@Rudolf
I got my DCX for almost a year now. And I use it for the stereo sub-woofers only . From timing perspective it was great to have everything including the upper range connected to it. Soundwise it was much of a step back.
That's why I took the upper range off the DCX.
OFF TOPIC:
By the way. Nice Homepage. Lot of interesting stuff over there.
You forgot to mention the Bastanis Dipole speakers on your page. I am running a Bastanis Kingtone. One of the few very dynamic high sensivity Dipoles.
I'll give it try with the wings on the baffle as you mention on your homepage. Sounds interesting.
By the way, which city are you from? You can drop me mail! If you like;-)
@MJK
Let see if I can do some backward engineering on my dipole-woofers.
Would be nice to see if the quarter-wave calculation works
also for a double-ripole such as mine.
As i understood I'd have to subscribe for a year though to get the sheet. Is this correct ;-)
I got my DCX for almost a year now. And I use it for the stereo sub-woofers only . From timing perspective it was great to have everything including the upper range connected to it. Soundwise it was much of a step back.
That's why I took the upper range off the DCX.
OFF TOPIC:
By the way. Nice Homepage. Lot of interesting stuff over there.
You forgot to mention the Bastanis Dipole speakers on your page. I am running a Bastanis Kingtone. One of the few very dynamic high sensivity Dipoles.
I'll give it try with the wings on the baffle as you mention on your homepage. Sounds interesting.
By the way, which city are you from? You can drop me mail! If you like;-)
@MJK
Let see if I can do some backward engineering on my dipole-woofers.
Would be nice to see if the quarter-wave calculation works
also for a double-ripole such as mine.
As i understood I'd have to subscribe for a year though to get the sheet. Is this correct ;-)
I am always looking for test cases to analyze. If you send me your geometry (sketch or drawing) and driver parameters I will make it the default set-up for a worksheet. If you have measured data it is always good to see how it correlates with the calculations. Obviously the calculations are always the correct answer.
That is correct, a one year subsription is required.
After looking...
long and hard it seems that the SLS series of drivers that Calvin has recommended is still about the very best suited to Ripoles. Visaton also have a similar series of excellent drivers as well. For folks who do not have to keep a small budger the Volt series of Radial 15 and 18 drivers are impressive.
I have had some simulations run that showed that there are a few Eminence drivers that are cost effective and may work as long as they can be confirmed to be suitable with respects to low frquency noise generation. Since I do not have any of these driver I cannot comment on this but perhaps there are some here who own these units and can check them and comment. First an least (but still good bang for the buck) is the Beta 15 A this shows pretty goo results and is inexpensive and will move a lot of air. Second is the Delta 15 LFA which is only a little more money than the Beta and sims quite well and coud be a strong performer if it it does not make much noise at LF. Third is the Killomax Pro 18 A is a monster and should be capable of most impressive performance again the caveat is to check it for LF noise. The Volt series of Radial drivers is impressive and will work well in Ripoles but the price is also impressive. Regards moray James.
Peerless SLS data can be found here http://www.tymphany.com/
Visaton data here http://www.visaton.de/en/index.html
Volt Radial series data here
http://www.voltloudspeakers.co.uk/About_Us/about_us.html
long and hard it seems that the SLS series of drivers that Calvin has recommended is still about the very best suited to Ripoles. Visaton also have a similar series of excellent drivers as well. For folks who do not have to keep a small budger the Volt series of Radial 15 and 18 drivers are impressive.
I have had some simulations run that showed that there are a few Eminence drivers that are cost effective and may work as long as they can be confirmed to be suitable with respects to low frquency noise generation. Since I do not have any of these driver I cannot comment on this but perhaps there are some here who own these units and can check them and comment. First an least (but still good bang for the buck) is the Beta 15 A this shows pretty goo results and is inexpensive and will move a lot of air. Second is the Delta 15 LFA which is only a little more money than the Beta and sims quite well and coud be a strong performer if it it does not make much noise at LF. Third is the Killomax Pro 18 A is a monster and should be capable of most impressive performance again the caveat is to check it for LF noise. The Volt series of Radial drivers is impressive and will work well in Ripoles but the price is also impressive. Regards moray James.
Peerless SLS data can be found here http://www.tymphany.com/
Visaton data here http://www.visaton.de/en/index.html
Volt Radial series data here
http://www.voltloudspeakers.co.uk/About_Us/about_us.html
Driver freq. response curves....
It would seem that not only are the T/S patameters important for Ripole/dipole drivers but also the drivers response curve will tell you a big part of the storey. With Ripole/Dipole cabinet you must depend upon the drivers ability to make bass as you do not have the benefit of a low tuned reflex vent to augment bass output. So the driver does what it does and you get what you get. I think that the response curve of the driver will tell you more than the T/S perametes will. If you are going to choose between two drivers where the T/S numbers are about the same choose the one that has the best low frequency response curve. If you look at the curves of most bass drivers they will show a significant roll off between 100 and 20 Hz. typically as much as 20 db or more. Many sub woofers drop like a rock starting as high as 100 - 200 Hz. The best drivers show only a 10 - 15 db drop in response between 100 and 20 Hz. These are the drivers that you want to consider for use in a Ripole/Dipole system as you will have the most amount of output where you want (need) it with the least amount of EQ.
I have noticed that the drivers with really big strong motors with BL above about 15 tend to be over damped and do not typically have the best LF curves. Just something to keep in mind. Auto sound drivers in the 8" to 10 " size may well be worth looking into at 12" and larger the pro drivers seem to have the largest selection but price starts to go up. Regards Moray James.
It would seem that not only are the T/S patameters important for Ripole/dipole drivers but also the drivers response curve will tell you a big part of the storey. With Ripole/Dipole cabinet you must depend upon the drivers ability to make bass as you do not have the benefit of a low tuned reflex vent to augment bass output. So the driver does what it does and you get what you get. I think that the response curve of the driver will tell you more than the T/S perametes will. If you are going to choose between two drivers where the T/S numbers are about the same choose the one that has the best low frequency response curve. If you look at the curves of most bass drivers they will show a significant roll off between 100 and 20 Hz. typically as much as 20 db or more. Many sub woofers drop like a rock starting as high as 100 - 200 Hz. The best drivers show only a 10 - 15 db drop in response between 100 and 20 Hz. These are the drivers that you want to consider for use in a Ripole/Dipole system as you will have the most amount of output where you want (need) it with the least amount of EQ.
I have noticed that the drivers with really big strong motors with BL above about 15 tend to be over damped and do not typically have the best LF curves. Just something to keep in mind. Auto sound drivers in the 8" to 10 " size may well be worth looking into at 12" and larger the pro drivers seem to have the largest selection but price starts to go up. Regards Moray James.
Driver noise considerations...
since driver noise is a greater concern in all dipole designs than it is in box designs I am wondering at what point (in terms of excurssion) one needs to move from non vented spider design to a driver with a vented spider? Any thoughts or comments? This would seem to impact driver considerations especially with smaller diameter drivers (8 - 10 inch) where longer excursions are required. Regards Moray James.
since driver noise is a greater concern in all dipole designs than it is in box designs I am wondering at what point (in terms of excurssion) one needs to move from non vented spider design to a driver with a vented spider? Any thoughts or comments? This would seem to impact driver considerations especially with smaller diameter drivers (8 - 10 inch) where longer excursions are required. Regards Moray James.
Re: Driver freq. response curves....
Moray,
if TSP are good for anything then it´s for EXACTLY predicting the bass response of a driver. If you see different diagrams for drivers with the same TSPs, then it exclusively stems from different measuring conditions (different baffle size, anechoic/not anechoic, microphone distance etc.) or from manipulated TSP (that happens too!).
The only excuse would be a driver with a cone so floppy that it breaks up below ~200 Hz, since T/S assume the cone to be a flat rigid piston. I don´t dare to suppose that such a bad driver would ever find it´s way into your home.
Rudolf
moray james said:
Moray,
if TSP are good for anything then it´s for EXACTLY predicting the bass response of a driver. If you see different diagrams for drivers with the same TSPs, then it exclusively stems from different measuring conditions (different baffle size, anechoic/not anechoic, microphone distance etc.) or from manipulated TSP (that happens too!).
The only excuse would be a driver with a cone so floppy that it breaks up below ~200 Hz, since T/S assume the cone to be a flat rigid piston. I don´t dare to suppose that such a bad driver would ever find it´s way into your home.
Rudolf
Re: Driver noise considerations...
I would definitely say that you must use open spider for all bass applications.
Excursion is much larger in open baffle and efficiency is much lower, add these two and you're there... My first dipole experiments with cheap and too small budget woofers actually produced so much other noises that the bass output was completely swamped by it
In my search for the perfect driver I once was allowed to perform the 'noise-test' on a whole range of 10 and 12" drivers in a local loudspeaker shop (the owner was very interested as well). I don't remember exactly, but I tested drivers from most popular manufacturers on the (European) DIY market, Visaton, Vifa, Monacor, Peerless, Seas, Scanspeak, some budget stuff, ..... These tests clearly revealed that only very few drivers are suited for open baffle use at all and that a vented spider is a must for real quiet operation, even at excursions of only a few mm
I also looked at cheap car woofers but found that in general they are of very poor quality. The better ones often cost more than a decent unit for home-use.
Drivers with very strong motors (Q<0.5) can be used with no problem and will allow you to set the final Q of your system according to your preferences. But this will require additional EQ in the filter. Using active EQ (which is mandatory anyway IMHO) that's no big deal.
BTW the ultimate dipole driver is probably the Cabasse 55 ND, a 22" and 40 mm stroke unit. Don't know if it's still available. Not a cheap one either
moray james said:
I would definitely say that you must use open spider for all bass applications.
Excursion is much larger in open baffle and efficiency is much lower, add these two and you're there... My first dipole experiments with cheap and too small budget woofers actually produced so much other noises that the bass output was completely swamped by it
In my search for the perfect driver I once was allowed to perform the 'noise-test' on a whole range of 10 and 12" drivers in a local loudspeaker shop (the owner was very interested as well). I don't remember exactly, but I tested drivers from most popular manufacturers on the (European) DIY market, Visaton, Vifa, Monacor, Peerless, Seas, Scanspeak, some budget stuff, ..... These tests clearly revealed that only very few drivers are suited for open baffle use at all and that a vented spider is a must for real quiet operation, even at excursions of only a few mm
I also looked at cheap car woofers but found that in general they are of very poor quality. The better ones often cost more than a decent unit for home-use.
Drivers with very strong motors (Q<0.5) can be used with no problem and will allow you to set the final Q of your system according to your preferences. But this will require additional EQ in the filter. Using active EQ (which is mandatory anyway IMHO) that's no big deal.
BTW the ultimate dipole driver is probably the Cabasse 55 ND, a 22" and 40 mm stroke unit. Don't know if it's still available. Not a cheap one either
Re: Driver noise considerations...
Two heretical comments concerning venting:
1. It´s all or nothing.
My Visaton W250 (http://www.visaton.de/en/chassis_zubehoer/tiefton/w250_8.html) in H-frames have no venting whatsoever. Air is completely trapped behind the spider. While this does not help to improve Qm, it definitely keeps the driver from generating air noise. First unwanted noise you hear in the dipole application is the stamped steel basket vibrating.
So IMHO you should keep the driver as airtight as possible or as amply vented as possible.
2. Do your own tracheotomy.
I have never done it myself, but it sounds worthwhile and the soldering iron will be your friend: By burning some holes into the spider (be careful to do that symmetrically) you get the back of the spider vented. And by cutting a hole into the dustcap you get the pole vented to the front of the speaker. Obviously all holes have to be wide enough to cope with the air flow. And obviously the TSP will change (slightly) by manipulating the respiration tract.
Anyone cares to do the reality check here??
Two heretical comments concerning venting:
1. It´s all or nothing.
My Visaton W250 (http://www.visaton.de/en/chassis_zubehoer/tiefton/w250_8.html) in H-frames have no venting whatsoever. Air is completely trapped behind the spider. While this does not help to improve Qm, it definitely keeps the driver from generating air noise. First unwanted noise you hear in the dipole application is the stamped steel basket vibrating.
So IMHO you should keep the driver as airtight as possible or as amply vented as possible.
2. Do your own tracheotomy.
I have never done it myself, but it sounds worthwhile and the soldering iron will be your friend: By burning some holes into the spider (be careful to do that symmetrically) you get the back of the spider vented. And by cutting a hole into the dustcap you get the pole vented to the front of the speaker. Obviously all holes have to be wide enough to cope with the air flow. And obviously the TSP will change (slightly) by manipulating the respiration tract.
Anyone cares to do the reality check here??
About ripole equalising
I had promised to close my general ripole rant with some notes regarding passive EQ. Doing this I will mostly rehash what I have learned from Axel´s and Calvin´s postings on other forums. And Calvin certainly will correct me where and when I get off the point.
The main reason for equalisation certainly is the first quarter wave resonance peak at the upper end of the ripole transmission range. This can be well done with a standard serial LCR notch filter in parallel with the driver. The values of this notch filter only depend on the required frequency and notch Q.
http://www.diyaudio.com/forums/attachment.php?s=&postid=568430&stamp=1107611565
To work properly this notch filter needs to see a resistive load (L1 in the diagram). This could be anything between 0.47-0.68 Ohm. Obviously this resistor must be a heavy duty one, since it is in line with the driver. A very clever solution is to join this resistance with a load impedance which will work as a low pass filter from ~100 Hz. So a coil of 6.8 mH / R=0.5-0.7 would be perfect for a driver impedance of 4 Ohm (or two 8 Ohm drivers in parallel). For a single 8 Ohm driver the load impedance should be halved to ~2-5 mH.
This low pass filter helps to subdue the resonance peaks and dips of the quarter wave pipe as well as possible noise from the subwoofer amp. Because the resistance of L1 becomes part of the system Qes, the system Qts will rise too – resulting in a slightly extended bass range.
Implementations of this passive ripole filter have been published at http://www.lautsprechershop.de/hifi/ripol_bau_en.htm and http://www.diyaudio.com/forums/showthread.php?postid=568430#post568430
Attention:
Since the position of the first quarter wave resonance peak is a function of driver AND ripole frame, its exact value can only be determined by measurement. Being off 10 % can render the notch filter useless. So interpolating notch filter values from different published ripole dimensions or drivers is trial and error – well, mostly error.
Rudolf
I had promised to close my general ripole rant with some notes regarding passive EQ. Doing this I will mostly rehash what I have learned from Axel´s and Calvin´s postings on other forums. And Calvin certainly will correct me where and when I get off the point.
The main reason for equalisation certainly is the first quarter wave resonance peak at the upper end of the ripole transmission range. This can be well done with a standard serial LCR notch filter in parallel with the driver. The values of this notch filter only depend on the required frequency and notch Q.
http://www.diyaudio.com/forums/attachment.php?s=&postid=568430&stamp=1107611565
To work properly this notch filter needs to see a resistive load (L1 in the diagram). This could be anything between 0.47-0.68 Ohm. Obviously this resistor must be a heavy duty one, since it is in line with the driver. A very clever solution is to join this resistance with a load impedance which will work as a low pass filter from ~100 Hz. So a coil of 6.8 mH / R=0.5-0.7 would be perfect for a driver impedance of 4 Ohm (or two 8 Ohm drivers in parallel). For a single 8 Ohm driver the load impedance should be halved to ~2-5 mH.
This low pass filter helps to subdue the resonance peaks and dips of the quarter wave pipe as well as possible noise from the subwoofer amp. Because the resistance of L1 becomes part of the system Qes, the system Qts will rise too – resulting in a slightly extended bass range.
Implementations of this passive ripole filter have been published at http://www.lautsprechershop.de/hifi/ripol_bau_en.htm and http://www.diyaudio.com/forums/showthread.php?postid=568430#post568430
Attention:
Since the position of the first quarter wave resonance peak is a function of driver AND ripole frame, its exact value can only be determined by measurement. Being off 10 % can render the notch filter useless. So interpolating notch filter values from different published ripole dimensions or drivers is trial and error – well, mostly error.
Rudolf
Driver at the alter the holy spider...
Rudolf: I have a number of odd 12 & 15 inch car driver kicking around for so long now I think that if one died for a test it would not be a hardship. I will have to look for my test disk with sine wave tones and then I can take my iron to a spider to see how much reduction in noise there is pre and post operation. I can also test to see what happens with dust cap venting.
I think that most of the noise you hear with sealed spiders is from air making its way through the spider as most spiders are porus. One might consider sealing the spider to make it air tight but this would to some degree affect stiffness (but not too much I think) as well as the Mms (I think). Have I got this right venting spider and dust cap reduces Mms and sealing the spider and dust cap (making them air tight) will increase Mms? Thanks Moray James.
Rudolf: I have a number of odd 12 & 15 inch car driver kicking around for so long now I think that if one died for a test it would not be a hardship. I will have to look for my test disk with sine wave tones and then I can take my iron to a spider to see how much reduction in noise there is pre and post operation. I can also test to see what happens with dust cap venting.
I think that most of the noise you hear with sealed spiders is from air making its way through the spider as most spiders are porus. One might consider sealing the spider to make it air tight but this would to some degree affect stiffness (but not too much I think) as well as the Mms (I think). Have I got this right venting spider and dust cap reduces Mms and sealing the spider and dust cap (making them air tight) will increase Mms? Thanks Moray James.
Re: Driver at the alter the holy spider...
if I remember correctly you alter Cms with those alterations. But since Cms is part of the equation for Mms, it should effectively turn out as a change in Mms too. I will check that out tomorrow in the morning (in my part of the globe)
Rudolf
Hello Moray,moray james said:
if I remember correctly you alter Cms with those alterations. But since Cms is part of the equation for Mms, it should effectively turn out as a change in Mms too. I will check that out tomorrow in the morning (in my part of the globe)
Rudolf
Thanks Rudolf...
I was thinking mostly about the impact of air mass loading with the spider vents decreasing the air load somewhat. You are right as suspension stiffness will also be impacted as the two are hand in hand together. So if the air load is reduced some then the suspension stiffness will behave as if it were a little stiffer when presented with the lighter load.
Venting or removing the dust cap will reduce/eliminate the compression of air that would normally occur beneath the dust cap and also impact both Cms and Mms with the bigger affect on Cms (I am guessing here) which would most likely result in a reduction of Fs.
Removal of the dust cap will probably have as great an impact upon driver noise (reduction of compression inside the voice coil system) as would some vents under the spider. Just a guess but the volumes involved (under the dust cap and under the spider) are probably close in volume). Holes in the vioce coil former above the spider have been used as heat pumps which also help to equalize the pressure on both sides of the voice coil in the motor structure. I have not seen heat pump holes in large high power pro bass drivers and I must assume that perhaps this is because they would compromise the former integrity under very hard drive conditions. It is well known that even solid heavy formers can buckle under severe stress due to the impact of the shock wave generated by the voice coil/motor. This is of course an extreem example but it does happen. I have often wondered why designers do not simply do away with the former all together as it limits heat disapation toward the pole piece (acts as a thermal insulator). There are companies (18 Sound) that wind voice coils on both the outside and the inside of the former to address this very issue but I wonder why the do not just wind a flat ribbon voice coil instead and do away wit the former alltogether. Note that the issue of multiple windings with this design suggestion could be dealt with by winding a flat bifilar ribbon coil. In this way the voice coil is able to thermally sink to both the top plate and the pole piece without any thermal insulation from a former. Just some ramblings regards Moray James.
I was thinking mostly about the impact of air mass loading with the spider vents decreasing the air load somewhat. You are right as suspension stiffness will also be impacted as the two are hand in hand together. So if the air load is reduced some then the suspension stiffness will behave as if it were a little stiffer when presented with the lighter load.
Venting or removing the dust cap will reduce/eliminate the compression of air that would normally occur beneath the dust cap and also impact both Cms and Mms with the bigger affect on Cms (I am guessing here) which would most likely result in a reduction of Fs.
Removal of the dust cap will probably have as great an impact upon driver noise (reduction of compression inside the voice coil system) as would some vents under the spider. Just a guess but the volumes involved (under the dust cap and under the spider) are probably close in volume). Holes in the vioce coil former above the spider have been used as heat pumps which also help to equalize the pressure on both sides of the voice coil in the motor structure. I have not seen heat pump holes in large high power pro bass drivers and I must assume that perhaps this is because they would compromise the former integrity under very hard drive conditions. It is well known that even solid heavy formers can buckle under severe stress due to the impact of the shock wave generated by the voice coil/motor. This is of course an extreem example but it does happen. I have often wondered why designers do not simply do away with the former all together as it limits heat disapation toward the pole piece (acts as a thermal insulator). There are companies (18 Sound) that wind voice coils on both the outside and the inside of the former to address this very issue but I wonder why the do not just wind a flat ribbon voice coil instead and do away wit the former alltogether. Note that the issue of multiple windings with this design suggestion could be dealt with by winding a flat bifilar ribbon coil. In this way the voice coil is able to thermally sink to both the top plate and the pole piece without any thermal insulation from a former. Just some ramblings regards Moray James.
Very interesting thread. I really appreciate the information.
How about the Dayton Reference series subwoofers?
RSS315 12" subwoofer
RSS390 15" subwoofer
Neither driver really needs a Fs reduction, but other than that they seem suitable and not too expensive.
Thoughts?
Thanks.
Paul Ebert
How about the Dayton Reference series subwoofers?
RSS315 12" subwoofer
RSS390 15" subwoofer
Neither driver really needs a Fs reduction, but other than that they seem suitable and not too expensive.
Thoughts?
Thanks.
Paul Ebert
inexpensive driver option...
This driver has been used and considered aceptable and is very inexpensive. Regards Moray James.
http://www.mach5audio.com/product_info.php?products_id=41&osCsid=df22114511d5b9b07ea425a028ed2259
This driver has been used and considered aceptable and is very inexpensive. Regards Moray James.
http://www.mach5audio.com/product_info.php?products_id=41&osCsid=df22114511d5b9b07ea425a028ed2259
Re: inexpensive driver option...
This MAW 12 driver seems good value for money, parameters are just about right. Too bad it doesn't seem to have an open spider, as far as I can see from the pictures. Well it's cheap enough to risk some hole drilling...
Btw how do you want to compensate for the 6db/oct slope using only passive filtering? You need a truly massive coil for that.
This MAW 12 driver seems good value for money, parameters are just about right. Too bad it doesn't seem to have an open spider, as far as I can see from the pictures. Well it's cheap enough to risk some hole drilling...
Btw how do you want to compensate for the 6db/oct slope using only passive filtering? You need a truly massive coil for that.
maybe this will be quicker: http://www.marchandelec.com/fg.html
Additional post...
This letter was posted elsewhere and I thought that the comments would be of use and interest here. Regards Moray James.
Driver considerations are the same as for a normal open baffle. Therefore high surface area (think of 12, 15 or 18 inch) low fs, highish qts (>0.4), and preferably high xmax with a lot of power or high efficiency + reasonable xmax (8 mm).
The only addition a ripole yields is that the baffle is more or less folded and the chamber behind and in front of the woofer generates a lower fs of the complete system.
When some parameters are off spec (say a low qts of a typical PA woofer) you need more eq in the filter. In my case (Visaton BGS 40) I wasted the efficiency of two times 98 dB/w/m resulting in a inroom efficiency of about 93.
In addition I've to say that the room dictates the lower threshold of the FR response as shown in one of the papers on the website of JohnK.
By the way, I forgot to mention the ripole resonance, this needs atleast a parallel LCR circuit in combination with a >3rd order electrical filter. The resonance is typically in the 200-300 Hz range so a lot of uF and mH are in order (typically >10 mH and >300 uF). The design can only be finalized when you atleast can measure the impedance (resonance is easily recognizable in the impedance curve) but IMHO to be able to design a proper loudspeaker you also need to measure the FR.
--------------------------------------------------------------------------------
This letter was posted elsewhere and I thought that the comments would be of use and interest here. Regards Moray James.
Driver considerations are the same as for a normal open baffle. Therefore high surface area (think of 12, 15 or 18 inch) low fs, highish qts (>0.4), and preferably high xmax with a lot of power or high efficiency + reasonable xmax (8 mm).
The only addition a ripole yields is that the baffle is more or less folded and the chamber behind and in front of the woofer generates a lower fs of the complete system.
When some parameters are off spec (say a low qts of a typical PA woofer) you need more eq in the filter. In my case (Visaton BGS 40) I wasted the efficiency of two times 98 dB/w/m resulting in a inroom efficiency of about 93.
In addition I've to say that the room dictates the lower threshold of the FR response as shown in one of the papers on the website of JohnK.
By the way, I forgot to mention the ripole resonance, this needs atleast a parallel LCR circuit in combination with a >3rd order electrical filter. The resonance is typically in the 200-300 Hz range so a lot of uF and mH are in order (typically >10 mH and >300 uF). The design can only be finalized when you atleast can measure the impedance (resonance is easily recognizable in the impedance curve) but IMHO to be able to design a proper loudspeaker you also need to measure the FR.
--------------------------------------------------------------------------------
watch out for your amp...
Paul: both the Dayton drivers that you mention will probably work very well in a dipole design. You will want to watch out if you run dual units as in a W or ripole configuration as the load to your amp is going to get low. You might want to opt for an H baffle or a U baffle with a single 15 inch unit to maximise your output and still maintain a healthy load for your amplifire(s). Regards Moray James.
Paul: both the Dayton drivers that you mention will probably work very well in a dipole design. You will want to watch out if you run dual units as in a W or ripole configuration as the load to your amp is going to get low. You might want to opt for an H baffle or a U baffle with a single 15 inch unit to maximise your output and still maintain a healthy load for your amplifire(s). Regards Moray James.
Beyma driver options...
Here are some Beyma drivers that would be suitable for dipole use. The number at the end of each driver (in brackets) is the driver's EBP which is the ratio of Fs devided by Qts which tells you the kind of enclosure the driver is intended for. An EBP close to 100 suggests a vented enclosure and a EBP close to 50 indicates a driver intended for a closed box. Dipoles would seem to prefer drivers with a EBP closer to 50 but there are numerous sucsessful designs with driver EBP close or over 100 so there is room to play. Most high efficiency pro driver are designed for reflex venting so you will see higher EBP's with them for the most part. You can find high excurssion car drivers with EBP's below the 50 range. Regards Moray James.
SM118/N (67)
21L50 – 73
18LX60 – 71
15LX60 – 97
12LX60 – 135
10LW30/N – 158
12BR70 (79.5)
10BR60 (72.5)
Here are some Beyma drivers that would be suitable for dipole use. The number at the end of each driver (in brackets) is the driver's EBP which is the ratio of Fs devided by Qts which tells you the kind of enclosure the driver is intended for. An EBP close to 100 suggests a vented enclosure and a EBP close to 50 indicates a driver intended for a closed box. Dipoles would seem to prefer drivers with a EBP closer to 50 but there are numerous sucsessful designs with driver EBP close or over 100 so there is room to play. Most high efficiency pro driver are designed for reflex venting so you will see higher EBP's with them for the most part. You can find high excurssion car drivers with EBP's below the 50 range. Regards Moray James.
SM118/N (67)
21L50 – 73
18LX60 – 71
15LX60 – 97
12LX60 – 135
10LW30/N – 158
12BR70 (79.5)
10BR60 (72.5)
I finally got around to testing the best cheap candidate that I could find locally in a 6"x9". They ended up being more than I hoped at $22/pr, but the performance exceeded my expectations primarily because it takes getting them up past 14mm of point to point excursion before they start behaving badly (sonic operation, etc.). That means that I can count on a solid 5mm of Xmax, and 4 drivers approximates the Sd of a 15". Yes, the Fs is high in the 50's, but that's where the ripole limited airway approach helps, although I may need to mass load the cones to get down below 40hz. Push/pull operation is a given due to the cheap construction.
The real beauty of 6x9's is how closely I can pack their Sd together. I plan to use 8 per side. It looks like I'll be able to fit 8 (equal to a pair of 15's) in a W cab that is 10" wide (maybe less), 10.5" deep, and 27" tall. Of course I'll add 4-5" of depth since it's a 2 for 1 value (4 for 1 compared to flat baffle width), and to achieve some U effects on dispersion.
For those not looking for high max output and/or low end extension, just think how compact 4 drivers could be. You could still do push/pull, and if you alternate the front pathways on the left and right sides, you can cancel most of the mechanics too using the typical Ripole alignment and have only a 7" width.
Another good alignment would be 6 drivers in a W (although you'd have to work at it to get reasonable symmetry). Then you stack them with the 9" driver dimension vertical, resulting in only 6" deep manifolds (higher extension possible). Then a 10"W by 12"D by 29"H would have the bass potential an 18" woofer on a 36" diameter baffle in free space, plus it would be a great compact stand for a main driver on a small baffle on top. I may have to rethink my plans as I'm not sure the extra 3db of potential is worth the extra pair of drivers and larger cab, not to mention less top end extension.
The real beauty of 6x9's is how closely I can pack their Sd together. I plan to use 8 per side. It looks like I'll be able to fit 8 (equal to a pair of 15's) in a W cab that is 10" wide (maybe less), 10.5" deep, and 27" tall. Of course I'll add 4-5" of depth since it's a 2 for 1 value (4 for 1 compared to flat baffle width), and to achieve some U effects on dispersion.
For those not looking for high max output and/or low end extension, just think how compact 4 drivers could be. You could still do push/pull, and if you alternate the front pathways on the left and right sides, you can cancel most of the mechanics too using the typical Ripole alignment and have only a 7" width.
Another good alignment would be 6 drivers in a W (although you'd have to work at it to get reasonable symmetry). Then you stack them with the 9" driver dimension vertical, resulting in only 6" deep manifolds (higher extension possible). Then a 10"W by 12"D by 29"H would have the bass potential an 18" woofer on a 36" diameter baffle in free space, plus it would be a great compact stand for a main driver on a small baffle on top. I may have to rethink my plans as I'm not sure the extra 3db of potential is worth the extra pair of drivers and larger cab, not to mention less top end extension.