Tony, this thread has got me very interested in the big PD woofers.
Have you tried the U baffles in stereo mode? I would be very interested to know what sort of bass depth you would be getting in room with the 21" and baffles of this size without eq.. ?? Also, what are you using to drive these beasts - would a high quality but lower power amp work in your opinion (say 25-50 watts?).
I am inspired to seriously think on what a pair of the 23" PD's would be like under my Goodmans 401's and a good supertweeter on a really big OB..
David
Have you tried the U baffles in stereo mode? I would be very interested to know what sort of bass depth you would be getting in room with the 21" and baffles of this size without eq.. ?? Also, what are you using to drive these beasts - would a high quality but lower power amp work in your opinion (say 25-50 watts?).
I am inspired to seriously think on what a pair of the 23" PD's would be like under my Goodmans 401's and a good supertweeter on a really big OB..
David
David,
The theory behind how much bass you get out of a dipole is actually quite simple. Output is determined by two things:
1. D
2. driver displacement
Linkwitz has a spreadsheet to calculate this for you
Put another way, a dipole is like a sealed box with has a 1st order highpass filter with a corner frequency at fequal
fequal = 0.17 x 344/D
In a U frame you must double the depth of the box to get D in comparison to a H frame.
Take a 24" wide 12" deep U frame. The value of D = 24/2 + 12 x 2
D = 36" or 1.2m
hence fequal = ~50 Hz
This should yield an anechoic F3 around 50 Hz, although I'm not sure of the response of that driver in a sealed box. F3 might be as high as 60 Hz but for music it should not need much eq at all. Eq might be needed more because it will benefit less from room gain.
The theory behind how much bass you get out of a dipole is actually quite simple. Output is determined by two things:
1. D
2. driver displacement
Linkwitz has a spreadsheet to calculate this for you
Put another way, a dipole is like a sealed box with has a 1st order highpass filter with a corner frequency at fequal
fequal = 0.17 x 344/D
In a U frame you must double the depth of the box to get D in comparison to a H frame.
Take a 24" wide 12" deep U frame. The value of D = 24/2 + 12 x 2
D = 36" or 1.2m
hence fequal = ~50 Hz
This should yield an anechoic F3 around 50 Hz, although I'm not sure of the response of that driver in a sealed box. F3 might be as high as 60 Hz but for music it should not need much eq at all. Eq might be needed more because it will benefit less from room gain.
David Shanks said:
This weekend I made a true stereo set-up. Stereo imaging has improved (it wasn't bad already
). What also suprises me is how well the 21" woofers and the 6,5" midwoofers integrate as one. I have no need at all to put something like a 12" in between. As for bass depth, for music there is plenty of well defined absolutly clear bass which produce a true life double bass or drum kit. Only for special effects in movies, it could do with a fraction more power at the 20-30Hz range.An externally hosted image should be here but it was not working when we last tested it.
PHL 1550 coax midwoofer, 16 ohms with a modified Monacor MRD-180 on the back.
An externally hosted image should be here but it was not working when we last tested it.
PD2450
Geenius - what about PD2450? 3 inches bigger
Dunno what the price of the speakers in nl/west europe is but so far the cheapest european distributor of these is the polish one - http://www.case-pack.pl/
lots of people here in czech rep built 1850 horn - http://speakerplans.com/index.php?id=1850horn and the price difference between cz and pl was some 100 EUR/pc on a PD 1850
They are even able to refund VAT
Geenius - what about PD2450? 3 inches bigger
Dunno what the price of the speakers in nl/west europe is but so far the cheapest european distributor of these is the polish one - http://www.case-pack.pl/
lots of people here in czech rep built 1850 horn - http://speakerplans.com/index.php?id=1850horn and the price difference between cz and pl was some 100 EUR/pc on a PD 1850
They are even able to refund VAT
Re: Re: Re: PD2450
She is a classical violinist, so she appreciates good sound.
The PHL coax has a nice dynamic approach to music, very clear and open. The Monacor 1" PA driver on the back is crossed at about 1200Hz and produces nice clean treble which never fatigues. The treble was a little harsh to start with but I modified the driver by placing a layer of felt in the rear chamber. It then became calmer without loosing it's "bite". The overall spatiality of the image is very good, better than a lot of non-coax systems I have built. All in all, I am rather happy
David Gatti said:
By the look of your living room, she's pretty tolerant
How does your coax driver sound?
She is a classical violinist, so she appreciates good sound.
The PHL coax has a nice dynamic approach to music, very clear and open. The Monacor 1" PA driver on the back is crossed at about 1200Hz and produces nice clean treble which never fatigues. The treble was a little harsh to start with but I modified the driver by placing a layer of felt in the rear chamber. It then became calmer without loosing it's "bite". The overall spatiality of the image is very good, better than a lot of non-coax systems I have built. All in all, I am rather happy
Update: The Precision Devices PD2150's are now running in a passive so-called double Ri-pole configuration. Compared to the U-frame, they are less efficient and lean towards a boxy sound. Also bass is less well defined but it is hard to beat a U-frame in that dicipline. They still sound impressive and a big advantage is the compact size.
More info: Ri-pole example
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
More info: Ri-pole example
Since yesterday I am running the subs with an active crossover and room correction. The two graphs show the situation before and after correction. The first unfiltered curve shows a resonance peak at about 170Hz that is typical for most di-pole designs and the output drops below 35Hz - it would have dropped at a higher frequency but my room has a strong room node at 35Hz that can be seen in the strong correction of the graphic equalizer in the second graph. The corrected output is near flat down to a -3dB point of around 20Hz . On the otherhand, I can boost as much as I like below 20Hz but it doens't have any effect to the output level.
. On the otherhand, I can boost as much as I like below 20Hz but it doens't have any effect to the output level.An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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