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Old 19th September 2006, 11:33 PM   #21
v-bro is offline v-bro  Netherlands
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http://www.acoustisoft.com/basics.html
This may be of interest to you?
Transient response in this case is measured by a microphone, on a certain distance in a specific room.
You give the speaker a pulse with virtually no wavelength(only amplitude) and "hear" with the microphone how long it takes to fade away(go back to zero) and how many times it crosses zero and in what way..
Don't know exactly what a standardised setup for such a measurement
should look like(supposedly at 1 meter and a certain voltage?)

The box and the room will give reflections that will influence the transient response, the amplifier dampening factor of an amp is of little influence to this... correct me if I'm wrong (think any modern amp will not produce dramatical differences in transient response graphs of a loudspeaker).

With simulation software you can maybe make it possible for you to compare things a little bit, but It'll never predict the real life situation..

But I mostly find speakers placed nearer to walls "BOOM" and would
prefer a more "decoupled" aproach, when it is preferred to sound a little more "exact".
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Old 20th September 2006, 12:31 AM   #22
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Quote:
The box and the room will give reflections that will influence the transient response
actually the room will provide "transient reflections" and dont actually affect the transient response of the driver. These show up as the secondary and tertiary(and so on) peaks on the impulse response graph.
Slam and boom and fast and slow are all laymen terms used to describe the relative levels of upper bass and lower bass, in addition to any uncontrolled cone motion(or lack of) due to the enclosure tuning.
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Old 20th September 2006, 03:06 AM   #23
v-bro is offline v-bro  Netherlands
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quote:
""The box and the room will give reflections that will influence the transient response"
actually the room will provide "transient reflections" and dont actually affect the transient response of the driver".

True, filtering can also affect the bass(or indeed actually mid-bass) to be experienced "slow" or "fast"(or however you want to call this experience) when things were not done right.
In my previous post I was solely writing about the experienced sound in a particular room. Maybe I should have added that in a transient test graph the line would have shown several (reflected)peaks...

Waves reflected in the room I think will only cloud the experience in relation to the source signal. As it will reach your ears in another timing, and interfere with directly radiated waves and other reflected waves, combining them to amplify or dip and may create the "boom experience" on some places. Most of all when standing waves occur amplified low frequencies can occur too.
Though wanting to produce 120 db's it might help indeed....;-)

Bass is a tough sucker though, goes through flesh and bone.
Where mid and high frequencies benefit from a good dosage of reflections in order to create a "pseudo" realistic reproduction of truth, bass is better off outside or in a dead room. Everything in a room will remain a compromise to reality. Getting it as right as possible in a room might involve eq-ing or having everything placed and designed specifically for a certain room when it comes to experiencing a "flat" frequency response. Experiment experiment experiment.....

Afterall we're not dealing with poor enclosure tuning cone slowing matter here I think, we're dealing with a person listening in a room in the future who'se speakers are yet to be built...
And you can unleash a lot of theory on the design, accurate sound does not give everybody more listening pleasure, listening and experimenting right mostly does the trick better. I've had greater breaktroughs by "hunches" than with my calculator..

I like richie00boy's comment:"one mans musical is another mans monstrosity".

No offense to anybody, just trying to help determine what important influences are in acoustics(the whole picture)and what aren't...
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Old 20th September 2006, 07:34 AM   #24
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Lot of good information here guys. If you have any more links to some good reads, I will gladly pay my dues just like everyone else.

Quote:
Originally posted by v-bro
quote:
Afterall we're not dealing with poor enclosure tuning cone slowing matter here I think, we're dealing with a person listening in a room in the future who'se speakers are yet to be built...
And you can unleash a lot of theory on the design, accurate sound does not give everybody more listening pleasure, listening and experimenting right mostly does the trick better. I've had greater breaktroughs by "hunches" than with my calculator..
Very true. This is my next project that I am planning/thinking about. Currently I am getting ready to build my first sub, just for practice, then will give it to my sister for christmas.

I have an old JBL GT1200 sitting around NIB, so I figured, hey, let's do something with it. I ordered up everything I needed including the 300w BASH amp from Partsexpress. It was on sale!

After tinkering with WinISD for a while, I've come up with this. It's not the best and buying a different speaker would work a ton better, but I am just using what I have sitting around.

Click the image to open in full size.

The db number in the upper right corner is with a 250w signal. It's roughly 9db down from it's peak. Also I added a 2nd order LP x-over @ 110hz. I could get a better response with a bigger box, but my group delay would go crazy and I would run out of excursion at 35hz with just 70w of power. So 3.2ft^3 is the largest I can go.
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Old 20th September 2006, 08:03 AM   #25
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Quote:
Originally posted by looneybomber

I am confused. I thought transient response was the time it took the speaker to go from one position (sitting still) to another (moving). It's that transition that I thought was measured and called "transient response". If that is not transient response, what is that called?

Also, do ported boxes increase that time from not moving to moving, or is that more controlled by the amp and its damping factor?
Yes that's what transient response is, but think about it - a sub is fed from a low-pass filter so it will never see a fast changing signal.

A vented box generally has more overshoot of transients/settling time.

Just off to try and find kelticwizard's excellent graphs...

edit: here it is for sealed

http://www.diyaudio.com/forums/attac...amp=1069945507

and now vented

http://www.diyaudio.com/forums/attac...amp=1081342894
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Old 21st September 2006, 01:07 AM   #26
v-bro is offline v-bro  Netherlands
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Exellent graphs indeed,

but to keep the birds eye view, some closed speaker designs have poorer experienced accuracy than some vented ones.

Always keep in mind the whole picture, for some vented speaker designs use specifically adapted drivers and some closed designs as well. Though most drivers are designed for several type of enclosures and give fine results in both, this is mostly done for commercial reasons. It would be always preferable to design a driver for the housing it's intended to be used in.

Read a good speaker design book on "thiele and small" parameters and you will probably find a table showing the relation between mechanical, electrical and acoustical physical quantities.

You may find a translation in your language of H.H. Klinger's "Lautsprecher-baubuch fur Hifi-Amateure und Musikfreunde"1989).
I bought it(dutch translation) in 1990 and advise anyone who wants to start understanding the deeper knowledge of loudspeakers to read it. In the book you find a very clear table like I just mentioned(with symols). Many designs use combinations of either mechanical, electrical or acoustical quantities that can only be calculated or tweaked right knowing the schematic in which all factors are incorporated.

Example: a bandpass subwoofer acoustically filters (like an inductance) mid and high frequencies (by air mass) and may save on electrical filtering.

Merely calculating this would have to incorporate so many factors that it would very likely not give accurate results in the end.
The value in mh resulting from this acoustic filtering can be better predicted than calculated I think. By knowing the slope will become steeper. Building an electric filter out of the enclosure and unwind/wind up the coil can help you get it right. And knowing larger values lower x-over frequencies and smaller values make them higher both for high and lowpass filters(for beginners).

Just using calculation software many times won't lead to good results unless you know what you're doing.

Once you know what you're doing solving problems is easy!
Or problems won't even occur...

My brother bought a new house, placed his speakers on the floor, straight in a rectangular room. He called me asking to help him out because it sounded awfull. I rotated his whole "relax corner" 45 degrees, put the speakers on a heavy tile on 3 "speaker toes" and made dramatical improvements(less standing waves for instance, still have to hang some carpets and stuff).
3 toes cant waver btw(hint).

That's why experimenting is so important, but always investigate your findings unless you're sure about them...

And see things in prespective, my brother would have noticed less if I had shrunk the content of his speakers 5 liters (from 46) or if I had put Van den Lul cables in there(dutch joke, I know it should be "Van den Hul")....

Your ears shall seperate the ******** from the truth.

Also never go for first impressions (the best materials used in loudspeakers often take longer periods to "break in". (therefore they live long)).
Some will "grow" better, some deteriorate fast.
Foam woofer cone edges for instance "sound" great almost from the start, rubber ones though live much longer and-if properly manufactured sound good too.
I find paper woofer cones mostly "sound" best, and often handle heat better than poly-whatever cones, dampen better than metal cones(domes!), but when made light they tend to fold quicker (fail mechanically).

Have to admit though that I am still learning every day and will keep making mistakes(I can learn from). Nobody will probably ever invent the perfect loudspeaker.

Key is to be satisfied at a certain acceptable degree of compromise and enjoy and listen to music.....
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Old 21st September 2006, 04:27 PM   #27
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Hello All

Here is another EQ solution that you might like even better.

http://www.behringer.com/DSP1124P/index.cfm?lang=ENG

12 band parametric per channel and $129 retail

Also check out the EP1500 & EP2500 power amps at the above link.
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Old 21st September 2006, 05:56 PM   #28
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Quote:
Originally posted by richie00boy
Yes that's what transient response is, but think about it - a sub is fed from a low-pass filter so it will never see a fast changing signal.
How fast is "fast" when refering to "see a fast changing signal"?

Quote:
Originally posted by TwisterZ
Hello All

Here is another EQ solution that you might like even better.

http://www.behringer.com/DSP1124P/index.cfm?lang=ENG

12 band parametric per channel and $129 retail

Also check out the EP1500 & EP2500 power amps at the above link.
Just minutes ago I purchased this.
Behringer DEQ2496 mostly because I can plug a mic into and annalyze my frequency response. From what I've been reading, that FBD you posted would work good too.
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Old 21st September 2006, 06:21 PM   #29
v-bro is offline v-bro  Netherlands
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after being satisfied with your eq-settings you may consider building a better filter(in which signal will make shorter routes) that gives the same result.

Eq's are built with ap-amps and aren't exactly audiophile devices, this is mostly not very audible with bass-frequencies though...

Just do some a/b testing....
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Old 21st September 2006, 07:17 PM   #30
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V-Bro

I went to school with a guy that hooked up a 2" speaker from a transistor radio to a fender bass guitar amp. When he hit the low string on his bass we found the Voicecoil stuck in the wall 30' away. LOL
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