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Lii Audio 15" full range
Lii Audio 15" full range
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Old 18th February 2020, 07:19 AM   #271
jjasniew is offline jjasniew  United States
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So here's some plots describing the frequency response of what I'm getting using the 18" helper woofers, EQd by a miniDSP.

First are the miniDSP settings, basically I've implemented a 24db LR low pass @ 70Hz, followed by a reverse-rise to 25 Hz (see 1st screenshot). Check out the system measurement at the low end in the 2nd capture. (Realizing I'm a little bass heavy, but always been that way)

Today, I took a spin with REW and made my 1st swept sine measurement. I'm happy because I was able to take it through the process to ultimately create an impulse file - of a corrective filter set it created for me. See snap #3 of the swept sine and the correction it made. (This was just for the F15 alone)

Having saved these files and uploaded them into Daphile, my USB stick music player, it sure sounds different when you engage the convolution filter. Unsure if I like the more correct sound, however I do realize my ears could get used to it. I havent listened to it this way very much yet.

I owe another measurement as a trust but verify step - see how the REW analyzer shows the effect of all the filters it cooked up. I'll use my 15 minute Pink noise recording played back via Daphile...
Attached Images
File Type: jpg MiniDSP_Reverse_Rising.jpg (304.9 KB, 150 views)
File Type: jpg Current Spectrum_12.jpg (349.5 KB, 143 views)
File Type: jpg REW Sweep.jpg (147.2 KB, 145 views)
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Last edited by jjasniew; 18th February 2020 at 07:26 AM.
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Old 18th February 2020, 09:22 AM   #272
KaffiMann is offline KaffiMann  Norway
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I see some squiggles on there that could be related to the LR filter.
Have you tried applying a classic Halogen Bessel per the Rane document?
RANE Commercial - Knowledge Base

Quick'n dirty for 2nd order Bessel:
Desired xo freq x 1.272 = Low pass frequency
Desired xo freq x 0.786 = High pass frequency

I would try that, also with the minidsp. At least before dismissing the minidsp completely, it's not "perfect" in any way. And like mentioned before in this thread, the cheapest minidsp really shines with xo experimentation before purchasing costly passive components.

The reason I am thinking it might be some other issue is that: If the minidsp is working in a well matched setup, the flaws come out really easily with some higher frequencies and especially square waves. Most musical instruments produce sine at high frequencies, so it's usually not a huge issue.

The way I understand your problem, is that it sounds a bit "lean"? IE perhaps lacking a bit upper-bass/low-mid? With your huge passive components it could also be that there's some phase issue when bypassing them?

I apologize for pressing this matter a bit, it's just that, as Dave noted, I've seen several that "junk" their minidsp's. Just seems to me it's for the wrong reasons.
If you're done or don't want to deal with this, I'll just bow out and stop derailing the thread.

Nice that you've found a driver that you like, there's something about big FR's.
(Ps. Use the distortion plot which is automatically 1/12th octave smoothed, it looks nicer and it contains mostly relevant information in regards of the listening experience, helping you see what to improve and what you can put aside. Also set the borders so you can get 5db/div, use the distortion plot to hunt down various areas of improvement)
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Old 18th February 2020, 06:27 PM   #273
Dadbeh is offline Dadbeh  United States
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is there an fr file for f-15 that can be used in vituixcad?
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Old 19th February 2020, 05:07 AM   #274
jjasniew is offline jjasniew  United States
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I'm just beginning to understand the REW filters. It provides a set, but you dont have to use 'em all, if you're partial to NOT having a pile of high order filters your audio signal runs through.

It's nice that you can click each on on/off and see the effect on the FR plot. Certainly at this stage of the game I dont need to make it "perfect", as it's a 1 Meter more or less on axis measurement point - not even at my listening position.

I can however "de-characterize" the F15's natural response using broader strokes, versus trying to address every wiggle seen in the FR with a high Q filter cut/boost. For example, the generally rising response between 300 and 2K. I'm trying to modify REW's suggestions to come up with a minimal filter set that makes this driver even better to listen to, than with no EQ.

Or perhaps the signal phase is getting knocked about by each and every wiggle - integrating on the high side of the bandpass, differentiating on the low - and the opposite corrective filter puts them back in their proper place, FAIK. Therefore the best sounding situation, for any given driver, would be to address each and every one; not only for amplitude correctness but phase also.

Maybe I'm just dreaming aloud here and that's not how it works. One way or the other should be best and I certainly dont know ;') Sometimes I just wish there was a normal graphic EQ - with sliders - that would output this .wav pulse for the convolution filter based on whatever levels the bands were set to.
Like the 31 band in Equalizer APO - but with just a convolution filter pulse output.
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Last edited by jjasniew; 19th February 2020 at 05:20 AM.
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Old 19th February 2020, 02:12 PM   #275
KaffiMann is offline KaffiMann  Norway
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I like to nudge some of the more general dips & peaks a bit before doing another sweep, some times a little nudge in one part of the spectrum seem to influence response far away. It often pays off to hunt for resonant behaviour using the distortion plot and starting with the more troublesome peaks&dips, quite often the rest will look more tidy after doing a few tweak/sweep rounds on the biggest problems. Go for nice behaviour perhaps 5 to 20 or 10-30 or something, don't pay much attention to 0.

I don't pay attention to the REW auto thingy, it just looks at response and does nothing for resonance issues. Sometimes it sounds worse than no eq.
Always do another sweep after applying or tweaking any setting.

Edit:
The last few years I've been using this as a sort of standard routine and just forget about degrees and everything:
Run 4-6 sweeps in and around listening position (I usually stay within ca 1 to 1.5 meters), apply 12th/octave smoothing on all, look for peaks and dips that coincide on all measurements, adjust eq, repeat.
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Last edited by KaffiMann; 19th February 2020 at 02:22 PM.
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Old 19th February 2020, 06:38 PM   #276
jjasniew is offline jjasniew  United States
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Thanks, KaffiMann. Looks like I have a new facet of this hobby, to play ad-nauseum with the infinite combinations of filters and Qs now available to me for EQ. I'm going to assume that in this day and age, most listeners "resort" to using some kind of EQ - or simply let their own ears train-out a mild "forward sound" to a major "rip your ears off" rising response.

Masters at this have told me they just like the sound of their (Lowthers) even though they realize the FR isnt ideal - it's the other qualities of the driver that, for them, reign supreme. I've only "de-characterized" the F15s with the EQ to make them appear a little flatter across the range.

So here's the latest FR plots - 18" assist included - with a reduced set of EQ bands obtained from REW. Gotta remember to SAVE those EQ settings! It's not that hard to recreate from the initial measurement...

The one dip just above 200 is there with any speaker I use in the same position - so I discount that as being Lii F15 specific. There's still some tweaks I can do on the miniDSP low pass function, but it's performing fairly well now. I've included 1/12 and 1/48 octave plots. Listening to them now I'm finding no objections with the gorgeous soundstage and sometimes scary player presence in the room.

I'll eventually follow up with some listening material review as heard through these as a wrap to this project. I realize I've just scratched the surface of what I can do with available multichannel sound cards, usb to I2S to miniDSP, analog implementations of 24 db LR filters with reverse rising response on the low-pass, REW and filter impulses - etc. So I know you're never quite "done".
Attached Images
File Type: jpg 1M-12th octave analysis.jpg (329.2 KB, 64 views)
File Type: jpg 1M-48th octave analysis.jpg (370.1 KB, 66 views)
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Last edited by jjasniew; 19th February 2020 at 06:40 PM.
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Old 19th February 2020, 09:39 PM   #277
KaffiMann is offline KaffiMann  Norway
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Quote:
Originally Posted by jjasniew View Post
Thanks, KaffiMann. Looks like I have a new facet of this hobby, to play ad-nauseum with the infinite combinations of filters and Qs now available to me for EQ.
... Yeah, it's a bit double edged, like most compromises. Just try and go for minimum amount of eq needed for flat-enough response, you can get almost better results doing "less is more". But it takes more fine-tuning to get it just so. Modes under 300hz or so need a bit of brute force though. Do adjust a bit to taste, after a bit of tweaking most end up in the vicinity of the "JBL tilt". There's no right here, as long as you're happy that's all that counts.

Next up: Getting focused towards S/N ratio and start listening for noise floor in the recording studios.

Hope I'm not ruining your hobby
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Last edited by KaffiMann; 19th February 2020 at 09:42 PM. Reason: There was an in there, don't wanna confuse people with the Norwegian alphabet..
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