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ClaudeJ1

Quarter Pie Bass Horn: Measured FR, How2Build, and Hornresp

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Cross over point? It behaves well almost to 1khz so would i t be ok to 650-700hz? My mid horn is 340hz and they say it should be crossed 1 octave higher than this.   Your thoughts please.   Many thanks Dave 

 

With a 4th order Linkwitz-Riley digital xover, you can cross anywhere from 350 to 500. I'm confident you will prefer the sound at a lower xover point. but it's up to your ears and your measurements. 

 

Just remember the basic physics here. Will 2-4" super light voice coil driving a super light and STIFF diaphragm thought tiny phase plug slots in a straight horn have better transient response and micro detail than the mass rolloff of a 15" woofer's relatively heavy cone bouncing a 350 hz. signal off a 90 degree relfector? Now you know why I like a lower crossover point if possible. That being said, you still want to try and match the polar response between the two horns.

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Now you know why I like a lower crossover point if possible

 

Also, the lower the crossover point, the closer we get to the frequency where the coverage pattern no longer matters.    In my room that's ~ 200hz.

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no such thing as a stupid question

 

1000%

 

impossible...   :)

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OK, so if I drop the cross over point to say 350hz will my 6681 handle it? What about the band width , if I lower the cross over will I need to reduce the upper limit ? Seems like we're asking a lot for it to work from 350 to 10k, (remember no tweeter yet....) I do like the thought of one driver covering the critical range.

Sent from my D5833 using Tapatalk

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Cross over point? It behaves well almost to 1khz so would i t be ok to 650-700hz? My mid horn is 340hz and they say it should be crossed 1 octave higher than this.   Your thoughts please.   Many thanks Dave 

 

With a 4th order Linkwitz-Riley digital xover, you can cross anywhere from 350 to 500. I'm confident you will prefer the sound at a lower xover point. but it's up to your ears and your measurements. 

 

We are running a 400Hz crossover with a 40Hz HP (we are crossing over to the DTS-10s at 60Hz), and I like the way it sounds. ;)

 

Left%20bass%20bin_zpsecz6wvcm.png

Edited by ellisr63

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Hi all

Thought it was about time I posted a response trace of the horns. 

The red trace is combined left and right at the listening position (adjusted down for clarity), the other 2 are LH & RH at 1 mtr all smoothed to 1/6. 

 

Is it correct that all we should aim for with 1/6th smoothing is + - 5 db? With 12 and 24 there are too many sharp peaks and dips to do individually.... 

 

Also should I eq each one at a time then check overall or can I link the channels and just look at overall?

 

I think I may have been trying too hard to adjust each and every peak and dip, what should I really focus on with eq?

 

 

Would love to here your thoughts.

 

Cheers Dave

post-62431-0-64220000-1467364065_thumb.j

post-62431-0-83500000-1467364081_thumb.j

Edited by nzlowie

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I think I may have been trying too hard to adjust each and every peak and dip, what should I really focus on with eq?     Would love to here your thoughts.   Cheers Dave

 

Ideally, you should be high pass filtering the Quarter pie at 60 Hz. IF you want to minimize cone motion and avoid IM distortion, then bring in a Sub below 60 Hz. You can push that down to 50 Hz., if you are not that picky. But I believe that all speaker setups need a minimum of 3 subs to excite all the room modes and flatten out the bass. Woofers need to work really hard for that bottom octave or two and that is best handled by up to 4 subs. 

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I think I may have been trying too hard to adjust each and every peak and dip, what should I really focus on with eq?

 

Assuming you've taken these in a typical sized room, then above ~300Hz, we can see your speaker, and +/- 1.5dB is a good target.    Look at each driver in a speaker separately, and also combined....   so you should be looking at the left speaker, with 3 separate traces.   QP.  Midhorn.  Combined.    This will allow you to investigate each driver, so you can get the crossover summing, and the driver levels right.

 

There are almost no situations where you want to look at the left and right speaker played together.

 

Below 300Hz, we're somewhat looking at your room.     If you take measurements from various locations, they will vary more below 300Hz, and so it's hard to design EQ which makes the response flat at more than a limited number of points in space.    +/-2.5dB is a good target, but you might only get +/-5dB in the bass.

 

You will see more effects from the room as you move the microphone further away from the speaker.

 

The question "should I work really hard and EQ all the peaks and dips flat"  is not a simple question.     The short answer is you want to get rid of the peaks/dips .... but you don't want a situation where it is made flat for the location you had the microphone at ... but when you move the microphone elsewhere, the EQ makes the response worse.

Edited by davewantsmoore

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I think I may have been trying too hard to adjust each and every peak and dip, what should I really focus on with eq?     Would love to here your thoughts.   Cheers Dave

 

Ideally, you should be high pass filtering the Quarter pie at 60 Hz. IF you want to minimize cone motion and avoid IM distortion, then bring in a Sub below 60 Hz. You can push that down to 50 Hz., if you are not that picky. But I believe that all speaker setups need a minimum of 3 subs to excite all the room modes and flatten out the bass. Woofers need to work really hard for that bottom octave or two and that is best handled by up to 4 subs. 

 

I set mine at 40Hz...as from what i understood at the selected HP frequency it is already down. I am forced to either crossover at 40Hz or 60Hz with my Yamaha AVP. Should i raise the HP to 60Hz with the DTS-10s?

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I set mine at 40Hz...as from what i understood at the selected HP frequency it is already down. I am forced to either crossover at 40Hz or 60Hz with my Yamaha AVP. Should i raise the HP to 60Hz with the DTS-10s?

 

Depends on what SPL you are trying to make.    If you're not trying to run an outdoor rock concert, the 40Hz is probably fine.

 

 

I use a butterworth first order highpass filter on mine  (-3dB @ 50Hz with a 6dB/ocatve slope).    The horns natural response is about -3dB@50Hz, with an 18dB/octave slope.

 

.... and the result is a -6dB point @ 50Hz, with a 24/dB octave slope.

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I think I may have been trying too hard to adjust each and every peak and dip, what should I really focus on with eq?

 

You should focus on minimum phase behavior. A phase plot is the best way to determine that. A Bode plot of frequency vs amplitude only tells half the story. However, it is difficult to get accurate phase information from a speaker in a room because of reflections and standing waves. What people who do not have access to an anechoic chamber usually do is to run frequency and phase curves with the speaker outdoors away from any boundaries. The speaker is then EQed  as close to flat as possible with regard to both frequency and phase. Bear in mind that the phase response of a woofer or subwoofer will never be perfectly flat. The goal is to have a smoothly changing phase plot.

 

When you get the speaker back in the room run another frequency response plot. The difference is you see is because of the room. Apply room treatments to minimize the differences for best results.

 

It's not a good idea to run these tests at 115-120 dB SPL. You could be looking at distortion products in the output of the speaker that may cause erroneous readings. Horn loaded woofers have less distortion and less of this effect than direct radiators though.

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I set mine at 40Hz...as from what i understood at the selected HP frequency it is already down. I am forced to either crossover at 40Hz or 60Hz with my Yamaha AVP. Should i raise the HP to 60Hz with the DTS-10s?

 

Depends on what SPL you are trying to make.    If you're not trying to run an outdoor rock concert, the 40Hz is probably fine.

 

 

I use a butterworth first order highpass filter on mine  (-3dB @ 50Hz with a 6dB/ocatve slope).    The horns natural response is about -3dB@50Hz, with an 18dB/octave slope.

 

.... and the result is a -6dB point @ 50Hz, with a 24/dB octave slope.

 

If I have my AVP crossing the LFE @60Hz, and I set the HP @ 60Hz it will be several DB down at the crossover point...that is why I set the HP @40Hz. Should I raise the HP to 60Hz, and let it have the dip at the 60Hz crossover?

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If I have my AVP crossing the LFE @60Hz, and I set the HP @ 60Hz it will be several DB down at the crossover point...that is why I set the HP @40Hz. Should I raise the HP to 60Hz, and let it have the dip at the 60H crossover?

 

If you are using your room correction on the AVP (bass management and LFE are related but different), the it will usually pick what's "best" if you don't restrict the subwoofer response. However, Tapped Horn Subs get quite "ringy" aavobe their 2 octave response, so if you use a 4th order ButterworthI bandpass filter from 14-60 Hz. you will avoid having your AVP's speaker correction from mistaking any ringing above that 60 hz. as higher output (does not sound good that way).

 

The Quarter Pie's cone excursion goes up substantially below 60 Hz., which is why I recommend crossing there. However, 50 works very well also, and some feel it sounds better that way. It's up to your room, your ears, and your sweet spot as to what works best for you and your listening test material.

 

Besides, what's a few lower Hertz among friends, when you agree Plus or Minus 10 Hz.!!

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If I have my AVP crossing the LFE @60Hz, and I set the HP @ 60Hz it will be several DB down at the crossover point...that is why I set the HP @40Hz. Should I raise the HP to 60Hz, and let it have the dip at the 60H crossover?

 

If you are using your room correction on the AVP (bass management and LFE are related but different), the it will usually pick what's "best" if you don't restrict the subwoofer response. However, Tapped Horn Subs get quite "ringy" aavobe their 2 octave response, so if you use a 4th order ButterworthI bandpass filter from 14-60 Hz. you will avoid having your AVP's speaker correction from mistaking any ringing above that 60 hz. as higher output (does not sound good that way).

 

The Quarter Pie's cone excursion goes up substantially below 60 Hz., which is why I recommend crossing there. However, 50 works very well also, and some feel it sounds better that way. It's up to your room, your ears, and your sweet spot as to what works best for you and your listening test material.

 

Besides, what's a few lower Hertz among friends, when you agree Plus or Minus 10 Hz.!!

 

The only thing I have done on the DTS-10s is to use a 10Hz HP with a Butterworth 24DB (as per Danley). I wanted to run a 50Hz crossover, but my Yamaha only gives me 40, 60 or 80Hz options. Should I change the HP on the 1/4pies to 60Hz, and accept the dip from the crossovers then?

Edited by ellisr63

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The only thing I have done on the DTS-10s is to use a 10Hz HP with a Butterworth 24DB (as per Danley). I wanted to run a 50Hz crossover, but my Yamaha only gives me 40, 60 or 80Hz options. Should I change the HP on the 1/4pies to 60Hz, and accept the dip from the crossovers then?

 

I would try it. Then your YPAO should end up choosing 60 hz. for the DTS-10's, one would think. It's worth a try. You can always go back and undo it if it doesn't sound better. 

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Hi Team

 

Can you please have a look at the response sweep for my quarter pie horn and let me know what you think..... The mic is just at the edge of the horn so hopefully not too much room influence.

 

I thought it would have been better than this so I'm picking there's something wrong. I'm trying to avoid using the minidsp as this kills the sound stage of the other horns...

 

What do you think?

 

Cheers Dave

post-62431-0-19900000-1468833688_thumb.j

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Nothing is wrong. You have a built-in Fletcher-Munson/ISO equal loudness compensation for the bass. Now match that to a good subwoofer (preferably full or tapped horn) and you are set. I'm assuming the top end picks up between 300-500 Hz???

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