Frequency Response Graph for ATC SB75-234SC - diyAudio
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Old 10th January 2013, 11:15 PM   #1
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Default Frequency Response Graph for ATC SB75-234SC

Hi

I am struggling to find frequency response curves for the 9inch short coil bass driver from the ATC SCM50 Cabinets. I am building my own cabs usng drivers bought from wilmslow audio, and it would be of great help when determining cabinet height to know the response of the bass driver. Any help gratefully received. I have tried googling but to no avail.

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Old 11th January 2013, 08:14 AM   #2
LJNorth is offline LJNorth  United Kingdom
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If you are going to buy $$$$ ATC drivers then a proper measurement setup is the only way to go, and to measure them yourself on your own baffle..etc,etc,etc, - are you going to design your own crossover? if not I hope you will use an existing design which will be optimised for an existing baffle - problem solved - stick to the established design, as for Wilmslows designs??? I have seen mixed comments

I suspect this is why no one has replied
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Old 11th January 2013, 08:55 AM   #3
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I have the designs for the ATC crossovers from another thread on here. It uses a different tweeter though so I will design my own high pass for the tweeter. I can map the resonances of the tweeter and make it appear as a stable resistance with some circuitry so should be able to make a more detailed crossover than the simple 2nd order that ATC use for their tweeters.

How would you recomend I measured the bass driver? I have heard about software which emmits a very short sinewave pulse which arrives at a close reference mic, before the pulse has had any chance to reflect of any nearby walls. Is this sort of software reliable though? Do you get good, repeatable graphs from this?

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Old 11th January 2013, 11:44 AM   #4
LJNorth is offline LJNorth  United Kingdom
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without measurement equipment you are shooting in the dark, any change to the tweeter/redesign of the crossover will need acoustic measurements, you are probably wasting your money if you dont use measuremements. If you have allready invested in the drivers then I would reccomend following somone elses design to the letter (use the same tweeter), baffle shape, size and room position have a big effect on the acoustic performance of a speaker, just correcting tweeter impedance with a Zobel is unlikely to do it justice. Measurement equipt. is cheap these days, you just require knowledge and experience to use it....
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Old 11th January 2013, 02:05 PM   #5
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I was looking at the original design of the crossover, all it is, a 2nd order filter. Its very basic stuff, and very blunt as well because all the components will behave differently dependent on the varying impedence of the tweeter. I would be very surprised if this was a choice by Atc based upon acoustic reasoning. I could be persuaded that they saw no audible acoustic advantage in making the crossover more complex for the tweeter though.

I will definitely be purchasing some test equipment of my own though, is there any you would recommend? I might have to talk nicely to my local uni, see if they have an anachoic chamber

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Old 11th January 2013, 03:40 PM   #6
LJNorth is offline LJNorth  United Kingdom
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There is plenty written about measurements on here, the search bar is your friend. For starters hardware - soundcard/usb mic preamp, I use M-udio mobile pre because it has a built in phantom supply for the mic. as for measurement mics dayton/PE do a calibrated one for cheap, I use a beyer MM1, or you could go crazy i.e. B&K, then software is Holm or ARTA both free, then you need to learn up - read posts here to start. You dont need an anechoic chamber with modern time domain gating and FFT/deconvolution algorithms, although to have one at your diposal is nice.
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Old 11th January 2013, 03:56 PM   #7
LJNorth is offline LJNorth  United Kingdom
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I suppose I should add that even after measurements you will be in for a challenge designing a 3 way (I assume you are using the ATC mid-dome). But if you post measurements you are more likely to get a favorable responce from people here. You dont mention if you have much experience at DIY, if not you have certainly jumped in at the deep end, usually people reccomend starting with a well documented/designed and simple, moderately priced 2-way from, for example, Zaph then graduating onto more complex things. If you dont enjouy building / designing / the physics and just want a top quality speaker then factoring in your time and effort and parts etc. you may be better off just buying an ATC complete speaker, if you would just like to build then use someone elses design - it will save years of work.

Laurence
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Old 11th January 2013, 04:21 PM   #8
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Old 11th March 2014, 09:42 AM   #9
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I am in the same need. Anybody with measurement or T/S parameters for ATC SB75-234 SL version. I mean it, SL version.
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Old 11th March 2014, 10:18 AM   #10
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I never did find any measurements I'm afraid. @LJNorth, I should have said, I have been building speakers since I was 13 so this is by no means something I am new too I have designed plenty of amplifiers, crossovers, both active and passive, and I am lucky enough to have a lot of resource available as my father is technology director of a hi-tec engineering firm in Cambridge. I ended up going for an active crossover in this project in the end. The guys at ATC were incredibly helpful, and provided information on the voltages of the amplifiers they used for each driver and anything else I needed to know.

They now sit happily in my studio, making a lovely sound. Only problem is, like most of my personal builds, I am a function over form person, so they haven't been painted, just sit in bare MDF! I never could be bothered to paint/veneer things once I could listen to music on them! My girlfriend wants me to decorate them one day though, but I just can't see the point as they won't be moving and venner won't make them sound any better!
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