Baffle Width

[berlin07]

For Christmas I am looking to build my son some bookshelf speakers. We are leaning towards Bromo’s - https://www.madisoundspeakerstore.co...aker-kit-pair/ . He is currently in an apartment, hopefully in a home in the next year. The plan is to build a home theater once that is done. The Bromo’s would shift to surrounds and Anthology II’s take front stage.

I have these old Parts Express enclosures that I would love to use. I can’t find documentation on them, but if my memory serves me right they are the correct volume- 0.5 cubic feet. Now to the issue/question- the baffle width is incorrect. Bromo kit calls for 7.87”. The PE enclosure is 8.43”. In the real world, how much will this difference affect performance?

We can certainly build new enclosures if needed. I am also open to different designs. I just haven’t found much in two way designs with the SB CAC drivers. I read that perhaps the SBA-61 crossover design is interchangeable??

[technodanvan]

Those are some pretty cabs that should definitely see some use! In the real world we're talking what, a little more than a quarter inch on each side? I'd just put a big roundover on it and call it good enough. I really don't think many could tell the difference.

That said, are you sure those cabinets are 0.5 cu ft? Port tuning could be off if they aren't.

[berlin07]

Those are some pretty cabs that should definitely see some use! In the real world we're talking what, a little more than a quarter inch on each side? I'd just put a big roundover on it and call it good enough. I really don't think many could tell the difference.

That said, are you sure those cabinets are 0.5 cu ft? Port tuning could be off if they aren't.

Thanks for the feedback! These cabinets have been sitting around the house collecting dust for nearly 20 years now. I need to either do something with them or get rid of them!

I’m not a 100% sure on the cu ft … I don’t completely trust my calculations on an odd shaped cab, so I may get out my giant bag of Sam’s Club rice 😁.

[technodanvan]

We might be able to determine which model they are by the exterior dimensions, assuming we can use the wayback machine (or similar) to find the product page.

[berlin07]

Found them! I had no idea sites like wayback machine existed!

DAYTON TWC-0.50BK

Cabinet Finish: Piano Black Gloss External Dimensions: 14" H x 8.5" W x 12.5" D Internal Dimensions: 12.5" H x 7" W x 10.75" D Internal Volume*: .54 cu. ft.

[theSven]

Found them! I had no idea sites like wayback machine existed!

DAYTON TWC-0.50BK

Cabinet Finish: Piano Black Gloss External Dimensions: 14" H x 8.5" W x 12.5" D Internal Dimensions: 12.5" H x 7" W x 10.75" D Internal Volume*: .54 cu. ft.

I have salvaged a tremendous amount of images from the wayback site for this forum. It has been a life saver to restore content with broken links and missing images. Glad you could get some use from it!

[Bear]

Those are some pretty cabs that should definitely see some use! In the real world we're talking what, a little more than a quarter inch on each side? I'd just put a big roundover on it and call it good enough. I really don't think many could tell the difference.

That said, are you sure those cabinets are 0.5 cu ft? Port tuning could be off if they aren't.

Weirdly, the Bromo design calls for square edges, and the diffraction signatures -- while pretty severe -- actually align pretty well between the tweeter and the woofer. I would rate that alignment as being way less important than controlling the diffraction signature overall, but the lack of roundovers seems... completely intentional.

[technodanvan]

You know, I noticed that in the images and did not think to further investigate it. That is an excellent observation.

[chrisn]

It's a small difference, enjoy those nice cabinets The bump around 5k seems to smooth out somewhat by changing the 6.8 uf cap to something smaller, and increasing the .15mh inductor.

[berlin07]

It's a small difference, enjoy those nice cabinets The bump around 5k seems to smooth out somewhat by changing the 6.8 uf cap to something smaller, and increasing the .15mh inductor.

Thanks chrisn! I’ll start a “build” thread soon.

[berlin07]

We started assembly and I noticed that the Madisound pre-built crossovers have R3 and C4 flip flopped in relationship to the diagram. After some googling, it seems to be a hotly debated topic as to whether this makes a difference… So to the gurus:
1. Am I reading the diagram correctly ?
2. do I need to flip R3 and C4?

[Evil Twin]

This is a parallel (to speaker load) series resonant filter, and the sequence of components will have no effect on the resulting behavior. This will create a dip in the parallel load impedance with a corresponding modification of the response at the driver.

[berlin07]

This is a parallel (to speaker load) series resonant filter, and the sequence of components will have no effect on the resulting behavior. This will create a dip in the parallel load impedance with a corresponding modification of the response at the driver.

Thank you!

[Reet]

Not really a hotly debated topic lol, it's basic electrical theory stuff. As Evil Twin mentioned, it doesn't matter the order of series components.

[berlin07]

Google took me to some forums that I have not been on before and the debate was on the topic that you speak too- electrical theory says that there should be no difference, however some members claim that they have built a configuration both ways and gotten different measurements respectively when testing The debate went back-and-forth and back-and-forth …That being said, we all know that there are always plenty of variables involved, especially human error…

Life got real busy for a while. I simply haven’t had the time to study electrical/crossover theory. So “you don’t know what you don’t know”. That being said, as my boys begin to age and move out I’m finding myself with more time(a passion) to become educated on such things.

[eb15]

I've been playing around with these SB ceramic drivers in a Parts Express BR-1 cabinet, and found a retailer had their own 'improved' crossover for the pair, but without values publicly listed, but with their published impedance and reverse null measurements, alongside my preliminary measurements, I simulated something close and then added my own touches to knock down breakup/resonance in vituixcad... I don't have a high quality testing setup with a rotating speaker stand to verify and adjust, and am waiting for some parts deliveries, so it is still a work in progress...

[Reet]

I traced the impedance of SB17CAC35-04 and loaded in your filter. The notches need some re-evaluation, they're not targeting the breakup at all with centre frequenies at 16kHz and 18kHz. You want the notch to land around 8kHz range for this driver.

Try this:

[Evil Twin]

I was wondering about that also, but was pretty busy yesterday, no time to stop look at it in detail. Good catch.

[eb15]

Thank you for your look over. I went over things and yeah, that was just a quick hack to increase roll off with the parts on hand and reduce HF output from the woofer in the simulator, not specifically tuned to the measured resonances.. 0.68uF in parallel with 56ohm and the 0.33mH would give an approximation to the series notch filter (at approximately 10kHz ) used in the SB bromo kit crossover. (~10kHz is where the highest output spike shows in response) 1.2uF there would be close to your example network for around 8kHz.