AL170 and G25FFL in bass reflex box

[mcl2k6]

Hello all,

I'm following UweG's advice, to open a topic on this.
I've been tinkering for some time now on a loudspeaker using the AL170 and G25FFL+WG combination.
Until now it is quite interesting as far as I can tell.
Originally it was an all-3rd-order crossover.
Recently I had some ideas to turn back to all-2nd-order, as I had the feeling that it sounded better.
Here would be some graphs from the simulator, the project file, and an on-axis Arta measurement (BOX_R_current_2nd_order*).

Then, after reading some info about the energy frequency response, I've made some possible tweaks (BOX_R_current_2nd_order_tw5uf_variant*).

Any comments?

[Willy_65]

I think 2 things require more attention:
- the impedance of the box must probably be 4 to 8 ohms, whereby the oscillation must be reduced to the best possible.
- the crossover frequency must not be below 2 kHz if you want the tweeter to last longer.

To start with, I have added a series RLC network (15 ohm + 22 mH + 220 µF) which smoothes the resonance peak at 60 Hz to an acceptable impedance.

Then I added a parallel LRC network (0.47 mH // 4.7 ohm // 33 µF) which is also used in the Couplet of Visaton with almost the same speakers, well with 1 x AL170-8 instead of 2 v AL130-8. This helps to better straighten the characteristics, while striving for an optimal crossover point, namely 2500 Hz. (The nominal frequency response is specified by Visaton as 2 kHz to 30 kHz. If you allow the tweeter to be taken over from the AL170 before the 2 kHz limit, you are going to load it more than what it was designed for.

Then I let go of the optimizer, which already gave a good result. Then adjusted a value here and there and achieved a fairly good result.

[ubix]

..

[jama]

@ Willy der G25 muss umgepolt sein...

(weiche zu kompliziert)

[jama]

@ ubix , trenne der G25 eher bei 2,2 kHz

mundorf luftspulen

[Willy_65]

@ Willy der G25 muss umgepolt sein...

(weiche zu kompliziert)

Das Netzwerk des AL170 ist nicht 3. Ordnung sondern 2.?
Bei 2x Netzwerk 2. Ordnung werden die relevanten Lautsprecher mit der gleichen Polarität angeschlossen.
Das RLC-Netzwerk macht das Netzwerk 2. Ordnung nicht zur Netzwerk 3. Ordnung, sondern wirkt sich nur auf die 60-Hz-Resonanzspitze aus.
Siehe unten, wo das RLC-Netzwerk getrennt ist:

[jama]

der G25 bleibt trotzdem falsch verpolt in deiner simu...

[UweG]

Hello mcl,

as I gave you the recommendation to open a new thread here, I'm a bit confused about the comments you earned. I did not expect that.

In my opinion, both of your simulations promise a well-sounding seaker. There is nothing completely wrong with them. If you want to compare similar designs made by VISATON, you may have a look at those two:
- Bijou 170 WG
- VIB170 AL

If you have a modern transistor amplifier (and not a tube amp), the impedance can never be too high. The impedance response of both of your simus is o.k. and uncritical even for a weak amp.

The discussion in german in the prior posts mostly relate to the suggestion in post #2, so I do not have to translate.

The suggestion by jama from post #5 for me is also a good design.
Jama states that it might be better to choose a crossover frequency of more than 2000Hz. I'm not sure, but I would have thought, that together with the waveguide, 1800Hz might also be possible. 2200Hz would give the G25 more reserve at higher loudness.
As jamas crossover provides an excellent match of the phases at crossover frequency (even better than your designs), it also shows best, what is the problem of the 2nd order /3rd order designs. The phase shift of the tweeter is different to the woofers. In my opinion jama did not solve the problem optimally. The 3rd order design should be at the bass. I tried it even with 4th order. This design does not run out of phase even 1 octave away from the crossover frequency.

[UweG]

One more comment on the two suggestions from post #1: If the capacitor 4µF (where can someone buy it?) is changed to 3.3µF the result is very similar to the alternative result. If you want to keep it simple, this would be my choice.

[Willy_65]

I conclude from the previous posts that the impedance is not that important unless you have a tube amp. For the last 5 years I only design and build tube amplifiers, hence my focus on impedance.
That obviously does not facilitate the design of a crossover, but to me it seemed logical that a loudspeaker box can serve both solid state and tube amplifiers.
An impedance is always given in the designs of Visaton, but I always found it strange when I looked at the curve, which fluctuations were allowed there.

In principle, I will always strive for uniform deployability in my designs, whether a solid state or tube amplifier is connected.

Regarding the phase characteristic, Uwe's design is indeed ideal. I thought mine was ok too, but maybe I don't interpret the graph correctly.

@Jama, I don't understand why you would reverse the polarity of the G25, is the first phase characteristic then wrong?

[walwal]

Yes, the First One is Not Good enough. Easy Test is : Switch the polarity of One driver, if you see a deep notch in the frequency response, it is ok. The deeper, the better.

[Willy_65]

Yes, the First One is Not Good enough. Easy Test is : Switch the polarity of One driver, if you see a deep notch in the frequency response, it is ok. The deeper, the better.

Thanks, now it's clear to me.

[mcl2k6]

Hello all,

Thanks for the answers.
I have found in several sources, that if you use a waveguide on the tweeter, it would unload it and lower crossover frequency is possible. Then, with the G25FFL there were several recommendations on another forum, which stated that it's safe to use it even at 1.5kHz. Okey, they stated that to be on the safe side, a 3rd order filter would be the best solution. However, with compromise, a 2nd order would work too.
Regarding amplifier, I have an LM3886 based one. But even with a home built tube-amp (2x6P36S, ~100W), I did not had any oscillation issues. However, it has quite significant NFB.
I've attached ARTA measurement of FR and step response for the current implementation.

I had an all-3 order design (attached BPJ, ARTA FR and step). The main scope was to kill as much as possible the horrific cone breakup of the AL170 above 5kHz. However I simply didn't liked it. The sound was somehow compressed. Although it measured well, it didn't sounded natural to me for some reason.

4uF PP you can find from Kemet, ~800V, low ESR:
https://www.tme.eu/ro/details/c4aqib...opilena/kemet/

[walwal]

Coneresonanz : a 0,33 or 0,22 or 0,47 Cap parallel to the induktor will help.

And Please forget ihr Electrical Order of an Crossover, only the acoustical Order is important. You Can check this With boxsim.

Sorry for and grammar, my Smartphone does the German one.

Your Crossover is somewhere between LR 4 and LR8, very sharp.

[walwal]

You know, Boxsim contents a Tool "optimize"?

I did this, here the result. First of all, your crossover ist very good. But, if the Energiefrequenzgang has a slope, the Box sounds too dull, therefore you should lift the frequencyresponse a little bit like the optimizer did.

My advice: look for available values for the crossover and check the simulation again. 1500 Hz ist ok for the G 25 FFL in WG. A liitle bit better will be the KE25, but more expensive.

If you look for Sonogramm, you will see at 2-3 kHz some disturbances. The reason ist Bafflediffraction. whith a smaller one it will be better. You can read also here. Good luck.

https://heissmann-acoustics.de/kante...eiberanordnun/