4 way design

[SoundLogic]

Hi,
Heres the plan

LCY 130 Ribbon for the Highs powered by NAD C355BEE
Seas MCA15RCY Midrange powered by Crown XLS202 (200 watts)
Beyma 10br60 Midbass powered by Crown XLS402 (300 watts)
Hertz DS300 Subwoofer in clamshell isobaric configuration Powered by Crown XLS602 (380 watts)

Crossover
DBX234XL

Here are the problems
1.What might be a good box design for the midrange?

2.I am really afraid of over powering the little 5 incher ,is it ok to feed it off a 200 watt amp considering I am crossing it over from the Beyma at around 500Hz.I am unable to find any decent amplifiers that have a lower power rating that is available in my country apart from QSC and Crown both end up at 200 watts at 8 ohms.The specs rate it at 100 watts nom with a max short term of 300,but looking at the driver I am kind of sceptical .

3.The Beyma is rated at 100 watts with 200 watts max ,again same issue with the amp power.I am thinking of putting it in a sealed box,what do you guys think?

4.The Hertz Subs have already been bought as with all the other components save for the amps,I know they arent the best drivers when it comes to Xmax or Fs but cant be helped,hence the best configuration I could come up with is the Isobaric clamshell ,which should,theoretically help in improving distortion figures and control excursion to an extent.I am thinking of loading it in a ported enclosure.

5.Basic problem is figuring out the power requirements assuming I would like to play within reasonably safe limits.How much power should I feed the mid and midbass I read somewhere that they should be equal power which means that there is also a possibility of using a 4 channel amp instead which should also bring my cost down a bit (QSC DCA1824)

Any help on the above will be much appreciated

Regards,

[ChrisA]

5.Basic problem is figuring out the power requirements assuming I would like to play within reasonably safe limits.How much power should I feed the mid and midbass I read somewhere that they should be equal power which means that there is also a possibility of using a 4 channel amp instead which should also bring my cost down a bit (QSC DCA1824) [/QUOTE]

The amount of power depends on the relative sensitivity of the drivers. Ideally all of your drivers would have the same sensitivity (measured at 1W and 1 meter) and require the same power. The simplest thing to do is pad down the more sensitive drivers so you can use equal amounts of power.

[DougL]

From your post I am making some guesses, because the information is not clearly stated.

I assume by context that you are going to use an electronic crossover and 8 channels of amplification.

I assume this is for a home setting.

In this context, in a reasonable sized room, you will be stone deaf long before
you heat up your drivers. If it is for an outdoor concert venue, or a dance venue, you probably need more robust drivers.

I have a tri-amped OB with that mid and 6 channels of 30W class D amps and I can make my ears ring long before I run out of power.

For the midrange, I would use a sealed enclosure. I would size it between 1 and 4 times VAS.

The QSC DCA1824 4 channel amp has more than enough power @ 170 W into 8 ohms and the ability to drive 2 ohm loads.

Good Luck.

HTH

Doug

[SoundLogic]

All the drivers are within about 89 db +/- 2 Db in terms of sensitivity,they can be further matched by using the gains on the crossover,I will be using an electronic crossover (dbx 234xl) and 8 channels of amplification for my main system in the house.Someone told me that you should provide for atleast the nominal rating of the driver (X) ideally your amplifier power should be 1.6X to allow for some headroom.Hence I am slightly confused,apart from the fact that I dont know if the mid will die of thermal failure if I feed it off the 200 watter .I dont want to end up frying to poor little seas because of too many watts.Please advise.

@DougL-Did you make those amps yourself? I was thinking sealed is the way to go for the mid,thanks for the suggestion.


Any info on isobaric subs?
Pros cons?

[DougL]

Originally Posted by SoundLogic

... .Someone told me that you should provide for atleast the nominal rating of the driver (X) ideally your amplifier power should be 1.6X to allow for some headroom.Hence I am slightly confused,apart from the fact that I dont know if the mid will die of thermal failure if I feed it off the 200 watter .I dont want to end up frying to poor little seas because of too many watts.Please advise.

@DougL-Did you make those amps yourself? I was thinking sealed is the way to go for the mid,thanks for the suggestion.
...

There are rules of thumb about power. They apply to speakers with passive crossovers. Even then, there is only limited truth to the statements.
The real truth is that gross clipping or ignoring gross speaker distortion can destroy speakers. Your midrange is capable of about 108 db continuously.

If you played a 110 db sine wave at 1K for an extended period, your voice coil might melt. Clipping a 200W amp can send 400W into a driver and potentially damage it, probably after several seconds of that abuse. However, that happens at over 112 db at 1 meter.

Bottom Line, you are covered.

I did not build my amps. They are a pair of Teac A700 3 channel amps.


HTH

Doug

[SoundLogic]

I have finally managed to get around to building the subwoofer cabs for yes my Hertz "Car" subs , here are a couple of pics of the bracing and the cabinets , they are made out of club premium bwr aa ply , still unfinished as another layer of mdf is to be applied over the ply for a box in box concept , in between these two boxes will exist a layer of bitumen waterproofing felt (visco elastic 1 mm) .This should in theory work well as a Constrained layer damping system , which according to my research ( over the internetz) works best with a thin layer in between two plates of similar densities that are not coupled to each other by anything other than the layer and the glue. Initial tests (knuckle rap,ouch!) of just the ply cab with the bracing provides a very high pitched crack with no ringing , the cabinet seems quite dead already , things should only improve with the CLD (I hope) .

The bracing that you see is essentially non symmetrical , all the panels of the sub are of different sizes owing to the overlap butt joint system I have used , hence each panel has a different resonance characteristic , the bracing is offset using the golden ratio .The cabinet bracing is mirror imaged in its offset for the pair . In addition to the bracing you might notice a blue panel , containing a special sound absorbing / back wave scattering mat jointly developed by me and 3m/dupont and is proprietary hehehehe .
There will ultimately be two woofers in each cabinet in a face to face push pull isobaric configuration , this is done for three main reasons
1) Space used is half that of one woofer
2)In a push pull (where one woofer moves out and one in) distortion is lowered .
3)Its just a cool concept , hehe .

Things I am giving up include 3 db spl because they are wired in series , but hey I have two cabs , stereo subs so I guess I make it up there . Using these car subs have a few problems , they don't handle all that much power before reaching excursion limits , but I am listening to music only so very little sub 30 hz content anyway .

Hoping to get them absolutely done in a few days , more pics to come


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