Optimized impulse responce of subwoofer; Horn VS Vented box - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 21 Old 03-03-15, 06:57 AM Thread Starter
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Optimized impulse responce of subwoofer; Horn VS Vented box

Hi,

I am investigating how to get best possible impulse response from a sub that will go all the way or close to 20Hz. Ideally I want to play 20Hz square-wave and it will still look as a square-wave when I measure it with a good microphone.
My first approach was that a horn loudspeaker would be ideal for this.
But when doing some simulations with a vented box of a fraction of the size actually had better impulse response!

Do anyone has any comments regarding this?
My expectation was that a horn would have a much better impulse response than a vented box. The horn is not a resonant system in the same way as a vented box and the general comments and experiences (including my own) is that horns are much more direct and punchy and not at all boomy in the same way as many vented boxes.
If this punchyness do not come from a better impulse response, what is it then that that makes bass horns so direct?
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post #2 of 21 Old 03-04-15, 12:22 AM
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It maybe just me but I would NOT be playing a square wave through your sub the speaker will not care one bit for it and depending on the amp it will not either.

What amp are you going to use and why would you ever want to reproduce something your driver should never see.
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post #3 of 21 Old 03-04-15, 03:38 PM Thread Starter
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Re: Optimized impulse responce of subwoofer; Horn VS Vented box

The important thing is not playing square waves and listening to them.
The important thing is to play music with perfect transient information intact and no ringing.
I want to be able to play a square-wave and have it reproduced perfectly because it shows that the system do not have phase distortion issues.
It is perfectly harmless to play square-waves through any loudspeaker system, just listen to any track containing a Moog synthesizer.
Of course it depends on the level. If you are playing a square-wave because your 2000W amp is clipping then it is probably not so good. But if you are playing a square-wave at 1 Vrms or 2,83 Vrms most system will not have any problem with it.
The problem is that most systems will not be able to play a 20 Hz square-wave that still looks like a square-wave!
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post #4 of 21 Old 03-04-15, 04:07 PM
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Re: Optimized impulse responce of subwoofer; Horn VS Vented box

Square wave reproduction requires a wide frequency response because the wave consists of the primary frequency and an infinite number of odd-order harmonics. The poor result of the horn-loaded system reflects a more limited operating bandwidth compared to the vented subwoofer. The best test would be how each performs with optimized satellites, crossovers and delay (if applicable) in place. Not many systems can produce good square waves at any frequency and/or listening position and the significance of the characteristic is hotly debated among audiophiles.
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post #5 of 21 Old 03-04-15, 04:12 PM
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Have you hooked your amp up to a scope and looked at the output and see if it can make a perfect square wave? Most amps have issues with that. What amp are you using that can make a perfect square wave on a quality scope please post some pics of it as I have seen many amps measured and most have issues and I am not talking cheep class D amps.

Even the Parasound Hca-3500 that I own does not produce a perfect square wave are you using a $5000 + amp for a subwoofer?

Also what are you using to make the square wave, are you using a sound card on a computer that will in most test I have seen fail to do such correctly or are you using a high quality generator that can do such?

What kind of test equipment do you own? I used to service electronic's and have a bench setup with stuff and from what I have measured over the years finding a piece of gear that can do such is not common.
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post #6 of 21 Old 03-04-15, 04:55 PM Thread Starter
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Re: Optimized impulse responce of subwoofer; Horn VS Vented box

Thanks for the inputs.
I should maybe clarify a bit more. These two speakers are simulations. I have not built them yet.
I was more looking for a theoretical discussion on how speaker parameters effect group delay, impulse response but more importantly audible parameters such as "punch" or "depth".
When measuring I can borrow a Audio Precision, Clio or Klippel system from work, but first I want all the theoretical stuff to add up.

My feeling is that I have always loved the punch of horn loaded subs. But looking at these simulated responses, the vented sub actually gives the impression of being the more punchy arrangement.
Any comments on this?
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post #7 of 21 Old 03-04-15, 05:50 PM
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With ringing if you remove the box from the equation and look at the driver the driver with the higher mass in theory take more time to stop moving.

A lot of horn subs seem to use cones that are lighter in mass then say a ported subwoofer.

However with that being said the amps ability to control the driver is based on a lot of factors and where it all may end up is hard to say.

The ported subs I have spent time with that sounded bad were not built correct and we're in too large or small of a box. My guess is that a subwoofer that is in too large of a box would cause it to ring a bit more then one that is in a smaller box and the same could be said with sealed sub. The air acts as a cushion and if I recall helps control the driver too much air being able to easily be moved and the sub can keep playing. This is a guess however and I could be very wrong on that.
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post #8 of 21 Old 03-04-15, 06:13 PM
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Here try reading this old thread on horn vs ported it may answer what your looking for and what you may run into with both types of setup's

http://www.diyaudio.com/forums/subwo...subwoofer.html
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post #9 of 21 Old 03-04-15, 09:14 PM
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Re: Optimized impulse responce of subwoofer; Horn VS Vented box

Quote:
Gubbe wrote: View Post
Thanks for the inputs.
I should maybe clarify a bit more. These two speakers are simulations. I have not built them yet.
I was more looking for a theoretical discussion on how speaker parameters effect group delay, impulse response but more importantly audible parameters such as "punch" or "depth".
When measuring I can borrow a Audio Precision, Clio or Klippel system from work, but first I want all the theoretical stuff to add up.

My feeling is that I have always loved the punch of horn loaded subs. But looking at these simulated responses, the vented sub actually gives the impression of being the more punchy arrangement.
Any comments on this?
Subwoofers with the lowest group delay are generally critically damped sealed box designs. These have a large box volume by commercial standards and can produce excellent results - very clean and musical. "Punchy" often means exaggerated and may wear thin quickly. Accurate and deep are the most desirable traits in a subwoofer. The best results are usually in a treated room with two or (preferably) more subwoofers placed in locations that smooth the response at the listening position and make the best use of room gain. Electronic room correction can add icing to the cake, but is not a panacea.

My current home theater uses four Acoustic Elegance SBP-15 subwoofers each in large sealed enclosures (about 8 cubic feet) and driven by an SVS STA-800H amplifier in a large acoustically treated room. Capable of plumbing the depths of any source material at levels that would drive any sane person from the room, the low distortion and smooth frequency response of this system is among the best I've encountered in a domestic environment. Measurement equipment (Dayton Audio Omnimic system and a wide range of test material) confirm the results and greatly aided in achieving the best sound.
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post #10 of 21 Old 03-04-15, 09:54 PM
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Off topic how low can you get while still having a flat response and what size room are you working with?
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