Home/Pro 8" 2-way: RS28A and B&C 8BG51

[Pete Schumacher]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

Good point, the the natural low end response on the RS28 in indeed lower than the TBFC.

Me personally I would go with the elliptical waveguide, they measure very similar but with the elliptical the woofer could be mounted closer and I like the looks of the elliptical better... :p
I would like to pair them with the FaitalPRO 6FE100 woofers tho because I'm not changing my current B&C/JBL current system but I really want to build this for another smaller room that will see much less use so it wouldn't be worth the investment for the B&C woofers.

Any ideas on how much a set of baffles would cost with the ellipticals?

How big would the baffles be? Same as these? I'd have to redraw the cut files for your particular woofer. PM me for a quote.

By baffles are you talking about the WG/baffle combo? Are you still using the 10"x17" PE dimensioned baffle for this?

Yes, they fit the PE .75cf TM cabinet using the hardware provided with the cabinet kit. They do need to have a rabbet cut around the back edge in order for the hardware to grab the inserts though. I forgot about that step. Easy fix on the table saw or router table.

I'm thinking that this particular baffle with the 8BG51 form factor for the woofer would be about $55 for either WG profile. Does that seem reasonable? You'd be responsible for final sanding and the back rabbet. It only took me 10 minutes with 80 grit to eliminate the tool marks. Can't imagine putting the rabbet on the back will take any longer than that.

[Pete Schumacher]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

Erich over at DIY Sound Group sent me a very interesting new item he just got in.



With the RS28A mounted to the guide (flange and all), and with it just sitting on top of a speaker, here's what I got on-axis at 1m.



This little guide looks really good with the RS28A! The only modification I made to the guide was to slide the back side of the guide back and forth on some 80 grit sandpaper for a couple of minutes to make sure the surface was smooth enough to get an air tight fit on the flange.

More on this to come as well. He sent me a little knockdown enclosure that puts the 8BG51 and this pairing together. I'll get the two drivers mounted up and come up with a first attempt XO. Can't do any voicing yet since he only sent me the one cabinet, but he's got a tower underway too!

[Pete Schumacher]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

Here's a set of plots of the TBFC in Erich's SEOS8 guide. It certainly responds differently to the guide than the RS28.

[Hifiaudio]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

So we have a new SEOS-8 based kit coming up at DIYSG soon ( using RS28A and 8BG51 ) ?

[donc]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

I would like to see this new kit with a woofer that uses a round frame and rubber surround like the Beyma or 18 Sound ! Is there a benefit using the B&C over these other two other than cost ? Any comparisons ?
donc

[Erich H]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

The B&C does have a rubber surround.

[Pete Schumacher]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

The B&C is the only "pro" 8" woofer I've seen that will provide the bass performance I'm after. All the others cut off around 60Hz or higher. The 8BG51 reaches well into the 40s. If you can find one that models up well, gives us at least 50Hz F3, I'd be happy to use it. Just remember that the sensitivity after baffle step needs to be around 91dB.

I did just find a possible Beyma candidate . . . http://www.usspeaker.com/beyma%208BR40-1.htm

It's a smallish 8" at only 200mm diameter, but it does look like it could easily work.





And then there's a 10" that looks promising too! http://www.usspeaker.com/beyma%2010BR60-1.htm

[donc]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

Beyma # 8P300Fe and the 18Sound # 8BM500 are the two that I would like to see in a two way , especially with a dome not a CD .
donc

[Pete Schumacher]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

Beyma # 8P300Fe and the 18Sound # 8BM500 are the two that I would like to see in a two way , especially with a dome not a CD .
donc

Neither of them off any bass below about 70Hz or so. But if you'd like to see them in a kit I'm sure we could work one up.

The 8MB500 in .75cf tuned to 75Hz has an F3 at 70Hz.

The 8P300Fe also has a similar F3 in .5 cubic feet.

They're both at about the sensitivity limit to mate up with the RS28 in the guide.

[blue934]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

Wow, Pete I love the look of that round guide baffle! Great symmetry.

David

[jcake5]

Re: Home/Pro 8" 2-way: RS28A and B&C 8BG51

Hi Pete,

I for one, am very thankful for all of the information that you have provided over the years. Please keep it up and help us rookies learn. I troll the boards and basically never add since I believe that I have not reached a level of audio knowledge that will allow me to contribute. I have made my own speakers of my own design based in inspiration from you and others. So thank you and keep on Pete!!

Kind regards,
Eric

[Pete Schumacher]

Another update. I revisited the baffle/guide and changed it to a 1" deep, 8" wide circular guide with circular profile to the guide walls. I'm much more pleased with the result of the shallower guide's rendition of the high frequency end of the spectrum. They image like crazy and have all the authority you'd expect from an 8" monitor. In-room, usable bass to the mid 30s.

Someone in California expressed an interest in buying them from me, but if that doesn't happen, I'll bring them to Iowa.

Final response and pics of the monitor.

[jhollander]

Pete if those are the same as I heard they are very good. That B & C was surprisingly detailed.

[Pete Schumacher]

If you remember John, we talked about the tweeter being a little bit "hot" and since then I changed the crossover and brought the tweeter down maybe 1.5dB from where it was. I didn't just pad it but changed all the values so that no padding resistor was required. It actually smoothed the tweeter response even further than before.

And I must agree with your impression of the woofer. It is as detailed as one could want. I'm very impressed with it. I'll make sure it gets to Iowa for everyone to see how good these B&C drivers really are.

[Pete Schumacher]

Here's the final details on the build, crossover and guide specs for anyone who wants to replicate this beast of a bookshelf. Each dimension listed is at a depth of an additional 1/32" except the topmost cut which is 1/64" from baffle flush. The cut below it is at 1/32" and each subsequent cut is an additional 1/32"

And if you don't want to replicate the baffle yourself, just PM me and we can arrange to get a set made for you.