Optimal crossover points for a 4-way active loudspeaker for home use ?

[Tangband]

My suggestion for a loudspeaker without compromises for home use , using Linkwitz Riley active crossovers with 24 dB/oct slopes, is like this :

3/4 tweeter without waveguide 4000 - 20000 Hz
3 inch middriver 300 - 4000 Hz
6 1/2 midbass 80 - 300 Hz
12 inch subwoofer 15 - 80 Hz

Would you use different crossover points, or different sizes of the drivers ? Of course everything depends on each driver….

I would also use a rather wide baffle , 38 cm wide to get away without baffle step compensation down to the 3 inch drivers crossover at 300 Hz.

 

[thewas]

3/4 tweeter without waveguide 4000 - 20000 Hz
3 inch middriver 300 - 4000 Hz

In above case probably different drivers, crossover frequencies or waveguides, the 3" mid beams already at 4 kHz* while the small tweeter doesn't, without WG I would rather use a 1" tweeter crossed around 2-2.5 Khz to the 3" mid, if you want to use a 3/4" tweeter you mid consider a 2" mid driver.
As this also depends on the baffle I would recommend you to use the Boxsim simulation software as it already has all drivers from Visaton and considers also their directivities and baffle sizes to find some optimal configuration as your first iteration (you experiment and measure then with drivers similar to the Visaton ones from your simulation).

*Above ka = 1, a directional effect begins to emerge (and also other problems), so one should separate here. This is the wavelength normalised to the circumference, i.e. the wavelength corresponding to the radiator circumference. The basis for calculation is the effective radiator diameter, i.e. cone diameter + half bead. Accordingly, one can use for a wide relatively constant directivity without a waveguide

15" cone: up to approx. 300Hz
12" cone: up to approx. 400Hz
10"-cone: up to approx. 540Hz
8" cone: up to approx. 650Hz
6.5" cone: up to approx. 800Hz
5" cone: up to approx. 1200Hz
4" cone: up to approx. 1500Hz

With dome radiators the directivity starts to increase a little later (by ka = 1.5), but then more strongly. According to this

3" dome: up to approx. 2200Hz
2" dome: up to approx. 3300Hz
1.5" dome: up to approx. 4400Hz
1" dome: up to approx. 6600Hz
0.75" dome: up to approx. 8800Hz
0.5" dome: up to approx. 13.2kHz

 

[DVDdoug]

It depends on the driver specs but 80Hz seems a little low for a 6.5-inch and 300 seems little low for a 3-inch. But that also depends on the loudness. A 6.5-inch speaker can probably put-out something at 80Hz.

 

[thewas]

By the way if I were you, I would ask the mods to move it to the DIY section where you might get more expedient responses.

 

[thewas]

My suggestion for a loudspeaker without compromises for home use

By the way everything is a compromise, for example in your case since you don't use waveguides and coaxial drivers the directivities, I have DIY engineered myself a similar wide radiating 3+1 way system and while its not bad it cannot compete in terms of engineering and sound quality with the top products of the pros like Genelec, Neumann, KEF, Revel etc., this comment is to avoid disillusionment when finally reality strikes hard at it always does.
Another choice is that someone might need different designs for different listening distances, room acoustics, stereo vs. multichannel, max SPL etc, so there is not the single one optimal loudspeaker but only the one that fits the corresponding demands, needs and tastes well.

 

[Chrise36]

I would try the Purifi Mid from 200-250 hz and use an AMT or compression driver to start as low as possible.An 8 inch from 50-60hz. Which 12 inch have you found that will work reasonably from 15hz.

 

[gene_stl]

For my large, home built, active speakers I used the following specs: 12 db/octave LR. (Pioneer D-23 four way electronic crossover)
4x Yamaha 33mm tweeter (but with "phase ring" that has much smaller diameter. ) 5K up (Yamaha uses them down to 2K)
2x Yamaha 88 mm MidRange (ditto the phase ring, but larger) 1K to 5K (Yamaha uses them down to 500 Hz)
single JBL LE10A 100Hz to 1000Hz 1.2 cu ft sub enclosure. (JBL specs up to 2000Hz)
4x Le14A (12 cu ft sealed enclosure) Low to 100Hz (JBL specs up to 1500Hz)

I have been quite satisfied with them and the only change since building them was exchanging a blown amp driving the LE 10A (Dyna Stereo 120 with a Quad 405 in the early eighties) and adding a CD player. See intro and system linked below.

I was trying to accomplish 1) as little beamng as possible 2) reduction in driver excursion. 3) Not too many octaves of bandwidth per driver. 4) Lots of BL product. 5) Try to keep pistonic motion as much as possible.
Project done immediately after Sigfried Linkwitz paper in JAES pulished in 1976. I like four ways, or in this day and age , three ways with a sub.

 

[Tangband]

By the way everything is a compromise, for example in your case since you don't use waveguides and coaxial drivers the directivities, I have DIY engineered myself a similar wide radiating 3+1 way system and while its not bad it cannot compete in terms of engineering and sound quality with the top products of the pros like Genelec, Neumann, KEF, Revel etc., this comment is to avoid disillusionment when finally reality strikes hard at it always does.
Another choice is that someone might need different designs for different listening distances, room acoustics, stereo vs. multichannel, max SPL etc, so there is not the single one optimal loudspeaker but only the one that fits the corresponding demands, needs and tastes well.

I have built a couple of loudspeakers , but yet to build a 4 way . I have been able to listen to very expensive gear that sounds outstanding, and those have been up to 5-way loudspeakers with dsp crossovers.
As you say, everything is a compromise.
Lets say that this loudspeaker will play music in a room thats about 7 * 8 metres .

Looking at your advice, a better suggestion for a 4 - way loudspeaker with LR 24 dB/oct crossovers might be like this :

1 inch tweeter , 2500 Hz SB acoustic 26ADC
3 inch midrange , 400 - 2500 Hz Peerless tc9fd-8 or purifi 4 inch
6 1/2 midbass , 100 - 400 Hz Seas er18rnx or Purifi 6 1/2
10 inch bass , 20 - 100 Hz Seas R0y or Peerless xls 10

The needed cabinet width would then be about 29 cm to avoid baffle step compensation for the 3 inch driver.
subwoofer could be mounted at the bottom of the cabinett.

What do you think about those drivers I have suggested ?

 

[thewas]

What do you think about those drivers I have suggested ?

Those are very decent drivers, with the appropriate tuning/crossover (your revised x-over suggestions sound also like a good starting point for the iterative optimisation process) I am sure something nice can be achieved.

 

[Tangband]

Those are very decent drivers, with the appropriate tuning/crossover (your revised x-over suggestions sound also like a good starting point for the iterative optimisation process) I am sure something nice can be achieved.

Four years ago I made jbl 530 active by taking out the crossover , with two big DIY subs ( a 3 way system ) and a dbx dsp crossover . Crossover where 125 Hz and 1,7 kHz . They sounded really good, much better than the passive 530, but my 8340 is better with slightly better clarity and dynamics. The dbx crossover wasnt 100% transparent I guess.

If I would start all over again with DIY ( my last projekt was HYBRID with waveguide ) , I would buy a better dsp crossover with digital inputs and FIR ability. Such as the latest mini-dsp. My experience with waveguides are that they are really needed in 2 way speakers but the sound can sometimes be even better with many drivers and crossoverpoints not using waveguides.

 

[fineMen]

Directivity is a major concern today. Back in the day, though, engineers were aware of intermodulation. This is greatly reduced by a multi-way design.

If You have a ported bass, the relevant stress comes from frequencies above 50..60Hz, because below the port would keep excursion pretty low. To cross over too low would not take advantage of the port's benefits.
On the other hand even a 12" (30cm) midrange (18sound AIC) could become a limiting factor, if deployed too low. I came to cross over at 180Hz then.
The 12" mid I would use up to 1kHz. It gets a waveguide/compression driver (BMS 4550) on top.

Another approach is to use one or two 7" basses up to 180Hz (SB acoustics) , then a 7" lower/mid (same) up to 600Hz, then one or two 3" upper mid (Peerless TD9) up to 1,5Hz and a tweeter w/o waveguide on top. Best directivity indeed, and the tweeter would still be happy if it was a reasonable Vifa or Seas.

Both concepts were prototyped with best subjective results. I feel that the focus on reducing IM was worth it. There is air-like transparency in the often muddled lower midrange. Speech with all its subtle nuances - there is a difference.

 

[gnarly]

Hi, please take my comments as truly meaning to help...
i don't think the project you outlined makes sense.

In my mind, the reasons to go multi-way are for a combination of wanting increased SPL, and frequency extension.
Otherwise small 2-ways work.... and without all the complications and phase rotations of multiple crossovers.

So, we want more SPL and low freq extension.... enter the multi-way !
The problem with your proposal imo, is that is doesn't give much increased SPL or low freq extension vs much simpler designs.

Tweeter is too little/ too weak. Sub driver is waay too little/weak. Gotta build these up with better driver selections.
Oh, the TC9's are sweet little drivers...but honestly they are tinker toys...I've built arrays with them using dozens....

I'd suggest a robust 3-way.....18", then 12" to maybe a pair of 10/8's, then to a a robust HF/VHF section ( i like a CD on a good waveguide.)

Your project has great complication without really gaining the goal of multi-ways....which again in my mind is SPL and low freg extension.

I've built a lot of 4 and 5-ways...a good goal is to try to split the 10 audible octaves into as equal slices as possible.

Apart from sizing drivers based on the ka=beamwidth rules, it also helps to remember that displacement has to increase 4x per octave decrease, for equal SPL.
Putting the ka stuff together with displacement needs, helps define driver sizes and xover points..

 

[gene_stl]

If I was doing this today (and I am, because I am building a "timbre similar" center channel), for tweeters, I would look at the ceramic or corundum dome tweets that Parts Express carry. These are very stiff and reasonably priced. I will not use these on the center channel because I have secured a quantity of Yammy tweets.

There are a lot of 10 inch units from Italy that are much more powerful than my LE10As and I have selected one of these for the center channel. (RCF L10 510 which can eat hundreds of watts)

I have not found anything much that I like to replace the Yammy 88mm midrange. I probably will bite the bullet and buy one if I can get a single.
There is a titanium cone 3 inch at Parts express I would try. And I have seen ceramic sandwich speakers in that size range as spare parts for Revel.

One day the polycrystalline diamond drivers from Germany will come down in price. They will be made in china for nothing unless the global trade system grinds to a complete halt. They actually do not cost that much more to build than ceramic or corundum diaphragms. Or Be. They are stiff strong and light but the word "diamond" allows them to price them beyond all reason. They HAVE been seen in nice large diameters though.

In the interest of more output down low I would use multiple 12 (like four) or 15s (two or four). It depends how big your room is and how loud and low you want to go.

Don't forget speaker fuses and DC blocking caps on expensive drivers.

 

[Holmz]

My suggestion for a loudspeaker without compromises for home use , using Linkwitz Riley active crossovers with 24 dB/oct slopes, is like this :

3/4 tweeter without waveguide 4000 - 20000 Hz
3 inch middriver 300 - 4000 Hz
6 1/2 midbass 80 - 300 Hz
12 inch subwoofer 15 - 80 Hz

Would you use different crossover points, or different sizes of the drivers ? Of course everything depends on each driver….

I would also use a rather wide baffle , 38 cm wide to get away without baffle step compensation down to the 3 inch drivers crossover at 300 Hz.

Why LR24 specifically ? (Why not 6dB, 12, 18 or 48dB slopes?)

One approach, if one had some extra amplifiers, would be to work out the crossover frequencies and slopes with a DSP.

Then once that was deemed as optimal, then go to passive XOs.
… or …
Just keep it active XOs.