{"id":1343,"date":"2022-01-02T20:21:47","date_gmt":"2022-01-03T04:21:47","guid":{"rendered":"https:\/\/totallyshould.com\/?p=1343"},"modified":"2022-01-03T19:41:07","modified_gmt":"2022-01-04T03:41:07","slug":"barn-speaker-redo","status":"publish","type":"post","link":"https:\/\/totallyshould.com\/?p=1343","title":{"rendered":"Barn Speaker Redo"},"content":{"rendered":"\n

Back in 2003 I worked with a college friend to build a big set of speakers, and in 2015 I did some updates to make them somewhat less terrible- I wrote about that here: https:\/\/totallyshould.com\/?p=870<\/p>\n\n\n\n

One big problem with these speakers was that they were really not capable of producing much bass, and it took so much EQ to balance things out that they really couldn\u2019t play very loudly. They sounded kind of boomy and hollow, probably due in combination to the walls flexing, the ported box tuning, and the sparse batting that was intended to (but did a poor job of) absorbing internal resonances. I wanted to see if I could really make them deliver on the promise of a loud barn speaker with some hifi sensibility.<\/p>\n\n\n\n

There\u2019s a project out there that I\u2019ve heard of but didn\u2019t pay much attention to, the Econowave <\/a> . I didn\u2019t copy it, but I took it as inspiration and found some drivers and a horn. I used the GRS 15PT-8<\/a> as a 15\u201d woofer, the PRV D280-ti<\/a> and the Dayton H6512 waveguide.<\/a> At the time of this writing this was about the cheapest combination of parts that I could find that would give significantly higher efficiency and bass output in the existing 4.25 cubic foot box. <\/p>\n\n\n\n

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Power supply, Minidsp, Sure 4×100 watt amp board <\/figcaption><\/figure>\n\n\n\n
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No extra bracing yet, but lots of fiberglass <\/figcaption><\/figure>\n\n\n\n

I decided to skip the port with these. I no longer have access to the Mathcad worksheet for simulating mass loaded transmission lines, and I didn\u2019t think it was worthwhile to do learn how to do it in Hornresp – it really would have taken something like that instead of WinISD to do it predictably because of how tall the box is. Instead, I checked the numbers for excursion limited bass SPL and decided that a Linkwitz Transform<\/a> was the best way to go. According to WinISD I would be able to extend the bass another half octave lower without running out or power or excursion as long as I also added a steep highpass. I took -3db point from about 60hz down to 35hz, and then added a 24 db\/octave highpass at 30hz. <\/p>\n\n\n\n

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Old speaker with new drivers ready to go in<\/figcaption><\/figure>\n\n\n\n

I used a new (to me) measurement technique to dial these in. I used something called the \u201cMMM moving mic method<\/a>\u201d to perform something resembling an anechoic on-axis measurement of the speaker. The way this is executed is by playing periodic pink noise while taking an average reading on a real time analyzer while randomly moving the mic around the zone of interest. In this case I swung the mic up and down several inches in front of the tweeter and woofer, taking care to keep it moving and not linger in one area too long to too often. In other speakers I\u2019ve checked it\u2019s pretty repeatable. Shout out to Joentell<\/a> for pointing me toward this method and working with me to get it going.<\/p>\n\n\n\n

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On-axis close mic MMM measurement of the final iteration of the barn speaker <\/figcaption><\/figure>\n\n\n\n

Ultimately the on-axis response that I\u2019ve created should be a flat horizontal line. it\u2019s not, and there are a number of problems with it. Rather than tear it apart and talk about what\u2019s separating it from a $10k reference monitor like the JBL M2<\/a>, I\u2019d like to focus more on what it\u2019s able to get done for this all-in price of around $250 per speaker (not counting discman, labor, or wood).<\/p>\n\n\n\n

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Tuning the barn speakers a little closer than the final distance <\/figcaption><\/figure>\n\n\n\n

One thing that I noticed with these speakers is that the tweeters and woofer are fairly directional. This is to be expected, and I\u2019m sorry I didn\u2019t have time to measure that, but it means that as you move away from the speaker the highs don\u2019t fall off as quickly as a lot of the home speakers I have experience with. For this reason I kept the absolute level of the tweeter just a bit lower than the measurements might suggest. In the future I\u2019ll do a re-tune when they are in their final home, but for now they\u2019re still just a bit bright since I anticipate they\u2019ll get used from a greater distance than the chair. <\/p>\n\n\n\n

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Close-mic response (blue) and at about two meters, MMM with psychoacoustic smoothing <\/figcaption><\/figure>\n\n\n\n

Finally I did some distortion tests to make sure that the bass boost wasn\u2019t too aggressive and the tweeter wasn\u2019t stressed from the low crossover. The above graph may not be what people are quite accustomed to seeing. <\/p>\n\n\n\n

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Relative distortion at ~2m. Call it about 85db average<\/figcaption><\/figure>\n\n\n\n

Here\u2019s another way of presenting the same data. It shows that above 100hz distortion mostly stays below 1% at 85db at two meters. Compared to home audio equipment that\u2019s respectable! <\/p>\n\n\n\n

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Distortion represented as a percent relative to fundamental<\/figcaption><\/figure>\n\n\n\n

That just about wraps it up. These things have some new life and in their latest form make Pink Floyd and Emerson Lake and Palmer a lot of fun. Thanks for reading!<\/p>\n","protected":false},"excerpt":{"rendered":"

Back in 2003 I worked with a college friend to build a big set of speakers, and in 2015 I did some updates to make them somewhat less terrible- I wrote about that here: https:\/\/totallyshould.com\/?p=870 One big problem with these speakers was that they were really not capable of producing \u2026 Continue reading → <\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/totallyshould.com\/index.php?rest_route=\/wp\/v2\/posts\/1343"}],"collection":[{"href":"https:\/\/totallyshould.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/totallyshould.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/totallyshould.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/totallyshould.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1343"}],"version-history":[{"count":8,"href":"https:\/\/totallyshould.com\/index.php?rest_route=\/wp\/v2\/posts\/1343\/revisions"}],"predecessor-version":[{"id":1364,"href":"https:\/\/totallyshould.com\/index.php?rest_route=\/wp\/v2\/posts\/1343\/revisions\/1364"}],"wp:attachment":[{"href":"https:\/\/totallyshould.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1343"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/totallyshould.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1343"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/totallyshould.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1343"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}