Crossover design

[F456GTM]

Hello Chaps,

What criteria is taken into account to design a simple crossover?

I would like your help in order to build a crossover, using a 12db Butterworth filter at 1.35 kHz, for the following drivers:

Low Frequency Driver: Altec 416-16Z
High/Mid Frequency Driver: Altec 806A
High/Mid Frequency Horn Model: Altec H-811B

I can assemble it but I do not have the technical expertise to design one.

Cheers,

 

[Folsom]

Can you take measurements once it's assembled? If not then you'll have poor results.

 

[F456GTM]

If someone tells me the values I can do that, I have a multimeter.
Thanks

 

[Folsom]

That won't help. You need to build the speakers and measure each driver individually with a microphone that's calibrated. A driver measuring device would be good, too.

I know you said, "simple" but when is anything with speakers truly simple? For a two way if you can match natural rolloffs that are similar in frequency then a 6db crossover is fairly easy if you indeed want simple..

 

[F456GTM]

Sorry, I should have been more clear. I have a 16 Ohms pair of Valencias in mint condition. They cross at 800 Hz but people who used a dbx DrivePack P2 loudspeaker management system got good results at 1.3KHz. The problem is that I do not want anything like that, not even a DSP mini switch. I have a simple all analog system.
Cheers

 

[DonH50]

An Internet search would help... Here is one example schematic of the N801 Altech used: http://www.audioheritage.org/vbulletin/showthread.php?37292-rebuild-of-Altec-N-801-crossovers

HTH - Don

 

[F456GTM]

I have the Altec crossover and the schematic diagram, it crosses at 800 Hz.

First of all, a crossover is designed from the ground up and built to crossover at a specific frequency.

You can not just go and change the crossover frequency at 1.3KHz

 

[Folsom]

Do the people that tried 1.3khz have good measurements that you can share with us? That would be a start.

 

[DonH50]

Sorry, I did not calculate the old crossover frequency, just found some pictures and was hoping it would match what you need. You can adjust the frequency by changing the LC (and R if present) values but need to know the driver impedances to dial it in. I assume you also need the attenuators to match the relative output of the two drivers. 1.3 kHz seems kind of high but whatever.

Would you be interested in an analog active crossover which would allow you to use two amplifiers to biamp them, or you just want someone to calculate the values for a new passive crossover at 1.35 kHz? It sounds like those who have done this have dialed it in with an active digital (DSP) design but you could use an active line-level analog crossover like the dbx 223xs.

Criteria other than frequency response include power handling and control flexibility (e.g. the ability to adjust relative output, typically to reduce the output of the tweeter to match the woofer).

If you just want component values it would take a bit of time to grunge through the equations and simulate the design. Likely many members here could do that but it may take a day or two (not to run the math, to find the time to run the math -- e.g. I am pretty busy these days).

Can you post your schematic? Better to have a known starting point.

 

[F456GTM]

Thanks Don. As I mentioned in a previous post, I have a simple system, a pair of QUAD ESL-63, my third pair in 55 years, Electrocompaniet DMB-100 Anniversary limited edition, Klyne series six, Technics SP 15/Audio Technica ATP-12T/Denon DL-103R - Thorens TD125/SME 3009/Ortofon MC 30 Super MkII. I also have a Meridian 507 DC player but rarely use it.

I attached Scott Freimann's article. He says that "After several days of listening tests it was determined that 12db Butterworth filters at 1.35 kHz rendered the best overall tonal quality, while almost seamlessly blending the horn and woofer into one".

https://www.audiophilenirvana.com/a...ews/altec-lansing-valencia-improving-classic/

PS: DBX 223xs: will not an extra active gain stage add more noise and distortion?

 

[DonH50]

Thanks Don. As I mentioned in a previous post, I have a simple system, a pair of QUAD ESL-63, my third pair in 55 years, Electrocompaniet DMB-100 Anniversary limited edition, Klyne series six, Technics SP 15/Audio Technica ATP-12T/Denon DL-103R - Thorens TD125/SME 3009/Ortofon MC 30 Super MkII. I also have a Meridian 507 DC player but rarely use it.

I attached Scott Freimann's article. He says that "After several days of listening tests it was determined that 12db Butterworth filters at 1.35 kHz rendered the best overall tonal quality, while almost seamlessly blending the horn and woofer into one".

https://www.audiophilenirvana.com/a...ews/altec-lansing-valencia-improving-classic/

PS: DBX 223xs: will not an extra active gain stage add more noise and distortion?

I did not see the Quad's listed in this thread, just the Altec drivers? The Quads are nice, heard them many times in the past. No point in listing my gear, not WBF-worthy.

All components add noise, active add distortion (passive too but negligible in this application), but likely swamped by your speakers (even for the legendary Quads). It's a pro unit and is very quiet with gobs of headroom (thus low distortion) in a consumer application. You would need separate bass and treble amplifiers, however.

IF the crossover is the same as the schematic in the link I posted, then it is a second-order (each for bass and treble) with corner frequency fc = 1 / (2*pi*sqrt(L*C)) = 1 / (2 * pi * sqrt(2.2e-3 * 18e-6)) = 800 Hz as expected. There are lots of solutions but I'll use the same inductors on the theory they are harder to find. Now reworking the equation to find a new capacitor value for fc = 1.35 kHz:

Cnew = 1/ (fc^2 * 4 * pi^2 * L) = 6.32 uF (check my math).

So, for a first pass, replace the 18 uF capacitors with 6.32 uF non-polar caps of the same voltage rating and see how it sounds. It may be hard to find 6.32 uF; you can use a 6.2 uF in parallel with 0.1 uF (or 0.12 uF) for each capacitor.

HTH - Don

 

[Leif S]

Hello Chaps,

What criteria is taken into account to design a simple crossover?

I would like your help in order to build a crossover, using a 12db Butterworth filter at 1.35 kHz, for the following drivers:

Low Frequency Driver: Altec 416-16Z
High/Mid Frequency Driver: Altec 806A
High/Mid Frequency Horn Model: Altec H-811B

I can assemble it but I do not have the technical expertise to design one.

Cheers,

If you call me I will walk you through the challenges and then you can decide what direction to go from there. I believe I still have the parameters for those drivers. if you give me the dimensions of the enclosure I can simulate the impedance curve and phase then simulate a crossover that can truly integrate the drivers. I will check and see if I still have the frequency response curves in my library from my old Altec mods.

 

[Leif S]

If you call me I will walk you through the challenges and then you can decide what direction to go from there. I believe I still have the parameters for those drivers. if you give me the dimensions of the enclosure I can simulate the impedance curve and phase then simulate a crossover that can truly integrate the drivers. I will check and see if I still have the frequency response curves in my library from my old Altec mods.

Long story short.....
You need five things to make a crossover become one with the drivers. Frequency response measurements, phase of the FR, impedance curve and phase along with the acoustic centers. Without those, the speaker will never be right. Sure you will get sound but there won't be integration.

 

[Leif S]

That won't help. You need to build the speakers and measure each driver individually with a microphone that's calibrated. A driver measuring device would be good, too.

I know you said, "simple" but when is anything with speakers truly simple? For a two way if you can match natural rolloffs that are similar in frequency then a 6db crossover is fairly easy if you indeed want simple..

Altec drivers don't work well with first order circuits. Not enough parts to get a linear frequency response or have good driver integration.

 

[Folsom]

Well what I noticed is a first order would work on either driver, but not with each other.

 

[F456GTM]

Hi Leif,

Thank you for your kind offer, I love music and stereo equipment but I know little about audio electronics.

The Valencias were built that way, with the advantages and disadvantages of the breed. I do remember some of the classics, EV Patrician, Jensen Imperial, JBL Hartsfield, Tannoy GRF... They were easy, more natural, more mids, often (but not always) a better sense of detail an depth, more of the rich sound that characterized the things I grew-up with. Imaging suffered in the old ones, especially the behemoths. No attention was paid to items like phasing, diffraction or time alignment. Grille cloths were occlusive.

There is no perfect loudspeaker. I think that I will be better off leaving the crossovers alone, very complicated for me.

Once again, thanks much.

Horacio

 

[DonH50]

As Leif said, 6 dB (first-order) is rarely used, and what little data I have shows Valencia to use second-order high- and low-pass filters.

Crossovers themselves can be a big effort, let alone figuring out how to make the entire system work together. Much easier with a DSP. And a lot of expertise I don't have.

Many times I have dredged up beloved old XYZ this that or whatever and have been sorely disappointed and disillusioned in what I considered "best" in its day.

Life goes on, as does the music! - Don

 

[bonzo75]

Hi Horacio, why don't you ask on the DIY audio forum Altec Lansing section

 

[Leif S]

Hi Horacio, why don't you ask on the DIY audio forum Altec Lansing section

I don't know about that lol. I've read a ton of post on that forum and there is some crazy s**t. Also, these guys suffer from a known physcosis that convinces them what they have done is the best thing ever. I would only make a change if someone has measurements to back their modification before you dump money into this. But you can't just change the value of one part. They all work together and if you change a cap value, the inductor will have to change as well on both the high pass to the HF driver and the low pass on the mid board. This can be a lot of fun for him but he really needs a program to measure frequency response.

 

[DonH50]

For the record, the crossover schematic I had and showed was symmetric second-order sections, same LC values for LPF and HPF, just reoriented in the circuit to accomplish the desired filter function. That is a valid configuration. I proposed changing both caps, changing the pole and zero symmetrically with a single component value change (to two components). That will change the crossover frequency and maintain symmetry. Not the best approach, but since the OP clearly was not going to run the equations and do the simulations himself, it was an easy thing to try.

If that was not the right schematic, all bets are off.

Of course knowing more about the components (crossover and driver) and doing the full-blown analysis is better. All I was trying to do was provide something that would be close if he wanted to just swap the caps and see.

I have not listened to an old Altec system in years but IIRC driver integration was not that great to begin with compared to today's better speakers... Integrating a horn and a cone can be tricky, and it still seems like 1.35 kHz is driving the woofer pretty high, so I wonder how distortion and dispersion will be impacted.