HB1 alternative tweeter with Vifa M21(?)

jervill

Member
2010-08-01 2:35 am
Hello guys,

Disclosure: I know next to nothing about speaker design. (Ive only ever added BSC and Zobels to full range drivers.) I'm only starting to learn about it really. I may make a lot of wrong conclusions or attributions so bear with me.

I refurbished an old pair of Heybrook HB1 last year and have been listening to them since. For me, it sounds very good at low to moderate level. Louder, it gets bright and male vocals take on, what i describe as, a subtle 'electronic' tone. Ive tried different amps and it sounds best with an F4, with what I have, as that cranks up gracefully.

I've attributed this, I thought, to the old tweeters and started looking for an alternative tweak perhaps. I also went to look at the specs of the M21 and the HB1 (speakers before my time)... The M21's graph response looks close to a bass woofer's to me and Heybrook crosses the tweeter at 4khz?? Shows really what I dont know or understand about crossover points...

Now I'm thinking that the 'male voice funkiness' I'm picking up is the the cone break up or xover perhaps (someone correct me). This then has got me thinking of whether its worth looking for tweeters that can cross lower than the original vifa D25, from say 2k-2.5khz LR2 to keep simple. Am I thinking about this the right way?

The M21 are new production, not refoamed. It looks like they were used by Snell and JPW as well. Where did the other designers choose to cross along that graph?

Anyway, thoughts and recommendations please.
 

giralfino

Member
2009-02-28 9:20 pm
A 4KHz crossover point is clearly not optimal for the woofer as it already beams at this frequency, but I don't think there is a breakup problem, as in this respect the woofer seems controlled.
I don't know how old the speaker is, but if it is 15-20 or more years old, you probably should replace all electrolytic caps, as they change value over time. Replace them with new same specs caps (same value audio bipolar electrolytic caps). No need to replace film caps, resistors or coils if they are not damaged.
A photo of the crossover board could be useful.

Ralf
 

jervill

Member
2010-08-01 2:35 am
A 4KHz crossover point is clearly not optimal for the woofer as it already beams at this frequency, but I don't think there is a breakup problem, as in this respect the woofer seems controlled.
I don't know how old the speaker is, but if it is 15-20 or more years old, you probably should replace all electrolytic caps, as they change value over time. Replace them with new same specs caps (same value audio bipolar electrolytic caps). No need to replace film caps, resistors or coils if they are not damaged.
A photo of the crossover board could be useful.

Ralf

Thank you. The woofer is new production, the tweeter is the original from the early 80s. I recapped them although they had film caps originally, I'd already bought caps thinking they were going to be electrolytics inside.

Seeing that youre of the opinion that 4khz may not be optimal, would a slightly lower xover like 3khz-3.5khz 2nd order with a tweeter like the Vifa D27TG be of benefit?

Thanks.
 
This is my kind of speaker, but, maybe as you have found it cannot t take a lot of power.

Hmm, are the cabinets still sound, does the tweeter on this model sit in its own mini enclosure?
Double check you have connected everything back up correctly to maintain the original design phasing

Giralfino is absolutely correct about beaming, for a 8" driver this can occur at approx. 1.8Khz or thereabouts. Not many cheap tweeters will allow that crossover point and it takes time to weed out the ones that will do it and give a sensible match to the woofer's crossover slope.

Within the original design constraints they work well. Applying modern day practices and knowledge exposes some weaknesses.

Can you easily disconnect the tweeter and listen to the bass on its own? Does it still fail your criteria when you turn up the volume?
With the original bass roll off at circa 4Khz you might be amazed how well it does without the tweeter. However walk around the listening area and you should be able to hear the beaming effect of the 8" cone as the image collapses as you walk past the 30 degree points of a speaker

If the bass and colouration you mention is Ok by your criteria, then maybe the tweeter levels could be the next thing to investigate. To finalise this you will need some measurements to meld the woofer and a new tweeter together.
Let us know how you get on.
 
The Vifa M21 is the original well-behaved midbass:
Vifa M21WG-09-08 Woofer - Heybrook HB1, JPW P1, AP2, AP3 replacement

You may find some of my experiments useful:
Restoring Monitor Audio R300 bookshelf speakers.

694035d1532786073-sb26adc-compared-sb29rdc-3rd-kef-style-png


714065d1541548033-restoring-monitor-audio-r300-bookshelf-speakers-ma-r300-md-4th-fr-png


That sort of thing works well enough. Fresh tweeter ferrofluid available here, because it can dry up over the years:
Blue Aran - The UK's no.1 Loudspeaker Component Stockist > Sonitus Audio > High Frequency Drivers > Ferrofluid
 

jervill

Member
2010-08-01 2:35 am
Heres the outward refurb:

Jeremy on Instagram: “Refurbishing an old High St. favourite. The Heybrook HB-1 from the 80s. Main drivers changed to current build ones (same model), fancy…”

The cabs were in great condition, even better after the wood veneer sides and fresh vinyl wraps for the front and back. I did inquire if the inside was original. Apparently it is, complete with the original long hair wool stuffing. I did convert the binding posts for bi-amp. There were only parallel caps to the tweeter and I wanted a SET to drive the top and F4 on the bottom.

Raymondj, you might be right. Maybe i am finding that it doesnt take a lot of power. But, I actually like them more than I imagined I would. I got them as my entry level learning pair. (I knew nothing of or even heard of Heybrook then. The criteria was that the model returned on a search, easily bought replacement drivers lol). After hearing them though, I decided to refurb the outside and get fresh woofers and listen for a while. This was over a year ago and this effort of mine now is seeing if theres mileage to be had tweaking and improving. Im going to try your suggestions, thanks.

System7, I'll have a read. I've not considered looking at the ferrofluid, thanks for the lead. Reading around has made me realise that the M21 was used by a lot of manufacturers. What intrigues me is that the original Snell K used them. Last time I saw original K's on offer was near 400 quid (rare) yet HB1s go for under a hundred (often). Is that just because it sold by the thousands here or does the price reflect the actual performance between the two? Anyway, I digress.
 
Heres the outward refurb:

Jeremy on Instagram: “Refurbishing an old High St. favourite. The Heybrook HB-1 from the 80s. Main drivers changed to current build ones (same model), fancy…”

The cabs were in great condition, even better after the wood veneer sides and fresh vinyl wraps for the front and back. I did inquire if the inside was original. Apparently it is, complete with the original long hair wool stuffing. I did convert the binding posts for bi-amp. There were only parallel caps to the tweeter and I wanted a SET to drive the top and F4 on the bottom.

Raymondj, you might be right. Maybe i am finding that it doesnt take a lot of power. But, I actually like them more than I imagined I would. I got them as my entry level learning pair. (I knew nothing of or even heard of Heybrook then. The criteria was that the model returned on a search, easily bought replacement drivers lol). After hearing them though, I decided to refurb the outside and get fresh woofers and listen for a while. This was over a year ago and this effort of mine now is seeing if theres mileage to be had tweaking and improving. Im going to try your suggestions, thanks.

System7, I'll have a read. I've not considered looking at the ferrofluid, thanks for the lead. Reading around has made me realise that the M21 was used by a lot of manufacturers. What intrigues me is that the original Snell K used them. Last time I saw original K's on offer was near 400 quid (rare) yet HB1s go for under a hundred (often). Is that just because it sold by the thousands here or does the price reflect the actual performance between the two? Anyway, I digress.

Going by what I've read over the years the order from best to worst sounding speaker is: Snell K, JPW P1/AP2/AP3 (JPW is supposed to be quite close though) and finally the HB1. I have heard people say the HB1 sounds a bit rough.
 

jervill

Member
2010-08-01 2:35 am
This is my kind of speaker, but, maybe as you have found it cannot t take a lot of power.

Hmm, are the cabinets still sound, does the tweeter on this model sit in its own mini enclosure?
Double check you have connected everything back up correctly to maintain the original design phasing

Giralfino is absolutely correct about beaming, for a 8" driver this can occur at approx. 1.8Khz or thereabouts. Not many cheap tweeters will allow that crossover point and it takes time to weed out the ones that will do it and give a sensible match to the woofer's crossover slope.

Within the original design constraints they work well. Applying modern day practices and knowledge exposes some weaknesses.

Can you easily disconnect the tweeter and listen to the bass on its own? Does it still fail your criteria when you turn up the volume?
With the original bass roll off at circa 4Khz you might be amazed how well it does without the tweeter. However walk around the listening area and you should be able to hear the beaming effect of the 8" cone as the image collapses as you walk past the 30 degree points of a speaker

If the bass and colouration you mention is Ok by your criteria, then maybe the tweeter levels could be the next thing to investigate. To finalise this you will need some measurements to meld the woofer and a new tweeter together.
Let us know how you get on.

For posterity and update of this thread. After a few months of faffing with this learning experience, just before lockdown, I found the cause of the Male voice anomalies. After swapping out amps checking it out, I swapped the plain wire with a fancier copperline cable. Cleared up the sound 'miraculously'. Since I'm dubious of cable talk, I opened up the crossover/binding post to look for the difference. Found it. A cold solder on the binding post itself. Since its wired direct to the components, it was stiff enough to make the connection but would vibrate when excited, noticeably for me on Male vocals. When the heavier Copperline cables with the WBT terminations were used, it stopped the binding post contact vibrating and causing sound anomalies. Now that I've resoldered everything, all works well.

Ive been back to trying to learn more about speaker building and contemplating a project based off these sealed M21, maybe a three way for the same Vb. Hard going 😂😂
 
Hi Jervill,

Great to hear that you got to the bottom of what was bothering you, and you have fixed it. Interesting what a poor electrical joint can do to the sound more so when its in a vibrating loudspeaker cabinet ?

In terms of future plans for the Vifa paper cone what were you thinking of doing? Lowering the crossover and using a more modern tweeter that can go lower?

Keep us posted.