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Multi-Way Conventional loudspeakers with crossovers

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Old 7th December 2012, 07:48 PM   #331
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These renderings look interesting, but there are some practical issues:

1) There's no benefit to leaving the woofers unbaffled. It just wastes efficiency. This is StigErik's conclusion and generally confirmed by others who've made swinging dipoles.

2) It doesn't make sense to place the mids side by side. Your tweeter has a tall diaphragm so it has limited vertical dispersion. The mids may as well match that by stacking vertically, as you had before. Or if you can get enough output from one driver just place it below the tweeter. I would suggest TMM is better than MTM given the large size of the tweeter.

3) The structure looks pretty hard to build with the two upright elements flowing together across the bottom. Try making some mini versions with cardboard to see how strong it is and how well it holds together. It's possible you could do this with one big piece of metal plate that's folded across the bottom. See below, someone posted this awhile back (don't recall where).

DSC_0221-1.JPG
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Old 7th December 2012, 09:58 PM   #332
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Thanks TJ for your input.

1. Does this apply to mid woofers as well? As the 18" woofers will be in a H frame. Guessing it may since the mid woofers go down to about ~100hz where there is some serious roll of.

3. Structure would be easier as would use the same router jigs twice per speaker. The piece across the front would be a separate piece that would be routed once glued in place (or not used at all).

Back to the drawing board to come up with a baffled version that doesn't look boring.
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Old 7th December 2012, 10:20 PM   #333
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It's the four midwoofers that I was referring to, they would work better with a baffle. It could even be a shallow H-baffle to reduce loss at the low end, and to add strength. I like the group of four midwoofers in a compact square.
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Old 7th December 2012, 11:23 PM   #334
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I bought a new external sound card? (Roland AU 55) the other day and a new Dayton EMM-6 mic to get better measurements out of the Ground Sound / XOver Wizard 2 Advanced software.

Rather than pot guesses at what I need it is time to do a bit measuring to determine what my real needs are. I half feel like I am throwing drivers at this project for the sake of it...

So what I might do is try a few measurements of 2 and 4 mid woofers and try measuring with and without a baffle. I have been far from scientific with this build so far, time to let some measurements dictate it course.

Having said that up to now I have only had my ears to work with because I couldn't get the software to work until I bought the right equipment and Robert from Ground Sound gave me a hand.
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Old 9th December 2012, 12:24 AM   #335
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Spent a little time yesterday trying to take some measurements of the current prototype 4 way.
After a bit of playing around with the crossover slopes I have come up with the following graph.
No filters applied, no delay etc.

Woofer is crossed over a little higher than I like but that is compensate for a lack of a proper baffle set up on the woofer.

Note: measured at 85cms from speaker, 85cms from floor between tweeter and mid.
Attached Images
File Type: jpg Measurement 1 - 4 way - No Correction.jpg (292.9 KB, 202 views)
File Type: jpg Measurement 1 - 4 way - No Correction - XOver.jpg (327.8 KB, 191 views)

Last edited by Silent Screamer; 9th December 2012 at 12:32 AM.
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Old 9th December 2012, 12:41 AM   #336
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Leaving the same crossover slope in place (no optimisation) and moving the crossover from 250hz down to 85hz reveals the roll off of the 18WUs.

I could EQ them back up a bit, but might see what happens when I mount them on a baffle. I expect to find I may not need such a big correction.
Attached Images
File Type: jpg Measurement 2 - 4 way - No Correction.jpg (284.4 KB, 180 views)
File Type: jpg Measurement 2 - 4 way - No Correction - XOver.jpg (326.6 KB, 163 views)
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Old 9th December 2012, 02:55 AM   #337
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At first I tried adding +3 to the mid and -3 to the mid woofer (bottom part of picture)

Which made me wonder what would happen if I was to double up the mid (12MU) as per the original intent. (top part of picture)

Interesting findings...

I found that doubling up the driver (in series) made very little difference where adding 3dB to both the the single and double 12MU had a greater impact.

I put this down to the limited bandwidth of the XOver. When placing my ear up against one of the 12MU vs one of the 18WU the is a very audible difference in SPL.

So it would seem there is little to gain by adding the second 12MU.
Attached Images
File Type: jpg Gain Test 2.jpg (259.3 KB, 159 views)
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Old 13th December 2012, 03:07 AM   #338
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Still making progress with learning how to use the software and how to get some meaning results out of the readings I am capturing.

I would have never managed to get this off the ground without Roberts extremely patient assistance. So far I am very happy with the Ground Sound DCN28, but the help section of the included software (another vendor) is terrible. The customer service at Ground Sound is second to none.

While progress is slow I sort of learned a new trick yesterday. Using the Group Delay I can apparently determine where reflections are showing up in my measurements. I still havenít worked out how to filter them out (if I can at all) but access to this sort of data can only make proper placement in the room so much better, and perhaps even help with some external acoustic dampening down the track.

Not overly worried about how to use this feature properly yet as I am still trying to work through proper cable connections and electrically configuring the hardware I need to use with the software.

Karsten hang in there help is comingÖ I hope to get to a point in the not too distant future where I understand the more advanced software features much better. I had my first go at using the auto EQ feature the other day, still a bit hit and miss but overall the learning level is coming up.
Attached Images
File Type: jpg Reflections.jpg (309.3 KB, 22 views)
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Old 18th December 2012, 10:44 PM   #339
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A new baffle is bornÖ

Now that I am getting the hang of using the mic and collecting measurements, I have made up a new prototype baffle to do some direct comparison. I only finished late last night so I didnít have chance to do much evaluating, but here are my very early findings.

The top end seemed to lack a very tiny amount of detail (not sure if this is related to a wide baffle close to the wall), and there is more bass although I donít think it is as clean sounding.
I did throw the mic on to do some very quick snap shot figures. First measurements were done with the mic in line with each of the drivers (also 2 and 4 x 18WU measurements), the second lot were stationary in front of tweeter area (4 x 18WUs only).

Not the greatest comparison but rough enough to get some early findings. It still has a nasty dip around the 300Hz mark, but on the baffle the mid bass makes a comeback, which indicates there is still some more research to be done with the mid bass area. Possibly even look at making a U or H baffle for just the mid woofers. Both the tweeter and the mids seem a bit smoother in response, but I am keen to see if I can cut the baffle back a bit in the area of the tweeter and mids and still keep the smoother response.

Hope to do some more conclusive testing tonight.
Attached Images
File Type: jpg IMAG1198-1.jpg (130.2 KB, 65 views)
File Type: jpg Quick Compare 1.jpg (274.5 KB, 64 views)
File Type: jpg Quick Compare 2.jpg (279.1 KB, 31 views)
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Old 19th December 2012, 02:47 AM   #340
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Yeah, try tapering the sides into the mids and tweeter. Like a pyramid. I like the midbass in a square quite a lot. Looks imposing and keeps overall height manageable.

Where is your crossover point btw the woofer and mids? Are they the same for the mid to woofer transition or do you accidentally have a gap programmed in there? Have you tried flipping the relative phase of the mids or woofers and have a look at the measurements? Where are those measurements taken from? You might be back too far and getting room effects added in more strongly than you want right now. I like to see a combination of closer measurements on the tweeter axis of no more than a foot away and then again at a meter and maybe 2 meters or the listening position. I use the closer ones to see what the drivers are doing with less room effects.

EDIT: I think I see now that the yellow is the midbass, purple is the mids and blue is the Raal, correct? Why run the midbass so high? You need to be looking at using those 12mu for more than just 2 octaves. That's a waste. Think more around 300-500Hz at least. Also, the entire bass range needs to come up. You need a dipole correction EQ as the low end is drooping too much.

Last edited by studiotech; 19th December 2012 at 02:52 AM.
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