# Received my PE cabs today for a ZRT build



## xyrium (Jul 28, 2008)

However, as you can see, they already had an internal brace installed. Yes, the cabs are for an MTM design, thus, the cutouts for two woofs, but I'm not using it for that. I'm doing a two way sealed ZRT. So, what do you guys think I should do with that thing? I was just going to take a hole saw and wack two large holes in it at the rear of the woofer placement. I left a hole saw in the photo so you can get an idea of where I'm headed. Either that, or get a jig saw in there and just take out the entire center section of the brace. What do you guys suggest?

Here's a photo:

http://img694.imageshack.us/img694/9052/img1667q.jpg


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## xyrium (Jul 28, 2008)

*Xover placement*

Ok, separate subject from my cabinet cutout dilemma. Given that PE put a center brace in the cabs that I bought, I can no longer fit both pieces to the xover on the side walls. The tweeter portion would have to be mounted on the lower portion of the rear wall, while I'll probably stick the woofer portion on one of the side walls. Does anyone see a problem with this arrangement?

http://img694.imageshack.us/img694/9052/img1667q.jpg


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## lsiberian (Mar 24, 2009)

*Re: Xover placement*

What type of brace is it?


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## evilskillit (Oct 7, 2008)

Keep me updated. My friend who has a pair of nice botique bookshelf speakers is thinking of doing the floor standing 2.5way ZRT sealed so I'll be following your build to see how it goes and what your impressions are. I can't imagine that they won't just blow away his Triangle Comete EX speakers but he has gotten used to them, and they're a tad on the bright side. Anyways, I'm excited for your build, keep posting.


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## xyrium (Jul 28, 2008)

Hey Matt,

Will do. Once I figure out what to do with the cab's prefab bracing, the next step is mounting the xover, the absorbing panels, and binding posts. Then, route the baffles, and test. Fingers crossed!

Paul


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## xyrium (Jul 28, 2008)

*Re: Xover placement*

The link has a photo of it. They added a brace the entire height of the cab with two holes in it for woofers. However, between the two holes is solid mdf, and that's where my woofer will probably go. So, I'm trying to determine the best route to go, wipe the entire midsection of the brace, or just hit it with a few hole saws.


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## dyohn (Apr 17, 2008)

*Re: Xover placement*

Why don't you just mount the woofer so it clears through one of the existing openings? If you design requires center mounting (which you should model for baffle edge diffraction effects. Being off-center is usually better) then cut out the brace, but be ready to add a new one back in to give the enclosure structural rigidity. And as far as having room to mount your crossover, if it's too large to fit into one of the available spaces in the enclosure break it up into pieces. It does not have to be physically together.

NOTE: I merged your two threads since they were both asking the same question.


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## xyrium (Jul 28, 2008)

*Re: Xover placement*

Thanks David. The design is a two way, so the woofer would then have to be on top of the tweeter, or mounted too far from it given the placement of the brace. Since I'd like to keep the tweet wand woofer close together, and near the top of the cabinet, I figured that it may b best to just carve out the center of the brace. I suppose I'll just hit it with the hole saws and see how that works.

The crossover mounting is tricky because the mounting plate and binding posts are going lower on the cab, so I didn't want to interefere with them. I'll probably glue some plywood pieces in there, then screw the xovers to them, so they're removable.


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## dyohn (Apr 17, 2008)

There is nothing wrong with mounting the tweeter under the woofer if you want the woofer high in the cabinet. Are you saying the Xover is already part of the binding post somehow? Is it a pre-fab?


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## xyrium (Jul 28, 2008)

Mounting the drivers in that manner (woofer over tweeter) would certainly change the seating position, and tonal characteristics of the speaker, though I do like that "look" if I may. Maybe i'll cut out a test baffle to see hwo well that works.

Nope, nothing is attached. In fact, I might build a small xover box outside the cab because this one is rather large. I'd like to get more damping material inside, probably 1.5" OC703 for the walls and 2" doubled up for the rear, top, and bottom. 

I think we're supposed to get 12-18" of snow this weekend, so I might have some time to get this started.


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## dyohn (Apr 17, 2008)

Woofer over tweet is not new, Mission for one has been doing it for years. http://www.mission.co.uk/ It can present some interesting challenges depending on the tweeter's off-axis response... but sure, go ahead and knock out what you need to knock out from the brace. You can always add different bracing back in if it's needed. If you can't fit your crossover inside, external is of course fine. I like to use old cigar boxes to house external Xover networks.

Snow. Brrr. Good luck!


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## xyrium (Jul 28, 2008)

Oh, absolutely. I've seen many manufacturers, including NHT when they were in business, do that. Unfortunately, you need to design your system around that layout. I'll probably eliminate the center altogether as you've suggested, and add my own (the latter of which was originally intended). 

Ahh, the cigar box is a great idea! Hmm, I have to see what's laying around. 

Have a good one gents!


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## JCD (Apr 20, 2006)

Just one thing, take lots of pictures.. people like me live for this kind of stuff!


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## xyrium (Jul 28, 2008)

Sorry, although we did receive a little over a foot of snow, it was cleared rather quickly, so I had things to do this weekend with the Mrs. However, I've bored out several holes with various hole saw sizes to allow better breathing between sides of the brace, and I glued the xover mounting boards into place (the xovers will be screwed into these, I didn't want to attach the xovers directly to the cabinet using screws)

The 5lb weght is sitting on top of a 10lb weight to apply pressure as the glue dries on the HF board, meanwhile I clamped the LF board to the side.



JCD said:


> Just one thing, take lots of pictures.. people like me live for this kind of stuff!


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## xyrium (Jul 28, 2008)

Slight setback. I just attempted to mount the back plates and binding posts and discovered that the Premium Binding Posts that PE sells, do NOT fit all of the way through their cabinets. This is my fault for assuming that they did. However, I went back to their site and only located two pairs that actually do. This means that about 80% of the posts that they sell will not penetrate the thickness of their prefab cabs. Anyway, so, I'm stuck with a lower grade pair that I just ordered, which have 1.5" posts.

The thing that really peeves me here, is that I tried to fix it by recessing the interior holes with a set of Speedbor space bit, while not realizing that I wouldn't land perfectly flat with them. The end result, 2 sets of binding posts mounted, and pointing in slightly different directions. Sigh...

So, now I will need to install the aluminium mounting plates on the interior of the cabinet, as well as the exterior, just to ensure that the posts mount on 90 degree angles. I just have to figure out what to fill the recesses with now. Maybe hot glue, maybe wood putty....

Final gripe, the PE binding posts mounting plates don't use color coded screws. So, even though the plates themselves have a very nice silver matte finish, the mounting screws that come with them are run of the mill cheap steel pieces, so they don't match the finish of the plates... Come on PE!!!


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## 1Michael (Nov 2, 2006)

I'm not sure why you cut those additional holes in the brace. This is a sealed box right? If so there is no breathing in a sealed box. The air gets compressed then expands so the air stays in the same place. Now if this was ported, there is air "moving" around the box, and in and out of the box...No big deal, I just like as much material in the bracing as possible.


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## evilskillit (Oct 7, 2008)

FWIW when it comes to binding posts I pretty much only use these.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=091-1245

They're affordable. They're not in a terminal cup so you can put them more than 0.005 inches apart and actually get your fingers on them, which I love. They look ok, they go through 3/4" material and you can really get a grip on them with your bare fingers. They don't look super high end but I like them so much I can't imagine using anything else, even if all the other speaker parts were thousands of dollars. But thats just me.

Bummer about your problems tho. You could always put some tape on the outside, refill the holes with bondo from the inside then redrill them perfectly straight. The plate would cover any of the bondo that would otherwise show. Or you could just live with it if you don't care that much. Just trying to give some useful help.


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## xyrium (Jul 28, 2008)

Hi Michael,

I'm quite a bit short on theory, but applied the following logic. The woofer is going to be producing a tremendous amount of frequencies. The velocity from the inverse movement of it's cone is going to create quite a bit of pressure, and I didn't want that pressure reflected by a surface too early in the process.

I realize that it may not make much of a difference. So, I figured it probably couldn't hurt either. Where were you when I was asking about this?!?! :neener:

Rgds,
Paul



buggers said:


> I'm not sure why you cut those additional holes in the brace. This is a sealed box right? If so there is no breathing in a sealed box. The air gets compressed then expands so the air stays in the same place. Now if this was ported, there is air "moving" around the box, and in and out of the box...No big deal, I just like as much material in the bracing as possible.


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## xyrium (Jul 28, 2008)

Thanks Matt. I used those on my L15 build actually. They are good posts. Well, I ended up ordering these, only slightly different:

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=091-340

In the end, I save about $35.00 by exchanging the Premiums for these. 

I'll keep the plate on the cabinet, but just add another to the inside for flat mounting of the new posts. I'll add it to both of them, even though I only massacred one. Just to keep them consistent. I'll toss a few vinyl damping strips on them to prevent any ringing. It's just annoying I suppose. 

On the flip side, I love the satin nickel plates, even with the gold binding posts (just trying to keep like metals in the signal path (gold plated bananas going into gold plated binding posts). I know, silly at best, but...





evilskillit said:


> FWIW when it comes to binding posts I pretty much only use these.
> 
> http://www.parts-express.com/pe/showdetl.cfm?Partnumber=091-1245
> 
> ...


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## evilskillit (Oct 7, 2008)

Those look pretty good too. I passed them up previously because at a glance they look like spring loaded binding posts, which I do not like at all. But that does not seem to be the case, maybe I'll try them next time.


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## xyrium (Jul 28, 2008)

I'm an idiot (no confirmations necessary please ). I'll just speedbor all the way through the cabinet and attach the binding posts directly to the plate. Will keep you folks posted!


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## evilskillit (Oct 7, 2008)

I suppose that would work, eh? I didn't think of it either.


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## 1Michael (Nov 2, 2006)

Ah I see, what you were concerned about was the reflected sound energy inside the box. For that you will need to put some sort of sound absorbing material like foam, or if you have money, something like whisper mat, or if you are poor like me insulation from Lowes. Also you will need to glue the baffle on once you have everything set up like you want, because these PE boxes do tend to leak air when playing bass type stuff. Some people fill the box with pillow stuffing...I do not. You can try it and its not a lot of cash to spend for experimenting.


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## xyrium (Jul 28, 2008)

Thanks guys. Yes, I have the foam from PE. It's about an inch/25mm thick. I plan to use that on the sides and top and then 2" fiberglass on the back and bottom. From what I've heard, fiberglass is much better at sound absorption than foam (studiotips.org, etc.). So, broke or not, you're probably using the better material anyway. 

So here we are. Being that I love both the binding posts, and the plates, there's on thing to note. Since the plates are aluminum, you need to ensure that you install the nylon washers that come with the binding posts on each side. Otherwise,you'll be blowing amp fuses all day... A few photos.

So, what do you think, fill ths holes with hot glue now?


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## xyrium (Jul 28, 2008)

Ok, I'll post some images to my yahoo account soon. However, if you recall from another thread (might even be this one) I changed the inductor on the woofer from the 2.7 to the 2.0mH inductor that Zaph tested for nearfield use. In my opinion, with the 2.0 in place, the mids are too far forward at a 4ft listening distance. I was considering the 2.5 value, but I may just go with the 2.7 in the original design. They are still breaking in, but in my experience, they won't change that much. I'll post REW results sometime later this week. Please remember, this is my opinion, in my listening room, and does not express or claim a fault of the design. It may also just be tweeter padding. The REW results will probably paint a much better picture of what I'm hearing and how to make it suit my preferences, but it sounds like it's in the 2kHz region.

Otherwise, they do a nice job on both acoustic and electric bass. Guitars are a bit bright, but I think that may be attibuted to the aforementioned adjustments. Female vocals are astonishing. Holly Cole, Alison Krauss, etc. They're here in the room. Very well executed for a setup that is also producing the kick drum very well with excellent delineation. The initial attack is there, while the thump of the resonating sound inside the drum is well represented.


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## 1Michael (Nov 2, 2006)

I don't know about that tweeter but that mid bass driver does need a bit of break in, in my experience...


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## zero the hero (Feb 24, 2008)

so did you end up leaving driver placement as intended? I'm a bit surprised by the suggestions tin this thread to move drivers around. These were designed with specific baffle placements; any alterations would have affected diffraction and consequensly response. Maybe not by much, but it doesn't take much to notice a change in sensitive frequencies.


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## xyrium (Jul 28, 2008)

Hey guys,

Thanks Michael. I've got mine playing music all night while I'm sleeping, and all day while at work. .I hope to do a frequency sweep on REW this weekend, hoping they'll be fairly broken in by then.

Kevin, yes, everything is as per Zaph's design suggestions. Th baffle is also still the same width, and drivers in the same exact alignment on the baffle. 1/2" roundover behind the woofer as well. Keep in mind, I'm not complaining, just providing a quick eval of what I'm hearing, in my listening room. Everyone's results will vary because no two rooms, or ears, are the same, in addition to have different preferences. I'm quite happy with the sound, and I could probably EQ any anomalies out rather easily using the parametric EQ built into my 1616M. So, these are just initial listening impressions, and thus far, I'm pretty happy. These are indeed, very revealing drivers.


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## evilskillit (Oct 7, 2008)

Glad to hear you got em built and are pretty happy initially. Cant wait to see how you feel about them after living with them a few days and making any final adjustments.


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## xyrium (Jul 28, 2008)

Hey Matt! Thanks. Yes, these drivers are rather impressive. Like any speaker, I'll need to EQ 'em to suit my needs. However, they are impressively revealing right out of the box!


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## xyrium (Jul 28, 2008)

Ok, so here we go. Some graphs from REW. Quite ugly, and this is WITH room treatment via OC703 panels. I think they may do more harm than good.

There's some funky dips in the lows around 150, and you can see the 5-6dB rise above 2k. So, I may go with the original inductor value on the woofer to see what that does, as well as add a 9Ohm resistor to the tweeter pad to bring things down a bit.

This explains the seemingly holographic imaging (the highs being increased). Though the holes in the low freq region seem odd.


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## xyrium (Jul 28, 2008)

Initially, I thought one driver was faulty. It turns out that the room actually impacted the measurements. Here are individual woofer measurements. As you can see, there's a dip on one side, and a significant increase o nthe other below 80Hz. Odd. I originally posted a graph that appeared to indicate one woofer was completely defective. However, it turns out that the mixer was unbalanced in one channel.


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## evilskillit (Oct 7, 2008)

Wow, yeah I'd say you eliminated all posabilities other than the woofer it's self by swapping woofers into cabinets. Good ear. Well if they sounded good with one woofer obviously being kind of messed up think how great they'll sound with 2 good woofers. Tho that is a bummer that you're going to have to deal with RMAing the thing. At least it shouldn't cost you anything other than shipping.

Makes me wish that I had the time to quickly measure every driver before I used it to make sure its right, because something like that could go unnoticed, well forever really and you wouldn't know what was nagging at you. Well good luck getting it fixed and let us know how they sound then 

Oh and on another positive note man the good woofer sure is flat! That is pretty impressive.


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## xyrium (Jul 28, 2008)

Hi Matt, this was a mistake on my part. I ended up swapping cables throughout the ssystem, and retesting. Though there was a difference between outputs, it wasn't as dramatic as previously posted. , I wish I could remove the post.  I'll post updated results of each speaker. It's actually good, and interesting.

Furthermore, here's a combined shot from 50-10k, then just 30-200. As you can see, the woofers seem to diev around 50. However, they play 20-30Hz rather well. Th problem with this, is that one would easily overload these drivers if they didn't cross them over and allowed them to play at those frequencies. I believe John mentions this in his power recommendations for this design, and it is apparently true that they can go that low, but only with decreased power being fed to them. This said, I would probably use a crossover at 50Hz if you're using these w/o a sub. The graph from 2k to 10k shows the tweeters' operating area, and though measured individually then combined in one graph, you can see that they bboth rise heading up to 10k. I'll probably pad them with a 9 Ohm resistor and remeasure.


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## zero the hero (Feb 24, 2008)

are speakers facing straight ahead or toed in? Dip at 150 is floor bounce; nothing you can do about that. Response looks pretty good to me for in-room.


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## xyrium (Jul 28, 2008)

Hey Kevin, this is with the Mic about 6" from the dome and dustcaps. So, from 40 up, that's 6" from the woofer dust cap, and from the 2k and up graph, it's 6" from the dome of the tweeter. I should have mentioned how it was being measured. That would need to be some impressive floor bounce to impact such close proximity measurements. 

I'll some full range measurements (the RS meter is useless above 8k though) from about 6 feet out so you can begin to see the how they sound as the combine.


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## evilskillit (Oct 7, 2008)

Sure you can, with a reciprocating saw. The wife might not like it tho. :bigsmile:



zero the hero said:


> are speakers facing straight ahead or toed in? Dip at 150 is floor bounce; nothing you can do about that. Response looks pretty good to me for in-room.


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## zero the hero (Feb 24, 2008)

xyrium said:


> Hey Kevin, this is with the Mic about 6" from the dome and dustcaps. So, from 40 up, that's 6" from the woofer dust cap, and from the 2k and up graph, it's 6" from the dome of the tweeter. I should have mentioned how it was being measured. That would need to be some impressive floor bounce to impact such close proximity measurements.
> 
> I'll some full range measurements (the RS meter is useless above 8k though) from about 6 feet out so you can begin to see the how they sound as the combine.




haha ok... my bad, thought they were in room measurements of the pair


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## xyrium (Jul 28, 2008)

Sorry, that was my fault Kevin, for not specifying. So, here's the final result using a 9 Ohm (stock is 6) tweeter pad in the high pass, and the stock 2.7 mH inductor in the low.

Baffles aren't glued on, but they are nice and snug, so it's a fairly leaky sealed design at the moment. I'll take another run once the glue sets. The mic is 1M or about 3.3 feet our from the center of the speakers, mounted between the height of the woofer and tweeter.

I have to admit, the dip below 100Hz bothers me...


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