Bryston AC1 center channel poor off axis response.

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Chewbacca 319

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Bryston AC1 center channel poor off axis response.
« on: 20 Feb 2023, 03:01 pm »
Good day all. I'm creating this post in the hopes of getting to the bottom of a really unfortunate issue that I am having.

Around 2 years ago now I purchased a bryston AC1 center channel through an authorized dealer in Edmonton. When I first purchased the center I had it in a much smaller listening room where the only listening position was dead on. No issues.

I have since moved into a new place and have a proper listening room where there are multiple listening positions. This is where the issue has come. Dialogue out of the center is extremely poor anytime I go off axis from the couch directly in front of it. I have two chairs on either side of my main couch which isn't much more than 40° off axis from the center. At these listening points the overall clarity and eligibility of any audio from the center is greatly reduced. You can even tell by walking across the room that the Signal from the center sounds worse the farther you go off axis. When using test tones there is even a distinct difference in how a static noise sounds compared to my A2 towers which use the same compliment of drivers.

I have ruled out this being a source or amp issue. I have tried completely different amps/processors and multiple types of sources. All the same issue. When running ARC room correction through my current AVM 60 it shows that the center has a substantial dip around the 5-6khz range and a roll off in the higher frequencies. Having ARC correct this helps but still isn't great.

I have contacted bryston support. Aside from shipping them the center (nowhere near a dealer and shipping from the Northwest Territories is going to cost an arm and a leg) I asked for a schematic of the crossover, maybe something was faulty from the factory or maybe something was wired out of phase by accident.

After examining the crossover and cross referencing with the schematic nothing looks the be wired wrong so I'm stumped. My next step is to either swap out the drivers from one of the towers and put it in the center or swap the center and the towers positions and retest.

Interestingly I decided to remove the metal grills that cover the tweeters and upon first impressions off axis performance appears to improve which is odd considering ive read that they are in place to improve off axis listening.

Perhaps what I'm experiencing is true example of comb filtering? Or maybe I just have a lemon from the factory. I'm at the point where I'm looking into purchasing a new center because of this issue. If there is in fact no issue and this is just how the center is supposed to sound I'm honestly disappointed. Hoping someone here has some insight on what I should do.

James Tanner

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Re: Bryston AC1 center channel poor off axis response.
« Reply #1 on: 20 Feb 2023, 05:44 pm »
I think we should get the speaker back to have a look

james

planet10

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Re: Bryston AC1 center channel poor off axis response.
« Reply #2 on: 20 Feb 2023, 05:52 pm »


This is a sideways MTM. They come from the marketing department not the engineering department.

Tools has shown this.

Try rotating the centre such that the MTM is vertical and see what difference that makes.

dave

whydontumarryit

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Re: Bryston AC1 center channel poor off axis response.
« Reply #3 on: 20 Feb 2023, 10:23 pm »
You can connect it out of phase and give it a listen.

Chewbacca 319

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Re: Bryston AC1 center channel poor off axis response.
« Reply #4 on: 20 Feb 2023, 11:20 pm »
Hey James.

I do agree with you but that option isn't realistically viable. when I initially called Mike at support he suggested the same thing about shipping it to you guys. I didn't get quotes but I already know that shipping from Yellowknife NT to your facility in Ontario would cost an arm and a leg. To heavy and large to ship Canada Post, most likely costing minimum $300 each way. Unless I were to box the center up and take it with me on a road trip down I can't justify the money spent.

Once I have a free moment I plan on trying both trouble shooting methods I listed at the end of my last post (transplant drivers from one of my towers and also try moving one of my towers to the center speakers position and seeing if it still sounds off).

James you wouldn't happen to know off hand what point the midrange frequencies crossover to the tweeters do you? The overall output of my tweeters sound low in comparison to my A2 towers for example. That lead me down the rabbit hole of possibly a defective crossover but from what I can tell it's all functioning as normal. One thing I do plan on doing is adding more acoustic foam to my center. I was surprised at how little was in the center, the whole main cavity of it was empty except for two small pieces on either side where the bass drivers were.

For whatever reason audio circle isn't letting me post pictures but for context the second ever post you shared in bryston systems is a picture of my system. The one with all Boston cherry speakers with a huge wooden AV unit.

Another thing I plan on testing is using my set of mini A's as a makeshift center and seeing how that sounds. I'll run them in parallel with each other which will also provide an MTM configuration.

Thanks for the reply though.

James Tanner

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Re: Bryston AC1 center channel poor off axis response.
« Reply #5 on: 21 Feb 2023, 12:03 am »
OK let me know how that goes - I will ask engineering to send me the anechoic graphs on the dispersion of the TC-1 Center

james

James Tanner

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Re: Bryston AC1 center channel poor off axis response.
« Reply #6 on: 21 Feb 2023, 12:36 am »
Hi Chew - he is a shot of my TC-1 Center - I am watching the hockey game and the measurement is at  10 feet -  first graph is on axis - second graph is 40 degrees off axis.
How do they compare to yours?




james

Chewbacca 319

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Re: Bryston AC1 center channel poor off axis response.
« Reply #7 on: 21 Feb 2023, 02:00 am »
Hey James.

The overall response of your graphs appear very linear with not much difference between listening points. When viewing the graphs in Anthems ARC calibration software my readings are all over the place. Now this is to be somewhat expected since room acoustics come into play however according to my readings this is what I found.

When comparing to the target curve there is a substantial dip from the 1-2khz range , with a big pump in 5-10khz range and a very deep dropoff around 12khz.

When putting my ear up to the tweeters in my center the overall output of them seems very reduced. When compared to my A2 towers there is a definite tonal change when my ear goes from the midrange to the tweeters. In the center it almost seems like the DB output is very toned down which is odd.

This reduced high frequency output falls in line with a lot of the issues I've been hearing. I think it would be very coincidental that both tweeters would have a flaw that causes reduced output so I'm rather stumped. When comparing the ARC readings on and off axis the high frequencies fall off faster but overall follow more or less the same curve.

When comparing the ARC graphs of my towers to my center its clear as day something is wrong. Both towers before room correction are quite flat in their response. Both towers have a bump of about 5db around the 18khz range but besides that rather flat, both towers show similar readings. Both of my mini A rears are very similar with good high frequency response. Again audio circle isn't allowing me to post images so I can't show the graphs. This deep cutoff at 12khz on the AC1 seems to be the problem. I'm going to swap out the tweeters from one of my towers and sees If it makes a difference

James Tanner

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Re: Bryston AC1 center channel poor off axis response.
« Reply #8 on: 21 Feb 2023, 12:16 pm »
Can you send me your graphs in an email - jamestanner@bryston.com
Are you measuring at the listening location?

james

James Tanner

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Re: Bryston AC1 center channel poor off axis response.
« Reply #9 on: 21 Feb 2023, 03:53 pm »
We are testing an AC-1 in our anechoic chamber today.

james

Chewbacca 319

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Re: Bryston AC1 center channel poor off axis response.
« Reply #10 on: 21 Feb 2023, 05:07 pm »
Hey James,

Just sent an email.

Today I am going to be swapping out the tweeters from one of my towers into the center and seeing if it improves at all. If it still sounds the same it may be indeed a defective crossover. I will update to let you know.

whydontumarryit

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Re: Bryston AC1 center channel poor off axis response.
« Reply #11 on: 23 Feb 2023, 08:37 am »
Hey James,

Just sent an email.

Today I am going to be swapping out the tweeters from one of my towers into the center and seeing if it improves at all. If it still sounds the same it may be indeed a defective crossover. I will update to let you know.

If things don't work out there's always this:
https://www.audioholics.com/bookshelf-speaker-reviews/ccb-8-bookshelf

James Tanner

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Re: Bryston AC1 center channel poor off axis response.
« Reply #12 on: 23 Feb 2023, 01:03 pm »
If things don't work out there's always this:
https://www.audioholics.com/bookshelf-speaker-reviews/ccb-8-bookshelf

Why would you post this on a Bryston forum?

james

whydontumarryit

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Re: Bryston AC1 center channel poor off axis response.
« Reply #13 on: 23 Feb 2023, 05:24 pm »
Why would you post this on a Bryston forum?

james
Mostly because it looks as if the OP is trying to cheapen up on his center channel selection and made the mistake of opting for a 2 way configuration and then complain about horizontal directivity, lobing, comb filtering, or whatever it is that a 2 way cannot do properly as a center channel.

I could have just as easily suggested an Infinity R263 ($200)or the Axiom VP160 or the AC-1 mini at 4 times the price. The point is he needs a 3 way or that coax point source, no lobing type to solve his problem.

Having a defective AC-1 micro seems highly unlikely.

If someone recommends Kimber Kable in this forum instead of Bryston's cables is that a problem.

James Tanner

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Re: Bryston AC1 center channel poor off axis response.
« Reply #14 on: 23 Feb 2023, 06:19 pm »
Turns out it was defective in that both tweeters were bad - 2 new ones are on the way. 
When you design a horizontal center channel you design it knowing that the drivers and the polar response will be different than in a vertical position.

james

Chewbacca 319

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Re: Bryston AC1 center channel poor off axis response.
« Reply #15 on: 26 Feb 2023, 10:13 pm »
Mostly because it looks as if the OP is trying to cheapen up on his center channel selection and made the mistake of opting for a 2 way configuration and then complain about horizontal directivity, lobing, comb filtering, or whatever it is that a 2 way cannot do properly as a center channel.

I could have just as easily suggested an Infinity R263 ($200)or the Axiom VP160 or the AC-1 mini at 4 times the price. The point is he needs a 3 way or that coax point source, no lobing type to solve his problem.

Having a defective AC-1 micro seems highly unlikely.

If someone recommends Kimber Kable in this forum instead of Bryston's cables is that a problem.

I think you misunderstood my posts when another member posted a picture of the AC1 micro. I have the full fat AC1, if you would have read my posts you would have understood that, 6 driver 3 way center channel.

I'm not trying to cheapen out and replace my center. In the end I transplanted a set of tweeters from my one A2 tower into the AC1, it was a night and day difference. According to my ARC room EQ graphs my tweeters were pretty much dead after 12khz. This is very odd because usually when tweeters blow they blow open, resulting in a completely dead driver.

I did dismantle both tweeters and there appeared to be lopsided and uneven dispersion of ferrofluid, did not see any signs of breaks or overheating on the diaphragms voice coil but it was cause for concern. I also tested the resistance of both faulty tweeters and they were reading a lower resistance than my control tweeters from my A2 tower.

I have never heard my center sound as good as they did with the working tweeters in them. My use case for my system is about 70% music 30% movies/games so it's not as if I use my center that much to begin with. I've never had a movie playing over 90-95 db so I don't think this was fault on my part overpowering the center, most likely, in my opinion, just a lemon from the factory, mike at service agreed.

I really appreciate James reaching out to me personally, it's such a unique experience to get direct help from a company owner for a product and he is a stand up guy. As James said I am currently waiting for new tweeters in the mail. One thing I did change with my AC1 center however is added more acoustic foam to the cabinet. Besides two small pieces on either side near the bass woofers the entire middle cavity of the cabinet was empty, probably won't make a huge difference but I have extra lying around from a previous project so I thought why not.

Overall I'm very pleased to finally get to the bottom of this. Thanks everyone for your input and advice :)

gbaby

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Re: Bryston AC1 center channel poor off axis response.
« Reply #16 on: 27 Feb 2023, 12:53 am »
Good post.

Stefan_DR3

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Re: Bryston AC1 center channel poor off axis response.
« Reply #17 on: 28 Feb 2023, 07:26 am »
We are testing an AC-1 in our anechoic chamber today.

james

Hi James, just curious how did that testing go?

Stefan_DR3

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Re: Bryston AC1 center channel poor off axis response.
« Reply #18 on: 28 Feb 2023, 07:29 am »
it was a night and day difference. According to my ARC room EQ graphs my tweeters were pretty much dead after 12khz. This is very odd because usually when tweeters blow they blow open, resulting in a completely dead driver.

In reality it was probably worse than that off-axis.  One thing to keep in mind is ARC shows you the average of the 5 (or more) measurement positions that you take in the room.  At least one of those positions would have been in the sweet spot.

James Tanner

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Re: Bryston AC1 center channel poor off axis response.
« Reply #19 on: 28 Feb 2023, 12:45 pm »
Hi James, just curious how did that testing go?

The graphs looked fine and I tested mine at home as well and they looked fine.
When you have a multi-driver speaker the measurements will be a balance between the horizontal and vertical measurements. With Center channels that balance is towards the horizontal positioning vs the vertical positioning.

best
james