Help making a passive crossover

[l33tfr34k]

I need some help on how to make a passive crossover for some speakers I just got. The speakers are Tannoy DC8i's and have a crossover frequency of 1.7kHz.

Speaker Specs
Frequency Range 1 62Hz - 45kHz
System Sensitivity (1W @1m) 2 92dB (1W = 2.83V for 8 Ohms)
Dispersion (-6dB) 90 degrees conical
Driver Complement 1 x 200mm (8.00”) constant directivity Dual Concentric™
Crossover Passive 1.7kHz with dynamic HF protection
Directivity Factor (Q) 5.7 averaged 1kHz to 10kHz
Directivity Index (DI) 7.0 averaged 1kHz to 10kHz
Rated Maximum SPL Average: 113dB
Peak: 119dB

Power Handling Average: 130W
Programme: 260W
Peak: 520W

Recommended Amplifier Power 100 - 260W @ 8 Ohms
Nominal Impedance 8 Ohms
Distortion 10% Full Power (8.94V)
2nd Harmonic
250Hz: 0.4%
1kHz: 0.28%
10kHz: 1.50%
3rd Harmonic
250Hz: 0.35%
1kHz: 0.66%
10kHz: 0.35%

1% Full Power (2.83V)
2nd Harmonic
250Hz: 0.11%
1kHz: 0.12%
10kHz: 0.51%
3rd Harmonic
250Hz: 0.15%
1kHz: 0.34%
10kHz: 0.17%


I have never made a crossover before and have been doing a lot of research but still find the process confusing. Can anyone help me?

 

[highfigh]

I need some help on how to make a passive crossover for some speakers I just got. The speakers are Tannoy DC8i's and have a crossover frequency of 1.7kHz.

Speaker Specs
Frequency Range 1 62Hz - 45kHz
System Sensitivity (1W @1m) 2 92dB (1W = 2.83V for 8 Ohms)
Dispersion (-6dB) 90 degrees conical
Driver Complement 1 x 200mm (8.00”) constant directivity Dual Concentric™
Crossover Passive 1.7kHz with dynamic HF protection
Directivity Factor (Q) 5.7 averaged 1kHz to 10kHz
Directivity Index (DI) 7.0 averaged 1kHz to 10kHz
Rated Maximum SPL Average: 113dB
Peak: 119dB

Power Handling Average: 130W
Programme: 260W
Peak: 520W

Recommended Amplifier Power 100 - 260W @ 8 Ohms
Nominal Impedance 8 Ohms
Distortion 10% Full Power (8.94V)
2nd Harmonic
250Hz: 0.4%
1kHz: 0.28%
10kHz: 1.50%
3rd Harmonic
250Hz: 0.35%
1kHz: 0.66%
10kHz: 0.35%

1% Full Power (2.83V)
2nd Harmonic
250Hz: 0.11%
1kHz: 0.12%
10kHz: 0.51%
3rd Harmonic
250Hz: 0.15%
1kHz: 0.34%
10kHz: 0.17%


I have never made a crossover before and have been doing a lot of research but still find the process confusing. Can anyone help me?

What happened to the original crossover? You get them with the original drivers? If so, can you contact Tannoy and get a schematic for the correct network?

 

[l33tfr34k]

I got the speakers from a theater that was getting rid of them, if there had been crossovers and enclosure with the speakers original they were gone by the time i got the speakers. So all I have are the driver/cone assembly.

 

[TLS Guy]

I got the speakers from a theater that was getting rid of them, if there had been crossovers and enclosure with the speakers original they were gone by the time i got the speakers. So all I have are the driver/cone assembly.

Unfortunately manufacturers keep the data I would need to design a crossover proprietary. I need the T/S parameters of the woofer and concentric tweeter as well as full acoustic date for both drivers to even begin.

If you don't do this correctly and muck about you will almost certainly destroy the tweeter.

You will have to persuade Tannoy to provide us that data or crossover circuit. Failing that you will have to buy the correct crossovers from Tannoy.

The other issue is that you need the T/S parameters to design and build enclosures for them. This is a complicated project and without the cooperation of Tannoy, pretty close to impossible. The only way out of your problem other wise, is to measure the T/Sparameters, which is easy enough, but measuring the acoustic data is a much bigger task.

Tannoy dual concentrics are excellent drivers by the way, so it would be worth trying to salvage the drivers, but I think you will be boating upstream.

I would start with Tannoy and honestly explain your situation to them. I have heard they are a very nice bunch.

 

[l33tfr34k]

Thank you, I will try talking with Tannoy in order to get those specs. If that doesn't work I can potentially get the acoustic data since I am a student at a university and have access to the recording studios and other audio equipment. I will continue to post with updated information.

 

[l33tfr34k]

Upon more digging at the theater I got the speakers from I discovered that I was mistaken. The speakers are DC8i's but are instead i8 speakers. I believe that this series has been discontinued because I can't find them on Tannoy's website.

This probably doesn't change the my basic problem but if anyone has some crossovers or knows that specs for i8 speakers can you please let me know.

 

[highfigh]

Upon more digging at the theater I got the speakers from I discovered that I was mistaken. The speakers are DC8i's but are instead i8 speakers. I believe that this series has been discontinued because I can't find them on Tannoy's website.

This probably doesn't change the my basic problem but if anyone has some crossovers or knows that specs for i8 speakers can you please let me know.

You might want to look at the authorized service shops and specifically, for the ones who have been working on Tannoy the longest. They should have the documentation you need.

 

[Guiria]

If your budget isn't super tight you might invest in something like this.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=390-804

The woofer tester will allow you to get the acoustic data you need to begin designing a xover, or atleast enough data to hand over to TLS_Guy for his help.

Good Luck.

 

[TLS Guy]

If your budget isn't super tight you might invest in something like this.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=390-804

The woofer tester will allow you to get the acoustic data you need to begin designing a xover, or atleast enough data to hand over to TLS_Guy for his help.

Good Luck.

T/S data alone will not let you deign a crossover. You need accurate acoustic data also, especially knowing were the break up peaks are, and the natural roll offs of the drivers.

 

[Guiria]

T/S data alone will not let you deign a crossover. You need accurate acoustic data also, especially knowing were the break up peaks are, and the natural roll offs of the drivers.

When you are saying "acoustic data" you mean the natural free air response curve of the drivers correct? So the OP would need a tone generator, calibrated microphone, amplifier to connect to the raw drivers and data tracking software such as REW, TrueRTA or Bassbox Pro, (to name a few) so he can graph the speakers response?

Half of what I'm saying is for my own benefit if/when I jump into designing my own crossover, I want to make sure I have everything necessary. Which brings up another concern, if you don't have a capable microphone (I consider the RS SPL meter not sufficient for full audio spectrum measurements) then you are really hurting your design from the beginning.

Hmm...I may stick to drivers that have this data available from the manufacturer

 

[TLS Guy]

When you are saying "acoustic data" you mean the natural free air response curve of the drivers correct? So the OP would need a tone generator, calibrated microphone, amplifier to connect to the raw drivers and data tracking software such as REW, TrueRTA or Bassbox Pro, (to name a few) so he can graph the speakers response?

Half of what I'm saying is for my own benefit if/when I jump into designing my own crossover, I want to make sure I have everything necessary. Which brings up another concern, if you don't have a capable microphone (I consider the RS SPL meter not sufficient for full audio spectrum measurements) then you are really hurting your design from the beginning.

Hmm...I may stick to drivers that have this data available from the manufacturer

You have it correct. That is why I stick pretty much to European drivers, as you can believe the acoustic data. SEAS are brutally honest in what they publish. I have a suspicion a lot of data on Far Eastern drivers is too good to be true!

 

[highfigh]

You have it correct. That is why I stick pretty much to European drivers, as you can believe the acoustic data. SEAS are brutally honest in what they publish. I have a suspicion a lot of data on Far Eastern drivers is too good to be true!

OTOH, most of the European companies now have at least some of their drivers made in China. It's unfortunate but as long as they live up to the design criteria and spec out when they're tested, it's about the only way they can keep their costs down.

 

[Face`]

Tannoy sometimes uses funky crossover designs. Their newer speakers, with the tulip style tweeter(what you have) usually have a 1st order crossover with a 2nd order from the woofer to the tweeter.

Which means, the tweeter probably has a 2.4-3.0uf cap in series with it, and the woofer has a inductor in series with a cap around 30uf in the shunt position. Those values are approximate and based off of the Saturn S8/S8C/S8LR's I've hot rodded.

There is a Tannoy Yahoo group, but I'm not sure how much help you'll get there since 95% of the members there own vintage drivers such as the old Monitor Red/Gold/HPD's.

Mike

 

[TLS Guy]

Tannoy sometimes uses funky crossover designs. Their newer speakers, with the tulip style tweeter(what you have) usually have a 1st order crossover with a 2nd order from the woofer to the tweeter.

Which means, the tweeter probably has a 2.4-3.0uf cap in series with it, and the woofer has a inductor in series with a cap around 30uf in the shunt position. Those values are approximate and based off of the Saturn S8/S8C/S8LR's I've hot rodded.

There is a Tannoy Yahoo group, but I'm not sure how much help you'll get there since 95% of the members there own vintage drivers such as the old Monitor Red/Gold/HPD's.

Mike

And if you are wrong it is a blown tweeter. It would be most unusual to use a single cap first order filter with a crossover that low.

 

[TLS Guy]

Tannoy sometimes uses funky crossover designs. Their newer speakers, with the tulip style tweeter(what you have) usually have a 1st order crossover with a 2nd order from the woofer to the tweeter.

Which means, the tweeter probably has a 2.4-3.0uf cap in series with it, and the woofer has a inductor in series with a cap around 30uf in the shunt position. Those values are approximate and based off of the Saturn S8/S8C/S8LR's I've hot rodded.

There is a Tannoy Yahoo group, but I'm not sure how much help you'll get there since 95% of the members there own vintage drivers such as the old Monitor Red/Gold/HPD's.

Mike

I have found the i8 manual.

The crossover is fourth order high pass, not first, and second order low pass.

I seem to remember the vintage Golds, Red etc. had a tapped choke and switched variable L-pad, and was second order high pass. The unusual feature, was the tapped choke in the second order high pass filter.

One word of advice. Don't publish crucial advice or facts you are uncertain of, which if you are wrong about, could lead a member to do damage to a piece of equipment.

In this case suggesting a first order crossover for the OP's driver falls into this category.

 

[Face`]

I have found the i8 manual.

The crossover is fourth order high pass, not first, and second order low pass.

I seem to remember the vintage Golds, Red etc. had a tapped choke and switched variable L-pad, and was second order high pass. The unusual feature, was the tapped choke in the second order high pass filter.

One word of advice. Don't publish crucial advice or facts you are uncertain of, which if you are wrong about, could lead a member to do damage to a piece of equipment.

In this case suggesting a first order crossover for the OP's driver falls into this category.

I understand where you're coming from.

Here's the specifications on Tannoy's Saturns: http://www.hnny.nl/archief_tannoy/saturn/manual_eng.pdf

The crossover is a first order at 1.5 kHz, which they attain by using a 2.4uf cap in series with the tweeter. A cap that small on the tweeter will probably start to roll off around 8-10 kHz, but probably drops like a rock around 1.5 kHz. But neither of us would know for sure without having it in our hands and measuring it. Since the tweeters are similar(both tulip waveguides), I thought it would be a step in the right direction.

Funny you mention the HPD's, I recently removed the autoformer with mine and replaced it with a 3.9mH foil inductor. Along with a couple of other small changes in the HF circuit, it now measures flatter than before.

 

[l33tfr34k]

Thank you guys for all the helpful advice and information. I emailed Tannoy last week and they sent me the schematics on the crossover (which I can't seem to post on the forum page). So I shall attempt to draw it.

```````````````` c1````````````c2 ```````````__ B1
+________o______||______o______||______o_____\ /_______-
Input`````|`````````````}L1```````````}L2``````````````HF
-___o____o _____________o______________o______________+
````|````|
````|````|`````````````L3
````|````|____________^^^_________o_________________+
````|``````````````````````````````|
````|``````````````````````````````==C3```````````````LF
````|_______________________________|_________________-


I hope that makes sense, its the best I can do.

Please ignore the apostrophe marks I only added them so that my white spaces didn't disappear

 

[Guiria]

Thank you guys for all the helpful advice and information. I emailed Tannoy last week and they sent me the schematics on the crossover (which I can't seem to post on the forum page). So I shall attempt to draw it.

```````````````` c1````````````c2 ```````````__ B1
+________o______||______o______||______o_____\ /_______-
Input`````|`````````````}L1```````````}L2``````````````HF
-___o____o _____________o______________o______________+
````|````|
````|````|`````````````L3
````|````|____________^^^_________o_________________+
````|``````````````````````````````|
````|``````````````````````````````==C3```````````````LF
````|_______________________________|_________________-


I hope that makes sense, its the best I can do.

Please ignore the apostrophe marks I only added them so that my white spaces didn't disappear

Did they send you the values for C1, C2, B1, etc? If so you should list them on the forum.

 

[l33tfr34k]

C1 - 2.7uF
C2 - 8.2uf
C3 - 12uf
*All C values are + or - 10%

L1 - 1.0mH
L2 - 0.7mH
L3 - 1.5mH

B1 - 12V/21W

 

[TLS Guy]

Did they send you the values for C1, C2, B1, etc? If so you should list them on the forum.

Yes, that makes sense. It is fourth order high pass and second order low pass. The manual gives box dimensions, so you can get the volume. You will need to find out the port dimensions, from Tannoy. That was very decent of them to pass that information along to you. However "back in the days", all decent British audio gear came with full schematics as standard procedure. All gear should now in my view.

Let us know how your project develops. It seems you are set to have a fairly expensive item on the cheap: - Pennies from Heaven.