The EV HR9040 is a real interesting horn, and I have alwas wanted to try a pair - but the documentationQuote:
Originally Posted by gibber
(http://www.google.no/url?sa=t&rct=j&...PZDIVMP5yb2DGw)
states that the horn throat is only 1.3".
How does this match up with the JBL 1,5 inch throat?
Have you done any modifications?
Best,
Espen
Hi Ralph,Quote:
Originally Posted by gibber
But pay attention that this is 2inch throat, without any stencil in the horn throat, so 10kHz is very good, from my experience.
Using the horn driver combo from say 700Hz and up, I think is OK, especially if 4th order hi-pass is applied.
Regards
Ivica
Hello,
here's some more info on this project as it unfolds.
The Woofer will be the same one that I was previously using, i.e., the Fostex FW405N (http://www.fostex.jp/products/fw405n/)
This is a modern woofer of recent design, with a hybrid cellulose+carbon fibre cone and a newly developed aluminum die-cast frame based on FEA.
Magnet is ferrite, and sensitivity is medium-high at ~93 dB/W(m).
The features that attracted me were:
(i) Medium Efficiency Bandwidth Product (EBP) = Fs/Qes = 56.
This allows the use of an overdamped bass-reflex box characterized by an almost 12dB/oct initial roll-off and associated low Group Delay, while still obtaining an F-3 of approximately 40 Hz in anechoic conditions (which leads to a nice almost flat response in room, given the typical Room Gain over the last octave).
Also note how the excursion is contained under Xmax down to 20Hz with 130Wpc in input.
Vb = 2 * VAS * Qt^2 = 180 L
Fb = 0.39 * Fs/Qt = 23 Hz
Attachment 75797Attachment 75798
(ii) Very low mechanical damping = Fs/Qms = 4.0.
This, in my experience, is a recipe for excellent low-level detail retrieval. In other words, the woofer sounds good and does not mask or smear micro-details also at very low SPLs.
By way of comparison, this is roughly the same mechanical damping as that of the TAD TL-1601a (Fs/Qms = 4.1), while only slightly higher than that of the JBL 1501AL-2 used in the flagship Everest DD67000 system (Fs/Qms = 3.7).
Instead, it is HALF of that of the more PA-oriented JBL 2226H (Fs/Qms = 8.0) and of that of the venerable JBL 2235H (Fs/Qms = 7.9).
(iii) Extremely low distortion.
The levels of 2nd and 3rd harmonic distortion are amongst the lowest ever measured by the German magazine "Hobby-Hi-Fi":
< 0.1% at 90dB(1m) all the way down to 20Hz (measured on an infinite baffle).
Attachment 75799
In my current speakers, I am using the Fostex T925A ring radiators (http://www.fostex.jp/products/t925a/).
For this new endeavour, however, I decided that I wanted to try and stay with Beryllium diaphragms all the way to the very top of the frequency range.
I therefore located and purchased a pair of Pioneer PT-R7 III
(http://audio-database.com/PIONEER-EX...t-r7iii-e.html)
This is an extraordinary ribbon tweeter which is unfortunately no longer manufactured.
It features a Beryllium diaphragm loaded by a short front horn machined from solid aluminium, and a massive AlNiCo magnet, resulting a sensitivity of 97dB/W(m) and an outstanding frequency response that reaches out to 120 kHz (!).
Attachment 75800
The associated Impulse Response, calculated by way of reverse Fourier transform using the published frequency response (unfortunately, I do not have access to a microphone that is linear beyond 20 kHz) is very clean and "fast", as expected:
Attachment 75801
For the Woofer-Mid crossover, I got inspiration from the design used by Pioneer in their TAD/Exclusive monitors
(e.g., http://audio-database.com/PIONEER-EX...del2402-e.html),
and later reprised by Shozo Kinoshita in his Rey Audio monitors
(http://www.reyaudio.com/large-e.html),
which is based on an asymmetrical 6th-order electrical low pass / 2nd order electrical high pass, with both drivers down -6dB at Fx.
In my case, the chosen crossover frequency is 600 Hz, so as to stay approximately one octave above the horn's cut-off.
When both the Woofer and Mid are connected with positive polarity and the Mid is physically set back so as to create a suitable offset between the two acoustic centres, this crossover results in the emissions of both drivers to be in phase over a relatively wide frequency range around the crossover frequency, as can be seen in the figure provided. As further proof of the excellend phase match, when reversing the polarity of the Mid, a deep notch at Fx is observed.
Attachment 75802
This type of crossover is handy in several ways:
(i) the front-to-back offset allows the convenient positioning of the horn-loaded mid atop the Woofer box without requiring any form of delay (be it analogue or digital);
(ii) the same offset also results in the two impulse responses to be almost perfectly 'time aligned', i.e. both traces leave the horizontal line simultaneously;
(iii) the 6th-order low pass effectively does away with any unwanted resonances at the top of the woofer's operating range.
Two woofer section will adopt a balanced topology to reduce crosstalk with the mid and tweeter sections, and the compression driver will be attenuated with the Fostex R100T autoformer (http://www.fostex.jp/products/r80br82br100t/), whose 8 Ohm shunt resistor also handily leads to an almost perfectly level 8 Ohm impedence.
For the second crossover between Mid and (super)-Tweeter, I opted for a simple symmetrical 2nd-order "Constant Power" design at 7kHz, with both drivers down -3dB at Fx.
Inevitably, given the short wavelengths at play and the physical separation between the acoutst centres, the super-Tweeter will not be time-aligned.
However,
(i) this was not deemed important at such high frequencies, where the human auditory system's sensitivity to phase is reduced;
(ii) the resulting comb filtering between the Mid and Tweeter outputs falls within the Equivalent Rectangular Bandwith (ERB), and is thus essentially inaudible.
Greg Timbers also seems to agree on this, as he said:
"The comb filter effect is normal and cannot be eliminated, even with the use of electronic delay. [...] In spite of the curve, we have had no negative comments about the 045Be and the choppy response through the crossover range"
Additionally, having an intentionally misaligned constant power crossover at such high frequencies results in a 1/6th octave-smoothed summed response that is essentially invariant over a +/- 30 degree listening angle, since any additional misalignment introduced by moving the head laterally is swamped by the >360 degree original misalignment.
Attachment 75803
Finally, the resulting modelled impedance curve of the complete system is very flat and with only moderate phase angles throughout:
Attachment 75804
...MORE TO COME! :-)
Hi Espen,Quote:
Originally Posted by jerv
it almost doesn't matter if you insert an adaptor or not. The HR series even has ex-factory that three hole mounting arrangement for the Altec 1.4" drivers of the time. Invitation for users to create a 2.5mm mismatch.
For fear of nasty visitor comment i wouldn't dare a permanent install of a 1.5" without a conical flange piece, but truth be told i never saw a significant effect, just a bit of ripple here or there, sometimes even smoothening a response taken with the "correct" transition fitted :confused:.
EV published measurements of even more gross throat size mismatch in one of the "PA Bible" articles as a quick fix guide for roadies during perfomances. Check it out.
Ralph
Yes, agree this will work from 700 if x/o steeply, and "upstairs" the Be ribbon will help to offset matters.Quote:
Originally Posted by ivica
Have you ever compared "same" motor in two exit versions, say 1.5 and 2.0 inches for >10 kHz Response?
My guess would be that say, a 2450SL 1.5" should perform the same way than a 2450 2". After all, both drivers would see further expansion into the horn they are bolted to. With the 2450 having part of that expansion bolted to it's magnet ex-JBL already.
In that sense, the smaller 1,5" exit could only possibly bring a benefit in extension >10kHz, if the horn accepts 1,5" and then rapidly expands (such as the PT Family or the 2352/2353 horns).
What do you think?
Hi gibber,Quote:
Originally Posted by gibber
From my experience with 2450-2" and 2450-1.5", applied to the almost the same horn, but with proper horn throat relative to the used driver ( 2" or 1.5") have shown that I have got +/-30 deg.off-axis dispersion up to the 10kHz with 2" driver, but about 14kHz when 1.5" driver is used.
In the horn throat is have been applied pi/4*D ( D=2" or 1.5") vertical size reduction ( like DD66000 horn as an example, or 2328 adapter).
From the mentioned experiments I can say that +/-30 deg.off-axis dispersion can be get up to the frequency calculated as: 34500/(D*pi/4)*1.2, where D is in [cm] is driver output diameter.
regards
ivica
So Ivica,Quote:
Originally Posted by ivica
doesn't that basically bring down the argument to that of slot size (rectangular or circular "slot") for being the source of the better dispersion?
Quote:
Originally Posted by ivica
The above arrangement of size reduction is perhaps also relevant to Espen's concern: it happens all the time! Look at how the original HR9040 throat reduces the 33mm entry to just 28mm as a matter of a few millimetres of pathlength into the horn (now oval-looking):Quote:
Originally Posted by jerv
Attachment 75833Attachment 75841Attachment 75831
(Source: http://www.diy-audio.narod.ru/litr/K..._Exp_Horns.pdf)
Attachment 75832
The above Keele reference lists a P.W.Klipsch 1945 (filed) patent that was commented on here to the effect that (i paraphrase) First, expansion is only in at single plane for a part of the length to bring radiation angle of the horn up to desired target in this plane; 2nd, expansion takes place at right angles to said 1st plane while continuing to expand in the angle reached in the first expansion. Expansion stops where targeted mouth area is reached.
So, all horn designers do what they please and place "obstacles" at will in order to get their designed pattern
Ralph
Hi Ralph,Quote:
Originally Posted by gibber
Such throat size reduction can be seen on M2 horn too, as 39mm throat has been reduced (partially ) to round about 19mm in order to involve diffraction in the horn throat so HF off axis dispersion woild be enhanced over +/- 45 degs.
Regards
Ivica
At last I found the time to work on the crossovers, and to assemble the system.
A couple of pictures below.
Keen observers will notice that I reverted to my tried-and-trusted Fostex T925A "bullet" tweeters.
In-room measurements and listening impressions will follow...
Attachment 75946Attachment 75947
Here's the system's FR measured from the listening position, superimposed on the target described in Olive et al., 2013.
Attachment 75948
The L/R differences below the room's Schroeder frequency (Fc) are mostly due to the fact that the left speaker is closer to a side wall, and hence gets more boundary reinforcement. But notice the excellent linearity of +/-dB all the way from ~300Hz to 20kHz.
Cheers,
M.
Hi Marco
the setup looks good! Kids (2..4yrs), or a cat in the home? Would look even better (i think) without the grille in front of the 38cm unit, but with cats...
Change of plan: why did you choose to go for the Fostex T925 instead of the TAD/Pioneer Be-Ribbon? I have 3 different pairs of them. The PTR version you have is less simply made and even more powerful than the high-reputation PTR-9. Yours has 4 of the 7 Alnico cylinders used in early TAD TL-1601B (later 1601B has very different magnet). I'd like to see any comments on sound/usable range/etc before putting in my €0.02. Posts/comments on T825 (which i believe uses the same fram as T925) at the end of this very interesting (one of my fav) threads.
Ralph
Hi Ralph,Quote:
Originally Posted by gibber
yes, there's a cute 2.5-yr old at home... ;-)
As for the tweeter, the Pioneer ribbon is surely a great product in and of itself. However, it seems as if it was really primarily meant as a SUPER-tweeter, to be used as an "add-on" to an already "complete" system, to supplement the ultrasonics (>20kHz).
When instead using it as a tweeter crossed over lower (7kHz in my case), I found that its frequency response is a bit ragged in the stop band (which causes issues with the passive crossover), and then it slopes down beyond 10kHz, becoming approximately -5dB at 20kHz (the upper frequency limit that I can measure - but the Pioneer then goes on and on... till over 100kHz!).
Instead, I measured the Fostex tweeter as almost perfectly flat from 3kHz to 20kHz, which makes filtering it a breeze, and then it is also much more efficient, which subjectively makes for a better dynamic match for the compression driver below.
Oh well, you live and learn...
Cheers,
Marco