Finished ZDT3.5 including CC *Pics*

Again, very beautiful work on these. And the feet that we came across on ebay don't look too shabby either. Love the CC.

Yup. Still think these look great. Good Job!

What are your impressions on how they sound?

Do you remember the flush and cut out diameters for the woofer and mid driver?
Did you do the two chamber or one chamber approach?

outstanding workmanship!

and who said DIYers can't compete with commercial finishes!

i am going to be order parts to build those myself soon. Nice work.

Can I ask what the approximate cost for each speaker was?

very nice work.....what did you use for your baffle, spray on bedliner?

The diameters are on PE's site and they are correct. I looked at my test cuts and it appears that the woofer is 3/16" recessed. The mid is 1/8" recessed. I don't have good calipers to accurately measure, but eyeballing with a tape makes me think these are the right recesses.

One tip with the cutouts for the drivers is to do the recess cut with a 3/4" bit and adjust your circle jig to take the larger bit into account (the Jasper Jigs are marked for a 1/4" bit). This will let you get the flat area cut in one pass. Then punch through with a 1/4" bit. It does mean a bit change, but it is quicker in the long run.

Also check out blktre's threads at the HT Guide DIY forum and the PE forum. There's lots of good info there and too much to repeat here. His threads are still on the first page. I built these before they were the PE featured project using the Aura tweeter (ZDT3), and there is a thread about them on the HT Guide forum but it is buried a ways.

Edit: BTW, Here is my build.

Now this is first class work ! DIY cannot compete with comercial...

This proves it can. I admire work like this,this is something you can show with pride.

I just hope I can come remotely close to this sort of quality when I start my main speakers.

are you going to build covers for those?

I like to say, I will take the time but in the end its not going to happen all my sub builds are prove that

If I want a truely comercial finish I should just buy my boxes but I shall see.

Will you document your grills? I would love to follow that.

Outstanding workmanship. Just outstanding.

I didn't document my grill construction, but here is the end result and what I used. The grills are of course removed for serious listening, but they (hopefully) help keep little fingers from messing with the drivers. The WAF for these speakers is already high, but the grill help even more.

The finished product on my ZDT3s:



What I used for the sides and cross braces:



On the right is the cross brace material, it is 1/2" x 3/4" actual dimensions. The round is not a quarter round, I don't know what the correct name is. It is 7/16" x 11/16". The triangular corner pieces (seen below) are just 1/2" thick pine that I cut to size. Recess the cross and triangular corner braces a little bit so that when the fabric stretches across the grill you don't get the braces pushing up on the fabric. All wood for the frame is glued together with Tightbond wood glue.

The grills are held in place against the baffle mounting bolts with the neodymium magnets PE sells, P/N 329-045 . I drilled holes for them and sunk them, then placed the green felt over the magnets to avoid scuffing the bolt heads. You'll need to glue the magnets in place as they will pull out of the wood. They are strong suckers.

I spray painted the frame black so that the wood wouldn't show through the cloth. The cloth is held in place with hot melt glue. I ran a bead of glue and then pressed the fabric to the glue. Blktre suggested that upholstery adhesive may work well. The hardest part is the corners. You need to cut the fabric so that it rounds the corner with no seams or bunching, and you have to cut and trim it on the back so that it doesn't bunch up.

The back:



Trust me, from the front they look very nice. The back could look a little better and isn't up to my normal anal retentive obsession with detail.

Absolutely beautiful speaker! I would dearly love to built a pair myself, and have actually been looking for a design like this for a while. Unless I'm mistaken those are Dayton Reference woofers.

BUT, and this is a big BUT, I don't like the rear ports. I recently purchase some rear ported JBL's. I've got them about 10" from the back wall, and at that distance, they sound terrible. So, I plugged the ports with some foam which improved them noticeably. But what is the point of having the ports if the average person has to plug them?

I've been told that rear ported speakers need to be Minimum 0.5 meters (19" to 20") from the back wall, and Minimum 1.0 meter (39" to 40") from the side walls to allow the ports to 'unload' with no interference with the front.

That's fine if you have a living room the size of an auditorium, but for a more average living room/media room, speaker encroaching 20" into the living space is not very practical.

In the above example, the lower 0.5-way section could be ported in the front, but the upper 3-way section doesn't have enough room on the front to do so. I guess other than having no room on the front, I can't think of any reason why I would rear port a speaker system. More likely, I would adjust the cabinet dimensions to make room on the front.

So, enough of my whining.

I do have a question, on the drawings, it seems to show a section 8.3" up from the bottom. Is that a lower chamber, or is that section at 8.3" simply a brace?

If it's a lower chamber, that would mean the cabinet could be a few inches shorter? Yes? No?

Still, all-in-all that looks like one sweet speaker.

Steve/bluewizard

Fabulous work and a great choice with the rift oak veneer. We talked about veneer types in another thread, and I personally think the quarter cut and rift when using oak makes a much more satisfying "professional look" grain patterning. Nice work and congratulations to both of you.

You can build the ZDT3.5 and the CC sealed if you wish.

Before he posted any such sealed version, I just asked him. He said it'd be fine. Thing is, the ports are only there to help out with extension and low end output. Taking them away is not going to significantly change the speaker in any other way. You're safe to build a sealed main.

Well, there is certainly plenty of room for a front port in the bottom 0.5 woofer chamber. The upper 3-way section is the problem.

At the moment, I'm wondering it I couldn't eliminate the bottom empty chamber, and expand the upper 3-way chamber downward to make room for a front port. Perhaps two smaller ports rather than one big one. To compensate for making the 3-way chamber taller, I could add a false back to the 3 way section. In a sense, a chamber within a chamber. The back box section of the 3-way could contain the connectors and crossover. Hopefully, it could be done so that the upper and lower chamber volumes came out the same in the end.

Until I had a rear ported speaker, I thought it was a good idea. But in practice, in most common real-world real-people living/media rooms, keeping the speakers 20 inches or more from the back wall simply isn't practical. Keeping it closer to the wall compromises the sound, and plugging the port seems kind of pointless; what good is the port if it's plugged.

The JBL Stadiums, which I recently bought at a bargain, were extremely disappointing for the first couple of weeks until I stumbled across the idea of plugging the ports. That cleaned up the sound noticeably. The speakers are still disappointing, but far less so with the ports plugged.

The JBL's are growing on me, but they will never equal my much cheaper 12" DIY speakers with horn mids and horn tweeters.

So, don't mind me, I'm just ranting about how disappointed I am with rear ported speakers from a practical and functional perspective. After having lived with them, I would certainly never have another pair, unless I got some of the big lottery money and had an extremely large room to put them in. Even then, it would be doubtful.

The irritating part of the JBL's, is that there is plenty of room on the front of the speaker for the port. Why use a rear port if you don't have too?

Steve/bluewizard

I would not form a blanket opinion of rear ported speakers based on one experience with those JBLs. And your observation about them sounding better with the ports plugged could have nothing to do with the rear port placement. Those speakers could have been tuned to make the bass boomy and have "punch" at the expense of accuracy. By plugging them you could have made things better regardless of the port location. Yes, rear ports can't be placed extremely close to a wall, but you don't want to do that with any speaker. So the issue really is moot. People can make just as many arguments against front ports as you can make against rear ports. In fact, you will probably find more people against front ports than you'll find against rear or down firing ports. IMHO, it is more trouble to try and front port the ZDT3.5 than it is worth. If rear ports are that big of a deal breaker, I'd look for another design.

That being said, I'd put my ZDT3.5s against any front or rear ported speaker and challenge you to tell me that the bass sounds bad. Nobody that has heard them has ever made any negative comments about the bass. And mine are a little over 12" from the back wall because with little kids I can't really get them out further. But even if I could I don't think they need to be further from the wall.

As for building the ZDT3.5 sealed, don't expect the bass extension to be as good as vented. If you are using a sub and will never run the towers full range, then sealed would probably be a more viable option. I believe Krutke's comments about sealed were primarily for a center channel and/or for towers that were only used with a sub. I'd run some sims with the RS180 in a sealed enclosure of the same volume as the ZDT3.5 to check what the change would do.

StangBat, I'm not ignoring your advise; it is well heard, duly noted, and much appreciated.

Though I can afford it under any circumstances, I've been looking at Dayton WWMTM designs but not with an 0.5 section. I want both woofers operating together full time. Also, I was considering maybe 8" woofer, but more likely 10" woofers. But keep in mind, this is all dreaming, and it is easy to dream big.

Also, this isn't a custom designed exclusive cabinet. It is a cabinet that Zaph has used for several designs, and he just moves the internal chamber partitions up or down to created the appropriate internal volume. As such, I don't think I'm that far off in readjusting the dimensions to accommodate front ports as long as I leave the internal chamber volumes the same.

As to the JBL's, I've got a fairly small listening room, though it does connect to an open kitchen which in turn connects to an open dining room, so the speakers are unloading into a fairly large space even though the listening room itself is pretty small.

My speakers are about 10" from the back wall and that is about the best place for them and is consistent with my previous DIY speaker which are front ported. At that distance with the bungs out, the bass and midrange were horribly indistinct, muddy, and muffled. Voice is important to me as I listen to a lot of TV through these speakers. Plugging the ports with 2" open cell upholstery foam cleared it right up. Most distinctly cleared it up.

Now, I only paid $200/pair for the JBL Stadiums, and for $200 they sound OK (Best Buy floor demos). For $200 I can't complaint, though I will. But I didn't buy them expecting $200/pr speakers; I bought them expecting +$600/pr speaker and in that light was sorely disappointed.

Now I complained (actually whined) about this in other forums, and people said that I needed to get used to them; that I needed to listen long enough to get my old DIY system out of my head. My old DIY system has a 12" CTS woofer, a 4x10 mid horn, and a 3x3 horn tweeter. Admittedly some people find horns tinny and harsh, but I find them very clear, present, and crisp though they have to be turned way down to create a balanced sound.

Keep in mind the crossovers on the JBL are at 300hz and 4000hz, that puts a lot of demand on that little 4" cone midrange.

I bought the JBL's on June 6 and have listened to both music and TV through them every day since then, and they are growing on me, but in Mid and High, they will never equal my old speakers. Right now to get my old DIY speaker as closely balance to the JBL's as possible, I have the midrange turn down to the 'I' in 'MIN.' on the L-Pad dial, and still my speakers have clear, crisp, and extremely present midrange compared to the JBL's. Voices on the JBLs are clear enough, but they sound flat to my ears.

So, time to correct some long overdue problems with my old DIY speakers which originally cost me less than $250/pr plus labor. The speakers are made from cabinet grade high density particle board birch veneered wood (50 pounds each). My current mods are going to cost me about $70 and a little labor. If these JBLs are $600 speakers then my DIY speakers are $1,000 speakers, or at least the will be when I'm done.

Now, the JBLs have decent bass, certainly deeper than my old speakers, and the mids are clear and distinct, just a little flat. So overall I would probably think they were a decent speaker IF I didn't have my speakers for a side-by-side comparison.

So, I'll use the JBLs until my old speakers are rebuilt, and then sell them...or maybe not. I played an action video with all four speakers playing and it was devastating. (Keep in mind this is pure stereo, not surround sound) The sound was so intense, my anxiety level shot through the roof. I was literally trembling with excitement.

So, as not to highjack this thread. The Zaph speaker are appealing, but I just can't see the rear ports working properly in a cramped space. Consequently, if I every had the resources to build these speakers, I would make adjustments that would allow me to front port them. Hey, that's just the kind of guy I am.

Love the Zaph speakers, and the workmanship on the current examples is very impressive. How can you look at those speaker and NOT want them?

Steve/bluewizard

Steve, I understand your constraints but I think you are unfairly passing judgment on rear ports based on one experience with a speaker that is probably not very well designed in the first place. The ZDT3.5 is arguably in range of $5000-$10000/pr commercial speakers. So passing judgment on the ZDT3.5 and all rear ports based on a $200 JBL really isn't fair. Also, the ZDT3.5 is not really a speaker for small spaces anyway. John states this a few times in the writeup.

A properly designed rear ported speaker should have no big disadvantages, and arguably have advantages over a front ported speaker. And they really don't have placement requirements that are much different from any speaker (closed, front ported, etc.) I don't know what goes on in John's head when he is designing and I don't claim to know, but it sure seems like he does not cut corners and sacrifice sound quality within reason. If rear ports were really that bad, I seriously doubt you'd see them in ANY of his designs. I also seem to remember he had a post on his blog a while ago discussing front vs. rear ports and the conclusion was that *front* ports aren't as bad as their reputation with proper design considerations. And as far as I know, front ports actually have a worse reputation than rear. Edit, the post can be found here a ways down the page:
http://www.zaphaudio.com/tidbits/

I'd suggest listening to other rear ported speakers, even the ZDT3.5 if you have a chance, before going to all the trouble to redo the design. If you are around the KC area I'd be happy to let you listen to mine. There will also be two pairs of ZDT3.5s at the Iowa get-together in October. Give more rear ported speakers a chance before writing them off as poor performers. I honestly think you'll come to the conclusion that they are not bad, and they don't have any worse drawbacks than the drawbacks any loudspeaker design has.

Again, well heard, duly noted, and much appreciated.

You say -

"A properly designed rear ported speaker should have no big disadvantages,.."

I'll amend that to say, a properly designed rear ported speaker should have no big disadvantages properly placed in a proper room.

But sadly, the average house has few room that anyone would consider 'proper'.

If, I had a house with a media room that allowed proper placement of speaker whether front ported or rear ported, I wouldn't be so concerned. If fact, I would be far more prone to not caring if my speakers were front or rear ported.

But I suspect I hang around with a lot more economically disadvantage crowd than you do. But just because we are broke doesn't mean we don't like good music. Consequently, I'm always looking for the most economically advantageous as well as functional way to implement a speaker design. Functionally, in the rooms I or my friends are likely to have available to them, front ports work better. So, front ports it is.

I do see your point, and within the limits of your statements I agree. But my limits or the limits of the parameters available to me are different than those available to you.

Still, I see your point and concede the general correctness of it.

Steve/bluewizard