Question: Optimizing Sub Driver Size for Transient Response?

Transients: how much dynamic range is needed for a sub to fully reproduce bass transients in typical movies and recordings? And how can we determine how big is big enough for a subwoofer driver?

Specific to my application, I'm choosing between 10" and 12" drivers. If the sub is playing content at an average SPL of 80-90 dB, where is the point of diminishing returns in terms of dynamic range. Should the sub be capable of 10dB more? 20dB?

I started with 10" drivers, because on paper the 10" met all of my requirements. I get response down to 20hz in a manageable cabinet volume, and the SPL capability exceeds the SPL I expect to listen at.

But now I started thinking about transients, and I am second-guessing myself. My 10" subs are simulated to have a max SPL of 105dB each. But if I switched to 12" subs, that number would go up to 110dB.

One argument is that the 10" meets the requirments, and the cone has less mass...so it should be more controlled, detailed (i.e. good transients?), distort less, extends lower than the 12" in a given cabinet volume, etc...

The other is that the 12" has more dynamic range, pushes the same amount of air with half the excursion...but has more mass, maybe more distortion, etc...

My gut says it is a toss-up? I'd like to know if there is a compelling argument for the 12" drivers. I already have the 10" drivers, and I'm foolish enough to buy 12" drivers if you can convince me. But make your pitch pertinent to the points mented above. Thanks!
 
how much dynamic range is needed for a sub to fully reproduce bass transients in typical movies and recordings?
If you mean crest factor (peak / avg), then something like 20-23dB. Dynamic range is the ratio of the loudest sound to the softest, often approaching 90dB or more. Usually, a subwoofer is expected to be able to match (at least) the same SPL as that of all the main channels driven together.

... the 10" met all of my requirements. ... I'd like to know if there is a compelling argument for the 12" drivers.
Yes, but at what excursion and power ? Is the power reasonable and within the capabilities of a typical amplifier ? Remember that you may not have considered the effects of bass redirection from other channels, equalisation, room correction etc.
 
If "crest factor" is the term, I'll go with it. I kind of wanted to call it "head room", but dynamic range seemed more correct to me...

Your 20-23dB suggestion may be the right answer, but I'd like to understand why that is the answer.

And does that mean +20dB for each sub in a multiple subwoofer system? Or is that the rule of thumb for a single subwoofer?

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I didn't give all the specs for my project because I want a narrow focus. Trying to explain everything would confuse the subject and make everybody forget the original question.

But you are welcome to check out what I'm working on:
https://www.diyaudio.com/community/...on-of-integrating-multiple-subwoofers.401343/
 
Transients: how much dynamic range is needed for a sub to fully reproduce bass transients in typical movies and recordings? And how can we determine how big is big enough for a subwoofer driver?
Some would argue there is no such thing as too much sub.
Specific to my application, I'm choosing between 10" and 12" drivers. If the sub is playing content at an average SPL of 80-90 dB, where is the point of diminishing returns in terms of dynamic range. Should the sub be capable of 10dB more? 20dB?
Well if you look at the Fletcher-Munson curve 20hz needs to be 20dB louder than midrange frequencies just to sound balanced, but room gain will help aleviate some of that. But a sub in particular should be capable of producing all it's content confortably within it's linear range, if you have to push the driver to the threshold of xlim to cover the transients they won't sound particularly good.
One argument is that the 10" meets the requirments, and the cone has less mass...so it should be more controlled, detailed (i.e. good transients?), distort less, extends lower than the 12" in a given cabinet volume, etc...
Driver size does not matter here transient performance is more about motor strength and power handling, any decent quality driver will have sufficient motor strength to handle it's cone.. if it doesn't it's a very poor design. But larger drivers better couple with air and are therefore more efficient at converting electrical energy into acoustic energy, and this is particularly apparent with transients. 50w into a 10" driver may not produce a transient you can feel 2m away but into an 18" driver you will feel something. ;)
 
Conanski, unfortunately my speakers are only 16" wide, so the 18" driver may not fit very well. But it's worth a shot, right?

I personally have some reservations about the Fletcher-Munson curve concept. With my speakers set up to be close to flat from 20hz to 20khz, and with average SPL of say 70-75dB, I feel I can hear everything equally well. It makes more sense to me at 90+ dB, but I will spend most of my time below 90 dB average. Of course the transients will louder than the average...

Part of the reason I'm going down this rabbit hole is because I once owned a Genelec 7060B subwoofer. It was technically excellent and played a tone pretty loud, but it just didn't have any impact.

With my design, I knew from the beginning that the 10" subs are the weakest link in the system.

The 10" subs are Dayton Audio RSS265hf-4s. They model at ~105dB from 20hz and up in my enclosure.

The other 2 subs are Eminence Lab 12s in sealed enclosures, and they model at 112dB @50hz.

If I changed to a 12" sub, it would probably be the Dayton RSS315hf-4 (12"), which would produce 110dB from 21hz.

I also like the way the 10" looks, although it's on the back so nobody will ever see it..... Here is the 10" sub and port outlet:

(It'll have a bezel around it eventually.....)
20230716_125310_resized_1.jpg
 

GM

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Joined 2003
Transients' dynamic range is bandwidth (BW) and since the lower the fundamental the wider its BW, then in the low end of the LFE BW we're 'talking' out to > 20 kHz, so ideally the better, more extended/'fuller' the (super) tweeter the better the LFE's transient response, though of course the recording is the actual limit.

Sound power's dynamic range is the difference between the highest/lowest passages and Crest Factor is the instantaneous difference between RMS and Peak Levels.

RE the LFE's dynamic headroom: https://www.diyaudio.com/community/threads/sub-box-with-alpine-drivers.401361/post-7408190 & https://www.diyaudio.com/community/threads/sub-box-with-alpine-drivers.401361/post-7412069

Re choosing a sub driver, it's all about having a massive/rigid diaphragm and displacement (Sd*Xmax) with the XO point ideally setting its effective motor strength; i.e. referenced to a 20-80 Hz BW, then its upper mass corner (Fhm) where T/S theory peters out = 2*20/80 = 0.5 Qts' with each successive driver BW ideally done the same to in theory yield a perfect transient response using 1st order XOs, so each driver ideally needs to be flat for (4) octaves above the XO point, ergo the sub ideally needs to be flat to 80*2^4 = 1280 Hz or rotating 360 deg (1 Hz offset) 4th order = 160 Hz.

Unfortunately, 0.5 Qts' = OB/IB or huge vented boxes, so some form of TL/horn and/or corner loading is normally required, though nowadays extremely small Vas drivers are a viable option + DSP allows EQing otherwise acoustically tiny cabs at the expense of reduced efficiency.

All that said, the pioneers considered a max flat's 0.707 Qts' 'critical' damping' as sufficient for excellent transient response reproduction, but this included the tube amp's output impedance, so driver Qts was somewhat lower hence the main reason why there's been so much confusion WRT choosing Qts driver specs on DIY audio forums.

(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
 
I realize that your limits are set, but I just have to say that in my experience with bass, there are different trade offs concerning what you got and what you want.. I agree with you generally about a 10" driver being tight in the bass, and yes, I like that. An exception for that was a pair of bass horns using 15" drivers that seemed to do about everything, except hide in the room. I now own a 12" with an amp using an accelerometer design that gets more right in both ways.
Does the sub need as much headroom as you think? It would nice to be able to just dial in the right amount according to your preferential needs.
 
Ixnay- I thought I was the one asking how much headroom is needed! I'm hoping to get a second opinion to help settle my mind.

On one hand, I know that modern recordings don't have much dynamic range. But on the other hand, my gut says that the speaker's capability should exceed the recording. But by how much? And will I really notice if I have a little bass compression between 20-40hz?
 
Part of the reason I'm going down this rabbit hole is because I once owned a Genelec 7060B subwoofer. It was technically excellent and played a tone pretty loud, but it just didn't have any impact.
There are multiple potential reasons why that may have been the case but one of the big ones is that a single low power 10" just doesn't displace enough air. It also depends on what type of impact you are referring to... movie explosion impact or music kickdrum inpact. The former is mostly subsonics and requires massive quantities of air displacement while kick drum impact is actually in the 80-120hz region which is totally outside the traditional HT sub range, but doing it well at moderate SPLs still requires larger drivers.
My current HT consists of a single 12" powered sub and Dayton BR1s, it sounds great but it doesn't produce any visceral impact which isn't surprising to me, the sub is low powered by todays standards(only 120w) and the BR1's don't have enough low/mid air displacement. How do I know that? My very first audio system was built around large 3-way monkey coffins with 15" semi pro drivers, even with only 65w on tap from a lovely Sansui AU-D5 Integrated these things produced great dynamics, they didn't go particularly low but kick drum sound and feel was excellent.
I now own a pro sound and lighting business and have an inventory of modern powered PA speakers... 18" subs, 12" and 15" 2-way mains plus some even larger passive boxes, and all of these are 1kw+. Just one of these subs in my HT room can produce impact and rumble that knocks pictures off the walls.. both in the rec room and upstairs in the living room. opps.:cool:
I mention this just to say that my audio experience has demonstrated that air displacement is key to delivering the impact of music, it can be done with smaller drivers and loads of power but that doesn't sound/feel the same as doing it with larger drivers, they just have a more effortless feel about them.

All of this is a bit devils advocate on my part because you may not want to go to these extremes so just food for thought, but I think you may start to get into the range of capability to produce impact you can feel with a pair of 12's. I think you will need to power them for all they are worth, it may not start there but there is always going to be that "what if" thought in the back of your head, an itch you have to scratch, but that is part of the fun.
 
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Your 20-23dB suggestion may be the right answer, but I'd like to understand why that is the answer.

And does that mean +20dB for each sub in a multiple subwoofer system? Or is that the rule of thumb for a single subwoofer?

But you are welcome to check out what I'm working on:
https://www.diyaudio.com/community/...on-of-integrating-multiple-subwoofers.401343/
For multiple subs, the total SPL from all the subs are the thing to be considered. Below is a nice reference manual for people who would like to understand the finer details (hows and whys) of movie sound reproduction.
 

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Conanski- For the record, the Genelec sub used an 8" driver, and I think 120 watt amp. So it's a little guy, although you wouldn't know it from the price!

If you didn't see the link I added before, you might be interested that my speakers are 80% pro audio...B&C coaxials, Lab 12 woofers...only the rear 10" subwoofers are hifi. I spent time looking at every 15" and 18" woofer and subwoofer I could get specs for, looking for a combination that could fit in a living room friendly cabinet. (The Lab 12 saved the build!) The front facing drivers are all 12". I used a 10" rear sub because I was trying to copy what Genelec did in the W371A.

https://www.diyaudio.com/community/...on-of-integrating-multiple-subwoofers.401343/
 
On one hand, I know that modern recordings don't have much dynamic range. But on the other hand, my gut says that the speaker's capability should exceed the recording. But by how much? And will I really notice if I have a little bass compression between 20-40hz?
If you follow my HT musings to calculate based on your reference, then you're 'golden' for all but certain special effects and some pipe organ recordings/videos/movies and no since it's in the upper bass - mids being reproduced by other drivers means there's none to hear unless of course your 'sub' is a wide range one covering the BW above ~300 Hz where your acute hearing starts increasing.
 
I’m trying to understand what the need or goal is.

The title asks about transient response, which is directly tied to frequency response. However, it looks like the goal is actually output related.

So what really is the goal or need?
One argument is that the 10" meets the requirments, and the cone has less mass...so it should be more controlled, detailed (i.e. good transients?), distort less, extends lower than the 12" in a given cabinet volume, etc...

The other is that the 12" has more dynamic range, pushes the same amount of air with half the excursion...but has more mass, maybe more distortion, etc...
 
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That is a neat design for sure, but do you have both front and rear subs covering the same part of the spectrum? And how low do you run the coax 12"

This driver arrangement has the potential for good spectral response but right away I would suspect it has a negative impact on impulse response... so probably not a coincidence that that is what you are here asking about. Also interesting that you mentioned cardiod sub arrays, the one big downside with them is that they smear impulse resonse.
 
That is a neat design for sure, but do you have both front and rear subs covering the same part of the spectrum? And how low do you run the coax 12"

This driver arrangement has the potential for good spectral response but right away I would suspect it has a negative impact on impulse response... so probably not a coincidence that that is what you are here asking about. Also interesting that you mentioned cardiod sub arrays, the one big downside with them is that they smear impulse resonse.
Nothing is set in stone right now. The working theory is that this is multiple subwoofers, so all for subwoofers are playing a summed signal from 20-100hz. I'm happy to discuss methods and share measurements, but preferrably under the other thread?
 
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Dolby's recommended listening level for home theater is approx 75 dB with 20 dB headroom. The requirement for the LFE/subwoofer is 10 dB higher. That means the subwoofer should be able to play 105 dB in your listening position down to at least 25 Hz. A single 10" simply can't do that.....
 
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StigErik- that seems to match up with what newvirus2008 said. That's good to independently verify. I wasn't sure where the number came from.

But of course I'm talking about 2- 10" + 2- 12" subs. I suppose the next thing to do is put in some ear plugs and run some sweeps....try to figure out if my subs can hit 105dB at the listening position. I assume 105dB impulse is acceptable?