No product recommendation is perfect. While most of our testing takes place in our own homes, everyone’s setup is different. As a result, the product you install in your house might not live up to the standards of the sample we tested. However, if we encounter complaints about a product, we investigate them to see if we need to adjust our recommendations. The most recent example of this pertains to the Monoprice 9723 subwoofer featured in our guide to the best budget subwoofer.



You can see the complaints about the 9723 outlined toward the end of this thread on Slickdeals. Some users report receiving scuffed or damaged units, and some complain that the subwoofer produces inadequate volume or excessive hum. Such reports led us to speculate that we had received a review sample that had been cherry-picked or somehow adjusted for better performance.

To find out how our review sample compared against a purchased sample, I asked a friend to buy a 9723 and put it on his credit card that so Monoprice would have no way of knowing that I would be testing the unit. The purchased sample arrived in new condition with no damage, although I did note that about ¼ inch of the black vinyl covering had peeled up slightly on one corner (something I could easily fix with a dab of Elmer’s glue).

I then ran a frequency-response test on both samples. This test shows the level at which a subwoofer reproduces different frequencies of sound; it’s the most commonly used test of a speaker’s quality. I set the controls on both subwoofers identically. The results (in the chart shown above) revealed that the output of the purchased sample matched that of the review sample almost exactly, with a maximum error of 0.57 decibel. To put that figure in perspective, moving your head 3 inches to the left or right might produce a similar difference. I didn’t encounter abnormal hum levels when testing either sample.

To see how the 9723’s volume compared with that of other subwoofers under real-world conditions, I set my Denon A/V receiver to play the test noise for setting subwoofer level, after which I used an audio-spectrum analyzer to see what level the 9723 achieved compared with two other, much more expensive subwoofers I had on hand: NHT’s $650 CS-10 and PSB’s $1,500 SubSeries 450. I set the level controls on all the subwoofers halfway up (that is, the 12 o’clock position), and I measured all of these results from my listening chair.

As you can see in the chart above, the 9723 predictably didn’t have as much low-frequency response (i.e., below 50 Hz) as the more expensive subwoofers. However, its response in the range from 50 to 100 Hz, which is where most of the bass content in music and movies resides, was on average 2.4 dB lower than that of the PSB model and 6.7 dB greater than that of the NHT model. Thus, the 9723’s output at a typical volume setting seemed to be in the same ballpark as the other subwoofers'. I made these measurements using the subwoofers’ line inputs; through the speaker inputs (which aren’t included on the NHT), the PSB unit’s level was 7.4 dB higher than the Monoprice’s. These variances are normal, and you can compensate for them easily by using the level control on the subwoofer or the channel level control in the receiver’s setup menu.

Considering the purchased sample's closeness to the review sample in tests, the fact that none of the three samples of the 9723 I’ve tried (including the sample I tested for About.com Stereos) had hum problems, and the evidence that the 9723’s output level under normal use is comparable to the output level of other subwoofers, it seems likely that some buyers may have received lemons and should contact Monoprice customer support. However, at least some of the performance complaints might be due to improper setup (which we address in our original review and again in more detail below).



Fixing volume and hum problems

Because the samples we tested delivered volume similar to that of other models we had on hand, the problems that users are reporting might be due to the fact that in a typical audio/video system, two controls govern subwoofer level: one on the subwoofer, and one built into an A/V receiver’s setup menu.

When using a subwoofer with an A/V receiver, start with the subwoofer’s level control halfway up and the receiver’s subwoofer level setting at 0 dB. If you start with either control turned down, it may result in inadequate level from the subwoofer. If setting the sub’s volume halfway up doesn’t give you enough volume, try turning it up to about three-fourths (3 o’clock), and then fine-tune the level with the receiver’s level control.

If you have to turn up the level on the subwoofer past halfway, don’t worry about it: Like practically all powered subwoofers, the Monoprice 9723 has an internal limiter that will protect the driver and amplifier. Unless you’re hearing gross amounts of distortion, there’s no problem.

Hum problems are common with subwoofers because the subwoofer is often plugged into a different AC outlet than the rest of the audio/video system. If the two outlets are on different circuit breakers, a “ground loop” can result, which produces a 60Hz hum. This effect can crop up with any subwoofer.

You can check a few things, however. First, check the audio connection between the subwoofer and the receiver; a damaged or partially disconnected cable can produce hum. The next solution is to try plugging the subwoofer into a power strip shared by the rest of the audio/video system. Even if this isn’t a permanent solution for your setup, it should at least narrow down the culprit.

A damaged or partially disconnected cable can produce hum.

If you continue to have problems, or if it’s impractical to plug everything into the same outlet, try using an isolation transformer on the cable going from the receiver to the subwoofer.

And in case you’re reading this because your own, non-Monoprice sub is having problems, note that some inexpensive subwoofers (but not the 9723) have AC cords that you can reverse. In this case you can try pulling the cord out from where it connects to the subwoofer, flip it 180 degrees, and reinsert it.



What Monoprice has to say

We also asked Monoprice to comment on the 9723 situation. Here is the company's response:

Our team here at Monoprice has looked into the customer concerns with the 12-Inch 150-Watt Powered Subwoofer, Black, 9723 – most of these comments we have received were due to people not realizing the physical dimensions of the unit and we have happily refunded or exchanged all customer queries. Since 2012 this piece has maintained a 4.5 star rating with 77 reviews on our website and a 4.3 rating on Amazon. Monoprice takes any performance issues seriously and works diligently to identify and correct the root cause. We are continuing to look into any additional concerns to address them quickly and ensure the best customer experience.

Unfortunately, Monoprice’s response doesn’t directly address most of the complaints, but it does raise a couple of important points:

The vast majority of user reviews on Amazon and on Monoprice’s site are positive. The subwoofers (like almost all audio products) do come with a warranty, and Monoprice will replace defective products or those that do not meet the customer’s expectations.

Of course, we can't verify the condition or performance of every sample of a product that a manufacturer ships, and neither can we verify that users have set up their subs correctly, or even that a reviewer doesn’t work for a competing manufacturer or a retail dealer that sells other brands. While we will continue to monitor user complaints regarding the 9723, we have not found sufficient reason to withdraw or modify our recommendation, especially considering this model's unmatched price-performance ratio, as well as the fact that the vast majority of user reviews remain positive and all three units we tested worked great. If you’re still having problems after trying the tips above, you should speak with Monoprice customer support at 877-271-2592.

(Photo and results charts by Brent Butterworth.)