Is it possible to cover the whole spectrum, high spl, low distortion with a 2-way?

fluid

Member
2009-01-24 2:20 pm
How do you personally feel about power response...the article the above pic is from, suggest that, some say it is an outdated concept. "Outdated" sometimes can seen as "neglected" lol so I tread lightly
I couldn't find that article to read it in context. Designing a speaker and concentrating solely on any one curve in particular is not the best approach.

Some history that prompted some of Sean Olives's work on preference. Consumer Reports used to rank speakers by measurement of the power response. Harman speakers were getting bad reviews and in typical corporate style someone needed to fix that problem. Research was done showing there was a negative correlation between the consumer reports ratings and actual blind preference tests.

The Yamaha NS10 was also designed to have a flat power response. It became popular but for all the wrong reasons.

Flattening the power response without considering the direct response works no better than flattening the on axis response and not worrying about the power response.

A paper on calculating Directivity Indices
https://www.princeton.edu/3D3A/Publications/Tylka_3D3A_DICalculation.pdf
 
"The lower the power response the less(er) the reverb" is wrong?

"The higher the power response the greater the reverberation" is correct?

"the more delay there will be in the onset of the reverb field." I never knew that
Yea, I think that it doesn't make sense unless you relate the power response to something, from an absolute value standpoint it doesn't matter much, in which case I might have meant the DI. Hence the statement(s) should be:

The higher the DI the less the reverberation relative to the direct sound.
 

camplo

Member
2019-02-25 2:27 am
Ive got Audio Architect running....Had to reinstall windows just to do it =(, daul bootin on a old mac book....between life and the living room (my speaker lab) took a hole day.


I placed a low pass 2nd order Butterworth at 21hz then cranked the band pass gain to +24db....So what happens now?
 

camplo

Member
2019-02-25 2:27 am
I want to compare and contrast. I will try doing a sweep with the xo activated.
I wonder if I'll need a high pass, so far seems like no, but I am a noob so, we'll see.

These are my thoughts after getting the crown and a low pass running. The dynamic potential of just one of my PPSLs is pretty on point. I would suggest anyone aiming for a certain Dynamic output, to do as I did, and develop towards your peak spl goals using one channel. Considering stereo, you're bass SQ will suffer if listening to material that moves lower bass left or right, while pushing the dynamic ability of the system. If an explosion came from the right....the right subwoofer will have to reach for the dynamics more so than usual...if this pushes it much closer to its xmax, you will hear it, yet the bass will be cleaner when coming from center...Keep the same SQ by aiming for max spl with one channel.
Theres a lot of loudspeaker design philosophy that revolves around, moving "points" 2x above or below another point of reference, or keeping excursion with 1/2 of xmax....simulating in 1/2 space.
I employ one to design towards quality output that reaches max spl goals, using only the L or R channel... If I had of aimed for less, I would of been disappointed, I feel. The sound is so clean when listened to, below, 100db, all the way down to 20hz, using just one PPSL.

I guess technically speaking you wouldn't want to have to use a 2nd order low pass at 21hz lol BUT since the dynamic ability of the system is sooooo high....I mean, I did design it to be able to do this....The noise floor should be higher because of what I did, right? Is that an issue on subwoofer channels? The only thing I can think to do, to expose the differences, is take measurements......I guess thats sign language for "I can't hear "the bad thing".....". Actually I can hear "too loud" lol right around the corner! with much more gain left on the eq and other gain stages inside the DSP. Don't forget...My loud is your too loud. Probably about 115db I bet. I didnt have mic hooked up at the time of demo session before dinner....since I had to reinstall windows bla bla bla, pain in the butt...I was smart enough to touch the wire...Highest I saw was 100 volts? 16 ohms...


Observation
Playing test tones through PPSL, caused a good amount of vibration in the midwoofer sitting on top of it. My thought was that, the only thing to dampen that effect would be Qes/Qms and the Box(air mass?).....and no electronic filter is going to improve or worsen this part of the game, in regards to our ability to adjust "Q" with a filter.

If that attitude is wrong, how so?
Something different happen if that woofer was connected to an amplifier?
 
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Ain't PPSL supposed to be force cancelling configuration? On positive amplitude both drivers should go towards the slot, in other words mass is moving to opposite directions. If you have mounted the drivers so that both cones are facing the slot (instead of the other driver reversed, magnet sticking out to the slot) then the drivers should be wired to same polarity.

If wiring is correct and it still vibrates, perhaps the construction is not rigid enough? Or is the sound pressure at the slot vibrating the box on top? Insert 1" steel plate between to stiffen up :D What ever it is you probably need to get the resonances of the PPSL sub above it's pass band.

edit. cone area (SD) of two 18" woofers corresponds approximately 18pcs 6" purifi woofers, which supposedly give enough bass for the current day hifi folks, alone. I suspect you'd have plenty capability even wired out of polarity :)
 
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camplo

Member
2019-02-25 2:27 am
I think its the sound pressure in the room.... a lighter flame gives the same impression....mic says about 112 at one meter. Up closer the pressure waves impose on anything it can....like the diaphragm of the woofer....my theory

Random Rap song on youtube,,,,,808 note at ~30hz lol 1642798594927.png
(make sure to use ear protection while testing dynamics =)
 
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camplo

Member
2019-02-25 2:27 am
1642801857488.png

This is from about 20" away, 2nd order 4.56% and lower at farther listening? GJ bandpass?

I've been playing bass content...most recently, tones at 20hz and 104db from 1 meter.....the amp is 10 degrees over ambient....54volts 16ohms..

with a system voiced flat to 20hz, I don't think the amp would ever get very hot.

The amp has been playing 20hz at said volume for about 10 minutes now.....The air out of the exhaust vent is about 30 over ambient, being near 100 while its 72 in hear

what are the drawbacks of using the 2nd order at 21hz?
 
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Observation
Playing test tones through PPSL, caused a good amount of vibration in the midwoofer sitting on top of it. My thought was that, the only thing to dampen that effect would be Qes/Qms and the Box(air mass?).....and no electronic filter is going to improve or worsen this part of the game, in regards to our ability to adjust "Q" with a filter.

If that attitude is wrong, how so?
Something different happen if that woofer was connected to an amplifier?

Yes. Either short out the woofer, or connect to an amp. Vibration will decrease substantially.

This is needed whenever measuring drivers that can acoustically interact,......... CD's, small cones, big cones, no matter. Short out adjacent drivers not under test.

The mid-woofer's vibration, a passive radiator, is now part of the sub's measurement...both transfer and impedance....need to get it out.
 
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The amp has been playing 20hz at said volume for about 10 minutes now.....The air out of the exhaust vent is about 30 over ambient, being near 100 while its 72 in hear

what are the drawbacks of using the 2nd order at 21hz?

You are getting a 30 degree temp rise coming out of your vent?? Your cones are facing the slot?? This is sealed so no venting to cool the drivers?? Have to wonder what's going on inside the box. Sounds like you have built up so much heat that it's radiating through the cones and frame into the slot. Might want to shut down and carefully lay a finger close to on the frames.

If this is correct you could consider this as a drawback.

Rob :)
 
Not exactly correct.

The DI(theta) is the power response normalized by the "theta" response. In other words, the DI is dependent on what is chosen as the listening axis.

The listening axis response is what the direct field response will be, and the DI indicates what the relationship will be between the direct sound and the reverberant sound. If the DI is flat, then the reverberant field will have the same timbre as the direct sound. If it rises, then the direct sound will be "bright". This holds above say 300-400 Hz where the ears integration time is such that it cannot distinguish between the direct sound and the reverberant sound. But always remember that this is dependent on what one chooses as the listening axis. I choose and design my systems for a flat DI along about 20-25 degrees and toe-in the speakers. Thus, my direct field has the same timbre as the direct sound.



The software on my website shows many speakers listening axis response and the DI as the angle is changed. It also shows the power response. So there are many examples available.

Your "theory" is exactly the reverse - the higher the power response the greater the reverberation will be. The higher the DI, the lessor the reverb field will be and, which is very important, the more delay there will be in the onset of the reverb field.

Hello Earl

Thanks for the clarification.

Rob :)
 

camplo

Member
2019-02-25 2:27 am
You are getting a 30 degree temp rise coming out of your vent?? Your cones are facing the slot?? This is sealed so no venting to cool the drivers?? Have to wonder what's going on inside the box. Sounds like you have built up so much heat that it's radiating through the cones and frame into the slot. Might want to shut down and carefully lay a finger close to on the frames.

If this is correct you could consider this as a drawback.

Rob :)
You are funny! The exhaust vent of the amp!
The heatsink/phase plug, barely warmed up at that time.
 

camplo

Member
2019-02-25 2:27 am
You're talking about a low pass, right? If so, it's nonsense to be blunt.
Maybe simulations make it look like something that helps, but if so, it just means bad design is being used to correct bad design.

The only low pass that should be in play, is the low pass used for x-over.
You kinda jumped into the middle of something Mark100... I'm talking, about a low pass...
You’re planning to put a second order low pass filter on the sub at 21 Hz?!
Whats the issue?
 
You kinda jumped into the middle of something Mark100... I'm talking, about a low pass...

Whats the issue?

Well, if a 21 Hz 2nd order low pass filter flattens out the subs's raw acoustic response, then the sub has to have a very unusual rising raw response, that just keeps on rising as frequency increases.
And that rising raw acoustic response is basically worthless to any kind of sub design desiring relative flat peak SPL response (or even more worthless to sub designs that often desire increasing SPL response as frequency decreases.)

IF, the 21 Hz low pass is truly helping, seems to me the acoustic design has to be whacked..
 
Its a result of the rising frequency response of the 18H+ actually... oh yeah! and the slot on top of that compounds it

The best advice I've gotten about voicing is; you do what you have to do to get the frequency response linear.
Yeah, brings up memories of all the discussion about whether the 18H+ is a good low-sub driver, or mid-sub driver.
Seems like mid-sub it is and yes, the slot compounds it.

I guess the best advice I've gotten is try to get the acoustic design right, such that it needs as little processing as possible to achieve linear response.