First of all my mid ranges were on the verge of foam rot, and I only discovered that after putting my butter fingers on them. The foam fell apart when I touched them. So the need for replacement in some way was absolutely necesarry.

My choice for the new elements were Peerless 830986, not so expensive but almost the same physical size and when you need 8 of them the price is some what interesting...

They were not a straight fit, the corners on the square shaped frame had to be grinded down a bit to fit the holes in the Penta baffel.

The Nokia originals:

The New Peerless elements:

A comparasion between old and new:

As seen on the last picture the old mid range fell apart totaly. You can also see the grinded corners on the frame. The grinding I did in my kitchen with a quite powerfull machine wich made the work easy and fast but it also made my kitchen look like sh-t. Picture of the sink after only two elements done, walls, floor and ceiling looked the same:

Of course all work was done while drinking beer, -work in progress:

I started with changing the elements in one speaker just to feel the difference. i discovered directly that it was not at all so good. The problem was that the midrange level now was a bit to low, hard to say so much about the quality of the sound.

To make sure it was not due to the fact that the elements were new, i left the speakes on for a few days to give them about 100 hours of music to get setteld. That made a difference but still not okay. The elements are in series 2 by 2 so I re arranged the wiring to the elements so they were connected in parallel in stead. Now the balance between the ellements felt better. I am aware of the filters being designed for the specific impedance of the original ellements and that altering the impedance also alters the frequency that the filters work with. The filters are also a bit different between the two pairs of ellements. But this modification made it more correct in my oppinion.

How sound is experienced is very difficult to put in to words, and as always it is a matter of taste, and placebo effects is very hard to avoid. It is not easy to admit that an investment/modification has made the opposite of what was expected. But I am a quite experienced listner and I am very hardened when it comes to experiments and testing and all the things that might affect the results since I am working with testing and evaluation proffesionally. Disappoining results is not something strange for me :-)

Both speakers are now converted but the second one still need some time to be run in before I give my final verdict on this. I am not at all afraid to admit that it was a failure if it turns out to be that way. So give me a couple of days to evalute this properly.

Interesting indeed.
The change from four 4ohm drivers to four 8ohm drivers will certainly change something soundwise, no
matter what way they are coupled it will be very different from the original setup.
Furthermore, the use of "full range" drivers rather than dedicated midranges will also do something.
Hard to believe it will provide a better sound reproduction altogether but when it comes to
speakers one can often be surprised. Do let us know the results.

Martin

Hi Turbo,

It's indeed very difficult to find matching drivers for B&O speakers. Especially if the original ones are no longer available (I don't know if the midranges drivers are still available by B&O but I think they prob are.)

I suggest , in order to get as good a sound as possible, to consider refoaming the original ones. I have refoamed many,many speakers now and the results are very satisfactory. If you can do it yourself (not that difficult, but a bit of a learning curve needed) it's a cheap solution that often gives very very good results and probably closest to original specs. The foam rings are available and cheap and the biggest factor is your time of cleanup and reglueing. 

Anyways, I look forward reading your update in a couple of days. 🙂

Dillen wrote:

The change from four 4ohm drivers to four 8ohm drivers will certainly change something soundwise, no
matter what way they are coupled it will be very different from the original setup.
Furthermore, the use of "full range" drivers rather than dedicated midranges will also do something.
Hard to believe it will provide a better sound reproduction altogether but when it comes to
speakers one can often be surprised. Do let us know the results.

Martin

Martin, I agree with you totally here, if we are just looking att the electrical perspective of this conversion, the difference in impedance will not only affect the frequency of the filters and the obvious difference in load on the amplifier. The lower impedance will make a higher power output from the amplifier, as long as it is capable of the lower load. That is not a problem here really because of the total load of the amplifier will not be that big. And the power on these frequencies is not that big.

But the load on the amplifier also makes a difference in it self, by that I mean that the amplifier sounds different depending on the load it is being presented to in means of impedance, resistance and capacitance. By that I mean that even if the elements vere identical in every perspective expect one single paramater of the mentioned it would still sound different because of the amplifier would behave differantly.

As seen in the data sheet on these elements they are called "full range" but that is not really true, I have been reading a lot about these elements and they do not preform well on the lower and higher frequencies that they are supposed to work with. There is one special thing that is apparently not so good about them, around 10 000Hz they obviously sound really bad. That is not a problem in this application since the filters starts to cut them of at 7000Hz.

The positive thing here is that the element is not forced to work in its lowest or highest frequency range and that makes it a pretty "easy" work to deliver music without unusual distortion.

double post

cooldude wrote:

Hi Turbo,

It's indeed very difficult to find matching drivers for B&O speakers. Especially if the original ones are no longer available (I don't know if the midranges drivers are still available by B&O but I think they prob are.)

I suggest , in order to get as good a sound as possible, to consider refoaming the original ones. I have refoamed many,many speakers now and the results are very satisfactory. If you can do it yourself (not that difficult, but a bit of a learning curve needed) it's a cheap solution that often gives very very good results and probably closest to original specs. The foam rings are available and cheap and the biggest factor is your time of cleanup and reglueing. 

Anyways, I look forward reading your update in a couple of days. 🙂

I never really tried to find original replacements. Refoaming is one way to go, and I am for sure capable of doing it myself, but from the prices I have found on Ebay etc, it would be quite expensive.

I am not going that way because I am sure that the mid ranges on the Penats never were especially great from the beginning! No use on fixing something that could be replaced for something better. The original specs is not what I want, there are improvements to be done to this old construction. And to be honest even B&O cut corners in quality in components. Nothing proves that better than all the modification tips you can find here. Besides the agening of components that happends to all old electronics.

I could be wrong on choosing theese elements, but then i will let you now so no one else do the same misstake.

Hi Jens

I think a few of us will be very interested in your results, and as you say, you can never tell with speakers, all strange things are possible 🙂