Hi,
Alvis doesn't understand the question or the physics much to claims to the
contrary. Utterly tedious, as is making out you know what your what your
talking about, when your clearly making up nonsense as you go along.
Two drivers in a 0.5 way configuration are fine in the same box, as would
be two drivers covering the same range. Rolling off the midrange of one
driver does not affect the midrange of the other to any significant effect.
In this design I'd say the main issue is the high mid/treble x/o point,
its asking for trouble due to driver spacing and mid dispersion issues.
A 2" mid isn't going to go that low without running into excursion issues,
a 3.5 way is a bit better for driver integration, but a 3 way should work.
rgds, sreten.
Alvis doesn't understand the question or the physics much to claims to the
contrary. Utterly tedious, as is making out you know what your what your
talking about, when your clearly making up nonsense as you go along.
Two drivers in a 0.5 way configuration are fine in the same box, as would
be two drivers covering the same range. Rolling off the midrange of one
driver does not affect the midrange of the other to any significant effect.
In this design I'd say the main issue is the high mid/treble x/o point,
its asking for trouble due to driver spacing and mid dispersion issues.
A 2" mid isn't going to go that low without running into excursion issues,
a 3.5 way is a bit better for driver integration, but a 3 way should work.
rgds, sreten.
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Rubbish!
Rubbish. Rubbish. Rubbish!!
Even if the 6.5" are driven by separate crossovers at 200 and 1KHz, the relative electrical phase in the low bass below 100Hz (where the excursions are likely to become meaningful) will be fairly close between the drivers, enough to have them performing pretty much in synchrony. The amount of pressure modulation from the "bass" driver on the "bass+midrange" driver will be very small in a single enclosure, barely perceptible. Been there, done that. It works very well.
Your notion of pressure imbalance would only be true if one of the drivers were being rolled off in the bass - and this is not the case in the OP's proposed design. In essence BOTH DRIVERS are being driven with bass frequencies and for the most part in phase. The difference in relative phase angle seen by the drivers will small enough to make very little difference.
In direct comparisons with double small chambers vs single of the same volume, the differences are practically un-measurable and mostly imperceptible.
That being said, if I were looking to build the "absolute purist version" I probably would "split" the internal enclosure into two, using a diagonal divider to reduce some of the standing waves. At that point might as well have separately sealed enclosures for each driver.
Alvis your example of the 3" driver being pressure modulated would be relevant if it were a driver without a sealed back sharing the same enclosure. Of course it would be pushed around by the bass pressure waves! But the OP clearly stated he wants to use a 2" dome, which in all probability has a sealed back already, so if that's what you were referring to, it's not something to worry about.
Acoustical clipper/compressor??
Rubbish. Rubbish. Rubbish!!
Even if the 6.5" are driven by separate crossovers at 200 and 1KHz, the relative electrical phase in the low bass below 100Hz (where the excursions are likely to become meaningful) will be fairly close between the drivers, enough to have them performing pretty much in synchrony. The amount of pressure modulation from the "bass" driver on the "bass+midrange" driver will be very small in a single enclosure, barely perceptible. Been there, done that. It works very well.
Your notion of pressure imbalance would only be true if one of the drivers were being rolled off in the bass - and this is not the case in the OP's proposed design. In essence BOTH DRIVERS are being driven with bass frequencies and for the most part in phase. The difference in relative phase angle seen by the drivers will small enough to make very little difference.
In direct comparisons with double small chambers vs single of the same volume, the differences are practically un-measurable and mostly imperceptible.
That being said, if I were looking to build the "absolute purist version" I probably would "split" the internal enclosure into two, using a diagonal divider to reduce some of the standing waves. At that point might as well have separately sealed enclosures for each driver.
Alvis your example of the 3" driver being pressure modulated would be relevant if it were a driver without a sealed back sharing the same enclosure. Of course it would be pushed around by the bass pressure waves! But the OP clearly stated he wants to use a 2" dome, which in all probability has a sealed back already, so if that's what you were referring to, it's not something to worry about.
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BSEE may be of some value
OK, I will have at it. I actually have some qualifications in the form of a BSEE and over thirty years working in the audio industry. What are yours?
What possible education can I bring?
Quite a lot actually.
Go re-read the edited reply. Then go study some of this stuff. Read up and actually learn something before spouting off.
Ignorance followed by rants just confirms what we were all beginning to suspect.
OK, I will have at it. I actually have some qualifications in the form of a BSEE and over thirty years working in the audio industry. What are yours?
What possible education can I bring?
Quite a lot actually.
Go re-read the edited reply. Then go study some of this stuff. Read up and actually learn something before spouting off.
Ignorance followed by rants just confirms what we were all beginning to suspect.
Who's ranting?
All a BSEE implies is you went to school. Good for you.
This specific topic is not taught while earning a BSEE, so your educational background is moot.
I would think that if you were credible selling $36,000 "Holistic" speakers you would have more then a gmail account?
The only thing "Holistic" is the the hole those electric bird feeders would leave in your wallet.
Science is looking at us in the rear-view mirror and laughing.
All a BSEE implies is you went to school. Good for you.
This specific topic is not taught while earning a BSEE, so your educational background is moot.
I would think that if you were credible selling $36,000 "Holistic" speakers you would have more then a gmail account?
The only thing "Holistic" is the the hole those electric bird feeders would leave in your wallet.
Science is looking at us in the rear-view mirror and laughing.
I think that flyingtele has enough info to make up his mind whether he believes there is reason to separate the drivers. I don't believe there is as has already been stated in one way or another, the pressure and or backwave in a cabinet with 2 drivers or 2 half size cabinets with them separate is going to have the same effect on the driver(s) midrange, regardless.
I think we just made it a 4 way, and in that case you would have little choice but to separate the drivers. But... using different drivers to cover the same frequencies smells bad to begin with.
I'm sorry but your argument just doesn't hold water.This specific topic is not taught while earning a BSEE, so your educational background is moot.
Your supposition is wrong: the "specific topic" most certainly IS taught as part of simple linear circuit theory, and if you want to you can actually load this up on a simulator to look at the differences. Anyone who has a grasp of this aspect of engineering will tell you this.
2nd, I haven't just studied this stuff, I've actually built it. Have you? I've spent 30+ years designing and building speakers professionally. I've tried 2.5 and 3.5 designs just as in the specific example that is being discussed in this thread, and had very good results, measured and audible from one enclosure for both drivers and from dual enclosures, and the difference just wasn't big enough to be able to say it's significant. Your notion that the midrange will be overly modulated just doesn't hold up theoretically, NOR DOES IT HOLD UP IN PRACTICE. Give it up, dude!
That some of my products are extremely expensive? Yes.
They are hand-crafted, custom tuned products which perform to an extremely high standard. I make no apologies for them or their pricing.
So in what way does that preclude me from being able to offer advice to the OP and others on this site? Does charging money for my work make me into a bad guy in the DIY world? Let's see: Linkwitz, Geddes, Kreskovsky, Nelson Pass and a few others are well regarded for their contributions to this forum. Last time I checked, some of their products are pretty expensive also!
But I'm also interested in making high performance systems at a lower cost and am about to introduce a line of Open Baffle kits which are very nearly as good at less than 1/10th the price. (I don't expect you Alvis will be lining up to buy, and that's fine by me. I try to stay clear of potentially hostile clients!)
Like I said, go study up, then we can discuss from a base of knowledge rather than uninformed speculation.
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Not always
Hey Cal, actually Nestorovic did use dissimilar woofers (12" + 15") and (10" + 12") and made some pretty good speakers. Not saying it's easy though...
But... using different drivers to cover the same frequencies smells bad to begin with.
Hey Cal, actually Nestorovic did use dissimilar woofers (12" + 15") and (10" + 12") and made some pretty good speakers. Not saying it's easy though...
We have had this particular discussion before Cal, it worked back in the 70s and all I said then I say again.
"It worked for those big Japanese speakers that used it."
The combination was usually an 8inch mid-woofer and a 10 inch .5.
Perhaps we have higher expectations these days, lots of people still like KEF and IMF monitors for instance but you know we could design much better with modern drivers.
Next one I find in an OP-Shop I'll try and remember to take photos.
Or build one and ask for a listening test.
Read Zaphs discourse on the subject
"It worked for those big Japanese speakers that used it."
The combination was usually an 8inch mid-woofer and a 10 inch .5.
Perhaps we have higher expectations these days, lots of people still like KEF and IMF monitors for instance but you know we could design much better with modern drivers.
Next one I find in an OP-Shop I'll try and remember to take photos.
Or build one and ask for a listening test.
Read Zaphs discourse on the subject
Here Cal
Lots of talk about them in the past.
http://www.diyaudio.com/forums/multi-way/190529-nestorovic-woofer-system.html
OP may be interested
Lots of talk about them in the past.
http://www.diyaudio.com/forums/multi-way/190529-nestorovic-woofer-system.html
OP may be interested
The discussion in this thread was getting personal. Please keep to debating ideas and not making things personal.
"simple linear theory" is just that. It does not even brush the compounding of evanescent acoustic waves.
So by your own admittance there is a measurable difference, yet in the same paragraph you say it does not hold up in practice?
So is this science or opinion now?
"Significant" is am matter of opinion. Lot's of very small numbers are discussed on these forums and most are significant to somebody.
A a few milliamps here, afew % HD there...
I'm fine with people making lot's of money, I truly am.
However someone with a BSEE should not selling, in my opinion questionable products and attributing them to a BSEE.
What precludes you is your bias for money skews your opinion, in my opinion, which is unscientific.
Linkwitz and the like are known for their selfless contributions, not what they try and take away.
They both make money and contribute in completely separate forums.
So at 1/10th the cost you will be selling Open Baffle speakers for $3,600?
Is that plus taxes and delivery?
Your right, I won't be lining up.
It's a shame you consider scientific debate as hostile.
So let's sum up here, I was wrong and two unbalance drivers in the same enclosure some how magically cancel out and don't effect each other.
Then, by your own admissions, there is a measurable difference and yet I am still wrong.
It would also be interesting to know how you isolated one driver from the other when performing this measurement.
What exactly were you measuring for?, did you have a baseline to go from, and if so how did you create a baseline for a 2.5 or 3.5 without the distortion to compare to. Smells fishy.
Just curious Alvis, but you do realise that in a 2.5 way (or 3.5 way) that BOTH drivers are playing down to the lowest bass frequencies don't you?
Your argument about the bass from the .5 way affecting the midrange of the driver running the full spectrum I think is what people are questioning here (as both drivers are producing the same bass frequencies below 200Hz).
The only interference I can see personally is the midrange frequencies that the driver running the full spectrum would be potentially modulating in the .5 way speaker which is only running up to 200Hz, but that does not appear to be what you are saying.
Tony.
Your argument about the bass from the .5 way affecting the midrange of the driver running the full spectrum I think is what people are questioning here (as both drivers are producing the same bass frequencies below 200Hz).
The only interference I can see personally is the midrange frequencies that the driver running the full spectrum would be potentially modulating in the .5 way speaker which is only running up to 200Hz, but that does not appear to be what you are saying.
Tony.
Close, just the other way around.
Since there is an excess of bass below 200Hz, this 200Hz and below will modulate the mid-range frequencies in the "full spectrum" driver.
Since folks widdle down power supply ripple to such low numbers I'm surprised that this is so accepted.
This modulated ripple could loosely resemble power supply ripple, except its not a steady 60Hz, it modulated from 200Hz down to as low as the amp goes, and only appears when there is <200Hz information in the source.
Since there is an excess of bass below 200Hz, this 200Hz and below will modulate the mid-range frequencies in the "full spectrum" driver.
Since folks widdle down power supply ripple to such low numbers I'm surprised that this is so accepted.
This modulated ripple could loosely resemble power supply ripple, except its not a steady 60Hz, it modulated from 200Hz down to as low as the amp goes, and only appears when there is <200Hz information in the source.
There's no excess of bass below 200Hz: perhaps you've heard of baffle step losses?
The addition of another driver covering below the baffle step frequency means the energy that would've been lost is now regained. Just another form of BSC.
Perhaps I have?, thats is really a different issue though.
There is an excess of bass pressure inside the box.
You have one playing bass, the other playing bass and mid. The bass being the common denominator.
Add that to the fact the energy levels involved are much higher with bass then the mids, which makes the situation worse.
Those mid frequencies will have to fight hard to stay linear against a wildly fluctuating cabinet pressure.
Any time bass <200Hz hits, the mid range will compress or compound excursion depending on how the waves line up in time.
There is an excess of bass pressure inside the box.
You have one playing bass, the other playing bass and mid. The bass being the common denominator.
Add that to the fact the energy levels involved are much higher with bass then the mids, which makes the situation worse.
Those mid frequencies will have to fight hard to stay linear against a wildly fluctuating cabinet pressure.
Any time bass <200Hz hits, the mid range will compress or compound excursion depending on how the waves line up in time.
How does it modulate it ?
The two drivers are pushing equally against each other in the box at bass frequencies. The presence of the bass only driver provides a back pressure that causes the mid-bass driver to move half as much as it would have. This reduces bass modulation of the midrange.
The only real issue I can see with both drivers sharing the same enclosure in a 2.5 way system is additional re-radiation of the midrange back-wave through the cone of the woofer.
With a single driver the midrange that radiates backwards into the box and is not fully absorbed by box stuffing will re-radiate through the (relatively porous to sound) cone of the driver itself.
In a 2.5 way you have a second porous cone in the same cavity for this unwanted back-wave to radiate through, meaning you'll get a bit of midrange leakage through the cone of the woofer as well even though it isn't generating any midrange of its own...
An "excess" ? What does that mean exactly ?
How is this any different to a 2 way ? Bass excursions are always much greater than midrange, period.
Complete nonsense.
The cabinet back pressure from the second driver will cause the driver producing both midrange and bass to have half the excursion that it would otherwise need if it was the only driver in the box producing bass.Half the excursion means less distortion in the midrange as well as the bass.
Depending on how the waves line up ? What on earth does that mean ?
At bass frequencies for any modest size box there will not be any standing waves in the box at bass frequencies, it will be operating entirely in the pressurisation region. This means the two drivers will stay well balanced in both excursion and loading through all bass frequencies.
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