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08-06-2018 Post does not mapped to Knowledge Tree

Chicago, IL
Posts 174
Joined on 06-12-2009

Post #: 1
Post ID: 25029
Reply to: 25029
Thoughts on midbass horn approach
I have identified a direction for my next speaker system. Whether it is a good one or not is a different topic -- I think it's a good one because I've lived with my current horn system for 10 years and have since developed an understanding of it's strengths and weaknesses and in my view the set of requirements. I think they are necessary to set basics. Again, those are the basics that I came up with, not recommended by someone. In my room and listening habits seem very reasonable.  Some may not agree but this would be another discussion. Back to my point: My requirements would require a new system and a lot of experimentation and tuning capabilities built into the new system.  First off, the midrange horn shall be Western Electric 13a with a 14 foot long horn, based on the 555 driver. 
I would like to ask your thoughts on the way I am approaching the midbass channel. Is this a reasonable way to think about design of midbass:
1.To match the footprint of the 13a horn, the midbass horn will be folded, sit on the floor, underneath 13a horn. This will elevate the 13a horn to correct ear level.
2.To have time alignment with 13a horn the midbass horn path must be about 14 feet.
3.To let midbass horn cover below 120hz.
4.To use field coil driver and to adjust the Qt if necessary, to fine tune midbass sound AFTER installation.
5.To let this midbass channel play as low as it can (while still sounding good). Below that use sealed subs if needed.

Using the list I made is possible to arrive at good performing midbass within constraints of system based on a large midrange horn that plays down to 120hz? So as to cover most of sound below 120hz.I am not sure about #4. Is this a useful thing in midbass horn?
Thank you,Gera

08-07-2018 Post does not mapped to Knowledge Tree
Romy the Cat

Boston, MA
Posts 9,967
Joined on 05-27-2004

Post #: 2
Post ID: 25031
Reply to: 25029
Gera, if you would like to incorporate the Western Electric 13a with 555 then you need to make a decision how low you will drive it. You chose the 120Hz but it might not be useable frequency, it might be much higher in order to get “better” sound or it might be even lower, depends how you room will response. To match the midbass horn below 120Hz you do not need to know where 13a will die, any midbass horn will shoot to there. The time-align the midbass horn and 13a will be not so hard but to alight it all with higher frequency channels will be very hard, if even possible. The ides or using field coil driver and to adjust the Qt at midbass is very bad idea, sorry. Audio people always fantasize to use the field coil to “adjust something” but in reality it is not how it works. Also, when you mention a midbass horn below 120Hz then it means nothing. When you name midbass you need to state what it is, means: rate, size, driver, throat, profile.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-08-2018 Post does not mapped to Knowledge Tree

Chicago, IL
Posts 174
Joined on 06-12-2009

Post #: 3
Post ID: 25034
Reply to: 25031
More explanation
Romy, thank you for your thoughts. First off, my further thought on the system and specifically the implementation of the high freq section: Yes, the time alignment would be a challenge but possible. This is the main compromise, in my view but the least objectionable compromise to use DSP delay on the high freq section. I'm not a fan of DSP and I say this because I know first hand of the drawbacks of inevitable compromise of sound quality. But out of all compromises, this one I decided to accept, as the least objectionable use of DSP, solely on the high freq section, and in the low bass section (subwoofer). To me, it is best to keep DSP away from midbass and midrange horn, and this configuration would make this possible, as the essential part of sound range would be without DSP.

Now about the midbass horn. I do not know the driver, throat, and profile. All I can say about this channel is my general idea, which is it can be 14 foot long folded horn and the size of the midbass box 32"x45"x40". This is the volume of space that will be "available". I do not plan to design it myself but have an expert do the design, recommend the driver, within those space constraints. Since you say any midbass horn will shoot above 120hz, the variable that is left is how low will it play. I'm not setting a goal freq of how low. This will be dictated by the volume and what the designer will propose as a good lower knee for the driver/horn combination based on space constraints and his design.

I do not have an expert designer but would be very thankful to anyone who can recommend someone competent.
So let's say this expert will tell me he can design something within those space constrains with such and such driver and it will be useable down to 50hz in the location of my room. I will be conservative in my expectations but if I get only 60hz, that is no issue at all.The low bass section will be on DSP and will be adjusted to meet the midbass.What do you think of this approach?
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