A Speaker Dilemma, Please Help!

[Bear]

I think I get it, but I am going to have to think about it alot more before I really get it.

A lot of people don't really get it until well after college. You are significantly ahead of the game if this concept just bounces around your head for the next decade.

[MT Speakers]

Okay, thanks. I've gone about as far as I can without buying anything. I've been pricing out components and found that Madisound is the cheapest. Madisound is the only company that has all of the parts needed.

By the way, I have wooden dowels and I'm going to install them according to Zaph's plan, but I'm waiting until I finish my front and back baffles.

[fbov]

...
In your case, that's just some cross braces and wall treatment, but no fiber fill so the port works.

If I could have choosen a key sentence, this would have been it.

However, re-reading a bit more, I see you've already installed a constraint layer system with your GPO-3... Mechanical bracing will make it even more effective. You should still line the walls with absorbant material, as Thomas notes; OC703/705 are among the best and JM makes a comparable product.

Frank

[MT Speakers]

Kudos to Madisound! :T My father order the parts on Tuesday morning and it came in Thursday afternoon. All of the components were correct and the resistors and inductors were all excellent after measurments.

When my dad ordered the components, Madisound was out of the 4-ohm Eagle (metal-oxide) resistors. So my dad ordered the 4 ohm in wire wound resistors.

As an experiment, I measured the inductance and resistance of all my resistors. I have 4 averages. A 4-ohm resistance average, a 4-ohm inductance average, a 3.5-ohm resistance average, and a 3.5-ohm inductance average. Here's some observations.
* Inductance seems to increase with resistance.
* The 4-ohm (wire wound) average inductance was 26.4 uH
* The 3.5-ohm (metal-oxide) average inductance was 21.92 uH
*assuming the linear resistance to inductance relation the calculated inductance of the wire wound resistance should be 26.04uH.
* The wire wound resistance is higher but only by 1.35%.

So my questions are,
* Can we hear 1.35% difference?
* Is 1.35% improvement worth the much greater cost of the metal-oxide
resistors?
* Are there other advantages to metal-oxide resistors I do not know?

[MT Speakers]

Okay guys, here's my problem. These inductances for resistors seem kind of high.

My 3.5-ohm metal oxide resistor with an inductance of 21.92 uH has a reactance of 2.8-ohms at 20k Hz. I figuered that out from this site.

These values are a big porportion of the resistance! Has this been taken into account with the crossover design? Or, do I need less inductive resistors?

When the police cheif of Gotham City has issues, he shines that bat light, signaling for Batman to come. Hint, hint. Please Zaph, help me!!! :sos:

[fbov]

What tolerance parts did you get? Most are 5-10%, and that's considered in crossover design. Now you are talking micro-henries for the resistors, right? That's an order of magnitude less than the small inductors (~200 uH) in the crossover, or 10%. It shouldn't have an effect on the sound.

Look for threads on the value of premium components to get a perspective on the audible effect of tight tolerances and ultra-high quality components. My gist is that there isn't much audible effect.

Have fun,
Frank

[MT Speakers]

Okay, so here's my gray area. I'm just a little 12 year old kid. People helping me out with this tells me that an inductor is not an inductor but a model of resistance, capitance, and inductance. And, a capacitor is a model of resistance, capitance, and inductance. And, a resistor is a model of inductance, capitance, and inductance. So, since I want to make these speakers sound the way Zaph designed them, I would like to know what resistors he used in the crossover design.

[fbov]

I understand about gray areas. In any design activity, you're walking a line between theory and practicality, at some level. Folks telling you that every component is a combination of every other are telling you the truth, at a theoritically correct level, but in this case, not at a physically significant level. That's a gray area we all have to live with.

When we use components, we know their characteristics. Wire wound resistors have more inductance, but greater power handling; it's a tradeoff you need in some applications. It all depends on what the crossover needs - have you read Zaph's crossover notes?

http://www.zaphaudio.com/SR71.html

He talks about inductor tolerances and capacitor quality, about tuning the components, but nothing on resistors. I suspect that's because theyr'e not critical to the sound. That's the beauty of these proven speaker designs; good ears have tested and prodded and found the pitfalls and marked them for you.

By the way, I noticed your age earlier. When I was your age, I was 1 year away from making my first telescope, maybe 2-3 years from making my first loadspeaker, at 10 years from a degree in Physics. You're right on schedule...

Frank

[Dennis H]

MT, don't get too hung up on the small differences in components. They aren't that big a deal in the big scheme of things. Just build it and I'll bet you'll like it. You're doing great, I wish I was that smart at 12. :T

[evilskillit]

I really have nothing to constructive to contribute to the thread but I wanted to say that I just built my first proven design last year at 26. I wish I had speakers this good when I was 12 so good for you for getting your foot in the door early. Don't give up, everybody here is extremely helpful and I'm sure you'll be happy with your speakers when you're finished. And you can tell all your friends, "Where do you think I got those awesome speakers? Wrong, I built them."

[MT Speakers]

Thank you for the input. I told my science teacher about building the speakers. She said that when I finished the speakers, that I could bring them in to show everyone and to get some extra credit points. Earlier on in the month, I brought in my science fair project that went to state to show it since we are learning about Astronomy. Then I told her about the speakers, she said that I could bring them in to show my class, after they were done. Working on the speakers, up to this point, has been great. Today, my dad and I made a router table with a piece of plywood, 2 sawhorses, and washers and screws. Over the past couple of weeks, we to go to my dad's workplace to work. There, they have the Bridgeport and sandblaster that we use. Those inductors and GPO-3 really is ours. Even though my dad is an engineer, he often brings home spare parts from work. During this project, I have learned that projects don't take a couple of days. That was my biggest thing up to this point, long projects. I used to think that projects lasted days. I always wanted to build stuff when I was younger, but my parents said no because when I start it, I would find out that it was too hard and quit. I've done that before with spare plywood. I've also learned about precision. Today, I learned that when getting ready to drill a hole, check it from all angles to make sure that it really is straight. To sum up the experience to this point; up lifting.

Thanks,
MT

[MT Speakers]

Okay guys, today I made worked with my circle jig to make the holes for the baffles. It worked out quite fine. The hole came put perfect everytime! I have attached a picture showing them. There will be 2 other posts with pictures. The centers of the holes; I didn't throw them out. You'll soon see what I did with them.

[MT Speakers]

Another picture

[MT Speakers]

When I bring my speakers into show my class, my science teacher said that I could play 3-4 different song and explain what makes these speakers unique.

So I have one question to ask; what songs should I play to bring out the best in these fine speakers.

[MT Speakers]

fbov, you asked me for the picture, here it is. I couldn't send it to you via pm.

[MT Speakers]

Okay guys, all work and no play doens't make for a happy kid. Since it is spring break and kind of cold and rainy here, we went to Orlando, and hung out at the theme parks and the resort. I was dissapointed because when we used to go to Universal, it seemed like alot of the speakers were home-made. I remember the sound being rich and full. Now they are UBL and Klispch. I have seen the same Klispch speakers at Best Buy. :cry: Since my last post, I have goten more done. A few weeks ago, I stopped working on the cases and began focusing my attention to the electronics. I finshed soldering up the crossover for both the tweeter and woofer. Then I mounted them using silicone. Then, I put on the back baffles. Today, I began to seal the wood using a 1 : 1 : 1 ratio. Eight tbl. spoons of dry, black pigment, 8 oz. of wood glue, and 8 oz. of water mixed together. I'm interested to see what happens when I start sanding.

[MT Speakers]

Picture

[MT Speakers]

Some more pictures

[MT Speakers]

Here is another one

[MT Speakers]

More pictures

[kevinp.]

keep up the good work!

[Dean100]

When I bring my speakers into show my class, my science teacher said that I could play 3-4 different song and explain what makes these speakers unique.

So I have one question to ask; what songs should I play to bring out the best in these fine speakers.

Try to pick some music that you and your classmates are familiar with. Also, you may find music that has really good vocals to sound spectacular on your new speakers. When you have them finished, listen to some music and pick out your favorites.

I think that you will find that your new speakers frequency response is very flat, which will make musical instruments and vocals sound very real. (Uncolored). They will probably also sound very revealing. (Where you can hear details and sounds that you may not hear through other speakers). These are some the things that may make your speakers unique.

Keep up the good work, you are doing great!

[MT Speakers]

What artists use the highest quality recording studios? I ask this because every studio uses different techniques of making and recording the album.

[---k---]

Most albums from Chesky records.

[ThomasW]

What artists use the highest quality recording studios? I ask this because every studio uses different techniques of making and recording the album.

Where an artist is recorded, who does the recording engineering, etc, etc, is all a part of the contract.

For example.......

I have a friend who's a recording and remix engineer. He recently spent 6+ weeks in New Orleans doing the live mix of what will become the latest Dave Matthews Band album. He now has those recordings at his personal studio (in Portland) for the remix. His services, the recording venue, and everything else was a function of the contract for this particular album. He was chosen for this job by reputation. Will he do another Dave Matthews album? Who knows? Will the next Dave Matthews album be done in the same studio in New Orleans? Probably not.

[MT Speakers]

While I was working on my speakers, this guy came to visit.

[fbov]

There are advantages to living in the country...

[MT Speakers]

Okey dokey guys, sorry I haven't been posting for a while. I been busy practicing for my band concert. So, here are some pictures. I've been insulating mainly. Today, we are going to finish insulating. In 2 weeks, I estimate, we will be done.

[MT Speakers]

One more picture.

[ThomasW]

You should leave yourself the ability to experiment with differing amounts of damping. The compressed fiberglass is VERY absorbent so you might have a bit too much damping.

[MT Speakers]

Here is another picture. That is very interesting. I haven't done my insulating on the back yet. I am waiting for this stuff to dry. The caulk that I used was latex. It said to use by 2003, basically junk now. But, I softened it up with some Xylene. It goes on white and dries clear. It brushes on with a paint brush. I think my solution was cheap and I think I didn't have to throw out any toxic waste.

Do you think a layer of 1" thick fiberglass should be added to the back? BTW; I wasn't planning on using any AcousticStuff. Thanks for all of the input.

[ThomasW]

But, I softened it up with some Xylene.... I think my solution was cheap and I think I didn't have to throw out any toxic waste.

Except the fumes of the xylene..

Do you think a layer of 1" thick fiberglass should be added to the back? BTW; I wasn't planning on using any AcousticStuff. Thanks for all of the input.

Lining all the interior surfaces is probably too much damping

Damping should be installed so it can be added or removed as needed to fine tune the performance.

[MT Speakers]

OK, how do you fine tune the performance?

Also, is there a way to measure my port tuning frequency?

Maybe I am more that 2 weeks from completion?

Thank you for your help.

[JonMarsh]

You can measure your port tuning frequency in several ways- by the impedance minima between the two humps, by doing a nearfield measurement of the woofer and seeing where the minimum in it's output at the low frequencies is, or by measuring the port output near field- all of these presume you have access to either an impedance measuring unit, like a Woofer tester, or a mic and PC/Mac software.

Personally, I usually line all the side walls and the back wall, but don't worry about the front baffle wall.

[ThomasW]

OK, how do you fine tune the performance?

Also, is there a way to measure my port tuning frequency?

From our FAQ/Reference section

http://www.htguide.com/forum/showthread.php4?t=17794

[JonMarsh]

Doesn't take any more equipment than a power resistor from Radio Shack and an inexpensive DVM and a Laptop with NTONE. I forgot about that post until Thomas posted the link.

[MT Speakers]

Thank you for all your help, This is really neet. I can do that, I will see if I can get NTONE.

[MT Speakers]

Okay guys, while I'm trying to figure out what I'm going to do about my dampening, I decided to work on the front baffles. They are all sealed and I decided to test fit the speakers and glue the rear retaining nuts in place.

Does anybody know how to attach the wires to the speakers? Is there any specific thing I need to attach it or just solder?

[MT Speakers]

Another picture

[ThomasW]

Solder or use crimp-on spade connectors.

You can download the nice little freeware tone generator here

http://home.comcast.net/~thomasw_2/tnsetupOld.exe

FYI you can put up to 5 attached images in a single post.

[MT Speakers]

Thanks ThomasW. For the rest of today, I was insulating and taking things apart. Yesterday, as you saw in the picture, we test mounted the speakers. Today, we took them out to make sure they would come out. If a screw was glued to a nut, we were between a rock and a hard place. That is one thing we did. If you look at the picture below, we insulated the back, that is the other thing we did today.

[MT Speakers]

We made little blocks out of insulation and glued them to the back baffle. This formed a level surface with the tweeter crossover components. So then, we took off about a 1/4" layer of fiberglass then glued it in as you see.

Before we did that, we fitted the front baffles to the enclosures and measured the woofer inductor inductance. Whoa!!!! It increased from 3.3 mH to 3.6 mH!!!!! I guess that this was from the woofer being kind of close to the inductor. So, we took some winding off all of the inductors until they measured below 3.3 mH.

Now I think I will start testing my box frequency response.

[MT Speakers]

Port resonance test

OK Thomas W, I made a setup and followed the instructions you have in your post. It took me awale but when I got it right it sort of works like you said it would.

My box/port resonent frequency seems to be around 41.78 hertz.

The port extension tube measures 2.25 inches. Installed the standard way accordind to Zaph's instructions. I just installed the speakers and clamped on the front baffle the taped the edges for an air seal. I did not install gaskets behind the speakers. But all the surfaces are very smooth. The insides of the speaker are like my last picture.

I attached a EXCEL spreadsheet of my data. What should I do to fix these speakers?

[MT Speakers]

I need help making some decisions. My measured box resonance is 41.78 Hertz. I went to the Precision Sound Products web site and used their port length calculator. It seems my box is resonating at a frequency that makes it seem bigger than it really is.

How does this effect flat frequency response? I think I prefer flat response more than lower extension.

Should I shorten the port to increase the frequency to the specified 44 Hertz?

I was going to add some blocks of fiber glass insulation around the woofer inductor to cut down on the height resonance. Is this a good idea?

Is the Q of my response OK? Should I be using some Acoustastuff to flatten it?

[ThomasW]

Sorry I missed your post last noc...

I wouldn't worry about a 2Hz difference in Fb. This is probably due to the higher damping effect of the all the compressed fiberglass. Up to a point adding more damping will continue to lower the Fb.

Placement of the speaker in the room will have far more impact on output than any little change in the length of the port.

So I think you're very close to being done...... :T