$vboptions[bbtitle]   $vboptions[bbtitle]  
  Terms and Conditions     Project Showcase
  Resource Index   Speaker Terms Glossary
  Security/Privacy   Speaker Replacement Help
Page 1 of 16 12311 ... LastLast
Results 1 to 20 of 314
  1. #1
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    This thread is to document a build using the RS28A in a waveguide teamed up with the B&C 8BG51 Neo motor pro-sound mid-woofer.

    Tom Jones (takitaj) provided the baffle. He fashioned a waveguide to fit the opening of the RS28, 2" deep, 7" overall width, with a smooth curve that ends tangential to the baffle. I'm unsure yet as to how well it will work but I have high hopes. It follows fairly closely the profile of the larger guide made by DanP with a 3D printer a couple years back. That guide was wider, with a larger radius profile. This one features the same throat opening, and same depth. Exit angle is a bit smaller at about 90 degrees.

    Tom's baffle is made to replace the baffle on the .75 cf TM Parts Express cabinet, using the same mounting screws, so it will be removable to allow mounting the tweeter onto the rear of the baffle.

    I expect the baffle to be here tomorrow so hopefully I can get things mounted and start testing. I want to bring this to the KYDIY this weekend, so I probably won't have time to get any paint on the baffle. Hopefully, I'll have enough time to get a crossover built along with getting some voicing time in.

    This will be an 8 Ohm system, and I'm guessing at around 87dB overall sensitivity after baffle step, with F3 about 47Hz, and should be able to produce over 110dB from 50Hz on up. Not too shabby for a stand mount monitor. I'm going to try a 2.5" port which will have 38m/s port velocity with 100W input. It's a compromise for sure, but the smaller port pushes the port resonance up above 1KHz. And for normal listening levels, port velocity will be low enough to not cause problems.

    More to come as progress continues.

    Click image for larger version. 

Name:	baffle.jpg 
Views:	1242 
Size:	230.3 KB 
ID:	41806
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	woofer bass alignment.gif 
Views:	314 
Size:	43.4 KB 
ID:	41808  
    Last edited by Pete Schumacher «; 12-14-2013 at 03:51 AM. Reason: corrected exit angle

  2. #2
    Join Date
    Jan 2013
    Location
    Hampton Roads Virginia
    Posts
    1,224

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

    Looks like a very cool project Pete. Can't wait to see how it turns out.

    Quote Originally Posted by Pete Schumacher « View Post
    This thread is to document a build using the RS28A in a waveguide teamed up with the B&C 8BG51 Neo motor pro-sound mid-woofer.

    Tom Jones (takitaj) provided the baffle. He fashioned a waveguide to fit the opening of the RS28, 2" deep, 7" overall width, with a smooth curve that ends tangential to the baffle. I'm unsure yet as to how well it will work but I have high hopes. It follows fairly closely the profile of the larger guide made by DanP with a 3D printer a couple years back. That guide was wider, with a larger radius profile. This one features the same throat opening, exit angle (120 degrees) and same depth.

    Tom's baffle is made to replace the baffle on the .75 cf TM Parts Express cabinet, using the same mounting screws, so it will be removable to allow mounting the tweeter onto the rear of the baffle.

    I expect the baffle to be here tomorrow so hopefully I can get things mounted and start testing. I want to bring this to the KYDIY this weekend, so I probably won't have time to get any paint on the baffle. Hopefully, I'll have enough time to get a crossover built along with getting some voicing time in.

    This will be an 8 Ohm system, and I'm guessing at around 87dB overall sensitivity after baffle step, with F3 about 47Hz, and should be able to produce over 110dB from 50Hz on up. Not too shabby for a stand mount monitor. I'm going to try a 2.5" port which will have 38m/s port velocity with 100W input. It's a compromise for sure, but the smaller port pushes the port resonance up above 1KHz. And for normal listening levels, port velocity will be low enough to not cause problems.

    More to come as progress continues.

    Click image for larger version. 

Name:	baffle.jpg 
Views:	1242 
Size:	230.3 KB 
ID:	41806

  3. #3
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    Ran a sweep of the 8BG51 nearfield, mic about 3" from the dust cap, just outside the front of the woofer flange. I'm guessing about 1W input. Ungated, no smoothing. This looks close to the manufacturer's data. Clean performance up to 1K. I hope the RS28A/guide can meet up with this without too much trouble.

    Click image for larger version. 

Name:	8BG51 nearfield 1W no baffle nearfield.png 
Views:	1069 
Size:	25.1 KB 
ID:	41811

  4. #4

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

    So what's the major "diameter" on that woofer?
    Thanks,
    Aaron

  5. #5
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    Quote Originally Posted by aarond View Post
    So what's the major "diameter" on that woofer?
    From the PE product page:

    Overall Outside Diameter 8.8"
    Baffle Cutout Diameter 7.4"
    Depth 3.50"
    Bolt Circle Diameter 8.3"

  6. #6

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

    Ha, I looked there but didn't scroll down to see it. I'm still not used to the (not so) new site format. I didn't see an "A" dimension in the description and assumed they left it out because of the odd shape.

    So practically speaking it's the same OD as the RS225, which is what I was really wanting to know.

    Following along, enjoying the ride.
    Thanks,
    Aaron

  7. #7
    Join Date
    Aug 2008
    Location
    council bluffs iowa
    Posts
    7,221

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

    cool Pete. Eager to see how the WG works out.
    " And it's not just the end result -- nice speakers or a cool amp -- but the creative process that adds richness to my life; and an artistic outlet. A cool looking speaker qualifies as art in my book."
    Tom Zarbo, January 2014

    http://www.midwestaudioclub.com/spot...owell-simpson/

    http://s413.photobucket.com/albums/pp216/arlis/

  8. #8
    Join Date
    Nov 2007
    Location
    Lil' Rhody
    Posts
    3,819

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

    Pete, looks really interesting. I have been eyeballing that 8" BC for a while.

  9. #9
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    Well, getting this to KYDIY is going to be tough. The baffles need to be modified on the back side in order to fit into the cabinets. It'll take some creative router or table saw work but the mod shouldn't be more than time consuming.

    In the meanwhile, I got the RS28A mounted and ran a sweep. I'm liking the looks of this guide. Should be a perfect match for the cutoff knee of the woofer.



    Click image for larger version. 

Name:	RS28A in guide.png 
Views:	2113 
Size:	24.9 KB 
ID:	41874

  10. #10
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    Well I couldn't get the baffle all the way onto the enclosure, but it did fit well enough to get a measurement of both woofer and tweeter together without the dipole cancellation on the woofer. I really wanted to start on a crossover design.

    So far,so good. 8 components yields this system response. LR4 at 1200Hz.



    Click image for larger version. 

Name:	System response.jpg 
Views:	2134 
Size:	59.1 KB 
ID:	41875

  11. #11
    Join Date
    Jan 2006
    Location
    Sweden
    Posts
    467

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

    Pete, is this wg the same as the LOKI or is it slightly smaller? Speaking about the LOKI, is that design dead? I hope not!
    Darwin loves you!

  12. #12
    Join Date
    Jan 2013
    Location
    Hampton Roads Virginia
    Posts
    1,224

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

    That should be an excellent HT speaker for folks that want high output levels from a standmount form factor. I'm sure it will ne nice for music too, but reasonable sensitivity and extension in a standmount box with pretty high output levels is a nice combination.

    Quote Originally Posted by Pete Schumacher « View Post
    Well I couldn't get the baffle all the way onto the enclosure, but it did fit well enough to get a measurement of both woofer and tweeter together without the dipole cancellation on the woofer. I really wanted to start on a crossover design.

    So far,so good. 8 components yields this system response. LR4 at 1200Hz.



    Click image for larger version. 

Name:	System response.jpg 
Views:	2134 
Size:	59.1 KB 
ID:	41875

  13. #13
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    Quote Originally Posted by jonasz View Post
    Pete, is this wg the same as the LOKI or is it slightly smaller? Speaking about the LOKI, is that design dead? I hope not!
    L.O.K.I. will resume when the new reference drivers come out. The 8" composite cone should be around in February (or there about) according to Rory.

    This particular guide is slightly smaller than the original and from the looks of it, doesn't extend quite as deep before cut off. Otherwise, it still produces the same smooth transfer function.

  14. #14
    Join Date
    Aug 2011
    Location
    Euclid, OH
    Posts
    1,061

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

    Quote Originally Posted by Pete Schumacher « View Post
    In the meanwhile, I got the RS28A mounted and ran a sweep. I'm liking the looks of this guide. Should be a perfect match for the cutoff knee of the woofer.
    Distortion looks excellent all the way down to 1 khz, and that is impressive. Most of the response slope is nice and smooth, great work. I'm not sure I like that massive early roll-off though. I wonder how audible that will be in the end.

  15. #15
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    Quote Originally Posted by JasonP View Post
    Distortion looks excellent all the way down to 1 khz, and that is impressive. Most of the response slope is nice and smooth, great work. I'm not sure I like that massive early roll-off though. I wonder how audible that will be in the end.

    Good point. I'm not sure how much of it is really there. These were all far less than optimal measurement conditions. Once I get the baffle into the cabinet properly, I'll get a new set of data.

    But it looks like this will not make it to KYDIY. Just not enough time. And now, my traveling partner has come down with a bad chest cold, so I'll likely be staying home to baby sit her.

  16. #16
    Join Date
    Aug 2007
    Location
    Grenada, West Indies
    Posts
    1,371

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

    Hmm... that 2dB rise @ 4kHz might stand out a bit on certain passages...

  17. #17
    Join Date
    Mar 2011
    Location
    Chicago - the guts
    Posts
    4,488

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

    Pete I have a dumb question regarding your PCD screen shot. Why is there such a large SPL disparity between the individual raw driver responses and overall system response? What happened to the sensitivity? FWIW, this is why I am attending Jeff's PCD speaker design seminar...LOL. So what's going on there?

  18. #18
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    Quote Originally Posted by Brian Steele View Post
    Hmm... that 2dB rise @ 4kHz might stand out a bit on certain passages...
    Could be. The RS28A has a bit of a rise at that frequency which is built into the tweeter. Only harmonics should be emphasized, and only a little bit at that. The top octave roll off seems to be another feature of the RS28A which according to manufacturers measurements as well as third party, definitely drops off quite a bit above 14KHz. That's a "feature" of 28mm hard domes that stay pistonic over their operating range.

    I'll post a series of off axis plots once the baffle is mounted to the cabinet. When you start getting off axis, the high end response actually improves.

  19. #19
    Join Date
    Oct 2005
    Location
    Ballwin, MO 38.597554, -90.547423
    Posts
    17,936
    Blog Entries
    1

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

    Quote Originally Posted by bkeane1259 View Post
    Pete I have a dumb question regarding your PCD screen shot. Why is there such a large SPL disparity between the individual raw driver responses and overall system response? What happened to the sensitivity? FWIW, this is why I am attending Jeff's PCD speaker design seminar...LOL. So what's going on there?
    Holm impulse only displays data relative to 0dB (full range). So when exporting FRDs for use in PCD, I first add 99dB and then export. That way, they show up in Jeff's default display range.

    These PCD plots are not relative to 1W, thats for sure. The raw response plots were taken with at least 1W to the drivers.

  20. #20
    Join Date
    Mar 2011
    Location
    Chicago - the guts
    Posts
    4,488

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

    Quote Originally Posted by Pete Schumacher « View Post
    Holm impulse only displays data relative to 0dB (full range). So when exporting FRDs for use in PCD, I first add 99dB and then export. That way, they show up in Jeff's default display range.

    These PCD plots are not relative to 1W, thats for sure. The raw response plots were taken with at least 1W to the drivers.
    OK, I can understand the part about Holm and the response not being SPL accurate, but I guess I was wondering more about the 15db drop in sensitivity at 1.5k. At the end of the day, the raw response IS relative to the final system response, yes? So you're still expecting the final iteration of this to be about 87db? Really showing my noobishness right now…..

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  




Your #1 Source for Audio, Video & Speaker Building Components


Clearance Center
Deal of the Day
New Products




View Our latest
Sales Flyer

Prices Effective
Through 8/31/14


Order our FREE 336 Page Full Color Catalog


Speaker Component Categories

Home Audio Speakers

Professional Audio & Guitar Speakers

Car Audio Speakers

Speaker Buyouts

Measurement & Design Tools

Subwoofer Plate Amplifiers

Full-Range Plate Amplifiers

Crossover Components

Cabinet Hardware & Speaker
Grill Cloth

Speaker Cabinets

Subwoofer System Kits

Speaker Kits

Speaker Repair Parts

Speaker Wire