How far can room treatments solve boomy bass?

In the 3 listening room that I've measured, Hemholtz devices like the tube trap/bass trap can be reasonably effective down to a little below 100hz. In an untreated room, you'll often see a hump in the half octave above that point. I've been pretty successful in taming that with bass traps.

Below that point, I've always had to deal with +/- 10db lumpiness that seems to resist "passive" treatment. I ended up using DRC (Audyssey, et al) to clean this up. I don't know if every room works this way, but it's been pretty consistent in my homes.

Good Luck.

Marty

Ja2,

Quarter wave effects exist for all of those surfaces. The closer the surface, the stronger the cancellation (deeper null) and the higher in pitch that the first null will occur. In most cases, I suspect that the wall behind the speaker is the biggest culprit, but it will be room dependent. In a small room, like the OP's, you have less flexibility in addressing this via placement. Even in large rooms, you're still going to get audible cancellation until you can get more than 10' from the nearest wall. That's usually impracticle.

If you use in-wall, flush to the wall, or on wall speakers, the analysis changes, but that's not the case for the OP.

It is true that placement, treatments, etc can somtimes reduce the impact, and reduce the amount of parametric EQ required. However, I've never seen a case where EQ did not produce clearly audible improvement after those steps were taken. I'm not suggesting that anyone abandon treatments, careful positioning, etc. I'm simply stating that, below app. 100hz, EQ is the only tool that I've found effective.

My conclusion is based on listening, but it is very clearly supported by measurements.

Kijanki,

Good luck finding absorptive material that's effective below 100hz. I looked for years, tried many, and never found any that worked. If you find any panels that work, please let me know.

As to "boomy bass" and the room's reverberant signature....that can be a problem in some rooms. The 1/4 wave and related modal issues will almost certainly be a problem in every room. In every case I've addressed, the latter has been far more severe, but this is certainly room dependent and case by case.

Simple passive treatments can usually get the worst of the reverberance problems under control. Proper placement can reduce cancellation effects, particularly if you employ multiple subwoofer (ala Duke L's "swarm " system) or soffit your speakers. Neither is usually an acceptable solution for obvious practical reasons.

Unless you're willing to that route, only Parametric EQ will address the 1/4 wave and related modal issues in the bottom 2 1/2 octaves. In all 3 dedicated listening rooms that I've had and in both dedicated HT rooms that I've had, parametric EQ has made a VAST improvement in the quality of bass response after extensive room treatment. It was instantly audible and clearly measurable.

Reverberant issues are usually easier to deal with passively, and that's what I do. However, that still usually leaves crappy FR below 100ish hz. At least it does in every room that I've measured. In all cases in which I've employed EQ, the room were decent to begin with. In all cases, the sound was better after room treatment and far, far better after EQ.

I'm not sure where/if I ever implied that room treatment was bad, but I never intended to. I use Hemholtz devices and a variety of absorptive panels in my current room. Still, bass quality is IMO night and day better when Audyssey is in the loop. That doesn't mean "perfect", it means "night and day better"?

IMO

Marty

My understanding is that the PARC is an analog variation of room EQ. Audysey, ARC et al work in the digital domain. I'm not sure whether PARC includes an RTA function (room analyzer), but if it doesn't you'll probably use a stand-alone RTA for set-up.

As to Ja2's contention that you can't fix acoustic problems with EQ, I'd respectfully disagree. Respectfully, but emphatically. Modern parametric EQ is an amazing thing and - to my ear - makes a bigger improvement in overall sound than just about any other change you'd make in a system. To test this claim, find any AVR with Audyssey and do a "before/after".

As always, however, YMMV.

Marty

To be clear:

1) Per Kijanki, EQ is not a "magic bullet" that fixes all problems. It is - IMO - a magic bullet that fixes one BIG problem.

Per Ja2) FR issues below 150hz or so have been IME virtually impossible to correct with traditional room treatments - including tuned Hemholtz devices.. Even if you fir out the walls to achieve ideal (or near ideal) relationships, you still have serious FR issues in most rooms with most speakers.

For instance, you will end up with destructive interference - unless your speakers are mounted on the wall or soffited into the walls. Quarter wave effects generally result in gross FR deformation (>10db at some point in every room that I've measured) below 150hz. Parametric EQ can bring that to virtually dead flat (depending on the system you're using). I find the delta instantly and dramatically audible. A simple visit to any HT retailer will allow you to A/B Audyssey. Form your own judgement, but I would be shocked if anyone missed the impact of the parametric EQ.

This certainly doesn't mean that everyone will like the sound of such a system. But, for the OP's question regarding a room too small for his loudspeakers, I don't know of any alternative to EQ. Even in a good sounding, fully treated room, I've yet to find a passive room treatment that is effective much below 100hz where these effects are so clearly audible.

I'd agree that traditional passive treatments are useful for many problems (particularly as Kijanki noted, issues related to the reverberant field - slap echo, etc.). That is why my listening room is heavily treated. However, I still use Audyssey. If you wanna fix the bass, there ain't nothin' like parametric EQ.

IMO.
YMMV (but I kinda doubt it.)

Marty

Jim,

I've never used a PARC.

My DRC set-up has evolved from using an NHT X-2 active x-over between my ARC LS-25 and VT130SE. The NHT fed a Velodyne SMS-1 subwoofer management system, which fed a pair of powered subs (originally Velos, then Rythmiks). This arrangement EQ'd only the signal headed for the subs and put only the NHT in the main path. It worked very well, but was kind of kludgy - 4 boxes to power up, etc.

I also maintained a parallel system in the same room with Joule and Cary or Prima Luna electronics that allowed for a non-EQ alternative, that I used mainly for vinyl.

Separately, I had also been using Audyssey in my HT room for years. When Stereophile did a very enthusiastic review of Audyssey XT32, I picked up an Onkyo pre-pro that contained this system. I figured that I'd try it out in my main 2 channel room and - if I didn't like it - I'd just use the Onkyo to replace my older pre-pro in the HT room.

Bottom Line: The ARC and Joule came out, the Onkyo went in and has never left. All sources - including vinyl - get the full XT32 treatment. I understand that this requires me to turn in my audiophile merit badge, but I simply prefer the sound this way.

Marty