It was very recently that I started studying speakers and the hi-fi scene. I read in an article recently that when it comes to a sealed midrange box, the QTC has to be between 0.5 and 0.7. So far so good, but when I put any example midrange in winISD the internal volume of the box is very low... around 3 liters and I've seen examples on this forum of boxes with a volume of 7 liters. Midrange 4"
Attachments
So a 4" speaker with .2 Qts
will be a smaller box
Than a 4" speaker with .5 Qts
So its not a wild guess based on piston diameter.
It is based on the speakers mechanical and electrical properties
To align it to a filter.
Which is what the theory is based on.
The speaker response is aligned to the equivalent
of a filter response.
Hence .5 Qtc is equivalent of a filter with .5 cutoff Q
.707 is = .707 filter cutoff Q etc etc.
---------------------------------
Speakers have mechanical and electrical properties.
Qms( mechanical Q ) Qes ( electrical Q )
Qts uses both those to
determine Qts ( total Q )
It represents the combination of electrical
and mechanical properties of a speaker.
So drivers with low Qts will generally
need a smaller box
and high Qts will tend to be larger.
So it is what is nice about math
or known formulas that work for speaker
performance.
--------------------------------
No wild guessing needed
Maybe this, maybe that?
You just calculate .5 to .7 Qtc
And that is what it is for.
To determine box volume needed.
for that specific driver
According to its suspension ( mechanical )
and its magnet ( electrical )
So no wild guessing.
The suspension is either so loose or so tight.
And the magnet so powerful.
The majority of box size is making the suspension
happy.
will be a smaller box
Than a 4" speaker with .5 Qts
So its not a wild guess based on piston diameter.
It is based on the speakers mechanical and electrical properties
To align it to a filter.
Which is what the theory is based on.
The speaker response is aligned to the equivalent
of a filter response.
Hence .5 Qtc is equivalent of a filter with .5 cutoff Q
.707 is = .707 filter cutoff Q etc etc.
---------------------------------
Speakers have mechanical and electrical properties.
Qms( mechanical Q ) Qes ( electrical Q )
Qts uses both those to
determine Qts ( total Q )
It represents the combination of electrical
and mechanical properties of a speaker.
So drivers with low Qts will generally
need a smaller box
and high Qts will tend to be larger.
So it is what is nice about math
or known formulas that work for speaker
performance.
--------------------------------
No wild guessing needed
Maybe this, maybe that?
You just calculate .5 to .7 Qtc
And that is what it is for.
To determine box volume needed.
for that specific driver
According to its suspension ( mechanical )
and its magnet ( electrical )
So no wild guessing.
The suspension is either so loose or so tight.
And the magnet so powerful.
The majority of box size is making the suspension
happy.
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Some 4" speakers
or many these days try to get "more bass".
So sensitivity will drop
And mechanical properties
change to make more bass.
For a mid only driver.
Your not to worried about bass.
Your more interested in sensitivity
and mid/ high frequency performance.
less distortion/ cone breakup etc etc
Drivers that make " more bass"
generalized will have a heavier cone
and loose surround.
So heavy cone and deeper shapes in general will
have more cone breakup at high frequency.
So good mid can disregard making " more bass"
and be lighter and stiffer for better high-end.
Very generalized
but notable after reviewing hundreds
of drivers
and certain parameters will clue in quickly
what it is designed to do.
Or actual visible mechanical design.
Surround/ cone
likewise since a mid is on a crossover.
your not to worried about the box being.
" big enough" cause bass response is not
the concern below the crossover point.
Obviously a mid crossed at 300 Hz compared
to 600 Hz. likely make the box bigger for
lower frequency
or many these days try to get "more bass".
So sensitivity will drop
And mechanical properties
change to make more bass.
For a mid only driver.
Your not to worried about bass.
Your more interested in sensitivity
and mid/ high frequency performance.
less distortion/ cone breakup etc etc
Drivers that make " more bass"
generalized will have a heavier cone
and loose surround.
So heavy cone and deeper shapes in general will
have more cone breakup at high frequency.
So good mid can disregard making " more bass"
and be lighter and stiffer for better high-end.
Very generalized
but notable after reviewing hundreds
of drivers
and certain parameters will clue in quickly
what it is designed to do.
Or actual visible mechanical design.
Surround/ cone
likewise since a mid is on a crossover.
your not to worried about the box being.
" big enough" cause bass response is not
the concern below the crossover point.
Obviously a mid crossed at 300 Hz compared
to 600 Hz. likely make the box bigger for
lower frequency
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There is no parameters or recommendations for " stuffing"
in WinIsd.
But you can model it slightly by changing
advanced parameters for absorption losses.
= Qa
Qa of 100 is no losses or no absorption
Qa of 30 to 40 is likely achievable
in real life. meaning stuffed the krap out of it.
Qa of 80 ish is about a lined box
Absorption material helps more for midrange frequencies
in the first place. Below certain wavelengths
it dont do much.
But good point regardless.
Mid box is not to complicated.
.5 to .8 Qtc is fine
Then basically stuff the krap out of it regardless.
All done.
you wanna push that to .9 or even 1.2 Qtc
Aka a very small box. Same thing
stuff the krap out of it regardless.
Parallel walls aka a box, or two straight walls.
Can have more resonance.
But that is why you have absorption material.
Not much energy in high frequency
so absorption gets rid of resonance peaks very easily.
But you can make it more " magical"
by reducing the chance of resonance
by making the walls, not parallel.
Hence triangle, trapezoid, spiral
or any other magical shape with
no parallel walls.
Aka= sounds good but you just stuff it
and they go away regardless.
Non parrallel walls is slightly more helpful
for bass resonance since the absorption material
is not very effective at lower frequency.
in WinIsd.
But you can model it slightly by changing
advanced parameters for absorption losses.
= Qa
Qa of 100 is no losses or no absorption
Qa of 30 to 40 is likely achievable
in real life. meaning stuffed the krap out of it.
Qa of 80 ish is about a lined box
Absorption material helps more for midrange frequencies
in the first place. Below certain wavelengths
it dont do much.
But good point regardless.
Mid box is not to complicated.
.5 to .8 Qtc is fine
Then basically stuff the krap out of it regardless.
All done.
you wanna push that to .9 or even 1.2 Qtc
Aka a very small box. Same thing
stuff the krap out of it regardless.
Parallel walls aka a box, or two straight walls.
Can have more resonance.
But that is why you have absorption material.
Not much energy in high frequency
so absorption gets rid of resonance peaks very easily.
But you can make it more " magical"
by reducing the chance of resonance
by making the walls, not parallel.
Hence triangle, trapezoid, spiral
or any other magical shape with
no parallel walls.
Aka= sounds good but you just stuff it
and they go away regardless.
Non parrallel walls is slightly more helpful
for bass resonance since the absorption material
is not very effective at lower frequency.
"There is no parameters or recommendations for " stuffing"
in WinIsd." Maybe go read the help file. And you can get a Qa down to 3 very easily.
Stuffing is modeled with Qa, absorption losses. Just as it says in the help file text reproduced below:
Designing your Box (a.k.a. Designing your Project)
Under "advanced->", you can find controls for box losses. There, you can see what effect the each loss type will have on your box design (Smaller the value, greater the loss). There are three types of losses:
in WinIsd." Maybe go read the help file. And you can get a Qa down to 3 very easily.
Stuffing is modeled with Qa, absorption losses. Just as it says in the help file text reproduced below:
Designing your Box (a.k.a. Designing your Project)
Under "advanced->", you can find controls for box losses. There, you can see what effect the each loss type will have on your box design (Smaller the value, greater the loss). There are three types of losses:
- Ql, leakage losses. These are produced by leaks in enclosure or in driver itself. Generally, this is most dominant loss type in vented boxes. Typical value is 5-20. This is quite impossible to predict before building the actual box. For reasonable quality box, WinISD pro uses Ql of 10 by default.
- Qa, absorption losses. These are produced by losses in enclosure. Any stuffing will increase the absorption loss. With no stuffing inside the box, 100 is typical. Heavily stuffed enclosure has this about 3-5.
- Qp, port losses. These are produced by port. Port has some resistance (air doesn't actually flow through the port without some friction). Actually, by setting this into very small value, you can turn vented box into closed one!
I know what Qa is hence why I wrote it.
And as mentioned earlier.
magnet is so big, suspension is so loose or tight.
.5 to .8 Qtc is more than fine.
if you wanna make it smaller
.9 to 1.2
then yes your stuffing the krap out if it
no matter what.
Obviously if your crossing at 100 Hz
compared to 600 Hz
Then making the box small is relatively
a poor decision for low crossover.
Fs rises in the box
and crossover is at least 2x over Fsc
so that is basically all you need to know.
The impedance curve.
Which " stuffing" doesn't change the frequency.
It will lower the impedance peak.
No magic. the suspension is so loose so tight.
so the box is this big.
Increasing Qa wont change Fsc
in WinIsd
It will just show the impedance peak changing value
in ohms.
So your stuffing it silly regardless.
All you care about is what volume to use.
Modeling Qa for midrange is pretty meaning less.
Because crossover is 2x over the Fsc or higher
regardless.
Whatever reflections hit the cone in real life at high frequency.
Is non existent, because you stuffed it.
Low frequency is the issue for magical chamber shapes.
So if you crossed say 100 Hz then ok cool
make the mid chamber some magical shape.
to feel better, it does what it does regardless.
And as mentioned earlier.
magnet is so big, suspension is so loose or tight.
.5 to .8 Qtc is more than fine.
if you wanna make it smaller
.9 to 1.2
then yes your stuffing the krap out if it
no matter what.
Obviously if your crossing at 100 Hz
compared to 600 Hz
Then making the box small is relatively
a poor decision for low crossover.
Fs rises in the box
and crossover is at least 2x over Fsc
so that is basically all you need to know.
The impedance curve.
Which " stuffing" doesn't change the frequency.
It will lower the impedance peak.
No magic. the suspension is so loose so tight.
so the box is this big.
Increasing Qa wont change Fsc
in WinIsd
It will just show the impedance peak changing value
in ohms.
So your stuffing it silly regardless.
All you care about is what volume to use.
Modeling Qa for midrange is pretty meaning less.
Because crossover is 2x over the Fsc or higher
regardless.
Whatever reflections hit the cone in real life at high frequency.
Is non existent, because you stuffed it.
Low frequency is the issue for magical chamber shapes.
So if you crossed say 100 Hz then ok cool
make the mid chamber some magical shape.
to feel better, it does what it does regardless.
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The article is incorrect. As mentioned above a midrange driver does not normally want to use a cabinet resonance to extend the low frequency response given the low frequency is normally then reduced in the crossover to the woofer. There is a price to pay in terms of a degraded transient response which is best avoided. A midrange enclosure is normally designed to be reasonably large and adequately stuffed so that the rear sound radiation is as fully absorbed as possible.
I imagined that... I'll have to know how much padding to put in order to know the perfect size of the box, wiISD didn't calculate this, giving me a box with the size without padding
I found graphs on the internet to help me study... From the graphs I have and from what I read, it would cross with the crossover at 350hz
It's not my theory or even really a theory but normal practise/understanding and I would expect it to be mentioned/assumed in most competent DIY speaker textbooks. Given the cabinet loading is effectively irrelevant I doubt you will find articles on the topic. What you may find are various studies looking at the effectiveness of various midrange stuffing strategies and possibly a bit on cavity shape. Unfortunately home audio is full of nonsense articles claiming all sorts of nonsensical things and so you are almost certainly going to come across a fair few of these as well.
An up to date reliable text on speaker DIY is a good question and I am not sure I have an answer. Anyone? The 50-60 year old basic texts I used have many relevant omissions due to how designing and manufacturing speakers has evolved.
The good news is that a midrange cabinet is not critical to performance. So long as it is big enough and contains a reasonable amount of stuffing it should be fine. Issues may arise if there isn't enough space behind the midrange driver but this tends to be rare given 3+ way speakers tend to be large.
A 4" midrange crossed around 350 Hz is a common configuration and so a quick look at good quality commercial and DIY designs using something like this should give you a good idea of what tends to be done in practise. Again, be aware that there is a lot of nonsense and marketing out there so take care with unusual designs.
Hello.
The QTC for a driver in a sealed enclosure is much more important for a woofer than a mid-range speaker.
The largest reason for the mid-range sealed enclosure is to keep the woofer pressures away from the back of the mid-range driver.
No worries the mid-range cross over frequency will be well above the resonate frequency of the mid-range speaker.
Thanks DT
The QTC for a driver in a sealed enclosure is much more important for a woofer than a mid-range speaker.
The largest reason for the mid-range sealed enclosure is to keep the woofer pressures away from the back of the mid-range driver.
No worries the mid-range cross over frequency will be well above the resonate frequency of the mid-range speaker.
Thanks DT