I've seen some postings regarding foam stuffing at the corners of the high frequency horn in Model 19's. I have Valencia's and would like to try it. Can someone tell me what type of foam is used, and can I see a clear photo of what it looks like?
Many thanks.
Les
Stuffing the outer edges, or the cells on either end, just makes it a less than 90 drgree horn, and more directional.Originally Posted by les winter
Ron
http://www.hostboard.com/forums/alte...light=mod+foam
If you're refering to the foam inserts around the 811 horns....then see the thread "model-19-foam source"
Technically, it's foam damping, i.e. you're only interested in attenuating any reflections between the horn mouth and any surrounding cabinetry. 'Stuffing' would be placed inside the horn and as Ron noted can be used to change its directivity and frequency response which in either case will probably require a super tweeter horn to gain back the attenuated extreme HF response.
FWIW, I did some stuffing experimentation a long time ago, but couldn't find any foam that I found acceptable, but ~ recently I tried again with the 30 ppi open cell foam (fish tank filter) that Dr. Geddes uses in his consumer oriented waveguides (WG) and liked what I heard enough to never go back to an un-stuffed wide BW horn in a HIFI app.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
GM,
Can you elaborate a bit?
Ron
The Darst's email has changed since that post this past summer I received a pair from them and like'em very much new email is, I spoke to Debbie Darst Pauls wife.
Paul & Debbie Darst [email protected] this was their email as of July '09
Price has increased also I think $55 + shipping
Not much to elaborate on. I mean Dr.Geddes uses a custom cut foam plug that fills his WGs and then uses the XO combined with CD horn EQ to flatten its response out to 20 kHz, so efficiency is only around 93 dB IIRC, same as what an Altec sectoral horn is. The tonal difference though is that all the micro reflections (aka HOM's) that any horn, and especially compression loaded ones generate are attenuated enough to get lost in the horn's noise floor: Geddes on Waveguides - diyAudio
In principle, think vinyl or tape playback except without the HF noise (hiss), though of course somewhat more subtle, ergo more beneficial for those with youthful hearing, especially female ones. In the good ol' days all these noises were crudely dealt with using an appropriate density grill cloth and later, thick foam grills and of course the screen in a cinema.
Unfortunately, too much stuffing is required to completely attenuate a sectoral horn's 'honk' to alleviate the need for CD EQ, but I was zeroing in on a combination of different density foams that might work well enough when a passing cab's communication signal finally finished off my much abused diaphragms (the downside of hooking them up to a high power amp without proper protection), but with more pressing repairs there's no budget for new ones for awhile yet plus I want to get a test rig built/calibrated before posting anything definitive, so probably at least a year away.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Which horns did you give the foam treatment to, GM? 811?
511, I never have cared for the 811 unless a higher XO point than I prefer is used. Multi-cells would need a plug in each cell with the advantage that the inserts can be used to flatten its power response over a wider arc by increasing the density of the beaming center cells.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Posting Permissions
Bookmarks