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Old 13th April 2006, 04:02 PM   #1
Tenson is offline Tenson  United Kingdom
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Join Date: Feb 2006
Location: Kent
Default Crossover help please :)

I have built some speakers using a Dayton 7" aluminium woofer and a Tangband 871 for mid and treble.

I have use the DCX to try different crossover settings and have found what I feel works best. So, I need some help with building the passive version please.

The crossover settings I need are:

Low pass BUT-12 @ 160Hz.
High pass BUT-6 @ 350Hz.

I also want to put a notch filter in for the Tangband but I'm not sure how to translate what I have set on the DCX to a passive filter.. For one, the 'Q' setting doesn't make much sense to me. Normally 1 'Q' is 1 octave. But on the DCX a 'Q' of 4, which is what I am using, is narrower than 1! So please, how do I make a passive notch filter that is the same as the DCX settings of - 'Q' 4, -2.5dB @ 9.66KHz.

I have used the crossover calculator in X-over sim from FRD to work out the components for the standard crossover bits and it says I need the following-

For the low pass the woofers impedance at 160Hz is 7Ohms so an inductor of 9.848mH and a cap of 100.446uF.

For the high pass, the impedance at 350Hz is 8Ohms so a cap of 56.857uF should do the trick.

If someone could double check those for me I would really appreciate it.

Now, the last question, where is the best place to buy these parts in the UK? I believe I can get the custom wound inductors and the caps from Falcon Components. But I am a bit lost as to what sort I need exactly. The speaker is not super high-end so only average components area needed. Also I doubt I can get a cap of exactly 56.857uF and Iím unfamiliar with what the standard ratings are so some help here too please!

Thanks for all the help!
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Old 13th April 2006, 05:49 PM   #2
sreten is offline sreten  United Kingdom
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Location: Brighton UK
Hi,

I recommend you experiment with a series 1st order
crossover for this application, around 200Hz to 300Hz.

Parallel first order crossovers are generally not good, the bass units
impedance rise due to inductance "fights" the crossover, as does the
mid units bass resonance which will be poorly controlled by the series
capacitor. (edit : In fact it will be seriously exacerbated)

A series 1st order c/o puts an inductor in parallel with the mid
unit and a capacitor in parallel with the bass unit, so any rise
in impedance will help the crossover.

Consequently the TB's bass resonance will be far better controlled
and the bass unit will get an overdamped second order roll-off, its
inductance effectively becoming a c/o component.

Its not possible to make a series 1st order with different frequencies.

Q=4 is much narrower than Q=1 in terms of a notch filter,
I'd say a Q=4 - 2.5dB filter is impractical to build passively.

Such a localised filter with - 2.5dB attenuation maximum would not
be particularly audible (unless you know its there - pychoacoustics).

Perhaps the maximum attenuation is more than -2.5dB.

/sreten.
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Old 13th April 2006, 06:54 PM   #3
tinitus is offline tinitus  Europe
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Hi, I think its due time someone does some serious membrane "coating" on those Daytons
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Old 13th April 2006, 07:19 PM   #4
Tenson is offline Tenson  United Kingdom
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Sreten,

So this would give me a first order roll off for the high pass and a second order for the low-pass using the woofer's coil as the inductor?

Just to clarify on it have you got any diagrams or links about such usage?

I agree the Dayton could do with some coating. It sounds pretty bad above about 200Hz, thatís why I chose to crossover so low and sacrifice max SPL.

Why does notch filter 'Q' work differently to normal EQ 'Q'? You are right it is not particularly noticeable but it seems to make the difference between abrasive and nice and lively in the treble. It is not essential though, if you think it would degrade the sound more by having more components in there?

Oh, where can I get some variable L-Pads from nice and cheap? I think the tweeter will need a few dB reduction but I donít know the exact amount as I am running the woofer and tweeter from slightly different amps. Although I level matched them as best as possible I donít want to rely on that.
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Old 13th April 2006, 08:41 PM   #5
tinitus is offline tinitus  Europe
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Maybe if you could remove this phase plug and give it a nice "dustcap"
Then it would be easy to reinforce this critical area and it would also ad some weight - it would possibly do some good
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Old 13th April 2006, 09:00 PM   #6
Tenson is offline Tenson  United Kingdom
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Are you talking about the Dayton? It does have a dustcap - http://www.partsexpress.com/pe/showd...number=295-335

The notch filter is audible and also clearly visible here by the way:

No-Notch filter-
Click the image to open in full size.

Notch filter -

Click the image to open in full size.
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Old 13th April 2006, 11:19 PM   #7
Relax is offline Relax  United States
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Very interested in your XO design. I had planned on these same drivers in a floorstander. Not sure what to do with the XO point though.

I aimed for a higher XO point so I could increase the power handling of the Tangband, because its XMax is the limiting factor in its use as a true fullranger. (For me anyways)

I settled on a 2nd order in the 500-600hz range.

After reading these posts I am a bit worried I may have chosen wrong...

I feel the dayton can go up that high fine, but I don't think the Tangband can go that low with more than its 15 watts rating.
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Old 14th April 2006, 12:33 AM   #8
Tenson is offline Tenson  United Kingdom
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Relax, I also originally planed to XO at about 400-500Hz 2nd order. However, upon trying it out I found the Dayton woofer too muddy and lacking definition for my taste. I am using it in the suggested 1.18 cubic feet enclosure with a 5cm dia port tuned to 28.7Hz. The cab has a sloped top as to reduce standing waves a bit. The Tangband is in a separate box on top. I had originally planed to use an open baffle Neo8 which is why the box is sloped like that as well and why it looks a little strange

Anyway, I found it sounded better with the Tangband going down as low as it could and then rolling off quite fast rather than using the Dayton. In a standmount and small room the max SPL is alright. Not huge but its alright for most stuff. For a floorstander I think you will have to cross higher up. I think it would wok fine if the woofer was better.

Can anyone suggest a direct replacement for this woofer if I want to upgrade it later?

By the way, an advantage of crossing the Tangband at about 400-500Hz means you can get away with no notch filter for baffle step as this is about the frequency baffle step will be anyway so simply adjusting the drivers relative levels will do the job.

Click the image to open in full size.
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Old 14th April 2006, 01:18 AM   #9
Relax is offline Relax  United States
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Excellent. I am building two pairs of floorstanders right now. One pair using this combo, the other using a vifa TC18WG29 and the Tang Band.

The Vifa sounds excellent except for its higher frequencies, above 200 its gets kinda harsh, so Ifeel confident in that XO at 500.

The Dayton Pair might just get a lower XO point. I am debating again now. I planned a MLTL for them, which will hopefully make them sound less muddy to begin with compared to a reflex.

the tangbands really are amazing though. Xo them over so they can increase power handling and they really come alive. As a fullranger they laked bass, but that was to be expected.

I also plan on picking up two HiVi B3S to compare.
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Old 14th April 2006, 04:00 PM   #10
Tenson is offline Tenson  United Kingdom
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Okay well to keep people updated I have decided to try the Seas P17REX woofers instead. I hope they will be a lot better than those cheap Daytonís and thus be able to cross higher up, maybe 500Hz or so.

I will make a new cabinet this weekend as I have some spare MDF and I'll probably get the drivers Tuesday and then run them in. No doubt I will need help a bit later on with doing the passive crossover, but thanks for your help with this one anyway!
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