Rythmik or SVS?

[Steve81]

Steve, please correct me if I am mistaken on any of this!

I don't have much to add, though as Warrior states, different rooms will invariably deliver different results, so it makes sense to take measurements to see exactly what's going on. There's no single curve that will fit every room, which can range in size from a small 10x12 room to a 10,000+ cubic foot great room. Still, for most smaller spaces, I believe the curve I posted would be a better starting point than a flat to 20Hz anechoic response.

 

[KEW]

I don't have much to add, though as Warrior states, different rooms will invariably deliver different results, so it makes sense to take measurements to see exactly what's going on. There's no single curve that will fit every room, which can range from small bedrooms to 10,000+ cubic foot great rooms. Still, for most smaller spaces, I believe the curve I posted would be a better starting point than a flat to 20Hz anechoic response.

Certainly.

My main point is we are so used to coveting a flat frequency response that that has become the norm for subwoofers even though it is clearly not what you want for realistic accuracy.

That may be why PSA subs have done so well. They start a gradual roll-off at around 90-100Hz.:
XS15se:

I am impressed with how smooth your curve is. I would have expected nulls and nodes that would be dramatic. Would they show on this chart? Would smoothing obscure them? Do you have room treatments/bass traps that are helping?
Comments/thoughts?

If you have a thread already discussing this, just give me a link!

 

[herbu]

Dr. Bob,
All this fine technical discussion notwithstanding, to your original question of, "Rythmik or SVS?", the answer is "Yes".

 

[Steve81]

My main point is we are so used to coveting a flat frequency response that that has become the norm for subwoofers even though it is clearly not what you want for realistic accuracy.

Agreed.

I am impressed with how smooth your curve is. I would have expected nulls and nodes that would be dramatic. Would they show on this chart? Would smoothing obscure them? Do you have room treatments/bass traps that are helping?
Comments/thoughts?

If you have a thread already discussing this, just give me a link!

The chart above is just the anechoic response of the Funk 18 in its "Rock" setting; this is the in room response (don't recall if it's unsmoothed or 1/24 smoothing, but it'd show any big issues either way), which is representative of the two money seats:

As mentioned, the curve from DB was the starting point. The FW18 has 10 available bands of EQ to work with, so I used a handful of narrow band filters to help deal with room effects, and I disabled the 6dB/octave high pass at 20Hz. The net result of all the EQ is the white curve here:



Relative to the native system response, you can see it's really just a bit of cutting here and there (the biggest cut is 6-7dB at ~45Hz) and a very mild bump centered at 20Hz.

 

[3db]

Certainly.

My main point is we are so used to coveting a flat frequency response that that has become the norm for subwoofers even though it is clearly not what you want for realistic accuracy.

I think I would prefer the flat response and eq it down rather than having the rolled off curve and attempted to correct it with room gain. That could get tricky.

 

[Dr. Bob]

Dr. Bob,
All this fine technical discussion notwithstanding, to your original question of, "Rythmik or SVS?", the answer is "Yes".

Yeah, or Hsu or PSA .... Thanks a lot....

 

[Steve81]

I think I would prefer the flat response and eq it down rather than having the rolled off curve and attempted to correct it with room gain. That could get tricky.

It definitely requires a bit of insight as to how your subwoofer interacts with your room. Ultimately it doesn't really matter of you start with a flat anechoic response, so long as you EQ it appropriately to adjust for the room, and you have adequate output over the passband to maintain your desired response. Note, that wasn't the case with the PB13 in my room; even when EQed flat, its top end would noticeably sag on a 105dB sweep at the MLP.

 

[3db]

It definitely requires a bit of insight as to how your subwoofer interacts with your room. Ultimately it doesn't really matter of you start with a flat anechoic response, so long as you EQ it appropriately to adjust for the room, and you have adequate output over the passband to maintain your desired response. Note, that wasn't the case with the PB13 in my room; even when EQed flat, its top end would noticeably sag on a 105dB sweep at the MLP.

So it boils down to personal preference whether or not a roll off on a sub is good thing or not and not that the roll off is the desired way to go.

 

[Steve81]

So it boils down to personal preference whether or not a roll off on a sub is good thing or not and not that the roll off is the desired way to go.

The short answer is that it depends. Consider something like the old SB12-NSD; SVS used their DSP magic to shape the response such that it was flat into the 20Hz range in outdoor testing. Personally I don't see the point, given that:
a. the system couldn't maintain that response even at a modest 100dB drive level in Josh's testing.
b. in a smaller room where such a sub is likely to be used, the end user will probably need to scrub off that low end boost to achieve a relatively flat in room response.
The only "advantage" I can see is that SVS could market a 14" cube as being flat down to 22Hz.

Something like your Rythmik LV12R would be a different scenario, since the system is presumably flat into the 20Hz range natively. Even then, Rythmik provides you with the tools to shape the response accordingly, whereas the SB12-NSD and the JL E112 would require outboard assistance to get the job done.

 

[KEW]

I think I would prefer the flat response and eq it down rather than having the rolled off curve and attempted to correct it with room gain. That could get tricky.

I'm inclined to disagree with this since Audyssey could not sufficiently correct for the anechoically "flat response" of my E112's to accomplish a true flat response in my largish living room.
Even if the target manufacturers response was designed with an approximation of the room gain of Steve's hypothetical 10, 000 cu ft great room in mind, it would be a more reasonable starting point to tune to our room.

 

[PENG]

I have seen a few plots by Gene and others that showed Audyssey XT32 could not do much for their room and I have no idea why. I am sure my room is not perfect yet XT32/Sub EQ HT has done a very good job on my PB13U and PC12U. According to Audyssey, we should not use the sub's EQ feature if we use Audyssey, i.e. one or the other but not both. After spending many hours trying to get the best curve I could get, I tried going against their recommendations and after several attempts I was able to make one PEQ adjustment that managed to flatten the curve a little more but even without doing that the curve I obtained was excellent. The only hiccup is that if I re-run Audyssey, the improvements gained by that single PEQ adjustment on the PB13U will be gone. That's really not a problem because now that I know, I will always run Audyssey first, and then make the adjustment on the sub.

My Rythmik E15HP is in a different room but my initial subjective impression is that it won't sound much different/better than the PB13U. I don't have a SB13U but my gut feeling is that the choice between it and the Rythmik E15HP is not going to be based on sound quality.

 

[KEW]

Steve,
How big is your room and where is sub located relative to walls for the curve you posted? I know there are other factors that complicate room gain, but I am curious after seeing your graph that is 5dB down at 40Hz and 12dB down at 20Hz!

 

[Steve81]

Steve,
How big is your room and where is sub located relative to walls for the curve you posted? I know there are other factors that complicate room gain, but I am curious after seeing your graph that is 5dB down at 40Hz and 12dB down at 20Hz!

The room is in my basement and the rectangular portion is roughly 24x13x7, with another ~3x12 chunk for the stairs and landing. Sub is located in the front left corner, but pulled out a tad towards the front left speaker, about 9 feet from the MLP.

The interesting part is that room represents about 50% of the total basement, with the two halves only separated by a fairly thin wall (the other half is unfinished). I would doubt such a wall represents any significant impediment towards a 20Hz sound wave, so the effective area may well be double.

 

[PENG]

shadyJ, I don't think you're right to equate group delay with stored energy. According to here:
"In simple terms, group delay is the time it takes for an electrical input signal to become an acoustical output. It is frequency dependant and should ideally be zero seconds at all frequencies, but this is practically impossible."
So group delay would show up in the graphs as a shift to the right - indicating that the signal doesn't start at t=0 but at some later time.

Since the Fourier transform of an impulse is a flat spectrum, the graph should ideally show a thin red line on the left of the graph, and nothing else. This is very nearly what the Rythmik graph shows. The red/orange bulge protruding to the right in the E112's graph shows that there is significant energy at about 20 Hz that is hanging around longer, while the other frequencies have died out: stored energy. Orange is about 85 dB, so this would certainly be audible.

I'm not claiming to have any experience in these things: I've only owned one subwoofer in my life. But theoretically I'd expect any rightward protrusions in the graph to be heard as boominess - and that's what KEW is claiming to hear.

From what I have read so far, I also have to disagree. They may be related, but they are different topics.

 

[PENG]

Thanks for the info.
You specify manually taking measurements, I wonder why Audyssey (XT 32) did not tame the E112's? (I'm sure it did, some, but the Rythmiks are so much easier to listen to!)

When I have time I will use REW to take more measurements of the E15HP. EQ'ing sub is more than just taking frequency response measurements. I would definitely leave it to Audyssey, Anthem ARC, or whatever that works..

 

[KEW]

The Schroeder Frequency helps define why Subwoofer measurements cannot be in-room: Below 250 hz, the room controls everything! Specific room dimensions that match quarter or full wave diameters, will resonate. So a given subwoofer will measure differently, in different rooms.

Agreed. I said earlier that anechoic measurements are used to allow a repeatable measurement.
My point is that a flat anechoic response is a lousy target for any typical listening room if you are looking for a realistic balance of bass with the rest of the frequency spectrum.
If you have a flat anechoic response, you need to be sure your system has the ability to decrease bass to compensate for the increase from your room gain.
I think Steve's example of the anechoic response which worked well in his room demonstrates this well:

 

[herbu]

My point is that a flat anechoic response is a lousy target for any typical listening room if you are looking for a realistic balance of bass with the rest of the frequency spectrum.

Seems like that would be a tough nut to crack for most of us. Would need to measure a flat source in your room, then find a sub/speaker whose anechoic response is the inverse?

The gain on both your AVR and sub are likely for the whole freq range of the sub. So if you crossover at 80Hz, you can turn up/down the volume from bottom to 80Hz, but turning up/down 20-40Hz only would be tough. Right?

I can see how finding a sub whose response is the inverse of your selected room and position would be best... but could you realistically do that?

 

[KEW]

Herbu,

I am not proposing attempting to find a sub that counters one's room-gain in any precise manner, I am proposing finding a sub based on anechoic measurement that makes it easier for the tools we have available (Audyssey) to make them sound better in room. That sub would not havean anechoically flat FR!

Can I quote Steve81 as an authority on this? He is getting pretty good with bassoholism!

In my room, this was the (anechoic) starting point I chose to achieve a (in-room) relatively flat response:
(KEW added colored text to help with context)

You can see how that differs from the E112, both in terms of how JL boosts the low end, as well as the behavior on the top end. If KEW's room is anything like mine, it wouldn't be hard to imagine the E112 sounding less than stellar without manually taking measurements & applying EQ.

That last sentence is worded in a convoluted way with the double-negative, so let me clean it up:
"If KEW's room is anything like mine, it would be hard to imagine the E112 sounding good without manually taking measurements & applying EQ."

There's no single curve that will fit every room, which can range in size from a small 10x12 room to a 10,000+ cubic foot great room. Still, for most smaller spaces, I believe the curve I posted would be a better starting point than a flat to 20Hz anechoic response.

First off, the nulls and nodes will vary greatly between rooms. There is no way to address that using a "target curve"! I use location, dual subs, and Audyssey as the best tools I have for nulls and nodes.

My focus in the thread is room gain. Going from 100Hz to 20Hz gives a ~12dB total roll off. Unless your room is extreme with treatments and bass traps, his room has much more in common with yours and mine than an anechoic chamber does. I firmly believe that if there was a study of gain in "normal" residential listening rooms they would all show at least 8dB of room gain at 20Hz. (We don't want to undershoot it because EQ should not be adding significant output. That is why I am looking for at least rather than average).
So I would say a curve like the SVS SB13Ultra offers enough bass at 20Hz to ensure you will have ample bass in your room, but not so much as to overwhelm the ability of Audyssey (as was the case when I attempted to tune E112's).

I also find it quite interesting that while their flagship sealed sub has the above FR, SVS invested extra cost in the lower-level SB12-NSD to more aggressively overcome the natural roll-off of a sealed sub (unfortunately the horizontal scales are different):

My belief is that SVS did this because people buying at a lower price-point (maybe their first system) are all about getting bass that calls attention to itself and impresses; however, by the time they are willing to invest in a SB13-Ultra they realize that for optimum SQ, a sub should never draw attention to itself, it should only make the mains sound better.

That said, I am all about boosting the level of the subs and letting them have there moments of glory for HT!!!

 

[3db]

I would still take a flat response and use room position to get me close to a flat response than deal with a sub that has a non linear response curve in the pass band.

 

[KEW]

I would still take a flat response and use room position to get me close to a flat response than deal with a sub that has a non linear response curve in the pass band.

Which "Bass Extension" setting (on the amp panel of your Rythmik) do you use?

Bass extension settings Low (19hz,Q=1.1), med (22hz,Q=0.9), and high(24hz, Q=0.8)

From Rythmik's quick guide:

Bass extension switch This switch determines the bass extension as well as the damping. Low extension setting is also low damping setting. This is recommended for HT application. High extension also uses high damping which gives cleanest sound. Mid and high extension settings are recommended for music playback.