JBL PT 100x100 waveguides, any experience? MPro?

I agree and that's what alluded to earlier. When you add a network the impedance curve will change.

Hello,

What impedance curve is changing?

What you are talking about is measuring the impedance at the amplifier output where it connects to the speaker network. Sure, no problem the amplifier sees a much flatter impedance curve. If you zoom in and measure the impedance where it was originally measured, across the CD / Horn, the impedance and underlying resonance will remain as it was without the network.

By adding the external network what you are doing is equalizing the frequency response without correcting the underlying resonance. Your vowels will still sound nasal but just not as loud.

I am from the school that wants to flatten the impedance and FR of the CD /Horn as much as possible prior to adding the network.

Thanks DT
 
yes, it is hard to get rid of resonances (reflections) with eq.
They still ring down over time.
You can eq it flat but you may still hear it.

If you notch a peak, a frequency half or a third can cause it to ring at full strength (the harmonic sneaks past).

I also heard (not sure), you can eq a horn, but the level of resonances change based on volume levels (say 90db vs 100db).

The pt waveguide you have looks good, less reflections = more detail, more you hear into a recording.
 
I am from the school that wants to flatten the impedance and FR of the CD /Horn as much as possible prior to adding the network.

Hello DT

Yeah OK but it's natural to have at least 2 peaks in the curve. Its the nature of the beast. Also there is no external Band Aid you can put on a horn CD combo to reduce the peaks that will fix the real problem. It's no different than trying to fix directivity in a speaker with EQ.

Doesn't work because it is fixed by the design just as a horn resonance and discontinuities or HOM's in a waveguide/horn or issues with the CD phase plug interacting with the horn/waveguide.

You need to take Earl Geedes approach and design a proper waveguide with a compression driver that has a compatible phase plug design to really fix this issue.

Even Earl's fix will have at least 2 of these peaks so no matter what they are not going away .

So with that said this is why I don't worry about them. I am an end user hobby guy not a designer of transducers or waveguides. As bonkers as some curves look they sure can sound good which is the bottom line for me.

Rob:)
 
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Hello,

While I am sorting the M2 waveguide and the PT H1010HF-1 waveguide. I am listening to 3-way + sub speakers; 2204 woofers, 2119H mids and 2344 waveguides + 2425H tweeters. I am guessing that the directivity is gently increasing with the 8 Inch cone mid-range and crosses over to match the DI of the 100 X 100 2344 waveguides. That is the goal, to be confirmed with test.

I really like what I am hearing. Dave Brubeck on original vinyl has a clearly dimensioned sound stage in my small listening room.

Thanks DT
 
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yes, excellent choice on the 2204.
Good to hear you have some enjoyment.

I imagine (and would bet) either pt is way better than the 2344, and I'm not positive.
I think the newest pt is even better.

M2 ?

My money is on the newer or older pt (so far as horn reflections especially at the mouth), but odds may be too close to call.

Norman
 
Hello DT

Your set up sounds like a good choice of drivers. I basically did something very similar except I had a 10" as my mid and the directivity was matched at the crossover point and it sounded really good imaged great with an imperceptible transition between the 10 and the 2344. Curious to see how your comparison goes.

Hello Norman

I imagine (and would bet) either pt is way better than the 2344, and I'm not positive.

You would be surprised how good an old design like the 2344 has held up. Especially crossing it over almost an octave higher than in the 4430. I still have my pair and one of these days I would like to get them running again. My favorite CD horn from that time.

Rob :)
 
Robh and TurnItDown:

Both of you have used the 2344a quite a bit, and still find it to be a good setup. In your opinion, how do the older 2425 drivers perform? A couple of other questions, which I hope are not too far off the path for this discussion:
1. You both comment on mids that mate up well with the 2344a...what about a 12" mid? Too big?
2. The compensation circuit 4430: does a constant directivity circuit in an electronic crossover such as the TDM brand do this same function for the 2344a?
3. Strictly for the purposes of experimentation, is there anything inherently wrong with putting a 2344a on top of a vintage speaker that has a wide range, efficient 12" woofer? I'm thinking of bypassing the stock midrange horn and crossover in that speaker, and using the 2344a, and a 2404. Not sure if the 12" woofer is a good fit. It is not going to go low in the current 3 cf box, but that can be augmented, of course.

Appreciate your input. Thanks!
 
A twelve would work great and if you use a DC300 from PE you'll get plenty 'o bass in that size cab. Bonus #1 - it's less than $50 and Bonus #2 a crossover is already worked out. Just tune the box.


PS - some actives have horn compensation, but the 2344 is a different animal as you can see by the factory crossover. If you can run some curves on the cd/horn combo, we could suss out the compensation.


PPS - you'll just have to work out the box tuning. That woofer should play pretty well sealed too.
 
Hello

2425's are just fine IMHO. I use them in 4344 clones and they sound just fine. As far as a 12" no real issue look up the 4425 monitor.

Use the stock compensation network as a canned curve won't work as well. Now if you have DSP then you can dial it in.

The 2425 and 2344 run out of steam at about 17 Khz or so. I used them without and added tweeter. Sounded fine by me.

If you go with a 12 try to match the directivity at crossover so I think the 4425 used a 1.2K crossover point as a ballpark figure.

1985 4425

Rob :)
 
TurnItDown and RobH: Thank you for those comments. Just to clarify, does the 2344a require to the compensation curve to get to 17khz? And, no, I cannot hear that high any more. Used to have tested hearing in excess of 20hz, but nowhere near that now. However, I have the JBL 2404's, and maybe someone else can hear them........

I'm going to look at that woofer you suggest too. The stock woofer is an alnico magnet, 100 db per 1 watt jobbie. Actually sounds pretty good. In this vintage speaker, they ran them full range in some cases. I'd like to play around with various crossover points to the 2344a, which can be done with my active crossover.

The cabinet is 3.14 cf internal. I was thinking of turning it upside down to have the woofer closer to the 2344a which would sit on top. Does this make sense?

I'm really liking this idea, because I want a pair of speakers that give me an excuse to go pick up a nice tube amp. Maybe about 100 watts.

Thanks!
 
does the 2344a require to the compensation curve to get to 17khz?

Yes take a look at the spec sheet it's a true CD horn.

2344

The stock woofer is an alnico magnet, 100 db per 1 watt jobbie.


Are you doing active or passive crossovers?? If your woofer is 100Db you may have an issue using the stock 4430 compensation. It's a passive compensation and it bleeds off midrange sensitivity. It was designed to work with a max sensitivity of 96db 4435. May be OK but something to think about.

Rob
 
I have a two way with 2206 woofers and 2344/2426 combo. Works quite fine. I can't remember the crossover frequency that I used with it. It was somewhere between 1000 Hz and 1200 Hz. I must have a look at the DSP config that I used with it.
But I must also say that a more modern waveguide sounds better to me (my purely subjective perception of course) and therefore the JBL combo is currently just used as a "plinth" for the newer speakers:

Two way with PA drivers

I wonder how much that 2344/2426 combo would be worth. I bought them new in 1998 and they have less than 100 hours of domestic listening on their voice-coils.

Regards

Charles
 
Newest pt square waveguide (pth 1010hf-1).
 

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