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Old 23rd February 2006, 01:25 PM   #1
Nuuk is offline Nuuk  United Kingdom
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Default Dipoles (continued)...

The story far:

I had a pair of Goodmans 201's that I used in a larged ported box and one day thought 'why not try them in an open baffle'.

Click the image to open in full size.

Being very pleased with the way they sounded, I knocked up some better baffles.

Click the image to open in full size.

The only thing missing was a bit more 'bottom end'. So I added some passive EQ and that improved matters but I still wanted more. So I built some TL woofers

Click the image to open in full size.

and voila - it all sounds divine!

But like everybody else on these forums, I couldn't possibly be satisfied and anyway, those huge TL's take up so much space. What to do next? Well try some open baffle woofers of course and at the end of last year, an offer that I couldn't refuse, tempted me to buy four 12 inch bass drivers. Since Christmas I have been knocking up some new protype baffles from an old wardrobe, a pack of laminate flooring and some bits of my mates stack of firewood. Here is the result.

Click the image to open in full size.

Click the image to open in full size.


Right, that the end of the entertainment, now for some questions!

Now, I know that I could use something like a Behringer DCX2496 to control the woofers (and mid/tweeters) but I can't really afford one right now (even if they were available). So I am looking for something that I can build to get me going. The two options I have found so far are the circuits on the Siegfried Linkwitz site and the circuit designed for the Contrapunt sub .

The second of those two options looks easier to build but I am confused by the circuit diagram.

Click the image to open in full size.

It says 110 Hz on the diagram but according to my calculations the woofers cross over at around 76 Hz and the main drivers (ESL's in this case) have a cut off around 300 Hz.

So can anybody suggest if this circuit would work reasonably well with my new baffle/woofers and explain how it is a 110 hz crossover?

Or is there something else out there that I can use? I'm sure that I am not the only one on this road so let's more forward together.
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Old 23rd February 2006, 01:46 PM   #2
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I have never seen this kind of arrangement, how does this circuit control the drive unit?

Does this not make the woofer flap with low bass?

Its looks very well made.
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Old 23rd February 2006, 02:51 PM   #3
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How Nice!

I can't help you on the circuit (I'd buy a DBX or Behringer) but just wanted to say I LIKE the design.

What bass drivers are you using, what path length, etc...?

Very cool.

Please post your final results.

Ribbon Project
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Old 23rd February 2006, 03:11 PM   #4
sreten is offline sreten  United Kingdom
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Default Re: Dipoles (continued)...

Quote:
Originally posted by Nuuk

It says 110 Hz on the diagram but according to my calculations the woofers cross over at around 76 Hz and the main drivers (ESL's in this case) have a cut off around 300 Hz.

So can anybody suggest if this circuit would work reasonably well with my new baffle/woofers and explain how it is a 110 hz crossover?

Hi,

Seems to me you are not considering the combined acoustic
response of the sections and the electrical response of the c/o,
combined c/o is at 110Hz, electrically it is not.

Without modification it is not suitable for your case.

Check out JK's NaO.

http://www.musicanddesign.com/naofaq.html

/sreten.
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Old 23rd February 2006, 03:39 PM   #5
Nuuk is offline Nuuk  United Kingdom
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OK thanks for the compliments. I must state that the design was inspired after seeing Icebear's OB's . In fact I cut out four curved side panels like his but just didn't like them so I went for the straight line approach instead.

I will be writing up this project on Decibel Dungeon and hope to be able to include full details.

Woofer drivers are Max Pentivent 1230's from Nightfire here in the UK although I think that they are available the other side of the Atlantic too!

Sreten, thanks for your comments. I am still at the stage of taking crossover circuits 'literally' and not being able to work out how they work in practice. I had contacted John at Nao but he advised me correctly that I would need to measure the system before proceeding.

Obviously, the advantage of the Behringer (disregarding and potential sound degradation) is that a novice like myself can fiddle around until he gets to some arrangement that sounds good.

Things were a lot easier with the TL woofers but of course they didn't require any EQ!

Iron Wizard, as I said, I will publish full details in due time. The woofer cabs are 35 cm deep, 55 cm high and 38 cm wide.

Click the image to open in full size.
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Old 23rd February 2006, 03:45 PM   #6
AJinFLA is offline AJinFLA  United States
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Do you already have amplification for the sub section? If not, this gentleman can provide a plate amp with a LT for your dipole eq. http://www.rythmikaudio.com/lt.htm
Your cabinet my have enough asymmetry where you don't have to notch your dipole peak, the plates low pass filter may suffice.
http://www.rythmikaudio.com/nonservo...t.htm#250basic
Perhaps someone has something similar in the UK?
Hopefully you have measurement capability. I always assume this about anyone building their own speaker design, much less dipoles!

Cheers,

AJ
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Old 23rd February 2006, 04:07 PM   #7
Nuuk is offline Nuuk  United Kingdom
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AJ - I have four LM3886 GC amps ready for this job!

I thought that the Linkwitz transform circuit was for sealed box woofers. But it's a neat idea providing something like that circuit in a plate amp. Presumably though I have to know what values of components I will need.

Now when it comes to measuring I only have my RS digital meter that I know is a bit unreliable at the frequency extremes. Perhaps I have been lulled into a false sense of security by getting my TL woofers set up so well, but I was hoping that I could do the same with OB woofers!
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Old 23rd February 2006, 08:09 PM   #8
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Nice inspiration for us all Nuuk

dave
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Old 23rd February 2006, 08:47 PM   #9
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Thanks Dave. Inspiration is one of the best aspects of these forums. I wonder how much more DIY goes on in the world since diyAudio and other hi-fi forums sprang up!

I really started making these speakers as no more than testbeds that wouldn't look too bad in my lounge if it took a few months or so to sort out the crossovers etc. Hence the frugalphile ingredients. But if I'm honest, they have come out much better than I expected!

But I don't know if I would use the same method of construction again! The laminate flooring is pre-finished and it is ultra-easy to damage it during construction. Next time it will be 3/4 inch (22 mm) thick board and a veneer!

BTW, the side panels are bolted to the front panel so it all comes apart for storage or transportation!
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Old 25th February 2006, 07:48 PM   #10
Ropie is offline Ropie  United Kingdom
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Nuuk, those look superb. I wish I could be of help but..

Knowing that everything you do gets written up in detail at DD should inspire someone with knowledge to assist you.
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