# Advice on crossover?



## caliberconst. (Dec 10, 2009)

I just scored some older paradigm monitor 9's. After messing around with them I have figured out the have a bad high pass crossover. There is almost no highs when hooked up threw the crossover, so I took the crossover out of the equation and the tweets work fine, they are just too loud. So I am thinking I need a crossover from partsexpress. I really am lost as to which one to get, so if you guys could point me in the right direction that would be great. I posted this in the DIY section because the boxes of these 9's are trashed, so I am going to re-use all of the drivers,ports and build new cabinets.


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## sparky77 (Feb 22, 2008)

One of the pre-built crossovers from parts express most likely won't perform very well with those speakers, at least not without some major modifications so you would be better off building from scratch.

Looking at the current crossovers are there any signs of leaking or bulging capacitors, or very dark burnt up resistors? It's possible some components have failed and simply need to be replaced to get the performance back.


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## caliberconst. (Dec 10, 2009)

Yes the resistors have some dark looking stuff on them. I got carried away and just blew both the tweeters, so I guess now I would need new pre-built crossovers and tweeters. Do you think you could recommend me a pre assembled crossover and tweeter setup?


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## Mark Techer (Jan 17, 2008)

caliberconst. said:


> so I took the crossover out of the equation and the tweets work fine, they are just too loud


:nono: No HP filter for the tweeter = BAD.



caliberconst. said:


> I got carried away and just blew both the tweeters, so I guess now I would need new pre-built crossovers and tweeters.


:rolleyesno:
You'll now have to replace the tweeters as feeding them full range signal (what happened when you disconnected the crossover) means that their voice coils are exposed to larger sign waves than they were designed for, hence over load and they have burnt out. It may be cheaper to just buy new drivers than finding someone that can re-build them for you. Either way it is time to :spend:


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## caliberconst. (Dec 10, 2009)

I know, I am an *IDIOT*, I totally know better. I had originally hooked up the tweeter (full range) to see if the tweeter was bad or something with the crossover. Then I tried showing off and pop. I am not to worried about it too much because I traded these for a bunch of I had laying around that was given to me, so the speakers were pretty much free. I just don't know where to start as far as picking out a replacement tweeter and assembled crossover.


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## bambino (Feb 21, 2010)

It is possible that you may be able to get a replacment diaphragm for them from an authorized Paradigm dealer or even through Paradigm themselves. What model are the speakers and what version? it should say on the back near the terminal cup.


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## caliberconst. (Dec 10, 2009)

They are monitor 9's, and I am pretty sure they are v.2. Paradigm didn't do a good job of labeling the version number for the first few versions. I am not opposed to calling Paradigm, I just assumed going that route would be pretty expensive. I am just going to use these in the garage, so I don't need to be too picky. I will give them a call tomorrow, in the mean time if anyone has some suggestions for other replacements, that would be good, then I can weigh all of my options.


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## bambino (Feb 21, 2010)

I was on E-bay abit ago and saw several crossovers for paradigm speakers, you should give them a look as there may be one that will work. The ones i saw were like $30.


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## caliberconst. (Dec 10, 2009)

Thanks bambino, I will check it out!!


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## Mark Techer (Jan 17, 2008)

bambino said:


> It is possible that you may be able to get a replacment diaphragm for them from an authorized Paradigm dealer or even through Paradigm themselves. What model are the speakers and what version? it should say on the back near the terminal cup.


It won't be the dome or diaphram, it will be the voice coil which is ultra thin copper wire and deforms with little or no effort (especially from a full range signal). It will be a replacement HF driver. 

I did a pair of silk domes about 20 years ago, showing off to a friend one of my first DIY speaker. There we were listing to Jean Micheal Jarre's OXYGENE (loud) with beautiful crisp highs, then suddenly a "phfft" sound followed by a small puff of smoke, and no highs anymore. Physically, the domes appeared to be fine. In this case, I'd pushed the amp into soft clip and that was enough to fry the tweeters. 

From then on, I added "speaker protection" to my designs :sn: by way of polly switches and have not blown a tweeter since.

Crossovers are not that hard and what I like about the DIY version is that you can tailor the sound to suit you.


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## digital desire (Dec 17, 2006)

http://cgi.ebay.com/Paradigm-7se-Sp...44?pt=Speakers_Subwoofers&hash=item519503a970


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## digital desire (Dec 17, 2006)

I would add: Speakers are a very complex _system (well, at least properly engineered ones are) and sticking in any 'ol replacement components will more than likely get you a ticket to the fail boat._


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## Mark Techer (Jan 17, 2008)

digital desire said:


> http://cgi.ebay.com/Paradigm-7se-Sp...44?pt=Speakers_Subwoofers&hash=item519503a970


The crossover in the link is a mixed order network with a 12dB/oct HP and 6dB/oct LP. Is it the genuine replacement for the speakers in question?


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## caliberconst. (Dec 10, 2009)

Mark Techer said:


> The crossover in the link is a mixed order network with a 12dB/oct HP and 6dB/oct LP. Is it the genuine replacement for the speakers in question?


It doesn't look anything like the one I have now plus I would need two. I do however appreciate the effort and providing a link.


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## caliberconst. (Dec 10, 2009)

These look very similar to what I have, but that is just going off of looks alone. Actually the HP looks exactly like mine, the LF is questionable, but I could swap them around.

http://cgi.ebay.com/Paradigm-Compac...Subwoofers&hash=item5d2d8fd782#ht_1010wt_1067


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## Mark Techer (Jan 17, 2008)

Are you comfortable making your own or would you prefer an off the shelf option.


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## caliberconst. (Dec 10, 2009)

I think I would prefer an off the shelf option. What are the pro's and con's between building one my self and and an of the shlef.


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## Theresa (Aug 23, 2010)

I've never known someone who is experienced with speaker design to say that "its not that hard" to design a crossover. Without measuring equipment, including a microphone and a computer and good software designing crossovers is almost black magik. One thing that you could try is looking for someone elses design that uses the same drivers and see if it can be tweaked to work with yours. Its one of the reasons I quit doing passives and changed everything but my surround speakers to using active crossovers.


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## bambino (Feb 21, 2010)

Mark Techer said:


> It won't be the dome or diaphram, it will be the voice coil which is ultra thin copper wire and deforms with little or no effort (especially from a full range signal). It will be a replacement HF driver.
> 
> I did a pair of silk domes about 20 years ago, showing off to a friend one of my first DIY speaker. There we were listing to Jean Micheal Jarre's OXYGENE (loud) with beautiful crisp highs, then suddenly a "phfft" sound followed by a small puff of smoke, and no highs anymore. Physically, the domes appeared to be fine. In this case, I'd pushed the amp into soft clip and that was enough to fry the tweeters.
> 
> ...


I've actually replaced the diaphram in tweeters that have the voice coil attached, it's just a matter of removing a couple screws removing the old one and replacing with a new one. Maybe things have changed in the last 20 years.:dontknow:


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## digital desire (Dec 17, 2006)

You _have_ to get the original crossover if you want the speaker to sound like it was engineered and voiced. If you use _anything_ else, it will be a compromise, most likely a very bad one. The "black art" mentioned above is one hundred percent correct, crossover design is tough. It requires very good analysis of the drivers, the baffle, the alignment, etc. There are plenty of plug and play devices, crossovers are not one of them.
You can however, put any old crossover in them. They will produce sound. But if you A/B'd them in a store, you would go home with something else.

Have you called the manufacture to see if any were available? It would be worth the $$. just my 2 cents.


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## Mark Techer (Jan 17, 2008)

Theresa said:


> I've never known someone who is experienced with speaker design to say that "its not that hard" to design a crossover.


Speaker design is more of an art from than an exact science. I take no offense to the term "black magic" if that works for you. I think the reason many look at as too hard is they think too deep into it. I've made (and sold) seven 7.1 systems in the last 11 years, and all of them worked (or I doubt the buyers would have handed over the cash if they did not sound good). So either I understand the WHY or I got really lucky and I somehow I don't luck applied each and every time. 

In its most simple terms, a typical LR crossover is a parallel rejection electrical circuit - ie it rejects frequencies above the set value of the LP and below the set value of the HP. A Cap has no "resistance" at or above the Xc and will present an ever increasing resistance to frequencies below the Xc. Coils have no "resistance" at or below the Xc and will present an ever increasing resistance to frequencies above the Xc. Because electricity is lazy, it always chooses the path of least resistance. The values chosen to represent the point Xc are based on frequency and impedance load. 

So whilst a crossover is a combination of Caps and Coils (and some resisters), it wants to see the speaker drivers as fixed resistances even though speaker drivers behave nothing like fixed value resisters. In a 2 way passive design, you have a LP and HP and I would suggest that no less than 12dB/oct is used simply because you have the ability to correct phase issues by inverting the tweeter's polarity. Each time you add a Cap or Coil, you get a +45° (for Coils) phase shift and a -45° (for Caps) phase shift. So for a 2 way LR at 12dB/oct, you have 2 Caps and 2 Coils resulting is a 180° phase shift between woofer and tweeter. Invert the polarity of the tweeter and you now have both drivers in phase. 

Something important to consider is that many components have a tolerances of at least +/-5% where even expensive caps like those from Sollen and Bennic are not 100% precise. 10% is quite a margin. 

The first step in a custom design is finding out the Fs of the Tweeter? Given the OP has to replace the tweeters anyway, he can choose to use the same ones or something else. The Fs is the resonant frequency of the driver and why they got fried when playing un-flitered frequencies below that. You want to set Xc at least 1 octave above Fs and Fs will be listed in the spec sheet of the driver. The Fs of the VIFA XT tweeter I use is just 550Hz, so in theory, an XC of 1100Hz could be used. In my passive systems, I used 1550Hz. Most tweeters however will require Xc to be at or above 2K.


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## digital desire (Dec 17, 2006)

^^^Good art comes from experience. You seem have it, and the tools. My point is that a shot gun approach (op's) to save a pair of fairly decent speakers would be the wrong approach.


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## Mark Techer (Jan 17, 2008)

digital desire said:


> ^^^Good art comes from experience. You seem have it, and the tools. My point is that a shot gun approach (op's) to save a pair of fairly decent speakers would be the wrong approach.


I agree.


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## fbov (Aug 28, 2008)

caliberconst. said:


> ...I posted this in the DIY section because the boxes of these 9's are trashed, so I am going to re-use all of the drivers,ports and build new cabinets.


Well, what's the plan now that the tweeters have joined the boxes and all you have are mids and woofs?

Looking at the spec sheet, this was a 4-driver, 2.5-way design. You will not find a similar crossover on the shelf. Presumably the pair of woofers was the 0.5 part with the mid running open to the tweeter cross. You can learn to characterize drivers (electrical and FR) and use crossover design tools to mate these drivers with a new tweeter, which will be chosed for sensitivity unless you want to pad the rest of it down. Try asking on RE Tech Talk or HTGuide forums, but I'll bet you get a lot of "are you sure you want to jump in the deep end?"

Have fun,
Frank


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