Crossovers with no resistors?

I recently purchased a second hand pair of DIY build floorstanders. Buying DIY kit is always going to be a bit of a risk but I was suitably impressed by the hight spec of the components and the bargain price so I decided to give them a try.
They appear to be based on a Wilmslow Audio 3 way floorstanding tower design (something akin to Spendor S9) and all of the components seem to have been supplied by WA.
The drive units are: Scanspeak D2905 treble, Scanspeak13M8640 mid and Seas Excel W17 EX001 bass.
The crossovers are mounted externally and use high spec polypropylene caps and decent looking air cored inductors. I'm a bit concerned however that there appears to be no resistors on the circuits. Every other speaker which I have owned has had a least one resistor. Is it acceptable/normal not to have any resistors and should I be concerned?
In listening I would rate the treble and mid performance as excellent. Bass is tight and very well controlled but I need to turn up the bass on the tone control on my amp to achieve the volume of bass I would like. To me there is also a bit of a 'deadspot' in the lower midrange/upper bass. Could a lack of resistor(s) on the treble circuit be creating these symptoms?

 

perfectly acceptable not to have resistors in a crossover,a basic 2 way needs olny contain 1 inductor and 1 capacitor.why not draw out the existing crossover and model it to see what its doing,maybe move the bass/mid crossover point a bit

 

As said you don't need resistors in crossovers- even 4th order and even 3 way's don't need resistors.

You do need them to reduce the gain if one driver is more efficient than the other (L-pad) - typically if one is a more efficient horn or ribbon, or you need a Zobel if a drivers impedance rises with frequency.

Have a play/look here.
http://www.erseaudio.com/CrossoverCalculators

BTW L-pads sap a lot of clarity and detail - avoid them if possible - how? Have a nice 2 or 3 way passive crossover but have an amp for each driver pair - that way you can attenuate the signal at line level where you do less / little harm compared to an L-pad. This is particularly important in horn systems where the purity of the horn sound is good to preserve. I have a 5 way system and yes I have 5 amps

 

Many thanks guys, I'm learning a lot here.

It looks to me like the mid and treble drivers have been replaced at some point. Maybe the crossover points need to be 'tweeked' to compensate for these changes?

I'll try to read all the values on the components so that I can run model.

 

if your going to the trouble of an amp per driver you might as well get rid of the passive crossover and go fully active

 

Only if you consider DSP meddling with your signal acceptable and think the expense of a top flight system worthy - £5-6K for a proper DEQX solution for 5 way for example. Behringer offerings will not do it for me and miniDSP is a bit of an unknown quantity and needs lots of bolt ons or rather plug-ins... I am thinking about it but I have got a very acceptable configuration with passives and would prefer to spend the money on some Raal Lazy ribbons and an even better SUT.

 

no need for DSP, just decent active filters made up from valve/transistor or op amp circuits.However if dsp is your thing the only one worth having is a dolby lake, if you can find one

 

What is wrong with the Behringer DCX crossover? The standard unit doesn't have ideal sound quality but it can be improved and still be less expensive than most other options.

There is also the PC crossover route. Simple PC, software and a soundcard.

I do think the op-amp active crossover is best for you if flexibility is not key.

 

Good points. I am not a fan of converting analogue sig to dig and then back again so the other active route could be good.
In the meantime I have other fish to fry and am very happy with my passives at the moment.