Mark_B

How do you tell if a Sub is good?

I have recently upgraded my HT system with a new amp and speakers. The only one left is the sub, but I'm not sure what I got. I purchased this sub off of Ubid.com 4 or 5 years ago and never gave it much thought. It is a 10 inch solidly built down firing sub. It was originally part of a whole HT in a box from Hitachi. All I wanted was the sub and at the time it was a good price. Anyway, before I go out and find something new, what can I do to measure the performance of this? To me it sounds good, but maybe because I have never heard a good one I'm in the dark. I have the Avia calibration disk and the RS spl meter. I listen to the tones but don't understand what I'm trying to hear. Maybe someone can give a simple explanation of what to look for. Maybe I don't need one.

Thanks.

SethH

Do you have the specs on the sub? Specs are often very telling about a subs performance. You could use the frequency sweeps on the Avia disc and see where the response really starts to drop off (using the SPL meter). A good sub (<$450) would be one that holds on down to about 25-30Hz. A better sub should hang on down to <20Hz.

I'm guessing that your sub could use an upgrade as most that come in HTiB systems aren't very good.

Another option, if you've got a laptop (or a desktop nearby your system), is Room Wizard EQ. That program allows you to play test tones at certain fequencies and will also graph the frequency response of your sub in your room.

Mark_B

Sorry, no specs on the sub. Searched the web and couldn't find any either. Not exactly sure what you mean by "drop off" Are you talking about the acutual DB reading? If I get this right, start the tone sweep at a certain level say 75db and watch where the volume on the spl meter drops. How much is acceptable? What should the meter look like as the sweep is occuring? Unfortunatly, I have read these terms but really never understoood exactly what they mean. Also, when they talk about it being flat, what does that mean.

Thanks for the help.

John Garcia

You would set the sub to a know average SPL level, the 75dB (calibration) with white noise. Then you measure the sub's response across a set of frequencies and plot the performance. This will show you where the sub rolls off at the bottom and any dips/peaks in response (most often room related). drop off would refer to the point at which the sub cannot reproduce the lowest notes; the lower the better usually.

"The trouble with the world is not that people know too little, but that they know so many things that ain't so." - Mark Twain

HT: Marantz SR-8300, MA500 monoblocks x 2, 5X GR Research A/V-2s, Adire Audio Tempest sub, Denon 2900, Oppo 980H, Toshiba HD-A2, RC2000MkII remote, Panamax 5100, Panamax Max2 sub, Slim PS2, PS3 60G + 320G USB

Bedroom: Marantz PM-7200 Integrated, GR Research A/V-1s, Sony 222ES SACD, RC3200 remote, Panamax M8EX

Audio: Audioquest * Video: Bluejeans

My DVDs My HT

Jeff Gatie

Basically correct, except you would nees to play a "frequency sweep" tone that goes from high (~150 Hz) to low (<20 Hz). Look for the point where the SPL drops off significantly and also watch for fluctuations (especially humps) around certain frequencies (40-50 Hz). Poor performing subs sometimes try to make up for low performance by boosting the 40-50 Hz region, often refered to as "boomy" or "bloated" bass.



A "flat" frequency response means the output (high output, that is) is the same across the effective frequency range of the sub. Example: 95dB from 16Hz - 180 Hz +/- 3dB means the average output of the sub is 95dB from 16Hz to 180Hz differing by +/- 3 decibles at the most. The +/- 3 dB is important, without it frequency response means nothing. Many sub manufacturers will list freq. resp. without the +/- 3dB or average output, which means the output at 16Hz could be 90 dB lower than at 50Hz, but you still get a noise, so they can list it as starting at "16Hz".

Quite the opposite of flat is the "bloated" bass mentioned above, which artificially increases the bass in the 40-50 Hz region. Basically, the flatter and lower a sub goes, the better the sub.

ColinM

Put on a Telarc CD that has Also Sprach Zarathrustra, or 2001: Space Oddysey, opening track. If you can hear the opening tone distortion free, I believe it is a 30hz organ pedal.

When I do that on my $230 DIY, cranked, I fear structural damage to the house before anything else.

You call that a knife?

Mark_B

Well I ran the sweeps last night and I guess it isn't the best sub in the world. The Avia sweep starts out at 160Hz. I first set the sub at 75 from the white noise where you match the level to your mains. I then started the sweep and the db ran above 85 for a little bit, slowly trailed off and then jumped at about 110, stayed about the same down to about 80. It then started to fall and then jumped way high, almost 10 db between 40 and 50. At 40 it started to drop off again. What surprised me is that it didn't lose sound completely until about 22. I still had readings in the 70's between about 28 and 35 with the big dropoff at about 30. It jumped around a lot during the sweep with no real lows, but a lot of highs. No matter where I set the level, I could not keep the readings on the same scale on the spl meter. I started on the 70 scale. I switched to the 80 scale and during the highs, that was almost pinned. It just kept jumping back and forth. I kind of blew my budget on the other speakers, so maybe I'll look into getting a Dayton sub. From what I have read here, they look like they can hold there own.

Thanks for the input. I learned a lot.

SethH

Yeah, you might consider the Dayton, but it may not be worth it. Most reviews I've read have the Dayton dropping off pretty hard around 30Hz, so you may not get a drastic improvement. However, it may be a better quality subwoofer and may just sound better.

ColinM

"No matter where I set the level, I could not keep the readings on the same scale on the spl meter."

Not uncommon. Perhaps look around for a used 31-band EQ. Music stores have them all the time, $40 or so. Use it to flatten the peaks as best you can, and maybe bring up the bottom end just a bit.

You'll use it with the next sub you get anyway, if you want to optimize your bass somewhat.

Check out the Rives site - there's a room sim that will show you approx. what the bass response curve looks like. Using EQ will improve the bass.

You call that a knife?

Jeff Gatie

Mark, a lot of what you are seeing may be room dynamics, which can play havoc with frequency response, but I think your hump at 50->40 Hz is most likely the "bloat factor". This gives a sub the "boom boom" that people who do not know bass think they are looking for. A quality sub will not have this and some even miss it when they first hear a good sub, but once you tune your ear to the flat/low response, watch out: If the lows are there, they are played with gusto.