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Discussion Starter · #1 ·
Well i'm half way done with one speaker cabinet and here is what turned out. The side edges I will be routing with a 19mm roundover soon as I get the bit and the front and back with a smaller 3mm roundover. Finish will be gloss black, not worried about producing a mirror like finish, just an even gloss finish is all i'm after. The auto body filler using a harderner turned out much better than using wood putty. The box size is 1100x450x450mm using 25mm all around with 25mm+18mm for the baffle board, the actual box volume is about 145L.


The speaker system will be a two way active crossover using the behringer DCX2496, AE TD15m woofers, QSC waveguides as you can see, and a Beyma CP-380M CD. Will be building for now just two and later a center speaker. I chose active as it is far superior to passive systems from reports. CD's will be powered by a rotel RB-1080 and the woofer by a rotel RB-1090. The porting is tuned to 58Hz and I will be stuffing the box with polyester insulation to reduce woofer excursion at a certain point as well to eliminate any resonances. With this configuration I can use the full 400W and beyond from the rotel rb-1090 into the woofer which will give me about 124db.


Will keep updating this thread as I go along. Should have the woofers and CD's in a couple of months time.




 

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Quote:
Originally Posted by DL86 /forum/post/17249040


I chose active as it is far superior to passive systems from reports.

It's all in the implementation and going active isn't going to solve any problems for you. I'll say it again - off the shelf active crossovers only give the impression you are doing things right when the reality (measured) will be far different. Do you have measurement ability? Do you have the ability to model the crossover? If not that will have a far bigger impact on the end result then whether you go active or passive. For example here is one of the latest iterations of the active version of my No Quarter, modeled with actual measurements in the crossover designer of SE:




Now imagine I had no measurement ability or knowledge of crossover design. All I know is I want a 1300hz crossover, and I need a shelf filter for BSC, and another shelf for CD compensation, and taking a guess at sensitvity matching I'd be lucky to get this:




Personally I'd take a cheap Eminence 2512 and Celestion 1425 with a properly designed passive crossover over the above example any day-even it was using all TAD drivers. Even the performance of those drivers is not going to over come the gross response and phase issues.


I know my view on this isn't popular in this forum, and some people can make it work "good enough (for themselves)" but I just don't buy into the idea that a DCX will turn a novice's creation into something rivaling Tom Danley. If you don't know what you are doing the results will be the same, whether you go active or passive.


OTOH since you obviously don't mind spending some cash do yourself a favor and buy a mic and something like Soundeasy and we'll help you design what you want properly.
 

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Discussion Starter · #4 ·
I will be doing a lot of measurments. You can't design a crossover without proper measurements I know that already. I am gonna be using a behringer EM8000 mic. I much rather hit a few a buttons than having to resolder caps and inductors.


Can't I just use room EQ wizard and take measurments from there and adjust accordingly?
 

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Quote:
I'll say it again - off the shelf active crossovers only give the impression you are doing things right when the reality (measured) will be far different.

But the great thing about active is that we still can have performance in our room in a short period of time. I agree measurements still have to be done but Active gives 90% of the performance to start with...the last 10% of perfection needs expertise like yours, Augerpro.

Quote:
I know my view on this isn't popular in this forum, and some people can make it work "good enough (for themselves)" but I just don't buy into the idea that a DCX will turn a novice's creation into something rivaling Tom Danley. If you don't know what you are doing the results will be the same, whether you go active or passive

I have say that is a direct point against me
No worries, your view is popular (I never knew you thought it was unpopular here) but we all have our own requirements. My goal isn't really to rival Tom Danley or Mark Seaton but I have heard their products and many other speakers over the years and my DIY active designs (which had advice from Mark) are pretty damn good for HT. Better then anything under 2K for main speakers (of course my drivers cost almost 2K so....). Anyways, we are in that subjectivity area now and its all personal choice. I care about measurements and Im learning daily about doing it all better but I like speaker performance and movies even more then I like any measurement.
 

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Quote:
Originally Posted by DL86 /forum/post/17249333


Can't I just use room EQ wizard and take measurments from there and adjust accordingly?

Is this EQ wizard a feature of the stereo receiver/controller? If so I suppose with good measurements and lot of tweaking it could get you in the ballpark, but without any specifics I have no idea how you would go about using it. As I said the implementation is everything. it might work well or not at all. I'd need more info.

Quote:
Originally Posted by penngray /forum/post/17249743


I have say that is a direct point against me

You were just the most vocal
But my comments aren't anything towards you personally. You've been seeing the light and after we get a properly designed crossover for those drivers you have I think you'll agree! If you can wait a few months I'll probably be able to help with that (active or passive).

Quote:
Originally Posted by penngray /forum/post/17249743


I agree measurements still have to be done but Active gives 90% of the performance to start with...

That plot I showed earlier that would be quite typical of novice user's results is not anywhere close to 90% in my opinion. It doesn't even register on my performance or value scale. Like I said a properly designed passive using drivers 1/3 the cost would probably be better. But it's all a matter of taste whether I agree or not. There are whole groups on some forums that throw drivers in the same cabinet and use any old cap and coil they find laying on the sidewalk and blabber about how good it sounds. Who am I to argue with what someone else hears?
 

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Looking good.


"The porting is tuned to 58Hz and I will be stuffing the box with polyester insulation to reduce woofer excursion at a certain point..."


Stuffing the box will increase excursion for two reasons, one good, one bad.


The good one - increase in effective box volume


The bad one - lowers Q (I'm not clear on what combination of Qa, Ql, or Qp), reducing output at Fb
 

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Quote:
Originally Posted by augerpro /forum/post/17250952



That plot I showed earlier that would be quite typical of novice user's results is not anywhere close to 90% in my opinion. It doesn't even register on my performance or value scale. Like I said a properly designed passive using drivers 1/3 the cost would probably be better. But it's all a matter of taste whether I agree or not. There are whole groups on some forums that throw drivers in the same cabinet and use any old cap and coil they find laying on the sidewalk and blabber about how good it sounds. Who am I to argue with what someone else hears?

No arguements from me but I have always had measurements tools so I get to that subjective 90% mark with crude measurements in room so I would get a plot that is somewhere in between. If I figure out the delay settings Im even closer.


I still havent figured out why you have great concern over using the DCX in your project but I havent spend enough time figuring out all the issues in the first place. I will have my own with my speakers with similar parts so I will learn as I go from them. Right now its all about painting
 

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I have no concern with using the DCX in my own project, I am using it afterall??


If you are asking why I'm not concerned about using personally versus my advice to others the answer is simple: I have measurement crossover design ability. It's not different than a passive crossover in that regard to me. Others often think is a substitute for having those abilities - THAT is what I object to.
 

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Quote:
Originally Posted by DL86 /forum/post/17249333


Can't I just use room EQ wizard and take measurments from there and adjust accordingly?

That's the REW software, right? You can use it for speaker design but it's pretty limited compared to a real measurement system with crossover design software. The main thing is it ignores phase which is a huge component in getting the drivers to blend. But all isn't lost with the DCX and REW is a heckuva lot better than nothing. Here's what I'd do.


Work on one driver at a time and measure their frequency responses.


Figure out what you want your acoustic targets to be, say LR4 at 1300.


Use the DCX crossovers and parametric filters to shape the response of each driver until it meets your acoustic target. That takes care of everything for a good blend except that pesky phase (time) thing.


The horn's acoustic center will be behind the woofer's so you can fix the phase with a digital delay on the woofer. Temporarily reverse the polarity on the tweeter and play both drivers with all the filters in place. Adjust the delay until you get a deep null at the crossover frequency. That means you've got the phase right.


Put the polarity back the right way and give a listen. If you want to fine tune the voicing, leave the individual drivers alone and use the EQ on the input. Or, if the whole thing sucks, say you are crossing too low or too high or too shallow or too steep, go back and start over.
 

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Quote:
Originally Posted by catapult /forum/post/17251638


Or, if the whole thing sucks, say you are crossing too low or too high or too shallow or too steep, go back and start over.

How would a compete n00b know if they need to adjust the crossover point, type or slope? Save settings and use trail and error?
 

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Quote:
Originally Posted by Looneybomber /forum/post/17251741


How would a compete n00b know if they need to adjust the crossover point, type or slope? Save settings and use trail and error?

Sure that works. With a normal tweeter, you could just EQ both drivers flat and play with different 'factory' crossovers in the DCX. But horns have a very sharp roll-off below 800 or so and that can't be EQ'd flat. So you have to use the horn's natural roll-off combined with EQ and XO filters to get to the acoustic target of LR4 or whatever slope at whatever frequency you want.
 

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Good point from Noah. This thing should be tuned much lower. I haven't modeled a TD15M but I imagine 40hz is probably more in the ballpark than 58hz. Do you plan to use these fullrange? With subs?
 

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Discussion Starter · #15 ·

Quote:
Originally Posted by augerpro /forum/post/17252352


Good point from Noah. This thing should be tuned much lower. I haven't modeled a TD15M but I imagine 40hz is probably more in the ballpark than 58hz. Do you plan to use these fullrange? With subs?

My bad, its actually tuned to about 49Hz the straight area of the port is 6cm excluding flare length, which gives a 49Hz tuning in the unibox spreadsheet.


It doesn't really matter though I will be HPF the speakers at 80hz. I can always tune lower by stuffing one of the ports if I have to.


I'll give that a shot Catapult.
 

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Discussion Starter · #18 ·
Thanks! but i'd probably be tweaking it quite a bit over time so I would prefer I had my own.
 

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Quote:
Originally Posted by DL86 /forum/post/17252792


Thanks! but i'd probably be tweaking it quite a bit over time so I would prefer I had my own.

No worries.'ll be watching with interest to see how this project turns out for you. I'd like to hear it when it's done too if I can.
 

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Discussion Starter · #20 ·

Quote:
Originally Posted by A9X-308 /forum/post/17252871


No worries.'ll be watching with interest to see how this project turns out for you. I'd like to hear it when it's done too if I can.

Sure thing. Hopefully the wait is short for the AE woofers. findbuddha has me worried a bit about the potential long wait.
 
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