Group Delay questions....... (1 Viewer)

[Chris Carswell]

When does it become noticeable or a concern? 10m/s, 15m/s, 20m/s??? I wanted to know while I'm still in the design phase. I wasn't concerned at all when I designed my vented Tempest b/c it was strictly for HT. Group delay was ~ 21m/s at low Hz which is why I feel it is a little slow for fast music tracks.
My current project is for mains so I will need to pay a little more attention on these. Specially since I would like to play the mains as "Large" with no sub for music. This is why I wanted to go ported with the mains. To get the extra low end since they will be playing solo. They are 7" drivers so I guess I can go sealed if need be but I would really like to have that extra bit of the low end. Thanks all

 

[Chris Carswell]

No one?
No ideas or thoughts?
Ok, what about guesses? Anyone want to guess ?

 

[Mark_E_Smith]

IMHO I think phase is more important, I think all drivers have some delay and it gets worse with the alignment chosen.

 

[Chris Carswell]

Hey Mark - how's it going? Long time no hear. I wish I could comment on your center ch. thread but I wondered the same thing.
"drivers have some delay and it gets worse with the alignment chosen"
That's exactly why I wanted to know what was an acceptable level or where I would start to run in to problems. I still have not nailed the final details of my alignment. The xovers are already done & they phase in/out very nicely.
BTY, How are those mains coming? I just started on mine

 

[Mark_E_Smith]

If you model a PR, Vented, IB and a sealed you could see the difference. What I have modeled seems the PRs and vented have the potential to have the worst GD. With sealed and IBs have the best. No mains yet. What mains did you decide on building? I think I am going to rebuild the center box for the ports to fire forward and measure them and compare. I am going on the HT cruise and will be driving to Miami at the end of Oct, how about a rendezvous? I would like to met you.

 

[Chris Carswell]

This group delay question pertains to my mains actually. I'm done with my sub although I will be putting in larger ports w/ homemade flared ends.
I'm not sure what Hz to tune it to since it effects the delay in different ways. I will probably go the safe route & build it sealed & check the bass response. Then if it is not to my liking I'll get out the jig saw/router & get to work. I went with the SA071's but not the Morel tweeter we were working on. I'll shoot you an email with more details. I'm working on my DIY web site as well. Should be lots of fun. What do you think about a TMM or MTM for the mains? Center is MTM, surrounds are TM.
What are you doing the 26th? I'm trying to have everything done & go to the ATL 2002 DIY meeting but not sure if I can swing it. If not LMK when you will be in FL so we can meet up .
-Cman

 

[Mark_E_Smith]

For the mains I would go MMT. If you plot the GD you may find it only gets out of hand below 60 Hz If so then port them and tune them to 60 Hz or so, I will await your e-mail. We will be driving from central Texas Wed the 30th and will arrive in Fl panhandle 31st. I will PM you will the details.

 

[Chris Carswell]

Do you think porting them to ~60 Hz is a little high? I get about a 7.8 db peak & 65Hz then falls after that with a F3 of 47Hz. I'll try to put up some graphs. I'll email you when I get home later today.

 

[Mark_E_Smith]

The tuning was a WAG, I was using as an example. If you are using a sub you really dont need to go that low.

 

[Chris Carswell]

Got ya
Send me your email again. If I use the forum's email I can't attach files.