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Multi-Way Conventional loudspeakers with crossovers

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Old 8th February 2007, 03:33 PM   #1
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Default Still having great trouble with my Scanspeak build

I was hoping to be able to tell you all about my latest loudspeaker build, and share my ideas and experiences, as many of you have helped me resolve many aspects, aiding me in this project. Unfortunately, having completed my loudspeakers to-design and run them in for a couple of months, they still sound fairly horrid (relative to my expectations).

The story so far: Roughly a year ago, I decided that I wanted some top end loudspeakers to go with some Musical Fidelity kit. I previously had some KEF 104/2s which I decided were going to be too difficult to diy update. In those days I was not familiar with the diy sites belonging to passionate and talented individuals such as Troels, Zaph, and Tony. I had found kits at lautsprechershop.de and ended up purchasing a small two-way monitor kit from AOS, the Studio 12XL. This is a 12 litre vented cabinet design using the Scanspeak 15W/4531G and the R2904/7000. See http://www.aos-lautsprecher.de/indexE.html

Upon completion, I was stunned by the seamless coherence of the speakers and their dramatic punchy bass, but I did not like the cold sound of them. Axel Oberhage the owner/operator of AOS suggested changing the midwoofer inductor from 1.6mH to 1.8mH, or alternatively he would switch the 15W units for 18Ws and supply crossover changes. I would then have to build new cabinets.

I was slightly put off standmount speakers by now, so I chose to build a pair of Studio 35XL floorstanders. I have now completed these with some beautiful cabinets, but oh no... There is lots of lovely warmth, but all the other good aspects of the Studio 12s have dissapeared. The sound is not seamless and is not coherent. The midrange sounds deadish and dull and unlively.

Please help?

I have attached photos of the speakers, the crossovers, and the XO schematic. For cabinet drawings please see the german section off http://www.aos-lautsprecher.de/indexE.html.

The HF unit is still the R2904/7000, the L/MF unit is the 18W4531G.
The cabinet is a bass reflex design of 42.5 litres with a Jetline 60 port of 145mmx60-53mm.
The crossover point is 2,200hz and it is a 6dB filter.

An Ideas?

I could always try Tony Gee's Optimo crossover from http://www.humblehomemadehifi.com/Optimo.html , which uses exactly the same drivers and maybe build some of Tony's transmission line cabinets, but I would like to ask the forum for some help and opinions first.
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Old 8th February 2007, 03:34 PM   #2
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Old 8th February 2007, 03:37 PM   #3
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Schematic
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Old 8th February 2007, 03:43 PM   #4
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The XO components are a bit blurry, so here they are in print:
Midwoofer Inductor 1.8mH 1.4mm (0.43ohm). I used a Mundorf CFC14 which is only 0.32ohm as directed by AOS.
Then on the tweeter circuit a 3.3ohm resistor, a 5.6uf cap, and 1.2ohm resistor on the tweeter which is reverse phased. There is a notch filter between the cap and second resistor consisting of a 3.9 ohm resistor, 6.8uf + 8.2uf caps and a 1.0mH (1.39ohm) inductor going to the return.

PLEASE HELP.
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Old 8th February 2007, 10:38 PM   #5
MadMutt is offline MadMutt  Australia
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looking at that xover, I'm not suprised it sounds like ****.

I would suggest going to troels site and having a look around.
He's done quite a few Scan designs and his xovers look just a bit different.

http://www.troelsgravesen.dk/8542.htm

Not the exact same bass driver, but should be a good starting point.

Edit,
that link isn't right either, wrong tweeter too.
He's done (from memory) 1 or 2 designs with that 7000 tweeter, and it sounds like a pain to work with.
Quite frankly, I would have never chosen that combination of drivers, it's just asking for trouble.

Oh, for what it's worth, I've built his Ektas using a 9500 tweeter and they are increadible....
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Old 8th February 2007, 10:58 PM   #6
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If I could go back 12 months, I would build Ektas too.
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Old 9th February 2007, 02:49 AM   #7
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Hey, you're lucky, seems like a no brainer solution here. Build the crossover for the Optimo and drop it in. The speaker uses the exact same drivers and the cabinet width is almost identical (looks like 230mm vs. 240mm) so baffle step will be almost the same. The only difference I can see is that you've built a bass-reflex with different cabinet volume/tuning and the Optimo is a TL. This should only effect the low-end response of the mid-woofer, so it won't sound the same as the Optimo as far as bass response, but the crossover should still be a perfect fit because it doesn't attempt to equalize bass response. Seriously, I think this is not a big problem at all, assuming the Optimo sounds good.
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Old 9th February 2007, 10:29 AM   #8
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Well, one difference then. Your cabinets tilt and it looks like Tony's crossover introduces a 90 degree phase shift on the tweeter relative to the woofer by using asymmetrical crossover slopes and reversing the polarity of the tweeter in an attempt to phase align the two drivers. I'm not sure how large of an offset between the two drivers your tilt introduces, but Tony's crossover might not provide proper phase alignment considering your cabinet tilt. Then again, his crossover may not have fully compensated for the phase mis-alignment and your tilt could make them sound even better. It's really hard to say without knowing all of the details, but when/if you build this crossover try listening to it with the tweeter's polarity reversed and with it normal. You may get interesting results.
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Old 9th February 2007, 11:26 AM   #9
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Motion: Thank you for your input.

I have purchased all the parts for the Optimo XOs today.

It is simple enough to tilt the speakers forwards the 5 degrees that they are currently reclined. Incidentally I built my existing cabs with a recline for largely aesthetic reasons. With the close proximity of the tweeter and the 18cm unit, they would have needed to be tilted back well over 10 degrees for proper time alignment (which would look silly IMO).

I was hoping that someone might run some figures to suggest the lack of success of this design.

I will of course let you all know the outcome with the Optimo XOs.

I can't see why having the HF unit below the 18W on the baffle would affect crossover requirements. Am I wrong?
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Old 9th February 2007, 12:21 PM   #10
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Quote:
I was hoping that someone might run some figures to suggest the lack of success of this design.
If you'd really like to know you should do some measurements.
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