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Multi-Way Conventional loudspeakers with crossovers

DIY PMC MB2 clone
DIY PMC MB2 clone
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Old 19th August 2017, 10:02 AM   #21
WalterPPK is offline WalterPPK  Netherlands
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I can test a design from top to bottom WMTW. Let's see how that will look.

Last edited by WalterPPK; 19th August 2017 at 10:25 AM.
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Old 19th August 2017, 10:26 AM   #22
WalterPPK is offline WalterPPK  Netherlands
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Old 19th August 2017, 10:35 AM   #23
wae is offline wae  Netherlands
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About positioning;
You also could place both mid and high NEXT to the low units, which could than be placed closer to each other.

And;

NO bracing of the front panel? That's where the mayhem mostly starts

My approach to this is, place a brace that makes the front panel at the point of the driver as small as possible, so the panel at the location of the driver almost has the same surface (cm2) as the driver. NO panel resonance (well hardly any) as a result.

You could do;
1 - Front to back
2 - Side to side
3 - Top to bottom.

If you place "1" and "2" off center, they will fit nicely.

"3" will hit "1" or "2", take your view.

As for your drivers, the SB Acoustics W024P-8 has an efficiency of 88dB, that is NOT much, also compared to the mid and high units. Requires some clever filter.
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Last edited by wae; 19th August 2017 at 10:42 AM.
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Old 19th August 2017, 10:41 AM   #24
wae is offline wae  Netherlands
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Quote:
Originally Posted by wae View Post
About positioning;
You also could place both mid and high NEXT to the low units, which could than be placed closer to each other.

Ooops, sorry did no see post 22

Yep so number 4 looks to me like the first go.

number 1 also looks like a candidate, but as being mentioned, turn it on its side for correct position of mid and high.

2 and 3 would be no option to my view, they both have 2 ports blasting alongside the high unit.
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Old 19th August 2017, 11:00 AM   #25
wae is offline wae  Netherlands
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By the way, forgot to ask;

Why leave the TL option? I think that a TL (properly designed) gives a much better low end control than a bass reflex does. This adds to lower distortion, which is one of the reasons people like TL's.

It will only take some time and a bit of wood to give it a go.

I did some A - B (on paper, using design software) with a few drivers (Volt RV3134, Faital Pro 12PR300 and some others I don't recall) in a bass reflex opposed to the same driver in the same volume TL cabinet with the filter settings and the same amount of power. Result:

1 - MOST drivers in the TL showed about (sometimes even more) of the excursion in the region below say 50 Hz,
2 - MOST drivers showed higher SPL in the TL below the Bass reflex tuning point (from dB to 3 dB varying per driver)
3 - The TL (although could be tricky) showed 3 major "tuning" points, where you could make it honk to your liking. That is at the closed end, right at the driver position and at a small offset of the open end of the TL. A BR can also be "tuned" but that is more the character of the sound, light damping can make it a bit "harsh" while much damping will make it more smooth but at the cost of a Db or 2.

In a studio, you want to have an Honest open sound with loads of detail. The TL seems to be the better candidate, although we see loads of BR versions for a studio. HHmmm

When I find the time, I intend to post a thread on this, not really theoretical but more practical comparison.
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Last edited by wae; 19th August 2017 at 11:04 AM.
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Old 20th August 2017, 01:36 PM   #26
WalterPPK is offline WalterPPK  Netherlands
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Join Date: Apr 2012
Quote:
Originally Posted by wae View Post
About positioning;
You also could place both mid and high NEXT to the low units, which could than be placed closer to each other.

And;

NO bracing of the front panel? That's where the mayhem mostly starts

My approach to this is, place a brace that makes the front panel at the point of the driver as small as possible, so the panel at the location of the driver almost has the same surface (cm2) as the driver. NO panel resonance (well hardly any) as a result.

You could do;
1 - Front to back
2 - Side to side
3 - Top to bottom.

If you place "1" and "2" off center, they will fit nicely.

"3" will hit "1" or "2", take your view.
I get what you mean. The design has to be altered to get the tweeter and mid vertically alligned so I will redesign the braces as well.

Quote:

As for your drivers, the SB Acoustics W024P-8 has an efficiency of 88dB, that is NOT much, also compared to the mid and high units. Requires some clever filter.
Originally the Volt mid is paired with the RV3134 in the MB2 which has 91,5db sensitivity. I thought that two WO24P would compensate to a healthy 91db. But ok, the idea is to use a DCX in the beginning and to move on to a DEQX or something more high end in the future.
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Old 20th August 2017, 01:54 PM   #27
WalterPPK is offline WalterPPK  Netherlands
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Join Date: Apr 2012
Quote:
Originally Posted by wae View Post
By the way, forgot to ask;

Why leave the TL option? I think that a TL (properly designed) gives a much better low end control than a bass reflex does. This adds to lower distortion, which is one of the reasons people like TL's.

It will only take some time and a bit of wood to give it a go.

I did some A - B (on paper, using design software) with a few drivers (Volt RV3134, Faital Pro 12PR300 and some others I don't recall) in a bass reflex opposed to the same driver in the same volume TL cabinet with the filter settings and the same amount of power. Result:

1 - MOST drivers in the TL showed about (sometimes even more) of the excursion in the region below say 50 Hz,
2 - MOST drivers showed higher SPL in the TL below the Bass reflex tuning point (from dB to 3 dB varying per driver)
3 - The TL (although could be tricky) showed 3 major "tuning" points, where you could make it honk to your liking. That is at the closed end, right at the driver position and at a small offset of the open end of the TL. A BR can also be "tuned" but that is more the character of the sound, light damping can make it a bit "harsh" while much damping will make it more smooth but at the cost of a Db or 2.

In a studio, you want to have an Honest open sound with loads of detail. The TL seems to be the better candidate, although we see loads of BR versions for a studio. HHmmm

When I find the time, I intend to post a thread on this, not really theoretical but more practical comparison.
The TL cabinet for the RV3143 was too large for our control room. The outcome of designing and building a TL cabinet is too uncertain for me. I don't have enough time to tune/experiment with it to get it right . A br cabinet is more predictable. Maybe I will do some designing/experimenting with TL enclosures on a next project.
My experience is that under 200hz every room sounds so different that correction is always needed to get optimum flat response and extension.
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Old 21st August 2017, 10:35 AM   #28
Charles Darwin is offline Charles Darwin  United Kingdom
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Join Date: Nov 2009
Location: Birmingham, UK
Since you are using two 8Ω woofers per side have you decided how you are going to wire them up?

In series you double the impedance to 16Ω and consequently halve the power available to them but also double the cone area resulting in no change in output.
In parallel you halve the impedance seen by the amp and so double the power and also double area resulting in a 6dB net gain over a single 8Ω woofer given the same voltage.
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Old 21st August 2017, 08:56 PM   #29
WalterPPK is offline WalterPPK  Netherlands
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The woofers will be driven by a Aragon 2007. What would you recommend? I was thinking the 16 ohm route to increase the damping factor.
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Old 21st August 2017, 10:53 PM   #30
Charles Darwin is offline Charles Darwin  United Kingdom
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Just checked and that amp puts out 300W into 4Ω.
That means it will roughly produce 150 into 8 and 75W into 16Ω.

I would definitely go the 4Ω road!
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