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Tarheel TJ

Replacing the K400 with the 11"x17" ZXPC Horn

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13 minutes ago, No.4 said:

...so what sounds right to me is probably the uncorrected peak @1800hz? 

 

Well, probably not so much, but rather that some selected recordings have way too much SPL in the 500 Hz region, and perhaps a more moderate amount of SPL in the 1-3 kHz region (precious few recordings, however), and many have too much SPL in the 3-4 kHz region, which will be attenuated by this horn/driver without EQ correction. 

 

If you find a recording like that, it will probably sound better than a loudspeaker that's playing the source music pretty much flat SPL with frequency.

 

I've also found that there are more than just a few individual tastes that like a whole lot of SPL in the 2-4 kHz band (and higher frequencies), so those people will likely prefer loudspeakers with even more emphasis in that region. 

 

I've found that for myself--flat SPL with frequency is something that sounds quite natural for the genres of music that I listen to--particularly after unmastering those recordings. See the following thread for an explanation of what "unmastering" means...

 

Chris

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Really interesting to see the frequency response of this setup.  Thanks for posting Chris.  I have really been wondering what that would look like.  
It appears some EQ is definitely needed to get these to measure flat.  I wonder how much of the peaks and valleys are caused by the adapter setup vs. the shape of the horn?  My guess is that either the valley at 500hz or the peak at 2000hz are a result of reflections caused by the mismatch between horn/adapter/driver, maybe both?

 

No. 4, I have noticed the mid-bass seemed a little stronger with these horns.  I chalked that up to the upper-midrange shout of the K400 being gone, making the mid-bass seem stronger by comparison.  It looks like what I may have been hearing was actually the giant hole in response at 500hz.  I'm sure that did make the mid-bass seem stronger!

 

Even with the frequency irregularities, they are still an improvement to my ears.  The harshness of the K400 is very bothersome to me.  These alleviate that completely.  I guess I need to get a measurement mic and a DSP setup and see how that improves things.  I bought this setup thinking it was a cheap upgrade.  Sounds like I just talked myself into spending another $300....

 

 

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4 hours ago, Tarheel TJ said:

I wonder how much of the peaks and valleys are caused by the adapter setup vs. the shape of the horn?

I would tend to believe it's more a function of the driver.  When you look at the K-400/401 horn, it begins to lose vertical polar control  precisely at that 1700-1800 Hz point (the famous "collapsing polars" midrange horn design), just as the frequencies that are in excess occur in the present horn/driver configuration. 

 

Paul Klipsch mentioned that he spent more time developing the K-400 midrange than the Khorn bass bin.  I assume that was due to the very low crossover point (400 Hz) to the bass bin, the requirement for very flat response (without EQ in the crossover) in the midrange and low treble from the midrange horn, and the relatively high crossover point (4.4kHz-6 kHz) to the tweeter.  Both crossover bands are fairly narrow (in my opinion...using active crossovers to replace the passives and searching for better crossing frequencies and steeper slope filters).  So the design of the Khorn was something of a work of engineering.

 

Chris

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Thanks to the information in this thread I bought some of these horns, even without an intended project. They are nice quality ABS plastic. I just connected one to the right channel and it sounds good.

 

 

Z horn.JPG

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On 10/24/2016 at 5:10 PM, Chris A said:

So the design of the Khorn was something of a work of engineering.

Gee, do ya think?;)

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Just FYI--my calculations say that the junction between the horn adapter and the horn itself corresponds to a frequency of about 800-900 Hz.  I just pulled up my REW measurements of the K-55V on this PRV 1"-2" adapter and ZXPC horn, and saw a little wiggle in the phase curve at that frequency.  Since I didn't do anything to smooth that transition, I would have expected to see that when I took the measurements (assuming that I did the calculations in advance---which I didn't). See the SPL + Phase curve below at about 850 Hz for that little wiggle:

 

K-55V on PRV adapter+ZXPC horn.png

 

Modeling clay should smooth that transition nicely.

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On 10/24/2016 at 7:10 PM, Chris A said:

Both crossover bands are fairly narrow (in my opinion...using active crossovers to replace the passives and searching for better crossing frequencies and steeper slope filters).  So the design of the Khorn was something of a work of engineering.

 

Please remember that this is the actual context of what was said. 

 

I was actually amazed that the narrowness of the crossover band from bass bin to midrange and so unable to be shifted in frequency. The same is true for how tenuous the midrange-tweeter crossover is, i.e., for most Khorns that exist having no electrical low pass filter on the midrange up until quite recently in terms of its 70-year lifespan. 

 

I believe that given today's choices in drivers and horns, I'd choose a bit more overlap in driver/horn frequency response at both the crossover regions (in fact implemented in the Klipsch Jubilee by PWK and Roy). It makes the job of supplier quality much easier to manage, i.e., changes in frequency response of the drivers by suppliers drifts over time (K-33, K-55, K-77). 

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This horn is worth an extended listening trial. My application of Dynamat to the outside surfaces is a personal preference. It reduces the possibility of resonance, from within or from external subwoofer vibrations. The mat is self adhesive once the protective backing is removed, so line up carefully before sticking it on. Press lightly from the center toward the edges to avoid trapping air pockets.

 

 

Dynamat on Z-horn.JPG

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Did you notice an audible improvement with the dynamat?  I had rope caulk on my K400s, but so far I am running these horns naked.

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I did not compare before and after, just tapped on the horn body with my fingertips and decided to apply the Dynamat vibration damping material. It is also recommended to mount the horn onto a baffle board, (or a decorative oak frame that matches your tweeter stand) to stiffen the horn body. Mark and pre-drill pilot holes to make it easier to screw the horn mouth flange to a new baffle board.

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Yeah, I built a pair of oak frames to serve as a baffle for my K400s before.  I plan to do the same for these, just haven't gotten around to it yet.  I may try some dynamat as well.  It can't hurt, right?

 

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The picture on the left, of the PRV Audio ADM25-50 1-3/8" 18 TPI Driver to 4-Bolt 2" Horn Adapter, appears to have a different taper than the P-Audio PC5025, 1" to 2" adapter (and Selenium ADF25-25, 1-3/8" 18 TPI to 1" Adapter) in the other pictures. The two piece set costs more, but looks like it might be a better match for the throat profile of the K-400/K-401.

 

IMG_3032.JPGIMG_9630 1.JPGIMG_9634 (1).JPG

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Would a jbl d408ti work with this horn. 2 way 400hz up.

 

 

 

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Yes it would, but it would need to be carefully dialed in.  The on-axis curve using another horn looks to have sufficient LF and HF response, but there looks to be a diaphragm or phase plug drop out at 8 kHz: https://www.parts-express.com/pedocs/specs/264-216--d408ti-spec-sheet.pdf

 

I don't recommend passive crossovers to do it unless you're pretty good at passive crossover design with compensation (i.e., equalization).  It's assumed that you would measure at least the on-axis frequency response using something like REW and a calibrated microphone in order to flatten the response effectively.

 

Chris

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12 hours ago, Chris A said:

Yes it would, but it would need to be carefully dialed in.  The on-axis curve using another horn looks to have sufficient LF and HF response, but there looks to be a diaphragm or phase plug drop out at 8 kHz: https://www.parts-express.com/pedocs/specs/264-216--d408ti-spec-sheet.pdf

 

I don't recommend passive crossovers to do it unless you're pretty good at passive crossover design with compensation (i.e., equalization).  It's assumed that you would measure at least the on-axis frequency response using something like REW and a calibrated microphone in order to flatten the response effectively.

 

Thanks! I have a chance to get a pair of jbl d408ti cheap. This looks similar to the jbl hl 4750 so thought it might be worth a try.

 

Chris

 

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18 hours ago, Ljk said:

Thanks! I have a chance to get a pair of jbl d408ti cheap. This looks similar to the jbl hl 4750 so thought it might be worth a try.

 

I guessing you mean Selenium d408ti...

 

They are owned by JBL now, so you are pretty much correct.

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takes a very special comp driver to be used two way down to 400Hz. not very many up to that task, would love to see a list probably count them on one hand.

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6 hours ago, moray james said:

takes a very special comp driver to be used two way down to 400Hz. not very many up to that task, would love to see a list probably count them on one hand.

Yes selenium jbl d408ti. Read it can sound kind of rough below 650hz, specs show good from 400 to 20khz. Anyway it should to fun experiment with these horns without breaking the bank. I would like to see a list also.

 

 

Faital pro 2000

M200

?

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EV DH1A (3" ti diaphragm) and JBL have some 3" and then 4" units which were designed for this type of application. A 1.4" exit is nice as it helps extend range with less EQ. Most big drivers which were designed to do this job are 4 inch diaphragms with 2 inch exits that work with very large horns which can hold polar response down that low and they simply don't fit typical domestic settings. There are other drivers I am sure but you have to look hard today to find any modern designs intended for this application, they are all very expensive and not in demand in a market that uses a less expensive more flexible multi way approach.

   You are not going to get flat to 20 KHz. with a two way but you will get far out enough to make you happy. Good two ways have a nice set of compromises and they sound "right" or "believable" there is a reason why the high efficiency two way studio monitor by companies like Altec JBL and Tannoy (though less efficient) etc. ruled supreme in the worlds recording studios for over three decades.

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 The zxpc eBay store has many different horns with no model numbers or specs. Their only designation is the horn size. The one I pictured several posts earlier is the 11" X 17" , which appears to be a copy of a 40 X 20 degree Selenium 2" horn with a lipped flange. The one in this picture is the 18" X 10" , which looks like a copy of a 90 X 40 degree 2" horn with a flat face flange. They are well made ABS plastic horns.

 

IMG_1134.JPG.b323f2ddb705d2b209c695043654472f.JPG

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