How Audioholics Determines Bass Output Ratings in Subwoofers

[admin]

As part of our new powered subwoofer measurement protocol, we will be offering a room size recommendation for each subwoofer tested based on the data gathered from our exhaustive CEA SPL vs frequency and distortion output testing. It is our hope that the methodology we chose in determining the room size capability for subwoofers can be a useful general rule of thumb for an end user attempting to determine which model is right for their listening space. We always recommend multiple subwoofers for more overall output and smoother bass response from seat to seat. The goal for a great A/V system is lots of clean output and a similarly good listening experience for all listening seats in the room, NOT just the money seat. See if your favorite subwoofer will get our "Bassaholic" recommendation.

Discuss "Audioholics Subwoofer Room Size Rating Protocol" here. Read the article.

 

[gene]

no comments on this thread. really??? Where are all the sub enthusiasts and critics when you need them ?!

 

[Adam]

I don't need any recommendation. My SVS, and all SVS's, are perfect and therefore suitable for any room size - from broom closets to football stadiums. You could have saved a lot of time typing by just writing, "Buy an SVS."

Hey, you asked where the "enthusiasts" were.

Actually, I started reading that last night but was just too tired from work to get very far into it. I'll definitely be reading that this week, though. Thanks for putting all of that together!

 

[shadyJ]

In that "Minimum Targeted Subwoofer Output Criteria vs Room Size" table, are those numbers under the column of "RL SPL Output @ 4 meters" actually 1 m groundplane measurements that you need to achieve your target reference level for each room size? Overall I think the system looks very reasonable. One thing that should be said is that most subwoofer owners would never drive their sub to your target reference levels, and you might want to explain more what 115 to 121 db actually means, so sub owners and prospective sub buyers don't think their sub is worthless if it can't actually hit that mark.

 

[kevon27]

Ah, can you redo this article and dumb it down about 10 notches.. Just too much math and numbers..

 

[gene]

In that "Minimum Targeted Subwoofer Output Criteria vs Room Size" table, are those numbers under the column of "RL SPL Output @ 4 meters" actually 1 m groundplane measurements that you need to achieve your target reference level for each room size? Overall I think the system looks very reasonable. One thing that should be said is that most subwoofer owners would never drive their sub to your target reference levels, and you might want to explain more what 115 to 121 db actually means, so sub owners and prospective sub buyers don't think their sub is worthless if it can't actually hit that mark.

The #s are taken from 2 meter GP data and scaled to 1/8th space (corner loaded) 4 meter. Thus our assumption is the average listener will corner load their sub and sit about 4 meters from it in the room.

115dB is a peak reference level intended by the recording studio. It can go as high as 123dB if all speakers are set small while all channels are at fullscale. This is very unlikely however. If a sub can't hit the 115dB reference then its suited for a smaller than "Large" room unless you use multiple subs and factor in the added gain which we will also tabulate.

 

[mike c]

well, i didn't know there was a thread/article like this.

1) the use of the term "bassaholic" to describe room size might be confusing? if i was really a bassaholic, i'd like to setup an HT in the toilet to maximize room gain.

2) there should be a chart/link to your CEA measurements of different subs. aside from your measurements and ilkka's ... are there other people who measured CEA for subwoofers?

3) since the conclusion of the article assumes corner loading (im sorry if the article discussed the other numbers) if 1/8 free space = +6db ... what is quarter space (front and center of the room) and half space (away from walls) equivalent to in +db
[the chart seems to allude that corner loading is +18db?]

 

[gene]

well, i didn't know there was a thread/article like this.

1) the use of the term "bassaholic" to describe room size might be confusing? if i was really a bassaholic, i'd like to setup an HT in the toilet to maximize room gain.

The idea is more about the output level achieved being above reference designating Bassaholic. I based it somewhat loosely on Ultra2 Spec which is 115dB into a 3,000ft^3 room though the THX spec is much easier to meet than ours b/c they test the sub at a much closer distance and don't have such a tight tolerance down to 25Hz as we do.

2) there should be a chart/link to your CEA measurements of different subs. aside from your measurements and ilkka's ... are there other people who measured CEA for subwoofers?

There will be once we start posting reviews.

3) since the conclusion of the article assumes corner loading (im sorry if the article discussed the other numbers) if 1/8 free space = +6db ... what is quarter space (front and center of the room) and half space (away from walls) equivalent to in +db
[the chart seems to allude that corner loading is +18db?]

I am calling corner loaded 1/8th space which in theory gives you +18dB of gain assuming the walls are infinitely long. In a real room the gain would be less, more like +9 to +12dB like I stated in the editorial note. However in a real room sound doesn't fall off 6dB per doubling of distance, more like 3-4dB.

Look at the Acoustical Load chart I posted which gives theoretical gains compared to freespace for each scenario. 1/4th space is +12dB compared to freespace.

1/8th freespace (corner loading) at 4 meters is +6dB hotter than 2 meter half space (groundplane) in theory of course. That is the conversion we are using to make the assumption of subwoofer location and distance to the listener when translating our CEA data to our room size calculator.
__________________

 

[sholling]

no comments on this thread. really??? Where are all the sub enthusiasts and critics when you need them ?!

I'll bite. I think it's an absolutely wonderful idea. The only caveat is that it be a realistic number and preferably rated with both a subwoofer's maximum extension mode and maximum output mode - in other words possibly two room size ratings depending on mode. Without getting into product names I've seen at least one review where my reaction to the room size rating was incredulity and with people spending hard earned money based in all or part on a rating I think it's important to keep those ratings on the conservative side so yes I agree that the standard should be reference levels.

1) the use of the term "bassaholic" to describe room size might be confusing? if i was really a bassaholic, i'd like to setup an HT in the toilet to maximize room gain.

You don't already have one?

 

[GO-NAD!]

no comments on this thread. really??? Where are all the sub enthusiasts and critics when you need them ?!

Hey! Some of us have jobs that aren't with the AH website! My employer is paying me to type this right now and I don't want to abuse the priviledge...that he has unknowingly granted me...

 

[STRONGBADF1]

I think AH giving this type of recommendation is really going to open up some eyes. How many of us have overkill vs. not enough??? Should be interesting.

 

[westcott]

I think the lack of interest is due to the fact that most listeners have no clue what a properly positioned and properly setup AV room sounds like. And those who have heard a properly set up system prefer the overbassed systems they grew up with. It is the old story of more is better for most of your readers. I can not tell you how many systems I see with more than one subwoofer on this site and they are both placed up front below their main speakers.

I think it is a great idea to help people properly size a subwoofer for their space but more likely than not, they are going to buy some highly advertised hardware that stands 4 feet tall and gives bragging rights to their friends who also have no clue what good bass is all about.

It really is sad statement about the lack of effort of enthusiasts to understand how bass frequencies interact with the room and Audioholics is fighting an uphill battle but I find it admirable.

 

[nickboros]

I think that this sub rating metric sounds great. I'm in the camp that thinks that the most important speaker in the 5.1 setup is NOT the center channel speaker, but the subwoofer. Many home theater magazine reviews don't really even give much attention at all to the subwoofer. There may be a $60,000, 5.1 speaker system reviewed in which the "subwoofer" doesn't even extend flat past 30 or 40Hz and all the reviewer talks about is how airy, light, laid back, etc. the system sounds, with not even a mention of the subwoofer in the review. Oh and the subwoofer costs $5000. What??

The thing that really gets on my nerves is when a "subwoofer" doesn't extend flat down to anywhere near 20Hz, yet reviewers call it a subwoofer. What is next, calling bookshelf speakers full range speakers (or tower speakers), just because that is how the manufacturer refers to it. I think that Audioholics should be the pioneers in this area as well. Any "subwoofer" that doesn't extend flat down (within +/- 3 dB) to 25 Hz (maybe 20Hz would be better, but it may be a little too strict) should be called a bass module and not a subwoofer.

 

[gene]

Bassaholic Logo

Check out our Bassaholic Logo

 

[gene]

After debating with Josh about using Peak or RMS data for our Room Size ratings, I decided on a compromise with Josh (something I wish our political parties in washington would do). We will go forward using Peak as I originally stated but I bumped the Bassaholic requirement up +2dB to make it a bit harder to pass. I updated the article accordingly.

 

[chilipalm]

Who the hell has a room bigger than 1500 ft let alone 5000 ft??!

 

[templemaners]

Who the hell has a room bigger than 1500 ft let alone 5000 ft??!

It's CUBIC feet. So, you only need a 10 x 15 ft room with 10 ft high celings for 1500 cuft and people with valuted celings or great rooms regularly exceed 5000 cuft.

 

[mike c]

Who the hell has a room bigger than 1500 ft let alone 5000 ft??!

im guessing that's 1500 CUBIC feet and 5000 CUBIC feet, and not SQUARE feet

 

[its phillip]

I wouldn't mind having rooms that big though

 

[templemaners]

I wouldn't mind having rooms that big though

Really? Give me the small rooms & useable room gain please.