Can you say, inexpensive Mission Accomplished dipole?

[JonMarsh]

That won't accurately show the dipole roll off or the peaking in response due to the front to rear baffle distance.

[RonS]

Measuring Dipole Baffles

http://www.musicanddesign.com/measure_dipole.html

Works very well

[Mazeroth]

I forgot about that site, Ron. Thanks!

A little update. I had planned on having the prototype running by tonight hooked up to the DCX2496 when my wife came out in the garage and said her best friend and her husband were coming over! I was just starting to route out the second RS180 hole when the news came. :cry: Oh well, to tease myself a little bit I placed the RS180s in their holes and put the RS28 (probably 27TDFC in final version) on the baffle, along with two old MTX 12" subs to show what the design is going to look like. Pretty similar to the Arvo but it will be a little bit different. Hopefully, weather permitting, I'll have this baby singing to me tomorrow night!

Image not available

[clearwaterms]

are the sub woofers going to be sealed? or some kind of H / W baffle?

[cjd]

eww, destroy good sound with funky baffle shapes or worse, monopole?!

C

[clearwaterms]

eww, destroy good sound with funky baffle shapes or worse, monopole?!

C

i assume your talking to me...

could you please elaborate?

[cjd]

It's been covered elsewhere on this forum in more detail if you're really curious. Simply: H/W baffles are compromises And switching to monopole in the middle of a core critical frequency range is, well... it's not a very good choice. Many people do anyhow. But you're splitting instruments down the middle as well as the human voice.

I honestly am not sure what choices they're going to be making for this project.

C

[clearwaterms]

It's been covered elsewhere on this forum in more detail if you're really curious. Simply: H/W baffles are compromises And switching to monopole in the middle of a core critical frequency range is, well... it's not a very good choice. Many people do anyhow. But you're splitting instruments down the middle as well as the human voice.

I honestly am not sure what choices they're going to be making for this project.

C

so by monopole you mean forward firing sealed enclosure? I have read threads where people put subwoofers on baffles and have dipole base and people seem to really like it, but the total available SPL was low compared to a sealed enclosure

[Mazeroth]

are the sub woofers going to be sealed? or some kind of H / W baffle?

I'm avoiding H and W frames due to their limited upper frequency limits. This design is going to use a small U-frame which will allow the subs to cross in the 125-175 region (maybe a bit higher, we'll see) and will also provide a little bit more output than a flat baffle does. If this weren't a budget project I would have went with subs that have twice the xmax (or more) and would have eliminated the U-frame to get the best possible sound.

[cjd]

so by monopole you mean forward firing sealed enclosure? I have read threads where people put subwoofers on baffles and have dipole base and people seem to really like it, but the total available SPL was low compared to a sealed enclosure

Yeah, below a certain point a monopole transition is far less critical - say, 40 or 50Hz. A sealed enclosure would surely be monopole, but so would bandpass, transmission-line, horn... dipole and bipole are not monopole.

They're covering pretty high in the frequency range on the "subs" in this case.

C

[augerpro]

If a person were to make these two subs sidefiring so you wouldn't have a monstrous front baffle, how high could you cross them before directivity or phase (or anything else) causes a problem? I've never been clear on how well sidefiring woofers integrate with the mids. I guess this could apply to sidefiring on a monopole speaker also.

[cjd]

Have you looked at dipole radiation patterns?

[augerpro]

Have you looked at dipole radiation patterns?

Err, nope. Just started reading about dipoles seriously last night. But now that you say that I suppose they cancel at 90 degrees so sidefiring would be the last thing you would want to do. Sorry for the dumb question ops:

Although I am still curious about sidefiring for monpoles and what the concerns are. If anyone knows please PM me so we don't derail this thread.

[Mazeroth]

Good news and bad news

Well, I received the four Elemental Designs 12 inch subs yesterday and didn't get to test any until early this morning before I went to work. I finished cutting the baffles and should have them assembled after I get home.

First thing, these subs look great for $25. Thick poly cone, flat poly dust cap, rubber surround and a pretty nice magnet size for a driver of this price. I'm not a big fan of the gaskets some subs have on them on the front of the driver and this sub has one. However, it's probably half the size of the gaskets that are on my Shivas so that's another plus. :T

Now, on to the bad. The first sub I took out and hooked up sounded good open air (with a little bit of noise prone to most budget subs) until I hit about 50% xmax. Then I started to hear a clack-clack sound near where the cone meets the spider. I drove it near xmax and it continued, obviously. Do you think this is a misaligned voice coil? I've never experienced this before so I don't know what exactly it is. When I contact ED I want to be as specific as possible so if anyone could point out what they think it is that would be great.

After that I was pretty worried that I just spent $118 on junk but I pulled another one out of the box and it sounds great! I ran it near full xmax for a few minutes with no sign clacking (is that even a word?!) and a sigh of relief went through my body. I didn't have time to test any more as I was already running late for work but I'll be testing them other two as soon as I get home. I also snapped a few pics of the drivers that I'll post when I get home so you can see what they look like.

Thanks.

[Mazeroth]

Test dipole completed!

I got the test enclosure built and the drivers installed last night. After wiring them up to my DCX2496 I must say I'm quite impressed with what I'm hearing! The bass is the cleanest I've heard in my house and digs a lot deeper than I had anticipated. With the speaker almost 3 meters from my listening position I was getting usable output down to 25hz. I put in a shelving filter that added 6db of boost up to 40hz and tailed off at 6db/ocatave which really helped things out. I still haven't done any measurements and was doing all the adjusting by ear with the DCX2496. This weekend I will get my computer ready in the basement with all my measurement software/hardware and go to town on this guy. I'm also going to experiment with adding a 1x2x48 on the sides to add a little bit of stiffness to the upper baffle, and will experiment with other sizes as well. I'm in no rush to get this done and will probably tweak it to death over the next 4-6 weeks until I don't think I can get it sounding any better without using over $200 in crossover parts.

The only downfall I've noticed thus far is the energy being transferred to the baffle from the subs. I want this project to be easy to build and really didn't want to use a super thick baffle but if you guys think a 1 1/8 to a 1.5" thick baffle will reduce the energy in the baffle I'll give it a shot. Also, what do you think of the dimensions I chose for the U-baffle? As of now the open part in the back is 28h x 12.5w x 8d. I can't hear any sound coloration using the U-baffle compared to a flat baffle, however, I've only been crossing over at 100-150 hz.

Here's a quick pic I snapped about an hour ago of what it looks like. I only used scrap wood so forgive the poor woodworking. Also, my basement audio room is usually immaculate but with this project I've created quite a mess! I also need to get those OC 703 panels I made hung up :B

Image not available

[JonMarsh]

This is pretty similar to the "Gen I" Arvo Part, but that had thick panels and reinforced edges- and just 10" (well, almost 11") woofers- the more woofer mass, the more reaction vibration you're likely to have.



So, IMO, thick panels and mass are a good and necessary evil, er, uh, technique.

Regarding your earlier post, it sounds like you have a VC misalignment OR driver leads slapping on the cone. Best construction for truly long throw drivers is tinsel leads woven into the spider.

Crossing low on the mid to woofer range will avoid the problem areas from a U baffle; you just need more cone area for the midrange, which can sometimes lead to other effects you may not want, but can deal with. With two midranges, plan on a low crossover with steep slopes to the tweeter, like the Gen 1 and Gen 2 Arvo.

But above all, have fun! Looks like you're well on the way to that!

~Jon

[JonMarsh]

EDGE examples

Per our other PM exchange, here's the EDGE plots with the current baffle shape and driver positioning I've worked out, just for reference to give you an idea of what I've been working towards.


Graph of the predicted baffle affect on woofer response




Graph of the predicted baffle affect on midrange driver resopnse







Graph of the predicted baffle effect at waveguide location





Targeted crossover frequencies are 350 Hz, probably with LR6 and 1.8 kHz with CE LR8.

[augerpro]

Jon I modeled somewhat similar results for the OB in my thread. My question is considering the normal XO area for the mid/woofer, how much of a problem have you found the hump centered at 400-500Hz when designing the XO? On my Bose buster MTM's I had a hump 4k and it caused me nothing but grief when designing the 3k Hz XO. Any tips you can share?

[JonMarsh]

You have to take into account the shape and nature of the "hump" and how it can be factored into the net crossover design.

For example, on the mid, the hump at ~ 300 Hz is a gentle slope on either side, and it can be sloped down easily with a zero in the response (high pass) and using the roll off below as part of the acoustical transfer function (for the midrange).

The woofer 225 to 500 Hz response is almost within a 1 dB window (this is really pretty flat), and is easy to compensate in the woofer roll off through adjusting the LP values and conjugate zobel network. The response will roll faster above 500 Hz for a while, but you just have to put a zero in one of the poles (a resistor in series with shunt cap) to get that to conform to a tranfer function.

These plots may look more problematic than they are; they're plotted at 1 dB/division, not the 5 dB or 10 dB you often see on driver plots! Of course, the actual driver response is just modified by these plots, but these took a bit of work, and are much easier to work with than say, the 1st Gen Arvo results.

Your hump at 4K may be a function of diffraction from the baffle size; that's in the frequency range where heavy felt diffraction treatments are very useful.

[SQdude]

Mazeroth,

Any updates on this design? Is it fully complete? What are the final XO settings?

[Mazeroth]

Of course there's an update, I haven't done anything to them...yet!

Right when I stopped posting on this is when my wife and I decided to redo the theater room in the basement. New ceiling, new paint, new projector, new DIY 100" screen, new wiring etc. I also just got back from Colorado and have also been playing and practicing a ton of golf. I have a little tournament next weekend and want to make sure I do my best. I do apologize for not posting any updates but I have full intentions of getting them up and running in the next month or two. I'll keep you guys posted!

[JonMarsh]

Of course there's an update, I haven't done anything to them...yet!

Right when I stopped posting on this is when my wife and I decided to redo the theater room in the basement. New ceiling, new paint, new projector, new DIY 100" screen, new wiring etc. I also just got back from Colorado and have also been playing and practicing a ton of golf. I have a little tournament next weekend and want to make sure I do my best. I do apologize for not posting any updates but I have full intentions of getting them up and running in the next month or two. I'll keep you guys posted!

Hey, it's great that I'm not the only layabout and laggard around this forum!

I think you've been having a lot more fun than I have in your non-speaker building time, though, so I'm a bit jealous...

My return to DIY should start around the end of June. Between now and then it's still probably eight days a week, and most in the air going somewhere on biz. But a new manadatory PTO plan for cost savings at work is going to save my sanity and DIY efforts. Five weeks scheduled at the moment between now and the end of September. :B

We'll be waiting with bated breath until you're done with your golf and ready to return to this project....

~Jon

[PoorboyMike]

Hey, it's great that I'm not the only layabout and laggard around this forum!

I think you've been having a lot more fun than I have in your non-speaker building time, though, so I'm a bit jealous...

My return to DIY should start around the end of June. Between now and then it's still probably eight days a week, and most in the air going somewhere on biz. But a new manadatory PTO plan for cost savings at work is going to save my sanity and DIY efforts. Five weeks scheduled at the moment between now and the end of September. :B

We'll be waiting with bated breath until you're done with your golf and ready to return to this project....

~Jon

It's about time! :B

My Infinity center isn't quite up to the task of playing with the NatPs. As far as inexpensive commercial centers go, it's not bad, but it lacks the detail of the RS drivers. At least it's a 3-way. The RS52 w-m/t-w center is on my list of projects for the summer. ;x(

[JonMarsh]

It's about time! :B

My Infinity center isn't quite up to the task of playing with the NatPs. As far as inexpensive commercial centers go, it's not bad, but it lacks the detail of the RS drivers. At least it's a 3-way. The RS52 w-m/t-w center is on my list of projects for the summer. ;x(

It's on mine, too! It's in a tie for priority #1.

[cobbpa]

Of course there's an update, I haven't done anything to them...yet!

Right when I stopped posting on this is when my wife and I decided to redo the theater room in the basement. New ceiling, new paint, new projector, new DIY 100" screen, new wiring etc. I also just got back from Colorado and have also been playing and practicing a ton of golf. I have a little tournament next weekend and want to make sure I do my best. I do apologize for not posting any updates but I have full intentions of getting them up and running in the next month or two. I'll keep you guys posted!

I say putting up pics of your basement work & the DIY screen could count as solid board contribution...ifff you put pics up! :T

I also say that the more golf a person can play, the better. I think some of my most enjoyable days in my life (only 22 yrs thus far, mind you) came when I first had my driver's license but no job for a couple of summers...5+ hours a day was the average, mostly range or practice green work. Boy I miss that. But on the positive, haven't we had some great weather for the game lately? Sunny & breezy..love it. 8)

Anyway, I'm looking forward to your progress, but enjoy the golf & dominate that tourney!