Nameless 2-way speaker build

The Appreticeships - Hmm, can't edit the title... that sucks.
January 2011





Thanks for looking at my DIY speaker build. Here is a little bit of info about this build. I've managed to build an excellent sounding, compact, easy to construct 2-way speaker, that costs about $150/pair including all materials. This is the perfect build for someone lacking good tools and a tight budget. This is not a unique build. There are hundreds like it. I built it so I could learn XO design. Read on to see what I mean.

2 way
Sensitivity = 83 db/w/m
Impedance = 8 ohm nominal
XO point = 2300hz
Frequency response = ~50 - 20,000hz
Cost = $150/pair

The Concept

Before I did anything, I had a few ideas of what I wanted from this new build. They included:

1. Cheap - $150 total to be exact;
2. Small;
3. Simple;
4. Original (my own XO design, not an original concept);

To keep the objectives, it was obvious it had to be a 2-way. I also intended them to be used with a subwoofer, but I didn't want to be limited to having to use it because I live in a town house. They’ll be used for HT use and music.

Drivers

Peerless 830656

http://www.solen.ca/pub/cms_nf_catal...au2=1&niveau3=



Dayton ND28F-6

http://www.solen.ca/pub/cms_nf_catal...au2=1&niveau3=




Driver Update

I've now had these drivers in hand and played with them a little. I came across a problem with the Dayton ND28F-6 tweeter. I wasn't able to measure DC resistance so I tried to play some test tones. No tones. A dead tweeter? Nope. One of the leads in the body of the tweeter was disconnected. See picture:



I was able to determine this while the ohm meter was connected I fiddled with the leads and it made contact. So the lead is just touching inside the tweeter body Hopefully it keeps contact I'd say that's a good strike against this tweeter. If it give me problems I'll return it or something. Not sure what Solen's return policy is. I've had it for a while now before discovering the issue.

Edited by tuxedocivic - 6/18/12 at 1:47pm

Enclosure

The enclosure is an important part of any speaker. For kicks I once listened to a 2 way system before installing it in the enclosure. It was not a good sound

A couple things to look at here is going to be diffraction, enclosure type, port tuning, and shape.

Tweeter placement

Originally I was going to center the tweeter because I like the look better. But then I read some things on the internet about how offsetting the tweeter minimizes diffraction. Just so we’re all aware, diffraction is the sound waves bouncing off the edges of the baffle giving a ragged response. The common practice to minimizing this phenomenon appears to be to offset the tweeter. Offsetting the tweeter means the tweeter will be at different distances to each of the baffle edges, so the diffraction is spread out.

I thought about this some more and changed my mind back to centering the tweeter. The room placement I have to offer is not going to be very good. This is my living room. They’ll be ear level, but not necessarily on-axis very often. When the speaker is off-axis, it seems that the internet world of DIY speakers agrees that leaving the tweeter centered is better. I haven’t found an explanation, but the results of testing approve this thought. Also, I think the theory of it would be that the distance of each baffle edge to your ear will be different off-axis. That’s my theory, it’s in the geometry, just like offsetting.

Something else that I will be doing (provided by Dad’s router from 1978 works) is rounding over the baffle edges. This helps with diffraction, even though it isn’t as attractive.

So I’ve decided to leave the tweeter centered and tight to the woofer.

Woofer Placement

I didn't think I was going to need this section. But notice the truncated frame. Good thing this doesn't need to be countersunk! Anyways, the bonus of that style of frame is getting the woofer and tweeter close together. I planned on that as well. Then I got the woofer in my hands and started thinking about diffraction some more. The truncated portion of the frame is straight and sharp, unlike the curved portions of the frame which are rounded and smooth. I don't want the tweeter frequencies difracting on that frame edge. So I've decided the run the truncated portions vertically. It kinda looks better too

Unibox Measurements

I had quite a few box alignments posted that really cluttered this post up. To see all of them, check out my photobucket link here: http://s874.photobucket.com/albums/a...aker%20Design/

Well, I've decided on a 8.7L (9L minus port, driver, etc.) vented box tuned to 51hz.

The comparisons above aren't exactly fair because notice, I've moved the xmax line up to the correct 3.5mm and I've put the power to 15W. You can see a rise of about 1db below 150hz which offsets some early driver roll off. And then really dives below where my sub should pick up on this. The box is really small!! And I can stuff the port and try it sealed. The 51hz is just so I don't have to cut the port. Essentially a 50hz tune

Although some of the other alignments appear to go deeper, this driver is down 10db by 40hz, so I just don't want to rely on this woofer for bass output. I may use my receivers active cross over even when the sub isn't being used to protect the woofer from unloading below 50hz. The more I study this woofer, the more I realize it's a mid woofer. I have to think of my system as a 3-way and the sub is the bass woofer, and the peerless is the mid woofer. These are not going to make very good full range speakers... are we surprised





Ok, here is a box plan. Some things I missed and am to lazy to add:

1. The tweeter is 70mm from the top and the woofer is 190mm from the top (centers);
2. Round over the baffle edges. If you can't, well, it not as good is all.
3. 3/4" (18mm) thick MDF was used. If changing, the box internal volume can change a little without to much issue, but the width should stay the same. If anything, internal volume should be larger, with a lower tune. That would be better than what I have.
4. Port location can change without issue.



Construction

Made another purchase - Wood: $6.15. My Dad had some extra MDF laying around so I only needed a 2' x 2' sheet.





I got lazy and didn't take to many pictures of the construction process. The beauty of this design for someone lacking tools, is the woofer is surface mounted, and the tweeter is dead easy to flush mount. Get a 1-3/4" and 2-1/2" hole saw. Drill the 2.5 into the baffle the thickness of the tweeter flange (about 4mm). Then drill the 1.75 hole saw through the same pilot hole. Now take a chisel and easily chisel out the thickness of the flange, if using MDF. Using plywood may make that step difficult. For me, the flange area just peeled right out perfectly. The tweeter is more like 2.51" so I had to just scrape the outside edge to make the tweeter press fit into it's place.

I rounded the inside edge of the woofer hole, to allow it to "breath". I rounded the baffle edges with a router. If you don't have a router, perhaps give the edges a 45 degree chamfer using a table saw, or sand a lot



I painted the baffle black. The enclosure has been left bare MDF right now. Debating veneer or paint.

There are many articles how to build a cab. This isn't one of them. So if you need more detail about how to build a speaker, I'm sure google can help you out.

Cross Over

Measurements




Note a few things. The strange dip at 3500hz doesn't show up sometimes. I think it's a reflection. But may be real. And the sensitivities are NOT relative. The tweeter is in fact more sensitive. I used zaph's measurements to get a relative sensitivity. The mic was further away while measuring the tweeter. Also, I'm not a pro at taking measurements. Those are actually re-measures from once the project was completed and knew what I was doing more. They do look a lot like zaph's, so this is good.



Below is the XO wired up for listening. Not to complicated! I paralled some caps to get the size I need. Paralleled resistors for the same reason, and I get some extra power handling out of it I suppose.



This is the final XO I used, and which should be used if anyone were to build these:



 

Edited by tuxedocivic - 6/18/12 at 1:45pm

Conclusion

I've done a fair amount of music and movie listening with these. I'm very impressed. To begin, I anxiously wired everything up, hit play, and instantly fear overwhelmed me. These sound terrible! What did I do. I spent all that time and money and these sound really really bad. I measured. Ok, something was seriously wrong. Very little top end output. I had a look at my wiring and found I had the 15ohm shunt resister in series and the 1ohm series resistor in parallel. Ha, whew, close one. Fixed it up and was instantly blown away. But that instantaneous feeling is NOT how you judge a speaker. Of course I was blown away. My creation was finally alive. And I didn't seriously screw up. I'm thrilled. Ok, measure, measure, listen, measure, listen, x10, stop. Take a deep breath, swap some resistors around, look at the model, measure, compare. Ok, I got it.

I ended up padding the tweeter just a tad more, and changing the 10uF cap for a 12. Oh and the parallel coil on the tweeter was a 0.18mH all along (all I could get) without adding any resistance. The woofer was left untouched.

So, lets be subjective. Well, first off, I really was not expecting any bass from this thing. The more I worked on the project, the more I knew I would need a sub. My listening impressions tell me I have no need for a sub for music and I prefer without. For music, I have set my sub XO to 60hz because the 80hz just sounded unnatural compared to the bass from the Appreticeships. Don't misunderstand me though, these are NOT bass performers Just... better than expected because I had such low expectations. I really pushed these a few times. See this video to see what I mean: http://youtu.be/kVRDF-lyVyw

If you have the space, you may want to use one of the other tunings above. Just keep the baffle 200mm wide. I don't think there was a need for me to tune as high as I did. I could hear all the bottom E notes on bass guitars, just not much power behind them. I haven't stuffed the cabs with poly fill yet, just a light dusting. I'll put a pretty big wad in there I think. I'll play with that yet.

They sounded very flat, in a good way. Very tonally balanced. More so than possibly any speaker I've heard, but that not saying much. I haven't heard too many hifi speakers. Totems come to mind. The Apprenticeships are very clean sounding. The last good speakers I heard was a pair of Planet 10's EL70, which I loved and want to build next. They are a full range. I'd say these technically performed better. Stronger bass, flatter response, etc. The EL70's were more... magical??? I dunno. They did different things. These rock, but the EL70's didn't. Jazz music doesn't have quite the transparency (what ever that is) compared to the EL70's though.

Where these lack is outright power. These don't go stupid loud, but plenty loud for me. The bass IS lacking, even though I'm content. With a sub, they have more than enough and you can crank these way up. Otherwise there isn't much to complain about. I've heard better speakers. Even way better sounding speakers. But, for the size and price, I haven't hear any commercial speaker this good.

I know a lot of member here will look at this build and think it's lousy. But they'd be missing the point of why I, or anyone else would build these. I wasn't interested in giant monkey coffin E-waves this time.

Measurements

Well, I was resisting posting final measurements because of my room reflections and poor measurement equipment, but I decided it's the best thing to do, so here you go:



Note, blue is with a 1ohm tweeter series resistor, and red is with a 2ohm. Red looks and sounds better to me. Sorry they're not lined up at the same db. Green is reverse null.

If I get around to it, I'll post in room measurements and off-axis measurements. In room, the top end comes down nice and flat. Just what I was aiming for

Well, I got around to taking off axis measurements, and doing a better job of measurements altogether. Wife and kids are away, so I rearanged the living room. Here you go:

First is a combined nearfield of the woofer, the farfield, and the port nearfield. Note, the stich was made at 500hz, which shows a dip. This is a little sketching in that zone. Likely fills in that trough in the listening position. Remember the farfield measurement was taken where full 6db baffle step would occur. The design is about 2 or 3db of baffle step only.



Then we have horizontal measurements at 15 and 30 degrees. Room is to reflective for me to get 60. See how flat it gets just a little off axis. I won't toe them in, unless I want some extra sparkle and air.



And vertical above axis. About what was expected.



Last, vertical below axis. Better than expected.



Costs

Below I've included ALL my costs other than a hole saw and maybe a couple other odds and ends I didn't feel were a cost to the speaker. Like the 2-1/2" hole saw is a tool I didn't have and can be used on other speakers, or other non-speaker related projects. The cost that are in italics are costs I felt are optional and shouldn't be reflected against the speaker costs. For instance, shipping was really high compared to if you live in the US or something. Or the cost of veneer, cause you could finish these with bare MDF if you really wanted to.

Drivers, ports, and binding posts including shipping - $99. Excluding shipping - $80
MDF - $6
Spray Paint - $2.50
XO parts - $30
Veneer - $50

All in all, I got a good deal on XO parts, overpaid on shipping, scored some free wood. I'd say this is a $150 project. I kept my #1 objective, great, although I ended up veneering driving my cost to ~$200. I also met objectives 2 - 4 I think! My wife loves how they look in the living room compared to my last towers. It was simple to build and used a simple network that I learned a lot doing. This worked out well.

Credits

AVSforum - for letting me host this design/build.
www.zaphaudio.com - for providing 3rd party driver measurements.
kbgl - for consistently offering suggestions and feedback on my enclosure and XO results.
Dave at Planet 10 hifi - for hooking me up with cheap XO component and letting me hear some great sounding EL70s.
And all the others I've missed stepping in here or there, or websites I've drawn information from.

Disclaimers

This design is free to use for personal use if not for profit. I doubt anybody would try and profit from this design, but it would sure make me mad if someone did. This project is open to public viewing so people can learn, and/or build a pair of speakers for personal use. Use outside of that scope is absolutely prohibited. This design is copyrighted C. Ryan Bouma 2011 in all WTO countries. Although not required, I would appreciate anyone wanting to use this design, to PM me indicating so, and I would like to offer any assistance.

I am not responsible for use of this design that may lead to any losses of any kind. If you spend money building this speaker, and you don't like it, all you get is a "sorry".

Proper use of this design includes all the above posts (4) as a whole.

This design/build is not a form of any endorsement to the products and/or vendors used in this speaker build.

Thanks for all the tips guys.

The tweeter has already been purchased, but I'm not bothered. That hump is pretty smooth looking and shouldn't cause too much of a problem. I have already started some XO modelling using the zaph FR plots in Jeff Bagby's PCD. The tweet may end up with a high order filter.

It makes sense that a 6db/oct filter would be forgiving, I never thought of that. And would defintely be cheap. I think the peerless is very well behaved looking. Crossing at 1500 seems low to me. I think it can do 3khz no problem No?

I do plan on rounding the front baffle edges. I've thought about sloping the baffle to align the acoustic centers, right? This is the part I'm going to struggle with. Phase, time alignment, driver spacing. I know the rule of thumb is get them close together and aligned. I'll need to dig into this more.

Right now the question is to port, or not to port. Sealed is smaller. However, I don't want to be forced into using a sub. The peerless is going to roll off pretty high sealed. Being in a townhouse with my living room wall adjoined to my neighbour means I don't want to have to use my sub all the time. He's pretty easy going, but I try to only turn it on when he's not home. So having good bass is important to me. It's all a compromise on this one I think.

Yes I will early next week. Thanks for the input. With a sloped baffle, do you slope the tweeter as well? That would be easier to construct that partially slanted. However, the tweeter would be off axis.

More specifically, it's the acoustic center of the driver. Coil alignment is essentially the same thing though. High frequencies travel at the same speed as low frequencies.

Because the woofer is concaved and the tweeter is domed, we want to align the sound waves with the XO region.

Hey Al, thanks for stopping in to have a look!

Mac tac eh? Haha.

I've updated

I could use some help with the box type. kbgl, perhaps your suggestion for a sealed enclosure is best

Oh and by the way. I got to thinking about my budget and what I could buy for $150. Anybody can walk into a Best buy and buy $150 speakers without lifting a finger. Was all this worth it?

Well, I found these http://www.bestbuy.com/site/Definiti...&skuId=7656404

Definitive technology is a "good" brand right. Similar sized woofer and configuration. A little more money though. Perhaps we can find some info on them.

Perfect, they link us right off their website to this review http://www.hometheater.com/content/d...i-av-receive-1

Ouch!!! There is a 6db rise from 90hz to 800hz. And some crazy peaks and valleys above 1000hz. The specs say a listening range of 47hz to 30000hz. And a sensitivity of 90db. Haha, ya right!

Anyways, I'm quite confident this is going to sound a lot better. If not, I will laugh at myself and Definitive Technology

For what it's worth:





I already tried the others at 10watts but didn't post them. I thought that was pretty high as well. Not sure what's up with that.

How about the 60hz giving that bump to offset the roll off. Does that make sence? Does it work like that?

Wow! Sweet Al. I gotta have a better look when I'm not on my phone. You know how to veneer?

The drivers and bits should be here on Monday. I'll start the building as soon as I can. Maybe next weekend. Still thinking about size, shape, porting, finish, etc.

I updated section 3 with a XO result. I meant to do this last week and forgot. Thoughts?

Drivers were attempted delivery yesterday. I'll pick them up during my lunch break

They are there, bottom left. Acoustic center is -0.025. This is a flush mount woofer and it's quite shallow. When the offset gets to -0.05 the response is really ugly. So hopefully I'm right

Oh and the vertical offset will be more like 110mm so that's a bit off. Not bad though.