Yes, I think so. Only at the lower frequencies though since the le is very low on those drivers and so after the impedance peak at fs it converges to 8 ohm per coil. You'd have to be careful not to exceed xmax though, but except at 40 hz and below that shouldn't be an issue if I remember correctly.
OK.
Now i am finally playing with them in 8 ohm configuration.
They sound very dynamic, open, clean and the bass is deep and has slam. I can hear details with drums etc i never had heard before. It is fun to listen.
This is definitely high end. I am very satisfied. THX John keep up the good work
Now i am finally playing with them in 8 ohm configuration.
They sound very dynamic, open, clean and the bass is deep and has slam. I can hear details with drums etc i never had heard before. It is fun to listen.
This is definitely high end. I am very satisfied. THX John keep up the good work
Dipole Selection
I look for low Le, specifically Le/Re. The Le is the limiting factor on high frequency extension and "jerk", the third derivative of displacement. Since pressure is proportional to acceleration, this is necessary for good transient response and integration with the midrange driver.
I look for low Le, specifically Le/Re. The Le is the limiting factor on high frequency extension and "jerk", the third derivative of displacement. Since pressure is proportional to acceleration, this is necessary for good transient response and integration with the midrange driver.
I have some problems understanding/accepting that low Le in itself is important for transient behavior. It is true that Le limits the upper frequency, but when the driver is bandwidth limited by a XO the Le value should not matter. Fourier's law will apply to the system.
However, I believe Le(x) can be of importance - variation of Le vs displacement. The speaker will show off different transient (bandwidth) behavior with different sound pressure levels or for that matter, dynamic in a recording. In this context low Le may be beneficial as %-age variations in Le vs. displacement have lower influence on the XO filter/end result.
Or I might be wrong...
The wiring of the VC in series with drivers in parallel will give an 8ohm overall impedance. At 8ohm you only need to deliver about 100W to the pair of woofers at 25hz to reach Xmax and about 150W at 30hz. Above those frequencies the efficiency goes up due to the baffle so you shouldn't need to apply more power than this. As long as your amplifier puts out that amount of power, that is the method I would choose.
In regards to inductance, it is linear inductance with respect to excursion more so than low inductance that is the issue. The issue though is that high inductance is usually an indication that nothing is done to linearize inductance. The other issue is back EMF created as the VC moves through the gap. As the VC is energized it becomes an electromagnet that moves or modulates the permanent flux field. The more windings there are, the stronger this electromagnet is and the more flux modulation there is. Reducing both Le(x) and Le(i) are critical. Addressing only one is less effective.
A voicecoil is like an inductor. An iron core inductor can have the same windings as in an air core inductor, but magnitudes higher inductance. This is what happens in a typical voice coil. If you measured the inductance sitting on a bench it would be very low. Putting it around the pole makes it become an iron core with the pole as the core.
The full copper sleeve put on the pole then lowers the inductance back down to that of an air core. It makes the VC a much weaker electromagnet reducing Le(i) and gives perfectly linear Le(x) as well.
Compare the Le(x) results for the TD12M here:
https://sites.google.com/site/drive...ts/tang-band-75-1558se/ae-speakers-td12m/le-x
to the Le(x) for drivers that do not address this issue like the GPA/Alted 414 here:
https://sites.google.com/site/drivervault/driver-measurements/tang-band-75-1558se/gpa-altec-414/le-x
You can see the Altec is a very reactive load where the impedance curve changes wildly with excursion. The TD12M however doesn't do that at all. This is the case for all the TD woofers. The Dipole and LO woofers have the additional advantage of the underhung motor with a nice flat Bl curve as well. This further makes them ideal for open baffle use.
In regards to inductance, it is linear inductance with respect to excursion more so than low inductance that is the issue. The issue though is that high inductance is usually an indication that nothing is done to linearize inductance. The other issue is back EMF created as the VC moves through the gap. As the VC is energized it becomes an electromagnet that moves or modulates the permanent flux field. The more windings there are, the stronger this electromagnet is and the more flux modulation there is. Reducing both Le(x) and Le(i) are critical. Addressing only one is less effective.
A voicecoil is like an inductor. An iron core inductor can have the same windings as in an air core inductor, but magnitudes higher inductance. This is what happens in a typical voice coil. If you measured the inductance sitting on a bench it would be very low. Putting it around the pole makes it become an iron core with the pole as the core.
The full copper sleeve put on the pole then lowers the inductance back down to that of an air core. It makes the VC a much weaker electromagnet reducing Le(i) and gives perfectly linear Le(x) as well.
Compare the Le(x) results for the TD12M here:
https://sites.google.com/site/drive...ts/tang-band-75-1558se/ae-speakers-td12m/le-x
to the Le(x) for drivers that do not address this issue like the GPA/Alted 414 here:
https://sites.google.com/site/drivervault/driver-measurements/tang-band-75-1558se/gpa-altec-414/le-x
You can see the Altec is a very reactive load where the impedance curve changes wildly with excursion. The TD12M however doesn't do that at all. This is the case for all the TD woofers. The Dipole and LO woofers have the additional advantage of the underhung motor with a nice flat Bl curve as well. This further makes them ideal for open baffle use.
This is my bass amp a Musical Innovation 2x50 Watt class A made by mr Roar Malmin.
It has 2x500VA and 200.000 uF.
The active crossover (First Watt B4) is at 160hz Linkwitz Riley 24db. I dont use any kind of EQ.
John, do you think a higher crossover point will provide more slam in the midbass?
It has 2x500VA and 200.000 uF.
The active crossover (First Watt B4) is at 160hz Linkwitz Riley 24db. I dont use any kind of EQ.
John, do you think a higher crossover point will provide more slam in the midbass?
-2 LO15's then per side, OR a different design.
The very best bass you'll get is in the NEAR-FIELD (..if only one sub positioned very near and just behind your head with the appropriate delay for proper summing.)
It will give you these properties (assuming you sit right next to them):
1. substantially more "efficient" at lower freq.s regardless of design, but particularly well suited to a dipole/ripole/cardiod.
2. substantially more linear - with less influence from standing waves.
3. greater tactile sensation (..upper bass "punch", and lower bass "slam"). It also allows the use of drivers that have these qualities that might otherwise be a poor choice for a more typical application.
The common aesthetic I mention for such a "sub" is an "end-table" behind your listening chair or sofa, OR if stereo and only using a chair - a pair of side tables to the left and right of the chair.
Figure about a 2 foot distance to the closest "edge" of the driver (or closest driver) - the closer, the better.
Sorry, a bit OT and old but I found this thread searching on dipoles and joined just to vehemently agree with this post.
Inspired by Martin King's wonderful write-ups and John Reekie's article on nearfield dipole subs I decided to give it a go and am glad I did. I'm just using a simple H-frame for an Alpha 15A per Martin's dims in the nearfield it's the best bass I've experienced. I have a very difficult, small, cinderblock room which is a modal nightmare. With this thing bringing up the rear, though (see pic), it's incredible. I get excellent depth (below 40Hz or so, anyway, which is fine for my music) along with a punch and bass-drum-head-thwak-in-the-chest that I haven't experienced before. It's...awesome. FR at my seat is utterly flat in the upper bass and ringing is negligible. It's crossoved over at 80Hz, 24dB/oct via my Denon 4310. If I have it to the side I can somewhat place it but if it's directly behind, all bass is solidly placed up front. 
So now I'm drooling over an AE Dipole 15, of course, so see how much better things can get.
Post the 3D dimensions for your room(s) so we can look/verify. (Not so important) At the same time and if you're doing this, post construction material for both floor and ceiling as a complete report add up for your Listening Room.
John,
When doing critical info on drivers (T/S specs of that kind) is very important for fair reference to mention more technical details like the frequency that the measurements where made so that we (and others) make sure we can compare apples with apples. You know a lot has being said about technical conditions for measurements for other brands and what is a standard and what is not and the great amount of manufacturers that don't mention this fact (or any other detail/condition) or spec in their driver spec sheet. The Le curve is one of the specs that changes exponentially, so I would be very careful just to make sure, I would feel infinitely more comfortable.
Hi! The dimensions are 13' L x 10.5 W x 6.8' H. 3 walls are drywall over cinderblock, one short wall is drywall/metal studs. Floor is concrete, ceiling is drop acoustic tile under the wooden floor of the 1st floor. A couple 34" face "superchunk" mineral wool traps in the front corners, a few 4" thick 2'x4' at the side reflection points.
Here's a waterfall I ran for just the sub from the listening position (that chair). I think that ringing at ~40Hz is the axial mode as that's still being excited given that's the axis the sub is pointing along :
Thanks!
That is one of the sickest in-room responses I've seen...!
Could you provide details for that measurement please (smoothing, gating, window etc). What is the distance from the H-frame to the mic and the rear wall?
Is this without any DSP or bass traps? Have you measured GD, ETC and RT60?
Add a couple of GIK Acoustics Scopus T40 or a helm-holtz absorber tuned at 40 Hz and you should be set! Perhaps EQ flat down to Fs and HP as long as you fell you have the SPL headroom to do so.
I would make sure also that the advantage of having the sub that up close is not mitigated by having early reflections from the mains.
Could you provide details for that measurement please (smoothing, gating, window etc). What is the distance from the H-frame to the mic and the rear wall?
Is this without any DSP or bass traps? Have you measured GD, ETC and RT60?
Add a couple of GIK Acoustics Scopus T40 or a helm-holtz absorber tuned at 40 Hz and you should be set! Perhaps EQ flat down to Fs and HP as long as you fell you have the SPL headroom to do so.
I would make sure also that the advantage of having the sub that up close is not mitigated by having early reflections from the mains.
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THIS IS NOT A DIPOLE
I'm just going to pop in to all the threads where JackG3 posted about his wonderful dipole and remind everyone that it isn't a dipole from where he is seated. I am doing this to quell any confusion that he might be generating.
He is sitting in, and measuring from, the near field. That is why his response plots don't show any room resonances, none, zip, zero. All thanks to the near field response dominating over the room response. His setup indeed provides the clean and visceral bass that he describes (at least down to 30-40Hz) but it's essentially the infinite baffle closed box response that he is getting frmo the driver. This explains not only the frequency response, but also the waterfall (note the ringing at 40 Hz from the high Qts?) and the lack of any room modes in his measurements (near field dominates the room response).
There is no need to over analyze this situation. If you put your ears near the radiator (of sound) you will get these effects. If my wife would let me put a large speaker right behind my head in our living room, I would do it too!
I'm just going to pop in to all the threads where JackG3 posted about his wonderful dipole and remind everyone that it isn't a dipole from where he is seated. I am doing this to quell any confusion that he might be generating.
He is sitting in, and measuring from, the near field. That is why his response plots don't show any room resonances, none, zip, zero. All thanks to the near field response dominating over the room response. His setup indeed provides the clean and visceral bass that he describes (at least down to 30-40Hz) but it's essentially the infinite baffle closed box response that he is getting frmo the driver. This explains not only the frequency response, but also the waterfall (note the ringing at 40 Hz from the high Qts?) and the lack of any room modes in his measurements (near field dominates the room response).
There is no need to over analyze this situation. If you put your ears near the radiator (of sound) you will get these effects. If my wife would let me put a large speaker right behind my head in our living room, I would do it too!
A little update.
AE-LO15 with custom rubber surround is still playing marvelous dry and detailed bass in my 17m2 listening room.
I use Sonos->Dac-Pass Labs XP10:
High Pass, XLR out from XP10 to XA30.5:
- passive 6 dB high pass at 300 Hz / low pass 12 dB 300 Hz to JBL2119 8"
- 3000 Hz 18 dB to Radian 475 beryllium 1" in Autotech Tractrix 1000 horn
Low pass, RCA out from XP10 to First Watt B4mkII to XA30.5 to AE-LO15. First Watt B4mkII is low passed active 24 dB at 300 Hz, no EQ
It sounds smooth, dry, detailed, dynamic, with slam and almost full range in my room.
AE-LO15 with custom rubber surround is still playing marvelous dry and detailed bass in my 17m2 listening room.
I use Sonos->Dac-Pass Labs XP10:
High Pass, XLR out from XP10 to XA30.5:
- passive 6 dB high pass at 300 Hz / low pass 12 dB 300 Hz to JBL2119 8"
- 3000 Hz 18 dB to Radian 475 beryllium 1" in Autotech Tractrix 1000 horn
Low pass, RCA out from XP10 to First Watt B4mkII to XA30.5 to AE-LO15. First Watt B4mkII is low passed active 24 dB at 300 Hz, no EQ
It sounds smooth, dry, detailed, dynamic, with slam and almost full range in my room.
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I have a new idea and wonder if you John, and others, have some suggestions and experience here.
A simple two way solution crossed over at ca 800 Hz:
Stereo-Lab Tractrix 400 horn: 1.5 inch cf 400Hz Wave Guide Tractrix Horn lower physical cut-off fre
JBL D2:
D2 Dual Diaphragm Dual Voice Coil Compression Driver
A simple two way solution crossed over at ca 800 Hz:
Stereo-Lab Tractrix 400 horn: 1.5 inch cf 400Hz Wave Guide Tractrix Horn lower physical cut-off fre
JBL D2:
D2 Dual Diaphragm Dual Voice Coil Compression Driver
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