Dual Eminence Delta-10B with a DE250 or D220Ti? - AVS Forum
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post #1 of 82 Old 08-21-2012, 07:48 AM - Thread Starter
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I have the itch to build something again, and this time I want to replace my Definitive BP10B mains and CLR2000 center. The bass department is good to go, so these only need to handle 80hz and up. The Definitives do ok for music, but due to the distance of the primary LP to the mains, about 13ft, the dynamics for HT are tamed down. These are also a bi-polar design, and directly behind the speakers are OC 703 corner bass traps, so that design for my room is kind of pointless.

To start, I’ve been really impressed from what I’ve read about the SHO-10 and ED Cinema 12 speakers, and from a materials perspective they are definitely within my budget. From a driver perspective I want to keep this around $250 per speaker.

For the crossover, I was thinking about going the active route with a DCX2496 since I have no clue how to build a crossover, and that’d also take care of the EQ’ing. I would have to bi-amp, which is fine since I already have the amps.

At the moment I’m thinking about dual Eminence Delta-10B midrange drivers (wired in parallel for 8ohm) with either a B&C DE250 or Selenium D220Ti. These seem to be pretty common in the DIY world.

Since I’m a complete noob I’ll need some help with what horn to use and the box dimensions. You guys do crazy stuff with those graphs, and most of it is beyond me. If someone has already done a build similar, please point me to the thread!

Input is always appreciated, even if I’m being told I’m an idiot, so fire away!
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post #2 of 82 Old 08-23-2012, 09:30 AM - Thread Starter
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Question for you guys:

Since I’m most likely going to cross these over at 80hz on my preamp, should I tune the box for 80hz, or shoot a little lower closer to 70hz?

At the moment I’m thinking 1.2 cu.ft for the internal volume, and doubling up ¾” MDF on all sides for 1.5” walls all around. I’m not spending tons of cash on BB plywood this time around like I did for my subs…
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post #3 of 82 Old 08-23-2012, 10:00 AM
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Cool stuff. I happen to be working on a Delta 10a design with the DE250 and DE10 (going to try both and use which ever works best). Using the SEOS12 waveguide. Check it out.

IMG_2719.jpg

I have it sealed right now, but plan to tune it right around 70hz. It's just a test box, nothing fancy. I'd tune it lower than 80hz so that the roll off is smoother and phase rotation is below the xo point.

I plan to do an active version. It would likely work ok with the 10B if you just offset the tweeter level by 3db. No gaurantees though. I plan to have measurements done this weekend and an active simulation done early next week. Listening to it middle of next week biggrin.gif

How are you doing your driver layout? Side by side woofers? MTM, TMM?

Good luck.
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post #4 of 82 Old 08-23-2012, 11:49 AM - Thread Starter
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Those were my thoughts for the tuning as well, mostly because of the phase rotation. Looking at graphs, 70hz or 80hz doesn't appear to be that dramatic of a change.

For the L/R mains I'm thinking TMM, and for the center since I'd want to lay it horizontally, I'm thinking MTM.

It looks like a 9" wide, 1" tall, and 1.5" deep port would get me around 71-72hz, which is perfect considering the front baffle will be 1.5" thick anyway!

It appears the outside dimensions of the boxes are going to be 13" wide, 32" tall, and 10.5" deep.

Since all 6 side will be 1.5" MDF, will I need any bracing?
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post #5 of 82 Old 08-23-2012, 12:50 PM
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I'd still use bracing. I'd also reconsider an MTM on its side for the center. One thing you speakers won't have is good vertical consistency.
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post #6 of 82 Old 08-23-2012, 02:04 PM - Thread Starter
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Quote:
Originally Posted by tuxedocivic View Post

I'd still use bracing. I'd also reconsider an MTM on its side for the center. One thing you speakers won't have is good vertical consistency.

Bracing, check.

The problem is that my LDC TV is going to have to sit on top of this center, as my current layout won't allow for a tower speaker as a center channel.

Right now my current MTM center, a CLR2000, is laying horizontally. Are you saying it would sound better positioned vertically?
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post #7 of 82 Old 08-23-2012, 02:23 PM
 
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Luke, I'd look into the DNA-360 / SEOS12 combo. Not too much more than the D220Ti but performance should be like the DE250 as I understand it.
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post #8 of 82 Old 08-23-2012, 03:57 PM
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Ya, it'll have some really bad off axis sound laying horizontal because of the driver spacing. Could you go with a single 10a on the center? Still not ideal, but better.
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post #9 of 82 Old 08-23-2012, 04:13 PM - Thread Starter
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Quote:
Originally Posted by Aknot5 View Post

Luke, I'd look into the DNA-360 / SEOS12 combo. Not too much more than the D220Ti but performance should be like the DE250 as I understand it.

I like what I'm reading about that combo. If I go that route I'll have to make the box a little wider since the SEOS-12 is 13.2" wide.
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post #10 of 82 Old 08-23-2012, 08:57 PM
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The enclosure would need to be about 14.25" - 14.5" wide. But you really don't need those to be 1.5" thick all around. There was a bracing thread here a couple years ago with some engineers joining into the discussion. Turns out that thinner walls and bracing will hands down beat thicker walls and no bracing.
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post #11 of 82 Old 08-23-2012, 09:28 PM - Thread Starter
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Quote:
Originally Posted by Erich H View Post

The enclosure would need to be about 14.25" - 14.5" wide. But you really don't need those to be 1.5" thick all around. There was a bracing thread here a couple years ago with some engineers joining into the discussion. Turns out that thinner walls and bracing will hands down beat thicker walls and no bracing.

I think 14.5" wide would be the way to go.

Maybe I'll only make the front baffle, top, and bottom 1.5" thick and add some bracing. It would be a lot easier!
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post #12 of 82 Old 08-23-2012, 09:31 PM - Thread Starter
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in WinISD I've been messing around with two different options:

1. A 1.2 cu.ft volume box tuned to 70hz

or

2. A 2 cu.ft volume box tuned to 60hz

The 2 cu.ft volume option would actually be tall enough that the waveguide would be at ear level when sitting down. I wouldn't have to build stands for them since they'd be around 40" tall...

Any opinions on that?
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post #13 of 82 Old 08-24-2012, 06:28 AM - Thread Starter
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Quote:
Originally Posted by tuxedocivic View Post

Ya, it'll have some really bad off axis sound laying horizontal because of the driver spacing. Could you go with a single 10a on the center? Still not ideal, but better.

What if I did the woofers side by side with the horn up top for the center?
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post #14 of 82 Old 08-24-2012, 06:48 AM
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Better. It'll be tall, but sonically that's gotta be better.
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post #15 of 82 Old 08-26-2012, 03:25 PM - Thread Starter
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Here's what I'm leaning towards at the moment::

DNA-360/SEOS12
Dual Delta 10B
2 cu.ft box tuned to 70hz (much flatter response than a 60hz tune)

TMM configuration with all the drivers as close as possible, and the slot port at the bottom below the two woofers.

Outside dimensions of the box: 40" tall, 14.5" wide, and 9.75" deep (Top, bottom, and baffle will be 1.5". Material will be MDF.

The DCX2496 I already have will be the crossover and EQ, and I'll bi-amp. The amp running the woofers is 200x2 RMS at 8ohm, and the amp driving the tweeters is 100x2 RMS at 8ohm, so I won't have to worry about over driving these.

Thoughts anyone? I'm anxious to get started!
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post #16 of 82 Old 08-26-2012, 06:26 PM
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May need a 2.5 way crossover

JSS
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post #17 of 82 Old 08-26-2012, 06:45 PM
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If you haven't purchased the parts yet, why not just the delta10a? I did my outdoor measurements on it yesterday and it can crank. 95db/2.83v/m at the bottom of the baffle step region. That's quite good. No doubt two is better than one, but you wouldn't have the CTC issues.

How are you going to design the cross over? Just an FYI you may already know, but active cross overs require tuning as well. You can't just plug in 48db/oct at 1500hz.
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post #18 of 82 Old 08-26-2012, 07:09 PM - Thread Starter
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Quote:
Originally Posted by tuxedocivic View Post

If you haven't purchased the parts yet, why not just the delta10a? I did my outdoor measurements on it yesterday and it can crank. 95db/2.83v/m at the bottom of the baffle step region. That's quite good. No doubt two is better than one, but you wouldn't have the CTC issues.
How are you going to design the cross over? Just an FYI you may already know, but active cross overs require tuning as well. You can't just plug in 48db/oct at 1500hz.

These won't have grills, and two looks better than one=) Another added bonus is the increased sensativity.

CTC issues? What's that?

I don't plan on having any passive crossovers, and I know the DCX will take time to get just right, but that's part of the fun.
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post #19 of 82 Old 08-26-2012, 07:58 PM
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CTC = Center to center of the drivers used at crossover frequency.

A larger center to center distance makes for a smaller forward lobe for a given frequency. Using two woofers vertically increases you CTC distance as the acoustic center for the woofers is moved down between the two. As maxmercy pointed out a 2.5 way may be need as it would alleviate that problem.
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post #20 of 82 Old 08-26-2012, 08:05 PM - Thread Starter
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Quote:
Originally Posted by mtg90 View Post

CTC = Center to center of the drivers used at crossover frequency.
A larger center to center distance makes for a smaller forward lobe for a given frequency. Using two woofers vertically increases you CTC distance as the acoustic center for the woofers is moved down between the two. As maxmercy pointed out a 2.5 way may be need as it would alleviate that problem.

Dude, you're speaking another language. Forward lobe? LOL

Please, dumb it down for me. How does this problem manifest itself in the sound of the speaker?
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post #21 of 82 Old 08-26-2012, 08:28 PM
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Quote:
Originally Posted by lukeamdman View Post

Dude, you're speaking another language. Forward lobe? LOL
Please, dumb it down for me. How does this problem manifest itself in the sound of the speaker?
Speakers are designed to work best when you are pretty much the same distance from the tweeter and midrange/midwoofer at all times. That's why most speakers have the drivers pushed close together, so when you stand up or slouch down you're only a tiny bit closer to one driver or the other, not enough to make a huge difference. By having dual woofers, both playing the same signal, one of them is going to be down near the floor and a good couple of feet from the tweeter (measured from the center of both drivers). This will be a lot harder to make work well, because depending on how you sit your ears will be relatively a lot closer or further away from the bottom woofer.

The "forward lobe" is the range of up-and-down positions where it sounds right. A pair of drivers close together = big forward lobe, it sounds the same over a large vertical span. Extra drivers spread out further and playing the same signal = small forward lobe, meaning it will probably only sound right in one teeny little spot.
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post #22 of 82 Old 08-26-2012, 08:53 PM - Thread Starter
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Quote:
Originally Posted by antisuck View Post

Speakers are designed to work best when you are pretty much the same distance from the tweeter and midrange/midwoofer at all times. That's why most speakers have the drivers pushed close together, so when you stand up or slouch down you're only a tiny bit closer to one driver or the other, not enough to make a huge difference. By having dual woofers, both playing the same signal, one of them is going to be down near the floor and a good couple of feet from the tweeter (measured from the center of both drivers). This will be a lot harder to make work well, because depending on how you sit your ears will be relatively a lot closer or further away from the bottom woofer.
The "forward lobe" is the range of up-and-down positions where it sounds right. A pair of drivers close together = big forward lobe, it sounds the same over a large vertical span. Extra drivers spread out further and playing the same signal = small forward lobe, meaning it will probably only sound right in one teeny little spot.

Excellent, that makes perfect sense.

If I'm understanding this correctly, the easiest way to fix this would be a MTM where the horn is ear level when sitting?
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post #23 of 82 Old 08-26-2012, 09:02 PM
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As you move off axis you move further away from one driver then the other, in other words the distance between you and each of the drivers is no longer equal.

Now when the driver are close together (small CTC) the change in distance is less then if the drivers are further apart. At an extreme picture being 90 degrees above or below the speaker and measuring your distance to each driver.

That change in distance as you move off axis creates problems, the sound from one of those drivers now reaches you before the other. Imagine the sound from the two drivers at the crossover frequncy being two sinewaves perfectly in sync (in phase) while you sit on axis, as you start to move off axis the sine wave of one starts to move ahead of the other and they are no longer in sync (phase). When they start to move out of phase they no longer sum perfectly, 90 degrees out of phase they don't sum at all, more then 90 and they start to cancel each other. Move far enough off axis and the sine waves will reach a point where they are completely out of phase (180 degrees) and you get a complete cancellation at that point.

That all relates back to your distances between the drivers and your crossover frequency. If your drivers CTC distance is 1/2 the wavelength of your crossover frequency you will see the cancelation 90 degrees off axis above and below. The futher apart the CTC distance the narrower that window (forward lobe) becomes, smaller CTC wider lobe. It is very hard to get a CTC distance of 1/2 crossover frequency wavelength, its only like 6.8" at 1000hz so you can see how this becomes a problem.

As an example here is what happens to the frequency response when moving off axis (this is 0 to 20 degress below on my MTG-08):


0-30 above:


Edit: The MTM still causes problems becuase the woofers/mids will cancel with themselves at the crossover frequency as you move off axis before they cancel with the tweeter since they now have the furthest CTC distance.
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post #24 of 82 Old 08-26-2012, 09:05 PM
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Am MTM will still have a small vertical listening window. if you target a very low xo point that'll help.

I know you're going active, but tweaking an active xo rarely gives an optimum result. I'll let you know my do settings in a few days. Oh shoot, that won't work. I'm using the De10 first. Ok if you're still working on this in a month I'll post my settings with the DNA-360. Hopefully it'll help you land on a useful do for yours.
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post #25 of 82 Old 08-26-2012, 09:17 PM
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Quote:
Originally Posted by lukeamdman View Post

Excellent, that makes perfect sense.
If I'm understanding this correctly, the easiest way to fix this would be a MTM where the horn is ear level when sitting?
Better might be a 2.5 way, as maxmercy mentioned. That's where you add extra crossover bits to the bottom woofer so it only covers the bass, not any of the midrange that the upper woofer is covering. In the bass frequencies we have a lot more flexibility as to how far apart the drivers are (has to do with wavelengths of sound etc).

Listen to these other guys though, they have a lot more experience than I do in these things. I just jumped in to help get past that one bump. I see mtg90 already added an informative post that explains things much more precisely than I did.
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post #26 of 82 Old 08-27-2012, 06:31 AM - Thread Starter
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Quote:
Originally Posted by mtg90 View Post

As you move off axis you move further away from one driver then the other, in other words the distance between you and each of the drivers is no longer equal.
Now when the driver are close together (small CTC) the change in distance is less then if the drivers are further apart. At an extreme picture being 90 degrees above or below the speaker and measuring your distance to each driver.
That change in distance as you move off axis creates problems, the sound from one of those drivers now reaches you before the other. Imagine the sound from the two drivers at the crossover frequncy being two sinewaves perfectly in sync (in phase) while you sit on axis, as you start to move off axis the sine wave of one starts to move ahead of the other and they are no longer in sync (phase). When they start to move out of phase they no longer sum perfectly, 90 degrees out of phase they don't sum at all, more then 90 and they start to cancel each other. Move far enough off axis and the sine waves will reach a point where they are completely out of phase (180 degrees) and you get a complete cancellation at that point.
That all relates back to your distances between the drivers and your crossover frequency. If your drivers CTC distance is 1/2 the wavelength of your crossover frequency you will see the cancelation 90 degrees off axis above and below. The futher apart the CTC distance the narrower that window (forward lobe) becomes, smaller CTC wider lobe. It is very hard to get a CTC distance of 1/2 crossover frequency wavelength, its only like 6.8" at 1000hz so you can see how this becomes a problem.
As an example here is what happens to the frequency response when moving off axis (this is 0 to 20 degress below on my MTG-08):

0-30 above:

Edit: The MTM still causes problems becuase the woofers/mids will cancel with themselves at the crossover frequency as you move off axis before they cancel with the tweeter since they now have the furthest CTC distance.

So if I do a TMM, I should add a passive XO to the lower woofer, and looking at your graph, that will be somewhere in the 800-1000hz range?

What is the "better" configuration, TMM or MTM?

EDIT: On second thought, you're saying a MTM won't work because it's the crossover point with the tweeter that's the issue. Nevermind!
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post #27 of 82 Old 08-27-2012, 07:28 AM - Thread Starter
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So I'm just curious when looking at alot of MTM designs like JTR, Seaton, Dynaudio, Definitive, etc.

It appears to me that a MTM would be best since I'm only concerned with how these sound when I'm sitting down. Since I can build the stand height to make the tweeter ear level when sitting, both woofers would be equal distance from my ear when sitting. I'm not really concerned with how they sound when I'm standing.

Where am I going wrong with this assumption? Help a noob out =)
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post #28 of 82 Old 08-27-2012, 08:08 AM
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If you plan on listening to them while seated or in a narrow window then there is nothing wrong going with a two way MTM.

On a side note JTR and Seaton both use a coaxial driver for mid/high so the crossover frequency of the mid/woofers is down far enough not to cause lobing issues.
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post #29 of 82 Old 08-27-2012, 09:02 AM - Thread Starter
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Does moving off axis have a greater affect on higher frequencies vs lower frequencies?
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post #30 of 82 Old 08-27-2012, 09:45 AM
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Not sure which answer to give, that question is many in itself, I'll try to answer the one I think your asking.

The lobing effect will only happen around the crossover frequency where two or more point sources are playing the same signal. Any off axis change in high or low freqencies out of that range will be dictated by the dispersion of those individual drivers.

At lower freqencies (like around those used for the mid/woofer crossover in JTR's/Seaton's designs) the wavelengths are much longer and drivers can be spaced further apart without lobing becoming an issue. (I think this is what you were asking.)

Just to throw this in as well, the different woofer orientations only make a difference in the vertical axis, on the horizontal axis there is little to no change. But this is only true if talking about different vertical woofer orientations, put them side by side and you make changes oin the horizontal axis.
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