I don't know what happened. . . .

M

MrBoat

Audioholic Ninja
@MrBoat
Yeah, I could see how constantly designing speakers to achieve ruler-flat accuracy could get to be a bit tedious, so as a speaker designer it is likely a bit fun to do something different or unexpected every now and then.

But, why another JB design? There are a lot of other designers out there to choose from! If I were to do a JB design, I've really been wanting to do those PE Solstice kits with the all-Morel drivers!

Anyway, just in case you have never seen Murphy Blaster, here is a link. I'm sure you hear us talk about Dennis Murphy and Philharmonic audio, here is a link to his DIY design page:
http://murphyblaster.com/content.php?f=main.html
I have looked at other designs from Zaph and those at Madisound. Also looked at Bagby's Tributes with the series crossover, the Docere, Fusion-8 Alchemy etc. Also built Paul Carmody's Classix 2.

Like I said, I don't know what happened. A lot of it has to do with these Tempest speakers and how they turned out. I really cranked them last weekend and these things refuse fail at any volume. Also figure I am using very little EQ with the Tempests, running them in Pure Direct mode on the AVR with just slight adjustments on the high frequency. Figure I'll see what's up with one of his designs at the opposite end of the spectrum.

I will check out the link yopu posted.
 
M

MrBoat

Audioholic Ninja
Jeff Bagby also has an excellent reputation among experienced DIY builders and designers.

The example that I posted above of the frequency response curve of a speaker with a BBC dip is probably an extreme one. When I actually looked at Bagby's frequency response curve on page 2 of his write up, it looked pretty good to me (see below). I'd call that flat within two octaves of the 1.8 kHz crossover. So I spoke too soon.
View attachment 21392
Our ears are most sensitive to variations in the mid range. We can detect changes smaller than ±1 dB in that range. At the extremes of the audio band, we are much less sensitive.

There are measurements and there are preferences. Some people like a flat frequency response and others don't. People's preferences often have a lot to do with what speakers they have become used to hearing. That can vary all over the map.
Yes, and their small size is a key point. Maybe you can get away with using that mahogany. You certainly have the experience. It might help to seal the inside and outside surfaces of the cabinet.

For what it's worth, Jim Salk does build and sell a version of Bagby's Continuum. Note all the screws on the front baffle.
The one thing that constantly bugs the back of my brain with current speaker design is the multipurpose requirements between music and HT. I hope to discover a cutoff point between the two where different bumps and glitches end up being favorable, even if it narrows down into specific genres of music. I think this is already a known, or the information exists but just doesn't sell well. Take the party speakers from "the worst decade in audio." They ended up being the most consistent performer for say, classic rock, which is some of the worst recorded, yet we never knew it until we started trying to play it through accurate speakers.

I also like the looks of Bagby's "Tributes," that were built in essence of Bud Fried.

Something came to mind when looking at the hardwood vs MDF or plywood of this design. A lot of small speakers are built with 1/2" material. The wood for these Continuum is spec'd at 3/4 so, it seems a little compensation occurs here. I have to see how they are filled, and with what, as well. The plans do state one can use either or.

This kit comes with the hurricane nuts and screws for the front baffle. I also have a 100 count bag of hurricane nuts. I could give the rear panel the same treatment to help further alleviate the expansion/contraction factor and even use plywood there. I certainly have enough MDF here in the event it doesn't work out.

Midrange has always been my thing. It was one of the adjustments I favored in the days of the graphic EQ. I knew that range since the music I followed was also midrange rich.
 
M

MrBoat

Audioholic Ninja
$1300/pr for the Salk version. That's getting into very good bookshelf speaker territory price wise.
Especially as small as these are. These are essentially desktop speakers.
 
M

MrBoat

Audioholic Ninja
Just putting this here as a point of reference albeit a bit long winded, that could and likely is summed up with a read elsewhere around the net but I found it interesting nonetheless.

History of the LS3/5A - The Hifi Hangar

Also, another website dedicated to the original LS3/5A speaker, with a DIY section with some information for those wanting to research building clones of these speakers.
http://www.ls35a.com/
 
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Swerd

Swerd

Audioholic Warlord
The one thing that constantly bugs the back of my brain with current speaker design is the multipurpose requirements between music and HT. I hope to discover a cutoff point between the two where different bumps and glitches end up being favorable, even if it narrows down into specific genres of music.
I have a simple take on that question. Speakers that sound good with music will also sound good with HT. It makes no sense to me to have two sets of speakers, one of which sounds poor with music. In my experience, a speaker with a flat frequency response across the critical mid range will do both music and dialog well. In fact, I'll go so far as to say that the few 'HT specialist' speakers I've heard sounded lousy – but they were extremely loud, especially in the bass range. And that seemed to be far more important to the owners of those speakers than anything else.
Something came to mind when looking at the hardwood vs MDF or plywood of this design. A lot of small speakers are built with 1/2" material. The wood for these Continuum is spec'd at 3/4 so, it seems a little compensation occurs here. I have to see how they are filled, and with what, as well. The plans do state one can use either or.
¾" wood can always help lessen vibrations better than ½". So can cross bracing in larger cabinets. Usually cross bracing is skipped in smaller cabinets. After you build your ¾" mahogany cabinets, you can always add an internal cross brace or two if you think it's needed. But you can't easily make ½" thick sheet goods into ¾" thick.

The filling in speakers with sealed cabinets helps deepen the bass response. It makes the air volume act like it's larger (as much as 20% larger) than if there was no filling. It has little to do with damping vibrations in the cabinet walls. The type of filling material (polyester, glass wool, real wool, recycled denim fiber, etc.) can also matter, but much less so.
This kit comes with the hurricane nuts and screws for the front baffle. I also have a 100 count bag of hurricane nuts. I could give the rear panel the same treatment to help further alleviate the expansion/contraction factor and even use plywood there. I certainly have enough MDF here in the event it doesn't work out.
Do you have a drill press? If so, you can probably use hurricane nuts without problem. I don't have a drill press, and when I tried hurricane and T nuts, I had problems. The holes for the nut shafts all have to be parallel. Otherwise the last bolt you put in won't thread properly. I've had much better success with threaded inserts. I use MDF for speaker cabinets and I use the flanged inserts made for softwood or MDF (see below), but there are also inserts made for hardwood.
 
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M

MrBoat

Audioholic Ninja
Au contraire mon frère, but you are talking to MrBoat who can pour 1/4" epoxy onto the panel and "inertify" it!:cool:
lol. . .I also have a vacuum bagging stabilization process that plasticizes wood and other porous materials. Epoxy, I like to use on MDF that will be painted. I am not a fan of MDF. In spite of it's acoustic properties, it's really dreadful stuff with regard to machining or anything involved with fasteners. It's a good way for industry to make a profit on it's sawdust. Granted, it typically machines/glues well and is inherently stable but it has no real structural capacity in any direction without engineering a good amount of overkill into it.
 
M

MrBoat

Audioholic Ninja
I have a simple take on that question. Speakers that sound good with music will also sound good with HT. It makes no sense to me to have two sets of speakers, one of which sounds poor with music. In my experience, a speaker with a flat frequency response across the critical mid range will do both music and dialog well. In fact, I'll go so far as to say that the few 'HT specialist' speakers I've heard sounded lousy – but they were extremely loud, especially in the bass range. And that seemed to be far more important to the owners of those speakers than anything else.
¾" wood can always help lessen vibrations better than ½". So can cross bracing in larger cabinets. Usually cross bracing is skipped in smaller cabinets. After you build your ¾" mahogany cabinets, you can always add an internal cross brace or two if you think it's needed. But you can't easily make ½" thick sheet goods into ¾" thick.

The filling in speakers with sealed cabinets helps deepen the bass response. It makes the air volume act like it's larger (as much as 20% larger) than if there was no filling. It has little to do with damping vibrations in the cabinet walls. The type of filling material (polyester, glass wool, real wool, recycled denim fiber, etc.) can also matter, but much less so.
Do you have a drill press? If so, you can probably use hurricane nuts without problem. I don't have a drill press, and when I tried hurricane and T nuts, I had problems. The holes for the nut shafts all have to be parallel. Otherwise the last bolt you put in won't thread properly. I've had much better success with threaded inserts. I use MDF for speaker cabinets and I use the flanged inserts made for softwood or MDF (see below), but there are also inserts made for hardwood.
Valid points. I do have a drill press. The inserts I have are like those in the photo. I still epoxy them in regardless. There are tricks to drill straight holes with a hand drill.

I'm not dead set on using hardwood just yet. I am half kidding myself having time/patience anymore for hand sawn dovetails too. I am not fond of the metric equivalent birch ply that's available when trying to adhere to 'inches' as depicted with most plans. I do have a half sheet of Signal MDO which is a full 3/4" and substantially heavier. The other thing I don't like to use plywood for with anything furniture grade, including veneer is, butt construction so, figure on mitered corners, even with veneer. I can always use plywood edged with hardwood where edges will be exposed as a good compromise and be just as happy.

This kit was an impulse buy. Now I have time to think about possible finish grades/treatments and come to my senses a bit.
 
M

MrBoat

Audioholic Ninja
@MrBoat
Yeah, I could see how constantly designing speakers to achieve ruler-flat accuracy could get to be a bit tedious, so as a speaker designer it is likely a bit fun to do something different or unexpected every now and then.

But, why another JB design? There are a lot of other designers out there to choose from! If I were to do a JB design, I've really been wanting to do those PE Solstice kits with the all-Morel drivers!

Anyway, just in case you have never seen Murphy Blaster, here is a link. I'm sure you hear us talk about Dennis Murphy and Philharmonic audio, here is a link to his DIY design page:
http://murphyblaster.com/content.php?f=main.html
Looking over the MB plans, either I am jumping around too much, due to the revisions (MBOW1, MB20, MB27 etc.) on the MB series of speakers (the morel tweeter in the budget version of the speaker is NLA, for starters), but I cannot find information on the 2" port length. Also, on the rear view of the cabinet drawings, they show the port location, and another cutout that I can only assume is for a terminal cup?

I see that Swerd built a pair of these in another thread.

At any rate, my Continuum parts arrived today and will likely build the crossovers before anything else. It's a tidy kit and the drivers have some heft to them for their size. I think I have just enough MDF to build the cases, and enough plywood for the baffles and backs. That would give an effective cabinet to listen to them before deciding what finish they deserve.
 
Swerd

Swerd

Audioholic Warlord
Why is it called void-free?
Voids in plywood are gaps, empty areas in inner layers, usually hidden from view. They can be filled during manufacturing. See the gaps below:


In the USA, void-free baltic birch plywood is more expensive than if it has hidden voids


 
Swerd

Swerd

Audioholic Warlord
Looking over the MB plans, either I am jumping around too much, due to the revisions (MBOW1, MB20, MB27 etc.) on the MB series of speakers (the morel tweeter in the budget version of the speaker is NLA, for starters), but I cannot find information on the 2" port length. Also, on the rear view of the cabinet drawings, they show the port location, and another cutout that I can only assume is for a terminal cup?

I see that Swerd built a pair of these in another thread.
The tweeter for the MB27 (SEAS 27TFFC) is still available at Madisound. I've built it and it sounds very good. In the past, I also built the MB20 with the NLA Morel tweeter. The MB27 is just as good.

In both speakers, the mid woofer, the M130 made by Peerless of India, sold in the US by GR Research, is at $27 a real bargain. It has a very smooth frequency response.

I've also built the CAOW1, same tweeter and cabinet as in the MBOW1, but uses a SEAS CA15 woofer instead of the M130 woofer. It goes a bit deeper to 50 Hz instead of 55 Hz. If you ask Dennis Murphy, he has a crossover modification so you can use a SEAS ER15 woofer instead of the CA15. The woofers are the same size but the CA15 has a coated paper cone, and the ER15 has a paper cone doped with reed (papyrus?) fibers. They should sound identical on their low end, but the ER15 has a smoother frequency response on its high end.

In the cabinets for any of these speakers, I used a 1¾"×4" port available through Parts Express. Use the full 4" length, no cutting was needed. If you think must have a flared port, you can use this 1 7/8" × 5 5/8" port but you'll have to trim it to 4" long.
 
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M

MrBoat

Audioholic Ninja
The tweeter for the MB27 (SEAS 27TFFC) is still available at Madisound. I've built it and it sounds very good. In the past, I also built the MB20 with the NLA Morel tweeter. The MB27 is just as good.

In both speakers, the mid woofer, the M130 made by Peerless of India, sold in the US by GR Research, is at $27 a real bargain. It has a very smooth frequency response.

I've also built the CAOW1, same tweeter and cabinet as in the MBOW1, but uses a SEAS CA15 woofer instead of the M130 woofer. It goes a bit deeper to 50 Hz instead of 55 Hz. If you ask Dennis Murphy, he has a crossover modification so you can use a SEAS ER15 woofer instead of the CA15. The woofers are the same size but the CA15 has a coated paper cone, and the ER15 has a paper cone doped with reed (papyrus?) fibers. They should sound identical on their low end, but the ER15 has a smoother frequency response on its high end.

In the cabinets for any of these speakers, I used a 1¾"×4" port available through Parts Express. Use the full 4" length, no cutting was needed. If you think must have a flared port, you can use this 1 7/8" × 5 5/8" port but you'll have to trim it to 4" long.
I saw the SEAS offering and the Hiquphon tweeter still available as well. I wasn't worried about it or anything. Just that I saw where D. Murphy claimed the bargain choices that saves $100 was his favorite bargain speaker. I think it's great he offers those plans for free. I may actually consider trying those at some point.

I have seen the ER15 used on other models that I looked at somewhere. . .perhaps it was Meniscus.

So, is there mention of the port size in the plans somewhere and I just overlooked it? I'll take your word for it as you obviously have experience with these designs. I thought maybe I missed a section somewhere is all. It was late. lol
 
Swerd

Swerd

Audioholic Warlord
I saw the SEAS offering and the Hiquphon tweeter still available as well. I wasn't worried about it or anything. Just that I saw where D. Murphy claimed the bargain choices that saves $100 was his favorite bargain speaker. I think it's great he offers those plans for free. I may actually consider trying those at some point.
The SEAS tweeter costs $90.20 for two, and the Hiquphon OW1 cost $252 for two. So the MB27 now costs $162 less than the MBOW1.

So, is there mention of the port size in the plans somewhere and I just overlooked it? I'll take your word for it as you obviously have experience with these designs. I thought maybe I missed a section somewhere is all. It was late. lol
The port tube size is mentioned near the bottom of the page for the MBOW1, in the parts list:

port, 4"× 1-3/4"​

All those small 2-way speakers, the MBOW1, CAOW1, and MB27 use the same cabinet and port.
 
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lsiberian

lsiberian

Audioholic Overlord
Things can be done to damp resonances, so that wood might not be a bog deal. Line the interior with some kind of viscoelastic material, and then stuff the cabinet chock full of Dacron. Install extra bracing. I think that will be enough to eliminate resonances from almost any kind of wood.
Just make sure you factor that into the volume of the box. You wouldn't want to be tuned too high.
 
killdozzer

killdozzer

Audioholic Samurai
@Swerd ah, those are actual voids, got it now. Are these voids important only quality wise or are they prime suspects in unwanted resonance? In your post which I quoted, you say that this birch plywood is a better option than most hardwood and I get that, I read a few articles on the subject. I know B&W brags with using Baltic birch. If you aim at building a neutral, non-resonant speaker would any plywood or MDF be better than hardwood or just the void-free types? Or more precisely, if you take some void-free and some regular plywood would there be difference in sound quality?
 
Swerd

Swerd

Audioholic Warlord
@Swerd ah, those are actual voids, got it now. Are these voids important only quality wise or are they prime suspects in unwanted resonance? In your post which I quoted, you say that this birch plywood is a better option than most hardwood and I get that, I read a few articles on the subject. I know B&W brags with using Baltic birch. If you aim at building a neutral, non-resonant speaker would any plywood or MDF be better than hardwood or just the void-free types? Or more precisely, if you take some void-free and some regular plywood would there be difference in sound quality?
My answers to your question are more like guesses than definitive answers.

MDF is inexpensive and resists changes in dimensions due to changes in humidity better than solid woods. It stays flat and does not warp. It is also heavy, poor at holding tight onto screw threads made for standard wood, and makes large amounts of fine sawdust as it is cut. MDF is made from sawdust chemically bonded together under high pressure with formaldehyde. Some people worry that exposure to large amounts of it is unsafe. This is however said to not be true by both industrial and independant scientific people.

Plywood, which is made in many different varieties, can be nearly as resistant to warping or changing shape as MDF, and is not as heavy. It costs more, especially higher quality void-free plywood. Plywood holds wood screw threads better than MDF. Plywood is also made with formaldehyde, but does not make the small sized dust particles that MDF makes as it is cut. Baltic birch is a high quality, and expensive, form of plywood. Void-free plywood frees builders to use screws wherever they wish.

Most speaker cabinets are made with MDF because it is cheap and widely available. Plywood is a lighter weight alternative useful in larger cabinets, such as large PA speakers and musical instrument speaker cabinets. They are meant to be portable, so weight is important. I don't know if anyone has tested the difference between acoustic properties between plywood and MDF speaker cabinets. If a large company like B&W has done that, they have not publicized their results. I suspect, B&W probably benefits more than its customers because the lighter weight of plywood reduces their shipping costs.

So, to directly answer your question, I don’t know if there really is a difference. I suspect the amount of resonance in a speaker cabinet can be minimized by a variety of different cabinet making methods while using either MDF or plywood.
 
killdozzer

killdozzer

Audioholic Samurai
Well, thank you for taking your time.

I wish I've been more precise when asking the question as most of what you wrote is familiar to me. I did a lot of work with wood in general; hardwood softwood, plywood and MDF when I was serving my time in the army. I was working in a carpentry shop. It was mostly furniture for schools and daycare centers and after that for my own use - shelves, kitchen cabinets and such.

You mostly got me interested with this void-free feature of some plywood. I just wanted to know do constructors associate these voids with bad resonance or affecting the sound in any way or is it simply because of holding the screws as you said and not threatening with dents? (For example, if there's an unsuspecting void under the first layer of veneer, you might make a dent even with medium grip, I get that, but is there an acoustic feature of void-free plywood that makes it desirable in speaker cabinet construction?)

In the end you gave me the answer, I'm just sorry I've made you write the whole story by being vague.

thx
 
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