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ClaudeJ1

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

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17 hours ago, nzlowie said:

Just thought if the standing up or opening up the mouth reduced this 160hz peak

 

You're only looking at it form one point in space.     Take 10 measurements with it vertical, and 10 with it horisontal from different positions across the room - and see what trends show up.   I'm sure you'll find that the vertical orientation is not substantially better.    I think the right way to orient the horn, is whatever way lets you arrange the mid horn best  (height, distance to QP mouth, etc.)

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When I had my original 3-way setup, I found that having the Quarter Pie laying down was ideal for a K-402 horn, in fact, the tweeter was above my ear level slightly, so if your treble horn is BIG enough, the Quarter Pie lays down some bass and midbass quite nicely laying down...........pun intended.

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They're back laying down as designed.... The mid/tweeter horn ended up being too high and I didn't want to mount it off to the side.

Anyway pretty happy at the moment!

Thanks again for the guidance...

Sent from my Moto G (4) using Tapatalk

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On 3/23/2017 at 1:01 AM, nzlowie said:

They're back laying down as designed.... The mid/tweeter horn ended up being too high and I didn't want to mount it off to the side.

Anyway pretty happy at the moment!

Thanks again for the guidance...

Sent from my Moto G (4) using Tapatalk
 

Where are you located?

 

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On 3/24/2017 at 9:59 PM, nzlowie said:

Perth Australia.

Sent from my Moto G (4) using Tapatalk
 

Are you using a sub for the sound down under down under?

 

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Hi Claude
No sub, this is a 2 channel system so I don't think I'm really missing out on much. When there is good genuine bass on the recording these sound great.

The system as a whole is 100% so I don't want to throw another variable into the mix.

Maybe later......

Cheers

Sent from my Moto G (4) using Tapatalk

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On 3/29/2017 at 6:23 PM, nzlowie said:

Hi Claude
No sub, this is a 2 channel system so I don't think I'm really missing out on much. When there is good genuine bass on the recording these sound great.

The system as a whole is 100% so I don't want to throw another variable into the mix.

Maybe later......

Cheers

Sent from my Moto G (4) using Tapatalk
 

Can you measure from your sweet spot? Something like pink noise with RTA?

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Sorry for the late reply.
Not sure how to measure this... I sort of know how to use REW and that's about it!
A long way short on knowledge when it comes to measuring speaker's...

Sent from my Moto G (4) using Tapatalk

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6 hours ago, davewantsmoore said:

Just taking a sweep in REW is equivalent to what he's asking.

That will do it.

 

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So, all you Quarter Pie builders out there, how is your BASS? Still good?

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Update time...

 

A few posts ago I mentioned that I tried running the quarter pie standing up. Well, revisited this and WOW very happy!

The reason I revisited this was I had a weakness in the mid bass area, not in measurements but "punch" or "attach". The FR was there but without impact. My thoughts were that as the upper end of the QP horn was probably becoming directional it was "getting to me". I only sit a few meters back from the horns and I think the mid bass just hugs the floor, standing them up points them directly at me.

The other benefit I was looking for was a flatter response, with the QP standing up the in room response was pretty flat from 50hz to 1khz. This meant I could just have a passive xover and eliminate the minidsp. I was keen to remove the dsp as it would reduce the time delay between the bass horn and mid horn. The mid horn driver sits further forward than the bass driver then add latency of the dsp and the distance between drivers is exaggerated. Mybe not a issue at the lowest frequency but I'm sure around the xover point it could be.

Very happy with the results now. Before we had beautiful vocals and acoustic music but it lacked the kick for rock music. We now have that as well !!!  

 

Only thing that I lost was some of the bottom end, really need a sub now where I could have lived without before.

 

Now I want to do a passive high pass filter for the QP to limit the out of band output. The distortion really increases below 50hz.

Trouble with a low frequency filter is the size of the capacitors, 600-700uf . Is this ok to use such big capacitors on the bass channel?

 

Anyway, just thought I'd share my finding and thoughts.

 

Cheers Dave

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The dsp should be used to delay the compression driver (mid/tweet), not the bass.

 

Bruce

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Bruce, not going to put minidsp back in the mid/tweet section. Tried minidsp early on in this project, just kills sound stage and imagery. Not going to happen!
The delay induced by the minidsp on the bass horn is an unwanted side effect of needing it for EQ.
Sound quality without minidsp is just beautiful, only thinking about it to chop the lowest octave that the horn can't produce.
Or go passive..... If the team think the massive amount of capacitance needed won't affect sq too much.

Sent from my Moto G (4) using Tapatalk

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15 hours ago, nzlowie said:

Trouble with a low frequency filter is the size of the capacitors, 600-700uf . Is this ok to use such big capacitors on the bass channel?

Yes, it's OK to do this, which is a first order highpass filter. When I looked at the Hornresp data, it showed a huge increase in cone excursion below 60 Hz. so that should be your target subwoofage. I would highly recommend building what I called my "coffee table Tapped Horn sub" with ONE Eminence LAB12 Driver, and and 2 sheets of 4x8 Plywood or MDF. It's ruler flat from 20-60 Hz. and you could make use or your Mini DSP to do a bandpass filter from 16-20 Hz. to 60 Hz with 24 db/ octave slopes. You would then have the best of both worlds.

LAB12TH.jpg

IMG_0066.JPG

IMG_0966.jpg

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Thanks Claude, that will do the job nicely.... As this will be placed flat against the front wall between the main horns is it ok to change the opening from being on the side to the front? Same distance from the end just moved 90deg.

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I won't try to convince you to use the Minidsp, but I'm curious about your signal path when you were using it.

 

Bruce

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Signal path was: Rpi with hifiberry digi+ feeding a Klien DAC (Australian). This then feed a Weston Topaz amp (Australian) driving the mid horn and a class D amp driving the bass horn. Tried manyyyyy different settings but each time I went back to a simple passive xover the sound stage and imagery just opened up. (Same amp) Sure you could get the minidsp system to measure better but it never sounded as good as passive, no matter what xover or filter settings were used. Compressed sound stage, it was there just not as wide or as deep as with a passive xover.

Once I gave up on the minidsp and spent time sorting out the passive xover it really came alive.

 

To my mind the minidsp is a budget piece of kit, can't expect it to perform miracles.

I know others think they're great but not me.

Also got sick of people telling me it must be the way I set it up, it was almost like I was a blass femer for questioning it's capabilities!

 

Anyway, very happy with most of the system now. Get a sub and hi pass the QP horn and that will be it!

Of the system's I've heard lately the only one that betters my was a hi end ML, Accuphase and​ Bakoon system. Having said that if I get a bit more lower bass mine will kill it on rock music.

 

 

Sent from my Moto G (4) using Tapatalk

 

 

 

 

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4 hours ago, nzlowie said:

Thanks Claude, that will do the job nicely.... As this will be placed flat against the front wall between the main horns is it ok to change the opening from being on the side to the front? Same distance from the end just moved 90deg.

Sent from my Moto G (4) using Tapatalk
 

Yes, you've got 3 sides to choose where the exit port goes, as long as the dimensions are the same. You can then just use the mini DSP as a bandpass filter from 20-60 Hz. at 24 db/octave, or even 48 db/octave if you dare (LOL), where the Tapped Horn is RULER FLAT. Don't forget that the lower cutoff on a horn (Quarter Pie included) is about 18 db/octave, so adding a bunch of film capacitors in parallel (100 uF is the largest one I found at a reasonable cost) will make the Acoustic 18 + the capacitive 6 db/octave total 24 db/octave which will match the low pass slope you can dial in on your Mini DSP. This will not affect imaging, etc. as you have experienced since the subwoofer frequencies are not critical to imaging at all.

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