I see... I think! So the higher the FS the less it will attempt to play lower frequencies? So a 40hz fs driver will try to play more at 20hz than a driver with an fs of 50hz?
edit: I don't mean to be a pain, but your post was ever so slightly mysterious to me! Do you mean low frequencies are less important because they won't be audible anyway, or do you mean that very low frequencies won't be 'seen' by the driver?
edit: I don't mean to be a pain, but your post was ever so slightly mysterious to me! Do you mean low frequencies are less important because they won't be audible anyway, or do you mean that very low frequencies won't be 'seen' by the driver?
Vikash said:I haven't got round to doing any baffle step calculations, but for some reason I was under the impressions that the bass units would need to go up to 700+Hz. Why does the 200 work better with respect to compensating for BS (than 300)? Crossover design and BSC is new to me, so bear with me
Hmm, OK here goes. With a midrange driver you can compensate for baffle step increasing the "Q" of the highpass. This essentially boosts back the loss of BS on the mid. Thus your mid sensativity is still at the standard sens as quoted by the manufacture. Your 85dB mid is still running at 85dB, rather then 89 after a normal BS comp circuit. Usually you attenuate the higher frequecies by the 6dB step response to get flat.
Here you leave the high freqs alone and give boost to the lower midrange to compensate for BS.
So now that your mids have been adjusted you need to sort out the bass.
Because the bass is two drivers in parallel you end up having 6dB more then a single driver. This works out well, because the two bass drivers will be 6dB down AFTER complete baffle step has occured, which is at about 200hz in a 15cm wide baffle.
The mid driver is working at stock sensativity 85dB, and the bass are wired in parallel giving 91dB, but because of bafflestep the bass below 200hz are at 85dB, crossing at 200 works sensativity wise.
Hope that makes sense.
SimontY said:
I think you've got the basics.
For a given excursion capability extending bass reduces power
handling which can be "fixed" with more drivers, in this case
this would only apply if you had active bass boost, such that
having more than 4 drivers would be needed for low bass.
Like I said 4 drivers is a sensible limit for bass where you
are accepting a subwoofer is needed for geniune low bass.
🙂 sreten.
Since 4 bass drivers are reccomended I have come up with the following design.
I am thinking it best to wire the top two and bottom two woofers in series with respective paired driver, and then each pair wired in parallel which will give an overall 6ohm impedance.
I imagine it best to wire the drivers facing the same direction...any reason otherwise?
For the tweeter, should it be placed off center? Physically it will be at ear height.
Also which would you reccomend...Audax TM025F1 (70w round dome), TM025M0 (55w round dome - resonance freq. 900Hz) or TW025A0 (55w round aluminium dome - resonance freq. 1090.5Hz).
As far as crossover design I'm a little bit confused about which to go for...1st order Butterworths for bass, 2nd order Linkwitz-Riley for mid/tweet?
(I've tried reading up on the different types but at the moment it's more confusing than helpful).
And finally...I plan on using a subwoofer (quite fancy a stereo pairing of a TL tubular design using a Peerless 850136) to help out the bottom end, although this won't be for a while yet. What would you reccomend as a crossover frequency for bass/mid | mid/tweet?
I was thinking 500 and 4000 but that's just for some unknown reason that sounded good and there's no real justification of why.
Thanks for all the help.
An externally hosted image should be here but it was not working when we last tested it.
I am thinking it best to wire the top two and bottom two woofers in series with respective paired driver, and then each pair wired in parallel which will give an overall 6ohm impedance.
I imagine it best to wire the drivers facing the same direction...any reason otherwise?
For the tweeter, should it be placed off center? Physically it will be at ear height.
Also which would you reccomend...Audax TM025F1 (70w round dome), TM025M0 (55w round dome - resonance freq. 900Hz) or TW025A0 (55w round aluminium dome - resonance freq. 1090.5Hz).
As far as crossover design I'm a little bit confused about which to go for...1st order Butterworths for bass, 2nd order Linkwitz-Riley for mid/tweet?
(I've tried reading up on the different types but at the moment it's more confusing than helpful).
And finally...I plan on using a subwoofer (quite fancy a stereo pairing of a TL tubular design using a Peerless 850136) to help out the bottom end, although this won't be for a while yet. What would you reccomend as a crossover frequency for bass/mid | mid/tweet?
I was thinking 500 and 4000 but that's just for some unknown reason that sounded good and there's no real justification of why.
Thanks for all the help.
After a quick read around trying to figure things out it seems that a crossover in the 'voice' range (300-3400Hz) isn't a good idea..
...so..how does a 1st order Butterworth for bass, and 2nd order Linkwitz-Riley for mid/tweet sound with 300Hz and 4800Hz cross over points?
...so..how does a 1st order Butterworth for bass, and 2nd order Linkwitz-Riley for mid/tweet sound with 300Hz and 4800Hz cross over points?
nubbins said:
Yes, thats a good general principle, but like others, can be bent once you understand the rules.
Unfortunately it's not really that simple. You need to either measure the drivers in the final box or use simulation software to design crosssovers if they are to work accurately and sum flat. You can't really just pick a topology off the shelf, or one used for another speaker and hope it will work.
nubbins said:
The 4 outside bass drivers should be wired in series parallel,
the two midrange drivers in series, this will give you BSC with
the correct c/o frequency, 6 ohm bass, 12 ohm midrange.
(as previously mentioned)
There's mileage in mounting the two rear bass drivers
magnet out, for push pull 2nd harmonic cancellation,
use an inset rear baffle, the T construction adds rigidity.
There's mileage in moving the top two bass drivers to the bottom
to give you a MTBB baffle, it also makes closing off the mids with
an added section easier and reduces overall speaker hieght.
Mirrored offset tweeters are always a good idea.
🙂 sreten.
is this just in this application or generally.
If this is a good idea for all louspeaker designs are there any prefered ratio's or ways to calculate exactly where the driver should be situated relative to the other drivers?
mark
There is no exact methodology IMO, but also IMO a simple offset
is easy to include and is likely to improve matters with no downside.
Golden ratios can be used to determine "ideal" position.
For an MTM a position at ~ 60% of baffle width is reasonable.
🙂 sreten.
is easy to include and is likely to improve matters with no downside.
Golden ratios can be used to determine "ideal" position.
For an MTM a position at ~ 60% of baffle width is reasonable.
🙂 sreten.
Well, the crossover components from Audiocom finaly turned up today, so I will hopefuly get a chance to wire up one speker (still in cardboard box) and have a bit of a listen tonight and see if £20' worth of drivers, one cardboard box, and 10uF cam and a 0.15mH inductor actualy make any sort of noise at all.
Looking forward to your results BP.
I asked this on the chip amps forum with no reply so I'll ask again here since it's related: If I want to use active crossovers what would be the best way to go about it? Are there any problems with using one psu (per enclosure) and three chips (one each for mid, bass and tweet duties) running off it?
I asked this on the chip amps forum with no reply so I'll ask again here since it's related: If I want to use active crossovers what would be the best way to go about it? Are there any problems with using one psu (per enclosure) and three chips (one each for mid, bass and tweet duties) running off it?
I doubt there would be any problems running a chip amp (or three) off the same powere transformer if it was for use in one speaker. As these things have amazing PSRR values and the mid and tweeter amps will probably have very little effect on the supply (even the bass will be fairly limmited).
So, if I were you I would just go ahead and try it using the one transformer and rectifier, but still with the seperate decoupling caps at the chips power supply pins.
So, if I were you I would just go ahead and try it using the one transformer and rectifier, but still with the seperate decoupling caps at the chips power supply pins.
One PSU per enclosure should be fine, and would be the way I would do it if I was incorporating everything into the box.
At first there seems an issue with overspecifying the PSU VA because you run all drive units off the same rails. However, in practice, because the mid and tweeter are attenuated they draw less power so the VA can be reduced accordingly.
At first there seems an issue with overspecifying the PSU VA because you run all drive units off the same rails. However, in practice, because the mid and tweeter are attenuated they draw less power so the VA can be reduced accordingly.
Into this:
As you may guess it's a bit difficult to properly judge how a single speaker in a cardboard box sounds. However, it does show signs of potential, as it easily outperforms my existing speakers when playing back acoustic guitar or female vocals. It's a bit week in the bass department at the moment, but I'm guessing this will improve as the driver bedds in and when it get's its propper vented enclosure. The other thing which would appear to need tweeking a bit at the moment is the tweeter, which I think still needa a little more attenuation (currently 2.5 ohms in line with the nominaly four ohm tweeter) to match the level of the two mid/bass units a little better.
But other than that, it sounds a lot better than £28 of components in a cardboard box hava an right too, and I am looking forward to see just what can be sqeezed out of these drivers (and possibly even get two the same for some propper listening), just have to see how friendly the guys in the engineering deparment are with regards to cutting me up some MDF...
As you may guess it's a bit difficult to properly judge how a single speaker in a cardboard box sounds. However, it does show signs of potential, as it easily outperforms my existing speakers when playing back acoustic guitar or female vocals. It's a bit week in the bass department at the moment, but I'm guessing this will improve as the driver bedds in and when it get's its propper vented enclosure. The other thing which would appear to need tweeking a bit at the moment is the tweeter, which I think still needa a little more attenuation (currently 2.5 ohms in line with the nominaly four ohm tweeter) to match the level of the two mid/bass units a little better.
But other than that, it sounds a lot better than £28 of components in a cardboard box hava an right too, and I am looking forward to see just what can be sqeezed out of these drivers (and possibly even get two the same for some propper listening), just have to see how friendly the guys in the engineering deparment are with regards to cutting me up some MDF...
Attachments
I think I may have discovered the reason for the harshness in the speaker. I designed the crossover assuming a 1 ohm resistor being used to attenuate the tweeter when I ordered the components, and then realised I needed about 2.3 for propper attenuation. So, the axtra 1.5 ohms I ahev in there at the moment means the tweeter is comming in at 2500Hz, and the mids not being taken out untill 3200Hz.
oops.
oops.
I've been messing about with a redesign of the speaker I was thinking about.
The image shows the MTMBB with the mids wired in series (12ohm) and the 4 bass drivers in a series/parallel configuration (6ohm). In the image it's kinda setup for the 4 bass drivers facing the same direction with the two in the rear mounted on an internal baffle.
Internal space is 4266cm³ (4.3litre) for the midrange area, and 8880cm³ (8.9litre) for the area occupied by the bass drivers and the space behind the midrange enclosure.
A few Q's. 😉
Do I have enough internal area with which to work in?
What about mounting the rear bass drivers in flush against the rear wall in a bipole setup?
How on earth do I go about creating a crossover now? 😀
Cheers y'all
An externally hosted image should be here but it was not working when we last tested it.
The image shows the MTMBB with the mids wired in series (12ohm) and the 4 bass drivers in a series/parallel configuration (6ohm). In the image it's kinda setup for the 4 bass drivers facing the same direction with the two in the rear mounted on an internal baffle.
Internal space is 4266cm³ (4.3litre) for the midrange area, and 8880cm³ (8.9litre) for the area occupied by the bass drivers and the space behind the midrange enclosure.
A few Q's. 😉
Do I have enough internal area with which to work in?
What about mounting the rear bass drivers in flush against the rear wall in a bipole setup?
How on earth do I go about creating a crossover now? 😀
Cheers y'all
I see you have the essential audiophile ingredients BP!
Wine
DIY Speakers
Randy Slone's Book
Well done on the test setup - I'm following with interest! 🙂
Gaz
Wine
DIY Speakers
Randy Slone's Book
Well done on the test setup - I'm following with interest! 🙂
Gaz
nubbins said:
You should mount the rear drivers to the rear baffle, with holes
in the centre "baffle" to allow airflow between the sections.
As its a 3-way 4 litres for the mids sounds about right but you
should extend the total hieght for a floor stander with the top
mid at ear level and target something like 3/3.5L per bass driver.
🙂 sreten.
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