Hi,
I'm new to the forums, so forgive me if I'm asking a tired old question...
I'm considering building a two-way passive cross-over loudspeaker using a single tweeter and two bass drivers in parallel. My thinking being two drivers will produce more sound. Is this correct, or because I'm splitting the current to the base units am I only just getting half the output from each of the two speakers? My hope is that by doubling up on the base drivers I can match the higher efficiency of the tweeter.
Make sense?
Thanks in advance!
A
I'm new to the forums, so forgive me if I'm asking a tired old question...
I'm considering building a two-way passive cross-over loudspeaker using a single tweeter and two bass drivers in parallel. My thinking being two drivers will produce more sound. Is this correct, or because I'm splitting the current to the base units am I only just getting half the output from each of the two speakers? My hope is that by doubling up on the base drivers I can match the higher efficiency of the tweeter.
Make sense?
Thanks in advance!
A
Hi, two drivers are going to sound louder you're right: you are doubling emiting surface area so you gain +3db, and if wired in paralel (// eg:2x8 ohm speaker units in // equal 4 ohm load for amplifier) you are halving resistance so for same Voltage as for 8 ohm single unit you are also gaining 3db with 2 units in //. Overall you gain 6db which is double the perceived volume.
BUT this is not so simple... as layout and driver placement or design choice can counteract or differ from the simple definition given.
For example d'appolito configuration (aka MTM or WTW which is vertical placement of tweeter in between two woofer will give you 'more sound' but you'll be constrained to driver placement and centre to centre distance depending on filter cut off). Lateral placement can be used too but you'll need to check if directivity is coherent between your woofers and tweeters... and if you decide to go 2.5 way you won't have doubling of SPL (sound pressure level) until you reach freq of BSC (baffle step compensation)....
Many choices possible, all a compromise... Very complicated to understand at first but with experience you'll learn. By the way if this is your first project just go for a design which is known to work. Starting from scratch can be very deceptive in the end: so many things to understand and take into account...
And... welcome to this wonderful place! Full of knowledge and good people!
BUT this is not so simple... as layout and driver placement or design choice can counteract or differ from the simple definition given.
For example d'appolito configuration (aka MTM or WTW which is vertical placement of tweeter in between two woofer will give you 'more sound' but you'll be constrained to driver placement and centre to centre distance depending on filter cut off). Lateral placement can be used too but you'll need to check if directivity is coherent between your woofers and tweeters... and if you decide to go 2.5 way you won't have doubling of SPL (sound pressure level) until you reach freq of BSC (baffle step compensation)....
Many choices possible, all a compromise... Very complicated to understand at first but with experience you'll learn. By the way if this is your first project just go for a design which is known to work. Starting from scratch can be very deceptive in the end: so many things to understand and take into account...
And... welcome to this wonderful place! Full of knowledge and good people!
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Krivium,
Thank you! Merci!
This is wonderful help! I had initially thought of putting the woofers vertically and below the tweeter - I've seen similar arrangement of a passive radiator/woofer in an old Phillips book... I thought since both woofers are producing the very same sounds there would be no interference - as with tweeters near crossover... I'm not familiar with "2.5 way" or "baffle step compensation" - where can I find more about those?
And yeah, I've done a few of these now. Started with a couple different bass reflex 3-ways, but I'm liking simple 2-ways more now I'm more comfortable with crossover design. I'm wanting to bring the base UP with this new one instead of attenuating the tweeter. That just seems like a waste. And I've got a little bigger room to fill but don't want to use big woofers...
Anyway, thanks again!
A
Thank you! Merci!
This is wonderful help! I had initially thought of putting the woofers vertically and below the tweeter - I've seen similar arrangement of a passive radiator/woofer in an old Phillips book... I thought since both woofers are producing the very same sounds there would be no interference - as with tweeters near crossover... I'm not familiar with "2.5 way" or "baffle step compensation" - where can I find more about those?
And yeah, I've done a few of these now. Started with a couple different bass reflex 3-ways, but I'm liking simple 2-ways more now I'm more comfortable with crossover design. I'm wanting to bring the base UP with this new one instead of attenuating the tweeter. That just seems like a waste. And I've got a little bigger room to fill but don't want to use big woofers...
Anyway, thanks again!
A
Hi,
What you say is basically true, but reality is much more complicated.
Speaker kits, loudspeaker design services, sub-woofers and amplifiers. - X-Series kits
is good for a first build.
rgds, sreten.
What you say is basically true, but reality is much more complicated.
Speaker kits, loudspeaker design services, sub-woofers and amplifiers. - X-Series kits
is good for a first build.
rgds, sreten.
2.5way as stated is a good way to go. It doesn't bring the sensitivity up to match the tweeter, but brings freq below the baffle step up. If you then wanted to go up another notch you'd probably have to go with 4 woofers, but then there's the issue of having them close enough for the freq you want them to cover up to until you cross to the tweeter.
It certainly makes you appreciate high sensitivity woofers and why some aim for quite large mid-woofers, not to mention tweeters that can be crossed over quite low.
It certainly makes you appreciate high sensitivity woofers and why some aim for quite large mid-woofers, not to mention tweeters that can be crossed over quite low.
I'm pleased if it helps, but it's just scratching over the surface of a good working loudspeaker design which seems a quite complicated thing for me.
Well for BSC:
https://www.trueaudio.com/st_diff1.htm
and
Baffle Step Compensation
As mentionned in the Rod Elliott article this is a parameter which depend highly of room and position of loudspeakers.It is related to physical dimension en geometry of box too... So tweaking the filter is needed once all woodwork is finished...and you must have this in mind designing the filter.
2.5 ways is basically a 2 way with an added woofer low pass filtered to compensate for this bsc effect. It works but for what i've experienced you need a big room for optimum results (some may differ).
Here is a pdf about physical location of woofer/tweeter and different layout and polar diagram resulting from.This is a study based on different Kinoshita's RM series and TAD exclusive series lphisical layout (2402,2401,...) Just keep in mind that this is horn with 90° horizontal x 40° vertical -6db for tweeter. Target in THIS PARTICULAR EXEMPLE is 90° horizontal. With a dome tweeter behavior is different as is bandwith: th4001 is designed to be used crossed at 640hz/480hz absolut minimum... compared to 2000hz/1500hz made huge difference concerning centre to center distance. And sorry it's in french...but i think the pictures speak enough to be understood. If not i can translate some things (in my poor english).
http://jimmy.thomas.free.fr/temp/DI-BOOMER-TH4001.pdf
Well for BSC:
https://www.trueaudio.com/st_diff1.htm
and
Baffle Step Compensation
As mentionned in the Rod Elliott article this is a parameter which depend highly of room and position of loudspeakers.It is related to physical dimension en geometry of box too... So tweaking the filter is needed once all woodwork is finished...and you must have this in mind designing the filter.
2.5 ways is basically a 2 way with an added woofer low pass filtered to compensate for this bsc effect. It works but for what i've experienced you need a big room for optimum results (some may differ).
Here is a pdf about physical location of woofer/tweeter and different layout and polar diagram resulting from.This is a study based on different Kinoshita's RM series and TAD exclusive series lphisical layout (2402,2401,...) Just keep in mind that this is horn with 90° horizontal x 40° vertical -6db for tweeter. Target in THIS PARTICULAR EXEMPLE is 90° horizontal. With a dome tweeter behavior is different as is bandwith: th4001 is designed to be used crossed at 640hz/480hz absolut minimum... compared to 2000hz/1500hz made huge difference concerning centre to center distance. And sorry it's in french...but i think the pictures speak enough to be understood. If not i can translate some things (in my poor english).
http://jimmy.thomas.free.fr/temp/DI-BOOMER-TH4001.pdf
And SPL is not the only parameter to take into account: having a tweeter with a pad means headroom to me and headroom is a great feature for me ... which can be seen as a waste for others.
Having two woofer as another advantage than max SPL for me: less distortion.
Why? Because much less movement is needed for each speakers for a given spl. And for woofer movement=distortion.
Same thing with BSC: using an attenuating high shelf=headroom=less distortion For some this is a waste of db... different point of view.
Having two woofer as another advantage than max SPL for me: less distortion.
Why? Because much less movement is needed for each speakers for a given spl. And for woofer movement=distortion.
Same thing with BSC: using an attenuating high shelf=headroom=less distortion For some this is a waste of db... different point of view.
Hi,
Here is a good MTM design :
My RS180 MTM Design
Optionally build it as a tall floorstander,
bigger volume with more extended bass.
rgds, sreten.
Here is a good MTM design :
My RS180 MTM Design
Optionally build it as a tall floorstander,
bigger volume with more extended bass.
rgds, sreten.
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Interesting comment about the crossover choice of even or odd order from power response point of view.
Clever way to deal with the compromise many d'appolito's design seems to exhibit to some listeners. Thank you Sreten, should sound good too Dayton woofers have low distortion which remind me some Scanspeaks (with differences! Not same price range).
I've already heard some hi-end d'appolito's design using same crossover choice and fc but with Scanspeak speakers and description from Jeff B. stand true to feelings i had at the time about the medium not being 'pushed forward'.
Clever way to deal with the compromise many d'appolito's design seems to exhibit to some listeners. Thank you Sreten, should sound good too Dayton woofers have low distortion which remind me some Scanspeaks (with differences! Not same price range).
I've already heard some hi-end d'appolito's design using same crossover choice and fc but with Scanspeak speakers and description from Jeff B. stand true to feelings i had at the time about the medium not being 'pushed forward'.
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IT takes 10db to perceive a doubling in loudness ...period. ..factors of ten. And 2 watts is not twice as loud as 1 watt either. factors of ten. 1-10-100-1000watt. so a 4 ohm driver pulling 200watts out of a 100 watt/8ohm amp is only 1 db louder. ....a second driver is said to be 3db louder.
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Not true and mix of different things:
if you're talking about loudness (perceived psycho acoustic) it is frequency and time behavior of sound source dependant. Being psycho acoustic it is highly variable between individuals too. In facts the 10db you quote is a worst case scenario at extreme frequencies (high or low) because 10db in the medium is much more than doubling (Fletcher and Munson and equal loudness curves should tell you something...) and it is accepted to be between 6 and 10 db.
If you are talking electronic gain (in line level) we are dealing with 20log so a doubling is equal to +6db. No psycho acoustic so you can use the term 'period'.
If we are talking acoustical we are dealing with power and this time it is 10log so doubling is equal to +3db (radiated acoustic power). Here too you can use the term 'period'.
You should have noticed that i did'nt use 'definitive' terms in the post you quoted, and it's probably because all this is relative and once you put loudspeakers in room other factors can play as room gain for low end...
This question seems to come up alot and the explanations are often misleading. In reality the problem is simple. Two drivers executing the same "motion" will produce double the pressure and therefore 20*log(2)=6dB greater SPL. It does not matter if the drivers are in different enclosures, or wired in series or parallel; as long as they execute the same motion, two will produce 6dB more than one. This assumes the driver spacing is much less than the wavelength of sound under consideration.
What happens, electrically, when series or parallel wiring is made, is a separate matter. Let's consider the three cases for which the drivers (each with resistance R) execute the same "motion".
Single driver:
resistance = R
voltage = V
power = V^2/R
SPL = a
Parallel wiring:
resistance = R/2
voltage = V
power = V^2/(R/2) = 2 V^2/R
SPL = a + 6dB
Series wiring:
resistance = 2R
voltage = 2V
power = (2V)^2/(2R) = 2 V^2/R
SPL = a + 6dB
So, we get another intuitive result, which is that as long as the two drivers execute the same motion, the power required from the amplifier doubles in both the series and parallel cases.
What happens, electrically, when series or parallel wiring is made, is a separate matter. Let's consider the three cases for which the drivers (each with resistance R) execute the same "motion".
Single driver:
resistance = R
voltage = V
power = V^2/R
SPL = a
Parallel wiring:
resistance = R/2
voltage = V
power = V^2/(R/2) = 2 V^2/R
SPL = a + 6dB
Series wiring:
resistance = 2R
voltage = 2V
power = (2V)^2/(2R) = 2 V^2/R
SPL = a + 6dB
So, we get another intuitive result, which is that as long as the two drivers execute the same motion, the power required from the amplifier doubles in both the series and parallel cases.
"In facts the 10db you quote is a worst case scenario at extreme frequencies (high or low)"
Actually, the contours of equal loudness (for sounding 'twice' as loud) are only 3dB~4dB apart in the 30hz~40hz range around 85dB~90dB. Above 110dB the contours become more than 10dB farther apart over most of the range.
I would accept a general 6dB figure, which also corresponds to a doubling of drive voltage.
For hi-fi, most inexpensive speakers go into power compression above about 10W. compare with 600W pro JBL drivers that have about 1dB of compression at -10 levels (60W).
Actually, the contours of equal loudness (for sounding 'twice' as loud) are only 3dB~4dB apart in the 30hz~40hz range around 85dB~90dB. Above 110dB the contours become more than 10dB farther apart over most of the range.
I would accept a general 6dB figure, which also corresponds to a doubling of drive voltage.
For hi-fi, most inexpensive speakers go into power compression above about 10W. compare with 600W pro JBL drivers that have about 1dB of compression at -10 levels (60W).
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