# Re-creating Revel F50a speakers



## Guest (Jan 1, 2008)

Hi all!

Sorry in advance for my babbling...

I have recently obtained a Parasound Halo A23 amp and I want to make some good speakers for it.

I have (6) 6 1/2 inch drivers which come from the Revel F50a speakers. So, I want to copy the Revel F50a speakers If I can.
I also have 1 of the midrange drivers but I don't want to spend the amount they want to buy another ($280.00). I would like to put that money into 2 new midrange and 2 new tweeters. I have wood shop class at school and I can make the speaker cabinets and match them exactly to the actual F50a cabinets. I have some pictures and the owners manual from the F50a showing the actual dimensions, which I'm sure I can replicate. I don't care how they are finished, just how good they sound.

My questions are concerning the crossover and the new midrange and tweeters.

I don't have access to the actual crossover and I don't really understand how to design one. Does anyone know the actual design of the crossover? Should I use that actual configuration since I'm going to duplicate the cabinet?

My second question is concerning the midrange and tweeters, what would be a good match for the 6 1/2 speakers I already have? The F50's have a 5.25 mids and 1 inch titanium tweeter. There is also a dial for the tweeter volume level on the speaker. I going to place the crossover outside the speaker box so I have access to it while I'm tuning the speakers... then install it later.

I am willing to spend about $400 dollars to make the cabinets and crossovers and buy the 4 speakers. I am thinking about Seas drivers... Seas MCA15RCY (H1262) 5.5"Coated Paper mid $60.00 and a Seas 27TTFNC/GW (H1461) 1" Titanium dome tweeter $80.00

I don't plan on blasting my speakers with hip hop... I just want a nice stereo sound with good imaging and detail and a moderate sound level.

Also, I have a picture of the crossovers from an F50... can anyone tell me what the components are and the circuitry of these crossovers? Sorry, the pic's are as big as I can find! 

Any suggestions or help would be appreciated!

Eddie


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## Anthony (Oct 5, 2006)

First off, welcome to the Shack.

Don't really know where to start on your questions.

Someone may be able to read the color bands on those resistors and get values off the capacitors, but the inductors and how they are all wired would be a shot in the dark. Unless someone has access to this specific schematic, you may be out of luck there.

As for the crossover design, you may have a couple of options:
Get the folks at Parts Express of Madisound to help you design one and then source your parts from them. It's not a perfect option, since much of crossover design is trial and error. 

You could get premade crossovers at the right frequency/slope ranges, but these are usually only tuned to one specific type of impedance curve and very rarely work for all speakers. However, it would be a cheap way to get into the process, even if the final result was not ideal.

Or you could learn a lot about crossover design, get some test and measurement equipment (mic, sound card, mic preamp) and start experimenting. It takes a lot longer, but you learn a lot and you can dial in your own sound.

good luck,
Anthony


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## MrPorterhouse (Jul 29, 2006)

No need to worry about copying those exact crossovers because if you aren't going to use the exact same midrange drivers, then you'll need a new crossover design anyway. Once you pick out your mids and tweeters, then you design the cabinet and crossover around the drivers. An experienced DIY'er(not me) can help you with crossover design. The cabinet design is farily user friendly if you pick drivers with similar specs as the original Revel, so you could model a similar type of cabinet, and then customize the crossovers accordingly. You might not have a duplicate Revel, but you should have a good speaker in the end.


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## JCD (Apr 20, 2006)

I think I've got some more bad news for you.. unless you get identical drivers to the drivers in the F50a's, that crossover really won't work for you. And like the others have said, you probably can't tell what all the values for those components are. 

Designing a crossover is REALLY difficult to do right -- especially a three-way design like you're proposing. You could run it through one of a handful of freeware simulators, but that only really gives you a starting point. After that, you'd need some testing equipment to make sure you got everything right and extra crossover parts to tweak the design. After all the testing equipment, and various crossover parts, it'd probably be just as cheap to have bought the original drivers for the speaker itself. This doesn't include the HOURS of testing you'd probably have to go through.

I don't mean to kill your enthusiasm, but I think that, if you want to get the best results, I'd get the same drivers that came with the original speaker and rebuild it from there.

If you REALLY want to start over with the 6.5" drivers, I'd tell you to use the 6.5" drivers and a tweeter in a 2 way design. If you've got six of them, I'd consider making similar MTM's for the front three speakers in a Home Theater and then maybe buy two more 6.5's and tweeters for the surrounds. This assumes that your 6.5" drivers are appropriate for a 2 way design (I don't know their frequency range). Alternatively, you could go with a TM design and only need 5 tweeters. That'd leave you with an extra 6.5" driver. Designing a crossover for a 2 way design is supposed to be a LOT easier than a 3 way. That being said, you'd still have to get all the testing equipment, etc.. meaning, you'd probably still be better off just rebuilding the F50a's with their respective drivers.

JCD


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## Guest (Jan 6, 2008)

Wow... Thanks for all the replies!

Well I have done a bit of reading and I can see that I really can't use the revel crossover for new mids and Tweets. 

Could I use the the low end crossover as a starting point? I mean what information can I get from the crossover as it sits? I guess that could give me the range of the bottom end of these speakers, right? I mean where they start and where they crossover into the mids. Shouldn't I really think about using the low end crossover, since it's been designed to work with those speakers in that enclosure. I could then think about the range of the mids, in terms of where they would start in reference to the low end... then move on to the tweeters. From what I've read the crossover corner frequencies are important. In the equation, the low xo and the enclosure are the known variables, so, shouldn't I work from there? I mean the design of the low end xo... does that tell me if it's a 6db or a 12 db or whatever... then should design the rest based on that?

So, at this point, I'm trying to understand the crossover components of the three low frequency drivers and at what frequency they are crossed over at. And, of course, how and why the circuitry is designed. Looking at the components, it looks fairly simple. Are they a coil, a capacitor and a resistor?
Can anyone tell me how the circuit is designed as the components are laid out on the board? I think the caps read 352 705 and 430/450? Any ideas on the rest of the items. 

If I figure out he low end xo, could madisound then design the upper crossover? Or is this putting a horse in front of the wrong cart?

Thanks again for any help.

Regards, 

Eddie


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## JCD (Apr 20, 2006)

erpiii said:


> Wow... Thanks for all the replies!
> 
> Well I have done a bit of reading and I can see that I really can't use the revel crossover for new mids and Tweets.
> 
> Could I use the the low end crossover as a starting point?


Maybe, maybe not. Since this is a three way system, the crossover is designed for three distinct drivers as well as the other crossover (between the tweet and mids). Even though the "low end crossover" may divide the signal from the mids to the woofer, it will be affected by the tweeter as well as the mids and woofers. 



> I mean what information can I get from the crossover as it sits? I guess that could give me the range of the bottom end of these speakers, right? I mean where they start and where they crossover into the mids.


I don't think there is much to be gleaned from the crossover unless you have a lot more information. Even if you had the crossover point between the mid/woofer, you won't know if the crossover is correcting any dip or peak in the freq response unless you had the full schmetic as well as the electrical parameters of the tweeters and.. 



> Shouldn't I really think about using the low end crossover, since it's been designed to work with those speakers in that enclosure. I could then think about the range of the mids, in terms of where they would start in reference to the low end... then move on to the tweeters. From what I've read the crossover corner frequencies are important. In the equation, the low xo and the enclosure are the known variables, so, shouldn't I work from there? I mean the design of the low end xo... does that tell me if it's a 6db or a 12 db or whatever... then should design the rest based on that?


You could probably determine the order (1st=6db/octave, 2nd=12db/octave, etc) and type of crossover (Bessel, L/R, etc) but that's only the start in the crossover designing process. Getting the crossover to actually cross over at your designated point given the intereaction between it and the other crossover as well as the drivers is the tricky part. This doesn't even take into consideration any corrections to the drivers to smooth out the FR or phase related issues or..



> So, at this point, I'm trying to understand the crossover components of the three low frequency drivers and at what frequency they are crossed over at. And, of course, how and why the circuitry is designed. Looking at the components, it looks fairly simple. Are they a coil, a capacitor and a resistor?
> Can anyone tell me how the circuit is designed as the components are laid out on the board? I think the caps read 352 705 and 430/450? Any ideas on the rest of the items.


In general , the first answer is "yes". Again, as mentioned above, the devil is in the details. The numbers that are mentioned look more like part numbers than the values for the various parts. Although I know many of the issues involved with a crossover, I don't think I could help determine the specifics in your case. However, for the reasons above, I think it wouldn't be that helpful in the end anyway.



> If I figure out he low end xo, could madisound then design the upper crossover? Or is this putting a horse in front of the wrong cart?
> 
> Thanks again for any help.
> 
> ...



There are places that can design a crossover, but I don't think it'd be with a "good" result, although it might be "ok". I think I saw someplace that would design a crossover. The fee was something in the neighborhood of ~$200 or so but you had to buy the drivers from them and.... I can't seem to find the link anywhere. 

So, I know this is kinda throwing a wet blanket all over your enthusiasm again, but I'd hate for you to go through all the cost and sweat and blood and not get what you're looking for.

Here are some links on Crossover Design you can read over to get a better understanding of what's involved:
http://sound.westhost.com/lr-passive.htm
http://sound.westhost.com/ptd.htm
http://www.linkwitzlab.com/frontiers.htm
http://www.geocities.com/kreskovs/Stored-energy.html
http://sound.westhost.com/doppler.htm
http://www.silcom.com/~aludwig/Sysdes/Crossove_Design.htm
http://www.termpro.com/articles/xover2.html​
JCD


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## Guest (Jan 8, 2008)

Thanks for the information Jacen! I really do appreciate your help!

Here's a better picture of the xo... it shows that actual component values. 

These are the assumptions I've made just looking at it. 

There are two sets of inputs and three sets of outputs to each of the 3 woofers.
Not all the woofers are crossed at the same point, each of the three woofers has a different xo value.
The three woofers are in parallel.
Two of the woofers incorporate a coil, resistor and a capacitor in some type of circuit. One of the woofers has just a coil and a cap... 3 speakers 3 circuits.

There's no way to tell the value of the coil unless tested. Also, is the coil also called an inductor? What does an coil/inductor do? The resistor limits power and the capacitor limits frequency, right?

Can I check the resistance of my speakers using an ohm meter? Will that tell me anything about the speaker? I assume that the resistance of the speaker will change with the amount of power that goes into it, correct?

The specs for this speaker say the 3-way speaker system is 5Ω (nominal)
3.2Ω (minimum @ 64Hz). They also say " A high-order crossover at 225Hz and 2.3kHz to optimize the on- and off-axis response of the system"?
Low-Frequency Extension -10dB @ 23Hz, - 6dB @ 27Hz, - 3dB @ 32Hz Does this tell how the bottom "rolls off"? Less of the sound the lower you go?

What is a "high-order" crossover?

Also, there is a control knob for the tweeter, is it called an L pad? Is that a variable resistor, do all those wires come off the L pad at different resistances and so the xo has different circuits for where the resistance is set on the L pad? Or is the L pad after the crossover and my assumption not correct? If not correct, where do all the wires come from?

I need to turn in my project plans for my woodworking class by Friday. I have cad plans for the speakers based on the real F50 speakers. I really want to go ahead with the F50 designed cabinets and use the 6 drivers I have for the low end. I guess this might turn out to be a good learning experience and something I can tinker with as my knowledge increases.

Are most of the people who build their own speakers electrical engineers? It seems like you have to understand a lot in order to be effective at doing this.

Thanks again for all the help! 

Eddie


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## Owen Bartley (Oct 18, 2006)

Eddie, that's a great ambitious project you're working on, good for you! So first of all, good luck, and keep at it. Second, as a few others have pointed out, it's going to be difficult to approach as a clone project without having all the identical drivers and knowing either their parameters, or having the schematic for the XO.

But don't let that discourage you, because you can still build a kick *** speaker! I think it would be easiest to start from scratch if you have the TS parameters for the drivers you have already, and base your mid/tweet decisions on that. Some of the experts here could recommend drivers to match some of the characteristics of the ones you have, and could probably help you with the crossover design too.

If you're for sure going to do this project, go ahead with the cabinets especially while you can use the resources you have in class. Then you can finalize the driver design and layout and XO as you go along.


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