Mark Audio CHR-70 Application Thread - Page 17 - diyAudio
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Old 29th April 2009, 03:52 PM   #161
tresch is offline tresch  United States
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Quote:
The FR graph looks a little better than the CHR-70 but that seems counter intuitive.
the Alpair10 is also four times the price of the CHR-70, so maybe that's what the extra 75 bucks per driver gets you

Hopefully I'll have something to report here pretty soon, subjectively, as it were. I'm hoping to start playing with measurement, but that's going to take a bit more time to get set up just right
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Old 3rd May 2009, 06:41 PM   #162
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I finally have pictures of the dual-chamber base reflex enclosure I built for my CHR-70's.

This picture shows the speaker as built. I've not applied a finished, and I'm consider putting a quarter-inch overlay around the driver to get it flush. The driver is offset on the baffle because of the port running up the one side, and you can see the slot ports on the side. They are built mirrored.
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Old 3rd May 2009, 07:03 PM   #163
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This picture is of the inside of my dual-chamber bass reflex enclosure, from the back.

In the design, I decided to use a slot port that was the same width as the enclosures depth and then use the port between the chambers as the separator for the chambers. This maximized the volume and minimized the number of walls.

The driver opening is visible through the far chamber. Half-inch material was used throughout. Because of some errors on my part, I had to use MDF for the port walls. All ports have the same effective length (slot port effective length is longer than actual length by half the height due to end being next to wall.) The height of the ports is 3/4". I used a couple of scraps of wood to set the spacing. The center port does wrap on both ends, again minimizing the walls. The driver chamber is twice the volume of the other. Besides the obvious stuffing, I glued some foam behind the driver, and I'm thinking of adding a little acousta-stuff in the driver chamber.

Overall, the design sounds very good. It can be pushed quite loud without distortion and it has good bass extension. Tuning design freq was ~48Hz and I believe the F3 somewhere below that.

I will publish a box drawing when I can get to it. Feel free to ask questions.

- John
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Old 3rd May 2009, 07:06 PM   #164
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^Niiiiiiice! Have you heard it yet and can comment on the sound? What are you going to finish it with?

I finished working on my set yesterday morning. If you guys remember, I was working on mine for a friend as a wedding gift. The entire set consisted of the Lotus BVR fronts, BR center, and BR surrounds all working with a sub. I had heard the BVR's since I tried them before I painted and finished them but I hadn't heard the others till yesterday morning when I finished everything.

I was kinda in a time crunch to finish everything by yesterday afternoon because that's when he and I were going to move it into his house. I woke up at 8 and did the ports, terminal cups, the rest of the soldering on the drivers and mounted everything. Before he came over I tested the small bookshelf BR surround speakers on my sonic impact amp and I really enjoyed them. I tuned them to 50hz so they don't have the bottom end presence of the Lotus BVR's but they sound delightful. Coupled with a sub they would do fine as mains.

We moved everything into his new place and set up his TV and everything. It basically took us all day. Flawed drawings on the TV stand instructions were to blame....FTL. But we got it done and I was able to hear everything. The whole system works very well together. I did some listening on music on my own and it was great. The real show stopper was when we threw in Irong Man on blue ray. Stuff sounded fantastic. In particular, I remember the sound of someone crumpling paper in the movie that sounded just like my friends wife crumpling packing paper about 20 minutes before in that room.

We have to mess with room placement some but I think I've found that the best way to place them is with the side drivers facing in. It really brings up the bass response on them. They sound a little deficient when the drivers are facing out. We weren't able to stick the sub in the corner because we didn't have a long LFE cable. I was just using an RCA. The sub needs some help from the corner on movie action but for normal use it's just amazing. I didn't get pictures of the whole set yet because he doesn't even have a couch in the room. I'll hopefully get some of the whole set in it's home.
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Old 5th May 2009, 12:11 AM   #165
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Quote:
Originally posted by italynstylion
^Niiiiiiice! Have you heard it yet and can comment on the sound? What are you going to finish it with?
I've had them playing for time. I had originally reported good bass extension with a muddled midbass. I hypothesized that being new was the issue and it was. I now have an NAD CD player as my primary audio source and I have to say that the detail from a better source is very revealing. The details on the jazz I'm listening to are fantastic. The piano is very accurate, the reeds are warm, and the percussion is sharp. And now I've sure I need more stuffing in upper chamber. Imaging has also improved from my initial report and listen. I'll pull out some of classical later. It's not something I listen to very often so if it doesn't resolve that well I won't be disappointed.

I highly recommend this style enclosure for anyone who's going without a sub. There is plenty of output down to ~45Hz. Don't let the tall thin shape dissuade you. I purposefully located the driver high in the cabinet to fit my desk and put them at ear level. They could easily be made shorter. If an EQ is to be used, this enclosure handles excursion better than a single BR.

For $70+wood, they're a great bargain. If I were to build them again, it'd be with 3/4" material for the front and back. And given the 4 small screws, I'd include an internal driver brace. And I just might. I also want to build a sealed enclosure and see what kind of bass they produce. A friend has asked for a very small HT set-up and I believe sealed would be the ticket for surrounds. Over all, I don't think I'm going to apply a finish to these enclosures. Too many other things to try.

Quote:
Originally posted by italynstylion
I finished working on my set yesterday morning. ...
... The real show stopper was when we threw in Iron Man on blue ray. Stuff sounded fantastic. In particular, I remember the sound of someone crumpling paper in the movie that sounded just like my friends wife crumpling packing paper about 20 minutes before in that room.
You'll have to get back to listen in 3 weeks. Once the CHR has some time on them, they sound great. Besides I want to hear the report on the BVRs. You're the first to build a set and they're not even for you.
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Old 5th May 2009, 12:24 AM   #166
MJK is offline MJK  United States
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Feel free to ask questions.
John,

How did you decide on the sizes of the two chambers and the lengths of the various ports? Did you use a specific theory or reference, some simulations to iterate the design, or just an intuitive feel for what would work well.

I like the idea, the speaker looks really nice.
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Old 5th May 2009, 02:44 AM   #167
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Quote:
Originally posted by MJK


John,

How did you decide on the sizes of the two chambers and the lengths of the various ports? Did you use a specific theory or reference, some simulations to iterate the design, or just an intuitive feel for what would work well.

I like the idea, the speaker looks really nice.
There had been a couple of enclosures built by some PE Tech-Talk regulars (Wolf's 3CR-Ti and W3-517S1-DCR, and Roman's Bandit). In Roman's write-up, he references the DIY-Subwoofer article about creating a 2:1 volume ratio and how the ports are determined.

The total volume and port size was determined by Unibox. The volume is determined in the vented alignment section with the number of ports set as 2. Looking at the response model, I chose 8.1L as my volume with no fill and tuning of 50Hz. This would allow for a mild ripple and I could tune that down with stuffing. The resulting port length is used for all 3 ports. The area of the port was chosen to be adequate for the driver at ~xmax. I also let the box dimensions drive this somewhat since I want to use the crossover port as the chamber separation too. The port is 4"x3/4" (3 sq in), and the internal depth is 4". In designing the box, I created a spreadsheet to develop the dimensions as I was iterating on several factors from Unibox and my space/location limitations. One issue with round ports was finding a way to put the ends into "space" in the chambers. This configuration does away with that problem entirely.

Some more listening impressions: I dug out a couple of Stereophile Test CDs and listened to some classical. The stage did suffer a little with the complex music but that could have been my listening environment. The instruments had no issues with resolution or identification. I put the warble tones one and the 80Hz and 63Hz tones were slightly louder indicating my ripple was greater than expected (and confirmed my thought of more acousta-stuff was needed.) The 50Hz was easily on par with 125Hz and the 41Hz was lower, confirming my statements earlier of the F3 in the mid-40s. Right now I'm listening to the Tears for Fears "Songs from the Big Chair" UltraDisc II from Mobile Fidelity. These speakers continue to amaze. It makes me want to keep upgrading. I may have to pull out my PS Audio DAC. Everything I try has rewarded me with obviously better sound. Where will it stop? I don't understand how something so inexpensive could be so good. I understand that my equipment is only mid-fi but it's still more investment than 90% of the people would do. Yet these CHR's are saying they're not the weak link in this chain.

John
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Old 13th May 2009, 05:08 AM   #168
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I've been holding out on you guys and for that I'm sorry. I've just been really busy lately with stuff.

I finished my friends system with the first normal design of the Lotus BVR's. His sound great and he is in love with the entire system. I'm sure the giant PVC subwoofer enclosure helps too. The center channel is the only place where I strayed from the advice given to me. I have two drivers and the port on the same face. For what the center is used for, movies and sports TV, it's fantastic and I have no regrets. The surround speakers are quite good on their own too. Not as much bottom end as the BVR's but they hold their own. The picture I have of them looks like the cone has something on it but it's just the odd flash reflection.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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All together...(he just moved in and doesn't have furniture yet)
Click the image to open in full size.



I also finished my own personal pair with the modified top part. They are exquisite. I lined two walls with felt, the rear wall and the wall that the side driver backs up against. The bass response is really quite breathtaking. They play hard and dead flat all the way down to 45ish and then taper off. The top end is fantastic as well. Best $100 on drivers I've ever spent. My 10 watt sonic impact amp is plenty of power for them as well. I find that facing the two drivers on the sides of the enclosures towards each other drastically improves bass response in my room. I'm not really sure why. Pictures are not where I listen to the speakers; I just wanted a decent picture.

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Old 13th May 2009, 05:38 AM   #169
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Beautiful. Expect to see those posted with the Lotus BVR on Frugal-Horn, and they deserve to be.
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Old 13th May 2009, 06:03 AM   #170
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Default italynstylion

Love the designs from italynstylion.

Could you contact us by sending a private message through diyaudio forums as we would like to get some information on how you designed the cabinets.

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