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Push-Pull horns [message #20314] Fri, 27 August 2004 07:30 Go to next message
martin seddon is currently offline  martin seddon
Messages: 2
Registered: May 2009
Esquire
Hi,

I recently built what I call a push-pull horn and would like to chip in with my own experiences.

It started out with a large fibre glass 160Hz front horn for a Lowther PM2a. Then I made an L shaped 2.2m 7000cm2 f/glass and ply horn for bass using a CA25FEY.

I had cross over difficulties I didnt know how to solve and eventually adapted the horn to back load the Lowther. This was done by breaking the top round fibreglass section over to mate with the mounting plate on the fronthorn. So there are only 2 x 90 degree bends (using reflector plates. The driver sits in the throat of the backhorn - with no throat chamber.

HornResponse predicted it would work down to 50Hz at c. 102 dB - and I think it may actually be true in practice - tho I havnt measured. It works much better than I expected - great bass integration. A

Re: Push-Pull horns [message #20315 is a reply to message #20314] Fri, 27 August 2004 10:42 Go to previous messageGo to next message
GM is currently offline  GM
Messages: 114
Registered: May 2009
Viscount
>Extended HF down the back horn is OK.
====
If the 'XO' point is kept low enough, I agree, but I've experimented enough with BLs that above ~250Hz (some say as low as 100Hz) I find the comb filtering unacceptable, so as always YMMV.
====
>The back horn throat chamber (LP acoustic filter)is best eliminated - this removes the nasty looking peaks (phase inversions?) shown by HornResponse - which even if well down, must surely be heard full level from the front.
====
Hmm, if you design the horn properly, the filter doesn't cause this due to the first section of the horn damping it. I assume that either by design/experimentation/blind luck yours works due to having the ~correct first section that is in effect the LP filter.

GM



Re: Push-Pull horns [message #20316 is a reply to message #20315] Sat, 28 August 2004 07:11 Go to previous messageGo to next message
martin seddon is currently offline  martin seddon
Messages: 2
Registered: May 2009
Esquire
Well with my old cloth ears and lack of measuring skills I won't make any rash claims. I build the contraptions as an experiment not expecting that much out of it - and was pleasantly surprised. I think possibly back horns get a bad name (and I've heard a few) because they are not even close to a proper expansion. Once one builds something like the real 50Hz thing (never minding the power to weight ratio, waf etc)one discovers what these drivers can do in the bass end. amazed just how enjoyable and free a single triode / horn can be.

best rgds, martin s

Re: Push-Pull horns [message #20317 is a reply to message #20316] Sat, 28 August 2004 16:55 Go to previous messageGo to next message
GM is currently offline  GM
Messages: 114
Registered: May 2009
Viscount
Agreed, I've yet to hear a 'fullrange' single driver backhorn that has the proper loading for the app other than my few 'proof of concept' designs.

GM

Re: Push-Pull horns [message #20318 is a reply to message #20317] Sat, 28 August 2004 17:12 Go to previous messageGo to next message
JeffM is currently offline  JeffM
Messages: 9
Registered: May 2009
Esquire
I agree. A backhorn is so narrow it must be more like a TL or TQWP than a horn. Not that that's bad at all, but I think it is true.

Re: Push-Pull horns [message #20319 is a reply to message #20318] Sat, 28 August 2004 19:32 Go to previous messageGo to next message
roncla is currently offline  roncla
Messages: 125
Registered: May 2009
Master
Well i spent around 6 months developing a horn for the 206e and its based on a very low M factor hyperbolic/exponential flare. It performs as designed and i believe i have the proper loading.Any BLH is going to have some TL action.
ron

Re: Push-Pull horns [message #20320 is a reply to message #20319] Sat, 28 August 2004 21:19 Go to previous messageGo to next message
GM is currently offline  GM
Messages: 114
Registered: May 2009
Viscount
Yeah, when I add enough series R to get the mass corner down to ~250Hz, I calc the flare = ~6Hz, M = 0.509, so for all intent it's a very narrow angle conical horn.

GM

Re: Push-Pull horns [message #20321 is a reply to message #20320] Sat, 28 August 2004 22:32 Go to previous messageGo to next message
roncla is currently offline  roncla
Messages: 125
Registered: May 2009
Master
so for all intent it's a very narrow angle conical horn.

If real estate is location, location, location then horns are size,size,size.
ron

Re: Push-Pull horns [message #20322 is a reply to message #20321] Sat, 28 August 2004 23:10 Go to previous messageGo to next message
GM is currently offline  GM
Messages: 114
Registered: May 2009
Viscount
Yep, which sets the gain.

GM

Re: Push-Pull horns [message #20324 is a reply to message #20322] Sun, 29 August 2004 09:44 Go to previous messageGo to previous message
roncla is currently offline  roncla
Messages: 125
Registered: May 2009
Master
GM,I posted the flare in the FR Tech forum gallery, it really dosent appear to be a conical flare.And i find that no series resistance to be the best sound (in this case)
ron

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