6 Ohm system.

We also note no signs of unwanted acoustical or mechanical resonances reflected back to the electrical domain, which would typically show as modest-sized impedance peaks located at random point(s) along the impedance curve.

 Amplifier Output amplitude response (Vac) with LP filter set at 40, 120 & 200 Hz;
LFE Input (Left). Low Level Input (Right)

Before moving on to the acoustical measurements, a quick assessment of the electrical behavior of the sub was done. At left we see the sub’s electrical response when fed a test signal to the LFE input (Left) and Low Level inputs (right) and the LP Filter’s frequency was set at ~40, 80, 120 and 200 Hz. As you can see, the filter has no effect on the LFE output, but significantly changes the system’s response when the signal was fed the Low Level input.

Near-field amplitude response (dB spl) scaled to 1m, Sub gain @ 50%
Test signal fed to LFE input (left) and LL input (right). Purple curve = 200Hz, Red curve = 120Hz,
Green curve = 80 Hz, Blue curve = 40 Hz.

Above left is the amplitude response (dB spl) of the LSP12 when fed a test signal directly to its LFE input, measured near-field. Above right, we see the response of the system when fed the same signal, this time to the Low Level input. As noted in the electrical measurements made above, the LP filter effects the systems output only for those signals fed the Low Level input.  Looking at the driver-only NF dB spl plot, (generated with built-in power amp engaged) the system seems to be tuned to ~44 Hz.  It is our opinion based on the impedance measurements above that this system was tuned too high yielding impressive output above its tuning frequency at the expense of severely limiting extension.  As a side note, I worked up some quick model’s of a theoretical system based on the driver's T/S parameters and found I could get a most impressively flat response using a Cheby/Butterworth alignment and tuning the system to ~ 26 Hz.- all done with an unlined cabinet sporting a net vb of ~ 2.3 ft^3.

      

In-room Groundplane Frequency vs SPL(dB) Plots
2m, mic calibrated, center room (left pic);  1 m, corner loaded (right pic)

The amplitude response plots were run in room using the groundplane measurement technique.   The above left plot was taken at 2 meters, with the collected measurement data equivalent to 1m free-space. The sub was placed well into the room for this round of measurements. I used a mic calibration curve I devised to completely remove the room effects to get as close to possible measurable results to what one would see outdoors using a similar measuring technique.  At the time of measuring this sub, the weather in Canada was simply too cold to bear.

The gain of the test signal (sine wave) fed the subs LFE input was increased 3dB each sweep. The sweeps were repeated until any sort of obvious compression/limiting appeared or the sub got distorted/noisy owing to mechanical/electrical stress was noted. The spiky appearance of the curves below 20 Hz is due to random environmental noise and can be ignored. The amplitude response plots seen in the left hand graph are not smoothed; rather, a mic calibrated to eliminate room effects for use in this particular room was employed.

The above right pic is the resulting response plots with the sub now parked in a corner. Gene suggested measuring the sub at 1m, ground plane, using a mic not calibrated to remove the room’s effects, for comparison purposes. In this case, the room’s acoustics are affecting the measurements. Room gain does help provide more extension to this sub, but its bass response below 40Hz is still rather limited.  Sweeps were once again repeated with the gain increased 3dB each time, until the sub became obviously noisy. No equalization was used in generating any of the plots showing in either the left- or right- hand graph.

Mic Calibration Comparison

The green plot is the response of the test subwoofer as measured in the room with no custom calibration data used. The blue plot is the reference standard that is known accurate to a fraction of a dB. The red plot is the same subwoofer, measured indoors, under conditions identical to those in place at the time the green response plot was generated, but with the room effects calibrated out.

Editorial Note About Mic Calibration

Calibrating out room effects requires clean dB spl reference response plots, the original device used to generate the reference response plots and meticulous attention to all details. Essentially, you compare measurements done in-room with the clean reference measurements and build a conjugate of the difference between the two. Add this to your mic’s calibration file and you have now calibrated out the room effects. Measure with full attention to the details (example: if you built the conjugate with in-room measurements done while the room’s doors & windows are shut, then you’ll need to keep all the doors & windows shut during any subsequent measurement sessions using the new mic calibration file.

While the Lava LSP12 displayed respectable output above 35Hz, it's hard to ignore the output advantage of the smaller, and only slightly more expensive Emotiva Ultra 12 subwoofer, especially at and below 30Hz.  If you scale up our 2 meter calibrated GP measurements of the Lava LSP12 sub to 1 meter and directly compare them to Gene's Emotiva Ultra Sub 12 measurements its clear to see the Emotive Ultra 12 subwoofer has about an 8dB output advantage at 30Hz and a whopping 20dB advantage at 20Hz.  The reader must decide if the additional $100 or so for the Emotiva is justified by its measurably better performance. 

Recommendations

Below 35Hz, the Lava subs measured response drops off pretty quickly. If you’re interested in wringing out every last drop of LF performance your sub and room are capable of, use your AVR’s bass management system. You will want to place the LSP12 in a corner; room gain and EQ’ing are essential if frequency-wise you’re hoping to hit the lowest portions of the LSP12’s output. One may just do the trick for you, but get two and really have some fun.

Lava LSP12 Subwoofer Conclusion

When Gene first offered the opportunity to review the LSP12, not knowing much about it (other than its retail price) I was quite prepared for or rather anticipated a ho-hum performance from a ho-hum product.   In fact the LSP12 was quite the pleasant surprise, to the point I was continually impressed by the performance of this no-frills budget product. So what don’t you get with the LSP12?  Besides NOT getting  the heavy price tag, you are also NOT getting the extremes of envelope-pushing performance, especially in terms of the extreme low-frequency output you may get from more expensive subs populating the marketplace.  The LSP12 certainly has its limits, but within those limits, it performs quite well.

  Lava LSP12 Subwoofer Review
MSRP: $338.46

Lava Subs
 http://www.lavasubs.com/
877-750-LAVA (5282)

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Bass Extension
Bass Accuracy
Build Quality
Appearance
Dynamic Range
Performance
Value