Usher Kit Mod

[hhdinc]

I want to use the drivers and crossover for the Usher 701 kit - but I want to alter the cabinet dimensions (keeping the same internal volume) and I need to relocate the port to the front. Is this nuts? Will it compromise the design too much? The goal is to make a short floor-stander that's about 8" wide and no more than 30" high that can be located within 6" of the back wall.

[Chris Roemer]

> I want to use the drivers and crossover for
> the Usher 701 kit - but I want to alter the
> cabinet dimensions (keeping the same
> internal volume) and I need to relocate the
> port to the front. Is this nuts? Will it
> compromise the design too much? The goal is
> to make a short floor-stander that's about
> 8" wide and no more than 30" high
> that can be located within 6" of the
> back wall.

Go ahead. The XO was (most likely) designed with a given baffle WIDTH in mind, and (if BSC was figured in there) a given distance out from the wall. If these are smaller to be used on stands (which I think they are), you'll notice some bass "bloom" when used back near a wall.

[jkim]

Provided Link: My Speaker Building Pages


> I want to use the drivers and crossover for
> the Usher 701 kit - but I want to alter the
> cabinet dimensions (keeping the same
> internal volume) and I need to relocate the
> port to the front. Is this nuts? Will it
> compromise the design too much? The goal is
> to make a short floor-stander that's about
> 8" wide and no more than 30" high
> that can be located within 6" of the
> back wall.

I think the default xover of the 701 kit may work fine in your situation (speakers close to back walls). Take a look at my analysis of the 701 kit:

<A HREF="http://www.geocities.com/woove99/Spkrbldg/Usher_701.htm">http://www.geocities.com/woove99/Spkrbldg/Usher_701.htm</A>

-jAy

[hhdinc]

Thanks for your response. I’m a woodworker and speaker builder, but definitely NOT a speaker designer. This client (in this case, my wife) needs a speaker built to match some previous work that I’ve done and the space is very limited. The goal is to get flat as possible response down into the 40hz range but in a tall, narrow package.

On the 701 what I need to do is narrow the width of the front baffle, decrease the depth, and make up for it by adding height. I also need to move the port to the front.

The internal dimensions that I’ve come up with are 25”h x 6.25”w x 8.5”d which is .77 ft3. By the time I add a couple of internal braces I should be pretty close to the .75 ft3 of the cabinet that comes with the kit. The max height on the speakers is 30”, so I could easily add more internal volume if anyone thinks that’s a good idea.

My next big question is where do I locate the port on the front baffle, and should I make any adjustments to the size of the port (diameter or length) given the new location?

A real bonus would be some kind of attenuation on the tweeter. I spend pretty much all day listening to a pair of ScanSpeak 2.5 ways that I built using the Revelator tweeter - I’m very spoiled. Almost every other tweeter that I listen to for any length of time begins to sound overly bright and harsh. The most recent pair of speakers I built for a friend used the Dayton RS28AS-4 which is a fine tweeter, but even it gets tiresome for me after 2 or 3 hours of listening.

Thanks to all

[panterra]

> A real bonus would be some kind of
> attenuation on the tweeter. I spend pretty
> much all day listening to a pair of
> ScanSpeak 2.5 ways that I built using the
> Revelator tweeter - I’m very spoiled. Almost
> every other tweeter that I listen to for any
> length of time begins to sound overly bright
> and harsh. The most recent pair of speakers
> I built for a friend used the Dayton
> RS28AS-4 which is a fine tweeter, but even
> it gets tiresome for me after 2 or 3 hours
> of listening.

> Thanks to all

I just finished a 2-way project using the Usher 8945P and the new Peerless HDS 810921 tweeter. You might consider that tweeter.

[jkim]

Provided Link: My Speaker Building Pages


> On the 701 what I need to do is narrow the
> width of the front baffle, decrease the
> depth, and make up for it by adding height.
> I also need to move the port to the front.

> The internal dimensions that I’ve come up
> with are 25”h x 6.25”w x 8.5”d which is .77
> ft3. By the time I add a couple of internal
> braces I should be pretty close to the .75
> ft3 of the cabinet that comes with the kit.
> The max height on the speakers is 30”, so I
> could easily add more internal volume if
> anyone thinks that’s a good idea.

.75 cu ft is a good volume for the 8945A.

> My next big question is where do I locate
> the port on the front baffle, and should I
> make any adjustments to the size of the port
> (diameter or length) given the new location?

You don't need to change the port size. As for the location of the port on the front baffle, some people like to place it close to the floor to use a stronger boundary gain. But there is no rule about this.

> A real bonus would be some kind of
> attenuation on the tweeter. I spend pretty
> much all day listening to a pair of
> ScanSpeak 2.5 ways that I built using the
> Revelator tweeter - I’m very spoiled. Almost
> every other tweeter that I listen to for any
> length of time begins to sound overly bright
> and harsh. The most recent pair of speakers
> I built for a friend used the Dayton
> RS28AS-4 which is a fine tweeter, but even
> it gets tiresome for me after 2 or 3 hours
> of listening.

I strongly believe that your preference of your SS tweeter is related to its unique frequency response, not due to its low distortion. These days, there are quite a few low distortion tweeters available to DIYers at reasonable prices. The RS28A is one of them. The Seas and the Usher tweeters have been popular. Recently, the Peerless HDS 810921 became popular, too. These are all very low distortion tweeters. But each has its own characteristics. For example, I used the Peerless tweeter, recommended in the above post, in my 2-way design, but spent a few months tuning it to finally get right sound. I found that a notch filter is needed to satisfy my taste. If you're interested, see

<A HREF="http://www.geocities.com/woove99/Spkrbldg/jays_blog.htm">http://www.geocities.com/woove99/Spkrbldg/jays_blog.htm</A>

It is interesting to see that other experienced people also reached the same tweaking with this tweeter:

<A HREF="http://www.htguide.com/forum/showthread.php4?t=28653">http://www.htguide.com/forum/showthread.php4?t=28653</A>

Take a look at post #11 and #14.

-jAy

[hhdinc]

Thank you for your insights. I spent some time looking at your designs. You obviously have a great deal of experience with these particular drivers. I'm going to go ahead and build the cabinets this weekend. Cabinet building is something I actually know something about. Wish me luck.