Different crossover point to improve vocal reproduction?

heem6

heem6

Member
Hi,
I have a pair of Cerwin Vega! VS-120's that I've recapped and replaced the tweeter and midrange. They sound very nice now - except for vocals. Voices sound very digital and raspy.

They are crossed over at 6kHz and I'm wondering if I could lower that to say 3.3kHz to let the tweeters do more of the midrange lifting? Does it sound like that might improve the vocal reproduction?

The tweeters are pretty well regarded VIFA's with a resonant frequency of 1660kHz, the midranges were the best reasonable match I could find, and reviews over at PE were positive. Original crossover points are 300Hz and 6kHz. The cabinets do not have much stuffing at all, btw. Current tweeter caps are Obbligatto Film Oil - 2.2uf. Mid caps are Dayton 6.8uf.

I'm open to any other suggestions that might improve the situation. I was going to sell these and upgrade, but I got a great deal on them, they're in excellent condition and honestly am very happy with them now other than the vocal frequencies. Any advice is greatly appreciated.

PS - I'm running them from a Pioneer ELITE VSX-52TX in Stereo mode.
 
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With those points all vocals are basically coming from the mid in isolation.

Personally I would run some response curve tests at your listening position using eg AudioTools app o the iPad, then consider what todo after that.
 
Many 3 way speakers invert the polarity of the midrange driver. If you connected your new midrange with standard polarity it could have an affect on the sound.


My suggestion would be to pull the mid's, invert the polarity and give them another listen.
 
This is one of the pratfalls of sticking different drivers in an existing system. The "system" is compromised of three basic parts: The driver(s), the enclosure, and the crossover to assure the drivers are each doing their job properly. Remember, the system was designed with specific drivers that meet the qualifications so they will work in conjunction with the crossover (with the points and slopes) designed specifically for the original drivers to get the best out of them.

It's all a balancing situation that might well be considered a black art.

When you just drop in drivers willy-nilly, you upset that magical balance that was arrived at by some pretty serious engineering. Results can be unpredictable.
 
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I second the Skippers thoughts.

Crossover design is as much black art as it is engineering. There is a fine balance between the various drivers parameters, the enclosure size and design and the actual components that make up a crossover.

Crossover design and construction is one of the things that separate great speakers from the "also ran's". You can take top notch drivers and have them sound horrible with a bad crossover design, inversely you can take average drivers and use a properly designed crossover and get some surprisingly good results, DQ10's come to mind.
 
Thanks for all the comments so far. I will try reversing the polarity on the midrange, but right now I have one new midrange installed (it was blown when I got it) and one old and they both have the same problem. I've also heard others complain of this same issue with this series speaker so I think it is a design flaw. I don't believe that things can't be improved upon, even if there was serious engineering involved. Designs are often compromised by budget constraints, materials constraints, even by bad management, as I'm sure we've all dealt with in our jobs. I did spend a lot of time and was careful to try to match up specs as best as I could between the old and new drivers.

I will readily admit that I am a n00b to this, and I can use all the help I can get. That's why I'm asking the more experienced people here.

sreten - those are the crossover points quoted on the marketing brochure, and I replaced the caps with the same as the original values.
 
sreten said:
Hi,

How do you get 300Hz with 6.8uF ?

rgds, sreten.
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Yep looks like he is crossing from the woofer to mid at about 6000 Hz. and out of my range of heating for the tweeter. That is the problem. Time to recalculate those capacitors.
 
JimPA - Thank you for finding the crossover schematic!
HTHMAN - My gut says you're right, the crossovers need to be recalculated.

I'm willing to spend money buying new caps if I can get some help figuring out what values I would need (and if I would need to change the inductors as well).
 
heem6 said:
I'm willing to spend money buying new caps if I can get some help figuring out what values I would need (and if I would need to change the inductors as well).
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There are lots of crossover calculators on the web, but this simple one will get you in the area. Figure 4 ohms for each driver and put in the desired crossover point. If your current crossover is like the schematic that was posted, replace the caps with the values indicated on the chart. Otherwise, build or buy a new one.
http://www.diyaudioandvideo.com/Calculator/ApcSpeakerCrossover/
 
Thanks! I took a first crack at it. Does this look like I'm on the right track?

4CpCkV0.jpg
 
Use any calculator you like BUT use the actual driver impedence (it will be shown on the response chart for the driver) at the desired frequency, not the nominal. Eg if it's a 4-ohm driver at 6kHz it's impedence is likely to be between 6 and about 12 ohms, so use that to calculate the LPF values. Also you need to consider the response of the driver; if it is rising steadily towards 6kHz, say +6dB at that point (I choose that number to make this simple....) then if using a 1st-order network, the crossover point could be shifted down a full octave (to 3kHz) to keep the response level.

This is why you need to measure the actual response before doing anything. Spend £20 on a Draytek IMM-6 mic and a few quid on AudioTools app for the iPad, it will be by far the best use of money initially.
 
J1mbo said:
Use any calculator you like BUT use the actual driver impedence (it will be shown on the response chart for the driver) at the desired frequency, not the nominal. Eg if it's a 4-ohm driver at 6kHz it's impedence is likely to be between 6 and about 12 ohms, so use that to calculate the LPF values. Also you need to consider the response of the driver; if it is rising steadily towards 6kHz, say +6dB at that point (I choose that number to make this simple....) then if using a 1st-order network, the crossover point could be shifted down a full octave (to 3kHz) to keep the response level.

This is why you need to measure the actual response before doing anything. Spend £20 on a Draytek IMM-6 mic and a few quid on AudioTools app for the iPad, it will be by far the best use of money initially.
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Quoted for truth and emphasis.
 
heem6 said:
Thanks! I took a first crack at it. Does this look like I'm on the right track?
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The values you show would be correct providing you wire the capacitors in parallel. As was pointed out, you may not get the same crossover points as the original since you are not using original drivers. But, as a starting point, I would rebuild the original crossover to original values and see how it sounds.
 
I have questions and comments.

I'm not sure I would have used the term 'willy-nilly' to describe the OP's work finding good drivers. I don't disagree with the idea that it is what's causing the problems here, but I reserve willy-nilly for 'stick in anything that's the same size including a Pyle car sub, and cut the baffle if it doesn't fit.' This was a step above that and probably sucks less. So there is hope for the OP. :p

Why would the original designer cross over to the woofer at 6000 Hz in the first place? Are you sure that's correct?

The original crossover had cap/inductor/cap configurations in both the mid and tweeter circuits. The redesign does not look the same at all - OK the mid section does somewhat but the tweeter circuit doesn't. Which is neither here nor there but I am really wondering if it's going to be any better without having the drivers measured. I mean if you're going to spend money on inductors, which aren't cheap, why not go all the way.

Finally, the redesigned crossover you posted has very bizarre values on their parts list - a 49,000 uf cap for example, and a 3217 mH inductor. Unless their units are off (i.e. they are actually showing the values in nf and microhenries), that's weird.
 
Your hearing is typically more sensitive in the midrange article. In the case of CV, most of what they used for midrange was those damned seal back mids. Never heard one I liked. I would suggest using a 5}`6" - such as a Peerless Seas, or a brand, that has good rendition characteristic! If you plan to use the same network try to used the same or near as impedance.
Good lucj
DC
 
Hi - Thanks! I really appreciate every post, even if I don't comment on each one specifically. I think we may have figured something out!
The project started with me replacing all the caps except one, that I couldn't see the value of until removing the one next to it. I had already ordered all the caps and figured it wouldn't make a great difference. But after running it down with the schematic provided, the sole remaining green cap IS A 5uf MIDRANGE CAP (C3) - and it's electrolytic, which means it's probably bad 25 years later....The original electrolytics were 1) the 5uf cap, 2) a 30uf and a 3) 100uf cap. That doesn't even match the original schematic of 5uf, 30uf and 40uf. Maybe I should consider replacing the sole midrange cap and the 100uf with a 40uf or 50uf?

I think it's a misunderstanding that CV crossed over the woofer at 6kHz. I believe that's the tweeter crossover point, and the mid crossover is at 300Hz.

And thanks toxcrusadr, for the vote of semi-confidence! :thumbsup:

The small one next to this is the 5uf mid cap - after I scraped off a ton of glue you could read the value etched on the board.
qTVnVbu.jpg


xiE9DM2.jpg

The Obbligatto Film Caps were mounted separately, way too big to fit on the board.
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TAC2gIS.jpg
 
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Ooh, put a film cap in there and maybe it will make a difference. Would be interesting to test that cap for not only capacitance but ESR.
 
I wish I had the equipment to test for ESR. I'll bet it's way out of spec. I'm ordering a couple 5uf Dayton Polys and 47uf electrolytic caps.
 
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