QSC HPR152i waveguides

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#41
Haven't seemed to have an issue yet with the epoxy. I tried to chip off some of the excess and it sticks pretty good as far as I've seen. I did also rough up the surface with sandpaper before applying it, which likely helps. That said, I'm not concerned anyways because I was planning on having the screws go a bit into the horn.

Why tweeters? Well for one it's an inexpensive experiment and I though I'd try something a bit unconventional. The idea of using tweeters is amusing to me, but I have a hunch it might not work so bad. Another reason is that it's difficult to get the mids to play high on normal synergy using larger (and not expensive prosound) mids. Of course you can get HF by oversizing your mid ports, but then you're compromising your design. I thought it would be fun to see if I could get the bandpass to play up to 2k.

Also, this is the post that got me thinking about the idea.

JLH said:
When I was trying to find a suitable mid range driver for the Unity and Synergy horns I can across the Misco RDC3T-A.

http://www.diyaudio.com/forums/multi-way/88237-suitable-midrange-cone-bandpass-mid-unity-horn.html

Once again I was told it couldn’t work because it was a cone tweeter and not a real mid range driver. Confident that it would work, I ordered a half case (30 speakers) and measured the T/S parameters. Come to find out, due to its low Le and moving mass, this speaker behaves in a purely resistive manner when horn loaded. This eliminated the problem of dealing with the mid range’s impedance peak. This allowed the RDC3T-A to take on whatever the local flair rate was. It would load to and play to whatever frequency you designed the horn for without having the Fs peak screwing things up.
Click to expand...

And I know it's not quite identical to the RDC3T-A, but I figured it was an inexpensive experiment to try.

As for why I'm not using a single midrange, my interest is in prosound use. That's why I'm packing 6 of them in there and trying to evaluate how much SPL it's possible to get out of it.

And I don't want to get too optimistic before I start doing sweeps, but how fun would it be if you could get a cheap 1" CD and $18 worth of tweeters to outrun much more costly larger CDs from 600hz up?
 
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#42
@fabrice63 and @POOH, to which mid/low driver(s) do you guys cross the PRV waveguide + comp. driver to and what are your XO points ?
The QSC 152i WG's are still obtainable from some QSC dealers in Europe, but I was surprised to learn they charge roughly 100-200 Euro a pair. Provided shipping costs won't break the bank, these PRV wg's look like a nice alternative, moreover due to the extra mounting holes.

Fabrice63, did you order your waveguides directly from Parts Express? I thought they won't ship to Europe.
 
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#43
I'm temporarily using the PRV horn with my big system. The Celestion CDX1730 driver is in the PRV to Fane Studio 10M in bass horns crossed at 1200 cycles. I like to crossover lower with a bigger driver- working with the JBL 2435 be driver to replace this soon. Sounds pretty nice. My PRV's have added dampening but out of the box they are pretty inert.

I have plans to use these upper range horns/drivers in a smaller system crossed over to twin JBL 2204 12" in an MTM or MMT. Crossover is undecided.
 
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#45
Fabrice,

This sweep of yours ( JBL 2426 on PRV 152i clone );

attachment.php


Is this without EQ?

Also, how much ferrofluid was added to the gap?

Do you have any before & after sweeps that show the effects of adding the ferrofluid ?

Here are a pair of my ( raw horn/driver ) REW sweeps ( 2 different vertical scales ).

JBL_2426H_on_152i_Horn-Clone_.png

JBL_2426H_on_QSC_152i_horn_clone.png


I'm now wondering if the addition of ferrofluid might actually knock-down ( flatten ) the 1K-2K hump that's seen in my pics.
- Your trace is very flat ( by comparison ) over this same area.

🙂
 

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#46
Yes the sweep is made without any EQ , the amount of ferrofluid is 0.450ml per driver .

I have made some mesurement before and after but it was without the horn , main differences were , lower distortion and an cone like sound with ferrofluid ,an "flatten" curve at 1.5 khz and - 5 db at 12 khz.


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#47
fabrice63 said:
Yes the sweep is made without any EQ , the amount of ferrofluid is 0.450ml per driver .

I have made some mesurement before and after but it was without the horn , main differences were , lower distortion and an cone like sound with ferrofluid ,an "flatten" curve at 1.5 khz and - 5 db at 12 khz.
.
Click to expand...

Fabrice,

Thank-you for your response.

Your results are consistent with info I was given ( many years back ) from a contact at Radian ( when I asked about ferrofluid ).

( Thinking Outloud ),
- I'm not sure if I could afford a minus 5db drop in the UHF since the 2426 is already challenged in it's top octave when compared to more modern drivers .
- If I try ferrofluid I might first try one half of the amount you've used.

🙂

PS; What type of plane is that (in your avatar) ?
 
#50
Thank you for your replies Fabrice, Pooh and the others for posting useful info.

Fabrice, do you still have the 'raw' sweeps without smoothing? This looks quite good, I wonder what the impact of the 1/8 oct. smoothing is.

I still have some old Fane Studio 15L woofers (100dB) laying around. The PRV WG's should (like the QSC's) work with 15" mid/low woofers that have a useful response beyond 1500Hz. I will probably use a Faital-Pro, Beyma or B&C comp., at least with polymer or polyimide diaphragm.
 
#51
here you'll find mesurement made with and without ferrofluid , 1/6 db smoothing , without horn , at 1 m , less than a watt .

green is with ferrofluid

red is without ferrofluid





here are the same sweep , but without any smoothing .






What ever happens , with ferrofluid is better , sound is smoother , a nice "HIFI" sound ;-)




.
 
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