I'm working on building a set of bookshelf speakers. I bought two 7" RS180-8 speakers, and just finished setting up REW to measure them. I built the impedence rig myself, and it seemed to work fine.
The one issue (maybe?) is that my parameters are quite a bit off from the published specs. I tested both speakers, and both are similar. But here are some rough deviations:
Left Speaker
Vas 14.85 litres
fs 49.4 Hz
Qts 0.464
Right Speaker
Vas 17.81 litres
fs 45.9 Hz
Qts 0.424
Published:
Vas 24.4 litres
Fs 35.7 Hz
Qts 0.31
Is it normal for the real measured parameters to be so far off? Anything I should look at adjusting?
My resistor measured 98.7 ohms, and I added about 70g of mass to the cone (which might be too much).
The drivers were fresh out of the boxes.
I'm using a USB Scarlet 6i6 sound interface.
Thanks.
The one issue (maybe?) is that my parameters are quite a bit off from the published specs. I tested both speakers, and both are similar. But here are some rough deviations:
Left Speaker
Vas 14.85 litres
fs 49.4 Hz
Qts 0.464
Right Speaker
Vas 17.81 litres
fs 45.9 Hz
Qts 0.424
Published:
Vas 24.4 litres
Fs 35.7 Hz
Qts 0.31
Is it normal for the real measured parameters to be so far off? Anything I should look at adjusting?
My resistor measured 98.7 ohms, and I added about 70g of mass to the cone (which might be too much).
The drivers were fresh out of the boxes.
I'm using a USB Scarlet 6i6 sound interface.
Thanks.
To be expected. T/S are vectors, the numbers we use are scalars collapsed from those curves. Where that collaps occurs can dramatically affectt he valiue of tghe parameters.
From experience i have found that working from factory numbers (if the factory is honest) gives a much more likely chance of nailing the box first time out.
The numbers you get from REW are useful for driver matching, i would noit use them for anything else.
dave
Ok. Because if I use my measured parameters, the boxes are significantly larger than using the PDF parameters. So you're saying I should just roll with the published parameters to make the enclosure?
That is what i have found. And Dayton, althou have a large range of quality, are pretyt good with their T/S data.
dave
dave
This is normal for new, not break in speakers.
fs is higher than published
Vas is smaller than published
Qts is higher than published
all they will be close to published values after break in.
fs is higher than published
Vas is smaller than published
Qts is higher than published
all they will be close to published values after break in.
Thanks.. So I have a remedial question - how does one break-in a speaker that isn't in a box or with a crossover? Just use the published values, and break it in later?
I am much gentler breaking in a driver as i do not want to impart a memory in the spider. The greater the bandwidth of the driver the more likliehood that memory will intrude (a supposition on my part).
Face up on a shelf, at least 200 hrs of low level FM input.
dave
Face up on a shelf, at least 200 hrs of low level FM input.
dave
Dave honestly, how can you spew complete utter nonsense like this ....
It's a disgrace man, to our serious exchanges with each other, about what matters ...
Cause seriously ???? Spider memory ??? heaven help me.....
Because it is not nonsense.
How tou break a driver in can affect its long term performance. Many recommended break-in procedures will actually “break” the driver.
dave
How tou break a driver in can affect its long term performance. Many recommended break-in procedures will actually “break” the driver.
dave
Recommended break-in procedures are themselves, by and large nonsense.....
so you've found a less non-sensical one?
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As a matter of interest, what tweeter will you be using please? There might be an existing project which documents the measurements you're after. To second post #4, Dayton's specs are generally regarded as accurate, compared to some nameless brands which can vary somewhat
Geoff
Geoff
Well I think it is a fact that when a new bass driver is excersised for a while, its Fs drops a hertz or two - it becomes softer end thus the change.
But the OP can forget about this if he is willing to use a poper EQ function for the system - if he does, he will ge in full control of the frequency response - just use a box size that is reasonably - check the Vas figure for the driver and it will get you a hint of a proper territory. Then tune to liking with EQ.
This will get you a lot better result in the end than thinking that a a few params will fix the design. This is the olden style design process which some are stuck in...
You can then safely also ignore hints of spider memory and other non critical aspects that is more or less dreamt up by vodo masters. It must not be mystic in order to be really good you know. But being able to tailor the final frequency response where you listen is really something that will matter.
There are streamer software with built in modern EQ functions like Volumio etc.
Good luck!!
//
But the OP can forget about this if he is willing to use a poper EQ function for the system - if he does, he will ge in full control of the frequency response - just use a box size that is reasonably - check the Vas figure for the driver and it will get you a hint of a proper territory. Then tune to liking with EQ.
This will get you a lot better result in the end than thinking that a a few params will fix the design. This is the olden style design process which some are stuck in...
You can then safely also ignore hints of spider memory and other non critical aspects that is more or less dreamt up by vodo masters. It must not be mystic in order to be really good you know. But being able to tailor the final frequency response where you listen is really something that will matter.
There are streamer software with built in modern EQ functions like Volumio etc.
Good luck!!
//
@duanestorey
There are posts (maybe here, but also at Parts Express Tech Talk) about break in. Some rules of thumb but also some tests measuring TS parameters after 3, 6, 12, 24, etc hours.
I run a sine wave at close to Fs, generating good excursion, overnight. I don't care if it's 6, 8 10 hours I just run it overnight because it's convenient to set it and go to bed.
I have a DATS v3 and would trust actual measurements over mfg specs, although hopefully they are close. Dayton and SB Acoustics (and some others) usually are reliable, some other brands are known to be not-so-reliable. Just like I trust actually measuring the mpg my actual car gets vs what mfg reports. (I have some HiVi F5 woofers that measure no-where-close to mfg specs. The were close out drivers that had probably been on a shelf for 5 years. I have a Toyota Hybrid that is supposed to get 36 mpg but gets closer to 31/32.)
There are posts (maybe here, but also at Parts Express Tech Talk) about break in. Some rules of thumb but also some tests measuring TS parameters after 3, 6, 12, 24, etc hours.
I run a sine wave at close to Fs, generating good excursion, overnight. I don't care if it's 6, 8 10 hours I just run it overnight because it's convenient to set it and go to bed.
I have a DATS v3 and would trust actual measurements over mfg specs, although hopefully they are close. Dayton and SB Acoustics (and some others) usually are reliable, some other brands are known to be not-so-reliable. Just like I trust actually measuring the mpg my actual car gets vs what mfg reports. (I have some HiVi F5 woofers that measure no-where-close to mfg specs. The were close out drivers that had probably been on a shelf for 5 years. I have a Toyota Hybrid that is supposed to get 36 mpg but gets closer to 31/32.)