The BaSSlines (was High Sensitivity Design)

[dlneubec]

Unfortunately, there is no progress. I've had to refocus my efforts on applying the veneer and finish to two other projects that I hope to take to the Dayton DIY on July 12, before I start on this new one.

I hope to start on this project in the latter half of July.

[dlneubec]

Any update on this ?

All the best,

Florian

There is nothing to update yet. I'm taking a few needed weeks off from speaker building before I start on this next project. I'm not in a hurry to finish this one.

BTW, I will be calling it the BaSSlines. This comes from the names of the designers of the speaker that inspired this design, Jeff Bagby(Ba) and Jim Salk of Salk Sound (SS).

[FlorianO]

BTW, I will be calling it the BaSSlines. This comes from the names of the designers of the speaker that inspired this design, Jeff Bagby(Ba) and Jim Salk of Salk Sound (SS).

With such godfathers it's bound to be good, looking forward. And congrats for the DIY Dayton award !!

Florian

P.S. OT question: Have I done some moderator no-no warranting _both_ my post and ThomasW reply to be removed from this thread (w/o notice) ? If so, please advise (just trying to understand why in order to avoid that in the future. thnks)

[dlneubec]

I didn't know your post was removed. Thomas moved his post and my follow up to it about my Dayton wins, because he accidentally put it in the wrong thread and so he moved them both to the Dayton thread. Maybe yours got lost in the mix by mistake.

[ThomasW]

OT question: Have I done some moderator no-no warranting _both_ my post and ThomasW reply to be removed from this thread (w/o notice) ? If so, please advise (just trying to understand why in order to avoid that in the future. thnks)

I don't know what happened to it. I split the thread to move Dayton DIY posts to the other thread. Splitting threads this large is very difficult and occasionally some of the bits decide to go their own separate way...So it's removal was unintended.

Since Dan quoted it we know what was originally posted...

[Jed]

Orcadesign.com seems to have decent pricing on the PHL mids, just in case you guys decide to go that route.

I also emailed them about Focal. Apparently focal is back in DIY, I just don't know if there is much new technology or just remakes of the "classics."

[dlneubec]

Thanks for the heads up Jed! That is a very good price on the 1120.

[NEO Dan]

Zalytron has the 1120 listed at $120

[dlneubec]

Well, I'm finally ready to start on this project more seriously. I have made a few changes to the design (see mock-up below). I'm thinking of doing the baffles out of solid hardwood, 1.5" thick. The idea is to laminate them from 1"x2" hardwood stock laid flat and stacked. I will mix a second hardwood as shown stricktly for aesthetics. I like the stacked laminated look and can easily cut the chamfers and in that orientation, I don't think splitting will be an issue. The woofer baffle would be mechanically attached to the box, not be glued to it.

I'm also considering mounting the midrange and tweeter from the back, leaving maybe 1/2" wood between the driver and the baffle face. I would use a 1/2" round-over on the edge. This would certainly make the mounting of the odd shaped midrange driver easier. The tweeter would look like the one in my Duo project, which has a 1/2" deep waveguide. I like the simple clean lines that this kind of mounting offers. Of course, I would have to do some testing to see just what effect this will have on the drivers frequency response before making a decision to do this kind of thing with either of the drivers. If there was a significant detrimental effect, I would abandon the idea.

More will be coming as I get further into it.

[ttan98]

Welcome back, looking forward towards your design....

[TacoD]

Where do you put the x-over? In the bass cabinet?

[dlneubec]

Yes, it will be in the bass cabinet. There will be power in binding posts on the back and two pairs on the top for the midrange and tweeter.

[dlneubec]

Here's a little update:

I'm going to try a different kind of box bracing scheme on the bass bins (see attached pdf). It involves dadoing 1/4" wide x 1/4" deep slots and installing 1/4" wide x 1.5" deep red oak or perhaps baltic birch ribs along the sides, top and part of the front of the box (on each side of the driver). These ribs are oriented by starting with a rib in the center, since that is where the bracing is most needed, and then placing the others in a golden mean ratio from the middle rib and/or the corners. Two 1"x2" hardwood cross braces will be used to tie the sides and front and back together. The ribs will offer additional gluing surface for the cross braces. My hope is that it will be at least, if not more effective than typical window bracing, but perhaps lighter and burn up a little less volume.

After seeing Zaph's test of the three Pro mid drivers, I've decided to go ahead with the B&C 6md38, as planned. Now I just have to get my hands on some. Ther are on backorder at PE.

Also, since two of my goals with this design is to reduce the mass of the speaker in room and, as always, a high WAF, I'm considering using arylic or glass for part of the open baffle section. I have found 1/2"x24"x24" acrylic online for $38.50, 3/4" for $68. One sheet of 24"x24" will do two baffles. I'm thinking of ordering a couple sheets to try. Exactly how it will be designed will depend on how easy the acrylic is to work with. Glass is also a possiblility, which I will explore with local glass shops. Below is a mock up of what it might look like.

[Jed]

Lookin' really sweet Dan. You're an artist!

[ThomasW]

The ribs are an interesting idea, but in the end I think it's more effective to use multiple 'window' or 'ladder' style braces to lock all surfaces of the box together.

[David_D]

Hi Dan
I really like to looks of the clear panel. You may want to consider polycarbonate. (Lexan)
As acrylic is very brittle and prone to chipping, cracking and scratching, Lexan is far more durable and free machining, although that comes with a higher price tag.

[dlneubec]

The ribs are an interesting idea, but in the end I think it's more effective to use multiple 'window' or 'ladder' style braces to lock all surfaces of the box together.

Hi Thomas,

You may very well be correct, but let me explain a bit further how the side are tied together. I left this out in my initial explanation.

There will be two cross braces made from 1"x2" red oak from side to side and front to back and one from the top to one of the cross braces. The sid to side cross braces and front to back cross braces will be resting on one another, so they can be glued or bolted together. Another option is to put a small dado in them so the overlap and mechanically lock them together in the center, using glue to secure them. This will ensure that the cross braces are supported in the center so they cannot flex or vibrate and it ties all 4 sides together.

FWIW, I did a comparison between this and the original window bracing scheme I had, which had 3 horizontal window braces of 3/4" stock with the panes of 1 1/4" wide. It had a brace volume of about 193 in3. The ribbed box has a brace volume of 161 in3. There is about a 0.5 liters brace volume reduction in the ribbed box, or about a 17% less, so not a tremendous savings in volume. If only one cross brace was used between the sides and front and back and top, that would drop the ribbed total to about 131 in3, for a 0.85 liter reduction or about 32% less than the window brace option.

[dlneubec]

Hi Dan
I really like to looks of the clear panel. You may want to consider polycarbonate. (Lexan)
As acrylic is very brittle and prone to chipping, cracking and scratching, Lexan is far more durable and free machining, although that comes with a higher price tag.

You are the second person that has suggested that and I will be looking into the cost and availability of Lexan.

[dlneubec]

Lookin' really sweet Dan. You're an artist!

Thanks Jed! Now if I can get them to sound as good as the Bagby/Salk speaker does, I will be a very happy camper.

[cjd]

I'll third lexan over acrylic, though understand that it is very prone to scratching.

I'd actually recommend tempered glass.

C

[ThomasW]

Hi Thomas,

You may very well be correct, but let me explain a bit further how the side are tied together. I left this out in my initial explanation.

That sounds fine.

Another vote for polycarbonate it's much easier to machine compared to standard acrylic. I agree with Chris regarding glass, problem is it's a bear to machine without special tools.

Psst....don't tell anyone I posted this but US Speakers has the B&C 6MD38 in stock..

[dlneubec]

I will be looking into tempered glass as well at local glass shops. Glass will mot certainly dictate the design options, whereas a plastic might be a little more flexible, but I don't know for sure yet.

For example, with plastic, I could still mount the tweeter in a 1/2" dep waveguide (ala Zaph) by simply cutting a hole and rouding it over with a 1/2" roundover bit. I suspect that you can't get that done with glass. So to have that design option with glass, I'd have to have a larger hole drilled and have the wood "extrude" through the opening and then cut the waveguide into the wood.

I'm also considering installing the midrange 1/2" deep with a 1/2" roundover, so the same situation applies there.

I just took a quick look at polycarbonate and a Lexan sheet 1/2" x 24" x24" is $75.80 at USplastics. A Makrolon polycarbonate sheet, however, of the same size is only $35.88, which is as cheap as I found he Acrylic for. I'm not sure of what differences there are between Lexan and Makrolon, but the both are polycarbonate.

[dlneubec]

Thomas,

Thanks for the heads up on the 6md38 :T . I might have to go for that, however, from my recent doings at the Dayton DIY, I have a $500 credit at PE I'd like to use!

[ThomasW]

I will be looking into tempered glass as well at local glass shops. Glass will mot certainly dictate the design options, whereas a plastic might be a little more flexible, but I don't know for sure yet.

For example, with plastic, I could still mount the tweeter in a 1/2" dep waveguide (ala Zaph) by simply cutting a hole and rouding it over with a 1/2" roundover bit. I suspect that you can't get that done with glass. So to have that design option with glass, I'd have to have a larger hole drilled and have the wood "extrude" through the opening and then cut the waveguide into the wood.

I'm also considering installing the midrange 1/2" deep with a 1/2" roundover, so the same situation applies there.

The pro glass shops can do an amazing range of cutouts and edges. For edge work they charge by the inch/foot. If you're talking about 1/2" or thicker glass, the cost for it and machining will be really really $PENDY....... 8O

For your needs any brand of polycarbonate will be fine.

[---k---]

Dan,

My wife would approve of your design.

I wonder if you simplify the mid and tweeter wood mounting plate to a simple rectangle if you could get a local trophy place to cut the glass for you for a real reasonable price. I'm picturing all those glass trophies I've seen that are nothing more than a triangular piece of 3/8" glass with beveled edges.

[cjd]

Find a good glass shop (one that works in the thicker glass you'll be wanting to use) and you should be able to get a roundover treatment. For that matter, with a little patience you should be able to work it over with a grinding stone yourself. If you work glass dry just watch the eyes!

If you want the roundover polished, just spec it out exactly and get it done. I mean, you could do it yourself too but it takes a wet pumice setup of sequentially finer grits. The equipment isn't prohibitively expensive if you're into glass work...

Another option is to find a local glass shop that'll do a custom casting for you. You could get countersinks and everything. But it won't be tempered, probably.

Make sure you get machinable lexan if you're going to be working it. I'm not exactly sure the differences in make-up (possibly it's only thickness).

C

[cjd]

I'm picturing all those glass trophies I've seen that are nothing more than a triangular piece of 3/8" glass with beveled edges.

Those are cast and ground to a polish at the factory. All the trophy shops can do is set up a sand-blast template to engrave. The fancier ones can do ground engraves and polish. But the base shape is still sourced bulk (that's where I got the glass for my anamorphic lens... just no engraving )

C

[Jed]

Thanks Jed! Now if I can get them to sound as good as the Bagby/Salk speaker does, I will be a very happy camper.

One thing I thought was "interesting" was that Jeff didn't use BSC on that design? Or so I heard. Does the woofer you are using have a rising bass response below 800hz or something of that nature so it's not needed?

[dlneubec]

Those are cast and ground to a polish at the factory. All the trophy shops can do is set up a sand-blast template to engrave. The fancier ones can do ground engraves and polish. But the base shape is still sourced bulk (that's where I got the glass for my anamorphic lens... just no engraving )

C

You know, my Brother in Law is the inventor of the "Panamorph" lenses. Maybe you have heard of them. Several years ago, he did a demo for me on what that lens would do to a projectors image and wow did it make a big difference.

[dlneubec]

One thing I thought was "interesting" was that Jeff didn't use BSC on that design? Or so I heard. Does the woofer you are using have a rising bass response below 800hz or something of that nature so it's not needed?

Here is the way a discussion of this went on the PE forum in regards to no BSC. It makes good sense to me.

Jeff Bagby:

What BSC are you guys referring to? I don't want to poopoo anyone's ideas, Dan can make whatever speaker he desires, but there is no BSC implemented in my speaker. The acoustical rules with this design are quite different than they are for a small stand mounted two-way that most people design. As for the bass tuning; I simply targeted the alignment that yeilded the flattest bass response when the speaker is used in it's recommended room location. Wolf's suggestion of where to place it is really far from ideal for this design. I hate to say it, but I think I need to, following some of these suggestions will result in a speaker that sounds quite different then the one you guys heard in Richmond.

Pete Schumacher:

Woofers mounted closer to the floor benefit from boundary reinforcement from the floor. They are effectively on a baffle that is as large as the floor at the lowest frequencies, and therefore, no BSC is required. As you go higher in frequency, the boundary reinforcement diminishes, and if you cross at the right frequency, no BSC for the woofer would be needed.

Jeff Bagby:

Yes Pete, you are correct on all points. In most cases when using a larger woofer like a 12" driver, the woofer to midrange crossover is not very high, the baffle is fairly wide to accommodate the woofer, and the floor is acoustically close (compared to the wavelength of the sound produced). All of this adds ups to a driver that is primarily operating into 2Pi space over its operating bandwidth, and therefore no baffle step actually occurs

[Jed]

I'll be interested to see how much BSC you use in your design Dan. I don't really think the woofer is acting completly in 2pi space, maybe +3 dbs or so from the floor, but then again a lot of folks like speakers with only 3dbs BSC anyhow.

Taken from musicanddesign.com by

However, if we consider a typically floor standing 3-way speaker system it would not be unusual to find the woofer located close to the floor and the midrange at a height of 2 to 3 feet above the floor. If we further assume that other than the floor the speaker is positioned far from other surfaces then we can see that somewhere across the frequency range of the system a transition form 4PI to 2Pi radiation will occur. Furthermore, since the woofer and midrange are at different distances from the floor this GP related transition
can occur at different frequencies for different drivers. If we assume that the wave length is long compared to the distance between the source and the GP when the wave length is 3 times that distance, then a midrange
driver positioned 3 feet from the floor would be operating in a 4Pi environment above approximately 125 Hz (wave length 9 feet). This is a reasonable lower limit for the crossover point of a midrange driver. Thus we
may consider the midrange to operate in 4Pi space and have uniform radiated total power as long as its DF remains constant (and we are below the baffle step frequency for a monopole system). By the same arguments, the woofer system, being close to the floor, say 1 foot above the GP, will be operating in 2Pi space at frequencies as high as 375 Hz. Thus the woofer can be considered to operate in 2Pi space over its entire frequency range. Now, returning to the conclusion reached above we can see that if the midrange and the woofer have the same DF and the system is designed to have flat on axis response over its entire frequency range, then the total acoustic power radiated by the woofer will be 3dB below the power radiated by the midrange. This result is independent of the system type, be it a full range
monopole, dipole or cardioid..

So I agree and disagree with JeffB, it depends on where you will be crossing over to the midrange that will determine how much BSC you use and the desired power response....

[augerpro]

I think the important phrase in JohnK's post is "if the woofer and the midrange have the same DF". In the case of JeffB's design and Dan's here the DF is not the same, with dipole mid and monopole woofer. In this arrangement, assuming the woofer is operating in 2pi due to the floor, it's actually radiating 3dB (pretty sure it's 3dB, have to look at JohnK's page again) MORE power than the mid, given a flat on axis response. This is great for Jeff and Dan from a BSC perspective, not so great for me who wants to use a dipole woofer :cry:

[cjd]

You know, my Brother in Law is the inventor of the "Panamorph" lenses. Maybe you have heard of them. Several years ago, he did a demo for me on what that lens would do to a projectors image and wow did it make a big difference.

I didn't know. Now I do. I'm familiar with the Panamorph line, but between the cost and the limitations on throw (I can run shorter throw since I run oversize glass) it was just never a consideration for me. Plus, I can't beat the DIY bug...

[Jed]

Brandon, he goes on to say at his website and I quote from there:

Before discussing how such a woofer could be constructed it is instructive to considerer what the result would be if a speaker with a dipole midrange were mated with a monopole woofer system. In this case the midrange would still radiate a power of 4Pi/3, but the woofer would radiate a power of 2Pi when the on axis response is matched to the midrange level. This results in the woofer radiating 1.5 time the power or +1.76dB more power than the midrange. While not a perfect match, it is certainly better than the -3dB result obtained by using a dipole or cardioid woofer system, or by using a monopole midrange with a monopole woofer.

That doesn't sound like enough to eliminate BSC, and not in my experience with the Tombstones, which operate with this "Allison configuration."

[augerpro]

Ah, you're right Jed. I was thinking 3dB might not be correct when I wrote it. Still though, certainly better than running a dipole woofer with dipole mid. How are you using this "Allison configuration" with the Tombstones?

[dlneubec]

From what I recall, Allison promoted getting all drivers as close to at least one bounday reinforcment as possible. In Jed's case and the case of my HOSS design, it is only one driver, the woofer, close to one boundary, the floor. Allison designed his speakers to be placed against the wall, so the woofer was as close to at least two boundaries as possible. He made them closer by using a couple methods. One, put the woofer at the base of the cabinet and down fire the woofer at a 45º angle, so its center could be within 6" or so from both the floor and the front wall . Another was to angle the baffle 45º away from a wall, so again the woofer was close to two boundaries. He also had one designed to go right in the corner. He also tried to put his midrange and tweeter close to at least one boundary, for similar reasons. He also had some later models that had top mounted, up firing woofers to get them close to the wall, but that did not have the full benefit of being close to two boundaries. I have a copy of most of his published papers.

I've been thinking about doing an Allison inspired design that is intended to sit right against the wall. This might be a good approach for a home theater speaker design. It is on lmy list of things to do. I have some early ideas roughed out, but that's about as far as it has gone. It will probably be he next project after the BaSSlines.

As far as needing BSC, I can only tell you at this point that Jeff's speaker did not sound thin in the bass whatsoever. It is probably the best sounding speaker I've ever heard. That is pretty much proof enough to me that his appoach worked and will work for me. Time will tell. :W

[Jed]

I'm sure it did sound great Dan, and I'm not trying to say otherwise. I just wanted to point out that what worked for that design, may not work for yours, nor did it for mine. Also, I think JohnK's info I quoted above explains the "why" factor- which is also tied to my original question of whether or not the woofer's response possibly has a slight rise down low... that's all.

I look forward to seeing your progress on this one, and it definitely has me interested... if I only didn't have so many designs unfinished right now I'd give some of those B&C drivers a try. Well, maybe next month.

[Paul Ebert]

I'm sorry, but I'm drawing a blank. DF?

Thanks.

[Jed]

I'm sorry, but I'm drawing a blank. DF?

Thanks.

Directivity Factor

[dlneubec]

Opinions Please

Hi all,

Based on feedback, I have put together a couple other options for how these will look. What do you all like the best? :rollhead:

Original:



Vertical laminations on bass bin:



Vertical lamination's and center accent:

[tf1216]

I like your first option the most. All three look beautiful!

[---k---]

Second. I like the way the vertical lamination flows into the top piece.

I'm not an engineer and not an artist. But, I would probably experiment with the round wood ovals for the mid and tweeter. I think the round shape doesn't jive with the triangle shape of the enclosure. Don't listen to me, I'm always proved wrong by artists and I try to let them do what they do best and stick to what I do best.

[cjd]

Curious: why have the top baffle vertical, and not continue the slant?

What happens if you add a third center stripe to the last option that goes all the way up?

C

[David_D]

I just took a quick look at polycarbonate and a Lexan sheet 1/2" x 24" x24" is $75.80 at USplastics. A Makrolon polycarbonate sheet, however, of the same size is only $35.88, which is as cheap as I found he Acrylic for. I'm not sure of what differences there are between Lexan and Makrolon, but the both are polycarbonate.

Hi Dan,
I have used both brands on custom machinery. No difference. I'm not sure about your pricing though. US Plastics shows both brands at 24 x 24 to be around the same price. Are you sure you were not looking at the 12 x 24?
Polycarb is polycarb.

[dlneubec]

Curious: why have the top baffle vertical, and not continue the slant?

What happens if you add a third center stripe to the last option that goes all the way up?

C

I may continue the slant. I want to test the drivers in a test baffle that approximates this one (out of mdf) at which time I will test flat and sloped to match the bass bin. If I sontinue to slope, the vc's come very close to being time aligned, especially if I mount the tweeter in a 1/2" deep waveguide. If I do sloped, then I have the option to do one continous baffle, with no need for rear bracing of the open baffle mid panel.

I think we may have a winner on looks from one of these.