The secret of building a good 2-way

[Starre]

Ty Salas, I will build that box to start with and then try some solutions for the filter. I have noticed that the woofer has an increasing impedance from 1kHz and upwards, but in your measuring this is gone so I wonder how it is done.
My initial thought was to use a low crossover frequency, something like 2kHz to be sure not to push the woofer too much, and since the tweeter got a Fs of 700Hz (I saw somebody measuring this finding it was a little higher around 800Hz) I think it can handle 2kHz just fine, but I probably need to try it before I can say if it works. I am excited with this since it is my first speaker project. Any input is welcome!

[dirkwright]

Originally Posted by thoriated

The Iron Lawbreaker satisfied the goals at hand for a 2 way - I extend the basic approach to 2 1/2 way configurations for larger speakers.



For this speaker, in a volume of approx. 3.5 cu ft, I wanted the maximum broadband efficiency, good quality bass with good extension, a flat response and low distortion at high levels, and I think I achieved it, with a response down to 50-60hz flat @ ~99db/w/m. The HF driver is an Altec 288G and the bass driver is a JBL 2220A. As a side benefit, I was able to achieve a very flat impedance of between 16 - 20 ohms between 40 and 240 hz due to adding ~ 1 cu ft of activated charcoal to the enclosure (in gas tight bags) to increase acoustic compliance and using a special xover/frequency shaping circuit in the bass featuring a custom air core transformer that allows minimum component count bass response shaping with the loss of almost no efficiency or damping and also serves as a series inductance to the woofer - the only series woofer xover component (although I also use 600uf of bass polypropylene AC coupling to reduce cone movement from out of band LF). With an overdamped tuning of the box to ~32 hz, the overall bass quality is surprisingly tight and very detailed - more like that of a closed box than a conventional ported system, only in some ways better yet since the impedance is so constant throughout the bass passband (no Zobel networks used). There is some serendipity with this all coming together as well as it did, IMO. With this design, using Elliptical xover filters allowed me to reasonaby approximate a first order xover response with the minimum possible driver overlap & allowed an xover ~550hz which minimizes Doppler distortion.

I like these a lot! Since I can't hear much over 8kHz, I would go with the B&C DCM50, a nice JBL 500Hz horn, and a 15" B&C woofer, active crossover @ 500Hz of course.
B&C SPEAKERS

[Salas]

Originally Posted by Starre

Ty Salas, I will build that box to start with and then try some solutions for the filter. I have noticed that the woofer has an increasing impedance from 1kHz and upwards, but in your measuring this is gone so I wonder how it is done.
My initial thought was to use a low crossover frequency, something like 2kHz to be sure not to push the woofer too much, and since the tweeter got a Fs of 700Hz (I saw somebody measuring this finding it was a little higher around 800Hz) I think it can handle 2kHz just fine, but I probably need to try it before I can say if it works. I am excited with this since it is my first speaker project. Any input is welcome!

There is an RLC conjugate that helps the impedance. Just make the crossover as recommended since it has been tried lower also etc. to have a reference. Its mature as it is. Then you may try whatever. Good luck.

[Starre]

Ok Salas I will build it like you said, thanks. I will post some pictures later on.

[Salas]

Don't forget to recess the tweeter in the baffle at least. But try the woofer too to keep the emitting points alignment as in the original. It may be 2-2.2kHz cross or something already, as you have seen my notes weren't precise anyway. Has good mid projection no worries, I listened to it recently again.

[Helmuth]

Originally Posted by dirkwright

I like these a lot! Since I can't hear much over 8kHz, I would go with the B&C DCM50, a nice JBL 500Hz horn, and a 15" B&C woofer, active crossover @ 500Hz of course.
B&C SPEAKERS

I think 99dB 1Wmtr down to 50Hz is overrated in that compact design. I think 96dB 1Wmtr is more realistic.

Monitor-xl does 92dB 1Wmtr and has response down to 30Hz that is high efficiency to to have cut off that low at 92dB 1wmtr.

[Starre]

Yes Salas, I will do that to both drivers, getting the tool for it. You said it was made from 19mm, I was thinking of maybe doing it with 22mm cabinet keeping the same internal measures for stability. I know this will make the cabinet a little wider (6mm), do you think it is a good idea or will it change the sound?
I will use all film capacitors and good quality coils. That big one of 2.5mH, what do you suggest for it? I want something good but not costing a fortune (less than 40 Euro).

[Salas]

A 2mm wire air coil was used for the 2.5mH. See the DCR of such in vendors lists and match it for other types maybe cored high power you may opt for, cost wise. Yes you can use thicker material 22mm and keep the internal proportions the same. The difference in external size will be negligible for altering diffraction due to dimensions drastically.

[dirkwright]

Originally Posted by Helmuth

I think 99dB 1Wmtr down to 50Hz is overrated in that compact design. I think 96dB 1Wmtr is more realistic.

Monitor-xl does 92dB 1Wmtr and has response down to 30Hz that is high efficiency to to have cut off that low at 92dB 1wmtr.

Yeah, maybe so. The B&C 15PS100 is pretty good. The -3dB point is about 45Hz, sensitivity is about 94dB, in a 2.5 cu ft vented box tuned to 42Hz. Group delay peaks about 12ms just below the -3dB point. With 300watts in, I see about 115dB at the -3dB point. The tweeter would have to be padded down heavily of course.

[Helmuth]

Originally Posted by dirkwright

Yeah, maybe so. The B&C 15PS100 is pretty good. The -3dB point is about 45Hz, sensitivity is about 94dB, in a 2.5 cu ft vented box tuned to 42Hz. Group delay peaks about 12ms just below the -3dB point. With 300watts in, I see about 115dB at the -3dB point. The tweeter would have to be padded down heavily of course.

When do you start.

I like B&C but, I have a better tip then the B&C the beyma sm115N 97-98dB. Can not find a better one for the money.
For your application also the beyma 12BR100 94dB is a sharp priced studio driver. Also good for high efficient hifi use. To keep it affordable look at the 18sound horn + driver xd125 XD125 - HF Compression Driver
Also would match nice with the 1,4" fatial pro driver and horn down to 500Hz. Has also a nice price tag.

FaitalPRO - Professional Loudspeakers Made in Italy
FaitalPRO - Professional Loudspeakers Made in Italy
12br100
http://profesional.beyma.com/pdf/12B100-RE.pdf
sm115
http://profesional.beyma.com/pdf/SM-115%20NE.pdf

attached simulation 12br100 94dB 1wmtr tuned to 40Hz 90liter.3,2cu/ft -3dB 35Hz. group delay 17msec on tuning frequency. Higher delay does mean more resonant.

The 12br100 and the 180 sound horn plus driver will cost you some where between 250 and 350dollar for a set. So you can build a hornloaded studio monitor -3dB 35Hz-18kHz 94dB 1Wmtr under 1000dollar.
first picture driver response second basreflex port response last groupdelay.