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Author Topic: What would you call this?  (Read 3530 times)

duane massey

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What would you call this?
« on: July 29, 2014, 09:48:22 pm »

Back in the 70's we used to describe a front-loaded horn system as having good transient response, or being "tight". My perception of vented or folded bass bins has always been that they can get sloppy or "boomy" at high volume levels. It goes beyond just frequency response, but more about accuracy? Not certain how this would be measured, you'd have to measure the actual response of the cabinet at higher output levels and look at the beginning and ending of the original sound versus the performance of the cabinet. What is the correct term for this aspect of a speaker cabinet?
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Duane Massey
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David Morison

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Re: What would you call this?
« Reply #1 on: July 30, 2014, 07:48:47 am »

Back in the 70's we used to describe a front-loaded horn system as having good transient response, or being "tight". My perception of vented or folded bass bins has always been that they can get sloppy or "boomy" at high volume levels. It goes beyond just frequency response, but more about accuracy? Not certain how this would be measured, you'd have to measure the actual response of the cabinet at higher output levels and look at the beginning and ending of the original sound versus the performance of the cabinet. What is the correct term for this aspect of a speaker cabinet?

Might be Group Delay you're thinking of?
That is related to phase which in turn relates to frequency response, so there may be other components to the difference in sound too, distortion being one for example.

HTH,
David
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John Roberts {JR}

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Re: What would you call this?
« Reply #2 on: July 30, 2014, 10:17:23 am »

I am not the speaker guru here but I would look for what you are talking about with short tone bursts. While looking at audio does not always correlate well with what we hear, I suspect you will see a difference between a "tight" infinite baffle, and "loose" ported cabinet.

Part of the no free lunch (my theme for today) the extra port output comes from somewhere.

JR

[EDIT- for a perhaps amusing and related anecdote...  back in the late '70s I ask Rudy Bozak in passing why didn't he add a port to his huge "concert grand"(?) speaker system to extend the LF response down even further? His response was that he tried it before and the ported cabinets just don't sound accurate recreating classical music.  [/edit]
« Last Edit: July 30, 2014, 10:23:21 am by John Roberts {JR} »
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Art Welter

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Re: What would you call this?
« Reply #3 on: July 30, 2014, 04:46:31 pm »

Back in the 70's we used to describe a front-loaded horn system as having good transient response, or being "tight". My perception of vented or folded bass bins has always been that they can get sloppy or "boomy" at high volume levels. It goes beyond just frequency response, but more about accuracy? Not certain how this would be measured, you'd have to measure the actual response of the cabinet at higher output levels and look at the beginning and ending of the original sound versus the performance of the cabinet. What is the correct term for this aspect of a speaker cabinet?
FLH (front loaded horn), whether straight or folded, can sound "tight", as can BR (bass reflex) if run within their linear limits. Back in the 70's it was unusual to have enough power to exceed Xmax (linear displacement limit) in a horn loaded cabinet, so they still remained "tight" at FTB (full tilt boogie), while BR cabinets excursion would be greater at similar power levels, exceeding Xmax.

When Xmax is exceeded, the magnet structure has less control over the cone, transient response and damping worsens, distortion increases exponentially, sloppy or "boomy" response is the result. Lots of second and third harmonic distortion from a 50 Hz fundamental makes for a bunch of 100 and 150 Hz "boom" that can't be equalized out.

Distortion can be easily measured now, though back in the 70's, not so much. It wasn't until this century that I started measuring it, made a  lot of  response  differences between different designs and drivers much easier to understand.

Art
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Charlie Zureki

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Re: What would you call this?
« Reply #4 on: August 08, 2014, 09:50:22 pm »

FLH (front loaded horn), whether straight or folded, can sound "tight", as can BR (bass reflex) if run within their linear limits. Back in the 70's it was unusual to have enough power to exceed Xmax (linear displacement limit) in a horn loaded cabinet, so they still remained "tight" at FTB (full tilt boogie), while BR cabinets excursion would be greater at similar power levels, exceeding Xmax.

When Xmax is exceeded, the magnet structure has less control over the cone, transient response and damping worsens, distortion increases exponentially, sloppy or "boomy" response is the result. Lots of second and third harmonic distortion from a 50 Hz fundamental makes for a bunch of 100 and 150 Hz "boom" that can't be equalized out.

Distortion can be easily measured now, though back in the 70's, not so much. It wasn't until this century that I started measuring it, made a  lot of  response  differences between different designs and drivers much easier to understand.

Art

   +1

   Thankful for advancements in Component and Materials designs.

 Hammer
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duane massey

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Re: What would you call this?
« Reply #5 on: August 09, 2014, 06:56:56 pm »

Art, I suppose distortion is a good term for what I'm trying to discuss. "What goes in" should match "what goes out" sort of thing, but do you measure distortion as a "snapshot" or as a time-lapse entity? And you would have have to take measurements at several different volume levels to truly determine the accuracy of the cabinet in question, right? Would this be something a modeling program would be able to predict? So many questions, such a small amount of memory cells left....
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Duane Massey
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Ivan Beaver

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Re: What would you call this?
« Reply #6 on: August 09, 2014, 07:23:38 pm »

Art, I suppose distortion is a good term for what I'm trying to discuss. "What goes in" should match "what goes out" sort of thing, but do you measure distortion as a "snapshot" or as a time-lapse entity? And you would have have to take measurements at several different volume levels to truly determine the accuracy of the cabinet in question, right? Would this be something a modeling program would be able to predict? So many questions, such a small amount of memory cells left....
The level will greatly affect the amount of distortion.

This is one area that an RTA is very helpful.

One simple way is use a sine wave tone and look at the fundamental and the harmonics.  The level of the harmonics tells the distortion.  BE SURE to use an RTA that has a fine enough resolution to land a "bar" on the harmonic freq.  At least 1/6th oct-but 12th or finer is better.

Lets say you use 60Hz as your test tone.  Look at the level of 120Hz.  If it is 20dB down-then that is 10% distortion.  10dB down is just over 30% distortion.  30dB is around 3% distortion

A fun thing to do is to use say 60Hz and drive it till the harmonics are 20dB down.  Then sweep down in freq and watch how the distortion rises.

You can find cabinets that will reach 100% distortion-with the same drive level.

What happens at one freq does not also happen at other freq.
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Barry Singleton

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Re: What would you call this?
« Reply #7 on: August 09, 2014, 08:38:03 pm »

  Hi Duane;

  If you get it figured out be sure to let me know.

  I am in the middle of a full on audio midlife crisis and am trying to quantify exactly what you are asking about. 

  I'm a measurement nut but try as I might I can not find a metric that really explains this. A clean impulse response is part of it as is an efficient use of power via a horn that delivers a strong grip on the driver thus limiting excursion even under real power.

Here's what I know, I think,,,

  RCA Ubangi's have it, JBL 4550's, not so much. Community Boxer Bass Horns have it in spades.

I have tapped horns and folded horns big and small and they have pretty incredible output but they leave something on the table, like the sharp impact.

  It's funny but you know instantly when you hear it.

Barry.
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duane massey

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Re: What would you call this?
« Reply #8 on: August 09, 2014, 08:46:02 pm »

We used to say "bump, not boom". At higher levels most of the conventional cabinets back then, including folded horns, would just sound sloppy or "boomy", whereas straight horns seemed to be much more accurate at the higher levels, and also demanded less power to achieve those levels. Somehow "bump" and "boom" just don't seem to be proper technical terms.
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Duane Massey
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Ivan Beaver

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Re: What would you call this?
« Reply #9 on: August 09, 2014, 10:04:05 pm »

  Hi Duane;

  If you get it figured out be sure to let me know.

  I am in the middle of a full on audio midlife crisis and am trying to quantify exactly what you are asking about. 

  I'm a measurement nut but try as I might I can not find a metric that really explains this. A clean impulse response is part of it as is an efficient use of power via a horn that delivers a strong grip on the driver thus limiting excursion even under real power.

Here's what I know, I think,,,

  RCA Ubangi's have it, JBL 4550's, not so much. Community Boxer Bass Horns have it in spades.

I have tapped horns and folded horns big and small and they have pretty incredible output but they leave something on the table, like the sharp impact.

  It's funny but you know instantly when you hear it.

Barry.
A few years ago we did a "quick late night test" after a long day-so take this with a grain of salt.

We had several subs and some had more of "it" than others did-when using the same low pass filter (80Hz).  So we measured the freq response of each of them. and noticed that it was quite different.

FIRST we took the cabinet and eqed up the others to its response-which had a greater amount of output above 80Hz.  The sound got closer but still not the same.

The next test was to "eq down" all of the boxes to the cabinet with the least amount of "punch or impact".  When we did this-there was very little (almost none to speak of) difference between the cabinets.

So our conclusion was that if you simply ignore the actual freq response (as was done in years past when measurement gear was not so prevalent), then the cabinet with the most output in the 80-150hz range will have more "punch or impact".

We (myself included) would simply set eq points and some cabinets simply had more impact than others due to greater HF(in the bass region) output.

But when you do a "proper system alignment", in which the actual freq response is considered, there is no real difference.

I would like to find the time to redo the test to confirm this quick test.

One of the reasons the "boxer" horn (and I remember some old Martin 2x15" straight horns as well) had such impact was due to a couple of things. 

First with no bends, the upper freq come straight out (along with distortion harmonics).

Second the short horn provided lots of gain  in the "punch" range and not so much at the lower freq (like the W bins did) so the ratio of the upper range to lower range is greater.

So the real question is "What do you want?  accurate freq response or fun?"

Of course the answer is both-but in my experience (which directly is limited I admit), is you can't have both.

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Ivan Beaver
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ProSoundWeb Community

Re: What would you call this?
« Reply #9 on: August 09, 2014, 10:04:05 pm »


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