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Multi-Way Conventional loudspeakers with crossovers

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Old 10th October 2013, 01:24 AM   #1
inguz is offline inguz  United States
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Default OB with pro drivers

My new build is a pair of open baffles with pro drivers - 15" JBL and horn.

This is my first OB and I wasn't sure it would work at all.

I've been running a variety of horns for a while, ending up with big 2360 butt-cheeks, which served me very well for several years. Then last month it seemed like a good time to get rid of all that stuff and try something new. But without buying a lot of new drivers, since I'm well stocked with pro gear - a few 15s, a couple 12" EVs, some 1" and 2" compression drivers, and so on.

Back in ancient history, some of the best things I heard were Quad ESLs, and Celestion SL6000 dipole woofers (unfortunately not together...!). The big system was loud and precise but the bass was never right, always boomy. (My listening room is an attic with low sloped ceilings).

So this all started literally with open drivers on the floor. They actually sounded amazing. So for practicality and aesthetics I built some nicer oak baffles, which I'm quite pleased with. Starting this thread to write something about my approach, and hear from your experience on better ways to go about this.

A couple pictures attached, and more here.
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File Type: jpg 2013-09-22-ob2.jpg (613.2 KB, 321 views)
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Old 10th October 2013, 01:42 AM   #2
Pano is offline Pano  United States
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You're on the right path and the baffles look nice.
For a few years I ran a 15" woofer topped with an Altec horn on OB. I liked it a lot, so did a lot of friends. Getting the crossover right was a big learning experience, tho.
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Old 10th October 2013, 01:47 AM   #3
inguz is offline inguz  United States
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Open speakers on the floor actually did sound good -- after adding compensation for the dipole rolloff.

Here's the RC network I put together. It's basically a fairly heavy bass shelving filter. Additionally for safety I have a 20Hz highpass (digital), because although the XMax on these woofers is fairly decent, I have lots of electronica with subsonic weirdness and playing it too loud would be an expensive mistake.

This setup with no baffle was a real eye-opener. The bass was there, but unobtrusive and smooth. The overall effect was quite enchanting.
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Old 10th October 2013, 02:07 AM   #4
puppet is offline puppet  United States
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I'm with you on the simple no baffle effect. I've been fiddling around with a naked 4-way for about a year now and find it quite nice. I really think the "ideal" would be a 4-way naked with sealed sub(s) .... below 50-60hz. Don't have to worry about hurting any of the naked drivers that way.

I don't use mini DSP for my active set-up ... rather an older pro (EV) DSP. There are fewer EQ functions so I had to pay closer attention to each drivers natural response and use that to an advantage with the crossover points. EQ'ing the heck out of they're response(s) didn't appeal to me sonically. The sum always had a "forced" sound to me.
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Old 10th October 2013, 01:48 PM   #5
inguz is offline inguz  United States
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Some measurements of the final speaker, from listening position. These have 1/48th octave smoothing applied, to hide some of the ragged spikes. The full-range combined measurement has a crossover at 1kHz.

There's something wrong with the top end; it's very rolled off. Later...

The bass is surprisingly flat, and strikingly free of any obvious room-mode suckout.
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File Type: jpg bass-ir.jpg (168.4 KB, 262 views)
File Type: jpg top-ir.jpg (150.7 KB, 256 views)
File Type: jpg in-room-response-48.jpg (165.3 KB, 89 views)
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Old 10th October 2013, 09:35 PM   #6
Pano is offline Pano  United States
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Thanks for the graphs. I have to say that I am VERY surprised at the bass response. How far back in the mic? Is that done using your line level EQ?
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Old 10th October 2013, 10:45 PM   #7
badman is offline badman  United States
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Regarding the rolled off treble- your midbass is too efficient. I suspect you're getting reinforcement from the floor to a higher frequency than one might think. Providing CD eq can take those 110dB comp drivers down to mid-90s very quickly- of course, they're still crazy efficient, just not crazy sensitive because of the filter.

Details on XO?
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Old 11th October 2013, 12:17 AM   #8
inguz is offline inguz  United States
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Microphone was just forward of the usual listening position, 10 feet from the speakers. In the picture, that's a foot above the laptop.

The picture reminds me. Every time I go up to the attic, one of the great things about these speakers is they smell really great. Tung oil finish.

The bass is a surprise still. It goes deep but in a completely different way to anything I'm used to.

The only EQ is that R-C network after the bass DAC, and a resistive L-pad on the compression drivers to manage their level, and a 20Hz highpass to protect the drivers.

I'm using a NanoDigi for crossover duties and the highpass protection, fed S/PDIF from a Squeezebox Transporter. When I first started using the nanoDigi, it didn't sound at all great at 44kHz, which I attributed to ASRC (rightly or not, I can't really tell). So I'm upsampling everything to 96k with sox first (rate -v -s -I). CPU is cheap!

Crossover frequency is 1kHz right now, and the slopes are 48dB/octave Linkwitz-Riley just because they're the steepest. The bass is delayed by 23cm (acoustic distance between the bass and tops, based on the impulse response measurements). I love the flexibility of being able to dial in delay plus off-the-shelf crossover at whatever frequency sounds right, and haven't even tried to go deeper into custom biquads or whatever.
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Old 11th October 2013, 12:35 AM   #9
OllBoll is offline OllBoll  Sweden
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Quote:
Originally Posted by inguz View Post
Crossover frequency is 1kHz right now, and the slopes are 48dB/octave Linkwitz-Riley just because they're the steepest.
Are you sure you want such steep slopes? If I remember correctly the experts ( Linkwitz, Bruno Putzeys and others ) use 24db/oct as guideline since steeper filters have a significant problem with pre ringing off axis. Unless you are really pushing the drivers to their limits then 24dB/oct should be enough anyway =)
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Old 11th October 2013, 12:43 AM   #10
inguz is offline inguz  United States
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I think you're probably right. Also 1k is at the low end, and could comfortably go higher. The raw response for each driver overlaps plenty far enough.

Do you know any specific things to listen for? (I've not managed to distinctly hear pre-ringing artifacts before).
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