About ripole dimensions (continued)
Well, I am not shure I should follow Paul´s nomenclature from the post above. I would still prefer to call the horizontal dimension of the ripole pipe opening it´s width. Otherwise he is mostly on topic. But maybe I can tell it even more precisely.
When we look at the most prominent difference between a common Linkwitz style W frame and a ripole it optically boils down to less width. But that´s not for style, but with reason. One design target for the ripole was to achieve an almost flat frequency response with only marginal electronic bass EQ. This was done by kind of mass loading the driver and raising the system Q that way. In a wide pipe the air volume would move freely and SPL would drop early. In a narrow pipe the air is more resistive against cone movement. Thus the cone can couple its energy more efficiently to the air mass. Narrowing the pipe has it´s limit when efficiency drops radically and the moving air becomes noisy. Comparable to a BR tube becoming too small.
The rule of thumb here is: If the drivers Xmax (peak-to-peak) is >10 mm, the opening area of the pipe should be not less than 1/3 Sd. If Xmax is less, the area might be reduced down to 1/4 Sd.
The pipe opening at the rear of the driver should be between 1/2 Sd and 1 Sd. The performance of the ripole is predominantly determined by the front pipe. There is no real need to get both volumes equal. But if you add the cone volume to the front pipe volume and subtract the same cone volume from the rear pipe volume you will get comparable volumes in many cases anyway.
A second design target for the ripole was the lowering of Fs. This can easily amount to 10 Hz reduction. A bigger VAS will result in a bigger reduction of Fs. So it is no use to look for rock bottom Fs under ~25 Hz in a driver.
This is definitely everything I can tell you about the ripole dimensions. Tomorrow I will try to add some comments regarding driver parameters and the – too much neglected – passive equalising cum notch filter.
Rudolf
Well, I am not shure I should follow Paul´s nomenclature from the post above. I would still prefer to call the horizontal dimension of the ripole pipe opening it´s width. Otherwise he is mostly on topic. But maybe I can tell it even more precisely.
When we look at the most prominent difference between a common Linkwitz style W frame and a ripole it optically boils down to less width. But that´s not for style, but with reason. One design target for the ripole was to achieve an almost flat frequency response with only marginal electronic bass EQ. This was done by kind of mass loading the driver and raising the system Q that way. In a wide pipe the air volume would move freely and SPL would drop early. In a narrow pipe the air is more resistive against cone movement. Thus the cone can couple its energy more efficiently to the air mass. Narrowing the pipe has it´s limit when efficiency drops radically and the moving air becomes noisy. Comparable to a BR tube becoming too small.
The rule of thumb here is: If the drivers Xmax (peak-to-peak) is >10 mm, the opening area of the pipe should be not less than 1/3 Sd. If Xmax is less, the area might be reduced down to 1/4 Sd.
The pipe opening at the rear of the driver should be between 1/2 Sd and 1 Sd. The performance of the ripole is predominantly determined by the front pipe. There is no real need to get both volumes equal. But if you add the cone volume to the front pipe volume and subtract the same cone volume from the rear pipe volume you will get comparable volumes in many cases anyway.
A second design target for the ripole was the lowering of Fs. This can easily amount to 10 Hz reduction. A bigger VAS will result in a bigger reduction of Fs. So it is no use to look for rock bottom Fs under ~25 Hz in a driver.
This is definitely everything I can tell you about the ripole dimensions. Tomorrow I will try to add some comments regarding driver parameters and the – too much neglected – passive equalising cum notch filter.
Rudolf
Moray asked me to mention a couple of drivers in connection with this subject of this thread.
The Max Pentivents are very well made, have a vented pole piece and from what I have heard testing a couple of 12 inchers in a W baffle, they work well for dipole bass.
Here are some specs.
I know of one member here who uses the PV1550!
I believe that the Pentivents are available on both sides of the Atlantic.
And Hemp acoustics are working on a 15 inch dipole woofer that will have an Xmax of 14 mm.
The Max Pentivents are very well made, have a vented pole piece and from what I have heard testing a couple of 12 inchers in a W baffle, they work well for dipole bass.
Here are some specs.
An externally hosted image should be here but it was not working when we last tested it.
I know of one member here who uses the PV1550!
I believe that the Pentivents are available on both sides of the Atlantic.
And Hemp acoustics are working on a 15 inch dipole woofer that will have an Xmax of 14 mm.
Rudolf,
You seem, no, you ARE absolute way more informed/experienced on the subject, so I'll follow your nomenclature
(I called it HEIGHT becouse in many of the pictures I've seen the cabinets seem to be 'laying down', the driver's horizontal, get it?)
I didn't know the Sd/front-mouth relationship was related to the Xmax, nor the Sd/rear-mouth width relationship, thanks!
I'll try to make some spreadsheet tomorrow to figure some values based on our common knowledge. As a matter of fact I've allready made one, just to calculate the wood dimensions (Bored at 'work' you see... )
So, for this S-sheet's enhaced version we need: Sd, driver's outside diameter, driver's height (To get rid of the hole in the back, if possible. That's a pita to achive...), Xmax, wood thickness, right?
Is there, or rather, do we yet know how to predict the Fs lowering, based on Vas, chamber size and some other parameters?
Regards, Tschüß, doeg, a+, Paul
You seem, no, you ARE absolute way more informed/experienced on the subject, so I'll follow your nomenclature
(I called it HEIGHT becouse in many of the pictures I've seen the cabinets seem to be 'laying down', the driver's horizontal, get it?)
I didn't know the Sd/front-mouth relationship was related to the Xmax, nor the Sd/rear-mouth width relationship, thanks!
I'll try to make some spreadsheet tomorrow to figure some values based on our common knowledge. As a matter of fact I've allready made one, just to calculate the wood dimensions (Bored at 'work' you see...
)So, for this S-sheet's enhaced version we need: Sd, driver's outside diameter, driver's height (To get rid of the hole in the back, if possible. That's a pita to achive...), Xmax, wood thickness, right?
Is there, or rather, do we yet know how to predict the Fs lowering, based on Vas, chamber size and some other parameters?
Regards, Tschüß, doeg, a+, Paul
I sometimes pity the fact that manufacturers are not at all clear on mechanical capabilities of their speakers, let alone noises produced by air displacement or cone breakup(flapping?wow, seems bad to me!).
Information on this shouldn't be limited to experience or guessing(knowing the materials and build).
Isn't there a way to produce free air specs based on showing all behavior other than desired?
Or don't they try becouse they're afraid of the results?
Or is it impossible to distinguish them that way becouse some flapping speaker can behave exellent in some enclosure design?
For a ripole I think a free air mechanical power capability graph(frequency related to max. electrical power connected in a sine-wave pattern keeping all within reasonable margins of distortion for example) might be helpfull.
Information on this shouldn't be limited to experience or guessing(knowing the materials and build).
Isn't there a way to produce free air specs based on showing all behavior other than desired?
Or don't they try becouse they're afraid of the results?
Or is it impossible to distinguish them that way becouse some flapping speaker can behave exellent in some enclosure design?
For a ripole I think a free air mechanical power capability graph(frequency related to max. electrical power connected in a sine-wave pattern keeping all within reasonable margins of distortion for example) might be helpfull.
Since this thread is about drivers and parameters, I should contribute some too.
In general Axel Ridtahler and some other competent ripole guys recommend a target system Q of ~0.7 to 0.9. This will be best achieved with driver Qts 0.5-0.7. But any Qts from 0.35 to 1 may be taken into consideration too.
Fs should be between 25 and 45 Hz. Remember that Fs reductions of 10-15 Hz for the ripole system are quite common!
VAS is indicative for the stiffness of the suspension. A PA driver with stiff accordion surround and resulting lower VAS would get less Fs reduction than a driver with a “loose” rubber surround.
Mms should be within reason. So better no 10 inch driver with a 120 g cone! Even 12 inch drivers should need no more mms than 80-120 g to give good results. 15 inch drivers should be content with mms < 160 gr.
So for instance mms-wise the Peerless SLS series would be suited much better than the XLS drivers.
Drivers that have been explicitly “approved” by those ripole guys or have been applied with good results are:
Rudolf
In general Axel Ridtahler and some other competent ripole guys recommend a target system Q of ~0.7 to 0.9. This will be best achieved with driver Qts 0.5-0.7. But any Qts from 0.35 to 1 may be taken into consideration too.
Fs should be between 25 and 45 Hz. Remember that Fs reductions of 10-15 Hz for the ripole system are quite common!
VAS is indicative for the stiffness of the suspension. A PA driver with stiff accordion surround and resulting lower VAS would get less Fs reduction than a driver with a “loose” rubber surround.
Mms should be within reason. So better no 10 inch driver with a 120 g cone! Even 12 inch drivers should need no more mms than 80-120 g to give good results. 15 inch drivers should be content with mms < 160 gr.
So for instance mms-wise the Peerless SLS series would be suited much better than the XLS drivers.
Drivers that have been explicitly “approved” by those ripole guys or have been applied with good results are:
- Peerless SLS series
- Vifa 30 WN 380 RL/8 Fs=21 Hz, Qts=0.21, Mms=61 g, VAS=328 l, Sd=507 cm²
(This driver reportedly had been produced to Ridtahler´s specifications and doesn´t really comply with the “rules” above. So you don´t have to stick to those rules too much too)
- GBS 515 Fs=24 Hz, Qts=0.47, Mms=160 g, VAS=257 l, Sd=835 cm²
(This discontinued driver was offered at the German ebay and is clearly the bigger brother of the RBS 512. Don´t confuse it with the new GBS 515 or GBS 5115, which are offered by the same vendor). TSPs are taken from an independent source: http://www.hifi-selbstbau.de/text.php?id=119&s=read
- RBS 512 Fs=29 Hz, Qts=0.42, Mms=196 g, VAS=61 l, Sd=531 cm²
(This driver has been approved by Ridtahler himself - notwithstanding the high mms)
- A&D 1530 Fs=46 Hz, Qts=0.48, Mms=xx, VAS=142 l, Sd= ~900 cm²
http://www.traumboxen.de/ad-audio/r1530.htm
- A&D 1830 Fs=34 Hz, Qts=0.64, Mms=xx, VAS=265 l, Sd=~1400 cm²
http://www.traumboxen.de/ad-audio/r1830.htm
- Visaton W 300 Fs=32 Hz, Qts=0.55, Mms=43 g, VAS=190 l, Sd=490 cm²
Rudolf
Hope this attached data sheet on the 30 WN 380 RL/8opens. If not here is a copy of the data on this driver. Regards Moray James.
Characteristics:
30-cm-Tieftonlautsprecher with very hard, conical paper diaphragm.
50-mm-Schwingspule, 4 lagig. Large stroke reserve (large mechanical stroke).
Ventilated magnetic system.
Ideal low clay/tone driver. Been suitable for bass reflex housings or closed volumes
(e.g. as Subwoofer, actively entzerrt).
Chassis data:
External dimensions: 308 mm Schw. - reel Ø: 40 mm
Installation dimension: 297 mm Schw. - reeling height 14 mm
Depth: 128.6 mm Schw. - spulen-Träger
Front. Material: Air gap height mm
Basket material: Air gap filling:
Diaphragm type: Magnet Ø: mm
Diaphragm Sicke: conical Magnet height: mm
Diaphragm material: Paper Magnet weight g
Dustcap material: Magnet Ind. T
Thiele Small parameter:
Resonance fms: 21 Cycles per second Indulgence Cms mm/N
mechanical. Quality Qms: 2.3 moved mass Mms: 53 g
electrical quality Qes: 0.25 mechanical. Absorption Rms: kg/s ¹
Total quality Qts: 0.23 Diaphragm stroke Xmax: mm
A-volume Vas: 400 Litre Force factor Bl: 12.7 N/A
DC resistance RH: Ohm Diaphragm Ø MD:
Inductance Le: mH Diaphragm surface Sd: 513 cm ²
Electrical absorption Res: Ohm Max. separation frequency. fmax: 1 kHz
Efficiency Nref: % Nominal sound pressure SPL: 93 railways
Product folder (English): Pdf Download (33 KB)
Characteristics:
30-cm-Tieftonlautsprecher with very hard, conical paper diaphragm.
50-mm-Schwingspule, 4 lagig. Large stroke reserve (large mechanical stroke).
Ventilated magnetic system.
Ideal low clay/tone driver. Been suitable for bass reflex housings or closed volumes
(e.g. as Subwoofer, actively entzerrt).
Chassis data:
External dimensions: 308 mm Schw. - reel Ø: 40 mm
Installation dimension: 297 mm Schw. - reeling height 14 mm
Depth: 128.6 mm Schw. - spulen-Träger
Front. Material: Air gap height mm
Basket material: Air gap filling:
Diaphragm type: Magnet Ø: mm
Diaphragm Sicke: conical Magnet height: mm
Diaphragm material: Paper Magnet weight g
Dustcap material: Magnet Ind. T
Thiele Small parameter:
Resonance fms: 21 Cycles per second Indulgence Cms mm/N
mechanical. Quality Qms: 2.3 moved mass Mms: 53 g
electrical quality Qes: 0.25 mechanical. Absorption Rms: kg/s ¹
Total quality Qts: 0.23 Diaphragm stroke Xmax: mm
A-volume Vas: 400 Litre Force factor Bl: 12.7 N/A
DC resistance RH: Ohm Diaphragm Ø MD:
Inductance Le: mH Diaphragm surface Sd: 513 cm ²
Electrical absorption Res: Ohm Max. separation frequency. fmax: 1 kHz
Efficiency Nref: % Nominal sound pressure SPL: 93 railways
Product folder (English): Pdf Download (33 KB)
Hi folks.
I finished my ripoles using 4* BD15 drivers of Bert Doppenberg some time ago.
These are 16R drivers with an efficiency of 97db each!
This a much higher efficiency than you're discussing here!
I am more than happy with them.
Read this:
http://www.bd-design.nl/forum/forum_entry.php?id=11047
\Klaus
I finished my ripoles using 4* BD15 drivers of Bert Doppenberg some time ago.
These are 16R drivers with an efficiency of 97db each!
This a much higher efficiency than you're discussing here!
I am more than happy with them.
Read this:
http://www.bd-design.nl/forum/forum_entry.php?id=11047
\Klaus
18 Sound drivers...
Have a look at these drivers by 18 Sound
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=201
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=203
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=215
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=230
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=233
Regards Moray James.
Have a look at these drivers by 18 Sound
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=201
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=203
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=215
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=230
http://www.eighteensound.com/index.aspx?mainMenu=view_product&pid=233
Regards Moray James.
Hi,
Rudolfs comments are correct so far so good. So I´ll add just a few words.
I can´t confirm his findings regarding drivers with stiff suspensions. My findings have been that especially those PA-drivers with stiff suspensions show high values of Fs-reduction even when the open area of the chambers is quite large compared to the Sd. Mostly the reduction lies within the range ~5Hz-10Hz, but with those stiff PA-drivers sometimes nearly 20Hz is possible! Too theses drivers normally show a better performance for infrasonics. The highest excursions happen on the fs and sinking values show below fs. Drivers with soft supensions show greater excursions values below fs.
In practise You can torture drivers with strongly progressive and/or stiff supensions much harder than drivers with sloppy suspensions.
The Vifa should best be forgotten. The reason why this driver was used was not because of its parameters, but because of a kind of OT-reason
Its usability for Ripoles is rather low and Axel and his partners were never really happy about it.
Peerless drivers have been intensively used in ripoles, from the older poly-types to the new SLS-series which have close to reference-parameter-sets. Those can be recommended wholeheartedly. Any other driver should be checked on its noise-performance. Many drivers with good sets of parameters lack in the noise departement. So unless tested no recommendation should be believed in!
jauu
Calvin
ps: @soundcheck: You´re claimed 97dB efficiency is worth nothing since it´s just applicable outside the working range of the driver Just displacement volume counts for SPL here!
Rudolfs comments are correct so far so good. So I´ll add just a few words.
I can´t confirm his findings regarding drivers with stiff suspensions. My findings have been that especially those PA-drivers with stiff suspensions show high values of Fs-reduction even when the open area of the chambers is quite large compared to the Sd. Mostly the reduction lies within the range ~5Hz-10Hz, but with those stiff PA-drivers sometimes nearly 20Hz is possible! Too theses drivers normally show a better performance for infrasonics. The highest excursions happen on the fs and sinking values show below fs. Drivers with soft supensions show greater excursions values below fs.
In practise You can torture drivers with strongly progressive and/or stiff supensions much harder than drivers with sloppy suspensions.
The Vifa should best be forgotten. The reason why this driver was used was not because of its parameters, but because of a kind of OT-reason
Its usability for Ripoles is rather low and Axel and his partners were never really happy about it.Peerless drivers have been intensively used in ripoles, from the older poly-types to the new SLS-series which have close to reference-parameter-sets. Those can be recommended wholeheartedly. Any other driver should be checked on its noise-performance. Many drivers with good sets of parameters lack in the noise departement. So unless tested no recommendation should be believed in!
jauu
Calvin
ps: @soundcheck: You´re claimed 97dB efficiency is worth nothing since it´s just applicable outside the working range of the driver
Just displacement volume counts for SPL here!@ calvin
97db SPL is according to spec of course!
2 in parallel giving me a real 91db SPL at 8R ! To me it's worth a lot I'd say.
I don't need a power plant to get my drivers moving.
I havn't heard a more airy realistic bass yet.
And I heard the originals!
I just wanted to mention that there are alternative drivers
out there.
BR
97db SPL is according to spec of course!
2 in parallel giving me a real 91db SPL at 8R ! To me it's worth a lot I'd say.
I don't need a power plant to get my drivers moving.
I havn't heard a more airy realistic bass yet.
And I heard the originals!
I just wanted to mention that there are alternative drivers
out there.
BR
I looked at the referenced German site with the U, H, A, W and the two Ripole enclosures. I believe that all of these can be modeled using my MathCad worksheets with some degree of accuracy. I already have older models of the U, H, and A frame dipoles that just need to be updated to the latest calculation scheme. Adding the W and Ripole enclosures will not be that difficult. The models would include the enclosures sitting on the floor with a movable rear wall boundary condition similar to my exisiting models.
I just uploaded new versions of my existing worksheets tonight that I have been updating for the past few weeks. These represent small updates and corrections to the previous versions. I am at a point of starting to work on my next topic, I was going to go back to working on horns but if there is enough interest I will spend the next month or two working on various additional "dipole" worksheets. I can see a set of worksheets that calculate the response of the driver/enclosure for a constant input voltage and then the user would need to decide on any boosting circuits to extend the low end response.
Is this what people want and is there enough support?
I just uploaded new versions of my existing worksheets tonight that I have been updating for the past few weeks. These represent small updates and corrections to the previous versions. I am at a point of starting to work on my next topic, I was going to go back to working on horns but if there is enough interest I will spend the next month or two working on various additional "dipole" worksheets. I can see a set of worksheets that calculate the response of the driver/enclosure for a constant input voltage and then the user would need to decide on any boosting circuits to extend the low end response.
Is this what people want and is there enough support?
Hi Martin,MJK said:
as you can see from the posters nationalities, ripoles seem to be an international affair. So basicly there is demand for H, W and N enclosure simulation worksheets in Europe too. But Mathcad still is a huge barrier here. And AJ-Horn is a potent contender. So I believe those dipole simulations would be a welcome extension of your portfolio, but will not rise the number of your supporters in Europe (at least on the continent) significantly.
Just to make shure it gets your attention: Those dipole simulations should include the low pass filter to attenuate the quarter wave resonance. It´s always good to know how much that resonance can be subdued without a notch filter. But I believe you already have taken care for that.
Rudolf
Hi folks.
Just another hint. If anybody is interested
I am running a DCX2496 digital crossover to control my Dipole Subs.
Gives you phantastic options to manipulate the frequency repsonse and the dipole integration if needed.
Slopes of 48db/oct can be configured.
Paramteric equalizers are at hand with flexible Q configurations.
Phase and timing can be even automatically adjusted by the crossover itself on per inch/cm basis.
Not to forget the level adjustment.
I crossing my dipoles over at 100Hz just the right frequency to avoid getting in trouble with the unlinear dipole response.
With a 48db slope I finally got rid of the very negative subwoofer response in the mids. The poor quality of any woofer compared to your mid-woofer or fullrange driver will alwas badly impact your lower mids. These days are over!
There is no way to get the Dipoles easier integrated in your setup and to your room.
Highly recommended.
\Klaus
Just another hint. If anybody is interested
I am running a DCX2496 digital crossover to control my Dipole Subs.
Gives you phantastic options to manipulate the frequency repsonse and the dipole integration if needed.
Slopes of 48db/oct can be configured.
Paramteric equalizers are at hand with flexible Q configurations.
Phase and timing can be even automatically adjusted by the crossover itself on per inch/cm basis.
Not to forget the level adjustment.
I crossing my dipoles over at 100Hz just the right frequency to avoid getting in trouble with the unlinear dipole response.
With a 48db slope I finally got rid of the very negative subwoofer response in the mids. The poor quality of any woofer compared to your mid-woofer or fullrange driver will alwas badly impact your lower mids. These days are over!
There is no way to get the Dipoles easier integrated in your setup and to your room.
Highly recommended.
\Klaus
Actually, what has surprised the me most is the number of Europeans that have subscribed to the worksheets. By far the largest percentage of users. The US users have been a small minority. Most of my correspondence comes from Europe also.
MathCad does scare off a lot of first time users. However, once people get past that initial turn-off they really learn to use MathCad very quickly and become productive. I have had very few people give up because of MathCad once they get started.