Bass trapping below 80hz, practical or not?

[yepimonfire]

Okay, finally set everything up with audyssey. Using a single sub in the back left corner, this is what I get.

First off, getting audyssey to not roll the highs off required placing the tweeters at ear level. As you can see, there is a small dip at the xover without audyssey because the speakers were designed to be flat at the midpoint between the tweeter and driver or above ear level. I have no idea why it causes a roll off if I don't point the tweeters directly at it.

Wondering where the 60hz dip is coming from when measuring the combined response. My guess is the sub distance is wrong. Going to try and setting it to the actual distance and remeasuring, since it wasn't there before audyssey changed the distances.

Still don't understand why I'm unable to get below 30hz in this room, even though the sub is tuned to 23hz and measures that low in every other room. My guess is that the 50hz peak boosts frequencies from 30hz on up and therefore lower frequencies that aren't affected by the room get shoved down. Using the parametric eq on my pc, I was able to get a flat 23 hz f3 without distortion, so I may just have to get a minidsp to correct it.

I tried placing the sub, 1200 in the front right corner and it reintroduced the big peak. I'll have to play around with other positions.

At this point, I'm pretty much done trying to get audyssey to work properly. It does an excellent job of flattening the bass, but it screws everything above 300hz up. It's apparent from the measurements of the l/r on direct without audyssey that I don't need any correction at all above 200hz.

The main goal is getting a decent bass response at the front of the room, hopefully I can find a good spot at the front of the room for the 1200.

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[Johnny2Bad]

Try to concentrate on correcting dips (or correcting them first) versus correcting peaks; that should result in a better overall sound.

 

[yepimonfire]

Try to concentrate on correcting dips (or correcting them first) versus correcting peaks; that should result in a better overall sound.

Well, the only major dip is at 60hz when the speakers are measured with the sub, that can be corrected by adjusting the distance.

With the sub located where it is, using an 80hz xover solves the peaks.

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[everettT]

What are your waterfall plots telling you? You have started to figure out the 80hz crossover is sounding better to you but why? My mains can play clean into the low 30s, but I cross my subs above 100hz (Subs will play well out to over 200hz) . Keep working on your measurements with a calibrated mic and sound card.

I get you are really into you Klipsch, but nothing says running anything other than their TOL and the RFs full range is a good idea (even then other than music I wouldnt).

The ultimax drivers are nice, but require lots of power and eq to play low. Maybe consider the RS series instead. 2 15s in your room would play loud and handle a high crossover better. The ultimax has the edge below 25hz, again with high power and eq.

I have a dbx mic that needs phantom power that I'd ship to you free. It's limited below 20hz but has a calibration file. If you have a mic preamp and are interested PM me.

Your obviously devoted to improvements, so keep listening to those who have been doing this a while.
Diy subs are an inexpensive why to improve the sub 120hz range and the Dayton RS require no EQ except room issues and less power to drive them to reference levels.

 

[yepimonfire]

That there's ringing in the time domain at those modes, and that it is a minimum phase problem that can be corrected via eq. If I have 2-4 subs around the room with global eq would eliminate the variable response and virtually nullify the ringing in the time domain.

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[TheWarrior]

I’m in Hong Kong and there’s too much going on for me to reply from on an iPhone.

You have to measure ALL speakers when tuning bass. A lack of just one pressure source is going to give you incomplete data in your measurement - you are not level matching surround speakers, you are distributing sound pressure so that you hear every frequency when, and where you are supposed to. (Where, resulting from the enormous wavelengths, and when resulting from half wavelengths lining up at the Listening position that measure as a cancellation)

 

[yepimonfire]

I’m in Hong Kong and there’s too much going on for me to reply from on an iPhone.

You have to measure ALL speakers when tuning bass. A lack of just one pressure source is going to give you incomplete data in your measurement - you are not level matching surround speakers, you are distributing sound pressure so that you hear every frequency when, and where you are supposed to. (Where, resulting from the enormous wavelengths, and when resulting from half wavelengths lining up at the Listening position that measure as a cancellation)

As in 7.1ch stereo?

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[everettT]

As in 7.1ch stereo?

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I had asked about LR and sub to get a baseline to what your hearing. What @TheWarrior is asking is the same but all channels. It should take time to make sure that all data is correct. I didn't notice if the mics Cal file was entered. Are you still using the Dayton mic?

I'll ask again, what is the waterfall plot showing you? Dealing with your room in the time domain is very revealing

 

[TheWarrior]

As in 7.1ch stereo?

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Are you connecting computer via HDMI? Just leave your receiver in a surround sound setting and measure well above your LFE crossover.

That said, loudspeakers are minimum phase devices. Which means that in a high resolution measurement (no smoothing in latest REW) if there is a peak, it will ring. That is a near direct quote from Toole (CIRMMT video, and in his books)That inferential knowledge allows us to confidently use frequency response as your primary tool. Waterfalls are pretty, but because you have to choose between frequency or time resolution, it can mask a problem.

 

[yepimonfire]

Latest measurements. Getting good bad in the front and back seems to require either an extra sub up front or the main+lfe setting. Going to mess around with the 1200 up front and see what I can't get.

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[yepimonfire]

I had asked about LR and sub to get a baseline to what your hearing. What @TheWarrior is asking is the same but all channels. It should take time to make sure that all data is correct. I didn't notice if the mics Cal file was entered. Are you still using the Dayton mic?

I'll ask again, what is the waterfall plot showing you? Dealing with your room in the time domain is very revealing

It's an omni mic and yes I have the cal file. It's interesting that measuring all five speakers and the sub full range gives me a small shelf in the bass, which isn't unpleasant. Since every speaker is capable to 40hz, I think I might try a large with main+lfe setup and see how it works out for me.

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[everettT]

It's an omni mic and yes I have the cal file. It's interesting that measuring all five speakers and the sub full range gives me a small shelf in the bass, which isn't unpleasant. Since every speaker is capable to 40hz, I think I might try a large with main+lfe setup and see how it works out for me.

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I was just asking if you needed a mic, as I understood it that you barrowed one. The DBX is ruler flat from 20 to 20. It just can't measure my subs . Works great for all other speakers.

 

[yepimonfire]

Oops. Should have read 3 1/2 feet, Tapatalk not allowing me to edit the post now.

 

[yepimonfire]

Finally settled on the 1200 in the left front and the 1500 in the rear right corners, with an 80hz xover and the 1200 flipped 180 degrees, this gives a very uniform, acceptably flat response around the room. Unfortunately my cpu fan died right after taking the measurements so nothing to upload, but I'm pretty happy with the results given the circumstances. Unfortunately, I'm still missing the bottom octave for some reason, but I intend on adding a minidsp in the future to try to correct that, since I can manage it with equalizer apo on my pc without loss of headroom.

With the two subs, I have a ridiculous amount of headroom. A quick test resulted in a 125dB peak with LFE and the volume at +18dB without audible distortion, that was definitely an experience lol.

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[highfigh]

Why are you trying to beat yourself to death with SPL?

https://www.osha.gov/SLTC/noisehearingconservation/

https://blink.ucsd.edu/safety/occupational/hazard-control/hearing/limits.html

 

[yepimonfire]

Why are you trying to beat yourself to death with SPL?

https://www.osha.gov/SLTC/noisehearingconservation/

https://blink.ucsd.edu/safety/occupational/hazard-control/hearing/limits.html

I'm not. The overall LeqA of a movie with multiple 105dB loud peaks is well below 90dBa, and when added to a time weighted average adds up to a very small percentage of a daily dose, in a addition, low frequencies don't have the same effect on hearing, which is why the A weighting curve is down some - 50 to - 20dB at 20-100hz. That spl measurement is almost entirely low frequencies.

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[TheWarrior]

I'm not. The overall LeqA of a movie with multiple 105dB loud peaks is well below 90dBa, and when added to a time weighted average adds up to a very small percentage of a daily dose, in a addition, low frequencies don't have the same effect on hearing, which is why the A weighting curve is down some - 50 to - 20dB at 20-100hz. That spl measurement is almost entirely low frequencies.

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Ok, so you're not beating yourself to death, just your ears if you're listening at 90 dB.

All of this is pretty meaningless if we can't see how your room is laid out.

 

[everettT]

I'd be happy to measure that sub15 and see if it peaked @125 dbs without audible distortion. My two subs would not do it and that's 4 15s measured by Josh.

 

[William Lemmerhirt]

I'd be happy to measure that sub15 and see if it peaked @125 dbs without audible distortion. My two subs would not do it and that's 4 15s measured by Josh.

I thought that was suspect too. He’s also said elsewhere that his rp160’s can do 30hz. Klipsch says 45...huh?

 

[yepimonfire]

I'd be happy to measure that sub15 and see if it peaked @125 dbs without audible distortion. My two subs would not do it and that's 4 15s measured by Josh.

It won't in any normal circumstance. In a larger room (20x12) without substantial room gain gain, it tops out at about 105dB peak when I tested it at 3m using cea 2010 bursts in rew. One of the nice things about the 1500 is it doesn't really show any audible distortion as it reaches its limits, it simply runs out of xmax and hits the back plate.

I only got the 124dB measurement when it was paired with a sub 1200 in a 12x11 room, seated against the rear wall, and both subs were placed in adjacent corners.

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