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Old 25th July 2009, 06:42 PM   #221
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Sorry, I apparently directed my question to the wrong person. I should have asked HareBrained.

HairBrained, re my post above, I'd really like to better understand the pros and cons of your design vs a standard BR box. BTW, does your double chamber help with the small hump in LF response due the Hi Q of the CHR-70 or does that stay the same?

Thanks much,
Steve
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Old 26th July 2009, 01:43 AM   #222
_henry_ is offline _henry_  Australia
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It is 5' tall.
that is big
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Old 27th July 2009, 03:03 AM   #223
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Quote:
Originally posted by audiosteve
Voldemar1,

I have a few CHR-70's. I have not yet decided on the enclosure for them. Thank you for sharing your design. But can you tell me why should I want build this enclosure instead of a standard BR? A standard ported design will give me an F3 of about 37 Hz in a smaller less complicated box. What is the benefit of building your box? I am not asking this to be disrespectful of your design. I just want to understand how the benefits of this design justify the additional cost, complexity and size. In short, is it worth the effort and why?

Thanks,
Steve

Quote:
Originally posted by audiosteve
Sorry, I apparently directed my question to the wrong person. I should have asked HareBrained.

HairBrained, re my post above, I'd really like to better understand the pros and cons of your design vs a standard BR box. BTW, does your double chamber help with the small hump in LF response due the Hi Q of the CHR-70 or does that stay the same?

Thanks much,
Steve

As you mentioned, all credits goes to HairBrained. I just hoped his calculations are right and wanted him to review the plan before implementing it.
The reason why I chose this design is they are just 5Ē deep and intended to stay close to the wall. Thatís exactly what I need for my PC speakers.
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Old 29th July 2009, 12:00 AM   #224
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Sorry for the delay in seeing the posts. I'm in the process of relocating to Portland for a contract and have been otherwise occupied.

Audiosteve, I have to question being able to get a lower F3 from the same driver in a smaller box. You may have an error somewhere. The F3 should be the same for a dual chamber as a single chamber for the same net volume. The benefit of a dual chamber reflex is excursion control. Any full range driver (that's run full range) will have excursion/power handling issues because of it trying to put out bass that it's not really capable of producing. Given the same net volume and power input, the DCR will have better excursion control then the BR.

I have my speakers against a wall, and I had to add more stuffing to the driver chamber to control the bump. If used further from the wall, I doubt it would be necessary. My modeling (Unibox) showed only 1db of ripple in the 8.1L box. And since I was able to tune it with the stuffing, you should see similar results.

Voldemar1, nice job on the sketch-up drawing. I thought you were interested in lowering the driver but it looks like you moved it up. Either way, shouldn't be a problem. That is one nice thing about the design, it can be tailored to suit the need. Please post your honest impressions of the design when you've had a chance to listen. I found it took only about 20 hours of playback before the output started to crystallize.
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Old 29th July 2009, 12:15 AM   #225
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Originally posted by HareBrained

....
Voldemar1, nice job on the sketch-up drawing. I thought you were interested in lowering the driver but it looks like you moved it up. Either way, shouldn't be a problem. That is one nice thing about the design, it can be tailored to suit the need. Please post your honest impressions of the design when you've had a chance to listen. I found it took only about 20 hours of playback before the output started to crystallize.
Thank you,
I was unsure about driver position. Aesthetically I want driver to be on the same distances from the left and right sides of the front baffle. But at the end I decided to put it in the middle of the upper chamber. Talking about distance from the top, I think Iíll lower it a little bit, to put it closer to the ear level.
Right now I have small pile of plywood sitting in my garage. Taking to account Canadian Civic Holiday next Monday (which I usually spent outside the city) Iím not expecting any outcome in next couple of weeks.
So Iím going to fully enjoy building speakers first, and then will certainly post my impressions.


Vlad
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Old 29th July 2009, 01:32 AM   #226
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Thanks for your reply Harebrained.
So the primary benefit is in reducing excursion and not in lowering F3. That is a useful benefit for a smaller driver and would make it wothwhile. I have since done some googling and found out quite a bit more about the dual chamber reflex (DCR) design. I may try one.
Incidentally, in looking at your plans I saw that the box was 21.5" by 8.5" and assumed it was much larger than the design of the simple BR that WinISD showed. I did not realize that the box was only 4" deep. In fact, the optimized WinISD alignment is in about 17.5 liters. So there is no size advantage. But you can jam it down to about 12 liters and still get a decent response.
Thanks for turning me on this design type. I see there is now another option available to me that could be beneficial in some circumstances.

Steve
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Old 29th July 2009, 08:46 PM   #227
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Quote:
Originally posted by audiosteve
Thanks for your reply Harebrained.
So the primary benefit is in reducing excursion and not in lowering F3. That is a useful benefit for a smaller driver and would make it wothwhile. I have since done some googling and found out quite a bit more about the dual chamber reflex (DCR) design. I may try one.
Incidentally, in looking at your plans I saw that the box was 21.5" by 8.5" and assumed it was much larger than the design of the simple BR that WinISD showed. I did not realize that the box was only 4" deep. In fact, the optimized WinISD alignment is in about 17.5 liters. So there is no size advantage. But you can jam it down to about 12 liters and still get a decent response.
Thanks for turning me on this design type. I see there is now another option available to me that could be beneficial in some circumstances.

Steve
From my experience, you can jam it down to 8L and get very good response. My next project will be a FAST with the CHR. There are numerous woofers that would work well, it's really going to come down to how much I want to spend. But with me moving to Portland OR USA, it's all gonna have to wait.
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Old 29th July 2009, 09:01 PM   #228
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My next 'real' project will also be a FAST once the CHR-70's are done. The CHr-70's shouldn't take much time. I am sure you have seen the 'Boominator' thread. My plan is to make the "Audinator', an audiophile quality boombox that can be closed up to be fully protected for travel so I can have good sound in hotels when on the road. I already have all the parts and have started building the amp. It is using a 41Hz Amp-9, the group buy active filter boards, a pair of Jordan J6's, a pair of 3 1/2" Peerless woofers, a 24V 10A universal switching supply and a small DC/DC converter to power the crossover boards. I'm not trying to hijack the thread with this. Just mentioning the project because you had also mentioned doing a FAST. I started planning this quite a while ago and am now dismayed to see that I could probably get similar performance out of just a pair of Alpair 6's. But I wasn't aware of them when I started down this road. 'nuff said about that. Back to the real thread.
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Old 29th July 2009, 10:10 PM   #229
vaughn is offline vaughn  United States
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Originally posted by vaughn
well I know this is probably heresy but...

I just ordered two pairs of these and plan on using them in a cabinet with
a separate woofer. I don't know which woofer but I have had great experience with
the JBL LE14a. I don't know, maybe one of Dayton's aluminum cone RS series subs.

Anyway, I would like to use these open baffle for the top end. I am wondering if I am going to need two drivers if I am not asking it to do anything below 150hz? If I am going to need two drivers can I mount them at right angles like the previously mentioned designs, but on an open baffle? Would this create any problems?

Optionally I could use them in a bipole configuration?

I thought I would try this again, any thoughts on using this driver ob covering 150hz and up or so?
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Old 30th July 2009, 02:26 PM   #230
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I tried these little CHR-70 in an OB crossed at 200Hz and they didn't do too well. Seemed very sloppy and lost control around 7-10W. I tried crossing at 330Hz and they did behave better but they still didn't perform nearly as well as the same driver in a boxed varient. YMMV but I didn't like how they performed OB....
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