Much prettier than my box, which wasn't planned out and used as much scrap as possible
http://farm4.static.flickr.com/3245/3121346919_6c1fc47a0e.jpg?v=0
http://farm4.static.flickr.com/3240/3122172386_358c59257c.jpg?v=0
Should have these finished a day late thats Monday now.
http://farm4.static.flickr.com/3245/3121346919_6c1fc47a0e.jpg?v=0
http://farm4.static.flickr.com/3240/3122172386_358c59257c.jpg?v=0
Should have these finished a day late thats Monday now.
I finished the test boxes, I've been listening for a short while, not too shabby very deep bass, I can hear notes that aren't there when using the Cerwin Vega, my partner says same thing deeper and richer, interesting.
Next I need to make up a test box for a H-frame and compare the two.
Having made a Ri-pole with a driver that really isn't suitable I think with a suitablr drier they are a very viable alternative, only drawback is the lack of SPL so the need to listen to them near-field.
http://farm4.static.flickr.com/3113/3122319636_287d0ded11_t.jpg
http://farm4.static.flickr.com/3200/3121493163_f2b0ffb32a_t.jpg
That is the 12inch CV along side for comparison.
Next I need to make up a test box for a H-frame and compare the two.
Having made a Ri-pole with a driver that really isn't suitable I think with a suitablr drier they are a very viable alternative, only drawback is the lack of SPL so the need to listen to them near-field.
http://farm4.static.flickr.com/3113/3122319636_287d0ded11_t.jpg
http://farm4.static.flickr.com/3200/3121493163_f2b0ffb32a_t.jpg
That is the 12inch CV along side for comparison.
I hear what your'e saying but remember;--- I already own these drivers ; also I like experimenting.
Also you have to remember that in the end I will probably need at least 3 * 15 inch to give me the SPL down below 40 that I need to keep up with my new speakers.
I'm actually looking at all alternatives for that bottom octave, definitely keeping the big 15 sealed box.
If you can point me to a driver that is 98dB at 20Hz i'd appreciate it, although I probably can't afford it
Also you have to remember that in the end I will probably need at least 3 * 15 inch to give me the SPL down below 40 that I need to keep up with my new speakers.
I'm actually looking at all alternatives for that bottom octave, definitely keeping the big 15 sealed box.
If you can point me to a driver that is 98dB at 20Hz i'd appreciate it, although I probably can't afford it
Moondog55 said:
Agreed. I am running 92db. As mentioned earlier. I am covering the lack of 6db compared to my 98db full-range drivers with a higher gain on the woofer amps. It's a compromise.
Still probably 10db more SPL than yours at 8Ohm.
I20-40 should be covered by a closed or vented design. (If you really need it - see Linkwitz) This way you are much more flexible on the Dipole side.
With e.g. Behringer DCX 2496 you can also put some extra juice on the lower range 35-50 if you like.
Cheers
Eminence or Monacor?
In need of advice.
I can buy the following cheap 12" drivers at the moment.
Eminence Michaelis 12/400l
and
Monacor SP302 e
The Eminence is 105db (I like that!!!!) the Monacor "only" 95db The problem with the Eminence is the lack of more driver specs (must be a very old model).
Thank you Peter
In need of advice.
I can buy the following cheap 12" drivers at the moment.
Eminence Michaelis 12/400l
and
Monacor SP302 e
The Eminence is 105db (I like that!!!!) the Monacor "only" 95db The problem with the Eminence is the lack of more driver specs (must be a very old model).
Thank you Peter
Eminence is a kappa (maybe not suitable)
Just found out that this is a Kappa from the 70's model. Rebranded in Holland.
on the Eminence website you can see the specs.
http://www.eminence.com/pdf/kappa-12a.pdf
the fs seems to be quite high (45 Hz) and xmax too small 3,5mm. Eminence states that their xmax specs are very conservative though!!
It does have a hugh motor!!!
Just found out that this is a Kappa from the 70's model. Rebranded in Holland.
on the Eminence website you can see the specs.
http://www.eminence.com/pdf/kappa-12a.pdf
the fs seems to be quite high (45 Hz) and xmax too small 3,5mm. Eminence states that their xmax specs are very conservative though!!
It does have a hugh motor!!!
How about the Visaton WHC 30 X at conrad.nl for 40 €? Looks like it has got good parameters.
Regarding Fs please keep in mind that a ripole configuration can reduce Fs of the system quite substantially. And please don´t judge with the stated efficiencies. They are specified for 1 kHz and won´t say anything for 50 or 100 Hz without comparing the individual Qts values.
Regarding Fs please keep in mind that a ripole configuration can reduce Fs of the system quite substantially. And please don´t judge with the stated efficiencies. They are specified for 1 kHz and won´t say anything for 50 or 100 Hz without comparing the individual Qts values.
determinimg spl near fs, below rated hz
Rodolf mentioned the need to "compare Qts" in order to determine the spl of a driver below the manufacturers rated spl, which was done at 1000 hz. What is the proceedure to do this computation for 27 hz? Example: Uframe type dipole, per Martin King; using a 15" diameter driver, fs=25hz, SPL=95db at 1000 hz, Qts=0.927, Qes=1.081, Qms=6.498, Xmax=6.3mm, Vas=192.84L, Imp=8ohms, Re=7.2, Le=2.56, Bl=15.22.
Rodolf mentioned the need to "compare Qts" in order to determine the spl of a driver below the manufacturers rated spl, which was done at 1000 hz. What is the proceedure to do this computation for 27 hz? Example: Uframe type dipole, per Martin King; using a 15" diameter driver, fs=25hz, SPL=95db at 1000 hz, Qts=0.927, Qes=1.081, Qms=6.498, Xmax=6.3mm, Vas=192.84L, Imp=8ohms, Re=7.2, Le=2.56, Bl=15.22.
Michael,
for calculating the real SPL for a driver in a cabinet (or an OB) you will need a simulation program. For the driver on IB (or IEEE baffle) you can calculate the SPL loss resulting from low Qts from this diagram:
The vertical axis is showing the relative SPL values compared to the 1 kHz standard.
Horizontal axis is for the Fs of the driver. 1.00 means Fs, 2.00 means 2x Fs, 0.50 means 0.5 x Fs etc.
for calculating the real SPL for a driver in a cabinet (or an OB) you will need a simulation program. For the driver on IB (or IEEE baffle) you can calculate the SPL loss resulting from low Qts from this diagram:
The vertical axis is showing the relative SPL values compared to the 1 kHz standard.
Horizontal axis is for the Fs of the driver. 1.00 means Fs, 2.00 means 2x Fs, 0.50 means 0.5 x Fs etc.
Re: About distance
AFAIK Axel Ridtahler places his own ripoles with 30-50 cm "air" behind. 50 cm would be fine so.
Ciu said:
AFAIK Axel Ridtahler places his own ripoles with 30-50 cm "air" behind. 50 cm would be fine so.
I just got one idea about construction of dual RiPol with two 18" Pro drivers. The location of drivers is shown on the picture. I guess that the width (depth?) of the side chambers could be only half of the middle one. It seems that these two 18" drivers with diameter 460mm and overall depth 176mm can be squeezed into fairly compact cabinet with outer dimensions H x W x D = 840 x 330 x 500 mm. Such cabinet can be used as a stand for a Mid-Hi section. What do you think? Could the height of the cabinet become a problem because of standing waves?
Then I have got another thought about depth of the chamber in front of the driver. Regarding the fact that narrow chamber provides an additional load to a driver, should we then make the condition when rear and front loads are symmetrical? I suggest to run driver with high amplitude at low frequency via resistor and then to check on the scope if current being consumed by a driver is the same in both directions. If not then size of front chamber should be adjusted accordingly. Any thoughts?
Then I have got another thought about depth of the chamber in front of the driver. Regarding the fact that narrow chamber provides an additional load to a driver, should we then make the condition when rear and front loads are symmetrical? I suggest to run driver with high amplitude at low frequency via resistor and then to check on the scope if current being consumed by a driver is the same in both directions. If not then size of front chamber should be adjusted accordingly. Any thoughts?
Attachments
Some aspects to consider:
If calculating the front and rear loads of your drivers, the air bounded by the loudspekaker cones has to be added to the outer chambers and has to be subtracted from the inner chamber. Since the cones make up a large part of the volume of the inner chamber, it needs to be significantly larger.
If the drivers have vented pole pieces, these vents will work into chambers with opposite pressure relations. This could be an issue.
The height of the cabinet could not become a problem because of standing waves. The only standing wave (quarter wavelength) will develop along the depth of the cabinet.
Making the front and rear loads symmetrical looks like a good idea, but what about making the front and rear excursion from the idle position symmetrical? The second looks like an even better idea, but does not imply the first automatically IMHO.
If calculating the front and rear loads of your drivers, the air bounded by the loudspekaker cones has to be added to the outer chambers and has to be subtracted from the inner chamber. Since the cones make up a large part of the volume of the inner chamber, it needs to be significantly larger.
If the drivers have vented pole pieces, these vents will work into chambers with opposite pressure relations. This could be an issue.
The height of the cabinet could not become a problem because of standing waves. The only standing wave (quarter wavelength) will develop along the depth of the cabinet.
Making the front and rear loads symmetrical looks like a good idea, but what about making the front and rear excursion from the idle position symmetrical? The second looks like an even better idea, but does not imply the first automatically IMHO.
Yes Rudolf, I would agree with you that exhaust from a pole vent goes in the wrong direction. BTW it looks that double-stocked RiPol has the same design: If stacked is the preferred method then the front cover (market blue in the picture) of the top Ripole needs to have a cut-out of 182 mm diameter (marked red in the picture) to accommodate the driver's magnet of the lower RiPole.
That sure doesn't make it right. However there seems to be fairly easy way of fixing that issue: rears of magnet assemblies need to be enclosed in separate chambers that vented into the center one. Please see the updated picture below. Also this design can allow using drives with pole vent noise issue as enclosures can be stuffed with sound absorbing materials.
