The Official "Can It Measure Well and Not Sound Good Thread?" - Page 6 - AVS Forum
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post #151 of 195 Old 05-20-2012, 08:52 PM
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i think you all missed the point of the OP

he's saying he can look at a piece of paper (measurements) and tell how good a sub will sound based on that alone

All this noise about noise.
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post #152 of 195 Old 05-21-2012, 07:14 AM
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Originally Posted by Auditor55 View Post

I didn't derail this thread. I'm just giving my pov just like everyone else.

So noted, from what i can see, we are all set.
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post #153 of 195 Old 05-21-2012, 07:24 AM
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Reviewers often do so with little validity in my book. A local guy Ed Mullen did a great job reviewing with plenty of measurements. Not sure how to review without GP first, then inroom measuring to find the best spot, then measurements from the LP......

Then said sub may fall short , do to output inabilities.
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post #154 of 195 Old 05-21-2012, 04:30 PM
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Quote:
Originally Posted by otk View Post

i think you all missed the point of the OP

he's saying he can look at a piece of paper (measurements) and tell how good a sub will sound based on that alone

I agree with the premise put forth in the OP. I think a full set of measurements can accurately predict how a subwoofer will sound. Take these 3 frequency response graphs for example:







Just based on the frequency response graphs, I am certain we all could describe how these 3 subs would sound, and, more importantly, how they would sound *different* from each other.


============================================================ ====================================


Now take a look at the maximum output measurements:







It's pretty easy to see which sub will have high output to very low frequencies, and which subs are far more limited in their output and extension.


============================================================ ====================================


Now look at the transient response:







It's obvious which sub is sealed and which subs are ported, and the frequency of the port tune.

You can find the full sets of measurements, including distortion, group delay and many other parameters, for all these subs and many more here:
http://www.data-bass.com/home

And MANY, MANY THANKS to Josh (Ricci) for taking these measurements and sharing them with us!

Craig

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post #155 of 195 Old 05-21-2012, 06:05 PM
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Of course, no matter how good a sub measures without a room around it, (outdoor, groundplane, as above), when a subwoofer is surrounded by a *room*, the frequency response of the room will dominate the sound quality. For example, here is the ground-plane FR of my subs, the Seaton Sound Submersive:



If you look at the response from 40 Hz to 100 Hz, the Submersive is +/- 1 dB through this range. From 40 Hz down to 20 Hz, it rolls off at 6 dB/octave. Below 20 Hz, it rolls off at 12 dB/octave. This sub should benefit from room gain, (AKA "pressure vessel gain"), at ULF's and be "flat" to well into the infrasonic range. However, the room will also cause resonances, and peaks and valleys in the FR. Here is a single Submersive in my room:



In spite of the very flat outdoor, ground-plane response, this same sub is +/- 12 dB in my room. If one were to just look at the in-room response of one of my Submersives, one would assume that this subwoofer was highly compromised and really awful. But that is not the case at all... the *real* problem is my room, and the listening/measuring position within my room.

Fortunately, with a combination of acoustic treatments, Audyssey XT32 room correction, and multiple, non-co-located Submersives, I can get the response back to very close to the "baseline" outdoor GP response:



Bottom line:

1. The outdoor GP measurements can profile the "baseline" output and frequency response of a subwoofer.

2. The room and listening position will determine the "transfer function" of the baseline response to the listener's ears.

3. A sub that measures well baseline outdoor GP will have a much higher probability of transferring that response to the LP.

4. There are many things that can be done to improve the "transfer function" of the sub to the LP.

5. However, there is nothing that can be done to improve the LF extension of a sub with compromised LF extension. Adding more of the same subs will increase total output, but LF extesnsion will be the same.

6. Measurements can, IMO, fully describe the sound quality of virtually any subwoofer.

Lombardi said it:
Perfection is not attainable, but if we chase perfection we can catch excellence."

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post #156 of 195 Old 05-21-2012, 06:39 PM
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thanks Craig. is that why you went with the submersives because of that one GP FR measurement ?

unless i read the first post of this thread wrong, the OP is also saying that words from reviewers are meaningless

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post #157 of 195 Old 05-21-2012, 07:31 PM
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Quote:
Originally Posted by otk View Post

thanks Craig. is that why you went with the submersives because of that one GP FR measurement ?

That one GP measurement was a significant factor in my "decision making" process. Prior to owning the Submersives I owned JL Audio F112's. They had flat, low distortion output to 20 Hz, but they completely "disappeared" below 20 Hz, and their limiters kicked in at output levels of 20 Hz @ ~ -10 dB below RL. I wanted more output and deeper extension. That GP measurement of the Submersive told me I could expect to reach my goals with a pair of SubM's. I eventually ended up with 3 SubM's, and I couldn't be happier. .

Quote:
Originally Posted by otk View Post

unless i read the first post of this thread wrong, the OP is also saying that words from reviewers are meaningless

I ascribe very little credence to subjective subwoofer reviews. They describe more about the room the subwoofer is in than about the "sound" of the subwoofer itself. I have shown graphically above the effect of a room on a subwoofer's response. These effects are totally dependent on the size, shape and construction of the specific room.

The descriptions of a subwoofers "sound" in a reviewer's room has very little relevance to the sound of the same subwoofer in "*my* room. Therefore, I only care about the outdoor GP measurement of a subwoofer's response. These measurements take the room out of the equation.

Look carefully at the outdoor, GP responses of the subwoofers above. It should become easy to "profile" the sound of each subwoofer based on the measured, baseline, outdoor, GP responses. Once you know the baseline "sound" of each sub, it should become obvious how to optimize the "transfer function" of that baseline response to the response heard and measured at the LP.

When you start with a compromised "baseline" response, it is much harder to optimize the response at the LP. It can be done, but it is impossible to go beyond the physical limitations of the subwoofers. If a sub rolls off precipitously at 20 Hz, it will be virtually impossible to get flat response to 15 Hz, even with multiples of the same sub. You need a sub with significant output below 20 Hz to allow for flat, (or rising), response below 20 Hz.

Bottom line, I re-iterate that, IMO, objective measurements provide all the information needed to make a subwoofer purchasing decision. Subjective opinions about SQ are worthless as they tell more about the room and LP than they do about the sub in question. Objective measurements, performed with a standardized and repeatable methodology, (such as Ricci has done), are much better predictors of ultimate subwoofer sound quality than subjective, (and potentially highly biased), listening impressions. IMO!

Craig

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post #158 of 195 Old 05-22-2012, 01:11 AM
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Quote:
Originally Posted by craig john View Post

I agree with the premise put forth in the OP. I think a full set of measurements can accurately predict how a subwoofer will sound. Take these 3 frequency response graphs for example:

....

Just based on the frequency response graphs, I am certain we all could describe how these 3 subs would sound, and, more importantly, how they would sound *different* from each other.

Craig

Hi craig, would you take a stab at writing a commentary about how you think those 3 subs would sound based on the measurements? I'm curious to see how such a commentary would look like.
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post #159 of 195 Old 05-22-2012, 02:02 AM
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There is more to predicting how a sub will sound than just good ground-plane data alone, but they are a great start. They are but just one leg of a three-legged stool. The other two legs are an understanding of the acoustics of the room the sub is going into + the setup choices.

Basically, if you know your room and you have an idea of how you plan to integrate the sub with your system, from the measurements alone it's fairly easy to choose the best sub for you. That is exactly how those measurements should be used to help someone make the best choice for themselves.
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post #160 of 195 Old 05-22-2012, 07:43 AM
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craig - great posts

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post #161 of 195 Old 05-22-2012, 11:24 AM
 
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Someone should define "sound good" what does it mean. Something may sound good to one person and may not sound to another person. Give examples if you can.
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post #162 of 195 Old 05-22-2012, 11:51 AM
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Quote:
Originally Posted by craig john View Post

That one GP measurement was a significant factor in my "decision making" process. Prior to owning the Submersives I owned JL Audio F112's. They had flat, low distortion output to 20 Hz, but they completely "disappeared" below 20 Hz, and their limiters kicked in at output levels of 20 Hz @ ~ -10 dB below RL. I wanted more output and deeper extension. That GP measurement of the Submersive told me I could expect to reach my goals with a pair of SubM's. I eventually ended up with 3 SubM's, and I couldn't be happier. .


I ascribe very little credence to subjective subwoofer reviews. They describe more about the room the subwoofer is in than about the "sound" of the subwoofer itself. I have shown graphically above the effect of a room on a subwoofer's response. These effects are totally dependent on the size, shape and construction of the specific room.

The descriptions of a subwoofers "sound" in a reviewer's room has very little relevance to the sound of the same subwoofer in "*my* room. Therefore, I only care about the outdoor GP measurement of a subwoofer's response. These measurements take the room out of the equation.

Look carefully at the outdoor, GP responses of the subwoofers above. It should become easy to "profile" the sound of each subwoofer based on the measured, baseline, outdoor, GP responses. Once you know the baseline "sound" of each sub, it should become obvious how to optimize the "transfer function" of that baseline response to the response heard and measured at the LP.

When you start with a compromised "baseline" response, it is much harder to optimize the response at the LP. It can be done, but it is impossible to go beyond the physical limitations of the subwoofers. If a sub rolls off precipitously at 20 Hz, it will be virtually impossible to get flat response to 15 Hz, even with multiples of the same sub. You need a sub with significant output below 20 Hz to allow for flat, (or rising), response below 20 Hz.

Bottom line, I re-iterate that, IMO, objective measurements provide all the information needed to make a subwoofer purchasing decision. Subjective opinions about SQ are worthless as they tell more about the room and LP than they do about the sub in question. Objective measurements, performed with a standardized and repeatable methodology, (such as Ricci has done), are much better predictors of ultimate subwoofer sound quality than subjective, (and potentially highly biased), listening impressions. IMO!

Craig

I always knew that rooms largely affected the performance of a subwoofer but never considered the room affect on subjective reviews. Interesting.
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post #163 of 195 Old 05-22-2012, 05:34 PM
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I have no real use for words. Give me the graphs.
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post #164 of 195 Old 05-22-2012, 07:56 PM
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Quote:
Originally Posted by Auditor55 View Post

Someone should define "sound good" what does it mean. Something may sound good to one person and may not sound to another person. Give examples if you can.

When comparing the 'sound' of different subs, you have to compare against a frame of reference or else the exercise is useless to everyone except you. A flat frequency response IS the reference frequency response as that is what the content creator (music, movie, etc.) uses as its reference; meaning if you listen to the content with a flat FR, that is the way the content creator wanted you to hear it.

'Sounding Good' = flat frequency response (or at least begins with a flat FR)

Make no mistake, many will not like the sound of a flat frequency response...and that is perfectly fine. However, that is a preference; and everyone's preference will never be the same and therefore useless to objectively compare.

If you don't agree that a flat FR is the reference to which audio should be judged, then its a futile conversation to have as everyone has their own 'preference'.

Assuming you agree to quantify/qualify against this reference, now you can start having some meaningful debate. IMHO.
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post #165 of 195 Old 05-22-2012, 08:29 PM
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Quote:
Originally Posted by dominguez1 View Post

When comparing the 'sound' of different subs, you have to compare against a frame of reference or else the exercise is useless to everyone except you. A flat frequency response IS the reference frequency response as that is what the content creator (music, movie, etc.) uses as its reference; meaning if you listen to the content with a flat FR, that is the way the content creator wanted you to hear it.

'Sounding Good' = flat frequency response (or at least begins with a flat FR)

Make no mistake, many will not like the sound of a flat frequency response...and that is perfectly fine. However, that is a preference; and everyone's preference will never be the same and therefore useless to objectively compare.

If you don't agree that a flat FR is the reference to which audio should be judged, then its a futile conversation to have as everyone has their own 'preference'.

Assuming you agree to quantify/qualify against this reference, now you can start having some meaningful debate. IMHO.

Those are good points, Dominguez. By definition, a flat frequency response (combined with low distortion) equals "high fidelity" in the classic sense.
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post #166 of 195 Old 05-22-2012, 08:41 PM
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Originally Posted by mojomike View Post

Those are good points, Dominguez. By definition, a flat frequency response (combined with low distortion) equals "high fidelity" in the classic sense.

Thanks mojo.

Bringing it back to the OP; that is why it's so important to strive for and show measurements. It validates your frame of reference so that other folks can take something away that is meaningful to them. For those that don't strive/show measurements, we can only assume it's based on your preference...in which case is great for you, but has no meaning to the general public.
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post #167 of 195 Old 05-22-2012, 09:26 PM
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Originally Posted by dominguez1 View Post


Thanks mojo.

Bringing it back to the OP; that is why it's so important to strive for and show measurements. It validates your frame of reference so that other folks can take something away that is meaningful to them. For those that don't strive/show measurements, we can only assume it's based on your preference...in which case is great for you, but has no meaning to the general public.

I say the same thing for speakers as well. So many people compare speakers and have no idea what responses they have and will say one is better than the other but really which ever speaker matches their room the best will sound the best. Once you dial in speakers and subs with at least a flat response then you can start to compare different speakers and subs. What is good sound, well it should be whatever sounds like a real instrument or sound effect(car crash), etc... As for how that is presented is personal tastes.
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post #168 of 195 Old 05-23-2012, 08:21 AM
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I say the same thing for speakers as well. So many people compare speakers and have no idea what responses they have and will say one is better than the other but really which ever speaker matches their room the best will sound the best. Once you dial in speakers and subs with at least a flat response then you can start to compare different speakers and subs. What is good sound, well it should be whatever sounds like a real instrument or sound effect(car crash), etc... As for how that is presented is personal tastes.

yet you don't hear anything about eq'ing speakers. what's the best way to do that? or are room treatments the best option?

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post #169 of 195 Old 05-23-2012, 09:36 AM
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yet you don't hear anything about eq'ing speakers. what's the best way to do that? or are room treatments the best option?

Always treat your room if you can, so you don't have to use as much EQ. EQ is not evil. Most audiophiles hear with their eyes! What I mean by that is they see a certain speaker with certain drivers and automatically assume it is better than something else. I would love for some to come over to my room which you don't see anything but screen and room treatments.
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post #170 of 195 Old 05-23-2012, 04:28 PM
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Unless a reviewer is speaking of the graphs, adjectives should be avoided. Discribing the facts of the measurements taken is more that enough.

I remember the days of reading Stereophile Mag, all that hoaky snake oil discriptions given to pages of total hogwash....bah, garbage !!!!

One guy i remember was kind of fun to read Cory Greenberg.

I'm really sorry Ed Mullen is out of the reviewing business, while i'm happy he is enjoying SVS, they garnered a hell of a sub reviewer......
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Quote:
Originally Posted by MKtheater View Post

Always treat your room if you can, so you don't have to use as much EQ. EQ is not evil. Most audiophiles hear with their eyes! What I mean by that is they see a certain speaker with certain drivers and automatically assume it is better than something else. I would love for some to come over to my room which you don't see anything but screen and room treatments.

That is why double blind listening test are necessary, preferably with trained listeners.
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Make no mistake, many will not like the sound of a flat frequency response...and that is perfectly fine. However, that is a preference; and everyone's preference will never be the same and therefore useless to objectively compare.

You care to explain that a little further. In your opinion, why wouldn't many like the sound of a flat frequency response. I've heard that mentioned before.
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post #173 of 195 Old 05-23-2012, 05:19 PM
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Quote:
Originally Posted by jchong View Post

Hi craig, would you take a stab at writing a commentary about how you think those 3 subs would sound based on the measurements? I'm curious to see how such a commentary would look like.

Hi jchong,

I could certainly do this, but I am going to pass on this request for 3 reasons:

1. IMO, the graphs speak for themselves. I chose these graphs as examples of different FR's only, not to make "examples" out of any of these subs.

2. There are many owners of these subs on the forum. I don't wish to offend any of those owners. More importantly, I don't think the point of this thread is to discuss the SQ of individual subs.

3. The graphs speak for themselves.

The OP said:

Quote:


(Deep) Extension
(High) Output
Flat Frequency Response
Low Distortion, (especially as output levels rise, and at the lowest frequencies).

In other words Low, Loud, Flat, Clean

I posted graphs showing extension, (Low), output, (Loud) and FR, (Flat). IOW, everything the OP asked for except distortion, (Clean), graphs, (which are nonetheless available on the Data-Bass website.)

The baseline "sound signature" of each of those subs can be gleaned from the graphs. Nonetheless, how any specific sub will sound in any particular room will be a function of the room, the listening position and the optimization efforts the owner/installer has gone to to optimize the "transfer function" of that sub to the LP. Even a marginally performing sub can be made to sound good by installation optimization. However, NO sub can go beyond it's performance capabilities and physical limitations, and these will always be determined by the "baseline" outdoor, GP measurements.

For example, a sub with a -3 dB point of 25 Hz will never have deeper extension than 25 Hz, no matter how it is installed in a room. Even if you add multiples of that same sub, the combined response will still have a -3 dB point of 25 Hz. The maximum output at 25 Hz will go up, but the roll-off below that will stay the same. If you want deeper extension than 25 Hz, you need a subwoofer with deeper extension, pure, plain and simple.

I will also state that I think the difference in "transient response" between sealed subs and "vented" subs is clearly audible. For example, here is the transient response of the SVS PB13 Ultra in sealed mode:



and here is the response of the exact same sub in 15 Hz "ported" mode:



The LF roll-off is obviously different, but the decay time difference is, IMO, going to be much more audible than the LF roll off. The LF roll off can be compensated with an LF boost, (i.e., a Linkwitz transform circuit.) The slow decay time can not be compensated for with any current technology, and that slow decay will muddy the sound of the bass, and interfere with the response all the way up into the midrange.

Craig

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post #174 of 195 Old 05-23-2012, 05:27 PM
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Originally Posted by Auditor55 View Post

You care to explain that a little further. In your opinion, why wouldn't many like the sound of a flat frequency response. I've heard that mentioned before.

It happens when people like to over accentuate certain frequencies based on the type of music or movies they listen to (their preference).

Some people may like to boost 20hz and below for big ULF HT movies. Others may prefer rap, house music, etc. and like boosting the 25-40hz range to get them that 'boom'. Others may listen to a lot of rock, and like that 'mid-bass slam' and boost 60-80.

I've been in that camp many times...and actually why I prefer flat now. Tweaking your response to certain content can be a lot of fun, but the downside is that the other frequencies now sound unnatural as a result. Overtime, it started to annoy me especially if you listen to a wide variety of content.

Door slams in movies turn into mini-earthquakes; rap music becomes fatiguing; Drum beats drown out vocals; etc. etc.

Having a flat response ensures your listening to it the way it was intended...or at least the baseline starting point to listening as intended. The other factors come into play such as controlling distortion, group delay, ringing, dynamic compression, etc.

Generally speaking, FR dominates what we hear and the other factors provide the subtleties and nuances. IMHO.
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post #175 of 195 Old 05-23-2012, 05:32 PM
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Quote:
Originally Posted by Auditor55 View Post

You care to explain that a little further. In your opinion, why wouldn't many like the sound of a flat frequency response. I've heard that mentioned before.

Human hearing deficiencies at low frequencies. Google "Fletcher-Munson Curve".

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post #176 of 195 Old 05-23-2012, 05:48 PM
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Quote:
Originally Posted by craig john View Post

Hi jchong,

I could certainly do this, but I am going to pass on this request for 3 reasons:

1. IMO, the graphs speak for themselves. I chose these graphs as examples of different FR's only, not to make "examples" out of any of these subs.

2. There are many owners of these subs on the forum. I don't wish to offend any of those owners. More importantly, I don't think the point of this thread is to discuss the SQ of individual subs.

3. The graphs speak for themselves.

While the graphs speak for themselves, one issue is that most people don't know what they are saying

The other thing is how data is interpreted. There can be one set of data but different interpretations. It is this interpretation and how it is correlated to how a sub sounds that is of interest to me. Hence I asked if you would take a stab at writing the commentary. I'm sure if we got 5 different people to write it there would be 5 different commentaries.

Quote:


I will also state that I think the difference in "transient response" between sealed subs and "vented" subs is clearly audible. For example, here is the transient response of the SVS PB13 Ultra in sealed mode:

and here is the response of the exact same sub in 15 Hz "ported" mode:

Can you share on how you read that? I've always thought the group delay chart was most telling to see the difference in sealed vs ported.

Going back to the 2 waterfalls above, let's look at the area from 30Hz upwards only (since below that the roll off is quite different). Both look quite similar to me. Both mostly disappear by 150ms, except for some bits at 30, 40 and 90-120Hz. I'm having a hard time seeing any big difference in the chart.

Note: I'm in the camp that doesn't know what the charts are saying
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post #177 of 195 Old 05-23-2012, 07:00 PM
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Originally Posted by jchong View Post

Going back to the 2 waterfalls above, let's look at the area from 30Hz upwards only (since below that the roll off is quite different). Both look quite similar to me. Both mostly disappear by 150ms, except for some bits at 30, 40 and 90-120Hz. I'm having a hard time seeing any big difference in the chart.

Note: I'm in the camp that doesn't know what the charts are saying

The ports in a ported sub are "tuned" to a specific frequency. The air in the ports resonates at the frequency of the port tune and makes sound. Virtually ALL of the sound produced by the ports is produced at, and around, this port tune frequency. Above that frequency, the driver(s) make all the output. Below that frequency, the driver unloads and the response falls off very rapidly. Therefore, a ported sub will have very little output below the tune frequency of the port.

Since the air in the ports is resonating, it has inertia, and that inertia keeps it resonating even after the energy exciting it to resonate has stopped. This causes a prolonged decay time at the port tune frequency. The ports in the SVS sub are tuned to 15Hz. The prolonged decay time starting at about 20 Hz is indicative of the air in the ports continuing to resonate after the signal has stopped.

With the sub in "sealed" mode, the ports are blocked and there is no air flow in them. Therefore in sealed mode, the decay time is similar, and foreshortened, across the whole bandwidth.

The two modes should look the same above the port tune, and they do. The difference is how they decay at, and around, the port tune.

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post #178 of 195 Old 05-24-2012, 04:53 AM
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craig, thanks for the reply.

As you said, the difference lies around the port tune. When I compare the waterfall to the group delay chart I see the correlation now. The ringing around the port tune is also the peak of the group delay graph (eureka moment!).

From this it appears as if the difference between sealed vs ported is only at the port tune. However, say we play some music which has little info below 30Hz, then theoretically both modes should sound the same yet they don't, there is a subtle but audible difference. FYI, I do own the PB13U and have experimented with the different modes. Since port tune is out of the picture, what else could account for the subtle but audible difference between the sealed vs ported mode?
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post #179 of 195 Old 05-24-2012, 04:55 AM
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I am probably swimming in the deep end here but what the hell. Not sure if this has been mentioned, but don't we have to make sure the sub is measured properly in the first place before we can make an assumption on how it would sound? It may make a difference or not, I am not an expert. But, I remember when AVtalk was doing a lot of sub testing. They once tested the Sub Utopia Be from JM Labs. It is a ported sub but all they did was take measurements from the driver. I don't know how you are supposed to measure a ported sub, but they did not take into account the output at the port. So that really skewed the data I think. Distortion, extension, etc... would probably have been different if the also tested it at the port. I have heard this sub in person and it is still one of the best subs I have ever heard. So while I do agree that measurements are important, and you can probably get an idea of how it would sound, you are also at the mercy of the people who are doing the tests and banking that they did them correctly.
OK I know leave this back to the professionals .

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post #180 of 195 Old 05-24-2012, 05:13 AM
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Quote:
Originally Posted by jchong View Post

craig, thanks for the reply.

As you said, the difference lies around the port tune. When I compare the waterfall to the group delay chart I see the correlation now. The ringing around the port tune is also the peak of the group delay graph (eureka moment!).

From this it appears as if the difference between sealed vs ported is only at the port tune. However, say we play some music which has little info below 30Hz, then theoretically both modes should sound the same yet they don't, there is a subtle but audible difference. FYI, I do own the PB13U and have experimented with the different modes. Since port tune is out of the picture, what else could account for the subtle but audible difference between the sealed vs ported mode?

In comparing the response between sealed and ported modes, we can see that there is a different shape from about 70hz on down. In the sealed mode, there is a rolloff that subtly begins at about 70hz. The shape from this point and below is different enough to give a different sound. Which is more accurate would depond on the characteristics of your room as well as your setup.
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