Crossover guidance is needed

Hello everyone!

I will try to be as short but to the point as possible 🙂

I have a pair of speakers, from ~1980, they went by the name BENDA around here. i purchased them used. awesome speaker overall, but, there is a problem - original woofers were damaged, so they were swapped for different brand.

Why i started to did around the speaker is because they inherently lacked bass. so i've done some experimentations, i added a second woofer in parallel (i figured, the original woofer must've been 4ohm, so ill trick it by using 2 parallel 8ohm woofers

later i added the passive radiator in the back of the enclosure (after i found out what passive radiators do). so, the speaker is a bit frankenstein I admit, but it still sounds good (at least to me), but then i learned about crossover, and many quirks that come with it when mix different components.

so, now i'm kinda looking for a possible solutions, a chance to learn something on the way, and basically - make the speaker better\right.

the original construction is ~100L box (rectangular, nothing special)
Philips AD0140 tweeter (probably)
Philips AD5060/SQ4 (definitely) x2 (parallel) /////(here i suspect something that defy logic - more on this when we get to crossover)
Philips AD12200 Woofer (presumably) could be AD12650, but i think it does not matter much
Philips AD1200 (passive radiator)

X-Over Philips ADF700/3000 8 8 8 (8 ohm i asume) ////you might see a problem here already////

What is going on now after my interventions:

Philips AD0140 tweeter (probably) no change here
Philips AD5060/SQ4 (definitely) x2 (parallel) no change here

Some 12'' woofer (i think BOSE), 8ohm
Another 12'' woofer (honestly i don't know the brand), but 8ohm
Both connected in parallel.

Philips AD1200 passive radiator (in the back)

Same crossover ADF700/3000

Now, the questions
PART 1

1) obviously, when i connected 2 woofer in parallel, they became 4ohm. the crossover was meant for 8 ohm, and from what a gathered - its a problem.
what are the effects of what ive done?

2) But, what intrigues me even more, is that the original speaker design has 2 tweeters, rated 4ohm each! (SQ4 = 4ohm - i found all the documentation on all the components), in parallel, so 2ohm total for mids? into 8ohm crossover?
Either its wrong, or i just don't know some tricks that speakers builder do...

PART 2 - what should i do now?

1) I bought Chinese crossover just to try it out - honestly sounds pretty much the same overall, but they have no proper spec sheet - so its just a guess with what's going on with it. (i tried to figure that out by using Spectral analyzer - nothing concrete).

2) building my own cross over, but, all that i have is my soldering skills, the ability to learn new information, and my inherent drive to DIY stuff.
basically i'm saying - im willing to try, but don't know enough about it.
i will manage using calculators for crossover,and somehow will find the components, and I have legit specs sheets to most of my components...
but I don't know what order crossover i need - 1st order, 2st order, Xst order..
and I don't know - will it be worth while? money wise as well (i heard that 3 and 4 order Crossovers are pricey.

3) if there where such a thing I would consider buying it - adjustable crossover, with ability to change slopes individually, x-poins individualy, adjust sensitivity (-3bd\0\+3db), and change Ohm rating for each component - then i would be able to play around with it a tailor it as i want it. sadly those devices ive seen - usually for car stereo, and active, means they need electricity, which complicates things.

4) just to buy aftermarket cross-over, but not chineese this time, something more reputable (off cores if such devices exists - i still will use 4ohm tweets, 2ohm mids, 4ohm parallel woofers....i did not find such a device yet)

5) im looking around to find the original woofer, to convert everything to stock configuration. but, the dual mids in parallel do bother me.

Sorry for long post, just tried to explain everything.

Thank you in advance for your replies!

Best regards,
Vadim

P,S,
more about me - i just do DIY, learn on the way, don't have degree in engineering, but learning as i can from where i can.
I'm kinda audiophile, i researched and implemented successfully room acoustic treatment, and spent a lot of time in my car, that actually have DSP with matrix, crossover point, slope select, and many more features. experimented with them a lot, and i do know what all those do and how to work with them,
but how analog crossovers and such work electronically, or how impedance effects crossover components - that's all new to me...so far best i can do is create electronic switches for guitars for example (parallel\series\ phase change etc. basic stuff.)
 
Ah ah :)
Short answer for a long post

Crossovers are filters that are made with the classic L and C and R

Let's consider speaker's Z

:radar:

P.s. Input Z is to be considered at least 1/10 of net Z ( amplifier output resistance WAiT! That's a Re!!+cable )
P.s. For fun, consider also series crossovers
 
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giralfino

Member
2009-02-28 9:20 pm
Vadim,
you, as many beginners do, are making the assumption that a speaker is a simple collection of drivers of constant impedance and Frequency Response (woofer, mid, tweeter) and a crossover whose effect is to cut the SPL of the drivers at a specific frequency or frequencies. If it were so simple everyone would create an awesome speaker.
But it doesn't work that way. Drivers don't have a flat frequency response nor have a flat impedance (ignoring for a moment the effect of the box and the baffle*). So a crossover must be designed to match the characteristics of the drivers you are using. And this is the reason why using an off-the-shelf crossover, Chinese or not, is generally a bad idea because they contain textbook values that are only good for ideal drivers, which unfortunately don't exist. And this is also the reason why swapping drivers, i.e. finding a substitute driver is generally very difficult. For woofers, you also have the additional problem of finding a driver with the appropriate T/S parameters to fit in a particular box.
So IMHO playing with off-the-shelf crossovers will get you sound from the speakers, but the probability of getting good sound is minimal.
If you want to design a speaker, or modify an existing design, you have only a route: measure. I mean measure FR of the drivers in the box/baffle you intend to use, measure real impedance, and measure T/S parameters of woofer/mids, and then use crossover simulators to create a crossover. If you aren't able to measure read the sticky in this forum about designing a crossover without measurement. Unfortunately I don't see how you could go into that route with drivers with unknown characteristics.
I don't want to be harsh, but with your speakers you are simply wasting time and money, without a real possibility to obtain good results.
As for your general question here you are. Connecting two drivers in parallel will halve the impedance, while connecting them in series will double it. I suspect your mids (not tweeters) are connected in series.

Ralf

(*) The baffle/box will alter the natural FR of the drivers imposing a baffle step effect and diffraction.
 
Vadim,
you, as many beginners do, are making the assumption that a speaker is a simple collection of drivers of constant impedance and Frequency Response (woofer, mid, tweeter) and a crossover whose effect is to cut the SPL of the drivers at a specific frequency or frequencies. If it were so simple everyone would create an awesome speaker.
But it doesn't work that way. Drivers don't have a flat frequency response nor have a flat impedance (ignoring for a moment the effect of the box and the baffle*). So a crossover must be designed to match the characteristics of the drivers you are using. And this is the reason why using an off-the-shelf crossover, Chinese or not, is generally a bad idea because they contain textbook values that are only good for ideal drivers, which unfortunately don't exist. And this is also the reason why swapping drivers, i.e. finding a substitute driver is generally very difficult. For woofers, you also have the additional problem of finding a driver with the appropriate T/S parameters to fit in a particular box.
So IMHO playing with off-the-shelf crossovers will get you sound from the speakers, but the probability of getting good sound is minimal.
If you want to design a speaker, or modify an existing design, you have only a route: measure. I mean measure FR of the drivers in the box/baffle you intend to use, measure real impedance, and measure T/S parameters of woofer/mids, and then use crossover simulators to create a crossover. If you aren't able to measure read the sticky in this forum about designing a crossover without measurement. Unfortunately I don't see how you could go into that route with drivers with unknown characteristics.
I don't want to be harsh, but with your speakers you are simply wasting time and money, without a real possibility to obtain good results.
As for your general question here you are. Connecting two drivers in parallel will halve the impedance, while connecting them in series will double it. I suspect your mids (not tweeters) are connected in series.

Ralf

(*) The baffle/box will alter the natural FR of the drivers imposing a baffle step effect and diffraction.

Ralf, thank you for your reply

About wasting time and money, no worries, i understand that its probably the truth, i take it more as an opportunity to learn new stuff, i mean, i can experiment with them all i want.
Driver characteristics and specs i can find out, like i found the specs sheet for original philips drivers.
Measuring - i can do that to an extend


so, can i say, that the main take away would be - if i do want to try and making something out of it is to design a crossover by myself (specifically for my drivers\enclosure)?

regarding parallel\series connection, yes that's the mid drivers
but i checked - it is parallel (+ are connected together, - are connected together, both go to crossover). but, it seems to me Series connection makes much more sense in this case. i wonder why the original design has it in parallel. (or, someone tempered with it before i got them).

also, another possibility that i'm thinking of, is keep looking for original Philips Woofers AD12200 8ohm.
if i find them, then the cross-over should be good (its also philips, and is the recommended one in the spec sheet, along with recommended drivers combination).
(well, and fixing the parallel midrange to series connection...)
 

Galu

Member
2018-04-17 6:50 pm
Hi Vadim, and welcome to the forum!

If you wish to learn about matching speakers to enclosures and matching crossovers to speakers, then I suggest you start with a fresh sheet and employ a simpler driver configuration.

Your current set-up has become unnecessarily complicated by the inclusion of a second woofer to an enclosure designed for only one, not to mention the added complication of a passive radiator and a crossover network not designed for the new combination of drivers.

Why not lay that lot aside for now and kick-start your learning process by designing a nice little two-way loudspeaker?
 
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