How many here have measured their frequency response?

JLM · « **on:** 11 Sep 2012, 10:24 am »

Is this the elephant in the room (circle)?

How did you measure (equipment/software, locations, etc.)?

If you haven't measured, why not?

I ask because many/most audiophiles I've met don't have a good handle on spls or bass response (they under estimate both rather severely).

JohnR · « **Reply #1 on:** 11 Sep 2012, 10:28 am »

Not only is it the elephant, but it's pink, got spangly things on it, and it's dancing.

jtwrace · « **Reply #2 on:** 11 Sep 2012, 11:02 am »

TJHUB · « **Reply #3 on:** 11 Sep 2012, 11:09 am »

I've been using Room EQ Wizard (REW) for years. I really only measure at the listening position for 2-channel. I'm lucky in that I have a great sounding room and it measures great from about 50hz and up. As such I mainly use the measurements to EQ my subs.

I would like to understand waterfall graphs better, but my latest changes to my room treatments was a huge improvement to the sound. Maybe I don't need to worry about for a while...

*Scotty* · « **Reply #4 on:** 11 Sep 2012, 06:56 pm »

I have measured mine using the RTA Lite app on my iPhone4, but not with any great accuracy. In as much as I am using multiple subs without any other form of equalization or passive bass resonance control I am stuck with what I've achieved unless I resort to another sub or get delay to the existing subs implemented. It doesn't measure too bad and as others who have heard the system will attest, it doesn't sound to bad either. I think I have some minor amplitude, shallow nulls that could be filled in with some relocation of the subs.
Snapshots of RTA Lite measurement below. The same position was used for all measurements.

RTA Lite measurements are subject to the iPhones software control of the internal mics response curve which was not chosen for accurate acoustical measurements, but resistance to interference from wind blowing across the mic. The display also bounces around a lot and is unstable below the point where the RTA lite program tries to compensate for the iPhones microphone curve.
Scotty

*Scotty* · « **Reply #5 on:** 11 Sep 2012, 10:56 pm »

I think for many people, the hobby is more about Beauty than Truth. Once you measure the decay times in your room and the frequency response curve, any illusions you might have had about just how good your judgment is and how well you hear are rather thoroughly dispelled. It is harder to live a lie with the truth staring you in the face.
I think many people are perfectly happy listening to their system as is. They think it sounds fine and it is what they are used to warts and all. Perhaps ignorance really is bliss. Speaking for myself, I like to know why things work the way they do.
Only those who are interested in an accurate presentation in the bass, and the rest of the frequency range for that matter, are going to go to the trouble to measure what is happening and doing something about the short-comings that are uncovered.
This is going to be a tiny segment of those people in the hobby, many people towards the mainstream of the hobby think we are crazy or Bass Freaks for using more than one sub-woofer. Those are the very people who you would think would be curious enough to wonder what advantages there are to using more than one sub in a system.
Scotty

JLM · « **Reply #6 on:** 11 Sep 2012, 11:28 pm »

Thanks gentlemen. Confirmation is a wonderful thing, but the opposite - like you stated - not so much. As Floyd Toole states: acclaimation to our system/room comes very quickly and easily.

Scotty, I agree - igorance is blissful. Yet it amazes me on the money wasted on equipment in the horrible rooms I've heard.

I've only used a RS spl with stereophile test CD2. Feel free to slap me because I have a Behringer DEQ2496 in the system with the matching mike and have never tested the room (finally found a link that might explain how in language I can understand).

nickd · « **Reply #7 on:** 11 Sep 2012, 11:34 pm »

I second the "Ignorance is bliss" thought. I love my rig and I love the bass

. Finding out it measures like crap

would just bum me out and make me want to go broke trying to fix it.

Rclark · « **Reply #8 on:** 11 Sep 2012, 11:47 pm »

It's awesome that there are several here who are very qualified to truly help people achieve highest possible performance. There aren't many forums that do. Looking forward to non-ignorant bliss with a properly set up multiple sub system. 3-4 subs, properly measured and treated room, proper control.

*Scotty* · « **Reply #9 on:** 11 Sep 2012, 11:56 pm »

nickd, not necessarily, depending on your room and system, neither of which is posted. You might only have to add a second sub-woofer operating out-phase with the front speakers or sub in order to solve most of your problems.
You don't have to measure first before taking this step. You can safely assume you have problems in the bass, every single loudspeaker system with bass extension below 100hz will create a pattern of standing waves in the listening room. The magnitude of the problem will depend on the loudspeaker design and the size and shape of the room. In this matter the laws of physics dictate what happens without exception.
Scotty

medium jim · « **Reply #10 on:** 12 Sep 2012, 01:47 am »

Scotty:

I don't have too much faith in iPhone based RTA's as they seem to exaggerate the sub bass. I have both RTA Lite and JLAudio...Jl Audio seems to be the more accurate of the two.

According to one here, I used Hillbilly Old School techniques to test my room. That is to run a Test Frequency CD that has 30 tones, ranging from 20hz to 15Khz that sweeps from left to right in a 15 second sweep. The test setting is 85db in the listening position...I used a Modern Radio Shack Digital SPL Meter to take the readings and wrote them down on graph paper...

My subs are 8ohm which conflicts with my Magnepan's which are 4ohm. That said, I employ a pair of Maggie Mates High-Pass Filters that are first order x/o's with a 12db slope (for my particular maggies) and are set at 60hz. This is the only EQ I have. My system is reasonably flat to 32hz with a drop off of 6db @20hz...there is no real dips or peaks (anything over 3db). My subs are x/o'd at 80hz low-pass and 60hz high-pass....the blending of the the 60 to 80hz between the mains and subs seems to make the subs disappear and eliminated any hint of smear there might have been.

I tried to find the graph, but I cannot as I did it over a year ago. Prior to the Maggie Mate's. there was a valley between 60 hz to 150hz as the fixed high-pass in the subs was set for an 8ohm feed...in effect, a suck out of the mid bass. I will note that it took about 10 readings to get the bass right as I had it about 7db pushed to compensate for the lack of mid bass (initially) and now have it very flat. Funny thing, there still is ample slam, but is much faster and musical. I trust my ears for things like note attack/rise and then decay. This is the area where room acoustics and treatments play into the mix.

I run my subs stereo, or for better terms, left feed to the left sub and right feed to the right sub. I sort of like them phased at 90 degree, but 0 degree is more natural.

I'm rather pleased with 2 subs, but again that is room dependent and a larger or my lively room may dictate a rear sub or two to smooth out any room funkiness.

I will some day get a computer based RTA that will allow me more ways to look at the same thing, but the best tool in the end is your own ears, ymmv.

Jim

mgalusha · « **Reply #11 on:** 12 Sep 2012, 03:27 am »

yep. Dayton mic that I have accurate correction curves for, mic preamp, creative usb card, Acoustisoft R+D, TrueRTA, HolmImpulse.

*Scotty* · « **Reply #12 on:** 12 Sep 2012, 03:35 am »

I just haven't worried about exactly how the system measures, because beyond a very crude graphic equalizer program that resides on my Linux computer, computer based equalization is not a viable option. The good thing about putting an extra sub-woofer at the rear of the room is that by itself it is an effective tool for controlling the bass resonant behavior in the listening room which is the primary cause of the response irregularities in the first place. I broke out my "vintage" analogue Rat Shack meter tonight and I am better than + or - 5 dB from 125Hz to 20Hz. Allowing for the -6dB down at 20Hz of the C weighted curve, I am flat at 20Hz and 2db up 30Hz. The response is up about 5 dB between 50 Hz and 100Hz relative to the levels at 125Hz which is my reference frequency. The RTA Lite on the iPhone 4 abruptly goes deaf to the warble tones at 40hz. When RTA Lite on the iPhone 4 is used with pink noise with SPL levels above 60dB RTA Lite responds down to the frequency limit of of 16 Hz. I think it may be 2dB to 3dB optimistic about the flatness of response below 80Hz with the instability in the graph it is hard to tell. Frankly the system flatter than I thought it was but it is not completely free of standing wave zones by any means. The plus 5 and 6 dB between 50Hz and 80Hz aggravate me I should be able to do better.
Scotty

medium jim · « **Reply #13 on:** 12 Sep 2012, 03:42 am »

Quote from: JLM on 11 Sep 2012, 10:24 am

Is this the elephant in the room (circle)?...

Actually, this is "The Manatee Bar" Circle, so pull up a chair!

Jim

*Scotty* · « **Reply #14 on:** 12 Sep 2012, 03:53 am »

I just downloaded the JL Audio RTA and it can't hear warble tones as a discrete tone it shows a 70 dB 200 Hz warble tone as a broadband noise with an increasing slope towards the RTA's low frequency cutoff point which it reads as an SPL of 90dB. This thing is also wildly inaccurate on music as well showing music to also have a sloping frequency response that peaks out at 90 dB at the low frequency cutoff point when the RS meter and the RTA Lite app show the SPL on the music at 70dB. Maybe it does better with pink noise as test signal. I am glad I didn't pay anything for the app.
Scotty

medium jim · « **Reply #15 on:** 12 Sep 2012, 04:06 am »

Quote from: *Scotty* on 12 Sep 2012, 03:53 am

I just downloaded the JL Audio RTA and it can't hear warble tones as a discrete tone it shows a 70 dB 200 Hz warble tone as a broadband noise with an increasing slope towards the RTA's low frequency cutoff point which it reads as an SPL of 90dB. This thing is also wildly inaccurate on music as well showing music to also have a sloping frequency response that peaks out at 90 dB at the low frequency cutoff point when the RS meter and the RTA Lite app show the SPL on the music at 70dB. Maybe it does better with pink noise as test signal. I am glad I didn't pay anything for the app.
Scotty

That surprises me, but then again, I have the iPhone 3G and not the newer version.

Glad it was free...

Jim

*Scotty* · « **Reply #16 on:** 12 Sep 2012, 04:15 am »

tabrink, I am waiting for the battery in my iPhone 4 to get tired sometime after the first of next year, then I will justify the new phone by saying it only costs $115 more than the cost of a new battery for the iPhone 4. Assuming that the price is 'only" $200 and two more years in cellphone prison.
Scotty

targa02 · « **Reply #17 on:** 12 Sep 2012, 04:34 am »

I had mine measured by Clayton Shaw as I am a Spatial customer. I apologize upfront for any lack of knowledge on my part regarding this topic. I am no where near as informed as many on AC.

When Clayton measured my system he stated that the frequency response was quite good, but the time decay in the lower frequencies was a problem. Basically the lower frequencies were taking way too long to "die". Clayton was able to "smooth out" the mid and upper frequencies, which makes a HUGE difference in the sound. Music sounds much more relaxed without losing any detail. Much like moving from from a mediocre DAC to a really great DAC.

Any room correction software can only do so much for low frequency problems - enter the Spatial Black Hole. The truth is, I do not notice that the thing is even in the room most of the time. However, if I play music that has a lot of low frequency information and I turn off/on the Black Hole I notice a big difference.

I know I sound like a Spatial fan boy, and maybe I am. I have had nothing but great experiences with Clayton and team. I have no association, other than being a satisfied customer.

Rclark · « **Reply #18 on:** 12 Sep 2012, 04:36 am »

Oh you have one, please do tell more. Can you describe your room and setup, and the total effect of the Black Hole?

*Scotty* · « **Reply #19 on:** 12 Sep 2012, 04:46 am »

targa02, have you tried moving your main speakers closer to the wall behind them? Assuming you have one Spatial Black Hole located behind you against rear wall of the listening room you might get flatter bass response if the speakers in the front were able to load to the front wall better. This would help them create a closer approximation to a planer wavefront which the SBH could more effectively cancel out.
Did you notice any improvement in the systems imaging after you installed the SBH sub-woofer?
Scotty