Rear Port and dual opposed driver subwoofers aren't getting a fair shake (1 Viewer)

[Mike Up]

I always thought that rear firing subwoofers weren't getting a fair shake when the CEA 2010 reviews came out. Looks like subwoofers producing sound at opposing directions need compensation compared to subs that have all of the sound coming out at one position.

See article here.

I got interested in this because the sealed SVS Micro 3000 came up almost 10 db lower in output than the cheaper SB-1000 Pro considering the two 8" subwoofers should have a total surface area similar to a 11.25" subwoofer. This output should be very similar if not more than the SVS SB-1000 pro due to greater amplifier power in the Micro 3000.

I would think if you really wanted to be fair, an in room test should be done in a 4000 CF to 5000 CF so that cabin gain wouldn't affect the subs.

I'm betting that SVS Micro 3000 isn't as bad as tests make it out to be when you actually get it into a room and compare against others.

 

[theJman]

You are correct, if the mic is not pointing at all the sound sources - drivers and ports - then the SPL measurements are not a true representation.

One of the premier testing sites was databass.com, considered by most to be the best place to get objective ground plane measurements. A subwoofer company by the name of Epik had sent one of their dual opposed subs for evaluation and the SPL numbers came back on the low side. The owner of the company provided databass with engineering data that showed measuring the way they did wouldn't account for the contribution of both drivers. databass agreed and changed their rating system to add a factor for dual opposed, basically the "compensation" you referred to.

A room will always change the output and response of a subwoofer, I'm not even sure 5k^3 would be large enough to eliminate that problem. Unless you're talking about something the size of Madison Square Garden, longer than any bass wave, an indoor measurement won't provide as accurate a reading as ground plane will.

 

[JohnRice]

Sometimes I can't help but wonder about some of these online experts. Room interaction is a factor with any speaker, but especially subwoofers. A 20Hz sound wave is over 50 ft. long, so room interactions are a significant aspect of how a subwoofer performs. If I'm understanding that article correctly, they were testing subs outdoors, which honestly, it seems to me will be mostly useless. First, most subs have more than one source. The main driver and either ports, passive radiators, or multiple drivers.

There's a lot more to it than just the driver area. Cabinet volume is a major factor, along with power and several others.

Maybe this is part of the reason I tend to get so much push-back regarding my advocating sealed subs, at least with higher end models. Equivalent ported models test better, but a capable sealed model will produce better overall performance and fewer negatives, in my opinion, in a lot of cases. I'm not absolutely certain, but a reduction in room interaction problems might be one of the reasons.

 

[JohnRice]

Just to add. traditional 1 meter testing doesn't work with line array speakers either. Honestly, the reason should be obvious. The range of distance that sounds are produced from is far too large to measure from 1 meter.