Impulse H2 full restoration - photos!
- Thread starter Pac1
- Start date
Lordhenley
pfm Member
They look great Paul
Crossovers have now been designed after 2 days of measurement, simulation, design, building a prototype, measuring using impulse signals (creating a step response gated for anechoic frequency response), tweaking, rebuilding and testing again!
I found out a few interesting facts about the standard crossovers within these H2s ((assuming factory originals):
This information was used to redesign the crossover for the new drivers. The replacement mid measured very closely to the standard. The new tweeter is much more linear in response with slightly better off axis behaviour. Overall, worth changing the original to imho.
I have designed the response to have an in room dip from bass to HF of around 4 or 5dB based on a fair few soft furnishings. The speakers have retained their mid range insight/detail but don't now make your ears bleed at volume! More a listen all day sound with better imaging plus the re-balancing of units means upper bass and lower mids come to the fore better allowing more natural voice reproduction.
I found out a few interesting facts about the standard crossovers within these H2s ((assuming factory originals):
- Mid rises anechoically to +10dB with speaker well away from rear walls!
- original tweeter had a 5dB rise sting in the tail
- sensitivity seems too much (ie drive units run pretty full on) to the expense of linearity
- Major improvements can be made
- bass anechoic starts rolling off just below 50 Hz and in-room close to wall should achieve closer to 30 Hz at -6dB
This information was used to redesign the crossover for the new drivers. The replacement mid measured very closely to the standard. The new tweeter is much more linear in response with slightly better off axis behaviour. Overall, worth changing the original to imho.
I have designed the response to have an in room dip from bass to HF of around 4 or 5dB based on a fair few soft furnishings. The speakers have retained their mid range insight/detail but don't now make your ears bleed at volume! More a listen all day sound with better imaging plus the re-balancing of units means upper bass and lower mids come to the fore better allowing more natural voice reproduction.
A little more progress to update the thread.
Crossover boxes nearing completion and first crossover now built awaiting installation and wiring. This is not a standard H2 crossover but an improved (and upgraded) RFC version to match custom mids and tweeters:
The bass inductor is a bit of a beast as I wanted to use as low a DCR as possible for this one. In this case, it's barely 0.1 Ohm DCR. The rest are all air cores specifically selected for each location and all inductors are custom wound to within 1%. All caps are also matched to within 1%.
Crossover boxes nearing completion and first crossover now built awaiting installation and wiring. This is not a standard H2 crossover but an improved (and upgraded) RFC version to match custom mids and tweeters:
The bass inductor is a bit of a beast as I wanted to use as low a DCR as possible for this one. In this case, it's barely 0.1 Ohm DCR. The rest are all air cores specifically selected for each location and all inductors are custom wound to within 1%. All caps are also matched to within 1%.
Not on this Occasion Stefan, although if the owner wants it done, it will be done. This was originally planned to be a plain ply box but I veneered the sides and left the lid as a contrast.
Sound wise, I'm delighted to report that these RFC modified H2's sound absolutely sensational. They have retained the scale and dynamic impact of the originals but are in another league SQ-wise being way more balanced and natural sounding. Voices are especially natural now and the sting in the tail at the upper end doesn't exist, yet they remain open and detailed. the re-tuning has also brought the bass (especially upper bass) forwards more which helps integrate the sound so that no one aspect draws attention to itself. Very enjoyable listen indeed.
I have re-designed crossovers such that they present a much kinder load to driving amplifiers (minimum 5 Ohms, nominal 8 Ohm) compared with the original design which dipped to just 2 Ohms in the lower mids.
Sound wise, I'm delighted to report that these RFC modified H2's sound absolutely sensational. They have retained the scale and dynamic impact of the originals but are in another league SQ-wise being way more balanced and natural sounding. Voices are especially natural now and the sting in the tail at the upper end doesn't exist, yet they remain open and detailed. the re-tuning has also brought the bass (especially upper bass) forwards more which helps integrate the sound so that no one aspect draws attention to itself. Very enjoyable listen indeed.
I have re-designed crossovers such that they present a much kinder load to driving amplifiers (minimum 5 Ohms, nominal 8 Ohm) compared with the original design which dipped to just 2 Ohms in the lower mids.
Thanks Stefan.
The crossover design/values are commercially sensitive as there's other companies who deal with these, so unfortunately I cannot give any details away without shooting myself in the foot. Suffice to say, that in both measurement and listening, they are a big improvement over standard factory design. The owner hasn't seen or listened to them since he dropped them off at the start of the month, so I'm crossing fingers he'll like the final result.
The crossover design/values are commercially sensitive as there's other companies who deal with these, so unfortunately I cannot give any details away without shooting myself in the foot. Suffice to say, that in both measurement and listening, they are a big improvement over standard factory design. The owner hasn't seen or listened to them since he dropped them off at the start of the month, so I'm crossing fingers he'll like the final result.
Hot off the heals of the H2 restoration/conversion, I will be posting another thread on a pair being shipped from Norway for the same treatment plus have a pair of Impulse Taus in for conversion and external crossovers. The crossovers for these are rather special, separate thread to follow!
Mongeddavid
pfm Member
I am considering this as well. Shipping from Norway cannot be cheap lol.
laverda
pfm Member
Hope you traders dont mind my posting here as it seams the most logical as only those with an interest will be reading this post. If not I'll ask for it to be moved.
I will start a thread in DIY, on the build as it gets going but for now....
I've decided to have a bash...I'm going to build a pair of H2/Taus type clones. (hate that word) Iv'e always liked and wanted a pair of the H2's after a listen some 20...25, ah might be 28 years ago. I been looking waiting for a S/H pair but with the problems high lighted 'mids and xover 'that need a looking at' after all these years> I see my only option is to build a pair. (I'm running out of years waiting)
I have already secured the drivers (many thanks to Falcon A, very helpful) with great advise from Paul of RFC and he has agreed to spec/build test a xover upon my comlpeted build. Looking forward to a nice drive out to Dursley. I used to live in Berkely (just up the road) Loved it there.
By the by...
So if an existing owner would be willing to assist I would be eternally greatful. I need some dimensions....I cant find any details on line apart from broucure sizes (1160hx280wx450d) I can eye ball most dims there or there abouts but it would be nice to have a firm measuements I can work to.
I will be throwing up a drawing with in the next few days with required areas I need to confirm.
So...Is there anybody out there...
Thanks in advance
Graham
I will start a thread in DIY, on the build as it gets going but for now....
I've decided to have a bash...I'm going to build a pair of H2/Taus type clones. (hate that word) Iv'e always liked and wanted a pair of the H2's after a listen some 20...25, ah might be 28 years ago. I been looking waiting for a S/H pair but with the problems high lighted 'mids and xover 'that need a looking at' after all these years> I see my only option is to build a pair. (I'm running out of years waiting)
I have already secured the drivers (many thanks to Falcon A, very helpful) with great advise from Paul of RFC and he has agreed to spec/build test a xover upon my comlpeted build. Looking forward to a nice drive out to Dursley. I used to live in Berkely (just up the road) Loved it there.
By the by...
So if an existing owner would be willing to assist I would be eternally greatful. I need some dimensions....I cant find any details on line apart from broucure sizes (1160hx280wx450d) I can eye ball most dims there or there abouts but it would be nice to have a firm measuements I can work to.
I will be throwing up a drawing with in the next few days with required areas I need to confirm.
So...Is there anybody out there...
Thanks in advance
Graham
No problems RE posting on here although it might be sensible for whoever can come forward with the required dims to perhaps email Graham direct? I would have supplied them Graham but the Taus I have are to be picked up shortly and are all back together!
Martin Clark might be your man ;-)
Regards
Paul
Martin Clark might be your man ;-)
Regards
Paul