What is the sonic result of this crossover design

[corelement]

Hi all

Could someone with some knowledge of crossovers take a look at this crossover design and tell me what thoughts occur to you.

Also what order of crossover is this?

I'm trying to understand which component on the diagram is reducing bass from the woofer for my own knowledge. Not planning on doing any physical modification but rather just understand crossover.

Here is the woofer and tweeter connected to the crossover.

http://www.seas.no/images/stories/vintage/pdfdataheet/e0003_w17ex001.pdf
http://www.seas.no/images/stories/excel/pdfdataheet/e0006_t25cf001_datasheet.pdf

Here are some photos of the actual crossover.

http://i.imgur.com/3XsJC.jpg
http://i.imgur.com/yYCqk.jpg

 

[PeteMcK]

electrically, 3rd order on the tweeter, 1st order on the woofer with zobel and notch

re:'which component on the diagram is reducing bass from the woofer ' - none

 

[corelement]

Aha! wow I never thought about that! It's biwired so two types of crossovers! That's an eyeopener for me.

Hmm, if nothing is reducing bass from the woofer, what could be the cause of the really lean bass I'm getting from the speaker? The bass only kicks in if there's considerable amount of low freq content in a track, otherwise it's really lean.

 

[picowallspeaker]

Hmmm , apart of the characteristics of woofer's construction
and the acoustic load seen by the back of the cone ,
I see that you changed the wires ; the one used for the tweeter is exagerate , that one can handle 20 A !
But the point is in the low section : You have introduced a very low resistance cable , which together with the resistance of the lowpass inductor defines
the electrical damping factor , which results also acoustically .I would upgrade also the coil , going to a thicker diameter of the wire , so there are no 'bottlenecks' . 1 mm is minimum , 1.2 mm is better , 1.4 would be perfect

 

[Moondog55]

Hmmm Ported design? Which way does the port face and how far from the wall is it??

 

[corelement]

Hmmm , apart of the characteristics of woofer's construction
and the acoustic load seen by the back of the cone ,
I see that you changed the wires ; the one used for the tweeter is exagerate , that one can handle 20 A !

Lol everything's as it came out of box What do you mean by the wire for the tweeter is exaggerated? They both look the same type of cable to me, only the number of wires going to the woofer are double than that of the tweeter. So wouldn't that make the wire going to the woofer.. exaggerated?

Also how'd you find out the wire can handle 20a?

But the point is in the low section : You have introduced a very low resistance cable, which together with the resistance of the lowpass inductor defines the electrical damping factor , which results also acoustically .I would upgrade also the coil , going to a thicker diameter of the wire , so there are no 'bottlenecks' . 1 mm is minimum , 1.2 mm is better , 1.4 would be perfect

Ok, correct me if I've misunderstood, The coil is the inductor ? And basically because the inductor uses very thin wire it's causing a bottle neck and making the bass lean?

 

[corelement]

Yes, it is ported on the rear. One speaker is 2 feet away from wall, the other speaker is 2 feet away on rear and 1 foot on left side.

This model by jamo is known to be very lean on bass, I'm basically trying to understand why.

Here's a couple of pics

http://i.imgur.com/jF6Vo.jpg
http://i.imgur.com/469zd.jpg

 

[picowallspeaker]

Lol everything's as it came out of box The one for the woofer is double the thickness of the tweeter. But they appear to be the same cord, only the one going to the woofer is much thicker.

Oh , it seemed to me that the one for the woofer was a 'planar' type.
So , if they came as they were projected , with the original wires , forget about my assumption .

Hmm there are two coils though, could you explain to me what purpose the 1st and the 2nd coils serve?

The one in series , the bigger one , stops the high frequencies , together with the capacitor after it . The second one , together with capacitor , form an RC net which linearizes the impedance , so the job for the first coil ( and cap) is much easier .

I suggest to read the 'sticky' thread made by Allen B at the top of multi-way section on the Forum . There are all the answers to your questions .

 

[Moondog55]

Look at the data sheet, the woofer is more of a midrange and has very little output below 100Hz, short answer if you like the top end is to get a decent subwoofer or three, 3 is better

 

[corelement]

Oh , it seemed to me that the one for the woofer was a 'planar' type.
So , if they came as they were projected , with the original wires , forget about my assumption .




The one in series , the bigger one , stops the high frequencies , together with the capacitor after it . The second one , together with capacitor , form an RC net which linearizes the impedance , so the job for the first coil ( and cap) is much easier .

I suggest to read the 'sticky' thread made by Allen B at the top of multi-way section on the Forum . There are all the answers to your questions .

Hehe yeah I tried reading that but there were no images so it was difficult to understand which is which, even tried googling but it's quite confusing right now. Gonna need a little more spoon feeding hehe.

Ok, correct me if I've misunderstood, The coil is the inductor ? And basically because the inductor uses very thin wire it's causing a bottle neck and making the bass lean? And you're talking about the L2 coil or the L1 coil?

 

[corelement]

Look at the data sheet, the woofer is more of a midrange and has very little output below 100Hz, short answer if you like the top end is to get a decent subwoofer or three, 3 is better

Yes this is true it is more of a mid bass unit. However everything that's coming out of the woofer just seems very lean. I've read information bits across the internet how people have modified the crossover and fixed the lean lower mid frequencies.

I tried contacting some of the people who did it but haven't got a responce back about what modification they did.

 

[Dirk95100]

What matters is the acoustical output of both drivers combined, not the electrical slope of the crossovers. Of cause the crossover is very important in getting the wanted acoustical output.

 

[picowallspeaker]

Look at the data sheet, the woofer is more of a midrange and has very little output below 100Hz, short answer if you like the top end is to get a decent subwoofer or three, 3 is better

Usually , when the bookshelf design is well done , if the speaker reaches 60 Hz
linearly ( working on the crossover circuit , diminishing sensitivity but augmenting extension ....) there won't be any lean bass .
Then , usually in BR design the port itself is used as source for frequencies under
drifer's Fs ; same as passive radiators used instead of a duct .

 

[Moondog55]

I'm not talking about deep bass, the roll-off of the woofer starts very early and rolls off gradually from 1k and is 25dB down at 100, add that to the baffle step loss and you have what you describe as lean bass, you need to add 25dB of bass starting at around 300-500Hz which will probably need a 12inch woofer you can do this passively with a large inductor as first order is probably better in this instance ( You would be making a 2.5Way speaker)

 

[picowallspeaker]

a 12 " would ruin the coherence given by a nearly point source cabinet , not to speak
about the benefits of a free standing speaker
The benefits of a 3 way speaker are that it may sound more 'articulated'
specially in the bass ! But it's not a good thing to choose a driver only by the measured parameters and curves , not to speak about the need of bigger cones to overcome
sensitivity and efficiency issues . Bigger cones lead to bigger problems : the first that comes to mind is that they exagerate the microphonic effect of the speaker itself , so the project must be really well done , otherwise the amplifier would catch the BEMF
( electric counter force )and modulate with the original signal .

 

[corelement]

Thank you for writing all that up guys, I'm in a learning mode right now so please don't mind if I ask silly questions hehe

I'm not talking about deep bass, the roll-off of the woofer starts very early and rolls off gradually from 1k and is 25dB down at 100, add that to the baffle step loss and you have what you describe as lean bass, you need to add 25dB of bass starting at around 300-500Hz which will probably need a 12inch woofer you can do this passively with a large inductor as first order is probably better in this instance ( You would be making a 2.5Way speaker)

AHA! now this I can understand, because right now what I'm doing is I've got my equalizer peaking 110hz with 16+ DB with a gradual slope on both sides to compensate for the lean bass. It's working but it bothers me because it's a makeshift.

However the way you describe it, it seems I'm doing the correct thing with the equalizer. A pseudo-passive fix of sorts?

a 12 " would ruin the coherence given by a nearly point source cabinet.

This is quite true, the other option is getting another pair of bookshelves of a similar category such as the be-718.
For the moment I guess the equalizer will have to do unless I do the 2.5way thing moondog is talking about.


Moondog, could you describe that technique a little bit more for me, like for example, the 1st order inductor is already larger than the other one, are you suggesting to make it even larger?

 

[picowallspeaker]

Note : as Dirk95100 Zipcode ?!? said , the acoustic slope will be given by the combination
of the electrical one to the mechanic one represented by the speaker and the cabinet .
Pneumatic suspension gives roughly a Butterworth slope of 1st order ; Bass reflex might
give 2nd order with a second impedance peak located at port's resonance .
As Pete McK said , the woofer section is 2nd order ...oh well , he said 1st order + zobel+ notch .... I would say 2nd order with the capacitor attenuated + notch .
Of course the lowpass coil in the woofer section is the one which carries most of the
energy , so a correct dimensioning of it is necessary . But this has already been taken into account by the designer , because the added resistance ( Ra ) represented by the (in series ) coil and the wire , they influence other parameters , and eventually lowering of the Ra would bring to a bigger box

 

[Kjeldsen]

Logically a better coil/inductor with lower resistance (close to 0 ohm), is a better choice and many tweekers do this blindly. However it will reduce bass extension since Qes is lowered, and it will be even more lean. A coil with resistance larger than 0 ohm is therefor a part of the design, and should not be replaced by a "better" one without measuring the effect.

link to some illustrated tech notes
Strassacker: Speaker - kits - do it yourself

 

[corelement]

Logically a better coil/inductor with lower resistance (close to 0 ohm), is a better choice and many tweekers do this blindly. However it will reduce bass extension since Qes is lowered, and it will be even more lean. A coil with resistance larger than 0 ohm is therefor a part of the design, and should not be replaced by a "better" one without measuring the effect.

link to some illustrated tech notes
Strassacker: Speaker - kits - do it yourself

This makes a lot of sense. A high resistance inductor will definitely help with bass extension and it seems deliberately done in order to help the woofer perform better.

From what I'm realizing, it's the woofer itself that is lean and jamo has attempted to use high resistance inductors to improve bass. Now the question is, what kind of upgrade to the cap and resist on the woofer side of the crossover help with further improving bass and lower mids.

 

[Moondog55]

It is a second inductor of much greater value and is placed in series with the "Boost" woofer. The value of the coil is chosen to give a first order roll off at a particular place in the frequency response.
Actual value needs to be carefully considered and I would defer to other more experienced designers on its value, but it will be large and laminate or ferrite cores are probably the best in this situation.
For an 8R woofer the values may range from ~ 4mH to 6 or 7mH, so quite an expensive exercise. Personally I see no problem with using a large woofer ( 8 / 10 or 12 inches ) with a low Fs in this application