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Old 10th October 2002, 10:00 PM   #1
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Default My first DIY, biting off more than I can chew on purpose!

Hello all,

I currently have a Snell HT setup with 5-LCR500's, 2-SUR500's and 2-SUB550's. After reading an article on Dunlavy in Widescreen Review and his supsequent series of articles, I haven't been able to get him out of my head.

His beliefs are that first order, time aligned, phase correct line source systems are the way to go.

Has anyone cloned his SC-IV A? I think that the IV specs are what I would like to shoot for. Perhaps a litle smaller footprint if possible.

Barring a clone, I guess I would start with Speaker workshop but have been also looking at Soundeasy. Is anyone using this?

I know I'm biting off a big chunk but the best way to learn, (at least for me), is to dive right in and solve what you can and ask questions on what you can't.

It seems like this is the right forum to attack such a project. Am I correct?

Any comments or suggestions would be greatly appreciated, (except building a kit..I'd rather learn by doing!).

TIA,
Phil

How do you eat an elephant? One bite at a time!
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Old 10th October 2002, 10:59 PM   #2
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Nice thing about DIY speakers, if you can use a saber
saw you can build a speaker and it will work and not
catch fire. All else is refinement.

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Old 10th October 2002, 11:14 PM   #3
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Nelson,

That's the spirit!

Phil
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Old 11th October 2002, 12:56 AM   #4
f4ier is offline f4ier  Australia
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JohnK's site might interest you

Isaac
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Old 11th October 2002, 02:44 AM   #5
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Default DIY Time Alignment

Speaker Workshop will work fine but you should build a Wallin jig to help calibrate the sound card and even a mod on the soundcard (for more output) would help, getting a good Reference for varying loads with repeatable results is very difficult and takes quite a bit of tinkering if you donít build a jig of some kind.

Read everything you can and develop a idea of what specific design philosophy you want, the clearer an idea of the results you wish to achieve, the easier the computer modeling will go.

Drivers;
Pick your drivers carefully, if you see 10 different manufacturers using the same combo of available DIY drivers together, then there is a good bet that they work together pretty well. Or you can spend the time modeling them in the software, but this is difficult because the published specs often differ from the actual T/S parameters. I like to use the R&D of successful designs and then expound on them a bit.

Crossovers;
These are the project killers, they can truly make or break you, if youíre not already doing a well-designed proven kit then I would stay away from difficult drivers that need compensation networks for resonance peaks, or stay away from the peaks by carefully matching drivers and selecting a crossover point that will stay away from the trouble region. If you select drivers that naturally work well together without complicated networks then I would strongly suggest that you go Active, at least for the design stage, then you can copy the alignment in a Passive design once it sounds right. The Active crossover route scares most people off because of the cost, but it really isnít that bad, Iíve used car crossovers (Nak EC-200H and 200L) for listening tests and it reveled the true nature of the speakers ability to work together at different selectable crossover points that (you can switch 4 points on the fly), also the high slope rates help for easy integration. Then once you have done all your listening tests you can select what crossover point you want and alignment based upon your modeling and listening tests.

Enclosure;
Stick with an easy enclosure and order alignment like a 2-way sealed, they can always be demoted later to rear speakers if you get a felling for going wild on a more difficult design. If you donít fell like doing all that research and posting questions all over the Internet on driver and crossover details, then I suggest you stick with a proven kit for the first time around.

Time Alignment;
If you really want to do the ďTime AlignmentĒ thing then I suggest you make either a prototype enclosure with adjustable baffle depths or make each drivers enclosure separate, and a stand that will allow for the enclosures to be adjusted fore & aft relative to the Tweeter (or you can get close and just tilt the cabinets). Then you can use Speaker Workshops Gated signal to Time align the drivers relative to one another. Iíve done this and I have learned a lot, the more adjustable the better, time alignment is for real a project like this will make you believe.

Wallin jig
http://www.gti.net/wallin/audio/jig2/jig2.html

Sound card Mod
http://www.gti.net/wallin/audio/ensoniq/ensoniq.html

If you donít already know about this site then go there for your questions first.
MAD Board
http://www.madisound.com/
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Old 11th October 2002, 03:54 AM   #6
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Kingdaddy, how did you use a gated measurement to measure the relative delay of the drivers?

I tried looking for peaks in the pulse response, but the sample rate of the soundcard is too low, which means this method is too coarse (20mm resolution).

I then used Dick Van Nierop's method of subtracting the measured phase in excel. This worked and I got an answer of about 50mm for a focal TC120 tweeter and 7NV woofer at my crossover freq - 2.4khz.

After some listening tests I decided that recessing the tweeter 50mm created more problems that it solved, and ended up recessing the tweeter 10mm - which holds a 9.5mm bit of felt in nicely.

Mark
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Old 11th October 2002, 04:30 AM   #7
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My recommendations were based on both practical experience and Theory, my practical experience is very similar to yours, the measurements say one thing and your ears say another, thus a compromise, thatís why you should do both. With totally separate adjustable enclosures you can do this more easily.

For Gated measurements the set up is different for each environment, you have to set the Gate Short enough to not pick up secondary room reflections and long enough to go to the lower registers (only for midís and woofers) of the frequency spectrum. Everything is a compromise thatís why there are no absolute written procedures for any of this, itís just too dynamic and differs from application to application. In the end I just used the method that sounded best to my ears. I definitely believe in Time Alignment but I think there is still a lot (for all of us) to learn, and no one has completely figured it out IMO. Time Alignment so I've read is relative to your position (distance) to the speakers and the crossover frequency, and IMO there is no way at present to satisfy all things at once, so a compromise is needed.
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Old 11th October 2002, 04:55 AM   #8
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f4ier,

Thanks, I have seen that site. I even tried to e-mail him about the TP-3W but his e-mail address is no longer valid. It does seem very close to what I would like to do.

kingdaddy,

Thanks for the links! I think I already have an idea of what I want.

35-20K +/- 1.5dB
flat phase
time aligned
line source
95-100 dB
1st order XO's if possible.

Is there anything I am missing? Am I nuts?

If the goals look close to the Dunlavy SC-IV A's, your right!

Good point on the drivers. I do have some friends of friends that are helping me along in that direction.

XO's:

On crossovers, that where the fun will be. I have done extensive analog engineering so I am fimiliar with the basics. It's when the circuits get tied to speakers that the real challenges will appear.

I also have a car 3 way XO as well as a Bryston 10B. The Bryston is a real help since you can also vary the slopes between 6, 12 and 18 dB/ as well as adding boost or cut.

Boxes:

I was thinking about doing just that, start with 3 separate sealed boxes, (MTM). Once that is straight, then go on to the W's.

So this forum isn't appropriate for my project? Am I insulting this forum by posting? That certainly wasn't my intention

Is madisound a better place for me until I catch up? I guess I'll have to stop by and see what's cookin' over there.

Thanks all,
Phil
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Old 11th October 2002, 06:11 AM   #9
navin is offline navin  India
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dear phil,

relax we discuss everything here. you ca ofcouse browse or post where ever you please but please dont get offended.

if nessacary one of the 18 stone moderators Jason promised will be there to sort things out.

i have been toying with an idea simialr to yours.

I started with 2 12" from Audio Concepts (SV12), 2 6" ScanSpeak 18W8546 and 1 Scan Speak 9900.

what stumped me was WAF. The foot print far exceeded the 1' x 1' I was limited to. actually I ended up with boxes that weere 16" x 24". I built 3 boxes. one for the MTM and 2 for each of the subs and aligned then WMTMW. The MTM box did not need much alighment as the 9900 has a slight horn that aligns the voice coil with the midbass.

anyway given WAF the only option was to build the subs in coffee tables and plunk the MTM on a stand.

I can provide photos of what I ahve done. I built this system in 1997. I seem to work in fits and starts. I was into audio in 1976-1980 then gave t up till 1986-88 then gave it up till 1996-97 then got interested a few weeks ago again! How long this flitation will last I dont know.

On each occasion I gave it up de to back biting, flaming, within the group I was (the internet was not there in 76-80 and 86-88 but I was involved in various audio clubs and these clubs disintegrated once the back biting and flaming and name calling started). I hope this does not happen to diyaudio.com. If it does...oh well.

regards
navin
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Old 11th October 2002, 08:18 AM   #10
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Navin,

Thanks for the encouragement! I only found out about this forum a few days ago and haven't quite gotten the feel of the place yet. The last thing I want to be is annoying since I also like calm forums. Speakers are probably the worst area for people to agree on since there are so many tradeoffs to weigh.

I pretty much laid out the specs of what I wanted to do so I think the next step is to get up to speed with Speaker Workshop. I am also looking at Soundeasy as it seems more complete and is reasonably priced.

Do you know about either of these?

Of course I'll be scanning the threads for speaker recommendations. Some initial feedback I got from a friend is that the Seas Millenium tweeter #T25CF002-06 gets high marks but it's kinda pricy. I also got a nod for the Vifa mid #PL11WG-09-08 so there's a begining.

I am also trying to juggle all the trade-offs in my head re crossover frequencies, baffle limitations, etc. so this project should keep me entertained for some time to come, (that's what hobbies are for afterall ).

Here's a scary thought. My friend also mentioned doing digital filters of each individual driver using an M-Audio 1010 sound card and DSP software to do flat response and zero phase, (for the sweet spot only, of course).

Essentially he is doing DSP processing on each driver to make the whole system 'perfect'. Since my system is a 7.3 can you imagine 24 amp channels and 3 8 channel 1010-s driving them? Yikes!

Oh well, back to the simulator tomorrow.

Thanks again,
Phil
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