What do you think :
https://www.sal.hu/termekdokumentumok/04646_03_01.pdf
it has few photos on web, difference in them. looks slightly like jbl ?
https://www.google.sk/search?q=sal+pa+50100&espv=2&biw=1680&bih=963&source=lnms&tbm=isch&sa=X&ei=tzCVVJaLI8bkyAO_wIH4Cg&ved=0CAYQ_AUoAQ#tbm=isch&q=sal+pa+50100&imgdii=xhYqp5RMgJT5aM%3A%3BMDzWzrDwib_evM%3BxhYqp5RMgJT5aM%3A
https://www.sal.hu/termekdokumentumok/04646_03_01.pdf
it has few photos on web, difference in them. looks slightly like jbl ?
https://www.google.sk/search?q=sal+pa+50100&espv=2&biw=1680&bih=963&source=lnms&tbm=isch&sa=X&ei=tzCVVJaLI8bkyAO_wIH4Cg&ved=0CAYQ_AUoAQ#tbm=isch&q=sal+pa+50100&imgdii=xhYqp5RMgJT5aM%3A%3BMDzWzrDwib_evM%3BxhYqp5RMgJT5aM%3A
I would say it's a no go. A Qts of 1.25 is not what you want for a OB woofer. Find one with 0.7 or less.
Also, air displacement is the key factor for OB woofers, you need high displacement drivers if you want some serious output. Displacement is cone area times max linear stroke. As both max linear stroke and voice coil en air gap height in the specs are missing there is no way of telling the displacement of this driver.
Check out the site of Linkwitz on OB woofer design.
Also, air displacement is the key factor for OB woofers, you need high displacement drivers if you want some serious output. Displacement is cone area times max linear stroke. As both max linear stroke and voice coil en air gap height in the specs are missing there is no way of telling the displacement of this driver.
Check out the site of Linkwitz on OB woofer design.
I have a couple of questions:
Why is a Qts of 1.25 not what you'd want for an Open Baffle?
However, you believe that a Qts of 0.7 or less is what you'd want?
Depending on the particular application, your advice is either Dead Wrong or a fairly legitimate recommendation. Perhaps you should explain to the OP the particular conditions, requirements and goals that warrent your opinion/recommendation.
Best Regards,
TerryO
Well if your goal is to make a lot of noise any driver will be ok but I assume the choice for OB is related to a certain aim for HQ sound reproduction.
With an OB system the Qtd of the entire uncompensated system will be slightly higher then the Qts of the driver. I guess we all know a Qts of 0.5-0.7 is considered to be optimal for good low frequency response and a Q of >1.25 will result in poor frequency and transient response.
It is to some extent possible to compensate in the electronics but it is easier and the results are better when the starting point is a Qts of <0.7.
Have a look at this and this 🙂
With an OB system the Qtd of the entire uncompensated system will be slightly higher then the Qts of the driver. I guess we all know a Qts of 0.5-0.7 is considered to be optimal for good low frequency response and a Q of >1.25 will result in poor frequency and transient response.
It is to some extent possible to compensate in the electronics but it is easier and the results are better when the starting point is a Qts of <0.7.
Have a look at this and this 🙂
Last edited:
Hi,
Would those who know nothing about OB design please
stop talking nonsense. Qts's up to about 2 are very
usable with no EQ and suitable baffle dimensions.
(Though you make shirk the consequences of ~>1.3.)
Thing is you are stuck to suitable baffle dimensions.
Any OB starting off with with Qts < 1.0 will need
electronic EQ by default for decently balanced bass.
It is a different argument that EQ'd low Qts drivers
are better than non EQ'd high Qts drivers, usually
about distortion, and to a lesser extent about
driver efficiency and the driving power required.
Of course EQing allows you to vary baffle size
and baffle loss for any driver, but reality kicks
in, in a vicious way for OB's and bass extension,
in terms of the maximum possible bass SPL.
rgds, sreten.
http://www.quarter-wave.com/OBs/OB_Design.pdf
Would those who know nothing about OB design please
stop talking nonsense. Qts's up to about 2 are very
usable with no EQ and suitable baffle dimensions.
(Though you make shirk the consequences of ~>1.3.)
Thing is you are stuck to suitable baffle dimensions.
Any OB starting off with with Qts < 1.0 will need
electronic EQ by default for decently balanced bass.
It is a different argument that EQ'd low Qts drivers
are better than non EQ'd high Qts drivers, usually
about distortion, and to a lesser extent about
driver efficiency and the driving power required.
Of course EQing allows you to vary baffle size
and baffle loss for any driver, but reality kicks
in, in a vicious way for OB's and bass extension,
in terms of the maximum possible bass SPL.
rgds, sreten.
http://www.quarter-wave.com/OBs/OB_Design.pdf
Last edited:
Sreten,
Thank you for providing much needed and correct information!
Best Regards,
TerryO
Also a "no go" due to the none smooth response around 100 hz but more importantly, all the little wiggles in the impedance trace which indicates anomelies in the motor/cone/spider/surround design. I'll bet this drive sound quite poor. The mechanical aspects of a driver is reflected in the impedance - look for a super smooth trace.
//
//
I´m surprised because alpha15a has similar qts, being popular is this setup
------
------
so this bigger woofer, has better parameters in overall ?
i´d like to see these (two per side perhaps overkill) mounted on slight U baffel.
plate amp (or if possible, not) and fostex pumped from small se
should be better than two alphas?
plate amp (or if possible, not) and fostex pumped from small se
should be better than two alphas?
From the Horse's Mouth
Just to untangle a few minds, here's a copy of an e-mail I received and was later posted to DIYAudio. This was right from the horse's mouth and is the explanation of what was done during the development of the first really sucessful open baffle speaker:
I created the Carver Amazing woofer system and Large Area Ribbon (co-authored with David Graebener) for Bob Carver in the mid 1980's as a consultant to Carver Corporation and was VP of Research and Development at Carver in the 1990s. I would be glad to answer any questions anyone has about these devices.
One question that was asked was whether the Amazings had a high or low Qms. The Qms was quite high, we attempted to achieve a Qms of nearly 10, which is required if one is going to end up with a Qt of much greater than 2 and still maintain reasonable efficiency.
The trick is to be able to maintain 'linear' Qms. One of the big problems we found early in the development of the Hi-Q open baffle was that many of the Hi-Q drivers have Qms values that change depending on level. This non-linear Qms causes a non-linear Qts, which causes a non-linear frequency response with level...i.e. compression/distortion. This Qms modulation is one of the main reasons that some have found higher Qts drivers to sound bad. It’s is not the higher Qts, but the Qms -> Qts nonlinearity that causes the poor sound quality. Proper Qts match to baffle cut-off frequency will perform quite perfectly, even for higher Qt values if the resulting frequency response is flat and the Qt value is maintained at all listening levels.
The Amazing suspension components, spider and surround, took nearly 9 months to work through the design problems to chase out the non-linearities. No one had optimized high-Q woofers previous to the Amazings so the driver vendors were not able to help. We had to drive the component development ourselves. It was hard to get spiders with low enough damping (they actually call them dampers in Japan) to achieve high-Q and then it was even more difficult to develop spiders and surrounds that maintained constant damping.
Okay, that is probably more than what anyone wanted to know on that subject, but I felt it was important to start getting past this myth that “high-Q drivers are bad”. It is a systems approach. High-Q is not inherently bad, but ‘mismatched’-Q is. A high-Q driver is appropriate when matched to a ‘low-Q baffle’, just as a Low-Q driver is appropriate to match to a ‘high-Q’ Helmholtz enclosure.
The original Amazings had even higher Qts and lower Fs than the later Series. As someone in the forum suggested, lower Fs requires higher-Q, but this becomes problematic. For a fixed baffle cutoff frequency, with the standard 6 dB/octave high pass characteristic from cut-off down to the resonant frequency, the ideal high-Q gain would match that first order slope over the bandwidth from cutoff to fs. Unfortunately, the 12 dB of gain we needed in the original Amazings to achieve reference level at the Fs of 20 Hz required a Qts of about 4. This created a narrow band peak that doesn’t match the smooth, 6 dB roll-off slope of the open baffle. Because of this we had to use some shaping networks to smooth things out from 25 Hz to 100 Hz. We ended up with a fairly smooth response with a peak at 20 Hz and Fc at 17 or 18 Hz.
The later Amazings had a new lower mass paper cone woofer to replace the heavier honeycomb devices in the originals. We were able to get the moving mass down to less than 15 grams, which is quite low for a 12” woofer, but required for getting decent efficiency.
The Fs was raised to 30 Hz and the Qts was lowered to a value between 2.5 and 3. This worked much better in matching the Fs, Qts, and baffle Fc to get a smoother response and much higher efficiency.
I’ll stop here. Hopefully this info is of some interest to the group. If not, I apologize for hi-jacking your space.
Warm regards,
- Jim
Just to untangle a few minds, here's a copy of an e-mail I received and was later posted to DIYAudio. This was right from the horse's mouth and is the explanation of what was done during the development of the first really sucessful open baffle speaker:
I created the Carver Amazing woofer system and Large Area Ribbon (co-authored with David Graebener) for Bob Carver in the mid 1980's as a consultant to Carver Corporation and was VP of Research and Development at Carver in the 1990s. I would be glad to answer any questions anyone has about these devices.
One question that was asked was whether the Amazings had a high or low Qms. The Qms was quite high, we attempted to achieve a Qms of nearly 10, which is required if one is going to end up with a Qt of much greater than 2 and still maintain reasonable efficiency.
The trick is to be able to maintain 'linear' Qms. One of the big problems we found early in the development of the Hi-Q open baffle was that many of the Hi-Q drivers have Qms values that change depending on level. This non-linear Qms causes a non-linear Qts, which causes a non-linear frequency response with level...i.e. compression/distortion. This Qms modulation is one of the main reasons that some have found higher Qts drivers to sound bad. It’s is not the higher Qts, but the Qms -> Qts nonlinearity that causes the poor sound quality. Proper Qts match to baffle cut-off frequency will perform quite perfectly, even for higher Qt values if the resulting frequency response is flat and the Qt value is maintained at all listening levels.
The Amazing suspension components, spider and surround, took nearly 9 months to work through the design problems to chase out the non-linearities. No one had optimized high-Q woofers previous to the Amazings so the driver vendors were not able to help. We had to drive the component development ourselves. It was hard to get spiders with low enough damping (they actually call them dampers in Japan) to achieve high-Q and then it was even more difficult to develop spiders and surrounds that maintained constant damping.
Okay, that is probably more than what anyone wanted to know on that subject, but I felt it was important to start getting past this myth that “high-Q drivers are bad”. It is a systems approach. High-Q is not inherently bad, but ‘mismatched’-Q is. A high-Q driver is appropriate when matched to a ‘low-Q baffle’, just as a Low-Q driver is appropriate to match to a ‘high-Q’ Helmholtz enclosure.
The original Amazings had even higher Qts and lower Fs than the later Series. As someone in the forum suggested, lower Fs requires higher-Q, but this becomes problematic. For a fixed baffle cutoff frequency, with the standard 6 dB/octave high pass characteristic from cut-off down to the resonant frequency, the ideal high-Q gain would match that first order slope over the bandwidth from cutoff to fs. Unfortunately, the 12 dB of gain we needed in the original Amazings to achieve reference level at the Fs of 20 Hz required a Qts of about 4. This created a narrow band peak that doesn’t match the smooth, 6 dB roll-off slope of the open baffle. Because of this we had to use some shaping networks to smooth things out from 25 Hz to 100 Hz. We ended up with a fairly smooth response with a peak at 20 Hz and Fc at 17 or 18 Hz.
The later Amazings had a new lower mass paper cone woofer to replace the heavier honeycomb devices in the originals. We were able to get the moving mass down to less than 15 grams, which is quite low for a 12” woofer, but required for getting decent efficiency.
The Fs was raised to 30 Hz and the Qts was lowered to a value between 2.5 and 3. This worked much better in matching the Fs, Qts, and baffle Fc to get a smoother response and much higher efficiency.
I’ll stop here. Hopefully this info is of some interest to the group. If not, I apologize for hi-jacking your space.
Warm regards,
- Jim
Last edited:
Interesting thread, esp if one has a giant OB.
1. I don't immediately see how you can hear a Q that varies and why, as Jim says, it sounds lousy (considering all the other more direct aspects of speakers-in-rooms that can make the sound lousy)?
2. Many fine old fine woofers seem to approximate what Jim is talking about and are suitable for giant OBs: light cones (strength not a primary issues with OB forces) and very flexible suspensions leading to very low Fs but not so low Qs.
3. My impression ie that simplified geometry of textbook OBs applies only very loosely when you carpenter a complicated shape baffle which is then installed in a complicated space. But Jim is right to emphasize the need to coordinate the fall-off of the baffle with the resonant boost of the driver. Pity you have to traffic in resonances (and other dirty things) in order to cobble together a reasonable freq curve: but it works for me.
Ben
1. I don't immediately see how you can hear a Q that varies and why, as Jim says, it sounds lousy (considering all the other more direct aspects of speakers-in-rooms that can make the sound lousy)?
2. Many fine old fine woofers seem to approximate what Jim is talking about and are suitable for giant OBs: light cones (strength not a primary issues with OB forces) and very flexible suspensions leading to very low Fs but not so low Qs.
3. My impression ie that simplified geometry of textbook OBs applies only very loosely when you carpenter a complicated shape baffle which is then installed in a complicated space. But Jim is right to emphasize the need to coordinate the fall-off of the baffle with the resonant boost of the driver. Pity you have to traffic in resonances (and other dirty things) in order to cobble together a reasonable freq curve: but it works for me.
Ben
Last edited:
Part of the issue is......the vast majority of woofer-subwoofer drivers available nowadays are lowish Qts designs. Some professional drivers have lower motor strength, but other trade-offs seem to eliminate them from consideration.
If you also take the approach that you don't want to use electronic equalization, then you really have yourself in a design pickle before even starting. 🙂
Open baffle woofers are pretty darn neat, but you have to throw away many pre-conceived notions in order to construct a successful one.
Cheers,
Dave.
If you also take the approach that you don't want to use electronic equalization, then you really have yourself in a design pickle before even starting. 🙂
Open baffle woofers are pretty darn neat, but you have to throw away many pre-conceived notions in order to construct a successful one.
Cheers,
Dave.
Prolly important for most drivers to have sub-sonic filter "EQ", maybe starting just north of Fs.
Once I even had "interesting" sound from a 12-inch driver hanging from a cord and using nothing but a series milli-hency coil.
I'd be interested in seeing curves of OB performance vis a vis sim prediction.
Ben
I personally find it hard to understand why to mount woofers to an OB to transmitt even below Schroeder frequency of the room at all.
Normally one will have to direct ("toe in") the (open) baffles towards the listening seat.
Having a noteable angle of toe in (say 20 degrees or even more) you start loosing potential dipole specific advantages in low- to mid bass impulse response by exciting modes even in left to right direction (shorter axis) of the room.
This is a common drawback of e.g. fullrange ESL and similar concepts like fullrange "planar magnetics" etc. Why mimick this suboptimal behaviour without need ?
It does not unfold to my mind, why - when already constructing multiway system using conventional drivers - there is not a dedicated (e.g. dipole-) subwoofer, which excites the room in parallel to the longest axis of the room.
Furthermore one (ore more) subwoofer(s) can be placed more freely for balanced excitation of the room with special respect to the main listening seat.
A multiway OB with woofers down below Schroeder is like using a motor to build a coach IMO.
The only OB design making use of dipole specific advantages is a "satellite OB" of moderate (tall) shape, which can also act like a dipole in the midrange.
"Big wide fullrange baffle with tweeter on it" (possibly even without segmenting the baffle for mids and highs) e.g. is a crude combination of disadvantages IMO ...
Normally one will have to direct ("toe in") the (open) baffles towards the listening seat.
Having a noteable angle of toe in (say 20 degrees or even more) you start loosing potential dipole specific advantages in low- to mid bass impulse response by exciting modes even in left to right direction (shorter axis) of the room.
This is a common drawback of e.g. fullrange ESL and similar concepts like fullrange "planar magnetics" etc. Why mimick this suboptimal behaviour without need ?
It does not unfold to my mind, why - when already constructing multiway system using conventional drivers - there is not a dedicated (e.g. dipole-) subwoofer, which excites the room in parallel to the longest axis of the room.
Furthermore one (ore more) subwoofer(s) can be placed more freely for balanced excitation of the room with special respect to the main listening seat.
A multiway OB with woofers down below Schroeder is like using a motor to build a coach IMO.
The only OB design making use of dipole specific advantages is a "satellite OB" of moderate (tall) shape, which can also act like a dipole in the midrange.
"Big wide fullrange baffle with tweeter on it" (possibly even without segmenting the baffle for mids and highs) e.g. is a crude combination of disadvantages IMO ...
Last edited:
Nelson liked the Beta15 as a good balance of cheap and cheerful.
(I remember a massive 2x beta (passive) with a Lowther on top, can't find ...)
So did Martin.
www.quarter-wave.com/OBs/OB_Design.pdf
So do I:
http://www.diyaudio.com/forums/mult...-tool-real-time-dsp-crossover-adjustment.html
(I remember a massive 2x beta (passive) with a Lowther on top, can't find ...)
So did Martin.
www.quarter-wave.com/OBs/OB_Design.pdf
So do I:
http://www.diyaudio.com/forums/mult...-tool-real-time-dsp-crossover-adjustment.html
Last edited:
Hi,
Non linear Qms and also in fact the related non linear Vas,
basically the suspension linearity are issues for all drivers.
Low Qts drivers by definition are usually used in boxes smaller
than Vas, and the box air linearises the suspension a great deal.
However low Qts drivers EQd are just as bad as a high Qts drivers
in typical OB's, basically because the suspensions are the same.
The Carver, FWIW tried to use a Qts of 2 to 3, similar to electrostatics.
And big low mass mass drivers, with low Fs, hence uttertly huge Vas.
Fine idea, wrong pushing the envelope, as suspension design for
typical big drivers simply is not based on silly low mass cones.
There is no design "pickle" not wanting to use EQ, quite the
opposite. The driver in the OP is ideal for a no active EQ OB.
As MJK describes the best bass driver for a 2 way passive
OB is about ~ 9dB* more sensitive than the mid/treble
driver and has a Qts in the region of 1.1 to 1.3.
rgds, sreten.
* You will lose all this and the bass peak of a Qts=1.2
driver as baffle loss, i.e. SPL loss, for a given excursion.
A 15" open baffle will not go loud, the same ~ boxed 6.5".
Non linear Qms and also in fact the related non linear Vas,
basically the suspension linearity are issues for all drivers.
Low Qts drivers by definition are usually used in boxes smaller
than Vas, and the box air linearises the suspension a great deal.
However low Qts drivers EQd are just as bad as a high Qts drivers
in typical OB's, basically because the suspensions are the same.
The Carver, FWIW tried to use a Qts of 2 to 3, similar to electrostatics.
And big low mass mass drivers, with low Fs, hence uttertly huge Vas.
Fine idea, wrong pushing the envelope, as suspension design for
typical big drivers simply is not based on silly low mass cones.
There is no design "pickle" not wanting to use EQ, quite the
opposite. The driver in the OP is ideal for a no active EQ OB.
As MJK describes the best bass driver for a 2 way passive
OB is about ~ 9dB* more sensitive than the mid/treble
driver and has a Qts in the region of 1.1 to 1.3.
rgds, sreten.
* You will lose all this and the bass peak of a Qts=1.2
driver as baffle loss, i.e. SPL loss, for a given excursion.
A 15" open baffle will not go loud, the same ~ boxed 6.5".
Last edited:
Yeah, but how big of a baffle (and what shape) would you mount it in/on?
If you're going to construct a dipole woofer that doesn't take up a huge amount of floor space, then you're going to have to address and deal with 6db/octave dipole cancellation effects in some way. A driver with Qts=1.25 does not have an acoustic response that complements a standard dipole correction over any kind of reasonable range. (This is the "pickle" I'm talking about.)
I don't happen to agree with MJK on his statement......but you probably already know that. 🙂
One thing about constructing open-baffle dipole woofers........they're easy to build and experiment with. That's what I would encourage everyone to do.
Cheers,
Dave.
Hi,
Your wrong. The combination of excess senstivity and the mild
kick up of Q=1.2 around Fs does allow you to build a passive
low pass filter that does the acoustic job relatively well.
You would be right with no excess senstivity, but that
is a very wrong way of not understanding anything.
Its pointless to disagree with MJK on all major points.
(Well I did, a long time ago, and he graciously admitted
he was wrong, such types end up being never wrong.)
I don't agree on some of the minor argueable points.
rgds, sreten.
Last edited:
- Status
- Not open for further replies.