Help making a passive crossover

[l33tfr34k]

Thanks for your help guys but I'm still fairly new at this so would someone mind explaining to me what I'm looking at in the schematics?

And can anyone recommend a good place to buy the components from?

 

[TLS Guy]

Thanks for your help guys but I'm still fairly new at this so would someone mind explaining to me what I'm looking at in the schematics?

And can anyone recommend a good place to buy the components from?

If you don't know what you are looking at, then you can't build it. Where do you live as that makes a huge difference as to where we recommend buying the components?

By the way can you send or scan what you have from Tannoy, so I can make sure there are no errors.

Before you build you will have to get some electronics books, and study, as if you don't understand it, you will make errors and won't be able to test the crossover.

Do you have the port specs? That will be crucial. Your box must be of the same internal volume as the Tannoy box, and the ports must be exactly the same.

I will see your reply later, I'm going out to resume repairs on my Willys Jeep. I have the fuel system apart but going back together now.

 

[l33tfr34k]

I understand enough of the drawing to know that there are 3 capacitors (1st, 2nd, and 3rd order) as well as 3 coils. I don't know what the B1 stands for.

I live in the Baltimore area but I wasn't sure if I could get these components from a place like Radio Shack or if I should be looking at a more specialized store.

As for the volume of the box, the specs on the speakers say that it is 17 liters. I am a skilled carpenter and am fully capable of building an appropriate box.

I have asked Tannoy for the port specs and I'm still awaiting their reply.

 

[TLS Guy]

If you don't know what you are looking at, then you can't build it. Where do you live as that makes a huge difference as to where we recommend buying the components?

By the way can you send or scan what you have from Tannoy, so I can make sure there are no errors.

Before you build you will have to get some electronics books, and study, as if you don't understand it, you will make errors and won't be able to test the crossover.

Do you have the port specs? That will be crucial. Your box must be of the same internal volume as the Tannoy box, and the ports must be exactly the same.

I will see your reply later, I'm going out to resume repairs on my Willys Jeep. I have the fuel system apart but going back together now.

You can post back to me now. Willy's is running sweetly.

 

[Face`]

www.PartsExpress.com
www.Madisound.com
www.SonicCraft.com
www.PartsConnexion.com

Unfortunately, Radio Shack is almost useless to DIYer's these days.

 

[TLS Guy]

I understand enough of the drawing to know that there are 3 capacitors (1st, 2nd, and 3rd order) as well as 3 coils. I don't know what the B1 stands for.

I live in the Baltimore area but I wasn't sure if I could get these components from a place like Radio Shack or if I should be looking at a more specialized store.

As for the volume of the box, the specs on the speakers say that it is 17 liters. I am a skilled carpenter and am fully capable of building an appropriate box.

I have asked Tannoy for the port specs and I'm still awaiting their reply.

Our posts crossed I see. Willys is running fine!

No you don't understand. There are two capacitors and the two inductors forming a fourth order high pass filter. That is C1, C2, L1 and L2. L3 and C3 form a second order low pass filter.

B1 is a thermister, to protect the tweeter from damage. It will limit current and reset automatically.

The caps and inductors I can spec from Madisound. I will do this for you this evening. The thermister will be a slight problem, I will try and source it from Digi-Key. I have a commercial account with them. If I draw a blank there, I will try Mousser.

Now when you come to build it, lay out of the components is crucial. You have to lay the coils out in a fashion, that minimizes cross inductance. This is very important on a high powered speaker like that.

If you don't feel comfortable doing this, I can build the crossovers for you.

There will be significant component cost for these crossovers, I'm guessing the components will come to about $100, but we will see.

 

[l33tfr34k]

TLS guy

Oh, thank you for clarifying, the primary reason that I wanted to build the crossovers myself was in order to learn more about them. I have been doing a lot of research into it, obviously I still have a long way to go. I work in technical theater and I figured this would great opportunity to learn more about how a crossover works.

I also didn't realize that these would cost that much, I am much less willing to try myself and make a mistake in a $100 crossover, not to mention what it would do to the drivers. So I may take you up on your offer to build them for me.

But for now thank you for the offer to spec the components for me.

 

[Face`]

The thermister will be a slight problem, I will try and source it from Digi-Key. I have a commercial account with them. If I draw a blank there, I will try Mousser.

Could you use a poly switch instead?

 

[Swerd]

Components from Madisound

C1 - 2.7 µF - Bennic poly $1.55

C2 - 8.2 µF - Bennic poly $4.05

C3 - 12 µF - Bennic poly $4.90

L1 - 1.0 mH - 19g Air Core Inductor $5.50

L2 - 0.7 mH - 19 g Air Core Inductor $4.95

L3 - 1.5 mH - Sidewinder 16 g Air Core Inductor $14.75

Total for all parts other than the two thermisters = $71.40

 

[TLS Guy]

Components from Madisound

C1 - 2.7 µF - Bennic poly $1.55[/UR

C2 - [URL="http://www.madisound.com/catalog/product_info.php?manufacturers_id=122&products_id=141"]8.2 µF - Bennic poly $4.05

C3 - 12 µF - Bennic poly $4.90

L1 - 1.0 mH - 19g Air Core Inductor $5.50

L2 - 0.7 mH - 19 g Air Core Inductor $4.95

L3 - 1.5 mH - Sidewinder 16 g Air Core Inductor $14.75

Total for all parts other than the two thermisters = $71.40

There are two more items you will need in addition to the thermisters. You will need two circuit boards, for a total of $28.

You will need two terminal cups, for a total of $11.40.

The Thermisters I can come to a close approximation. The thermister in addition to providing tweeter protection is also padding the tweeter. The spec is 12 Volt, 21 watt, which means the thermister has a resisitance of 6.8 ohm. The closest I can come is two 10 ohm thermisters in parallel which would be 12 volt, 18 watt. That difference is only a fraction of a db, so will be quite satisfactory. So you will need four of these thermisters sourced from Mouser for a total of $3.72. I struck out with digi-key.

So your total for electronic parts will come to $114.52. So I was pretty close at $100 off the top of my head.

Now when you build your enclosure, use at least 3/4 mdf or cabinet grade ply wood. You will need to brace well, or it will ring like a barrel. Vertical and horizontal internal braces need placing every nine inches. You need to cover 50% of the internal surfaces with Rockwool (mineral wool). Make sure you cover all the back surface behind the driver with Rockwool. Apply the balance to top, sides and bottom towards the front. to prevent reflections from the driver cone.

Swerd thanks for helping with the heavy lifting.

 

[Swerd]

There are two more items you will need in addition to the thermisters. You will need two circuit boards, for a total of $28.

You will need two terminal cups, for a total of $11.40.

The Thermisters I can come to a close approximation. The thermister in addition to providing tweeter protection is also padding the tweeter. The spec is 12 Volt, 21 watt, which means the thermister has a resisitance of 6.8 ohm. The closest I can come is two 10 ohm thermisters in parallel which would be 12 volt, 18 watt. That difference is only a fraction of a db, so will be quite satisfactory. So you will need four of these thermisters sourced from Mouser for a total of $3.72. I struck out with digi-key.

So your total for electronic parts will come to $114.52. So I was pretty close at $100 off the top of my head.

Now when you build your enclosure, use at least 3/4 mdf or cabinet grade ply wood. You will need to brace well, or it will ring like a barrel. Vertical and horizontal internal braces need placing every nine inches. You need to cover 50% of the internal surfaces with Rockwool (mineral wool). Make sure you cover all the back surface behind the driver with Rockwool. Apply the balance to top, sides and bottom towards the front. to prevent reflections from the driver cone.

Swerd thanks for helping with the heavy lifting.

l33tfr34k

TLS Guy knows what he is talking about. I'd pay close attention to any details he suggests. There is, however, one small point of his that I wonder if it is necessary - the circuit boards. I have built crossovers on small boards (¼" masonite, pegboard, scrap wood, etc.) and wired the components directly together. A circuit board may be a nice feature, but is there any reason why it is needed?

TLS - glad I could help .

Also, I believe you mentioned you live in the Baltimore area. I'm not too far away in Gaithersburg. If you need any more direct help, send me a PM. I also have a friend in Bethesda who has a full speaker measurement rig and would be glad to run some frequency response scans of your work when you're done. It may seem unnecessary but after all that work, its nice to verify that you've done nothing wrong. And if you need to trouble shoot something you don't understand, its the best way to proceed.

I forgot to add this to my previous post. Capacitors and resistors (What about thermisters?) may be placed anywhere on the board without problem, but you should follow certain conventions for placing the inductors. I find this diagram very helpful.

 

[TLS Guy]

Neat electronics is generally good electronics. A good circuit board really helps, and good ones like the ones I suggested give you a good ground plane.

The OP has a high quality unit there, and if he wants the best out of it, he needs to maintain quality through out his project. After all he will end up with a unit way below cost for the performance.

 

[Guiria]

I've built xovers using 1/8 and 1/4 inch hardboard and printed circuit boards. My opinion is that the prefab circuit boards were easier to assemble and faster overall in xover assembly. I will probably use them in the future unless cost is a huge factor for the specific build.

Just to echo Swerd, TLS_Guy knows his stuff. I've built a pair of bookshelf speakers following TLS recommendations and they are a very nice set of speakers today (even though I had some major box building issues, but what can I say it was my first pair ).

 

[l33tfr34k]

Do you have the port specs? That will be crucial. Your box must be of the same internal volume as the Tannoy box, and the ports must be exactly the same.

I will see your reply later, I'm going out to resume repairs on my Willys Jeep. I have the fuel system apart but going back together now.

The rep from Tannoy told me that there are 4 ports 1 ¼” in diameter, 2 5/8” long.

TLS Guy-

Congrats on getting your jeep working. BTW that is one uber nice sound system you got there. I'm running 2 JBL 4655, on a Sony STR-DG820. Its a little under powered but it does allow me to add 5 more speakers to the system.

 

[Swerd]

The rep from Tannoy told me that there are 4 ports 1 ¼” in diameter, 2 5/8” long.

Parts Express has a better selection of port tubes, but none of them are exactly 1¼" internal diameter.

I see 1 1/8", 1 3/8", and 1½", but none that are 1¼". You can easily cut them to the appropriate length with a hacksaw. Perhaps you can find some PVC drain pipe in the right size.

TLS Guy - How much latitude is there is with port diameter? It should be possible to tune a larger diameter port correctly by making it longer. Doesn't Bass Box calculate that?

 

[TLS Guy]

The rep from Tannoy told me that there are 4 ports 1 ¼” in diameter, 2 5/8” long.

TLS Guy-

Congrats on getting your jeep working. BTW that is one uber nice sound system you got there. I'm running 2 JBL 4655, on a Sony STR-DG820. Its a little under powered but it does allow me to add 5 more speakers to the system.

If you use 1 3/8" ports then their length needs to be 3.4". If you use 1.5" ports the length needs to be 4 1/4". If you have room for the 1.5" ports, use those as vent velocity will be lower. Those port lengths are for flush non flared ports.

So now you can get building. Please post pictures.

One other thing you should ask Tannoy is the resistance of those thermisters at normal ambient temp with minimal current, 1 ma say. I had to make some assumptions, as they never quoted the temperature at which 12 volts across the thermister resulted in dissipation of 21 watts. It would be nice to confirm the assumption I had to make.

 

[TLS Guy]

Parts Express has a better selection of port tubes, but none of them are exactly 1¼" internal diameter.

I see 1 1/8", 1 3/8", and 1½", but none that are 1¼". You can easily cut them to the appropriate length with a hacksaw. Perhaps you can find some PVC drain pipe in the right size.

TLS Guy - How much latitude is there is with port diameter? It should be possible to tune a larger diameter port correctly by making it longer. Doesn't Bass Box calculate that?

Yes, you can see that even small changes in port diameter result in significant changes in length.

 

[lsiberian]

You guys seem to have a had a lot of fun while I was gone.