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Dave A

KP-904 questions, crackle in HF

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First thank you for taking your time out.

 

Second, you're right in that I was taking my measurements at the listening position.  I thought searched enough threads about the subject but I guess not.  Here is what I intend to do:

 

1. Take measurements 1 metre from the speaker.  I have carpeted floor with padding, 95% of my ceiling is made up of acoustic paneling. I will also put two acoustical panels on the sides of each speaker and take REW measurements this weekend from varies heights.

 

2. Evalutae the data.

 

3. More than likely buy a Xilica vs. a new passive xo after I buy @Westcoastdrums amp next week if it doesn't sell by then.

 

4. Hide both the amp and Xilica from wife.

 

5. Play with it. Make wife jealous. (Please no jokes here)

 

5. Have a CRAP LOAD of questions.

 

6. Smile.

 

7. Work on a Subwoofer....or two and piss wife off.

 

8. Fly @Chris A (and pay$) to listen and evaluate.  Dinners will blow you away.

 

9. Finally have the system where I want it.

 

10. Start all over and build some 402 MEH's!  Thanks Chris.

 

 

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I should qualify some of my remarks about "BS in the video":

 

1) Almost all of these types of REW tutorial videos are making assumptions about what the viewers own, and one of those assumptions is that they all are using loudspeakers with direct radiating drivers.  On the Klipsch forum, this isn't a good assumption (almost everyone here is using loudspeakers with at least HF horn-loaded drivers, and many with full-range directivity like La Scala, Belle, Khorn, Jubilee, and MWM owners), and it causes issues throughout the videos in the advice given.  To give you a feel for how much it affects the Klipsch owners here, note the the presenter's comments on the 500-700 Hz ceiling on EQing your loudspeakers using REW in-room are just invalid, and his advice that home theater rooms should have no higher than 0.3 second reverberation time.  These comments are not correct for Klipsch owners. 

 

2) Using filtered impulse response (IR) plots with 1/3 octave filtering is a laborious and not-so-productive way to see the room's resonances.  It also isn't terribly useful to most Klipsch owners, for the reasons stated just above.  He calls the spectrogram plots "wavelets".  This is extremely confusing and pointless, especially to beginners (as the presentation is named for).  They are spectrograms, and the presenter doesn't know how to read them.  If he did, he would abandon the filtered impulse response and waterfall discussions that he introduced (badly). 

 

3) Rooms do not exhibit "minimum phase behavior", nor do most loudspeakers with passive crossovers.  Loudspeakers of the types sold by Klipsch all exhibit mixed-phase behavior, and home-sized listening rooms exhibit the same thing.  This is important for journeyman REW users, but not really beginners.  He should have left well-enough alone and avoided the subject altogether.

 

4) Like most people used to using "room correction software", the presenter is confusing how to EQ loudspeakers at higher frequencies (above 200 Hz) with correcting for room mode resonances and cancellations below 200 Hz.  These two subjects are not the same.  Taking measurements at 1 m in front of each loudspeaker individually allows you the opportunity to avoid measuring early reflections in-room (as I've already noted above).  Taking sweeps at the listening position(s) is only valid for bass bin and subwoofer frequencies.  He's confused.

 

5) Using REW's EQ facility is one of the major strengths of the tool.  To say that it isn't very useful says to me that the presenter isn't really very good at what he's doing.  Enough said.

 

6) His comments about "not using too much EQ" are just wrong.  If he actually read Toole's papers that he discussed, he would have to eat his words when Toole gets to the part about desired flatness of the SPL response.  Toole is saying that the desired SPL response flatness is ±1 dB, which this presenter completely negates in all of his discussions.  Additionally, if one were to use FIR filters to further flatten response of the loudspeakers, the presenter's comments about "too much EQ" are completely wrong.  I understand where the presenter is getting his concerns from in this subject area, but he's using a very blunt tool to try to convey them.  Just ignore what he said on this subject and you'll be much better off.

 

I'll stop there.  The presenter is trying to convince you that he knows what he's doing...he really doesn't, however.  He needs more training--a lot more.

 

Chris

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Good information is so hard to find on the web. There is a ton of it out there but you have to be familiar enough with the topic to have a good BS filter. I have viewed that video and others and deleted them when done. Either there are darned few videos on this topic or Googles broken search algorithms keep taking you back to the same clips they make money on and they seem to be OK at best.

 

  Good points on your comments Chris and I am grateful you are willing to help online and in person at SWAG.

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On 2/14/2020 at 4:19 AM, Chris A said:

2) Using filtered impulse response (IR) plots with 1/3 octave filtering is a laborious and not-so-productive way to see the room's resonances.  It also isn't terribly useful to most Klipsch owners, for the reasons stated just above...

BTW: The newest beta versions of REW have a "RT60 Decay" facility that far surpasses the Filtered IR facility in resolution and usefulness (which was recommended in the video in question).  An example:

 

152156230_K-402-MEHRT60Decay(1mon-axis).thumb.jpg.5b6f7fb884f55b5308b775878b47b7ab.jpg

 

 

The help page online for the new "RT60 Decay" facility can be viewed here: http://www.roomeqwizard.com/betahelp/help_en-GB/html/graph_rt60decay.html

 

Chris

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Not at all an expert but this looks like dog poop to me!

 

This was done on 904's with mic 1 metre away, sound panels on either side of the speaker past the mic, carpeted/padded floor and sound panel ceiling.

 

Outlaw audio 990 with Sunfire amp

 

1295717527_left9041metre.jpg.d4a6d20ff699748542d45d4e06b1e3f3.jpg36985186_left9041metrespectro.jpg.98187b85144a107a39d0d94a945d6daf.jpg

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My biggest concern is the drop from 400 to 1Khz.  Could this be due to old passive networks?  Would going the active route correct this?  I know the spike from 100 to 150hz is big too but we're talking a difference of 50hz and not 600hz!  There is a lot being missed here and I tend to believe it's not the room.  Again measurements taken from 1 meter being careful not to get reflections from the room.  Any direction would be helpful.1816857311_9043rd.jpg.4def10be00c75aea725e958bc5a9483a.jpg

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Sure looks like you've got a reversed polarity through that crossover.  If you showed the phase plot in your plots above, it would tell you if you've got a polarity reversal.

 

I'd try reversing the polarity on the bass bin leads to the passive crossover and take another measurement--this time showing the phase trace in the SPL plot. 

 

Chris

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1 hour ago, risingjay said:

Would going the active route correct this?

Yes--if you're talking about a DSP crossover (not analog active).

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Not reversed.  Again from just a single speaker

 

normal.jpg.0ee7208305c473bc3844dc4b8511af92.jpg

 

this is reversing the compression driver

 

reversed.jpg.2c6083670e2f58d598b8c5b19d67692d.jpg

 

Is it my imagination or are you right?  I did not know you had to reverse the polarities on these.  I bought these used so I wonder if anyone has done anything to the passives.

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Voila!  Success.

 

You might want to zoom in a bit on the SPL vs. frequency plot.  I usually use no more than 5 dB/vertical division.

 

Chris

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Went back with the Klipsch OEM crossovers yesterday on these. Decided to dump the 510 Ist gen horns I have and the clones and use 2" Throat Horn Bolt-On 18"x10"For Assorted Bolt On 2"Exit Drivers 90°x 40°(398) | eBay   instead. Also stuck a Zoebel circuit on the back of the DE-75 drivers using a 20ohm resistor and 15uf capacitor and it sounds pretty darned good. This larger horn is better sounding than the 510 clone with Klipsch OEM crossover and the Zoebel as described above. I have no doubt this could be improved on but I can also live with these results. Reminds me a lot of the KPT-456 which I had high regards for now.

 

  I will be trashing all those old brittle 510's and since the bigger horn sounds better than the 510 clone and is the same basic price will be sticking with the big horn.

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