[MJK]

I have been busy the past couple of months designing, building, and testing a new two way dipole speaker system. The resulting speaker has an efficiency of 88 dB/W/m and covers the full spectrum from 20 Hz to 20 kHz. You can find pictures and the documentation of the design on the Projects page of my web site.

Martin

[jkelly]

Very exciting.  Drivers ordered.  Looks like a great fall project.

Thanks,

Jeff

[mcgsxr]

Wow, thanks for sharing, that is going to be a ton of fun for people!

[richidoo]

Very cool article Martin, Thanks!  Nice to see an active OB design designed using your software. I found the non-symmetrial driver location on the baffle worked well for me too, just as your sim software predicted.

[zipidachimp]

pardon the doofus question:  how do you connect the 4 binding posts shown to the 2 on my receiver?

[Rudolf]

Very well done, Martin

I just want to show, what I have done recently along the same lines.
Not to hijack this thread, but as a confirmation and to emphazise how much this concept has to offer.



I have opened another thread for a description of my system, so please refrain from discussing it here.
http://www.audiocircle.com/index.php?topic=59633.0

A question to MJK:
I did not find a real difference between positioning the OB on the middle or on the front of the H frame. For aesthetical reasons I put mine to the front. Would you see any reasons to not do so?

Rudolf

[MJK]

how do you connect the 4 binding posts shown to the 2 on my receiver?

Unfortunately, to use this system you need to bi-amp using an active crossover. I use the dBx Driverack Pro but the Behringer DCX would also work. The signal path is shown below.

Source
|
|
V
Preamp
|
|
V
Active Crossover
|                    |
|                    |
V                   V
Amp               Amp
|                    |
|                    |
V                   V
Jordan            Goldwood

I don't know of a way to make a reciever work

Sorry,

Martin

[MJK]

A question to MJK:
I did not find a real difference between positioning the OB on the middle or on the front of the H frame. For aesthetical reasons I put mine to the front. Would you see any reasons to not do so?

Rudolf,

Looks like we are on parallel paths! That is a good sign.

I am not sure that the exact locations of the OB on top of the H frame is that critical, at these low frequencies a couple of inches seems kind of insignificant. I have not tried moving mine back and forth yet, I am still in the early phases of listening and fine tuning. The big tuning is done so the little tweaks will string along over the next few months. So many interesting things to try and not enough time is my biggest problem.

I look forward to seeing more about your speakers,

Martin

[jkelly]

Martin,

If I was willing to give up on the separate toeing of the OB - what problems
would I run into if I made a single unit approx 40 x 20 with a H on the bottom
part and the OB on the top?  do they need to be isolated?  Should I be worried
that the OB will be vibrating off the H woofer?

Jeff

[zipidachimp]

mjk: thanks for the reply. shows how much I have to learn!
another doofus question:  if you replace the preamp/a-c/amps with a receiver and passive x-over,  what difference in the sound would you expect to hear, or is this design only relevant to bi-amping?  i'm playing with my own versions of your designs and they are already superior to my purchased speakers. i'm really new to this

[scorpion]

MJK and Rudolf,

OK lads, this is not quite seriously intended, although the simulations all are to the point. May be you can spot the difference ?

I would say that you are constantly unaware of these fundamental differencies as the next three pictures show:







and I look forward to your explanation of this  phenomenon. Do they matter and if why ? 

Hint: 2 x Alpha15s in an H-dipole like MJK's only double height.

And Martin when going with a classy fullranger why not also go with a classy bass-unit like the Acoustic Elegance Lambda Dipole 15 as presented a bit inside this thread: http://www.aespeakers.com/phpbb2/viewtopic.php?f=3&t=536 . It will simulate like this in the H-dipole:



But there are 12 millimeters to go in X-max.

/Erling

[Rudolf]

I would say that you are constantly unaware of these fundamental differencies as the next three pictures show:
...and I look forward to your explanation of this  phenomenon. Do they matter and if why ? 

Hint: 2 x Alpha15s in an H-dipole like MJK's only double height.

Erling,
since when are you able to simulate stacked frames with the worksheets? I see virtually no differences below 100 Hz and only minor ones above. I have no cue.

[MJK]

Erling,

I have no idea what the small differences in the simulations mean. Maybe you need to supply some more details.

I looked at the AE Dipole 15, the specs look impressive. But the price was shown as $249 each. The $129 (or 4 for $100) is for the AE IB 15 which has a lower Qts. So if we used one of the AE drivers, we would need EQ plus boost for the IB 15 or just boost for the Dipole 15. If we did that right we could approach the performance of the $60 Goldwood or Alpha 15A drivers. Why would we spend more money and jump through more hoops to get to the same place? Since the driver only works from fs to 100 Hz, I am not convinced that paying more is going to dramatically increase the bass quality or quantity.

Martin

[scorpion]

Hi Guys,

No problems, The three simulations was with baffle .33 , .50 and 0.67 of the H-dipole length, and yes it doesn't really matter but the 1st choice falls off very good with respect to the 12 db/octave specs.

Rudolf, MJK himself has this proposal: http://www.quarter-wave.com/General/Two_Drivers.pdf

In fact MJK I have purchased a pair or IB15s which together with other people here in Sweden  we are able to import for about 150 $ each unit. These I intend to use for IB and for U-dipoles. It will be very interesting to see its performance.

[markC]

Off topic a little but, Erling, I use a pair of the PE IB 15's in an IB. They are driven in parallel by a 300W plate amp.
My listening room backs to the crawl space beneath the Living, Dinning and kitchen.
I would desribe the bass as effortless, solid and dynamic. I think you'll like them in IB!

[Rudolf]

The three simulations was with baffle .33 , .50 and 0.67 of the H-dipole length

Sorry Erling,
I´m afraid I don´t fully understand. Do you mean "... was with baffle position at ..." or "... was with baffle width of ..." or what else?

Rudolf, MJK himself has this proposal: http://www.quarter-wave.com/General/Two_Drivers.pdf

I see, but would be cautious: I´m not sure if this is still valid for such big drivers, when one is near the floor and the others center more than 60 cm above.

Rudolf

[MJK]

I see, but would be cautious: I´m not sure if this is still valid for such big drivers, when one is near the floor and the others center more than 60 cm above.

Rudolf,

I had similar concerns until I ran a quick test case. I took one of my OB designs that used two Alpha 15A drivers and and re ran the model using only one large equivalent driver centered at the point between the two real Alpha 15A drivers. While not exactly the same, the resulting SPL response curve very close to the original result. So my conclusion was that the method was not perfect but it was adequate.

Martin

[MJK]

if you replace the preamp/a-c/amps with a receiver and passive x-over,  what difference in the sound would you expect to hear, or is this design only relevant to bi-amping?

If you take the design as it stands now and just add a passive crossover, the bass will be a few dBs less efficient then the full range driver. I worry it will sound out of balance and weak in the low end.

If you really wanted a passive solution, you would have to L-Pad the Jordan down to match the H frame. I guess it could be done but then the system will drop to about 85 dB/W/m. If you have the power it would probably work. I had not really thought about that option.

Martin

[zipidachimp]

mjk: thanks,   I need to learn more!   am I correct that a pair of these needs 4 amplifiers?

[MJK]

am I correct that a pair of these needs 4 amplifiers?

It needs four channels of amplification, so I use two stereo amps. One amp is fed the lows and powers the left and right Goldwood H frames and a second amp is fed the rest and powers the left and right Jordan OBs. The active crossover is the traffic cop and sends the right frequencies to the appropriate amp. I seem to remember someplace seeing somebody using a preamp and a 5, 6, or 7 channel HT amp with an active crossover to accomplish the same thing with one big amp, an interesting and flexible option.

Martin