General Forum

Re: Questions about MS150 speakers and B&O's measurement techniques...

j0hnbarker — Fri, 27 Mar 2009 06:12:00 GMT

Hi Jon

Like Peter, I recently fitted a pair of replacement 8" new Peerless woofers in some MC120.2s. I don't have any equipment to measure the results, but all I can say is that I am very pleased with them. Both my old woofers needed re-foaming, and one of the voice coils was dead, so to me the new units were a simpler (if more expensive) and quicker route to getting my speakers back up and running again.

Re: Questions about MS150 speakers and B&O's measurement techniques...

Jon — Fri, 27 Mar 2009 04:11:36 GMT

I guess not. :)

Re: Questions about MS150 speakers and B&O's measurement techniques...

Jon — Wed, 25 Mar 2009 20:59:16 GMT

Hey thanks Andy! This place seems like a great place to learn. I've already found out how to adjust the tonearm set-down position on my turntable.

Anyway, I don't know how feasible it is to reverse engineer this speaker, but I'd like to try. If I had measurement equipment, that'd probably make it easier, but I don't. Hopefully, someone can answer my questions.

Thanks again!

Jon

Re: Questions about MS150 speakers and B&O's measurement techniques...

Jandyt — Wed, 25 Mar 2009 19:41:45 GMT

Hi Jon, and a warm welcome to Beoworld.
There are not many members online at the mo, and this is a bit technical for me, but check in tomorrow and I'm sure you will have some replies.
One of our mods, and a prolific poster, Peter has replaced some bass drivers with Peerless ones in a pair of 120s and has some data I believe.
I believe the 150s are superbly flat. (and very big!)

Andy T.

Questions about MS150 speakers and B&O's measurement techniques...

Jon — Wed, 25 Mar 2009 19:23:52 GMT

Hello everyone, this is my first post here. I recently purchased an older Beosystem 8000, and unfortunately, the shipping company damaged the bass drivers in the MS150 speakers.

I was able to locate another pair of mid-bass drivers, and then I bought a new set of Peerless SLS 10" subwoofer drivers to replace the old Peerless units. Since I have no measurement equipment, I took an educated (well, hopefully anyway...) guess about the interchangeability of these drivers. I chose the Peerless, because, one, the old unit was Peerless and I wanted to keep it Danish, and two, because it seemed to measure correspondingly in Unibox, a speaker enclosure design program. B&O specs this speaker at +/-4dB from 48-22KHz, and -8dB at 30Hz. With the size of the port used, in a 64 liter enclosure lined with stuffing, it looks like they tuned it to around 30Hz. The new Peerless SLS driver models almost identically.

This brings me to my first question: Is the "+4dB" in this spec just residual undulation in the frequency response? Second question: Does B&O have some method of compensating for the lower frequency transition in response due to the different radiating characteristics at those frequencies (i.e. - "baffle step")? I'm not the best at reading schematics, but from what I can tell in the service manual, there's no compensation cicuit designed into the crossover.

What I'm thinking is that the "+4dB" is referring to response above the frequency of the baffle step transition, and hence, when I put this speaker all back together, it's going to sound super lean, which will be further magnified by my extremely lively room characteristics (polished concrete floor, sparse furnishings, etc.).

I remember my old Beovox S80.2's sounded quite thin. When I put them in a corner, it helped the tonal balance tremendously, but created more problems than it fixed. I'd like to not have to have the MS150's stuck in the corner.

Any help is appreciated! Thank you!

Jon