Another converted to dipole

[chops]

I read the whole Chops thread last night and was wondering if there is any advantage or disadvantage in placing the 15 inch woofers on a plain baffle like Miguel's compared to building them into an H frame or other casing.?

Boy, I'm gone for a little while and I become famous! lol

To answer your question Nuuk, from what I read in the past, it seemed that the H-frame or W-frame would give you better low end response rather than just a flat open baffle. The reason for this is that the larger the baffle, the lower in frequency the driver can reproduce before the the front and back wave meet and cancel out the bass.

That's why I went overboard with the size of my dipoles. I got sick of hearing everybody saying that dipole subs couldn't reproduce anything below 40Hz. If you look at what type of drivers they're using, their Qts and Fs is exactly backwards of what's needed for dipole use. To tell you the truth, I wouldn't give you 5 cents for those Peerless drivers, not for dipole use anyway. The other reason they don't get anything below 40Hz is because the size of baffles they're using. They are so small and compact, it's a wonder they reproduce any bass at all.

Someone here figured it out for me once before (Planet10 maybe), that with the size of my H-frame, I have about 8 or 12 feet of combined distance from the front to the back of the woofers. If someone here can confirm that for me, I would appreciate it. The dimentions are 24"W x 24"D x 48"H.

In fact, I'm sitting here listening to Pink Floyd's Dark Side Of The Moon on SACD as I'm writing this. Some of this bass is so deep and loud, I can only feel it going through my head and chest, plus something down the hallway and in the livingroom, I can hear something rattling like crazy.

 

[Nuuk]

Thanks Chops, those diopole subs have made you famous around the world!

I'm being quite fussy over drivers having the right characteristics, high Qts and Xmax but I will probably have to go with a W baffle as explained in this other diyAudio thread

 

[ThorstenL]

kONNICHIWA,

Someone here figured it out for me once before (Planet10 maybe), that with the size of my H-frame, I have about 8 or 12 feet of combined distance from the front to the back of the woofers. If someone here can confirm that for me, I would appreciate it. The dimentions are 24"W x 24"D x 48"H.

If it is an H frame, 24" deep & 48" high then you have a distance of around 48" maybe 60" effective and a baffle width/hight of maybe 60" X 36". The distance related acoustic shortcircuit would be around 230Hz. My still somewhat imperfect Baffle model using a "fudge factor" for the "wings" on the H Baffle suggests -6db @ 37Hz with respect to 100Hz.

HOWEVER, you are using an X-Over that aready attenuates 3db @ 90Hz, and an EQ with 6db cut @ 90Hz further flattening the resultant response to around +/-3db from around 30Hz (-3db) to 120Hz (-3db) with a 3db peak around 50-60Hz, that being the Sub response only, not the system response. The -6db point with respect to the peak around 50Hz is obviously around 30Hz, with respect to the average SPL of the equalised and crossed over sub it is around 25Hz!!!

Now having very low frequencies at around -6db to the main output will still give a very substantial perception of "presence" of output, not much diminished as such at all. So your comments do not surprise me at all. This dipole will go quite low with fairly little EQ and a suitable X-Over.

In fact, I'm sitting here listening to Pink Floyd's Dark Side Of The Moon on SACD as I'm writing this. Some of this bass is so deep and loud, I can only feel it going through my head and chest, plus something down the hallway and in the livingroom, I can hear something rattling like crazy.

I get the same sort of effects with dual sealed 12" Woofers crossed over at 40Hz (X-Over -3db point) to my open baffles with Supravox 8" Fullrange drivers.

Sayonara

 

[chops]

kONNICHIWA,



If it is an H frame, 24" deep & 48" high then you have a distance of around 48" maybe 60" effective and a baffle width/hight of maybe 60" X 36". The distance related acoustic shortcircuit would be around 230Hz. My still somewhat imperfect Baffle model using a "fudge factor" for the "wings" on the H Baffle suggests -6db @ 37Hz with respect to 100Hz.

HOWEVER, you are using an X-Over that aready attenuates 3db @ 90Hz, and an EQ with 6db cut @ 90Hz further flattening the resultant response to around +/-3db from around 30Hz (-3db) to 120Hz (-3db) with a 3db peak around 50-60Hz, that being the Sub response only, not the system response. The -6db point with respect to the peak around 50Hz is obviously around 30Hz, with respect to the average SPL of the equalised and crossed over sub it is around 25Hz!!!

Now having very low frequencies at around -6db to the main output will still give a very substantial perception of "presence" of output, not much diminished as such at all. So your comments do not surprise me at all. This dipole will go quite low with fairly little EQ and a suitable X-Over.



I get the same sort of effects with dual sealed 12" Woofers crossed over at 40Hz (X-Over -3db point) to my open baffles with Supravox 8" Fullrange drivers.

Sayonara

OUCH!!! You just hurt my brain! lol

So what you're saying is that my subs are fairly flat down to 25Hz, if not lower due to room response?

That's what I kind of figured just by ear.

I have one more question for you then.... What do you think the efficiency of my dipoles are, considering that just one driver is rated at 96dB @ 1 watt? I'm guessing around 105dB @ 1 watt, but I could be wrong.

I only ask because I can push this system to about 115dB without any strain or distortion, and without the LEDs on the sub amp ever moving. Not to mention that the drivers themselves hardly ever move no matter what frequency or volume level I play.

 

[chops]

Actually, I was wrong in that last post. These Pyles are 93dB @ 1 watt, not 96dB.