CA18RNX Bookshelf help

[benthe8track]

Hello,

I have a pair of seas ca18rnx drivers left over from my previous car stereo. I would like to use these drivers in a pair of simple sealed bookshelf speakers. What would you recommend in terms of a tweeter and crossover?

Regards,
Ben

[Jed]

Hello,

I have a pair of seas ca18rnx drivers left over from my previous car stereo. I would like to use these drivers in a pair of simple sealed bookshelf speakers. What would you recommend in terms of a tweeter and crossover?

Regards,
Ben

You can use something like the Seas 27TDC. Some of the folks over at the Partsexpress board might be able to simulate something for you. We'd be glad to help you out once you have some real measurements with the drivers mounted in a box, since most of the guys here believe in measuring versus relying purely on simulations.

For a 2 way you should be able to come close with just simulations, but will have to tweak a bit after a crossover is suggested to get it to suite your tastes.

[benthe8track]

Thanks for your response.

I think I can get away with a modeled crossover for this project just because its really just an excuse to get into the garage and make some sawdust. Also it's an opportunity get some practice assembling a crossover before I build Denis Murphy's TMWW towers later on. I was actually toying with the idea of using one of those PE prefab crossovers. In addition I don't have the equipment to properly take measurements.

You think the Seas 27TDC would be the most complimentary tweet for the CA18? I haven't found many examples of people using the CA18 for anything other then car midwoofers (like I did).

[Jed]

You can check out Roman's site at www.rjbaudio.com. He's used the CA18RNX's brother (CA18RLY) to good effect. I'm sure he has a crossover schematic laying around for the CA18RNX using a Seas tweeter or could model one for you. If not I'll see what I can find or put together using some of my files I have from various projects I've done using the CA18RNX. I recently did a speaker using the CA15RLY and Seas TDC and it was pretty dang smooth sounding. I ended up giving them to my sister for a Xmas present.

Image not available

[Jed]

I got bored and decided to take a try at a crossover for you. Seas 27TDC (non-F version!) is the tweeter and the woofer is the CA18RNX.



Images not available



And here is the test box that was used for the above measurements, from the maker of Seas drivers. There has been some issue as to how accurate these files are, but if you get the acoustic center in LSPcad right they work great, I have found. No gaurentees though until you measure the drivers, but this should get you very close.

Just make your box like this one.

Image not available

The PE boxes or Madisound .75ft3 boxes should work well.

Regards,

Jed

[benthe8track]

Awesome! Do you have a larger pic of the schematic (or a BOM) though just it seems like the top is cut off. I'm going to build the box myself though, Ill throw up a solidworks drawing of what I'm thinking shortly.

EDIT:
Component Value
L1 0.250mH ri=0.150Ohm
L2 1.80mH ri=0.222Ohm
L3 0.400mH ri=0.155Ohm
R1
R2
R3 10.0Ohm
R4 9.00Ohm
C1
C2
C3 12.0uF
C4 12.0uF
C5 15.0uF

[Jed]

I'll come up with a ported box solution for you in a moment. I attached another pic of the crossover layout. 19-18 gauge inductors are fine except you want a low DCR for the 1.8mH. The caps can be Bennic or Solen from partsexpress.com or madisound.com.

Jed

[Jed]

Here is the unibox simulation for a 20liter (inside volume) ported box tuned to 43hz with a flared 2" precision port that is 4.75"-5" long. I'm assuming that is what you will want.

[benthe8track]

Perfect! Here is what I sketched up quickly for the box, just to get a feel for the size. It comes to just over 20L without the bracing or driver basket considerations.

Any thoughts on bracing?

[Jed]

For bracing you can do something like the PE boxes with a vertical brace with 2 circles cut from it. Make sure you have the tweeter center about 3" from the top of the enclosure so it is like the test box measurement conditions.

Jed

[benthe8track]

Thanks for all your help Jed. Ill be sure to post some pics when I get it together.

[Jed]

No problem. One last thing is you can put the port on the rear such that it is directly behind the tweeter. I've found that the 2" precision port works nicely, and you won't need to use the center tube because the 2 ends come together at approximately 5" in total length, which is perfect to tune the box to around 43hz. I also prefer the CA18RNX in the 20L, even though you could go as large as 24L-28L.

[benthe8track]

I'm trying to put together an order for the crossover parts but I'm having trouble finding the exact specifications as per your diagram.

Between madisound and solen (here in Canada) I can find all the appropriate values for the caps and resistors but I cant seem to find inductors that fit that description. Could you please point me in the right direction?

[jimangie1973]

I just finished a two way design using the CA18RNX with the TDFC. I used the 0.5 cu/ft madisound enclosure rear ported and tuned to about 43 Hz. The crossover is 2nd order electrical and comes close to LR4 at 1700 Hz.

I do everything using measured driver frequency and impedance responses in box.

[Jed]

I'm trying to put together an order for the crossover parts but I'm having trouble finding the exact specifications as per your diagram.

Between madisound and solen (here in Canada) I can find all the appropriate values for the caps and resistors but I cant seem to find inductors that fit that description. Could you please point me in the right direction?

Just use 18 or 19 gauge for all the inductors except the 1.8mH which should be 14 or 15 gauge, unless you want to use an iron core inductor.

[Jed]

I just finished a two way design using the CA18RNX with the TDFC. I used the 0.5 cu/ft madisound enclosure rear ported and tuned to about 43 Hz. The crossover is 2nd order electrical and comes close to LR4 at 1700 Hz.

I do everything using measured driver frequency and impedance responses in box.

Well what are you waiting for. Post your design! :T Ben, this will be a better alternative.

I was able to get better phase alignment using the topology I did over 2nd order electrical. The measurements I used came from bjorn? I think that was his name, from Seas. All in box on axis.

[jimangie1973]

Well what are you waiting for. Post your design! :T Ben, this will be a better alternative.

Well here you go. Looks similar to Zaph's SR-71 doesn't it.

Jim

[Jed]

Yes it does. I found you can get away with a smaller series inductor if using a zobel on the woofer. Looks like the optimum placement of your design would be 2-3ft away from walls because of the amount of BSC used.

How do they sound?

Jed

PS- after this afternoon I won't be around to answer any questions Ben, since I'm visiting a friend in NYC for a few days with my wife.

[jimangie1973]

I have them with the backs about 1.5 feet from the wall in a large bedroom. You are correct that they cannot be placed against the wall or in a bookshelf.

They sound very nice although not quite as clean in the midrange as my W18 MTMs.

I didn't try simulating them with a zobel. That would probably work although I'd have to simulate the driver phase integration.

Jim

[benthe8track]

After much consideration I decided to go with your design Jed. I figure I can tweek it to taste easy enough. Hopefully Ill have all the parts next week to assemble the crossover.

[Jed]

After much consideration I decided to go with your design Jed. I figure I can tweek it to taste easy enough. Hopefully Ill have all the parts next week to assemble the crossover.

Cool. Glad I was able to help. :T I like the Seas 27TDC tweeter very much. It sounded great in my last design with CA15RLY.

Jed

[benthe8track]

Since I'm a mechanical engineer not an electrical can someone verify I reading the diagram correctly. Is this how I will wire up the terminal? Forgive me if Im out to lunch.



I'm hopefully going to start construction this week if time permits.

[Jed]

That is correct.

[benthe8track]

Hey I just wanted to post a long overdue update. Thanks again for everyone's input in this thread. I think they turned out pretty good for my first venture with veneer. Most importantly they sound fantastic!

I thought a sealed Dayton RS 12 sub would be a nice addition as well.

Thanks again to Jed for the crossover design

[peter_m]

Benthe8track,
gorgeous speakers. I love the color, finish and rounded edges. Is the baffle solid wood or MDF+veneer?

Jed,
the 27TDC lack the ferro-fluid of the 27TDFC. The ferro-fluid increases the power handling but what audible effects can it have on the tweeter?

Peter

[Jed]

Hey there. I was wondering if you were going to get to those speakers. I'm glad my crossover worked well for you! I always get a bit nervous making a recommendation for a crossover design from simulation without measuring afterwards to confirm the FR.

As for the ferrofluid debate... in theory the non ferro tweeter will have a bit more detail, but less power handling at lower frequencies. I haven't compared the ferro tweeter next to the non ferro tweeter, however.

Jed

[benthe8track]

Benthe8track,
gorgeous speakers. I love the color, finish and rounded edges. Is the baffle solid wood or MDF+veneer?

Jed,
the 27TDC lack the ferro-fluid of the 27TDFC. The ferro-fluid increases the power handling but what audible effects can it have on the tweeter?

Peter

Thanks! Everything is MDF+ cheery veneer.