for its size and range, Inlow's little 8pe21 horn should really do well. FWIW in hornresp, it scales nicely at 1.2X for my JBL M151
sorry for typo on graph - I don't see well these days in old age
https://i.imgur.com/JbTbGfS.jpg
sorry for typo on graph - I don't see well these days in old age
https://i.imgur.com/JbTbGfS.jpg
time for some practice!
"We could sit around here all day, talking, making clever speeches, it's not gonna shift one Roman soldier!"
Having that on mind I realized that what I needed is a prototype... so I built one. The mouth is 28x55 cm (inner dimensions), the throat is 11,5x12 cm, inner lenght 41 cm. I didn't get 8PE21s yet so I thought I could try the horn with FaitalPro 8FE200 I had from some old project. The rear chamber is made as small as possible, sealed, filled with some polyfill.
I've taken the measurements. As you can see it's quite good from 200Hz to 850Hz, then it drops rapidly.
It made me think if having the intended BC driver in that horn would really be so different that I could reach 2000Hz on the upper end. Any thoughts? Ideas?
Maybe some modifications to the horn?
"We could sit around here all day, talking, making clever speeches, it's not gonna shift one Roman soldier!"
Having that on mind I realized that what I needed is a prototype... so I built one. The mouth is 28x55 cm (inner dimensions), the throat is 11,5x12 cm, inner lenght 41 cm. I didn't get 8PE21s yet so I thought I could try the horn with FaitalPro 8FE200 I had from some old project. The rear chamber is made as small as possible, sealed, filled with some polyfill.
I've taken the measurements. As you can see it's quite good from 200Hz to 850Hz, then it drops rapidly.
It made me think if having the intended BC driver in that horn would really be so different that I could reach 2000Hz on the upper end. Any thoughts? Ideas?
Maybe some modifications to the horn?
Attachments
Thanks, Turk.
"Phase plug route" - that's will be the last resort
I think I install a vertical piece of mdf to shut the throat completely but with a circular hole of 8 cm (diameter) and then try to fill (with some clay or something) the space between the new throat and the horn walls - to make a smooth-ish transition.
"Phase plug route" - that's will be the last resort
I think I install a vertical piece of mdf to shut the throat completely but with a circular hole of 8 cm (diameter) and then try to fill (with some clay or something) the space between the new throat and the horn walls - to make a smooth-ish transition.
Having some spare time I came with an idea of making more measurements, using drivers I had. One of them, Seas ERX18, ended with a quite nice response curve. As you can see pretty good from ~200Hz up to 5k. Playing music with that combo that's another story Much worse than 8FE200 which measured way worse...
Another example of that common wisdom saying that there's quite a long way from good measuring driver to good sounding speaker...
Much worse than 8FE200 which measured way worse... Another example of that common wisdom saying that there's quite a long way from good measuring driver to good sounding speaker...
Attachments
Yep, I was searching for the suitable drivers for some time and decided to go for 8''. Another very good one was one of the 5'' faitals but I read lately very long thread by LewinskiH01 and, despite of building 4 or 5 prototypes, he couldn't achieve the desired response. So I decided to quit five-inchers... I just have a feeling that going down to 250Hz would be easier or better with a bigger driver.
GM,
Thanks for the formula, I didn't know that as well.
To clarify my approach: I don't have any solid believes on how big the drivers should be. I'm just looking for the most suitable driver for the given range. So if 6,5'' drivers can do better than 8'' I'm ready for change.
The problem is my very limited experience with horn speakers therefore I would like to rely on some reliable, well-regarded projects. If there are ones for that FQ band...
Thanks for the formula, I didn't know that as well.
To clarify my approach: I don't have any solid believes on how big the drivers should be. I'm just looking for the most suitable driver for the given range. So if 6,5'' drivers can do better than 8'' I'm ready for change.
The problem is my very limited experience with horn speakers therefore I would like to rely on some reliable, well-regarded projects. If there are ones for that FQ band...
Does this mean you are using minimalist crossovers + EQ on your prototype?
Nice.
Pretty smooth, too. That would be good with minimal EQ.
I came with an idea of making more measurements, using drivers I had. One of them, Seas ERX18, ended with a quite nice response curve. As you can see pretty good from ~200Hz up to 5k. Playing music with that combo that's another story
Another example of that common wisdom saying that there's quite a long way from good measuring driver to good sounding speaker...
Note: you used different scales for the measurements, so they are hard to compare at a glance.
If you are using simple EQ, the subjective comparison may not be "fair".
e.g. with a low order crossover, the Seas will be about 10dB louder in the 2-4kHz range. It will overlap a lot more with the HF driver.
I think it is hard to say - unless you've found measurements of the driver in a horn. The Inlow 135Hz horn uses this driver - but only to 500Hz, and no measurements are given - so that doesn't tell you anything about the HF response.
Many spec sheet values, like Qts and Qes (related magnet strength) appear to have no value at all for predicting HF performance. See link. One of the 4.5" drivers I used was defective (weak magnet), but the HF response didn't change.
Midrange (cone driver) horns; low relevance of magnet strength and Qts
In my experience, a less symmetric throat can give smoother HF.
You could try putting scraps of foam onto the mounting plate to break up the symmetry of the gap between the cone and the horn throat. This might fill in some of the HF notches you measured with the 8" Faital.
When you go from prototype to final build, you could try making the throat taller / less square, eg 10.5x13 instead of 11,5x12.
No.
Fc = the theoretical optimal [reactance annulled] tuning of the compression driver, i.e. the mean sound power point between Fl-Fh; IOW the 250-707.1 Hz and 707.1-2 kHz BW each have the same 1.5 octave spread.
This WL is then used to determine the theoretical optimum effective piston diameter.
Note that ideally the driver Fs is at/slightly below the intended pass band, so the aforementioned B&C 5MDN38 is to the first approximation a theoretically excellent choice with its 240 Hz Fs.
GM
You're welcome!
Well, a smaller driver works better up high and vice versa and why we try to average out the variables, but this isn't 'cast in stone', just a good rule-of-thumb; the driver's specs, HF performance is what's important, you just have to be careful not to have too high a compression ratio or its HF performance will suffer.
Historically the bands were 300-500-800-1200 Hz-up with [multiple] compression drivers, it's only been in recent decades that pro/cinema sound has moved to three way systems with the main ones I found being 350-500 Hz, 1.2-2 kHz BWs, which looking just now at JBL, they use a sealed back 6.5" [195H] in the mid horns, so nice to see that while I may be 'vintage', I'm not completely obsolete [yet].
Unfortunately, couldn't find any specs, but doubtful it will work at 250 Hz, so guess at this point, best to go with a 6.5" if you can find one with good enough specs.
No clue whether there's any "reliable, well-regarded projects" for you to copy, my 'horny' interests lay only in Synergy concept [MEH] horns since circa '99, though still piddle with vintage two ways.
GM
GM - re:195H - wonder how close it is to the Eminence Alpha 6 - ?
Eminence Alpha-6CBMRA 6-1/2" Ferrite Sealed Back Midrange Speaker Driver
here's an Eminence sealed back 6.5 on a JBL 6.5 WG. I never got back to it to figure out a good highpass - it looked pretty steep with just a 12uF cap
https://i.imgur.com/UcRtZtc.gif
Eminence Alpha-6CBMRA 6-1/2" Ferrite Sealed Back Midrange Speaker Driver
here's an Eminence sealed back 6.5 on a JBL 6.5 WG. I never got back to it to figure out a good highpass - it looked pretty steep with just a 12uF cap
https://i.imgur.com/UcRtZtc.gif