Internal Crossovers

[Sirch Sound]

Hi again

 

I am still looking at building my speakers. I am looking at the 18" super scooper's from speakerplans.com. I am going to load them with the Eminence sigma 18" Driver, good idea? However the crossovers are confusing me. I am looking at the range of the eminence crossover panels, with the speakon connectors already attached, so you basically plug the driver into them and screw them onto your cab, that simple. However I am not sure exactly which one I want to buy, I would have thought the low frequency option, which gives me a 250hz signal, however this does not give me a high freq signal out so that I can run my tops off them right? So should I be looking at the other crossovers, which give me a 200khz and a 9db hight output, but they must be for the mid/high cabs right? Sorry if I'm being confusing but I'm very confused myself!

 

If all of this is wrong could you suggest the right frequency and power rating I need for these cabs. The sigma Drivers are 650wrms and the Eminence crossovers are 600wrms. Is it as simple as spec the crossover rating to the same as the driver or do you have to spec it slightly less so that the crossover will protect the drivers from overload?

 

Thanks for your help

Rich

[paulears]

If you are going to build your own speakers, then until they are complete, it will be difficult to predict exactly what cut-off frequencies will sound best when used with your choice of programme material. Maybe moving to a bi-amped system with an adjustable crossover would be a better method of running them. Using a preset crossover, is more difficult, as the balance between HF and LF might be wrong - after all, the efficiency of the cabinet makes a big difference.

[SteveAATW]

I'd stay away from using passives, especially down at bass frequencies. To get a decent power rating they've got to have quite big inductors, which makes them expensive and if a fault develops they will heat up very quickly and that leads to delamination of the inductor, caps blowing and all sorts of nasty stuff. Plus if you have a passively crossed system with one amp potentially driving 3 drivers if one of them blows, then the other two have then potentially got to handle the full power of the amp or your crossover has got to try and dissipate some of the spare power. Then the crossover has to be pretty well designed if you don't want to introduce phase and time alignment problems into the signal, without being too much of an audio snob I'm not sure how much thought to this emminence would put into their designs. All told passives are a bad idea for a number of reasons.

 

If your worried about the cost of bi or tri amping don't be. You don't have to go into XTA money to get a decent crossover, there's perfectly good analogue one's kicking about for around £100 or if you want a digital one the Behringer Ultradrive is fantastic value for money at around £200 - I've got one sitting next to a DP-226 and a DP-448 and the difference in performance between them is barely noticeable. If your worried about the cost of extra amps, again there's pretty good value models out there. The Peavey CS series, Yamaha P series and especially the Bittner basic series offer great value for money.

[Sirch Sound]

I think this is defiantly going to be the way to go as I will need to buy a second amp in the near future to power them as my poor makie only kicks out 700w per channel at 8ohms, the subs alone will be double that, however will I be able to get an amp that can kick out say 700 - 800wrms per channel for a cheep price, as this must be getting to the larger end of the spectrum. What will be the advantage of a digital crossover instead of an analogue crossover??

 

Cheers

Rich

[SteveAATW]

You get much greater control with digital - you can use different filter types - Butterworth, Linkz-Reily etc which is useful for matching the crossover to the type of sound you want to create. and you can also assign different slopes to the crossover regions - normally 6dB, 12dB and 24dB per octave. Most digital crossovers have limiter facilities on them and also you get a better idea of whats going on gain wise and can have much more precise control over the gain of each output. You also get EQ and invidually adjustable delays for each output which is handy for time aligning. Plus PC linkup (though with the Behringer the PC software is a bit pants and the front panel control is that good you don't need to)

 

Yamaha P7000S is just under £500 exc vat and can do 750W per channel into 8R, for the money they sound great too:

 

http://www.tmc.ltd.uk/acatalog/Yamaha.html

 

Also remember that its better for the amps to work on seperate drivers as they don't need to work as hard and thus will sound better - the more you push any of the components in a sound system the worse the sound will get, everything likes to operate with some spare capacity.

 

If you have got some time before you need everything and want some top end amps keep your eye on ebay for QSC Powerlight, MC2 Amps and Crest CA series. They quite often go for barginous prices! MC2 will also honour the 5yr warranty even if the owner changes.

[gyro_gearloose]

May I ask, why have you chosen to build the 18" super scooper? It seems to be one of the more complex designs on the website, and by Rogs own admission they aren't the best type of enclosure. From the FAQ section of speakerplans.com :

 

I don’t like scoop or rear loaded horns cabinets because the output from the front of the driver is out of phase from the output of the horn or rear of the driver. This causes a dip in the frequency response, which normally occurs around the 70 to 90Hz range for 15 or 18" bins. It is in this 70 to 90 Hz range that we hear or feel the kick or speed of the bass. Most scoop bins have a 3 to 6 dB dip in the response around that area making the cabinet sound slow and heavy. Scoops lack any real punch and detail and are very difficult to mix a band on. Bigger scoops with 21" drivers will have the dip lower down at around 50 to 60 Hz and the dip in response will be less pronounced with the more cabinets you use.

 

I much prefer folded horns as they do not have this dip and phase abnormality around the crucial 70 to 90 Hz frequency range. Folded horns are capable of reproducing the music very accurately and exposing a lot of detail, detail you would just not hear with a scoop bin. Folded horns also throw the sound a lot further than scoops. If you walk away from a scoop bin the sound seems to disappear after about 35 feet, with folded horns the sound travels a lot further.

 

The X1 seems to be a better design. Although its designed for a different driver, it is smaller and easier to build than the super scooper.

[Sirch Sound]

If im using an external crossover does that mean that all I need on the back of the cab is a simple speakon connection plate? How would I go about wiring this? Just take the driver connections and wire them to 1+ and 1- on the speakon? And once I have done that how would I wire a through onto the connector, again just take another pair of cables from 1+ and 1- and like them onto the 1+ and 1 - on the second speakon socket? Or would this not be possible as there is not an internal crossover to limit the power to the first driver in the chain? In which case the first driver will take all of the power and the other cabs in the chain wont get anything.

 

I'm not sure whether I have just answered all of my own questions or not there!

cheers for the help

Rich

 

Oh and as for the super scooper's I'm not too sure why I chose them, they were recommended in the other post about building my own speakers and I liked the look of them when I looked at them, not a good basis I know and may reconsider with the additional information you provided.

 

Thanks again

Rich

[SteveAATW]

Convention on 4 pole Speakon is that bass is wired on 1+ & 1- and mid/high is wired on 2+ & 2-.

 

If you use a digital crossover the driver is just connected straight to the speakon socket in the cabinet and yes, if you need a through connector to drive another sub then just put too speakon's next to each other on the rear panel of the sub and solder connection leads across the back off them.

 

Any drivers you connect will be wired in parallel with the first, so the power is split between the two - just watch out over time for drivers blowing as if you have two cabinets wired in parallel to one amp one will eventually take the full power if the other blows.

 

Because of this on twin driver bass bins you will sometimes find that each driver is wired to a seperate channel on the speakon. On the Funktion One F218 for instance driver 1 is wired to 1+ & 1- and driver 2 is wired to 2+ and 2-.

 

One thing to watch out for with the solder tab speakons if your using multiple cables is that its often easier to crimp the wires to a spade connector, put the spade connector onto the speakon, then solder the wires to the spade crimp and then the spade crimp to the speakon terminal, than try and hold two wires against the tab whilst you try and solder them on.

 

 

 

One more thing - out of intrest how much are the drivers and wood going to cost you in total?

[Sirch Sound]

Wood - not too sure as I need special birch ply with 13 laminates instead of the usual 8 or 9 and as for drivers I'm hoping to spend about £200 on them, plus about and extra £100 on Castor's, handles speaker pains and grille ect.

 

Rich

[SteveAATW]

Unless you want to have the experience and satisfaction of building the cabinets yourself, which is fair enough, I would really recommend you have a look at the T218 boxes that Thomann sell - they won't be that much more than what your going to be spending anyway and without CNC cutting equipment building something that sounds as good as something thats properly manufactured is always going to be a struggle.

 

Unless you want to have the experience and satisfaction of building the cabinets yourself, which is fair enough, I would really recommend you have a look at the T218 boxes that Thomann sell - they won't be that much more than what your going to be spending anyway and without CNC cutting equipment building something that sounds as good as something thats properly manufactured is always going to be a struggle.

[Sirch Sound]

Right last question, I have a gig coming up very soon and there is no way which I am going to be able to get the amp in time, however I could probably stretch to the crossover, so would it be possible to run the system (2 subs and 2 tops) off one amp, just as I one off. I wont need any great volume, its only small but unfortunately not small enough to get away without bins.

Cheers

Rich

[J Pearce]

If the amp can take two tops on one side and two subs on the other then yes; but the system would be in mono.

 

The signal chain would look like this:

 

Mixer - Crossover - Left side of amp - Tops (paralleled)

_______________- Right side of amp - Subs (paralleled) (__ used as forum deletes multiple spaces)

 

What impedance are your tops and subs?

[Jivemaster]

If you are using an active crossover then the only need for passives is to longstop, - Something to save the tweeter if is is driven full range and perhaps something to stop the sub driver using power above 200hz if fed full range. The real crossover frequencies to be set with the active crossover at test flight time.

[Sirch Sound]

The Independence of the tops is 8ohms and the subs are 8 ohms aswell.

 

Rich

[J Pearce]

In that case you would be fine to run the system as described above; that is one side of the amp running both tops, the other side running both subs.