Hi, I'm just about to start building a pair of Pensil 7's, using a set of CHP70 1st generation drivers. Following the plans downloaded from Planet10's archive, I will be using 18mm birch plywood and a piece of 18mm solid walnut for the speaker baffle. And this is where the maths comes in to it.
The walnut is only 144mm wide (the plans state a 146.1mm wide baffle). Although this is a small difference in size it does effect the overall volume of the speaker. By using the plans dimensions I've calculated the internal volume of the 7's to be 38.45litres. After recalculating for the change in width, this becomes 37.93litres.
If I use the 144mm wide baffle and alter the internal depth, by adding 4mm, this brings the internal volume back to 38.45litres.
The question is, can these alteration be used and not effect the sonic presentation of the speakers?
Any advice welcome.
Mark
The walnut is only 144mm wide (the plans state a 146.1mm wide baffle). Although this is a small difference in size it does effect the overall volume of the speaker. By using the plans dimensions I've calculated the internal volume of the 7's to be 38.45litres. After recalculating for the change in width, this becomes 37.93litres.
If I use the 144mm wide baffle and alter the internal depth, by adding 4mm, this brings the internal volume back to 38.45litres.
The question is, can these alteration be used and not effect the sonic presentation of the speakers?
Any advice welcome.
Mark
Hi Scott. The build is slow going. Time and money are an unfortunate factor. I've got the drivers and wood for the baffles. Just got to get the plywood for the rest of the cabinets and find the time to build.
I bought three CHP70's. Two for the Pensils and a third to design and build a centre speaker. The plans for the centre speaker are still in development but il draw them up and post them. Will be good to get some feedback on my design.
I bought three CHP70's. Two for the Pensils and a third to design and build a centre speaker. The plans for the centre speaker are still in development but il draw them up and post them. Will be good to get some feedback on my design.
Cool. I understand how slow things can go, just check out my thread on my build! Took FOREVER to get done but I really enjoy them daily.
For a center design, talk to Dave (Planet10). We did a custom Mar-Ken design for my 12's and it blends in with my SuperPensils pretty much perfectly and looks nice also.
Scott
For a center design, talk to Dave (Planet10). We did a custom Mar-Ken design for my 12's and it blends in with my SuperPensils pretty much perfectly and looks nice also.
Scott
Well I've eventually started the prep for the Pensil 7's build. Started running in the drivers. They are just in their boxes and wired up to an old stereo at the moment but are already sounding pretty good. Also designed and made a router jig and started work on the baffles.
I've also done some initial calculations for the centre speaker. Attached are the plans and dimensions. The design is for a sealed enclosure with an F-3 of 81hz.
A couple of questions about the design are:
As the baffle isn't very high (internal hight of only 109mm) will their be any problems having the driver so close to the wall?
Would I need to consider any form of BSC for the design?
Any feedback would be much appreciated.
Mark
I've also done some initial calculations for the centre speaker. Attached are the plans and dimensions. The design is for a sealed enclosure with an F-3 of 81hz.
A couple of questions about the design are:
As the baffle isn't very high (internal hight of only 109mm) will their be any problems having the driver so close to the wall?
Would I need to consider any form of BSC for the design?
Any feedback would be much appreciated.
Mark
Attachments
It’s been a while since my last post so I thought I’d give an update on the Pensil build. Finding time to dedicate to the build has been tricky but I think I’m nearly there.
This is the first speaker build I’ve done but me being me, I couldn’t just follow the plans, I had to tinker.
As you can see from the pictures I’ve used a piece of walnut on the baffle, where the driver sits. As the walnut width is a few millimetre smaller than the plans I re-calculated the speaker and vent dimensions to maintain the original volume.
Lesson 1: Check measurements. Check measurements. And check again.
As the eagle eyed reader has probably noticed, the cleats for fixing the back panel are flush with back of the cabinet. After much swearing and rechecking of measurements I had to accept I’d got it wrong and the only way to get around this without scrapping the wood was to trim the side panels and have the back panel fixed directly on, rather than set in. This now means I’ve got a bit of a job to make sure the seal is as airtight as I can make it.
One of the hardest things I’ve found with the build is cutting the plywood accurately. Trying to make millimetre accurate cuts with a circular saw is pretty difficult. And even when using hand saws, getting everything exact has taken some patience.
How sensitive is the Pensil design when it comes to measurements? Even re-measuring and re-calculating every time I cut and sand panels their are still slight differences between what I have and the plans.
Hoping to get the cabinets finished this month and then start designing and building the centre speaker. Final stages are to sand, paint and add the stuffing before fixing the drivers and start to test the speakers. The plan is to paint the main body of the cabinet white and wax the walnut. This should look fantastic once the natural paper CHP70’s are fitted.
I’ll post more pictures as I progress.
Mark
This is the first speaker build I’ve done but me being me, I couldn’t just follow the plans, I had to tinker.
As you can see from the pictures I’ve used a piece of walnut on the baffle, where the driver sits. As the walnut width is a few millimetre smaller than the plans I re-calculated the speaker and vent dimensions to maintain the original volume.
Lesson 1: Check measurements. Check measurements. And check again.
As the eagle eyed reader has probably noticed, the cleats for fixing the back panel are flush with back of the cabinet. After much swearing and rechecking of measurements I had to accept I’d got it wrong and the only way to get around this without scrapping the wood was to trim the side panels and have the back panel fixed directly on, rather than set in. This now means I’ve got a bit of a job to make sure the seal is as airtight as I can make it.
One of the hardest things I’ve found with the build is cutting the plywood accurately. Trying to make millimetre accurate cuts with a circular saw is pretty difficult. And even when using hand saws, getting everything exact has taken some patience.
How sensitive is the Pensil design when it comes to measurements? Even re-measuring and re-calculating every time I cut and sand panels their are still slight differences between what I have and the plans.
Hoping to get the cabinets finished this month and then start designing and building the centre speaker. Final stages are to sand, paint and add the stuffing before fixing the drivers and start to test the speakers. The plan is to paint the main body of the cabinet white and wax the walnut. This should look fantastic once the natural paper CHP70’s are fitted.
I’ll post more pictures as I progress.
Mark
Attachments
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