speedysteve

DIY Tannoy GRF's

118 posts in this topic

DEALER

I finally got around to put the order in for the 21mm Birch plywood (front panel 24mm).

I will be using my Tannoy Berkeley HPD 3828 15" drivers.

They are a copy of plans found on T'internet but to the same dims as Mr Coco's (which I've heard).

2479969770071997495S600x600Q85.jpg

Idea is to make the round front panel cut compatible for both 3828's and Golds.

My Coco kindly put their data into his horn calc prog:) and things came out very much the same as for his 15" Monitor Golds (see below).

HPD params

2069687690071997495S600x600Q85.jpg

2772748440071997495S600x600Q85.jpg

HPD response

2452228190071997495S600x600Q85.jpg

Monitor Golds params

2742499710071997495S600x600Q85.jpg

Monitor Golds response

2067589240071997495S600x600Q85.jpg

Apparently the comb filtering is normal. So green light on HPD's working on paper.

I'll post up some pics as we go...

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DEALER
:pop:
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Pretty much the same SPL response I was getting with scaling down the GRF for a 12".

Unfortunately haven't had the time to start mine yet. Keep us posted!

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DEALER

Coco-san said that the prog allows you to build up a sectioned horn (in this case 3 sections) adding them together. Not sure of the exact details though.

News flash form Coco-san on the calc done.

"I just simulated a straight exponential, which approximates the GRF flare. I did it as conical sections before, but lost the measurements when my laptop got rebuilt. It was a ball ache to calculate from the plans and didn't show much difference. But it doesn't matter, we're trying to do a comparison here, not a new design and the comparison shows negligible differences..."

The comparison was between my HPD's and Coco's MG's.

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DEALER

I'm looking forward to getting started on mine, where have you sourced the wood? Could you post the dimensions pic larger please, when I zoom in I cant quite make some of the dimensions out.

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DEALER

Yeah BD can do from home this evening.

Wood from Avon Plywood (Coco's recommendation).

They could have fulfilled the order immediately for around £360 with 21mm / 24mm Birch plywood but the 21mm stuff would have been a grade that has knots and dings repaired by letting new wood in. Fine if you are going to paint or veneer but I want nartual / varnished Birch. So have asked them to price and source the stuff that is higher grade on one surface. Will cost around £100 more I reckon - also get them to cut the front hole - internal stuff I can do with a slip of the jigsaw or router:)

You would need a slightly smaller hole for your round HPD drivers than my odd shaped gold fronted ones. I have that dimension on the plans from T'internet.

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DEALER

Once a pair are done it would be interested to have a pair of Berkeleys and a pair of Grf's with HPD drivers side by side. :geek:

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DEALER

Another wammer kindly sent me this today too.

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Mind you, if you intend to use the plans please re-check the driver/magnet dimensions and cutouts. The thing is, the plans and cutouts are based on my 3828 drivers, which have ceramic magnets as opposed to older (reds, golds, HPDs,...) which, as you know, have AlNiCo magnets (=narrower and deeper).

And please excuse my crappy translations...

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DEALER

The top angle would be exactly the same as the bottom showed on the pdf. Anyone have the dimensions of HPDs as shown in my speakers above? I dont really want to take them out un-necessarily.

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