SLOB project

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Toppsy
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#256 Re: SLOB project

Post by Toppsy »

OK.
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Ray P
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#257 Re: SLOB project

Post by Ray P »

Also, I think it would be very simple to add a higher order filter on the front of the chip amp if required.
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Ray P
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#258 Re: SLOB project

Post by Ray P »

A question regarding passive filters. You can obviously end up with numerous combinations of R & C values to achieve a give corner frequency. Is there a 'best practice' reference that I can check out with respect to selecting those values, for example, for a lo-pass it feels as though you should keep the R quite low in value and go with a larger cap but that may just be my ignorance talking. Any steer would be useful. Cheers.
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vinylnvalves
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#259 Re: SLOB project

Post by vinylnvalves »

http://www.t-linespeakers.org/tech/filt ... eHLxo.html

The high pass is always more challenging as the input impedance of the amp is needed, no different to a speaker crossover.

If you don’t want to introduce to much resistance into the signal path, inductors can be used, as used in the Marchand ones, which SET and horn users in the USA rave about.
https://www.marchandelec.com/xm46-pllxo.html
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Ray P
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#260 Re: SLOB project

Post by Ray P »

Thanks, that's helpful.

I've got hold of the TubeCAD journal filter calculator software which give options with inductors and/or resistors. Lots to learn!

I'm sure I can get this arranged for a lot less than those Marchand crossovers!
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Ray P
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#261 Re: SLOB project

Post by Ray P »

Anyway, one step at a time so the first thing will be to build one bandwidth limited MoFo amp and try/measure with a speaker on a baffle - if that shows promise I can put the effort into the bass section and integrating them.
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Ray P
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#262 Re: SLOB project

Post by Ray P »

So after much mulling, here's a block diagram of the 'architecture' I've settled on for the SLOB project amplification;

Open Baffle Amp Block Diagram.jpg

I decided to build the Chip Amps as 'stock' - not building in bandwidth limiting means it's a more flexible amplifier - and by including the lo-pass filter in the MoFo amp chassis means it's the only element dedicated to the SLOB build. I can experiment with the lo-pass filter, maybe using MiniDSP to start with, and then convert that to a passive/active filter as appropriate. Following the lo-pass filter I've added a line buffer to drive the chip amp and I'll use some of the BUF-03 devices I used in this project;

http://www.audio-talk.co.uk/phpBB3/view ... =11&t=7788

For the Chip Amp volume control I'll use an Academy Audio Muses module that I have available. Master volume control will be via HQ Player.

Any observations?
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chris661
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#263 Re: SLOB project

Post by chris661 »

Looks pretty sensible to me, Ray. Having a separate volume control on the LF driver will be useful for getting things dialled in.

Interested to see how this progresses.

All the best,
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Ray P
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#264 Re: SLOB project

Post by Ray P »

I'll be grateful for any comments on this possibility, assuming Mark still has them?
Ray P wrote: Mon Jun 07, 2021 9:08 am
IslandPink wrote: Wed Nov 12, 2014 7:42 pm For sale, pair of these. Almost new, lightly used, run-in for 20-30 hrs with eg.25Hz and used for experiments on OB .
http://www.eminence.com/pdf/DeltaliteII_2515.pdf
Still available Mark?

I'm wondering if they might do a job in the Pass SLOB project I'm planning?
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IslandPink
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#265 Re: SLOB project

Post by IslandPink »

Yes, they could work in this application. The drivers JC Morrison and Nelson Pass recommended were in the same Qts range, i think. Have you got the Nelson Pass article to check ?
I never came across a method to simulate the performance though. Hornresp gave very suspect-looking results, I got the impression that the software wasn't valid with such a short 'horn' . I wasn't sure if any of the 'box' programs could work, either !
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Ray P
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#266 Re: SLOB project

Post by Ray P »

Thanks Mark. These are the units Nelson Pass used;

https://www.eminence.com/pdf/Definimax_4015ULF_8.pdf
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IslandPink
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#267 Re: SLOB project

Post by IslandPink »

Thanks.
The Deltalite's are about the same Fs and Qts ( a little bit higher, but same approx as Supravox 285GMF ) .
The Definimax has a larger cone mass, less output higher up. It has a higher Qms and hence lower Rms.
I don't know if this helps ? :)
One would have thought that suitability for application and acoustic loading would be linked mostly to Fs and Qts ..?
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Ray P
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#268 Re: SLOB project

Post by Ray P »

Thanks Mark.

I plan to cutover to the full-range drive unit at about 150Hz so the extended range of the Deltalite isn't a factor, though it does offer other alternatives, such as compression driver/horn crossed over a bit higher.

Hmmm, stuff to ponder.
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Ray P
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#269 Re: SLOB project

Post by Ray P »

Today I completed the assembly of the Class D amp I will use for the bass drive units in this SLOB project. It all went together fine, including some pretty fiddly smd soldering, and worked straight out of the blocks. The only downside was the noise level from the SMPS I was using to power it so I'm going to have to find an alternative (or experiment with disconnecting the fan - it's rated at 800W 48V so is never going to be called on to deliver that).

Image

Need to find a box to put it in too.
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Ray P
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#270 Re: SLOB project

Post by Ray P »

I returned from Owston today with a set of CNC'ed panels to build the base section of the SLOB project so I hope to be able to resume this project soon. Pictures to follow.

A big thank you goes to Toppsy for getting the ply and cutting done at his usual supplier on my behald - I really appreciate you putting yourself to the trouble involved in helping me out Colin, cheers!
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