Vintage Bang and Olufsen Recycle build

[thehillboys]

Objective:
Well I am itching for a build and have these lying around and want to do something with them. The surrounds on the drivers are shot, and the crossover parts are 40 years old. I am thinking of reusing the cabinets and building a 3-way or something that will go down fairly low. I will reuse the stands and keep the vintage look of Bang and Olufsen with new drivers and parts. My thoughts are that there are experts in this thread that can help guide me in some directions.

My Skills:
I have build two surround systems 10 speakers in total from kit speakers from Zaph and Madisound. I have yet to design a crossover, but am familiar with the process and components. I am aware of free software but have not used any. I do not have testing equipment, but it on my list of needs. My woodworking skills are decent. I have build furniture, chicken coops, speaker cabinets, etc and have the tools. I am good with soldering and have designed reef tank lighting and such. I sew and have made my own backpacking gear and make fly rods. I like DIY and like a challenge.

Specs:

-Cabinet size is external 33"h x 14"w x 11"d

-Downward firing port- Have not measured it yet but will when I take the baffle off. I can reuse this port, but it is not necessary.

-The speakers sit slightly at a back angle on the stands and I would like to keep them. Will Measure this angle.

-The current baffles are curved. I will probably redesign the baffle, but could reuse. The Mid driver and tweeter probably sit vertical when on the stands.

-Can scrap everything but the cabinets and stands.

-I do not know if there are any dividers in the cabinet.


Initial Thoughts:

I was thinking of a 3 way design. Something similar to the Travelers or Finalist. I am open to driver suggestions. For an 8 inch I will probably go with the ever popular Dayton used in these two designs. If I use the existing baffle, the bottom driver is 8" and the middle driver is around 7". Thinking trying to design a system to the baffle will be more complex than just making my own baffle. The back angle of the stand will call for crossover adjustments if the baffle is flat.

I am open for any kind of suggestions. I do want to recycle and up cycle the cabinets.

[bbe22]

? original on the right

[thehillboys]

That is cool. Did you refurbish them?

I am open for suggestions on what to do with them. My end goal is to educate myself, to stay under $1000, and get the best sound possible.

[thehillboys]

Thoughts on this option

Use existing Baffle

Dayton Reference 8" Bottom

Dayton Reference 7" or Seas Prestige 7" Middle

SEAS Prestige 27TDFC (H1189) for Tweeter

My concerns:
Space between Mid and Tweeter- Have not measured it yet- Can crossover adjust for wider spacing?
Curvature of the baffle- Mid and tweeter should be Vertical - Woofer will be angled up.

Give me your thoughts

[thehillboys]

Well, I took the baffle off today and dismantled the speakers. Found a few things:

The bottom woofer is 10" not 8"
The Middle woofer is 8" not 7"
The tweeter looks like a 1 1/4" and the other midrange is about 3 1/3".

The bottom two speakers will fit right in on a rubber flang and screw right in with brackets.

I will need to make a baffle to fit in the tweeter hole. I could probably fit a 4" driver and a tweeter. Probably about 8 inches of space here.

A bit Baffled on what to do. As simple as the 10" and the 8" would be to retrofit, makes me want to try and use the baffle.

The cabinet seems sturdy. Would probably put some braces in, if not separate the 10" from the top end.

Would love your thoughts.

[thehillboys]

Midrange is a 4" and I would have 9" total to work with for the top end.

[thehillboys]

....

[chrisn]

Neat project! That baffle is too interesting to not reuse it

Are the tweeter and mid on a removable panel? What is the tweeters flange diameter?

https://www.parts-express.com/morel-tm4055-8-2-midrange-and-1-1-8-tweeter-speaker-plate--287-038



https://www.parts-express.com/hivi-dmb-a-2-fabric-dome-midrange--297-716




Just thinking out loud, but you could use an 8" woofer and fill the 10" hole with a passive radiator. Have you looked into having the original woofers re-foamed?

[thehillboys]

The mid and tweeter are in a sealed capsule that attaches to the top baffle. Can't figure out how to add pics, when I do I will send it.

The woofers, though heavy and sturdy have pretty cheap and dilapidated paper surrounds. Thinking the 40 year old capacitors and crossover is too complex to rebuild. Also do not remember them sounding stunning. Thinking I can put together something that sounds better and more up to date. I know the vintage folks are cringing right now. But looking to transform them. Been out of use for 10 years.

Still learning about passive radiators. Interesting idea.

[thehillboys]

I did see that Morel the other day. I am not necessarily thinking of filling the existing holes. I might just replace the 9 inch baffle with something I can cut a tweeter hole in. Or a small midrange and tweeter in.

[thehillboys]

Doing research I came across the Mini Statements. Similar cabinet volumes with down firing ports. Three way crossover. Dealing with the mid woofer will be a bit of a challenge, but the drivers should fit. It did bring up a few questions If I go with the design and make the necessary alterations.

My questions:

Can you use a 8" and 10" driver on the same low pass in the crossover of a three way or do they need to be the same driver. Use the Dayton Reference 10" and 8" instead of two 8".

What would the 14" baffle do with extra few inches? Can the crossover fix any issues?

If both the mid and tweeter are two wide for the top hole, will another tweeter be workable in the design, crossover modifications pending?

[thehillboys]

Pictures of insides

Here are some pictures of the inside.

[thehillboys]

Also looking at the Finalist top end mid and tweeter with Dayton 8" and 10" on the bottom.

[thehillboys]

Starting to measure and make decisions. What I am thinking:

Bottom End

10" Dayton RS on Bottom. A bit of modifications to baffle but will fit. The cheaper series Datons would fit better but?

8" Dayton RS Center Baffle

Still wondering if I need to cross these individually or can I use them both in the same low pass being they are different size. I have a lot to learn about crossovers.

Top End:

Here is where I am a bit lost. I can rebuild the baffle. I think a 4" mid and a Tweeter will fit. Like the Seas tweeter but am open to any suggestions here. Not sure and have not heard much about 4" mid woofers. May could use a 5" and a small form factor tweeter.


I am not sure if I can just use a Tweeter here and crossover lower, relying on the RS 8" for Mids. This could save money and fabrication issues.

[CADman_ks]

After seeing the pictures of the insides of these, it makes me ponder our DIY construction builds.

Now, I realize that mass manufacturers have to build things as easily and cheaply as they can to a certain extent to make money. When you look at their cabinet construction, it's nothing like a DIY'er would build for the same box size. No cross braces at all, AND their cabinet is made out of particle board, not even MDF. MDF feels a lot stiffer than particle board to me. Are the sides of these boxes imparting a lot of resonance?

Their port is a cardboard tube, and at the end of the day, that probably gets the job done. We'd opt for something like PVC, though.

That's kind of an interesting concept on the mid volume too. It appears that the cardboard tube probably sits against that piece of foam on the back side of the cabinet, essentially closing off the tube, and making that a separate chamber for the mid. Again, cheap, quick, and effective enough?

It would be interesting to know just how much "engineering" goes into all of this stuff, and figuring out the "exact" location that they should put the batting, and why they chose the locations they did.

When I do something for myself, whatever that is, it is always too easy to overbuild, and overengineer EVERYTHING. You do end up with nice stuff, and at the end of the day, for me personally, that's the reason that I do things for myself. At least I know what went into it...

[Steve Manning]

Could be fun to use the cabinet design as a template and build some nice new, better cabinets from scratch.

[thehillboys]

Exactly why I contemplated making a new baffle. Also why I will not put thousands into this build. I plan on adding bracing in a few places and will probably trade out the cardboard for PVC when I design a port. I am using the existing down firing hole. The baffle is surprisingly heavy. It is some kind of plastic composite. I may glue some MDF onto the sides to increase rigidity. The main reason I want to keep the cabinets are to upcycle them. They were just lying around collecting dust. The stand system is also really cool. By they time I am done they will be better suited.

I had an epiphany last night that I may go with. The 4 driver thoughts bring in a bunch of extra problems. Also being as like Steve said the cabinets could be scrapped and I could just do a proven build and get better. These will be used in a sewing room, or at a second property, or in the garage, so why throw tons of money at them.

My goals are to make them sound good if not great and for them to look cool in the space. That brings me to this new thought:

Use Dayton RS for the bottom end but go with an 8" and 7". They will fit just inside the rings and I will make a MDF ring that they will mount to . They will sit relatively flush to the decorative ring and fit somewhat snug. Use some cool screws to make them look like they were designed that way. If I use the grills it will not matter. Go with the Seas or alternate tweeter for the top and redesign the baffle. I could retrofit it to the Mid driver hole with some doing and cover the tweeter hole with some kind of bling. This would allow the 7 inch to be the mid in the design up to around 2k.

[thehillboys]

Open for recommendations for tweeters that work well with the RS drivers.

Also what is everyones opinion on the Paper vs Aluminum for the RS drivers?

[1Michael]

My question would be who is going to design the crossover for this? That is the most important part of the speaker...I would recommend finding a design that you like and build it from scratch or find a kit. YMMV

[thehillboys]

I have been there and done that. I have build a surround sound 5.1 system using Audax drivers from Madisound and a 5.1 Zaph system using kits. That is 12 cabinets total with crossovers pre made.
One of my goals here is not only to upcycle the B&O speakers that were sent out to pasture, but learn the process of speaker building. I am a DIYer. I have designed and build backpacking tents and backpacks. Designed and build reef tank LED lighting, build fly rods and tied flies, build golf clubs etc. I have intermediate woodworking skills. Learning crossover design is next on my list. I feel for a $600 give or take investment, I can give it a go. With all the free software and some understanding of cabinet and crossover design, I may get close to having something that sounds ok. I love the challenge.
That being said, I may be biting off more than I can chew. I will buy a mic and testing software. Building others designs and hearing how wonderful they sound, makes me want to give it a go. I am a math teacher and love to learn. Also if I use the tried and true RS Dayton Drivers there is a lot of documentation about what needs to be done.
I am teaching under lock down at the moment and thinking a Frankenspeaker project will be educational and fun.
Wish me luck.

[thehillboys]

Thinking of drivers and crossovers I am looking at the following. The Dayton Drivers will fit just inside the decorative rings. Looked long and hard for a direct replacement, but nothing had the right diameter to plug and play. Here I will make an MDF ring that the drivers screw to increasing the rigidity of the baffle. The tweeter will fit in the bottom hole of the top baffle bringing it closer to the mid driver. I will just fill the top hole. If this looks goofy or does not work well, I will make a top baffle for the top hole.

8" Dayton RS225-8 8 Ohm

Crossed around 350 Hz

7" Dayton RS 180-8 8 Ohm

Crossed around 2000 Hz

Seas 27TDFC or Dayton RST28F-4. (Used in Zaphs SR-71 and Finalist respectively and crossed around 2000Hz) Would love opinions and alternatives that will cross fairly low.

[thehillboys]

I will probably order the drivers, work the cabinets up and then make measurements of the drivers in the box. Go from there with the crossover design and parts. So the answer to who is designing the crossover from Michael is yours truly. With hopefully help here and other forums from the experts.

I realize that it would be easier to start from scratch, but these cabinets have been in the family for 40 years and I hate to sell or trash them when they might at least make some cool garage speakers.

[chrisn]

Thinking of drivers and crossovers I am looking at the following. The Dayton Drivers will fit just inside the decorative rings. Looked long and hard for a direct replacement, but nothing had the right diameter to plug and play. Here I will make an MDF ring that the drivers screw to increasing the rigidity of the baffle. The tweeter will fit in the bottom hole of the top baffle bringing it closer to the mid driver. I will just fill the top hole. If this looks goofy or does not work well, I will make a top baffle for the top hole.

8" Dayton RS225-8 8 Ohm

Crossed around 350 Hz

7" Dayton RS 180-8 8 Ohm

Crossed around 2000 Hz

Seas 27TDFC or Dayton RST28F-4. (Used in Zaphs SR-71 and Finalist respectively and crossed around 2000Hz) Would love opinions and alternatives that will cross fairly low.

I haven't seen tests on the new(er) RS28's yet so I can't comment on how low they will cross. The Seas 27TDFC will cross low enough for the RS180. Are you using the RS180 as a mid driver in a 3 way, or as the upper woofer in a 2.5 way? The rs180 and rs225 probably want a different cabinet volume and tuning so it may be easier to separate them.

I generally prefer metal cones over paper, and have enjoyed all the Dayton RS drivers I've used.

[Steve Manning]

FYI the 27TDFC and a pair of RS180's were used in the Modula MTM1 design. Could take a look there for some info.

[thehillboys]

Quite the crossover in those. Hope I do not have to tame them that much.

[5th element]

Both of those speakers are the originals in the pictures above. One is the MS150 and one is the MS150.2 hence the slightly different look.

If the only thing wrong with the speakers is the shot surrounds why not replace them?

https://lautsprecher-technik.com/Speaker-Repair-Parts/Speaker-Refoaming-New-Edge-Foam-Surrounds-Repair/Bang---Olufsen-Speaker-Surround-Refoam-Edge-Repair-Kits/Bang---Olufsen-Beovox-MS150-Speaker-Surround-Re-Foam-Repair-Kit---Midrange.html?language=en

https://lautsprecher-technik.com/Speaker-Repair-Parts/Speaker-Refoaming-New-Edge-Foam-Surrounds-Repair/Bang---Olufsen-Speaker-Surround-Refoam-Edge-Repair-Kits/Bang---Olufsen-Beovox-MS-150-Speaker-Surround-Re-Foam-Repair-Kit.html

Just check that the crossovers are still functioning well and enjoy them as they are.

Edit - it seems like there is a lot of information on these if you do a bit of searching.

https://forum.beoworld.org/forums/t/638.aspx?PageIndex=7

A chap here recaps the electrolytics in the crossover and leaves it at that. A sensible option in my opinion. Along with surround replacements you'd have your speakers up and running fairly quickly.

[thehillboys]

Yep thought about just a refurbish. Kind of like the Frankenspeaker idea better. Kind of like my 1996 Nissan Pathfinder. Went from a regular suv old and ready for the junk yard to something much better. Guess it is in my blood to upcycle old things. May sound better or worse, but it will be fun to learn. Also the paper cones are a bit beat up on these also. It is what I do.

[thehillboys]

I do need to brace and strengthen the cabinets also. New drivers, new crossover parts, stronger cabinets, and a new look. We will see what turns out.

[thehillboys]

Would the crossover on the Dayton RST28F-4 be simpler than the Seas 27TDFC? I know it is a bit cheaper and gets good reviews. Love for opinions of those who have worked with both.

[thehillboys]

Worked up a crossover on Xsim. I will post in a few days for you all to critique it and help me with my ignorance. Working on the cabinets. Well in need of bracing and reinforcement. I did the crossover with the RST28F-4. Off to the hardware for stain, paint and MDF in a few days.

[thehillboys]

Hoping to get a response. My question is should the midrange and tweeter or just the midrange be separated from the woofer? Here I am going to use the RS Dayton drivers 8" and 7" in the same box. I have been studying some designs that put the mid in its own tube. Also wondering if you run the 8" and 7" together in the low pass. Their frequency responses are very similar. I know they probably have different power and sensitivity specs. Run them as if they were the same driver. Have not seen it done but is it possible.

Options would be:
All in the same box
separate the mid and tweeter in a sealed enclosure
Put the mid in its own tube

[1Michael]

Separate the mid and tweeter in a sealed enclosure.

[chrisn]

if they cover different frequency ranges they need to be separated. If the tweeter is sealed back then it doesn't "need" a separate space, but sometimes people seal the back of the baffle behind it with another piece of MDF/etc.

[Mikerodrig27]

They will model different then they will sound. I would grab some cheap caps, resistors and inductors of different values. It takes forever waiting for things to show up. Do you have a calibrated microphone already?

It is a big learning curve but it should be fun!

[thehillboys]

I did design a crossover for a starting point in XSim. I will start from there. I have not bought a microphone yet. My thoughts are to even build the crossover in its own space for not so I can tweak it. With the room, not perfect cabinet, and my novice skills, I know it will need tweaking. Anxious to see how close it will be the first go around. I had a lot of similar designs to model after. I am going to line the box with 3/4 inch mdf sides and top. I will put a couple of cross braces, one to divide the compartments and one for support. The crossover board will go on the bottom in the woofer compartment eventually. I do not think the cabinet other than the wider baffle will be an issue as far as being dead. I think I have developed a way to attach the drivers to MDF attached to the baffle for strength. I will use some left over foam and stuffing to dampen the cabinets. I have painted the stands flat black and sanded the cabinets down to take a stain. I will stain them a darker cherry or mocha coffee type stain. Making them darker. I am looking for a color for the baffles. My neighbor has a 4 runner that is grey and black that is inspiring me. They should look pretty cool when done. Who knows how they will sound. Fun project just the less. A good garage set at least.

[Mikerodrig27]

lining the whole thing with MDF may be overkill. I'd start with the bracing and go from there. Definitely put dampening material on the inside though.

I am all up for messing with things so it will be interesting to see how this comes out. The UMM-6 is on sale at Parts Express right now. over 100 is free shipping too.

[thehillboys]

Did some cabinet work this weekend. back, top/bottom, right/left will be 1 1/2" thick with mdf inside and the plywood with Venere outside. I will have two braces between speakers. I cut rings for the 8" and 7" RS drivers that they will attach and be locked into the baffle. I may find a way to deaden the baffle a bit. I will start glueing up tomorrow. Still waiting on the tweeters, they were back ordered. I will get some pictures up when I get the insides glued. I have been getting little interest on the forum, so I may move the thread elsewhere. Seems as though my speaker hack job may be more suited for another forum. May need some hillbillies to see my vision. If I move it I will come back and post the finished project with hopefully some measurements and a subjective unprofessional review.

[thehillboys]

Took a detour from the main project today and working on a side project. I took the tweeters from the original speakers and paired them with a Dayton RS 4" full range speaker. Crossed them over and am putting them in the existing box that the tweeter and mid came in. Built the crossovers and tested with the drivers. Now need to build the baffle. It so far will be a small sealed TM but may later port it or just try it as an open baffle. Thought it would be fun to mess with. I will get some pics up when I get further along.

[thehillboys]

Here is the crossover for the mini project. Test sounds good, will build the baffle soon.

[thehillboys]

Even recycled the hookup wires by braiding three of the internal hook up wires. Cool fun little project. May recap my old NAD to run these little guys.

[thehillboys]

Hated to let the tweeters go to waste. They seem in really good shape. I had no measurements so I cross them over around 3k modeled it around a Dayton Silk Dome. May have to tweak the resistors if it plays too high or too low. Trail and Error.

[chrisn]

Looks good. Cabinet pics?

[thehillboys]

Finished mini speakers with original tweeters.

[thehillboys]

I kept the enclosure that the mid and tweeter came in and attached it to a walnut baffle made from a piece of scrap Walnut I had lying around. They sound good. Sealed enclosure so they might need a sub eventually. Running them with a Topping Mx3 at the moment. Designing a stand to keep the back up. Right now I am using the driver box to prop them up. I do not have measurements, but a bit of bass boost from the MX3 helps the low end. Probably could have used a bit of a baffle step for the 4 inch, but the bass adjustment on the MX3 does the trick. When I can afford a test mic, I will take readings and see if it is worth it to boost the bass. A sub will also cure the issue. Can't hear anything strange in the mix without testing them.

[chrisn]

Could always vent the RS100. Good driver to experiment with