Something Stirs in the Workshop

[vinylnvalves]

Did an additional test on the TPL’s today- some suggestions that adding a flat face will increase the LF extension. Did this - no affect what so ever on the response. Was expecting to see something, in the FR but no. So it looks that with my horn a 1000hz is as low as I can really go.

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[steve s]

Did an additional test on the TPL’s today- some suggestions that adding a flat face will increase the LF extension. Did this - no affect what so ever on the response. Was expecting to see something, in the FR but no. So it looks that with my horn a 1000hz is as low as I can really go

Thats alot lower than mine go Steve.
I've got 2 drivers below, which I know your trying to avoid.. but to me well worth it

[vinylnvalves]

Yes - I have the midrange AMT’s which cover 300hz to 4000hz. So technically that’s better than have a crossover at 1000hz, but I do wonder if for the midrange, the surface area of a 12” driver will have its benefits. To many options, the current arrangement sounds good...but would the Beymas TPL’s sound better further up the running range. I know you reckon they need a supetweeter, which is another consideration. I need to generate a straw man of all the options.

[chris661]

Steve, those speakers are referenced on the DIYA thread. I think the consensus was that the clamshell is orientated the wrong way because the dipole nulls will be at the front and rear. Or am I missing something?

You're missing something.

Look at the picture again - the baskets are covered on the front side, so you've got the front side of the cones firing forwards, and the rear side of the cones firing rear-ward.

ie, dipole radiation.

You also get force cancellation from the cones moving in opposite (mechanical) directions.

Chris

[vinylnvalves]

Yes I have been reading the same threads to.. I am not sure about the circles of doom, I think you need the surface area to make them work properly. I am not sure what the polar plots will look like.
I have been trying to understand these better... to see if the downsides of the ripole can be designed out. https://6moons.com/audioreviews2/ecobox/2.html
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From that link

Team less echo (and no box!) refine that recipe. Facing their woofers at each other does some useful things. It lowers their resonant frequency to increase bandwidth and output. It raises radiation resistance for higher pressurization and superior cone breaking power over lossier standard OB woofers which face an entire room's cubic air volume.

In my view thats how my speakers work. The lower resonant is nothing new
The drawback is that increasing cone pressure decreases the drivers ability to follow the signal, probably enhancing low notes with a little distortion .. but most ported speakers cause some change, its about how audible it is, and if you hear it.

I do wonder if what I was hearing in my listening trials yesterday was distortion due to the asymmetrical loading of the driver. The H frames are at least 10db more efficient than the clam shell arrangement. I like this as a concept, I would recess the drivers so they were loaded front and back equally with a plug of air.

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. With the drivers I have building on Siegfrieds established design is probably less problematic, which an H frame or W frame is.

Technically isobaric loading in a seal cabinet, with good damping should be a good solution from a biradial polar plot perspective, with respect to room modes.

[vinylnvalves]

I was asked whether I could supply a smaller horn to go on top of the ES290 horn. Here’s my first attempt, a test run to see what issues I would have. Horn profile, from Joesph Crowe, external styling by me to match the bigger horn. It’s a ES1200 horn with a 1” throat.
These are small horns - only 220mm wide, watch making in comparison to what I normally build. (Not sanded properly- just oiled to show the grain.

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[iansr]

Nice Steve. You’re tempting me . . . .

Presume these are going to the other ES290 owner?

[vinylnvalves]

No they were for a speculative enquiry, no customers yet, however the other you mention may be interested. I think I might get Chris to measure this one and see what it’s FR is like. As I don’t have any 1” compression drivers.

[iansr]

Steve
Given your pursuit of a bass solution I thought you might be interested in the speaker that XRK is working on ATM:

https://www.diyaudio.com/community/thre ... 08/page-33

XRK is a one man industry and is clearly a pretty smart guy.

[vinylnvalves]

Eventually got around to finishing a pair of the HF Horns. I ended up modifying the design so the mounting of the drivers is not into end grain but onto 9mm ply. These were finished in Danish oil, personally I think it makes them to dark
Hopefully Chris May get some time to measure the one I sent him.

I will be posting them for sale on one of those other non technical audio sites

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[chris661]

Sorry Steve!
A bout of Covid has knocked me on my arse. Hoping to be back to normal service soon.

Chris

[vinylnvalves]

Chris, sorry to hear the Covid affected you so bad. WB must be a dangerous place to work. I was only a stone throw away from you last week when I went to Unstone Hall to pick up a tonearm.

[vinylnvalves]

Now that work is starting to calm down, and with operation “ energy saving “ the end is insight, I can now focus back onto audio stuff.
First on the agenda is to sort out the bottom end. I have been using some LF modules fromthe Linkwitz LX521 speaker which tick a lot of boxes, except they need space to breath. So am looking to repurpose the SEAS 26LROY04Y into some different cabinets that can go closer to room boundaries, but still utilise the strengths of the drivers.

I have been looking at cardioid designs, which I believe should help with the boundaries.

I saw this concept, it intrigued me. I am struggling to understand how the Helmholtz resonator helps in this concept. Unless there is a spike in the response, I don’t see how the high Q suck out at 60Hz will help.
I

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[vinylnvalves]

having simulated it it doesnt look to bad

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when compared to a sealed box version

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a bit of work to do to get the SEAS drivers as good

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[vinylnvalves]

Any feedback from the speaker design gurus... Not sure if my approach of making the vent in the second cabinet short and a very small diameter is the best “ bodge” with the tools available?