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ClaudeJ1

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

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Thanks Claude

Trouble is when measured from my listening position I end with this response, big drop below 100hz and a hole at 300hz. I've tried inverting phase but can't get bass below 100hz, medium sized room with plenty of bass traps.

As for the 300hz hole, won't be able to get my horn down that low, well maybe if I use a 4th order crossover.....

 

Any suggestion on things I could try to improve things?

 

Thanks for your assistance. 

post-62431-0-46700000-1468839039_thumb.j

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Below 300 Hz. all room responses are modal. It is NOT the fault of the Quarter Pie horn. Bass traps do very little (fantasy world).You probably need to move your listening position and add 3 to 4 subs. Geddes and Welti cover this well.

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Can you please have a look at the response sweep for my quarter pie horn and let me know what you think

 

That seems about right for the horn with no filters.

 

It would be even flatter if measured outside or similar, as at these frequencies there is still some room effects getting into the measurement even with the mic right at the mouth.

 

Thanks Claude

Trouble is when measured from my listening position I end with this response, big drop below 100hz and a hole at 300hz. I've tried inverting phase but can't get bass below 100hz, medium sized room with plenty of bass traps.

As for the 300hz hole, won't be able to get my horn down that low, well maybe if I use a 4th order crossover.....

 

Any suggestion on things I could try to improve things?

 

Thanks for your assistance. 

 

Here are your images overlaid.     You have a narrow dip at 300, which is likely caused by diffraction from the floor (probably ignore it) ....  and you have a strong cancelation ~ 70, 80 Hz, which would imply you are sitting in a node.  (point of cancellation for the room standing waves) .... and so EQ could be tried here, but probably doesn't help.  Solution is bass traps, or moving speaker/listener location.

 

 

Aside from that, everything seems fine.

 

You'd want to take many maeasurements, overlay them, and decide where you might make some minor EQ.    For example, you might want to cut very slightly at 120Hz ....  but you would only do that if there is a peak everywhere at ~120Hz     (So you're not making the response worse in some places and better in others).

 

 

Otherwsie, you just need to setup a filter to low pass the bass horn.    Do this so the bass horn blends in well with the high pass response of the next horn up.

 

My midhorn has a 24dB/octave high pass response, with the -6dB point at ~250.

After EQing out a few bumps ....  My QP has a 6dB/octave low pass response, with the -3dB point at ~ 250Hz.

 

.... so I add a 18dB/octave (butterworth) low pass filter to the QP.... with the -3dB point at 250Hz

 

 

The result is that bass and mid have both 24dB/octave low and high pass responses respectively .... with the crossover point (-6dB) at 250Hz.

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Cheers Dave

Trouble is my mid horn won't go that low, it's a 340. Maybe I could take it lower with a sharper roll off. Don't want to cook the Yamaha driver..... no diaphragms anywhere!

I did try taking some different measurements within acceptable setting positions and yes the dip and peaks were still there, just moved in frequency a bit. As mentioned I didn't try to eq these just a bit of lift at the top and bottom of the range.

Just have to wait now till all the painting is done before I can play again.

Thanks again for everyone's help.

Dave

Sent from my SM-T800 using Tapatalk

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Trouble is my mid horn won't go that low, it's a 340. Maybe I could take it lower with a sharper roll off. Don't want to cook the Yamaha driver..... no diaphragms anywhere! I did try taking some different measurements within acceptable setting positions and yes the dip and peaks were still there, just moved in frequency a bit. As mentioned I didn't try to eq these just a bit of lift at the top and bottom of the range.

 

What Dave said, but at 340 Hz. and you should be fine. If you need to nudge up the Quarter Pie a decibel or two near the Xover point, that should make for a smoother hand off as it will not add any perceptible distortion. 

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Claude, Dave - do you think I should try my 340 horn right down at the lower extremity?

If the horn rolls off at 340hz should we use that as part of xover? So use the roll off at 3db from 340hz then add an extra xover with the minidsp?

I briefly touched on this with Martin the horn builder but he's not really one to offer too many ideas in case we don't like the outcome!

I do like the idea of bringing the mid horn in early.....

Thanks guys.

Sent from my SM-T800 using Tapatalk

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It's a question of balance between all facets of performance, including the room. A rugged woofer can take more punishment than a fragile diaphragm, which will sound better if it's still operating in concert with the right horn. I'm a fan of a single series large film protection capacitor along with active steep active Xover slopes, if your are pushing that Yamaha driver to the edge.

 

Fortunately, in a home environment, even at near "stupid loud" levels, we are still talking about milliwatts of power to do the job. With all precautions taken, you should be able to enjoy the superior definition and "speed" of a compression driver at the lowest frequency possible with the right "systems approach" to the problem, with a complementary hand off to a good bass/midbass horn.

Edited by ClaudeJ1

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Trouble is my mid horn won't go that low, it's a 340. Maybe I could take it lower with a sharper roll off. Don't want to cook the Yamaha driver..... no diaphragms anywhere!
Are the JA-6681 drivers a one inch throat? those look rather massive.

 

I have a pair of Yammy JA-4201 drivers that I would love to find a use for. They are an 800-20Khz driver, but I've never been able to find a freq. response plot.

 

Bruce

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Claude, Dave - do you think I should try my 340 horn right down at the lower extremity?

If the horn rolls off at 340hz should we use that as part of xover? So use the roll off at 3db from 340hz then add an extra xover with the minidsp?

I briefly touched on this with Martin the horn builder but he's not really one to offer too many ideas in case we don't like the outcome!

I do like the idea of bringing the mid horn in early.....

Thanks guys.

Sent from my SM-T800 using Tapatalk

I believe there will be a pattern control issue, if run that low.

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If the horn rolls off at 340hz should we use that as part of xover? So use the roll off at 3db from 340hz then add an extra xover with the minidsp?

 

People report they run your compression driver down to 250Hz ... or 500 with a 6dB slope .... so, yes. I would think -6dB@340 with 24dB/octave slopes would be fine.

 

 

 believe there will be a pattern control issue, if run that low.

 

Perhaps slightly, but it will surely have better directivity than the bass horn.

 

 

I do like the idea of bringing the mid horn in early.....

 
Run the midhorn down as far as it works best....   then whatever -6dB frequency and slope you have it at .... .dial in the QP so it has the complimentary response.    If you need to add a small amount of EQ ~ < 5dB to the QP to get it to play up that high, then do that.
 
Once the drivers are flat, and summing together well .... then use EQ which applies to BOTH drivers to dial in the overall response you want.
Edited by davewantsmoore

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Hi Bruce, the throat size is 35mm. Big yes, 6.75kg!

Have to be a bit careful as there aren't any replacement diaphragms available. ....

Sent from my D5833 using Tapatalk

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"... no diaphragms anywhere!"

 

Beg!  (I have six)

 

"Are the JA-6681 drivers a one inch throat? those look rather massive."

 

1.4" Altec clone.

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Hehe, thanks Dennis. I figured that out when he said 35mm.

Haave you seen resp. Charts for the ja4201?

Bruce

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"... no diaphragms anywhere!"

 

Beg!  (I have six)

 

djk, did you get the PM i sent? Wouldn't mind buying a couple from you if you're willing to part with some...

 

Thanks Dave 

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It seems that whenever there is a very good product out there, it's no longer available.

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So, are all my Quarter Pie builders happy with their bass? I'd like to hear from you and maybe see some measurements in your rooms. OK?

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I've been patiently waiting for pictures and MEASURMENTS from the Quarter Pie builders out there. Any new goodies to share???

 

Which driver you are using if not a K33, EVM15L/B, or Emience 15C then what?

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Look like they make great drivers, if a bit on the pricey side. But I guess you get what you pay for. I have TAD Beryllium drivers for my K-402's, so I get it.

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TD15M-4ohm
Fs: 34.7Hz
Qms: 5.09
Vas: 312 L
Cms: .3 mm/N
Mms: 70 g
Rms: 3 kg/S
Xmax: 6 mm(peak)
Xmech: 10 mm(peak)
Sd: 855 sqcm
Vd: 1.02L (p-p)
Qes: .35
Re: 3.2 ohm
Le: .2 mH
Z: 4 ohm
Bl: 11.81 T/m
Pe: 500W (cont.)
Qts: .33
1WSPL: 97.7 dB
2.83V: 101.7 dB

 

Fabulous driver!

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