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Help finding ideal woofer for 2-way design


ElliottDesigns
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Hi guys, it's been a while.

 

I'm currently in the process of designing a 2-way bookshelf speaker that I will want to crossover at 80hz using active filters (meaning I can have the crossover be as steep as I want). The driver I am using as a tweeter (and midrange) is the tebm46c20n-4 by tectonic audio and I am thinking of crossing it over to a woofer somewhere between 200 and 800hz so it is mostly outside of most vocal ranges (or where we are highly sensitive to differences in sound) but also high enough so that it can handle 50W peak (within x-max). I am trying to find a woofer to match which is proving to be difficult, it needs to be under £60 (including import into England if necessary) and it needs to be comfortably capable of achieving an 80hz crossover, preferably being more sensitive than the BMR driver and if possible in a sealed enclosure. Ideally, the enclosure for the woofer is to be 10L or less but it isn't crucial.

I hope some of you can help me with this endeavour since it has seemed quite troublesome so far.

I'll look forward to hearing back from some of you (hopefully 😂).

 

Many thanks,

Elliott Dyson

p.s. loving the sound advice podcast, I'd be happy to come on and discuss BMRs in-depth with you guys if you are looking for a guest. 😊


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TVOR-Ceasar
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Hey there Elliot! Just a couple of questions before wading through the massive mire called the internet. 

I see the Tectonic is a 3" / 7.62cm @ 4 ohm. Also it is rated as 20/40 watts and 86dB 2.83V/1m. 
If I were to search, I'd try to keep with 4 ohm (or equivalent) if possible, though you can mix and match as long as you take it into account for all "matchup" parameters.

The questions:
1. What size (range) woofer are you looking for? For your maximum box size, though flexible, it will limit what's available, size wise. Especially in a sealed / Acoustic Suspension design.
2. Do you have any preferred sites to buy the drivers? I did a quick search and started looking on willys-hifi. This was the first on the list and while going through some of the drivers, I realized I needed to ask these questions.

That being said, this Monacor SPH-135TC, when put into a 10L box will have a Fb of 63 Hz and F3 of around 47 Hz while the box Q will be around 0.66, and that is just using the info straight off the page. You have the option of hooking this up in 4, dual 8, or 16 ohm configuration. Now, they don't tell you what any of that does to the T/S parameters, or even at which rating they measured the T/S parameters, so take this all with a splash of salt.

Many of the other drivers I looked at were higher in their Fb and F3 for an equivalent box size. So, I think I'll wait to see your reply. Spinning wheels is only good when warming the tires for a drag race. 😎 

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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ElliottDesigns
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@tvor-ceasar

Thanks Charlie,

I'm in the UK so sites like RScomponents, sound imports.eu or any other company that ships in England is good for me. Even amazon.co.uk if need be, but I prefer to support non-conglomerate corporations (unless the driver is far cheaper). I'd say I'm happy with any driver under 8" as long as it still fits my specifications, I forgot to mention that I am trying to make it so that the sealed driver is within xmax when crossed over at 80hz at 50W (I don't mind going slightly over xmax at 50W since that is max amplifier power, but not too much). Don't worry about configurations since I am doing separate amplifiers for each driver, each with active crossovers and EQ. Smaller box sizes with a hump shouldn't be a problem (I don't think), since I can just EQ that down to flat so I don't get any of the boominess, I think that's how it works but please correct me if I'm wrong. As for smaller sizes I doubt we can go below 4" due to sensitivity, power, and low end requirements. I've recently acquired AKABAK since I am an engineering student so I will be using it to test out the drivers as well as winISD. I'll have a look to see if the Monacor is available in my country and if it is I'll test out the parameters. Thanks for helping me with this, I really appreciate it, it should be a fun project. Hope to hear from you soon! 🙂


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ElliottDesigns
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I had just realised you were talking about multiple drivers when talking about configurations, ideally I would just have the one since I have plans to use them as satellites for a home theatre system. I will start off with two and keep upgrading until I am using the speaker for 5 height level channels and 4 ceiling channels, that is a long way away though. For quite a while I will just be using them for 2.1. (I say home theatre but I will be using them for music too!).

P.s.If anyone wants complex simulations I would be happy to do them in AKABAK when I have figured out the program. This includes generating polar patterns and testing custom horns for specific drivers. It's the least I could do to give back you guys.


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ElliottDesigns
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Sorry, I see what you mean now. It's a dual-voice coil speaker, so that's what you meant by configurations (I got there eventually) and it looks pretty amazing so far. Time to get to simulating... 😉


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ElliottDesigns
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Thats a real shame, that driver initially looked really well suited to my requirements, but no matter what I do with the driver in winISD the excursion is only linear up to 20W of input power at most. I think I need either a similar sized driver with a lot more xmax or it just needs to be a bigger driver. Good find though, it's better than any I've found so far, you really have a knack for finding good drivers Charlie!

P.s. I just realised how much I have written out in these posts, I am so sorry for anyone reading through that mess 😅


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ElliottDesigns
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umm, really confused here. When I put the BMR driver into winISD and set input wattage to 50W (or anything for that matter), for whatever reason no other driver is getting up high enough on the spl graph to match it, now that is really strange since tectonic lists the spl as 85. I think I'll stop for today since this is driving me crazy as I cannot figure out what is going on for the life of me.


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TVOR-Ceasar
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When you are running your Sims, do you have the ability to do bandpass signal, say 80 Hz to 400 Hz with say 18 - 24 dB slopes at either end? Might help with excursion, especially if you go with a slightly smaller box, That'll raise the Qbox slightly, which will push the Fb and F3 up accordingly, as long as you don't go too far past your target Fb. 

Satellites, rears, and height channels, got it now. So you could go with smaller boxes. I'll look again a little later.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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ElliottDesigns
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@tvor-ceasar

Thanks again Charlie, greatly appreciate it as always, I do have the option to bandpass in the sim so I'll try that again tomorrow since I'm done for the day I think. Do you have any idea what was happening in winISD with the BMR driver I was using by any chance, it seemed like quite strange behaviour?


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TVOR-Ceasar
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Are you using a larger than optimal box for the BMR? The larger the box, the less back pressure you have which could lead to less control and over-excursion.

I tend to initially use my QBasic programs to quickly evaluate drivers. All these use are the Fo (Fs), Qts, and Vas of the driver, which then gives me a box size, port length is I chose ported, Fb and F3.  I have the option to play with the box size to see what I can get out of a driver, but generally, I like to try to stick to the optimal designs. 

WinISD takes too long to enter all the driver parameters if it's not already in the database. I can check out 5-10 drivers in QBasic before I can get one in WinISD. That's why I hold off. If something looks real promising, then I'll go to WinISD to get down to the nitty gritty.

That being said, I haven't put the BMR into WinISD, so no real clue as to exactly what you are seeing. If u have time after work, I'll look. In the meantime, let me know what size box you are using. I gather it's a sealed box, from your earlier comments.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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ElliottDesigns
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@tvor-ceasar

No don't worry I'm using the natural slope of the BMR when it is situated in a 0.24L enclosure. This enclosure will mean xmax isn't reached at full power since the slope will be increased to a 3rd or 5th order depending on how it works out with the midbass driver (easily adapted anyway since it will be active). Your system of finding drivers sounds very interesting, is the software you use free? Also I figured that the strange offset in winISD means at most that I just want a more sensitive driver, probably 88db or above I would think unless we can trust the manufacturers claim for the BMR of 85db 1W 1M over winISDs obserd values for SPL. I am starting to get my head around AKABAK now but for me in England I will be settling down for the night soon so I'll work on it more tomorrow. Yet again thanks for all your help so far. It's nice having someone to help on a project when you are completely stumped, I hope I can return the favour someday. 😉


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TVOR-Ceasar
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@diyaudiphileelliottbridge

Got it, re: BMR box -n- slope. I'm on my way to work ATM, so I'll give it a check later, just to see where it sits, Q and Fb - wise. 

The QBasic stuff is a bunch of routines I've written over the years. The more I learn, the more I see areas that could use some attention, but those are places where I made assumptions. If you search back, you'll see where I was working on updating things to be more comprehensive and want to release it here so everyone can benefit. Big deal is that being QBasic, it is still 8-bit, so you need an emulator. I use DOSBox and have it set up to launch Basic right away. Quite convenient. Maybe I'll just combine the "quick version" of ported, sealed, and. Transmission line all into one and have it all presented on 1 screen. Hmmmm...

Re: helping - as Nick said, this is a place for all of us to learn. I'm sure you will be teaching me things along the way just like Nick has been dropping the knowledge for us left and right. 

Have a good night. Catch you on the flip side.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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