IB and EBS time domain performance

[Ayreonaut]

Bag End wrote:

Almost all specifications for subwoofer systems are fixated on the frequency response domain. However, the impression of power and quality is equally related to the time domain performance of a system. Because of the long wavelengths of low frequencies, this is particularly true with subwoofers. Likewise, the maximum SPL is not a very reliable way to judge the impact of a subwoofer. A poor time domain performer will not have the same impact or natural sound as a time correct ... system.

In my experience this is absolutely true. At a certain other forum to remain unnamed there are pages and pages of "heated discussion" about monstrous DIY subs, but this critical issue is largely ignored.

Has anyone here seen the measured impulse response (or any other time domain measurements) for an Infinate Baffle sub or a DIY large Extended Bass Shelf sub?

[Exocer]

Personally I haven't.

In the larger EBS systems, the driver provides most of the output in the most "musical" frequency ranges down to lower frequencies than typical vented designs. Does this mean impulse response charts will look more like that of sealed subs? I would assume they'll be close but not identical. By the time port SPL contributes to output you're almost in the inaudible frequency ranges where impulse response probably isn't even important (again this is my opinion of course).

IB would theoretically be just as tight if not tighter than most normal sealed allignments due to the huge Vb, thus creating a low as heck Qtc. I wonder if this is the case since the air-spring behind the drivers is pretty much eliminated in IB, what effect does that have on impulse response?

[Darren]

From my reading on IB and discussions with several people on the topic, an IB subwoofer tends to be very quick. From my listening experience the IB integrates with my mains much better, you really don't know there is a separate subwoofer element in the mix. With my old box sub you knew the bass was coming from something other than the speakers. It integrated well but you could still tell the bass was a separate component. Not so with the IB. I'd attribute some of that to what I believe you are describing as time/delay.

Am I interpreting "time domain" appropriately?

[Ayreonaut]

Acoustic suspension designs use the air mass within the cabinet as a "spring" to help return the relatively low mass speaker to the rest position. The size of the box is important.

Rhythmik at AVS wrote:

To make the long story short, my observation is the vented box is not a agile as the sealed box and that 4 cu ft sealed box is not as agile as the 2 cu ft sealed box (but the 1 cu ft sealed box sound I tried sounded awful), all using the same driver and all conform to +/-1db deviation. ... My speculation is the the larger sealed box does not have enough back pressure to linearize the compliance, so the distortion is somewhat more audible. In the past, the advantage of vented box is to use shorter coil to get lighter moving mass and low Qts value. That has helped the sound quality of vented box a lot. But if you tune it low, it will require a longer coil and therefore heavier moving mass. That low mass advantage is gone. So I am really wondering how these factors play in the real world.

Here's the Impulse Response for a sub with a sealed enclosure.




Here's the Impulse Response for a sub with a large, ported box.


Clearly, there's a lot of slop there. But that's not the end of it. The Spectral Decay plots reveal that the ringing can attenuate much quicker in the mid bass and linger in the low bass.

Spectral Decay for a ported design where the ringing lingers around 20 Hz.


There may be advantages to using huge boxes or tubes, or IB, but I've seen nothing to prove that this ringing is eliminated.

So here are three questions about IB and EBS:

1. Is IB or EBS system well damped in the mid bass, and not so well at very low bass or "system resonance?"

2. If the ringing is limited to the very low bass, will there still be slop generated from signals in the musical range?

3. Where is the measured data on this?

[Darren]

I'd measure my IB for the "ring" and "timing" if I knew how and had good measurement equipment but unfortunately I don't

[SteveCallas]

The larger the enclosure, the lower a tune one can get away with and the lower the Q will be, meaning a more damped system, or more accurate bass. By using a really low tune, transient response issues are largely kept in the lowest of frequencies. Then consider that such a low tune allows one to get away without using a high pass filter, which negatively affects transient response. Finally, consider that almost every LLT has mated extremely well with typical room gain, resulting in very flat in room FRs to very low frequencies, pushing the transient response issues into even lower frequencies again, and I think you will find time domain issues to be very well behaved, definitely much more so than more traditional ported subs.

Even in just comparing the Monolith to the Plus/2, you'll see the Monolith has better transient response due to no highpass, more volume per driver, and a naturally lower tune.

An IB should have the greatest transient response of all, as it is the most highly damped. A small sealed box typically has a higher Q, and is actually "sloppier". It needs a LT to flatten out the response and optimize performance.

[SteveCallas]

1. Is IB or EBS system well damped in the mid bass, and not so well at very low bass or "system resonance?"

IB is well damped at all frequencies, LLT is well damped until subsonic frequencies.

2. If the ringing is limited to the very low bass, will there still be slop generated from signals in the musical range?

It depends on how low you tune, how high the Q is, and how flat the resulting FR is. Here is a SVS 20-39 in 20hz tune:



Now here it is in 12hz tune:



As you can see, much less spillover into audible frequencies. Now if they designed that sub to be tuned to 12hz from the get go, meaning a larger enclosure and no high pass, that chart would be even cleaner. That's what the LLT does.

3. Where is the measured data on this?

Well I just showed you some, and you posted some yourself comparing the Monolith to the Plus/2. Unfortunately I don't have measuring equipment of that caliber nor the know how to take those kinds of measurements, otherwise I would. But it's all a simple logical progression - we can extrapolate based on the subs that are measured.

[Chrisbee]

I can offer a subjective opinion based on a couple of years of listening to a relatively large reflex enclosure (16-46 cylinder SVS) and my 4 x 15" IB over several months.

No matter how short a sound is reproduced the IB has the unique ability to tell you everything about the sound envelope. It does this completely effortlessly. Leading edge, form of sustain, weight, timbre and decay are all clearly heard in the briefest of sounds.

The cylinder doesn't even come close and sounds very coloured, soft, muffled, ponderous, distant and dull in comparison. However the cylinder does offer effortless infrasonics for film watching. As long as the sounds are not too short it still adds enormously to the enjoyment of films.

For gunfights like "Open Range" you really want the IB to capture the shocking violence and sharp impact of gunfire at all accurately. On "Private Ryan" you want the very low distortion and remarkable transient response of the IB to capture the tank movements and explosions properly. The IB gives you no warning of something coming! Its leading edge is so steep the mind has no time to adjust to what is suddenly there in full force.

The slower cylinder is better at rolling massive boulders about. You know what's coming and can prepare yourself for the coming imact. If you want tactile menace in the air on LOTR then the slower but effortless infrasonics of the cylinder redeem it relative to the IB.

I would humbly suggest that the IB's transient and distortion superioirity would be clearly displayed on test equipment.

[Darren]

Yeah, what Chrisbee said... he has a way with words

[SteveCallas]

The cylinder doesn't even come close and sounds very coloured, soft, muffled, ponderous, distant and dull in comparison.

While I agree 100% the IB will beat the SVS in all the things you mentioned, as well as just about every other measure of performance, you can't base the results on account of the alignments, as you're using four 15" drivers with beefy class AB amplification on one hand, and a single 12" driver with a BASH amp on the other hand

[Darren]

SteveCallas wrote:

While I agree 100% the IB will beat the SVS in all the things you mentioned, as well as just about every other measure of performance, you can't base the results on account of the alignments, as you're using four 15" drivers with beefy class AB amplification on one hand, and a single 12" driver with a BASH amp on the other hand

Yes, but the prices are very similar $650 for a 4 way 15" AE IB with an EP2500 watt amp. Add the BFD and you are at $750.

[brucek]

Yes, but the prices are very similar

And if you had to have the IB professionally designed and installed such that you simply handed over a cheque (to ensure you were comparing apples to apples) ? ..........

I don't think the prices would be similar at all...

brucek

[SteveCallas]

It is assumed DIY will always beat commercial for the price, and obviously this is the case. I'm not comparing the two in terms of which is better - clearly the IB is the much better option in all aspects - I'm talking about making a comparison of the alignments in terms of "time domain performance", and for a legitimate comparison, you'd need something like four AE-15 LLTs.

[Darren]

brucek wrote:

And if you had to have the IB professionally designed and installed such that you simply handed over a cheque (to ensure you were comparing apples to apples) ? ..........

I don't think the prices would be similar at all...

brucek

I'm not sure anyone would pay to have an IB installed, it is simple although your point is well taken. I'd say the percentage of people that pay to have their IB installed is a fraction of a percent.

SteveCallas,

Four AE IB15 drivers come to $400. The EP2500 is about $250 delivered.

[Chrisbee]

brucek wrote:

And if you had to have the IB professionally designed and installed such that you simply handed over a cheque (to ensure you were comparing apples to apples) ? ..........

I don't think the prices would be similar at all...

brucek

I can't imagine why anybody with the most basic skills and tools couldn't throw an IB together. The driver rims can hide the quality of the hole cutting. So a cheap electric stick/jig saw can do the work here. A $20 Chinese router is just as easy to use if desired.

A manifold needs no real finishing at all if it is hidden by a simple screen. Or even rough painted internally the same colour as the surface behind which it is mounted.

[brucek]

I can't imagine why anybody with the most basic skills and tools couldn't throw an IB together.

Guess I didn't make my point too well.

You must assume a value for your labour when monetary comparisons are made to a 'store bought' subwoofer.

brucek

[Chrisbee]

brucek wrote:

Guess I didn't make my point too well.

You must assume a value for your labour when monetary comparisons are made to a 'store bought' subwoofer.

brucek

In no particular order of importance:

You call something "work" because if you weren't paid you wouldn't turn up.

Hobbies are what you do because you hate being paid just to have fun. Try it and see!

Making a hobby into work doesn't work. You end up hating it almost as much as real work because it puts unwanted pressure on you to use your time most usefully.

A hobby is the pleasant passing of time which allows you to feel usefully employed while doing nothing of real consequence.

Paying somebody else to do your hobbies for you is the corruption of the term "hobby". You become a part time employer and soon start setting conditions of employment, taxation, benefits etc and end up cheating yourself.

Valuing your time per hour expended on a hobby is accountancy. This is the worst form of work because it has no practical value whatsoever and eats into your useful hobby time. It also reminds you that you cannot possibly afford to employ yourself as a hobbyist. You are much too expensive to be employed on something as purposeless and non-productive as a hobby. In which case you should find somebody else who will take a much lower wage than you to do your hobby for you. This way lies madness.

[SteveCallas]

You must assume a value for your labour when monetary comparisons are made to a 'store bought' subwoofer.

Why? This train of thought has never made any sense to me. You may look at building a subwoofer as a chore, whereas most who actually build them look at it as a fun activity. So really, they are getting to partake in a fun activity and ending up with something that will outperform what they could have bought for anywhere near the same price point.

SteveCallas,

Four AE IB15 drivers come to $400. The EP2500 is about $250 delivered.

Umm, ok, I took your word the first time I still don't think you understand what I'm saying. I'm all for DIY, I have a DIY sub myself, you don't have to convince me that they are superior to commercial subs, and I realize and agree that the only comparison needed is in terms of price. That's all well and fine.

What I'm saying is you can't judge the ported alignment's "time domain performnace" in general based on a single (undersized in my opinion) 12" sub with a BASH amp compared to an IB using four 15" drivers with a beefy class AB amp. You can judge the SVS 16-46 sub's "time domain performance", but it doesn't represent all ported subs. Am I getting anywhere?

[Chrisbee]

Steve

Can you enlarge on what you are trying to say? I'm being conversational not critical.

Explain for the benefit of those who don't know how your Sonotube differs from an SVS cylinder except in a matter of scale.

I presume you have a decent amp behind it but the enclosure itself is still a ported reflex.

When I first had my SVS cylinder I was amazed how it seemed to come from nowhere. Bam!

The IB carries this surprise factor to a whole new dimension. Everything you hear is so unexpected.

The feeling is always that some prankster hit an empty oildrum with a large hammer while you had your back turned!

This has enorrnous shock value! Just like loud noises in real life in fact.

There is never any warning powerful enough to prepare you for what is coming.

It's not just the fast rise time either. It is the totally unexpected ability to stop dead on a very small dime.

The decay is so sharp and so instantly silent this must surely be indicative of a highly damped system?

Is this also a characteristic of your Sonotube?

How much of the damping in a ported enclosure is a direct result of the amplifier?

Since you have mentioned the unfair comparison of a brute AB amp with the Bash:

If you took a CS model SVS and drove it with a "pro" amp would it perform far better than a PC model with a Bash amp?

Would this even be a serious upgrade in your opinion?

Why don't we hear about people modding their SVS subs with proamps all the time?

I can't remember a single example of this ever being mentioned online except in the CS context.

[Ayreonaut]

SteveCallas wrote:

IB is well damped at all frequencies, LLT is well damped until subsonic frequencies.

By what mechanism is the IB damped?
By what mechanism is the large EBS damped in the upper bass?

SteveCallas wrote:

You can judge the SVS 16-46 sub's "time domain performance", but it doesn't represent all ported subs.

Yes, that's my point exactly. I posted here a comparison of a sealed sub and a 12" ported sub, but that's hardly representative of the large EBS subs, or of an IB. Both the large EBS and the IB are DIY, and each one fits a different situation. If you can't cut a hole in your floor or cieling, you'll want an EBS. If you can't put a refrigerator-size tube in your room, you'll want an IB.

Subjectively speaking, it sounds like the large tuned port will belt out some world class infrasonics, but it takes some time to excite that resonance, and so the leading edges (and trailing edges) get blunted. The IB is reported to start instantaneously, and stop on a dime, and I wonder exactly how it stops so quickly without the benefit of small box damping.

I didn't mean to start a face off, where the owners of each defend their subs virtues. Most of this has been debated endlessly at AVS. I'm just eager to see some hard data to go with all these impressions. I'm still waiting to hear back from Ilkka.