Does anyone know of a puplished frequency response (db)
curve... for the A7 800 ...
Does anyone know of a puplished frequency response (db)
curve... for the A7 800 ...
I don't know of any officially published response graph for the A7, though it's fairly straightforward to guesstimate one ( based on the type of crossover being used ) .
For the LF response , look in the LHF library ( Altec section > Specs > speaker Components > 515G > 3rd Page >Top Graph ) .
That graph shows the "stepped LF" response of the 515 ( 416 will be similar ) in the 828 enclosure ( used by the A7 ) .
HF response will depend on the horn & driver ( & crossover ) you are using .
One should count on bumping up the HF response above 9K with some sort of equalization .Panomaniac ( at the Hostboard forum ) has done the best job ( that I'm aware of ) at making the A7 ( or A5 ) into a HiFi performer .
PS ; Here's Pano's thread, My A7-500s. A journeyfor you to read through to ( hopefully ) gather some insights .
Thanks for ..info... Earl ...my A7's were empty when bought them..I put K140's 811/808's
and 20uf cap on the 808 and thats it!!! I'd like to trim them up w/30 band eq I have
got any suggestions as to how too....
<snip>.I put K140's 811/808's and 20uf cap on the 808 and thats it!!!
- I'd like to trim them up w/30 band eq I have,
- got any suggestions as to how too....
- No, sorry . I'm of the opinion that with the parts you currently have there on hand, you can't fix it by simply applying EQ ( you need a crossover ! ) .
- I believe you're best off buying ( or building ) a N1201-8a crossover network ( the same network used in the Altec M19 ) .
- Also, for HiFi use, I'd suggest that you buy a pair of GPA #34647 replacement diaphragms ( 8 ohm, all aluminum / as opposed to the 808 style symbiotic ) .
- The thread I linked you to is pretty detailed in what it takes to make PA-grade A7's morph into HiFi grade . Right now your A7s aren't even PA-grade ( since they lack a crossover ) .
- If you don't have the time, inclination or knowledge to follow through with that sort of journey, then I believe you're better off buying M19's ( & selling your A7 lash-ups ) .
Thanks again... Earl for ..good info.....I took your advice and eq'd the A7 800's above 9k
to +6-12db .... I used the 1218A Altec libr Graph as Ref...( I printed the graph and
pasted it under the eq and mimicked the whole graph above 1k......
Result....."New Experience" (muffled off) (Transparant on)
Conclusion: A7 needs eq (for hi fi)
Eqiup used ...Alesis 30b, laser trimmed, EQ (Xrtra quiet)
Reason: necessary to plot jagged curve of 1218A (w/811 horn)...
(only problem: 1218a uses 807 dr (not 808))
eq adj
My A7's run no crossover other then a 20uf cap. on the 808's
test: An elect. x-over and amp were added (left ch.) to ck eq settings..
Left/Right eq was kept same for listening ...and results were mixed
I wound up still at odds w/the overall tone of things....
I think my Real Problem is ...Room Eq...I have a Bad listening area
(don't we all) Standing waves and non-exisiting freq. got me
hunting for the old.. Radio Shack sound meter.... (If it still works)
more later.......
If your Adj. your bass and treble knobs for ea. song you play,
you probably need to (if you haven't already) Eq your room...
I never did it (even though I heard of it)....but I just happened up
on a 30 band eq....(even then I didn't know what to do with it!)
till I saw a You Tube 30b sp. test 1/3 Oct (it matched the freq's
on my Eq).....so out came the Radio Shack sound meter...I've
had a "work in progress" ever since....but ea. time I EQ, I get
a better result then "FLAT".....Dramatic would be more the word
for it.....It's great fun....I'd suggest anyone out there ..give it a go.
[]
This wild eq setting is the result of Zeroing my sound meter (accross the board)
to satisfy my room acoustics.. +10 db/ on one freq -10db on another That means
that before the EQ I was only hearing half the music.....
2ch: WiiM Pro; Topping E30 II DAC; Oppo, Acurus RL-11, Acurus A200, JBL Dynamics Project - Offline: L212-TwinStack, VonSchweikert VR-4
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Hi Knox;
You have just shown why RTA and or a sound meter will get you in trouble in small rooms in the lower frequency ranges and why steady tones are the least useful test stimulus for acoustical measurement.
Assuming an eight foot ceiling, in a room of your dimensions, the region where the acoustical performance of the space is mode dominated is bounded on the low end by the first mode of the Rooms Largest Dimension (RLD) is 20 Hz and the highest bounded by the Rooms Smallest Dimension (RSD) is about 425Hz. This is where RTA will lie to you, EQ can't help you, and absorption is really your only weapon. In this region, your ears are your best tool.
Theory says you have two hard hits about 20-23Hz, two more about 40-46Hz and a pile up at 60-70-80 and 93Hz. With EQ you can remove energy from the original signal in these bands in an attempt to not "aggravate the beast" but you obviously destroy the content fidelity. Tuned absorbers will bail you out of this.
I wouldn't worry too much about the hit in the 20's but the one in the 40's and the pileup between 60-90 could wreck the LF performance of an otherwise size of room most would be very glad to have.
In the end I would surely avoid an EQ routine anywhere near this aggresive. EQ is a great tool, used properly. Your EQ, of which I own two, is not the proper tool for precision acoustical space tuning, the filters are just too wide but it's fine as a relatively precise tone control.
To find the LF bounds of a space, use: f=.5C/RLD
To find the HF bounds of a space, use: f=3C/RSD
C= the speed of sound, use any metric you like thoughout the equation.
Hope this helps,
Barry.
If we knew what the hell we were doing, we wouldn't call it research would we.
I just saw the new Bond 007 flick in Dolby 7.1
and the sound was Spectacular, the Explosions
were so powerfull I thought a part of the building blew.
Being into EQ'g right now, I did notice, however, the Ultra high's
were just nonexistant.....Any thoughts?
A total lack of super tweeters I reckon.
If we knew what the hell we were doing, we wouldn't call it research would we.
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