Hi,
I was wondering if anybody had worked through the' Loudspeaker Modelling & Design' book by Geoff Hill. I've been using it as a guide to look at driver design, specifically subdrivers, but I seem to be coming across a lot of errors in the math & modelling.
Has anyone else encountered this and been left similarly stumped?
Thanks,
I was wondering if anybody had worked through the' Loudspeaker Modelling & Design' book by Geoff Hill. I've been using it as a guide to look at driver design, specifically subdrivers, but I seem to be coming across a lot of errors in the math & modelling.
Has anyone else encountered this and been left similarly stumped?
Thanks,
I hadn’t run into that book before. I have run into his tetrahedral test chamber. The guy is very experienced, but without seeing some of the stuff i know well i do not know how well he covers stuff.
From the ToC it is quite comprehesive and it looks like it is targeted at practical matters.
But every text has its own biases, and the field does have significant “general knowledge” that proves to be not so solid.
So, based on little, it looks to be a good guide, but you do need to do complementary research to try to dig up the biases.
Can you give some examples of things made using this as a guide, and perhaps a page or 2 of the box construction parts for me to get a better idea of wher ehe has been.
Do note that there are lots of people around here with 40 or more years of experience.
dave
From the ToC it is quite comprehesive and it looks like it is targeted at practical matters.
But every text has its own biases, and the field does have significant “general knowledge” that proves to be not so solid.
So, based on little, it looks to be a good guide, but you do need to do complementary research to try to dig up the biases.
Can you give some examples of things made using this as a guide, and perhaps a page or 2 of the box construction parts for me to get a better idea of wher ehe has been.
Do note that there are lots of people around here with 40 or more years of experience.
dave
Yeah, there's lots of good theory in the book and some software walkthroughs are very helpful. However, a lot of the modelling seems off, as in the results in the book differ from the results I have obtained following the same steps. It's quite hard to show as there's a fair bit of working involved. But I wondered if there was anyone else who'd encountered similar issues as me.
It's mainly the driver design where I've encountered some things that don't make sense
for example here when describing coil winding.
"If we use 0.575mm copper wire in a 4-layer with a 32mm wind length using a 75mm Inner diameter giving a DCR of 3.46 ohms, this has 208 turns and the
outer diameter 77.5 mm."
So the inner dimension is said to be 75mm and outer 77.5mm. The difference being 4*wire diameter(0.575mm) + 2*former(0.1mm). However should the difference not be 8*wire diameter + 2*former. This is as the wire is extending the diameter by twice its thickness for each turn? So the outer diameter would be 79.8mm.
Potentially a fairly innocuous mistake but it's carried on in the workings for modelling throughout the book
It's mainly the driver design where I've encountered some things that don't make sense
for example here when describing coil winding.
"If we use 0.575mm copper wire in a 4-layer with a 32mm wind length using a 75mm Inner diameter giving a DCR of 3.46 ohms, this has 208 turns and the
outer diameter 77.5 mm."
So the inner dimension is said to be 75mm and outer 77.5mm. The difference being 4*wire diameter(0.575mm) + 2*former(0.1mm). However should the difference not be 8*wire diameter + 2*former. This is as the wire is extending the diameter by twice its thickness for each turn? So the outer diameter would be 79.8mm.
Potentially a fairly innocuous mistake but it's carried on in the workings for modelling throughout the book
Looks like he uses Windoz so not much use to me.
Loudspeaker design has a huge number of degrees of freedom. I don’t pay much attention to the VC detail you outline, in the end how does the whole work?
dave
Hello, I am currently reading the book and am trying to use it as a guide, but I have some problems understanding it:
On page 89 it is summarized that you already have the following variables:
Fs=38Hz,Bl=25Tm,Re=3.5ohms,Mms=300gm,Sd=310cm2,Xmax=25mm,and−3dB=27Hz.
A few chapters earlier it is shown how to use the box volume and a spreadsheet to arrive at 38 Hz for the resonant frequency. However, despite reading it several times, I do not understand where the 27Hz for the -3DB frequency suddenly came from. I thought that it might be the desired value, but before that 20Hz is always spoken of and never 27Hz. Just as little I don't understand where the 25mm Xmax come from. Xmax is briefly explained but somehow not where this value comes from or how exactly it was calculated.
Is anyone able to help me ? Otherwise, the book is really helpful.
On page 89 it is summarized that you already have the following variables:
Fs=38Hz,Bl=25Tm,Re=3.5ohms,Mms=300gm,Sd=310cm2,Xmax=25mm,and−3dB=27Hz.
A few chapters earlier it is shown how to use the box volume and a spreadsheet to arrive at 38 Hz for the resonant frequency. However, despite reading it several times, I do not understand where the 27Hz for the -3DB frequency suddenly came from. I thought that it might be the desired value, but before that 20Hz is always spoken of and never 27Hz. Just as little I don't understand where the 25mm Xmax come from. Xmax is briefly explained but somehow not where this value comes from or how exactly it was calculated.
Is anyone able to help me ? Otherwise, the book is really helpful.
I have not read the book, but in case it helps, Xmax can mean different things - it could be maximum travel distance while keeping the voice coil in the magnetic field (xmax lin), or it could be the mechanical limits of the suspension or when the voice coil former hits the back of the motor plate (xmax mech). Both can be written as one direction only, or both directions e.g. 10mm or +/-10mm = 20mm pk-pk.
Thank you, it's definitely a helpful addition ! 🙂
but I still can't get any further with the book 😀
Where exactly the -3dB point occurs (not a figure of merit for humans), is not often the box resonance.
dave
dave
I know but it doesn't explain how he got that value. The 38 Hz resonant frequency is explained but the 27 Hz for the -3DB frequency suddenly just shows up. How do you get that? This is not so obvious, especially for a beginner. Maybe someone can help me
Most of us just use a simulation program like WinISD to do the heavy lifting with maths. With that general overview you will probably see how the number was found.
However if you want to know how to calculate frequency response curves from T/S/ parameters I would say it's probably not very easy and beyond most of us who have broader interests than only physics.