Extension, SPL, perceived sound and possibly more subjects?

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JensToft91
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Extension, SPL, perceived sound and possibly more subjects?

#1 Post by JensToft91 »

Hi all.

So, some of you has probably seen my posts about my slim TT vs. SVS PC12-NSD, and my questions about extension.

I want to understand, and possibly scientifically determine the difference between 2 subwoofers. I have seen YouTube lectures about perception of sound, that Bill linked to on another forum, and I know that it really affects me.

I'm so "anxious" about finding out whether the slim THT LP will be satisfactory to me, or my PC12-NSD or Table Tuba actually does things just aswell at lower listing volumes, that I keep searching the internet for "answers".
In reality, I might not know what I'm looking for?
And therefore, I don't actually know what questions to ask.

I know I'm not making any sense, but I'm hoping that someone might me able to piece it together, if I ask a series of questions.

- if I had two subwoofers, a horn and a vented, and I would apply EQ to them, so they measure the same - would these two subwoofers then sound the same?
- is extension below, let's say 26 Hz important, if I can't really hear it anyway? I have an UMIK-1, and can measure the same SPL at 30 Hz. and 26 Hz. 30 Hz is really loud, and 26 Hz is barely audible to me. I'm aware of the human, ehm, listening curve - so I know why. I just don't understand the need for sub 26 Hz if it's not audible. It shakes things - sure - but does it really add a perception of "depth" to movies/music?
- My SVS PC12-NSD will play a 18-20 Hz sine wave loud enough to shake things - and I kinda want this in my slim THT build. I just can't figure out, if it's able to do so - but then again, is it 18 Hz in movies, that shakes the couch? 20? 25? As far as I've read, there not really alot of information in these registers anyway.

Enough babbeling.
A real question now: if I were to compare two subs, and I wanted to eliminate all personal perception, and purely wanted a scientific result. Could I do this with REW and an UMIK-1? How would you do it?

Sorry for this mess of a post. But I think it clearly shows a frustration. Maybe I already know the answers, and is just complicating things. A big thank you to anyone who takes the time to answer.

JensToft91
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Re: Extension, SPL, perceived sound and possibly more subjects?

#2 Post by JensToft91 »

Attached is an outdoor compression measurement of the pc12 boxed brother, the pb12. They are identical in output.

And total harmonic distortion.

How would you the think the slim THT LP, will compete against this?
Attachments
Screenshot_20211230-130044_Chrome.jpg
image.jpeg

JensToft91
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Re: Extension, SPL, perceived sound and possibly more subjects?

#3 Post by JensToft91 »

I know I'm in the process of answering my own question.
But: say I listen to movies at -20 dB, with dynamic EQ that adds approx 10 dB to the bass levels. And I run the sub 8 DB hot.
That's 115 - 20 + 10 + 8 = 113 dB.
If the SVS is only capable of 103 dB + cornor loading (9db) = 112 dB, I've actually already maxed it out? Theoretically, at the max possible output. - this is where the 10%THD sets in.
This is possibly why I think my TT sounds better, even though it has a few Hz less extension?

And, from the looks of it, it's not actually a true 18 Hz extended sub. That's more like a 6 dB drop from 25 hz, not even including the compression at the highest levels.

So for me, it looks like the THT will reach 25 Hz at nealy all levels with ease, and then decline from there. Not adding THD into the mix - and there for sound alot cleaner.
I guess true 25 Hz extension is better than strained 18 Hz extension.

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Bill Fitzmaurice
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Re: Extension, SPL, perceived sound and possibly more subjects?

#4 Post by Bill Fitzmaurice »

Where THD and power compression are concerned the THT will beat any direct radiator of comparable output. Ever read this page? https://billfitzmaurice.info/THT.html

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Re: Extension, SPL, perceived sound and possibly more subjects?

#5 Post by JensToft91 »

You can be direct, Bill ;) Of course I've read it. Countless times.
You mentioned in my other post, that if I built the slim version, it might not do what I want.

But if it beats the PC12's low-end I've posted measurements of, it's all good.

Still curious about all the other questions, if anyone can link to some information about this.

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Re: Extension, SPL, perceived sound and possibly more subjects?

#6 Post by Bill Fitzmaurice »

This may help.
http://www.readresearch.co.uk/loudspeak ... icle_1.pdf
http://www.readresearch.co.uk/loudspeak ... icle_2.pdf

These articles are in part responsible for my first foray into designing and building horns in 1970, and being familiar with them put me in a position to be offered a job by Paul Klipsch when I met him in 1973. I turned it down, not having any desire to live in Arkansas.

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Re: Extension, SPL, perceived sound and possibly more subjects?

#7 Post by JensToft91 »

Thank you very much.
I'll read these before I ask any further questions.

That's cool! Have you been designing horns for 50 years?

I've admittedly fallen prey to some of the negative reviews around, making me doubt some designs. That was until I realised that some of these people look at the frequency response graph as a vented design. They'll take the highest sensitivity, go 3 dB down, and say "do you really think this is a good design? The cut-off is at 90 dB. -16 dB at 40 Hz. -12 dB at 35 Hz." Then they post their own measured graph that happen to match your posted graph. Not realising that the sensitivity of the area that actually matters, is higher than their other cabinets.

I'm writing this because of frustration (that talent can be overshadowed by.. ehm.. stupidity, and because I have a feeling that my questions are understood as "I don't trust the design, is it really better than this subwoofer?".
They're really not. It is genuine curiousity, because I can't figure out, if the slim version of the THT has 20 Hz extension. As I read the sensitivity graph, the slim version will be quite alot less sensitive at 20 hz than it is at 25hz. So I'm asking about it, because I don't plan on using a 200 w amplifier to raise the gain this much in that area.

Hope you read all these things positive. It's meant that way.

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Seth
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Re: Extension, SPL, perceived sound and possibly more subjects?

#8 Post by Seth »

Jens, I'm sure a bunch of the guys here will agree that your mind works in a way I can relate to quite well. We think in much the same way and I'm pretty sure I understand your curiosity and quandary. I'm no audio guru, so I may not have all the answers. But, I'm on board to figure it out with you :thumbsup:

JensToft91 wrote: Thu Dec 30, 2021 6:34 am - if I had two subwoofers, a horn and a vented, and I would apply EQ to them, so they measure the same - would these two subwoofers then sound the same?
I've had the very same curiosity. The unverified conclusion I've come to is; provided they're both capable of reproducing the desired frequency range, they should sound the same... up to the point that one or both exhibit audible distortion. But again, that's just the unverified conclusion I've come to on my own. I'd love to get some validation or outright disqualification on that too.
- is extension below, let's say 26 Hz important, if I can't really hear it anyway? ... I just don't understand the need for sub 26 Hz if it's not audible. It shakes things - sure - but does it really add a perception of "depth" to movies/music?
This one is completely up to you. If you're trying to distinguish whether numbers on a chart are important or not, I'd recommend playing actual content (not just sine waves) with those frequencies then highpass those frequencies out and see if you're disappointed or not. Personally, I find value in the visceral experience. But, the vast majority of people wouldn't miss what they didn't know was there to begin with. So, whether it's important or not is really a personal choice for you to make on your own.
...is it 18 Hz in movies, that shakes the couch? 20? 25?
Any of the subwoofer band of frequencies reproduced at sufficient volume are visceral. Not to sidetrack the conversation, but if you want the couch to shake, just add some tactile transducers.
JensToft91 wrote: Thu Dec 30, 2021 6:34 am ...If I were to compare two subs, and I wanted to eliminate all personal perception, and purely wanted a scientific result. Could I do this with REW and an UMIK-1? How would you do it?..
Disclaimer: I have REW on my computer, but have never used it.
That said, I'm quite certain it will do what you want it to do. Place and affix the measurement mic in your listening position, disable any signal processing/EQ, and run a sweep. Maintaining the microphone position as stationary as possible, swap subs (position too), and run the sweep again. I'm pretty sure it will automatically overlay the two results. HOWEVER, given the two are driven by different amplifiers at an unknown voltage (unless you measure and set them identically), the information gained would be more about the shape of the response curves versus being able to compare the sensitivity too. Seems you could make adjustments to the level of the 2nd speaker until the output matched at a specific frequency, then compare the differences from there. But, to do it somewhat right, you'd want to measure and set the amplifiers output voltage the same for both tests to get the most accurate data to compare.
A big thank you to anyone who takes the time to answer.
You're welcome. :thumbsup:
Last edited by Seth on Thu Dec 30, 2021 6:13 pm, edited 1 time in total.
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Re: Extension, SPL, perceived sound and possibly more subjects?

#9 Post by Bruce Weldy »

Bill Fitzmaurice wrote: Thu Dec 30, 2021 12:07 pm not having any desire to live in Arkansas.
Gee, I don't know ..... Arkansas isn't so bad. After all, that's where the toothbrush was invented..




Of course, had it been invented anywhere else, it would have been called a teethbrush.

6 - T39 3012LF
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Re: Extension, SPL, perceived sound and possibly more subjects?

#10 Post by himhimself »

Bruce Weldy wrote: Thu Dec 30, 2021 4:14 pm
Bill Fitzmaurice wrote: Thu Dec 30, 2021 12:07 pm not having any desire to live in Arkansas.
Gee, I don't know ..... Arkansas isn't so bad. After all, that's where the toothbrush was invented..




Of course, had it been invented anywhere else, it would have been called a teethbrush.
OMG, i needed that today. :lol: Thanks Bruce!
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Re: Extension, SPL, perceived sound and possibly more subjects?

#11 Post by Bill Fitzmaurice »

So do you know why they had to put in artificial turf at Razorback Stadium? To keep the cheerleaders from grazing at halftime.

JensToft91
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Re: Extension, SPL, perceived sound and possibly more subjects?

#12 Post by JensToft91 »

Bill Fitzmaurice wrote: Thu Dec 30, 2021 12:07 pm This may help.
http://www.readresearch.co.uk/loudspeak ... icle_1.pdf
http://www.readresearch.co.uk/loudspeak ... icle_2.pdf

These articles are in part responsible for my first foray into designing and building horns in 1970, and being familiar with them put me in a position to be offered a job by Paul Klipsch when I met him in 1973. I turned it down, not having any desire to live in Arkansas.
I am extremely impressed. What a good read. If I understand this paper correctly, it explains just about all the questions I have posted on this forum.

It makes so much sense, why I feel the way I do about t
The TT vs. The PC12. The PC12 might add som tactile frequencies that may be desirable, but it also adds so much audible distortion that muddies the sound. It describes exactly what I felt.

It might also explain, why people have multiple sealed 18's to have this sub 20 hz extension - and why it might not be doing what they really want. The sound can't be heard, it's purely tactile. They claim that they definitely hear the difference - and sure they can. 18" driven at extreme excursion at 10-20 Hz will by my understanding of the paper create a multitude of other tones at the audible range of bass. An explosion consists of low-end LFE effects AND 30 -100 Hz bass - the excursion of 10-20 Hz tones will dirstort the other signals to quite some extend. And that is audible.
Which is probably explain why they keep building more and more. It will be cleaner and cleaner as the efficiency goes up.

The paper also explains why you can claim that the THT beats any direct radiator of comparable output. It seems "uptight", when I don't know how you can claim it. But it makes SO much sense when I do know why you can claim it.

I'm pretty certain now, that I will prefer horned 25 Hz bass Vs 20 Hz ported bass. Or.. I know I will.

Thank you so, so much for clearing this up for me. I've probably been obsessed with this for 8 years. In bass, midrange and tweeter level aswell. It makes so much sense.

You SLA also makes sense now. Your way of getting rid of distortion is high efficiency. Horned speakers all the way through are too hard to sell. Linearray not so much. So it's a compromise.

I've been of the understanding that it was in the crossover all the magic were. It's probably less distortion (high efficiency) and voicing of the speaker that matters most.

Please feel free to correct me, if I have understood some of this wrong.

Your SLA is interesting for me now. I'm really curious about how you handle the crossover in these, as I've understood you can use different drivers in it. But maybe it can be more general, because of what I've written above?

I could go on forever. I'll stop for now.

And thank you Seth! So nice to hear, that I'm not alone in this "insanity". 😄

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Re: Extension, SPL, perceived sound and possibly more subjects?

#13 Post by ACUA »

My two cents:

I am a lot like you, I want all the answers and I want to understand every scientific detail. I have and still do spend a lot of time studying and researching and I still feel clueless. One important element of horn loaded loud speakers to consider is driver excursion and the distortion introduced as a result of the time delay that occurs when the cone has to move a great deal to produce the desired pressure. Even if a front loaded base reflex sub is able to play loud enough it has to move a great deal and this introduces distortion when it struggles to transition from one signal to the next. The inertia created is hard to stop once the cone is flopping at 2”peak to peak. With a horn the output to cone excursion is much less this increases fidelity and integrity.

I have personally noticed with all of my front loaded subs compared to horn loaded there is a better transition between the driver and the medium of air when properly horn loaded. This is noticeable to me and I do not know how to identify this with a spectrum analysis. The horns always sound smoother and the sounds are, how do you say, effortless! I can shake the decor on the shelves of my house using a single 8” driver with a 150watt amp using a table tuba horn enclosure. It only cost me $100 to build the table tuba that I built and the amp is cheap because I do not need 500-1000w to drive it.

If you are this curious, start saving up your money, build one of these horns. I believe you will be happy with the results. I say build the largest one you can get away with, it’s always nice to have headroom.
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Re: Extension, SPL, perceived sound and possibly more subjects?

#14 Post by Bill Fitzmaurice »

ACUA wrote: Sat Jan 01, 2022 5:53 pm I have personally noticed with all of my front loaded subs compared to horn loaded there is a better transition between the driver and the medium of air when properly horn loaded.
It's because a horn is an impedance transformer. Moving coil loudspeakers have an inherent flaw, in that they're high impedance devices operating into a low impedance load, that load being air. 2 ohms doesn't sound like it's a high impedance, but it's huge compared to the impedance of air. This is what causes direct radiator speaker efficiency to be very low, around 2% on average. A horn provides a driver with a higher impedance load, so the speaker works with far greater efficiency. The THT runs with an average efficiency of 25%. That efficiency is at the heart of why horns are better.

Anticipating the next question yes, direct radiators would work better if they had much lower impedance values. The reason why they don't is that they would have too low an impedance for amplifiers to work into.

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Re: Extension, SPL, perceived sound and possibly more subjects?

#15 Post by ACUA »

I know how this sounds but the horn seems to change the quality of sound wave created, like beyond just the impedance match or improvement/ efficiency gains, I hear and feel a more solid sound somehow with horns. If I setup and use a high power direct radiator sub, I can get things to rattle all over my house and somehow observe a weak bass sound, then when I deploy a proper horn sub the sound will be rich and full and powerful long before things start to rattle around in the space. Certainly this has to with the distortion but there is an audible benefit to a proper horn loaded sub over a direct radiating unit. Now if you use a servo sub or some tech like that it can sound amazing but that is expensive! I built a table tuba for $120 total that only needs a 100-200w amp to shake my house. I don’t know another way to do it for that cost. . .
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