Impulse H2 Speakers Crossover help please?

[AJSki2fly]

I have been considering hopefully improving the sound of my lovely Impulse H2 speakers. Initially I thought I would replace the capacitors in them as they are probably getting a bit old in the tooth by now. H2 builds varied quite a bit over the years I believe, mainly the siting of the crossover. Mine has the crossover on the inside mounted on a board that is secured to the rear of the cabinet by 6 screws, on the outside of this board is where the 6 speaker posts are. It is quite straight forward to get the board off but with limited movement due to the length of the internal leads to the speakers.

I removed and have examined the crossover circuit which looks quite straight forward, two large capacitors and one smaller one, all are black and I think oil filled ones but I could be wrong, by the way I have limited electronics knowledge. I examined the capacitors carefully looking for markings to indicate what voltage and microfarads they are rated as with a view to ordering high quality replacements. Unfortunately they seem to be completely unmarked :doh:.

I have searched the internet for crossover wiring diagrams for the H2's but can find none, I did find some pictures of a redesigned crossover for an upgraded pair and also a pair of Taus (the last version of H2's that look slightly different). But in both cases the circuits look a bit different, probably I believe due to the tweeters being replaced and I suspect an upgrade to improve the top/mid range crossover point.

If anyone has any info or could guide me in the right direction it would be appreciated. I was hoping to do the simple capacitor swap myself, and then to look at making a minor mod to the circuit to improve a 450hz dB drop (I believe this is a standard tweak).

[killie99]

Here you go. Have a look at http://www.acoustica.org.uk/ for lots of info on Impulse. I had H2's and Taus for many years, loved them.

https://i.postimg.cc/c1KpGs2v/H2-Taus-crossover.jpg

[killie99]

After loads of experimenting I used a Jantzen Superior Zcap in the tweeter and a Clarity Cap TC Poly in the mid and changed all the inductors for Jantzen air cores. Might be worth speaking to Paul at Reference Fidelity Components as he developed a completely new crossover which is supposed to be very good.

[AJSki2fly]

After loads of experimenting I used a Jantzen Superior Zcap in the tweeter and a Clarity Cap TC Poly in the mid and changed all the inductors for Jantzen air cores. Might be worth speaking to Paul at Reference Fidelity Components as he developed a completely new crossover which is supposed to be very good.

Hi Stuart

That's very helpful, at least I know the values of the Caps, resistors and inductors, so I can decide what to do. Yes I have spoken with Paul some time ago but I am on a limited budget and his prices are too much for me, plus I think I would like to try myself. I have also spoken with another chap who has worked on several H2's and has told me the crossover can be improved with better components and the addition of a resistor to get rid of the mid-range dip at 450hz. So I will price the parts up and decide what to do.

By the way why did you replace the inductors with air cores, is it because they are more stable?

Many thanks

Adrian

[killie99]

I changed them because I thought they improved the sound - i thought the air core inductor in the bass gave much better control. As I said, I experimented with lots of components and built my final crossovers with what I thought sounded best.

[AJSki2fly]

I changed them because I thought they improved the sound - i thought the air core inductor in the bass gave much better control. As I said, I experimented with lots of components and built my final crossovers with what I thought sounded best.

That makes sense from what I read about ferrite core ones, I believe the air core should be better. Thanks

[killie99]

here's a pic of the xo's I built, note £1 coin to give an idea of the size!

https://i.postimg.cc/SK1hF4r9/tausxo.jpg

[AJSki2fly]

here's a pic of the xo's I built, note £1 coin to give an idea of the size!

https://i.postimg.cc/SK1hF4r9/tausxo.jpg

Thanks, that looks good, am I right that the brown is tweeter, blue is mid and red is bass? I see you kept the inductors as far apart as possible and at 90 degrees to each other to minimise interference. I can see from the size it's not very practical to fit inside the speaker, and presumably heavy with the air core inductors.

Thanks again

Adrian

[killie99]

Yes that's correct with the colours and I put coloured speaker connectors on the speakers and used coloured heatshrink on the cables linking the crossover to the speakers to minimise the risk of connecting things up wrong! The bass inductor was very heavy, think it weighed about 700g. The crossover boxes weren't too big, you can see them here beside the speakers:

https://i.postimg.cc/TYmHRcCP/taus.jpg

[Mr.Ian]

Hi Stuart

That's very helpful, at least I know the values of the Caps, resistors and inductors, so I can decide what to do. Yes I have spoken with Paul some time ago but I am on a limited budget and his prices are too much for me, plus I think I would like to try myself. I have also spoken with another chap who has worked on several H2's and has told me the crossover can be improved with better components and the addition of a resistor to get rid of the mid-range dip at 450hz. So I will price the parts up and decide what to do.

By the way why did you replace the inductors with air cores, is it because they are more stable?

Many thanks

Adrian

HI Adrian, how did this work out in the end, was it worthwhile?, what parts did you use?. I am thinking of doing the same Ian

[AJSki2fly]

HI Adrian, how did this work out in the end, was it worthwhile?, what parts did you use?. I am thinking of doing the same Ian

Hi Ian,

Well after much contemplation I was about to do the cross-overs when my best friend suggested I tried out his Vienna Acoustic Mozart Grands SE's, he had kept them after upgrading 2 years earlier. I listened to them for 2 months and came to the conclusion that they worked better in my room than the H2's and I did not want to spend money out on the H2's and still not get what I wanted. Also my wife was rather pleased that the size of the Vienna was a reduction in size in the lounge. Since then another friend gave me a pair of JBL L100's, I am very impressed with these and have been using them quite a lot and they are staying.

[Mr.Ian]

Jbl l100, look interesting and appreciating but think on reflection I will stick with my h2, and leave as standard they are visually mint condition

[Edward]

Ian, recently Paul at RFC did a restore on my Tannoy crossovers replacing all the caps, some resistors and stripped down/fixed other stuff. As part of the restore Paul ensured that the crossovers measured well between each other (I think within 0.5db). Transformed the sound and was much cheaper than going for external crossovers etc.

[AJSki2fly]

Ian, recently Paul at RFC did a restore on my Tannoy crossovers replacing all the caps, some resistors and stripped down/fixed other stuff. As part of the restore Paul ensured that the crossovers measured well between each other (I think within 0.5db). Transformed the sound and was much cheaper than going for external crossovers etc.

Depending on which version of H2's you have this could be a very good option, especially if you have and earlier pair with the crossover mounted higher up as there is more room. Alternatively speak with john@loudspeaker-design-restoration.co.uk he knows H2's very well and has a couple of minor mods for low cast that can make a big difference to the mid range.

[Mr.Ian]

Any one know what the resistor mod, is parts, values etc that gets rid of the 2.8 ohm impedance dip

[hifinutt]

very interesting thread here about active impulse speakers

https://www.hifiwigwam.com/forum/forum/8-2-channel/