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Multi-Way Conventional loudspeakers with crossovers

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Old 14th February 2008, 11:20 PM   #1
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Default Ringing problem with dayton DIY's

I had a friend rebuild my RadioShack 2-way speakers with Dayton parts. He used the following:

DC28F-8 silk dome tweeter 89dB
http://www.partsexpress.com/pe/pshow...number=275-070

DC250-8 Classic woofer 89dB
http://www.partsexpress.com/pe/pshow...number=295-315

Acoustastuff Polyfill
http://www.partsexpress.com/pe/pshow...number=275-070

Dayton XO2W-2K 2-Way Crossover 2,000 Hz
http://www.partsexpress.com/pe/showd...number=260-140

Radio Shack Nova-18 cabinets

These speakers sound awesome on simple clear music, such as Pink Floyd or Bob Dylan or Maggot brain, and it even sounds really good with Cake and other modern pop. But it can't handle metal. When the music gets complicated and the high-pitched four part harmony male vocals start, the midrange spikes in volume rather sharply and I get a ringing, garbled sound. Songs like Savatage's "Not What You See" and Blind Guardian's "And Then There Was Silence" are two big offenders. Lots of Muse songs too. What's more, a lot of my CDs which are range-compressed sound like they're being driven into clipping. This happens at even moderate volumes, but is really noticeable at higher volumes.

If I swap speakers out the problem disappears, so it's not my amp or input source. (amp: Yaqin MC-100B tube amp, 30 watts/channel triode 60/watts channel UL, neither mode makes any difference. Input source: Toshiba HD-A3 HD DVD player. Not exactly HiFi, but will do for now as I'm on a budget).

I'm really at a loss as to what could be wrong. I'm new to Hi Fi, and speaker design is not my thing. The guy that built these never tested them with metal. He says they sounded great when he ran Pink Floyd through them, but admits he didn't do much testing beyond a few songs here and there (and all on vinyl).

He is going to stop by and demo the speakers again on my system with my music, but I'd really like to be armed with some knowledge. He knows a bit about speaker construction - he's got the computer programs and stuff, and he built himself a really nice set of bookshelf speakers that sound great... so I'd like to be armed with some knowledge of what could be wrong. Right now all I can say is that they're "ringy" at certain frequencies. I'm hoping some gurus here can help me determine why.

Thanks all.

Charles.
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Old 15th February 2008, 04:40 AM   #2
fwater is offline fwater  United States
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The Dayton woofer's response graph shows an almost two octave spike as a result of cone breakup, peaking around +9 dB at 2200Hz. This would explain a garbled or ringing sound. Even when properly attenuated, cone breakup can sometimes still be offensive sounding. The pre-fab crossover can't even begin to handle this spike. An aggressive Zobel might help. I ran a sim without knowing the values of the pre-fab X-O componnents but made an educated guess, and came up with a 50uF cap & 4ohm resitor that pulled the peak down by at least 9 dB. The sim also suggests around a 3ohm restor in series with the tweeter (after X-O) would level out response. The result will be less sensitivety, but a more listenable and balanced sound. Definitely worth a try to save these speakers. BTW, if you don't know the terminology, "a Zobel" refers to a simple X-O component to help control a drivers rising impedance and therefore making the intended slope more effective. It is a capacitor and a resistor, wired in series, and then wired between the woofer's positive and negative terminals.
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Old 15th February 2008, 05:24 AM   #3
fwater is offline fwater  United States
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Charles, I visited you weblink. Anyone that can turn an inexpensive jap bike into a slick chopper was born to DIY a set of speakers. You'll get five times the results compared to what you have now with your building skills and by asking a few questions, and for probably not much more money. I could help design a more proper crossover for the drivers you already have, if interested.
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Old 15th February 2008, 11:48 AM   #4
sreten is offline sreten  United Kingdom
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Hi,

As stated the c/o is very wrong for the drivers, and even with a flat
mid/bass unit would only work if it is zobelled. The "design" also has
no baffle step included or any padding for tweeter level.

I'd guess the inductor is tapped and only one of the low pass
capacitors is used for 8 ohm / paralled for 4 ohm.

A 10" bass- mid / 1" tweeter 2 way is a very difficult thing to do.
For these drivers where the tweeter distortion is "average to
poor- Zaphaudio.com" and the 10"ers midrange distortion levels
also not good (see PE PDF) its never going work well IMO.

http://www.speakerbuilder.net/web_fi...a/lyramain.htm

As you already have the bass units and tweeters I think the above
would be a very good to rather excellent idea if you would like what
can be called acccurate clear midrange, which is what mainly counts.

The higher tweeter c/o frequency reduces its distortion and the
dome midrange runs the frequency range of the 10" distortion.

Reducing the 9R midrange resistor slightly may liven it up a touch.

FWIW I doubt in the current state, your speakers are awesome
on any sort of material. They are simply wrong which may sound
interesting with some material but dreadful with other material.

/sreten.
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Old 15th February 2008, 01:42 PM   #5
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Yes to all of the above - you definitely need to go 3-way with these.
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Old 15th February 2008, 03:41 PM   #6
sreten is offline sreten  United Kingdom
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Click the image to open in full size.

Hi,

The cabinets appear to be a little small for the driver, 23"x12"x8".
The port should be closed off, left open it will add boom.
Assuming 3/4" stock internal volume pans out at 0.85 cuft.
Well stuffed might get this nearer 1 cuft effective.
This gives a box Q of 0.9, not too bad but an ~ 2 cuft box is ideal.

/sreten.
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Old 15th February 2008, 03:43 PM   #7
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Default what if...

What if I replaced that tweeters with these:

http://www.partsexpress.com/pe/showd...number=264-813

And then find a more suitable crossover, of course.

Charles.
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Old 15th February 2008, 04:07 PM   #8
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That would probably work - you'd have a mid-tweeter instead of a 3-way or 2-way with mid-woofer. You could cross much lower to let the woofers just carry the bottom end - and with the right box they can do a very good job of that.
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Old 15th February 2008, 05:20 PM   #9
sreten is offline sreten  United Kingdom
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Default Re: what if...

Quote:
Originally posted by ChopperCharles
What if I replaced that tweeters with these:

http://www.partsexpress.com/pe/showd...number=264-813

And then find a more suitable crossover, of course.

Charles.
Hi, not a good idea in my opinion, just not thought through, /sreten.
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Old 15th February 2008, 05:32 PM   #10
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I don't think he's really going for an all-out design - just wants to get these speakers rebuilt and up and running - if he's not going for audiophile sound/crossover perfection etc. I think he'll be OK.
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