New DIY Mid High (90deg) - AKA PM90

Re: New DIY Mid High

Scott Mullane said:
In fact, it begs the question...why can't the big brands do this?
The stereo image was incredible, the tonal balance was incredible with a beautiful range. Well done Peter.
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It's a good question.
I would seriously consider buying a pair if they we're available ready for the road:)

If someone could make the cabinet, I'd buy it and load it with drivers myseld and paint it.


Sent from my iPhone
 
Re: New DIY Mid High

Helge Dr. Bentsen said:
It's a good question.
I would seriously consider buying a pair if they we're available ready for the road:)

If someone could make the cabinet, I'd buy it and load it with drivers myseld and paint it.


Sent from my iPhone
Click to expand...

Since you and Jeff are both sort of in the same boat and I'm still trying to make a version that can easily be assembled and cut using a CNC router for the most part (a table saw is still the best tool for the baffles), I'm really starting to think it may be worth figuring out a solution to this. I'll talk a bit with Peter and check back later.
 
Re: New DIY Mid High

Here are some plots of Paul’s 90 degree DIY from England.

It’s active 2-way using the RCF 12 inch drivers and a passive crossover on the HF – VHF section of a 4594.

The measurements were taken in an anechoic chamber at Birmingham University and show the response at 0, 45 and 60 degrees off axis.

Its really great to see other people achieving such excellent results :) … +/- 1 dB 100Hz to 18KHz with third octave smoothing.
 

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Re: New DIY Mid High

Peter Morris said:
Here are some plots of Paul’s 90 degree DIY from England.

It’s active 2-way using the RCF 12 inch drivers and a passive crossover on the HF – VHF section of a 4594.

The measurements were taken in an anechoic chamber at Birmingham University and show the response at 0, 45 and 60 degrees off axis.

Its really great to see other people achieving such excellent results :) … +/- 1 dB 100Hz to 18KHz with third octave smoothing.
Click to expand...

Do you know if this was using FIR or IIR processing?
 
Re: New DIY Mid High

Peter Morris said:
Here are some plots of Paul’s 90 degree DIY from England.

It’s active 2-way using the RCF 12 inch drivers and a passive crossover on the HF – VHF section of a 4594.

The measurements were taken in an anechoic chamber at Birmingham University and show the response at 0, 45 and 60 degrees off axis.

Its really great to see other people achieving such excellent results :) … +/- 1 dB 100Hz to 18KHz with third octave smoothing.
Click to expand...

Guys,

Am I missing something here but shouldn't the phase be flatter and not wrap as much as it is through the crossover point?
 
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Re: New DIY Mid High

Chris Greco said:
Guys,

Am I missing something here but shouldn't the phase be flatter and not wrap as much as it is through the crossover point?
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With a 4[SUP]th[/SUP] order crossover there is 360 degrees of phase rap.

Add to that phase caused by the porting of the double 12 horn i.e. 180 degrees at the box tuning frequency … and the then at the other end, the phase caused by the HF/VHF crossover.
 

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Re: New DIY Mid High

Hi Peter,

I like your design and I'm thinking about building a modified version. (Straight baffle resulting in a slightly bigger, but easier to built, cabinet. And possibly a bit longer horn.) One thing that bothers me is the following question: do the bass reflex holes provide sufficient cooling? At full continuous load, more than 500 Watts are dissipated in the rear chamber. Did you measure the temperature rise after a long time at high load?
 
Re: New DIY Mid High

Peter van Gils said:
Hi Peter,

I like your design and I'm thinking about building a modified version. (Straight baffle resulting in a slightly bigger, but easier to built, cabinet. And possibly a bit longer horn.) One thing that bothers me is the following question: do the bass reflex holes provide sufficient cooling? At full continuous load, more than 500 Watts are dissipated in the rear chamber. Did you measure the temperature rise after a long time at high load?
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Hi Peter,

Not sure what you mean by straight baffle (?).

I have never measured the temperature rise, but I actually think the port design should help keep the temperature low. This was a consideration during the design process.

This is a mid/hi box and there is not that much air movement in the ports compared to a bass bin. There are two ports on the bottom and two on the top of the horn mouth. As the air heats up that should mean there is some air convention flow. I suspect that the convection plus the normal port movement of the air will be quite good when compared to other box designs.
 
Re: New DIY Mid High

Peter Morris said:
Hi Peter,

Not sure what you mean by straight baffle (?).

I have never measured the temperature rise, but I actually think the port design should help keep the temperature low. This was a consideration during the design process.

This is a mid/hi box and there is not that much air movement in the ports compared to a bass bin. There are two ports on the bottom and two on the top of the horn mouth. As the air heats up that should mean there is some air convention flow. I suspect that the convection plus the normal port movement of the air will be quite good when compared to other box designs.
Click to expand...
Hi Peter,

You used 2 panels under an angle to mount the 12" drivers. I'm looking into using 1 panel. It will result in a slightly different "compromise" (easier built, longer horn, but probably bigger cabinet).

Would be nice it somebody could stick a thermometer into one of the top holes and measure the temp rise after some time. :)
 
Re: New DIY Mid High

Jack Arnott said:
Is this your own creation, or are you using someone elses'?
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IIRC, Peter does his measurements outside with the speaker cranked up high, the photo is probably Paul’s 90 degree DIY from England mentioned in post #385, taken in an anechoic chamber at Birmingham University.
 
Re: New DIY Mid High

Jack Arnott said:
Is this your own creation, or are you using someone elses'?
Click to expand...

Its "Paul’s 90 degree DIY from England mentioned in post #385, taken in an anechoic chamber at Birmingham University" as Art said.

Here's a picture of my latest (prototype) box - its heavier, bigger, doesn't go as loud, but it goes lower and the sound quantity and directivity are improved. FWIW it uses a BMS HF driver and some new B&C speakers.

Its the best sounding PA box I have ever heard, incredible stereo imagine and depth of field, you feel like you are in the studio. You hear things that you have never heard in the recording before, but unfortunately the horn flare is not generally available. I am however planning to do a new version of my double 10" based on the tricks I discovered with this design.

.... and I have taken a big jump and started work on a small 8" Line-array !!!
 

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